Encyclopedia of Computer Science and Technology

Encyclopedia ofComputer scienceand technologyRevised Editionharry henderson

In memory of my brother,Bruce Henderson,who gave me my first opportunity to explorepersonal computing almost 30 years ago.ENCYCLOPEDIA OF COMPUTER SCIENCE and TECHNOLOGY, Revised EditionCopyright © 2009, 2004, 2003 by Harry HendersonAll rights reserved. No part of this book may be reproduced or utilized in any form or byany means, electronic or mechanical, including photocopying, recording, or by anyinformation storage or retrieval systems, without permission in writing from the publisher.For information contact:Facts On File, Inc.An imprint of Infobase Publishing132 West 31st StreetNew York NY 10001Library of Congress Cataloging-in-Publication DataHenderson, Harry, 1951–Encyclopedia of computer science and technology / Harry Henderson.—Rev. ed.p. cm.Includes bibliographical references and index.ISBN-13: 978-0-8160-6382-6ISBN-10: 0-8160-6382-61. Computer science—Encyclopedias. 2. Computers—Encyclopedias. I. Title.QA76.15.H43 2008004.03—dc22 2008029156Facts On File books are available at special discounts when purchased in bulk quantitiesfor businesses, associations, institutions, or sales promotions. Please call our Special SalesDepartment in New York at (212) 967-8800 or (800) 322-8755.You can find Facts On File on the World Wide Web at http://www.factsonfile.comText design by Erika K. ArroyoCover design by Salvatore Luongolllustrations by Sholto AinsliePhoto research by Tobi Zausner, Ph.D.Printed in the United States of AmericaVB Hermitage 10 9 8 7 6 5 4 3 2 1This book is printed on acid-free paper and contains30 percent postconsumer recycled content.

C on t e n t sAcknowledgmentsivintroduction to the Revised EditionvA–Z Entries1Appendix IBibliographies and Web Resources527Appendix IIA Chronology of Computing529Appendix IIISome Significant Awards542Appendix IVComputer-Related Organizations553Index555

A c k no w l e d g m e n t swish to acknowledge with gratitude the patient and thoroughI management of this project by my editor, Frank K. Darmstadt. I canscarcely count the times he has given me encouragement and nudgesas needed. I also wish to thank Tobi Zausner, Ph.D., for her ability andefficiency in obtaining many of the photos for this book.iv

I n t r od u c t ion to t h eR e v i s e d E d i t ionChances are that you use at least one computer or computer-relateddevice on a daily basis. Some are obvious:for example, the personal computer on your desk or atyour school, the laptop, the PDA that may be in your briefcase.Other devices may be a bit less obvious: the “smart”cell phone, the iPod, a digital camera, and other essentiallyspecialized computers, communications systems, and datastorage systems. Finally, there are the “hidden” computersfound in so many of today’s consumer products—such asthe ones that provide stability control, braking assistance,and navigation in newer cars.Computers not only seem to be everywhere, but alsoare part of so many activities of daily life. They bringtogether willing sellers and buyers on eBay, allow youto buy a book with a click on the Amazon.com Web site,and of course put a vast library of information (of varyingquality) at your fingertips via the World Wide Web.Behind the scenes, inventory and payroll systems keepbusinesses running, track shipments, and more problematically,keep track of where people go and what theybuy. Indeed, the infrastructure of modern society, fromwater treatment plants to power grids to air-traffic control,depends on complex software and systems.Modern science would be inconceivable without computersto gather data and run models and simulations.Whether bringing back pictures of the surface of Mars ordetailed images to guide brain surgeons, computers havegreatly extended our knowledge of the world around us andour ability to turn ideas into engineering reality.The revised edition of the Facts On File Encyclopedia ofComputer Science and Technology provides overviews andimportant facts about these and dozens of other applicationsof computer technology. There are also many entriesdealing with the fundamental concepts underlying computerdesign and programming, the Internet, and othertopics such as the economic and social impacts of the informationsociety.The book’s philosophy is that because computer technologyis now inextricably woven into our everyday lives,anyone seeking to understand its impact must not onlyknow how the bits flow, but also how the industry worksand where it may be going in the years to come.New and Enhanced CoverageThe need for a revised edition of this encyclopedia becomesclear when one considers the new products, technologies,and issues that have appeared in just a few years. (Considerthat at the start of the 2000 decade, Ajax was still only acleaning product and blog was not even a word.)The revised edition includes almost 180 new entries,including new programming languages (such as C# andRuby), software development and Web design technologies(such as the aforementioned Ajax, and Web services), andexpanded coverage of Linux and other open-source software.There are also entries for key companies in software,hardware, and Web commerce and services.Many other new entries reflect new ways of using informationtechnology and important social issues that arisefrom such use, including the following:• blogging and newer forms of online communicationthat are influencing journalism and political campaigns• other ways for users to create and share content, suchas file-sharing networks and YouTube• new ways to share and access information, such asthe popular Wikipedia• the ongoing debate over who should pay for Internetaccess, and whether service providers or governmentsshould be able to control the Web’s content• the impact of surveillance and data mining on privacyand civil liberties

viIntroduction to the Revised Editionas• threats to data security, ranging from identity thievesand “phishers” to stalkers and potential “cyberterrorists”• the benefits and risks of social networking sites (suchas MySpace)• the impact of new technology on women and minorities,young people, the disabled, and other groupsOther entries feature new or emerging technology, such• portable media devices (the iPod and its coming successors)• home media centers and the gradual coming of thelong-promised “smart house”• navigation and mapping systems (and their integrationwith e-commerce)• how computers are changing the way cars, appliances,and even telephones work• “Web 2.0”—and beyondFinally, we look at the farther reaches of the imagination,considering such topics as• nanotechnology• quantum computing• science fiction and computing• philosophical and spiritual aspects of computing• the ultimate “technological singularity”In addition to the many new entries, all existing entrieshave been carefully reviewed and updated to include thelatest facts and trends.Getting the Most Out of This BookThis encyclopedia can be used in several ways: for example,you can look up specific entries by referring from topics inthe index, or simply by browsing. The nearly 600 entriesin this book are intended to read like “mini-essays,” givingnot just the bare definition of a topic, but also developing itssignificance for the use of computers and its relationship toother topics. Related topics are indicated by small capitalletters. At the end of each entry is a list of books, articles,and/or Web sites for further exploration of the topic.Every effort has been made to make the writing accessibleto a wide range of readers: high school and collegestudents, computer science students, working computerprofessionals, and adults who wish to be better informedabout computer-related topics and issues.The appendices provide further information for referenceand exploration. They include a chronology of significantevents in computing; a listing of achievements incomputing as recognized in major awards; an additionalbibliography to supplement that given with the entries;and finally, brief descriptions and contact information forsome important organizations in the computer field.This book can also be useful to obtain an overview ofparticular areas in computing by reading groups of relatedentries. The following listing groups the entries by category.AI and Roboticsartificial intelligenceartificial lifeBayesian analysisBreazeal, CynthiaBrooks, Rodneycellular automatachess and computerscognitive sciencecomputer visionDreyfus, Hubert L.Engelberger, Josephexpert systemsFeigenbaum, Edwardfuzzy logicgenetic algorithmshandwriting recognitioniRobot Corporationknowledge representationKurzweil, Raymond C.Lanier, JaronMaes, PattieMcCarthy, JohnMinsky, Marvin LeeMIT Media Labnatural language processingneural interfacesneural networkPapert, Seymourpattern recognitionroboticssingularity, technologicalsoftware agentspeech recognition and synthesistelepresenceWeizenbaum, JosephBusiness and E-Commerce ApplicationsAmazon.comAmerica Online (AOL)application service provider (ASP)application softwareapplication suiteauctions, onlineauditing in data processingbanking and computersBezos, Jeffrey P.Brin, Sergeybusiness applications of computersCraigslistcustomer relationship management (CRM)decision support systemdesktop publishing (DTP)

Introduction to the Revised Editionviienterprise computingGooglegroupwarehome officemanagement information system (MIS)middlewareoffice automationOmidyar, Pierreonline advertisingonline investingonline job searching and recruitingoptical character recognition (OCR)Page, LarryPDF (Portable Document Format)personal health information managementpersonal information manager (PIM)presentation softwareproject management softwaresmart cardspreadsheetsupply chain managementsystems analysttelecommutingtext editortransaction processingtrust and reputation systemsword processingYahoo!Computer Architectureaddressingarithmetic logic unit (ALU)bits and bytesbufferingbuscachecomputer engineeringconcurrent programmingcooperative processingCray, Seymourdevice driverdistributed computingembedded systemgrid computingparallel portreduced instruction set computer (RISC)serial portsupercomputerUSB (Universal Serial Bus)Computer IndustryAdobe SystemsAdvanced Micro Devices (AMD)Amdahl, Gene MyronApple CorporationBell, C. GordonBell Laboratoriesbenchmarkcertification of computer professionalsCisco Systemscompatibility and portabilitycomputer industryDell, Inc.education in the computer fieldemployment in the computer fieldentrepreneurs in computingGates, William III (Bill)Grove, AndrewIBMIntel Corporationjournalism and the computer industrymarketing of softwareMicrosoft CorporationMoore, Gordon E.Motorola Corporationresearch laboratories in computingstandards in computingSun MicrosystemsWozniak, StevenComputer Science FundamentalsChurch, Alonzocomputer sciencecomputability and complexitycyberneticshexadecimal systeminformation theorymathematics of computingmeasurement units used in computingTuring, Alan Mathisonvon Neumann, JohnWiener, NorbertComputer Security and Risksauthenticationbackup and archive systemsbiometricscomputer crime and securitycomputer forensicscomputer viruscopy protectioncounterterrorism and computerscyberstalking and harassmentcyberterrorismDiffie, Bailey Whitfielddisaster planning and recoveryencryptionfault tolerancefirewallhackers and hackingidentity theftinformation warfareMitnick, Kevin D.online frauds and scamsphishing and spoofingRFID (radio frequency identification)

viiiIntroduction to the Revised Editionrisks of computingSpafford, Eugene H.spamspyware and adwareY2K ProblemDatabasesCORBA (Common Object Request Broker Architecture)data conversiondata dictionarydata miningdata securitydata warehousedatabase administrationdatabase management system (DBMS)databasehashinginformation retrievalOracle CorporationSAPSOAP (Simple Object Access Protocol)SQLData Communications and Networking(General)bandwidthBluetoothbroadbandcable modemclient-server computingdata acquisitiondata communicationsdata compressionDSL (digital subscriber line)error correctionfiber opticsfile serverfile transfer protocolsFireWirelocal area network (LAN)modemnetworksatellite Internet serviceShannon, Claude Esynchronous/asynchronous operationtelecommunicationsterminalWifiwireless computingData Types and Algorithmsalgorithmarraybindingbitwise operationsBoolean operatorsbranching statementscharacters and stringsclassconstants and literalsdatadata abstractiondata structuresdata typesenumerations and setsheap (data structure)Knuth, Donaldlist processingnumeric dataoperators and expressionssorting and searchingstacktreevariableDevelopment of ComputersAiken, Howardanalog and digitalanalog computerAtanasoff, John VincentBabbage, CharlescalculatorEckert, J. Presperhistory of computingHollerith, HermannMauchly, John WilliammainframeminicomputerZuse, KonradFuture ComputingbioinformationDertouzos, MichaelJoy, Billmolecular computingnanotechnologyquantum computingtrends and emerging technologiesubiquitous computingGames, Graphics, and Mediaanimation, computerart and the computerbitmapped imagecodeccolor in computingcomputer gamescomputer graphicsdigital rights management (DRM)DVR (digital video recording)Electronic Artsfilm industry and computingfontfractals in computinggame consolesgraphics card

Introduction to the Revised Editionixgraphics formatsgraphics tabletimage processingmedia center, homemultimediamusic and video distribution, onlinemusic and video players, digitalmusic, computeronline gamblingonline gamesphotography, digitalpodcastingPostScriptRSS (real simple syndication)RTF (Rich Text Format)sound file formatsstreaming (video or audio)Sutherland, Ivan Edwardvideo editing, digitalYouTubeHardware ComponentsCD-ROM and DVD-ROMflash driveflat-panel displayfloppy diskhard diskkeyboardmonitormotherboardnetworked storageoptical computingprinterspunched cards and paper tapeRAID (redundant array of inexpensive disks)scannertape drivesInternet and World Wide Webactive server pages (ASP)Ajax (Asynchronous JavaScript and XML)Andreessen, MarcBerners-Lee, Timblogs and bloggingbulletin board systems (BBS)Bush, Vannevarcascading style sheets (CSS)Cerf, Vinton G.certificate, digitalCGI (common gateway interface)chat, onlinechatterbotsconferencing systemscontent managementcookiesCunningham, Howard (Ward)cyberspace and cyber culturedigital cash (e-commerce)digital convergencedomain name system (DNS)eBaye-books and digital librariese-commercee-mailfile-sharing and P2P networksflash and smart mobHTML, DHTML, and XHTMLhypertext and hypermediaInternetInternet applications programmingInternet cafes and “hot spots”Internet organization and governanceInternet radioInternet service provider (ISP)Kleinrock, LeonardLicklider, J. C. R.mashupsNetiquettenetnews and newsgroupsonline researchonline servicesportalRheingold, Howardsearch enginesemantic Websocial networkingTCP/IPtexting and instant messaginguser-created contentvideoconferencingvirtual communityWales, JimmyWeb 2.0 and beyondWeb browserWeb camWeb filterWebmasterWeb page designWeb serverWeb serviceswikis and WikipediaWorld Wide WebxmLOperating Systemsdemonemulationfileinput/output (I/O)job control languagekernelLinuxmemorymemory managementmessage passingmicrosoft windowsMS-DOSmultiprocessing

Introduction to the Revised Editionmultitaskingoperating systemOS Xsystem administratorregular expressionRitchie, DennisshellStallman, RichardTorvalds, LinusUNIXOther Applicationsbioinformaticscars and computingcomputer-aided design and manufacturing (CAD/CAM)computer-aided instruction (CAI)distance educationeducation and computersfinancial softwaregeographical information systems (GIS)journalism and computerslanguage translation softwarelaw enforcement and computerslegal softwarelibraries and computinglinguistics and computingmap information and navigation systemsmathematics softwaremedical applications of computersmilitary applications of computersscientific computing applicationssmart buildings and homessocial sciences and computingspace exploration and computersstatistics and computingtypography, computerizedworkstationPersonal Computer ComponentsBIOS (Basic Input-Output System)boot sequencechipchipsetclock speedCPU (central processing unit)green PCIBM PClaptop computermicroprocessorpersonal computer (PC)PDA (personal digital assistant)plug and playsmartphonetablet PCProgram Language Conceptsauthoring systemsautomatic programmingassemblerBackus-Naur Form (BNF)compilerencapsulationfinite state machineflagfunctional languagesinterpreterloopmodeling languagesnonprocedural languagesontologies and data modelsoperators and expressionsparsingpointers and indirectionprocedures and functionsprogramming languagesqueuerandom number generationreal-time processingrecursionscheduling and prioritizationscripting languagesStroustrup, BjarnetemplateWirth, NiklausProgramming LanguagesAdaAlgolAPLawkBASICCC#C++CobolEiffelForthFORTRANJavaJavaScriptLISPLOGOLuaPascalPerlPHPPL/1PrologPythonRPGRubySimulaTclSmalltalkVBScriptSocial, Political, and Legal Issuesanonymity and the Internetcensorship and the Internet

Introduction to the Revised Editionxicomputer literacycyberlawdeveloping nations and computingdigital dividedisabled persons and computinge-governmentelectronic voting systemsglobalization and the computer industrygovernment funding of computer researchidentity in the online worldintellectual property and computingLessig, Lawerencenet neutralityphilosophical and spiritual aspects of computingpolitical activism and the Internetpopular culture and computingprivacy in the digital agescience fiction and computingsenior citizens and computingservice-oriented architecture (SOA)social impact of computingStoll, Cliffordtechnology policywomen and minorities in computingyoung people and computingSoftware Development and Engineeringappletapplication program interface (API)bugs and debuggingCASE (computer-aided software engineering)design patternsDijkstra, Edsgerdocumentation of program codedocumentation, userdocument modelDOM (document Object Model)error handlingflowchartHopper, Grace Murrayinformation designinternationalization and localizationlibrary, programmacroMicrosoft .NETobject-oriented programming (OOP)open source movementplug-inprogramming as a professionprogramming environmentpseudocodequality assurance, softwarereverse engineeringsharewareSimonyi, Charlessimulationsoftware engineeringstructured programmingsystems programmingvirtualizationUser Interface and Supportdigital dashboardEngelbart, Dougergonomics of computinghaptic interfacehelp systemsinstallation of softwareJobs, Steven PaulKay, AlanMacintoshmouseNegroponte, Nicholaspsychology of computingtechnical supporttechnical writingtouchscreenTurkle, Sherryser groupsuser interfacevirtual realitywearable computers

Aabstract data type See data abstraction.active server pages (ASP)Many users think of Web pages as being like pages ina book, stored intact on the server, ready to be flippedthrough with the mouse. Increasingly, however, Web pagesare dynamic—they do not actually exist until the userrequests them, and their content is determined largely bywhat the user requests. This demand for greater interactivityand customization of Web content tends to fall first onthe server (see client-server computing and Web server)and on “server side” programs to provide such functions asdatabase access. One major platform for developing Webservices is Microsoft’s Active Server Pages (ASP).In ASP programmers work with built-in objects that representbasic Web page functions. The RecordSet object canprovide access to a variety of databases; the Response objectcan be invoked to display text in response to a user action;and the Session object provides variables that can be usedto store information about previous user actions such asadding items to a shopping cart (see also cookies).Control of the behavior of the objects within the Webpage and session was originally handled by code writtenin a scripting language such as VBScript and embeddedwithin the HTML text (see html and VBScript). However,ASP .NET, based on Microsoft’s latest Windowsclass libraries (see Microsoft .net) and introduced in2002, allows Web services to be written in full-fledgedprogramming languages such as Visual Basic .NET andC#, although in-page scripting can still be used. This canprovide several advantages: access to software developmenttools and methodologies available for establishedprogramming languages, better separation of programcode from the “presentational” (formatting) elements ofHTML, and the speed and security associated with compiledcode. ASP .NET also emphasizes the increasinglyprevalent Extensible Markup Language (see xml) for organizingdata and sending those data between objects usingSimple Object Access Protocol (see soap).Although ASP .NET was designed to be used withMicrosoft’s Internet Information Server (IIS) under Windows,the open-source Mono project (sponsored by Novell)implements a growing subset of the .NET classes for use onUNIX and Linux platforms using a C# compiler with appropriateuser interface, graphics, and database libraries.An alternative (or complementary) approach that hasbecome popular in recent years reduces the load on theWeb server by avoiding having to resend an entire Webpage when only a small part actually needs to be changed.See Ajax (asynchronous JavaScript and XML).Further ReadingBellinaso, Marco. ASP .NET 2.0 Website Programming: Problem—Design—Solution. Indianapolis: Wiley Publishing, 2006.Liberty, Jesse, and Dan Hurwitz. Programming ASP .NET. 3rd ed.Sebastapol, Calif.: O’Reilly, 2005.McClure, Wallace B., et al. Beginning Ajax with ASP .NET. Indianapolis:Wiley Publishing, 2006.Mono Project. Available online. URL: http://www.mono-project.com/Main_Page. Accessed April 10, 2007.

AdaAdaStarting in the 1960s, the U.S. Department of Defense(DOD) began to confront the growing unmanageability ofits software development efforts. Whenever a new applicationsuch as a communications controller (see embeddedsystem) was developed, it typically had its own specializedprogramming language. With more than 2,000 suchlanguages in use, it had become increasingly costly anddifficult to maintain and upgrade such a wide variety ofincompatible systems. In 1977, a DOD working group beganto formally solicit proposals for a new general-purpose programminglanguage that could be used for all applicationsranging from weapons control and guidance systems to barcodescanners for inventory management. The winning languageproposal eventually became known as Ada, namedfor 19th-century computer pioneer Ada Lovelace see alsoBabbage, Charles). After a series of reviews and revisionsof specifications, the American National Standards Instituteofficially standardized Ada in 1983, and this first version ofthe language is sometimes called Ada-83.Language FeaturesIn designing Ada, the developers adopted basic languageelements based on emerging principles (see structuredprogramming) that had been implemented in languagesdeveloped during the 1960s and 1970s (see Algol andPascal). These elements include well-defined controlstructures (see branching statements and loop) andthe avoidance of the haphazard jump or “goto” directive.Ada combines standard structured language features(including control structures and the use of subprograms)with user-definable data type “packages” similar to theclasses used later in C++ and other languages (see classand object-oriented programming). As shown in thissimple example, an Ada program has a general form similarto that used in Pascal. (Note that words in boldface type arelanguage keywords.)with Ada.Text_IO; use Ada.Text_IO;procedure Get_Name isName : String (1..80);Length : Integer;beginPut (“What is your first name?”);Get_Line (Name, Length);New_Line;Put (“Nice to meet you,”);Put (Name (1..Length));end Get_Name;The first line of the program specifies what “packages”will be used. Packages are structures that combine datatypes and associated functions, such as those needed forgetting and displaying text. The Ada.Text.IO package, forexample, has a specification that includes the following:package Text_IO istype File_Type is limited private;type File_Mode is (In_File, Out_File, Append_File);procedure Create (File : in out File_Type;Mode : in File_Mode := Out_File;Name : in String := “”);procedure Close (File : in out File_Type);procedure Put_Line (File : in File_Type;Item : in String);procedure Put_Line (Item : in String);end Text_IO;The package specification begins by setting up a datatype for files, and then defines functions for creating andclosing a file and for putting text in files. As with C++classes, more specialized packages can be derived frommore general ones.In the main program Begin starts the actual data processing,which in this case involves displaying a messageusing the Put function from the Ada.Text.IO function andgetting the user response with Get_Line, then using Putagain to display the text just entered.Ada is particularly well suited to large, complex softwareprojects because the use of packages hides and protects thedetails of implementing and working with a data type. Aprogrammer whose program uses a package is restricted tousing the visible interface, which specifies what parametersare to be used with each function. Ada compilers are carefullyvalidated to ensure that they meet the exact specificationsfor the processing of various types of data (see datatypes), and the language is “strongly typed,” meaning thattypes must be explicitly declared, unlike the case with C,where subtle bugs can be introduced when types are automaticallyconverted to make them compatible.Because of its application to embedded systems and realtimeoperations, Ada includes a number of features designedto create efficient object (machine) code, and the languagealso makes provision for easy incorporation of routines writtenin assembly or other high-level languages. The latest officialversion, Ada 95, also emphasizes support for parallelprogramming (see multiprocessing). The future of Ada isunclear, however, because the Department of Defense no longerrequires use of the language in government contracts.Ada development has continued, particularly in areasincluding expanded object-oriented features (includingsupport for interfaces with multiple inheritance); improvedhandling of strings, other data types, and files; and refinementsin real-time processing and numeric processing.Further Reading“Ada 95 Lovelace Tutorial.” Available online. URL: http://www.adahome.com/Tutorials/Lovelace/lovelace.htm. Accessed April18, 2008.Ada 95 On-line Reference Manual (hypertext) Available online.URL: http://www.adahome.com/Resources/refs/rm95.html.Accessed April 18, 2008.Barnes, John. Programming in Ada 2005 with CD. New York: PearsonEducation, 2006.Dale, Nell, and John W. McCormick. Ada Plus Data Structures: AnObject-Oriented Approach. 2nd ed. Sudbury, Mass.: Jones andBartlett, 2006.

Adobe SystemsaddressingIn order for computers to manipulate data, they must beable to store and retrieve it on demand. This requires a wayto specify the location and extent of a data item in memory.These locations are represented by sequential numbers, oraddresses.Physically, a modern RAM (random access memory)can be visualized as a grid of address lines that crisscrosswith data lines. Each line carries one bit of the address,and together, they specify a particular location in memory(see memory). Thus a machine with 32 address lines canhandle up to 32 bits, or 4 gigabytes (billions of bytes) worthof addresses. However the amount of memory that can beaddressed can be extended through indirect addressing,where the data stored at an address is itself the address ofanother location where the actual data can be found. Thisallows a limited amount of fast memory to be used to pointto data stored in auxiliary memory or mass storage thusextending addressing to the space on a hard disk drive.Some of the data stored in memory contains the actualprogram instructions to be executed. As the processorexecutes program instructions, an instruction pointeraccesses the location of the next instruction. An instructioncan also specify that if a certain condition is met theprocessor will jump over intervening locations to fetchthe next instruction. This implements such control structuresas branching statements and loops.Addressing in ProgramsA variable name in a program language actually referencesan address (or often, a range of successive addresses, sincemost data items require more than one byte of storage). Forexample, if a program includes the declarationInt Old_Total, New_Total;when the program is compiled, storage for the variablesOld_Total and New_Total is set aside at the next availableaddresses. A statement such asNew_Total = 0;is compiled as an instruction to store the value 0 in theaddress represented by New_Total. When the program laterperforms a calculation such as:New_Total = Old_Total + 1;the data is retrieved from the memory location designatedby Old_Total and stored in a register in the CPU, where 1 isadded to it, and the result is stored in the memory locationdesignated by New_Total.Although programmers don’t have to work directly withaddress locations, programs can also use a special type ofvariable to hold and manipulate memory addresses for moreefficient access to data (see pointers and indirection).Further Reading“Computer Architecture Tutorial.” Available online. URL: http://www.cs.iastate.edu/~prabhu/Tutorial/title.html. Accessed April10, 2007.Murdocca, Miles J., and Vincent P. Heuring. Principles of ComputerArchitecture. Upper Saddle River, N.J.: Prentice Hall, 2000.Virtual memory uses indirect addressing. When a program requestsdata from memory, the address is looked up in a table that keepstrack of each block’s actual location. If the block is not in RAM, oneor more blocks in RAM are copied to the swap file on disk, and theneeded blocks are copied from disk into the vacated area in RAM.Adobe SystemsAdobe Systems (NASDAQ symbol ADBE) is best known forproducts relating to the formatting, printing, and display ofdocuments. Founded in 1982 by John Warnock and CharlesGeschke, the company is named for a creek near one of theirhomes.Adobe’s first major product was a language that describesthe font sizes, styles, and other formatting needed to printpages in near-typeset quality (see PostScript). This was asignificant contribution to the development of software fordocument creation (see desktop publishing), particularly onthe Apple Macintosh, starting in the later 1980s. Building onthis foundation, Adobe developed high-quality digital fonts(called Type 1). However, Apple’s TrueType fonts proved tobe superior in scaling to different sizes and in the precisecontrol over the pixels used to display them. With the licensingof TrueType to Microsoft for use in Windows, TrueTypefonts took over the desktop, although Adobe Type 1 remainedpopular in commercial typesetting applications. Finally, inthe late 1990s Adobe, together with Microsoft, established anew font format called OpenType, and by 2003 Adobe hadconverted all of its Type 1 fonts to the new format.Adobe’s Portable Document Format (see pdf) has becomea ubiquitous standard for displaying print documents. Adobegreatly contributed to this development by making a freeAdobe Acrobat PDF reader available for download.

Advanced Micro Devices (AMD)Image Processing SoftwareIn the mid-1980s Adobe’s founders realized that they couldfurther exploit the knowledge of graphics rendition that theyhad gained in developing their fonts. They began to createsoftware that would make these capabilities available to illustratorsand artists as well as desktop publishers. Their firstsuch product was Adobe Illustrator for the Macintosh, a vector-baseddrawing program that built upon the graphics capabilitiesof their PostScript language.In 1989 Adobe introduced Adobe Photoshop for theMacintosh. With its tremendous variety of features, theprogram soon became a standard tool for graphic artists.However, Adobe seemed to have difficulty at first in anticipatingthe growth of desktop publishing and graphic artson the Microsoft Windows platform. Much of that marketwas seized by competitors such as Aldus PageMaker andQuarkXPress. By the mid-1990s, however, Adobe, fueled bythe continuing revenue from its PostScript technology, hadacquired both Aldus and Frame Technologies, maker of thepopular FrameMaker document design program. MeanwhilePhotoShop continued to develop on both the Macintosh andWindows platforms, aided by its ability to accept add-onsfrom hundreds of third-party developers (see plug-ins).Multimedia and the WebAdobe made a significant expansion beyond document processinginto multimedia with its acquisition of Macromedia(with its popular Flash animation software) in 2005 at a costof about $3.4 billion. The company has integrated Macromedia’sFlash and Dreamweaver Web-design software into itsCreative Suite 3 (CS3). Another recent Adobe product thattargets Web-based publishing is Digital Editions, which integratedthe existing Dreamweaver and Flash software into apowerful but easy-to-use tool for delivering text content andmultimedia to Web browsers. Buoyed by these developments,Adobe earned nearly $2 billion in revenue in 2005, about$2.5 billion in 2006, and $3.16 billion in 2007.Today Adobe has over 6,600 employees, with its headquartersin San Jose and offices in Seattle and San Franciscoas well as Bangalore, India; Ottawa, Canada; and other locations.In recent years the company has been regarded as asuperior place to work, being ranked by Fortune magazineas the fifth best in America in 2003 and sixth best in 2004.Further Reading“Adobe Advances on Stronger Profit.” Business Week Online, December18, 2006. Available online. URL: http://www.businessweek.com/investor/content/dec2006/pi20061215_986588.htm. Accessed April 10, 2007.Adobe Systems Incorporated home page. Available online. URL:http://www.adobe.com. Accessed April 10, 2007.“Happy Birthday Acrobat: Adobe’s Acrobat Turns 10 Years Old.”Print Media 18 (July–August 2003): 21.Advanced Micro Devices (AMD)Sunnyvale, California-based Advanced Micro Devices, Inc.,(NYSE symbol AMD) is a major competitor in the marketfor integrated circuits, particularly the processors that areat the heart of today’s desktop and laptop computers (seemicroprocessor). The company was founded in 1969 by agroup of executives who had left Fairchild Semiconductor.In 1975 the company began to produce both RAM (memory)chips and a clone of the Intel 8080 microprocessor.When IBM adopted the Intel 8080 for its first personalcomputer in 1982 (see Intel Corporation and IBM PC),it required that there be a second source for the chip. Inteltherefore signed an agreement with AMD to allow the latterto manufacture the Intel 9806 and 8088 processors. AMDalso produced the 80286, the second generation of PC-compatibleprocessors, but when Intel developed the 80386 itcanceled the agreement with AMD.A lengthy legal dispute ensued, with the CaliforniaSupreme Court finally siding with AMD in 1991. However,as disputes continued over the use by AMD of “microcode”(internal programming) from Intel chips, AMD eventuallyused a “clean room” process to independently create functionallyequivalent code (see reverse engineering). However,the speed with which new generations of chips wasbeing produced rendered this approach impracticable bythe mid-1980s, and Intel and AMD concluded a (largelysecret) agreement allowing AMD to use Intel code and providingfor cross-licensing of patents.In the early and mid-1990s AMD had trouble keeping upwith Intel’s new Pentium line, but the AMD K6 (introducedin 1997) was widely viewed as a superior implementation ofthe microcode in the Intel Pentium—and it was “pin compatible,”making it easy for manufacturers to include it ontheir motherboards.Today AMD remains second in market share to Intel.AMD’s Athlon, Opteron, Turion, and Sempron processorsare comparable to corresponding Intel Pentium processors,and the two companies compete fiercely as each introducesnew architectural features to provide greater speed or processingcapacity.In the early 2000s AMD seized the opportunity to beatIntel to market with chips that could double the data bandwidthfrom 32 bits to 64 bits. The new specification standard,called AMD64, was adopted for upcoming operatingsystems by Microsoft, Sun Microsystems, and the developersof Linux and UNIX kernels. AMD has also matchedIntel in the latest generation of dual-core chips that essentiallyprovide two processors on one chip. Meanwhile,AMD strengthened its position in the high-end server marketwhen, in May 2006, Dell Computer announced that itwould market servers containing AMD Opteron processors.In 2006 AMD also moved into the graphics-processing fieldby merging with ATI, a leading maker of video cards, ata cost of $5.4 billion. Meanwhile AMD also continues tobe a leading maker of flash memory, closely collaboratingwith Japan’s Fujitsu Corporation (see flash drive). In2008 AMD continued its aggressive pursuit of market share,announcing a variety of products, including a quad-coreOpteron chip that it expects to catch up to if not surpasssimilar chips from Intel.

AjaxFurther ReadingAMD Web site. Available online. URL: http://www.amd.com/usen/.Accessed April 10, 2007.Rodengen, Jeffrey L. The Spirit of AMD: Advanced Micro Devices. Ft.Lauderdale, Fla.: Write Stuff Enterprises, 1998.Tom’s Hardware [CPU articles and charts]. Available online. URL:http://www.tomshardware.com/find_by_topic/cpu.html.Accessed April 10, 2007.advertising, online See online advertising.agent software See software agent.AI See artificial intelligence.Aiken, Howard(1900–1973)AmericanElectrical EngineerHoward Hathaway Aiken was a pioneer in the developmentof automatic calculating machines. Born on March 8, 1900,in Hoboken, New Jersey, he grew up in Indianapolis, Indiana,where he pursued his interest in electrical engineeringby working at a utility company while in high school. Heearned a B.A. in electrical engineering in 1923 at the Universityof Wisconsin.By 1935, Aiken was involved in theoretical work onelectrical conduction that required laborious calculation.Inspired by work a hundred years earlier (see Babbage,Charles), Aiken began to investigate the possibility of buildinga large-scale, programmable, automatic computing device(see calculator). As a doctoral student at Harvard, Aikenaroused interest in his project, particularly from ThomasWatson, Sr., head of International Business Machines (IBM).In 1939, IBM agreed to underwrite the building of Aiken’sfirst calculator, the Automatic Sequence Controlled Calculator,which became known as the Harvard Mark I.Mark I and Its ProgenyLike Babbage, Aiken aimed for a general-purpose programmablemachine rather than an assembly of special-purposearithmetic units. Unlike Babbage, Aiken had accessto a variety of tested, reliable components, including cardpunches, readers, and electric typewriters from IBM andthe mechanical electromagnetic relays used for automaticswitching in the telephone industry. His machine used decimalnumbers (23 digits and a sign) rather than the binarynumbers of the majority of later computers. Sixty registersheld whatever constant data numbers were needed to solvea particular problem. The operator turned a rotary dial toenter each digit of each number. Variable data and programinstructions were entered via punched paper tape. Calculationshad to be broken down into specific instructions similarto those in later low-level programming languages suchas “store this number in this register” or “add this numberto the number in that register” (see assembler). The results(usually tables of mathematical function values) could beprinted by an electric typewriter or output on punchedcards. Huge (about 8 feet [2.4 m] high by 51 feet [15.5 m]long), slow, but reliable, the Mark I worked on a varietyof problems during World War II, ranging from equationsused in lens design and radar to the designing of the implosivecore of an atomic bomb.Aiken completed an improved model, the Mark II, in1947. The Mark III of 1950 and Mark IV of 1952, however,were electronic rather than electromechanical, replacingrelays with vacuum tubes.Compared to later computers such as the ENIAC andUNIVAC, the sequential calculator, as its name suggests,could only perform operations in the order specified. Anylooping had to be done by physically creating a repetitivetape of instructions. (After all, the program as a whole wasnot stored in any sort of memory, and so previous instructionscould not be reaccessed.) Although Aiken’s machinessoon slipped out of the mainstream of computer development,they did include the modern feature of parallel processing,because different calculation units could work ondifferent instructions at the same time. Further, Aiken recognizedthe value of maintaining a library of frequentlyneeded routines that could be reused in new programs—another fundamental of modern software engineering.Aiken’s work demonstrated the value of large-scale automaticcomputation and the use of reliable, available technology.Computer pioneers from around the world came toAiken’s Harvard computation lab to debate many issues thatwould become staples of the new discipline of computerscience. The recipient of many awards including the EdisonMedal of the IEEE and the Franklin Institute’s John PriceAward, Howard Aiken died on March 14, 1973, in St. Louis,Missouri.Further ReadingCohen, I. B. Howard Aiken: Portrait of a Computer Pioneer. Cambridge,Mass.: MIT Press, 1999.Cohen, I. B., R. V. D. Campbell, and G. Welch, eds. Makin’ Numbers:Howard Aiken and the Computer. Cambridge, Mass.: MITPress, 1999.Ajax (Asynchronous JavaScript and XML)With the tremendous growth in Web usage comes a challengeto deliver Web-page content more efficiently and withgreater flexibility. This is desirable to serve adequately themany users who still rely on relatively low-speed dial-upInternet connections and to reduce the demand on Webservers. Ajax (asynchronous JavaScript and XML) takesadvantage of several emerging Web-development technologiesto allow Web pages to interact with users while keepingthe amount of data to be transmitted to a minimum.In keeping with modern Web-design principles, theorganization of the Web page is managed by coding inXHTML, a dialect of HTML that uses the stricter rules and

Algolgrammar of the data-description markup language XML(see html, dhtml, and xhtml and xml). Alternatively,data can be stored directly in XML. A structure calledthe DOM (Document Object Model; see dom) is used torequest data from the server, which is accessed through anobject called httpRequest. The “presentational” information(regarding such matters as fonts, font sizes and styles, justificationof paragraphs, and so on) is generally incorporatedin an associated cascading style sheet (see cascading stylesheets). Behavior such as the presentation and processingof forms or user controls is usually handled by a scriptinglanguage (for example, see JavaScript). Ajax techniques tiethese forms of processing together so that only the part ofthe Web page affected by current user activity needs to beupdated. Only a small amount of data needs to be receivedfrom the server, while most of the HTML code needed toupdate the page is generated on the client side—that is, inthe Web browser. Besides making Web pages more flexibleand interactive, Ajax also makes it much easier to developmore elaborate applications, even delivering fully functionalapplications such as word processing and spreadsheets overthe Web (see application service provider).Some critics of Ajax have decried its reliance on Java-Script, arguing that the language has a hard-to-use syntaxsimilar to the C language and poorly implements objects(see object-oriented programming). There is also a needto standardize behavior across the popular Web browsers.Nevertheless, Ajax has rapidly caught on in the Web developmentcommunity, filling bookstore shelves with bookson applying Ajax techniques to a variety of other languages(see, for example, php).Ajax can be simplified by providing a framework ofobjects and methods that the programmer can use to set upand manage the connections between server and browser.Some frameworks simply provide a set of data structuresand functions (see application program interface), whileothers include Ajax-enabled user interface components suchas buttons or window tabs. Ajax frameworks also vary inhow much of the processing is done on the server and howmuch is done on the client (browser) side. Ajax frameworksare most commonly used with JavaScript, but also exist forJava (Google Web Toolkit), PHP, C++, and Python as well asother scripting languages. An interesting example is Flapjax,a project developed by researchers at Brown University.Flapjax is a complete high-level programming language thatuses the same syntax as the popular JavaScript but hidesthe messy details of sharing and updating data between clientand server.Drawbacks and ChallengesBy their very nature, Ajax-delivered pages behave differentlyfrom conventional Web pages. Because the updatedpage is not downloaded as such from the server, thebrowser cannot record it in its “history” and allow theuser to click the “back” button to return to a previouspage. Mechanisms for counting the number of page viewscan also fail. As a workaround, programmers have sometimescreated “invisible” pages that are used to make thedesired history entries. Another problem is that since contentmanipulated using Ajax is not stored in discrete pageswith identifiable URLs, conventional search engines cannotread and index it, so a copy of the data must be providedon a conventional page for indexing. The extentto which XML should be used in place of more compactdata representations is also a concern for many developers.Finally, accessibility tools (see disabled personsand computers) often do not work with Ajax-deliveredcontent, so an alternative form must often be provided tocomply with accessibility guidelines or regulations.Despite these concerns, Ajax is in widespread use andcan be seen in action in many popular Web sites, includingGoogle Maps and the photo-sharing site Flickr.com.Further ReadingAjaxian [news and resources for Ajax developers]. Availableonline. URL: http://ajaxian.com/. Accessed April 10, 2007.Crane, David, Eric Pascarello, and Darren James. Ajax in Action.Greenwich, Conn.: Manning Publications, 2006.“Google Web Toolkit: Build AJAX Apps in the Java Language.”Available online. URL: http://code.google.com/webtoolkit/.Accessed April 10, 2007.Holzner, Steve. Ajax for Dummies. Hoboken, N.J.: Wiley, 2006.Jacobs, Sas. Beginning XML with DOM and Ajax: From Novice toProfessional. Berkeley, Calif.: Apress, 2006.Ajax is a way to quickly and efficiently update dynamic Webpages—formatting is separate from content, making it easy torevise the latter.AlgolThe 1950s and early 1960s saw the emergence of two highlevelcomputer languages into widespread use. The first wasdesigned to be an efficient language for performing scientificcalculations (see fortran). The second was designedfor business applications, with an emphasis on data processing(see cobol). However many programs continued tobe coded in low-level languages (see assembler) designedto take advantages of the hardware features of particularmachines.In order to be able to easily express and share methodsof calculation (see algorithm), leading programmers

algorithmbegan to seek a “universal” programming language thatwas not designed for a particular application or hardwareplatform. By 1957, the German GAMM (Gesellschaft fürangewandte Mathematik und Mechanik) and the AmericanACM (Association for Computing Machinery) had joinedforces to develop the specifications for such a language. Theresult became known as the Zurich Report or Algol-58, andit was refined into the first widespread implementation ofthe language, Algol-60.Language FeaturesAlgol is a block-structured, procedural language. Each variableis declared to belong to one of a small number of kindsof data including integer, real number (see data types),or a series of values of either type (see array). While thenumber of types is limited and there is no facility for definingnew types, the compiler’s type checking (making sure adata item matches the variable’s declared type) introduced alevel of security not found in most earlier languages.An Algol program can contain a number of separateprocedures or incorporate externally defined procedures(see library, program), and the variables with the samename in different procedure blocks do not interfere withone another. A procedure can call itself (see recursion).Standard control structures (see branching statementsand loop) were provided.The following simple Algol program stores the numbersfrom 1 to 10 in an array while adding them up, then printsthe total:begininteger array ints[1:10];integer counter, total;total := 0;for counter :=1 step 1 until counter > 10dobeginints [counter] := counter;total := total + ints[counter];end;printstring “The total is:”;printint (total);endAlgol’s LegacyThe revision that became known as Algol-68 expandedthe variety of data types (including the addition of boolean,or true/false values) and added user-defined typesand “structs” (records containing fields of different typesof data). Pointers (references to values) were also implemented,and flexibility was added to the parameters thatcould be passed to and from procedures.Although Algol was used as a production language insome computer centers (particularly in Europe), its relativecomplexity and unfamiliarity impeded its acceptance,as did the widespread corporate backing for the rival languagesFORTRAN and especially COBOL. Algol achievedits greatest success in two respects: for a time it becamethe language of choice for describing new algorithms forcomputer scientists, and its structural features would beadopted in the new procedural languages that emerged inthe 1970s (see Pascal and c).Further Reading“Algol 68 Home Page.” URL: http://www.algol68.org. AccessedApril 10, 2007.Backus, J. W., and others. “Revised Report on the Algorithmic LanguageAlgol 60.” Originally published in Numerische Mathematik,the Communications of the ACM, and the Journal of the BritishComputer Society. Available online. URL: http://www.masswerk.at/algol60/report.htm. Accessed April 10, 2007.algorithmWhen people think of computers, they usually think ofsilicon chips and circuit boards. Moving from relays tovacuum tubes to transistors to integrated circuits hasvastly increased the power and speed of computers, butthe essential idea behind the work computers do remainsthe algorithm. An algorithm is a reliable, definable procedurefor solving a problem. The idea of the algorithm goesback to the beginnings of mathematics and elementaryschool students are usually taught a variety of algorithms.For example, the procedure for long division by successivedivision, subtraction, and attaching the next digit isan algorithm. Since a bona fide algorithm is guaranteed towork given the specified type of data and the rote followingof a series of steps, the algorithmic approach is naturallysuited to mechanical computation.Algorithms in Computer ScienceJust as a cook learns both general techniques such as howto sauté or how to reduce a sauce and a repertoire of specificrecipes, a student of computer science learns both generalproblem-solving principles and the details of common algorithms.These include a variety of algorithms for organizingdata (see sorting and searching), for numeric problems(such as generating random numbers or finding primes),and for the manipulation of data structures (see list processingand queue).A working programmer faced with a new task first triesto think of familiar algorithms that might be applicable tothe current problem, perhaps with some adaptation. Forexample, since a variety of well-tested and well-understoodsorting algorithms have been developed, a programmer islikely to apply an existing algorithm to a sorting problemrather than attempt to come up with something entirelynew. Indeed, for most widely used programming languagesthere are packages of modules or procedures that implementcommonly needed data structures and algorithms (seelibrary, program).If a problem requires the development of a new algorithm,the designer will first attempt to determine whetherthe problem can, at least in theory, be solved (see computabilityand complexity). Some kinds of problems havebeen shown to have no guaranteed answer. If a new algorithmseems feasible, principles found to be effective in thepast will be employed, such as breaking complex problems

ALUdown into component parts or building up from the simplestcase to generate a solution (see recursion). For example,the merge-sort algorithm divides the data to be sortedinto successively smaller portions until they are sorted, andthen merges the sorted portions back together.Another important aspect of algorithm design is choosingan appropriate way to organize the data (see data structures).For example, a sorting algorithm that uses a branching(tree) structure would probably use a data structure thatimplements the nodes of a tree and the operations for adding,deleting, or moving them (see class).Once the new algorithm has been outlined (see pseudocode),it is often desirable to demonstrate that it will workfor any suitable data. Mathematical techniques such as thefinding and proving of loop invariants (where a true assertionremains true after the loop terminates) can be used todemonstrate the correctness of the implementation of thealgorithm.Practical ConsiderationsIt is not enough that an algorithm be reliable and correct,it must also be accurate and efficient enough for itsintended use. A numerical algorithm that accumulates toomuch error through rounding or truncation of intermediateresults may not be accurate enough for a scientific application.An algorithm that works by successive approximationor convergence on an answer may require too many iterationseven for today’s fast computers, or may consume toomuch of other computing resources such as memory. Onthe other hand, as computers become more and more powerfuland processors are combined to create more powerfulsupercomputers (see supercomputer and concurrentprogramming), algorithms that were previously consideredimpracticable might be reconsidered. Code profiling(analysis of which program statements are being executedthe most frequently) and techniques for creating more efficientcode can help in some cases. It is also necessary tokeep in mind special cases where an otherwise efficientalgorithm becomes much less efficient (for example, a treesort may work well for random data but will become badlyunbalanced and slow when dealing with data that is alreadysorted or mostly sorted).Sometimes an exact solution cannot be mathematicallyguaranteed or would take too much time and resources tocalculate, but an approximate solution is acceptable. A socalled“greedy algorithm” can proceed in stages, testing ateach stage whether the solution is “good enough.” Anotherapproach is to use an algorithm that can produce a reasonableif not optimal solution. For example, if a group oftasks must be apportioned among several people (or computers)so that all tasks are completed in the shortest possibletime, the time needed to find an exact solution risesexponentially with the number of workers and tasks. Butan algorithm that first sorts the tasks by decreasing lengthand then distributes them among the workers by “dealing”them one at a time like cards at a bridge table will, as demonstratedby Ron Graham, give an allocation guaranteed tobe within 4/3 of the optimal result—quite suitable for mostapplications. (A procedure that can produce a practical,though not perfect solution is actually not an algorithm buta heuristic.)An interesting approach to optimizing the solution toa problem is allowing a number of separate programs to“compete,” with those showing the best performance survivingand exchanging pieces of code (“genetic material”)with other successful programs (see genetic algorithms).This of course mimics evolution by natural selection in thebiological world.Further ReadingBerlinksi, David. The Advent of the Algorithm: The Idea That Rulesthe World. New York: Harcourt, 2000.Cormen, T. H., C. E. Leiserson, R. L. Rivest, and Clifford Stein.Introduction to Algorithms. 2nd ed. Cambridge, Mass.: MITPress, 2001.Knuth, Donald E. The Art of Computer Programming. Vol. 1: FundamentalAlgorithms. 3rd ed. Reading, Mass.: Addison-Wesley,1997. Vol. 2: Seminumerical Algorithms. 3rd ed. Reading, Mass.:Addison-Wesley, 1997. Vol. 3: Searching and Sorting. 2nd ed.Reading, Mass.: Addison-Wesley, 1998.ALU See arithmetic logic unit.Amazon.comBeginning modestly in 1995 as an online bookstore, Amazon.combecame one of the first success stories of the earlyInternet economy (see also e-commerce).Named for the world’s largest river, Amazon.com wasthe brainchild of entrepreneur Jeffrey Bezos (see Bezos,Jeffrey P.). Like a number of other entrepreneurs of theearly 1990s, Bezos had been searching for a way to marketto the growing number of people who were going online.He soon decided that books were a good first product, sincethey were popular, nonperishable, relatively compact, andeasy to ship.Several million books are in print at any one time,with about 275,000 titles or editions added in 2007 inthe United States alone. Traditional “brick and mortar”(physical) bookstores might carry a few thousand titlesup to perhaps 200,000 for the largest chains. Bookstoresin turn stock their shelves mainly through major bookdistributors that serve as intermediaries between publishersand the public.For an online bookstore such as Amazon.com, however,the number of titles that can be made available is limitedonly by the amount of warehouse space the store is willingto maintain—and no intermediary between publisher andbookseller is needed. From the start, Amazon.com’s businessmodel has capitalized on this potential for variety andthe ability to serve almost any niche interest. Over the yearsthe company’s offerings have expanded beyond books to34 different categories of merchandise, including software,music, video, electronics, apparel, home furnishings, andeven nonperishable gourmet food and groceries. (Amazon.com also entered the online auction market, but remains adistant runner-up to market leader eBay).

Amazon.comExpansion and ProfitabilityBecause of its desire to build a very diverse product line,Amazon.com, unusually for a business startup, did notexpect to become profitable for about five years. The growingrevenues were largely poured back into expansion.In the heated atmosphere of the Internet boom of thelate 1990s, many other Internet-based businesses echoedthat philosophy, and many went out of business followingthe bursting of the so-called dot-com bubble of theearly 2000s. Some analysts questioned whether even thehugely popular Amazon.com would ever be able to convertits business volume into an operating profit. However,the company achieved its first profitable year in 2003(with a modest $35 million surplus). Since then growthhas remained steady and generally impressive: In 2005,Amazon.com earned $8.49 billion revenues with a netincome of $359 million. By then the company had about12,000 employees and had been added to the S&P 500stock index.In 2006 the company maintained its strategy of investingin innovation rather than focusing on short-term profits.Its latest initiatives include selling digital versions ofbooks (e-books) and magazine articles, new arrangementsto sell video content, and even a venture into moviemaking.By year end, annual revenue had increased to $10.7 billion.In November 2007 Amazon announced the Kindle, abook reader (see e-books and digital libraries) with asharp “paper-like” display. In addition to books, the Kindlecan also subscribe to and download magazines, contentfrom newspaper Web sites, and even blogs.As part of its expansion strategy, Amazon.com hasacquired other online bookstore sites including Borders.comand Waldenbooks.com. The company has also expandedgeographically with retail operations in Canada, the UnitedKingdom, France, Germany, Japan, and China.Amazon.com has kept a tight rein on its operations evenwhile continually expanding. The company’s leading marketposition enables it to get favorable terms from publishersand manufacturers. A high degree of warehouse automationand an efficient procurement system keep stock movingquickly rather than taking up space on the shelves.Information-Based StrategiesAmazon.com has skillfully taken advantage of informationtechnology to expand its capabilities and offerings. Examplesof such efforts include new search mechanisms, cultivationof customer relationships, and the development ofnew ways for users to sell their own goods.Amazon’s “Search Inside the Book” feature is a goodexample of leveraging search technology to take advantageof having a growing amount of text online. If the publisherof a book cooperates, its actual text is made available foronline searching. (The amount of text that can be displayedis limited to prevent users from being able to read entirebooks for free.) Further, one can see a list of books citing(or being cited by) the current book, providing yet anotherway to explore connections between ideas as used by differentauthors. Obviously for Amazon.com, the ultimatereason for offering all these useful features is that morepotential customers may be able to find and purchase bookson even the most obscure topics.Amazon.com’s use of information about customers’buying histories is based on the idea that the more oneknows about what customers have wanted in the past, themore effectively they can be marketed to in the futurethrough customizing their view of the site. Users receiveautomatically generated recommendations for books orother items based on their previous purchases (see alsocustomer relationship management). There is even a“plog” or customized Web log that offers postings relatedto the user’s interests and allows the user to respond.There are other ways in which Amazon.com tries toinvolve users actively in the marketing process. For example,users are encouraged to review books and other productsand to create lists that can be shared with other users.The inclusion of both user and professional reviews in turnmakes it easier for prospective purchasers to determinewhether a given book or other item is suitable. Authors aregiven the opportunity through “Amazon Connect” to provideadditional information about their books. Finally, inlate 2005 Amazon replaced an earlier “discussion board”facility with a wiki system that allows purchasers to createor edit an information page for any product (see wikisand Wikipedia).The company’s third major means of expansion is tofacilitate small businesses and even individual users inthe marketing of their own goods. Amazon Marketplace,a service launched in 2001, allows users to sell a variety ofitems, with no fees charged unless the item is sold. Thereare also many provisions for merchants to set up online“storefronts” and take advantage of online payment andother services.Another aspect of Amazon’s marketing is its referral network.Amazon’s “associates” are independent businessesthat provide links from their own sites to products on Amazon.For example, a seller of crafts supplies might includeon its site links to books on crafting on the Amazon site. Inreturn, the referring business receives a commission fromAmazon.com.Although often admired for its successful business plan,Amazon.com has received criticism from several quarters.Some users have found the company’s customer service(which is handled almost entirely by e-mail) to beunresponsive. Meanwhile local and specialized bookstores,already suffering in recent years from the competition oflarge chains such as Borders and Barnes and Noble, haveseen in Amazon.com another potent threat to the survivalof their business. (The company’s size and economic powerhave elicited occasional comparisons with Wal-Mart.)Finally, Amazon.com has been criticized by some laboradvocates for paying low wages and threatening to terminateworkers who sought to unionize.Further ReadingAmazon.com Web site. Available online. URL: http://www.amazon.com. Accessed August 28, 2007.Daisey, Mike. 21 Dog Years: Doing Time @ Amazon.com. New York:The Free Press, 2002.Marcus, James. Amazonia. New York: New Press, 2005.

10 Amdahl, Gene MyronShanahan, Francis. Amazon.com Mashups. New York: Wrox/Wiley,2007.Spector, Robert. Amazon.com: Get Big Fast: Inside the RevolutionaryBusiness Model That Changed the World. New York: Harper-Business, 2002.Amdahl, Gene Myron(1922– )AmericanInventor, EntrepreneurGene Amdahl played a major role in designing and developingthe mainframe computer that dominated data processingthrough the 1970s (see mainframe). Amdahl was bornon November 16, 1922, in Flandreau, South Dakota. Afterhaving his education interrupted by World War II, Amdahlreceived a B.S. from South Dakota State University in 1948and a Ph.D. in physics at the University of Wisconsin in1952.As a graduate student Amdahl had realized that furtherprogress in physics and other sciences required better,faster tools for computing. At the time there were only a fewcomputers, and the best approach to getting access to significantcomputing power seemed to be to design one’s ownmachine. Amdahl designed a computer called the WISC(Wisconsin Integrally Synchronized Computer). This computerused a sophisticated procedure to break calculationsinto parts that could be carried out on separate processors,making it one of the earliest examples of the parallel computingtechniques found in today’s computer architectures.Designer for IBMIn 1952 Amdahl went to work for IBM, which had committeditself to dominating the new data processing industry.Amdahl worked with the team that eventually designed theIBM 704. The 704 improved upon the 701, the company’sfirst successful mainframe, by adding many new internalprogramming instructions, including the ability to performfloating point calculations (involving numbers thathave decimal points). The machine also included a fast,high-capacity magnetic core memory that let the machineretrieve data more quickly during calculations. In November1953 Amdahl became the chief project engineer forthe 704 and then helped design the IBM 709, which wasdesigned especially for scientific applications.When IBM proposed extending the technology by buildinga powerful new scientific computer called STRETCH,Amdahl eagerly applied to head the new project. However,he ended up on the losing side of a corporate power struggle,and did not receive the post. He left IBM at the end of1955.In 1960 Amdahl rejoined IBM, where he was sooninvolved in several design projects. The one with the mostlasting importance was the IBM System/360, which wouldbecome the most ubiquitous and successful mainframe computerof all time. In this project Amdahl further refined hisideas about making a computer’s central processing unitmore efficient. He designed logic circuits that enabled theprocessor to analyze the instructions waiting to be executed(the “pipeline”) and determine which instructions could beexecuted immediately and which would have to wait for theresults of other instructions. He also used a cache, or specialmemory area, in which the instructions that would be needednext could be stored ahead of time so they could be retrievedimmediately when needed. Today’s desktop PCs use thesesame ideas to get the most out of their chips’ capabilities.Amdahl also made important contributions to thefurther development of parallel processing. Amdahl createda formula called Amdahl’s law that basically says thatthe advantage gained from using more processors graduallydeclines as more processor are added. The amount ofimprovement is also proportional to how much of the calculationcan be broken down into parts that can be run inparallel. As a result, some kinds of programs can run muchfaster with several processors being used simultaneously,while other programs may show little improvement.In the mid-1960s Amdahl helped establish IBM’sAdvanced Computing Systems Laboratory in Menlo Park,California, which he directed. However, he became increasinglyfrustrated with what he thought was IBM’s too rigidapproach to designing and marketing computers. Hedecided to leave IBM again and, this time, challenge it inthe marketplace.Creator of “clones”Amdahl resolved to make computers that were more powerfulthan IBM’s machines, but that would be “plug compatible”with them, allowing them to use existing hardware andsoftware. To gain an edge over the computer giant, Amdahlwas able to take advantage of the early developments inintegrated electronics to put more circuits on a chip withoutmaking the chips too small, and thus too crowded forplacing the transistors.Thanks to the use of larger scale circuit integration,Amdahl could sell machines with superior technology tothat of the IBM 360 or even the new IBM 370, and at alower price. IBM responded belatedly to the competition,making more compact and faster processors, but Amdahlmet each new IBM product with a faster, cheaper alternative.However, IBM also countered by using a sales techniquethat opponents called FUD (fear, uncertainty, anddoubt). IBM salespersons promised customers that IBMwould soon be coming out with much more powerful andeconomical alternatives to Amdahl’s machines. As a result,many would-be customers were persuaded to postpone purchasingdecisions and stay with IBM. Amdahl Corporationbegan to falter, and Gene Amdahl gradually sold his stockand left the company in 1980.Amdahl then tried to repeat his success by starting anew company called Trilogy. The company promisedto build much faster and cheaper computers than thoseoffered by IBM or Amdahl. He believed he could accomplishthis by using the new, very-large-scale integrated siliconwafer technology in which circuits were deposited in layerson a single chip rather than being distributed on separatechips on a printed circuit board. But the problem of dealingwith the electrical characteristics of such dense circuitry,

America Online 11as well as some design errors, somewhat crippled the newcomputer design. Amdahl was forced to repeatedly delaythe introduction of the new machine, and Trilogy failed inthe marketplace.Amdahl’s achievements could not be overshadowed bythe failures of his later career. He has received many industryawards, including Data Processing Man of the Year bythe Data Processing Management Association (1976), theHarry Goode Memorial Award from the American Federationof Information Processing Societies, and the SIGDA PioneeringAchievement Award (2007).Further Reading“Gene Amdahl.” Available online. URL: http://www.thocp.net/biographies/amdahl_gene.htm. Accessed April 10, 2007.Slater, Robert. Portraits in Silicon. Cambridge, Mass.: MIT Press,1987.America Online (AOL)For millions of PC users in the 1990s, “going online” meantconnecting to America Online. However, this once dominantservice provider has had difficulty adapting to thechanging world of the Internet.By the mid-1980s a growing number of PC users werestarting to go online, mainly dialing up small bulletin boardservices. Generally these were run by individuals from theirhomes, offering a forum for discussion and a way for usersto upload and download games and other free software andshareware (see bulletin board systems). However, someentrepreneurs saw the possibility of creating a commercialinformation service that would be interesting and usefulenough that users would pay a monthly subscription feefor access. Perhaps the first such enterprise to be successfulwas Quantum Computer Services, founded by Jim Kimseyin 1985 and soon joined by another young entrepreneur,Steve Case. Their strategy was to team up with personalcomputer makers such as Commodore, Apple, and IBM toprovide special online services for their users.In 1989 Quantum Link changed its name to AmericaOnline (AOL). In 1991 Steve Case became CEO, taking overfrom the retiring Kimsey. Case’s approach to marketing AOLwas to aim the service at novice PC users who had troublemastering arcane DOS (disk operating system) commandsand interacting with text-based bulletin boards and primitiveterminal programs. As an alternative, AOL provided acomplete software package that managed the user’s connection,presented “friendly” graphics, and offered point-andclickaccess to features.Chat rooms and discussion boards were also expandedand offered in a variety of formats for casual and more formaluse. Gaming, too, was a major emphasis of the earlyAOL, with some of the first online multiplayer fantasy roleplayinggames such as a version of Dungeons and Dragonscalled Neverwinter Nights (see online games). A third popularapplication has been instant messaging (IM), includinga feature that allowed users to set up “buddy lists” of theirfriends and keep track of when they were online (see alsotexting and instant messaging).Internet ChallengeBy 1996 the World Wide Web was becoming popular (seeWorld Wide Web). Rather than signing up with a proprietaryservice such as AOL, users could simply get an accountwith a lower-cost direct-connection service (see Internetservice provider) and then use a Web browser such asNetscape to access information and services. AOL was slowin adapting to the growing use of the Internet. At first, theservice provided only limited access to the Web (and onlythrough its proprietary software). Gradually, however, AOLoffered a more seamless Web experience, allowing users torun their own browsers and other software together withthe proprietary interface. Also, responding to competition,AOL replaced its hourly rates with a flat monthly fee ($19.95at first).Overall, AOL increasingly struggled with trying to fulfilltwo distinct roles: Internet access provider and contentprovider. By the late 1990s AOL’s monthly rates were higherthan those of “no frills” access providers such as NetZero.AOL tried to compensate for this by offering integration ofservices (such as e-mail, chat, and instant messaging) andnews and other content not available on the open Internet.AOL also tried to shore up its user base with aggressivemarketing to users who wanted to go online but were notsure how to do so. Especially during the late 1990s, AOLwas able to swell its user rolls to nearly 30 million, largelyby providing millions of free CDs (such as in magazineinserts) that included a setup program and up to a month offree service. But while it was easy to get started with AOL,some users began to complain that the service would keepbilling them even after they had repeatedly attempted tocancel it. Meanwhile, AOL users got little respect from themore sophisticated inhabitants of cyberspace, who oftencomplained that the clueless “newbies” were clutteringnewsgroups and chat rooms.In 2000 AOL and Time Warner merged. At the time, thedeal was hailed as one of the greatest mergers in corporateAmerica Online (AOL) was a major online portal in the 1990s,but has faced challenges adapting to the modern world of theWeb. (Screen image credit: AOL)

12 analog and digitalhistory, bringing together one of the foremost Internet companieswith one of the biggest traditional media companies.The hope was that the new $350 billion company wouldbe able to leverage its huge subscriber base and rich mediaresources to dominate the online world.From Service to Content ProviderBy the 2000s, however, an increasing number of peoplewere switching from dial-up to high-speed broadband Internetaccess (see broadband) rather than subscribing to servicessuch as AOL simply to get online. This trend and theoverall decline in the Internet economy early in the decade(the “dot-bust”) contributed to a record loss of $99 billionfor the combined company in 2002. In a shakeup, Time-Warner dropped “AOL” from its name, and Steve Case wasreplaced as executive chairman. The company increasinglybegan to shift its focus to providing content and servicesthat would attract people who were already online, withrevenue coming from advertising instead of subscriptions.In October 2006 the AOL division of Time-Warner(which by then had dropped the full name America Online)announced that it would provide a new interface and softwareoptimized for broadband users. AOL’s OpenRidedesktop presents users with multiple windows for e-mail,instant messaging, Web browsing, and media (video andmusic), with other free services available as well. Theseofferings are designed to compete in a marketplace wherethe company faces stiff competition from other major Internetpresences who have been using the advertising-basedmodel for years (see Yahoo! and Google).Further ReadingAOL Web site. Available online. URL: http://www.aol.com.Accessed August 28, 2007.Kaufeld, John. AOL for Dummies. 2nd ed. Hoboken, N.J.: Wiley,2004.Klein, Alec. Stealing Time: Steve Case, Jerry Levin, and the Collapseof AOL Time Warner. New York: Simon & Schuster, 2003.Mehta, Stephanie N. “Can AOL Keep Pace?” Fortune, August 21,2006, p. 29.Swisher, Kara. AOL.COM: How Steve Case Beat Bill Gates, Nailed theNetheads, and Made Millions in the War for the Web. New York:Times Books, 1998.analog and digitalThe word analog (derived from Greek words meaning “byratio”) denotes a phenomenon that is continuously variable,such as a sound wave. The word digital, on the otherhand, implies a discrete, exactly countable value that can berepresented as a series of digits (numbers). Sound recordingprovides familiar examples of both approaches. Recordinga phonograph record involves electromechanically transferringa physical signal (the sound wave) into an “analogous”physical representation (the continuously varying peaksand dips in the record’s surface). Recording a CD, on theother hand, involves sampling (measuring) the sound levelat thousands of discrete instances and storing the results ina physical representation of a numeric format that can inturn be used to drive the playback device.Most natural phenomena such as light or sound intensity are analogvalues that vary continuously. To convert such measurementsto a digital representation, “snapshots” or sample readings must betaken at regular intervals. Sampling more frequently gives a moreaccurate representation of the original analog data, but at a cost inmemory and processor resources.Virtually all modern computers depend on the manipulationof discrete signals in one of two states denoted by thenumbers 1 and 0. Whether the 1 indicates the presence ofan electrical charge, a voltage level, a magnetic state, a pulseof light, or some other phenomenon, at a given point thereis either “something” (1) or “nothing” (0). This is the mostnatural way to represent a series of such states.Digital representation has several advantages over analog.Since computer circuits based on binary logic can bedriven to perform calculations electronically at ever-increasingspeeds, even problems where an analog computer bettermodeled nature can now be done more efficiently with digitalmachines (see analog computer). Data stored in digitizedform is not subject to the gradual wear or distortion ofthe medium that plagues analog representations such as thephonograph record. Perhaps most important, because digitalrepresentations are at base simply numbers, an infinitevariety of digital representations can be stored in files andmanipulated, regardless of whether they started as pictures,music, or text (see digital convergence).Converting between Analog andDigital RepresentationsBecause digital devices (particularly computers) are themechanism of choice for working with representations oftext, graphics, and sound, a variety of devices are used todigitize analog inputs so the data can be stored and manipulated.Conceptually, each digitizing device can be thoughtof as having three parts: a component that scans the inputand generates an analog signal, a circuit that converts theanalog signal from the input to a digital format, and a componentthat stores the resulting digital data for later use. Forexample, in the ubiquitous flatbed scanner a moving headreads varying light levels on the paper and converts them to

analog computer 13a varying level of current (see scanner). This analog signalis in turn converted into a digital reading by an analog-todigitalconverter, which creates numeric information thatrepresents discrete spots (pixels) representing either levelsof gray or of particular colors. This information is thenwritten to disk using the formats supported by the operatingsystem and the software that will manipulate them.Further ReadingChalmers, David J. “Analog vs. Digital Computation.” Availableonline. URL: http://www.u.arizona.edu/~chalmers/notes/analog.html.Accessed April 10, 2007.Hoeschele, David F. Analog-to-Digital and Digital-to-Analog ConversionTechniques. 2nd ed. New York: Wiley-Interscience, 1994.analog computerMost natural phenomena are analog rather than digital innature (see analog and digital). But just as mathematicallaws can describe relationships in nature, these relationshipsin turn can be used to construct a model in whichnatural forces generate mathematical solutions. This is thekey insight that leads to the analog computer.The simplest analog computers use physical componentsthat model geometric ratios. The earliest known analogcomputing device is the Antikythera Mechanism. Constructedby an unknown scientist on the island of Rhodesaround 87 b.c., this device used a precisely crafted differentialgear mechanism to mechanically calculate the intervalbetween new moons (the synodic month). (Interestingly,the differential gear would not be rediscovered until 1877.)Another analog computer, the slide rule, became theconstant companion of scientists, engineers, and studentsuntil it was replaced by electronic calculators in the 1970s.Invented in simple form in the 17th century, the slide rule’smovable parts are marked in logarithmic proportions,allowing for quick multiplication, division, the extractionof square roots, and sometimes the calculation of trigonometricfunctions.The next insight involved building analog devices thatset up dynamic relationships between mechanical movements.In the late 19th century two British scientists, JamesThomson and his brother Sir William Thomson (later LordKelvin) developed the mechanical integrator, a devicethat could solve differential equations. An important newprinciple used in this device is the closed feedback loop,where the output of the integrator is fed back as a newset of inputs. This allowed for the gradual summation orintegration of an equation’s variables. In 1931, VannevarBush completed a more complex machine that he called a“differential analyzer.” Consisting of six mechanical integratorsusing specially shaped wheels, disks, and servomechanisms,the differential analyzer could solve equationsin up to six independent variables. As the usefulness andapplicability of the device became known, it was quicklyreplicated in various forms in scientific, engineering, andmilitary institutions.These early forms of analog computer are based on fixedgeometrical ratios. However, most phenomena that scientistsand engineers are concerned with, such as aerodynamics,fluid dynamics, or the flow of electrons in a circuit,involve a mathematical relationship between forces wherethe output changes smoothly as the inputs are changed. The“dynamic” analog computer of the mid-20th century tookadvantage of such force relationships to construct deviceswhere input forces represent variables in the equation, andConverting analog data to digital involves several steps. A sensor (such as the CCD, or charge-coupled device in a digital camera) createsa varying electrical current. An amplifier can strengthen this signal to make it easier to process, and filters can eliminate spurious spikes or“noise.” The “conditioned” signal is then fed to the analog-to-digital (A/D) converter, which produces numeric data that is usually stored in amemory buffer from which it can be processed and stored by the controlling program.

14 Andreessen, MarcCompleted in 1931, Vannevar Bush’s Differential Analyzer was a triumph of analog computing. The device could solve equations with up tosix independent values. (MIT Museum)nature itself “solves” the equation by producing a resultingoutput force.In the 1930s, the growing use of electronic circuitsencouraged the use of the flow of electrons rather thanmechanical force as a source for analog computation. Thekey circuit is called an operational amplifier. It generatesa highly amplified output signal of opposite polarity to theinput, over a wide range of frequencies. By using componentssuch as potentiometers and feedback capacitors, ananalog computer can be programmed to set up a circuit inwhich the laws of electronics manipulate the input voltagesin the same way the equation to be solved manipulates itsvariables. The results of the calculation are then read as aseries of voltage values in the final output.Starting in the 1950s, a number of companies marketedlarge electronic analog computers that containedmany separate computing units that could be harnessedtogether to provide “real time” calculations in which theresults could be generated at the same rate as the actualphenomena being simulated. In the early 1960s, NASA setup training simulations for astronauts using analog realtimesimulations that were still beyond the capability ofdigital computers.Gradually, however, the use of faster processors andlarger amounts of memory enabled the digital computer tosurpass its analog counterpart even in the scientific programmingand simulations arena. In the 1970s, some hybridmachines combined the easy programmability of a digital“front end” with analog computation, but by the end of thatdecade the digital computer had rendered analog computersobsolete.Further Reading“Analog Computers.” Computer Museum, University of Amsterdam.Available online. URL: http://www.science.uva.n/museum/AnalogComputers.html. Accessed April 18, 2007.Hoeschele, David F., Jr. Analog-to-Digital and Digital-to-AnalogConversion Techniques. 2nd ed. New York: John Wiley, 1994.Vassos, Basil H., and Galen Ewing, eds. Analog and Computer Electronicsfor Scientists. 4th ed. New York: John Wiley, 1993.Andreessen, Marc(1971– )AmericanEntrepreneur, ProgrammerMarc Andreessen brought the World Wide Web and itswealth of information, graphics, and services to the desktop,setting the stage for the first “e-commerce” revolutionof the later 1990s. As founder of Netscape, Andreessen also

Andreessen, Marc 15created the first big “dot-com,” or company doing businesson the Internet.Born on July 9, 1971, in New Lisbon, Wisconsin,Andreessen grew up as part of a generation that wouldbecome familiar with personal computers, computer games,and graphics. By seventh grade Andreessen had his own PCand was programming furiously. He then studied computerscience at the University of Illinois at Urbana-Champaign,where his focus on computing was complemented by a wideranginginterest in music, history, literature, and business.By the early 1990s the World Wide Web (see WorldWide Web and Berners-Lee, Tim) was poised to changethe way information and services were delivered to users.However, early Web pages generally consisted only oflinked pages of text, without point-and-click navigation orthe graphics and interactive features that adorn Web pagestoday.Andreessen learned about the World Wide Web shortlyafter Berners-Lee introduced it in 1991. Andreessen thoughtit had great potential, but also believed that there neededto be better ways for ordinary people to access the newMarc Andreessen, Chairman of Loudcloud, Inc., speaks at Fortunemagazine’s “Leadership in Turbulent Times” conference on November8, 2001, in New York City. (Photo by Mario Tama/GettyImages)medium. In 1993, Andreessen, together with colleague EricBina and other helpers at the National Center for SupercomputingApplications (NCSA), set to work on what becameknown as the Mosaic Web browser. Since their work waspaid for by the government, Mosaic was offered free tousers over the Internet. Mosaic could show pictures as wellas text, and users could follow Web links simply by clickingon them with the mouse. The user-friendly programbecame immensely popular, with more than 10 millionusers by 1995.After earning a B.S. in computer science, Andreessen leftMosaic, having battled with its managers over the future ofWeb-browsing software. He then met Jim Clark, an olderentrepreneur who had been CEO of Silicon Graphics. Theyfounded Netscape Corporation in 1994, using $4 millionseed capital provided by Clark.Andreessen recruited many of his former colleagues atNCSA to help him write a new Web browser, which becameknown as Netscape Navigator. Navigator was faster andmore graphically attractive than Mosaic. Most important,Netscape added a secure encrypted facility that people coulduse to send their credit card numbers to online merchants.This was part of a two-pronged strategy: First, attract thelion’s share of Web users to the new browser, and then sellbusinesses the software they would need to create effectiveWeb pages for selling products and services to users.By the end of 1994 Navigator had gained 70 percentof the Web browser market. Time magazine namedthe browser one of the 10 best products of the year, andNetscape was soon selling custom software to companiesthat wanted a presence on the Web. The e-commerce boomof the later 1990s had begun, and Marc Andreessen was oneof its brightest stars. When Netscape offered its stock to thepublic in summer 1995, the company gained a total worthof $2.3 billion, more than that of many traditional bluechipindustrial companies. Andreessen’s own shares wereworth $55 million.Battle with MicrosoftMicrosoft (see Microsoft and Gates, Bill) had been slowto recognize the growing importance of the Web, but by themid-1990s Gates had decided that the software giant had tohave a comprehensive “Internet strategy.” In particular, thecompany had to win control of the browser market so userswould not turn to “platform independent” software thatcould deliver not only information but applications, withoutrequiring the use of Windows at all.Microsoft responded by creating its own Web browser,called Internet Explorer. Although technical reviewers generallyconsidered the Microsoft product to be inferior toNetscape, it gradually improved. Most significantly, Microsoftincluded Explorer with its new Windows 95 operatingsystem. This “bundling” meant that PC makers and consumershad little interest in paying for Navigator when theyalready had a “free” browser from Microsoft. In responseto this move, Netscape and other Microsoft competitorshelped promote the antitrust case against Microsoft thatwould result in 2001 in some of the company’s practicesbeing declared an unlawful use of monopoly power.

16 animation, computerAndreessen tried to respond to Microsoft by focusingon the added value of his software for Web servers whilemaking Navigator “open source,” meaning that anyone wasallowed to access and modify the program’s code (see opensource). He hoped that a vigorous community of programmersmight help keep Navigator technically superior toInternet Explorer. However, Netscape’s revenues began todecline steadily. In 1999 America Online (AOL) bought thecompany, seeking to add its technical assets and Webcenteronline portal to its own offerings (see America Online).After a brief stint with AOL as its “principal technicalvisionary,” Andreessen decided to start his own company,called LoudCloud. The company provided Web-site development,management, and custom software (including e-commerce “shopping basket” systems) for corporations thathad large, complex Web sites. However, the company wasnot successful; Andreessen sold its Web-site-managementcomponent to Texas-based Electronic Data Systems (EDS)while retaining its software division under the new nameOpsware. In 2007 Andreessen scored another coup, sellingOpsware to Hewlett-Packard (HP) for $1.6 billion.In 2007 Andreessen launched Ning, a company thatoffers users the ability to add blogs, discussion forums, andother features to their Web sites, but facing established competitorssuch as MySpace (see also social networking). InJuly 2008 Andresseen joined the board of Facebook.While the future of his recent ventures remains uncertain,Marc Andreessen’s place as one of the key pioneers ofthe Web and e-commerce revolution is assured. His inventiveness,technical insight, and business acumen made hima model for a new generation of Internet entrepreneurs.Andreessen was named one of the Top 50 People under theAge of 40 by Time magazine (1994) and has received theComputerworld/Smithsonian Award for Leadership (1995)and the W. Wallace McDowell Award of the IEEE ComputerSociety (1997).Further ReadingClark, Jim. Netscape Time: The Making of the Billion-Dollar StartupThat Took on Microsoft. New York: St. Martin’s Press, 1999.Guynn, Jessica. “Andreessen Betting Name on New Ning.” SanFrancisco Chronicle, February 27, 2006, p. D1, D4.Payment, Simone. Marc Andreessen and Jim Clark: The Founders ofNetscape. New York: Rosen Pub. Group, 2006.Quittner, Joshua, and Michelle Slatala. Speeding the Net: The InsideStory of Netscape and How It Challenged Microsoft. New York:Atlantic Monthly Press, 1998.animation, computerEver since the first hand-drawn cartoon features entertainedmoviegoers in the 1930s, animation has been an importantpart of the popular culture. Traditional animation uses aseries of hand-drawn frames that, when shown in rapidsuccession, create the illusion of lifelike movement.Computer Animation TechniquesThe simplest form of computer animation (illustrated ingames such as Pong) involves drawing an object, then erasingit and redrawing it in a different location. A somewhatmore sophisticated approach can create motion in a sceneby displaying a series of pre-drawn images called sprites—for example, there could be a series of sprites showing asword-wielding troll in different positions.Since there are only a few intermediate images, the useof sprites doesn’t convey truly lifelike motion. Modernanimation uses a modern version of the traditional drawnanimation technique. The drawings are “keyframes” thatcapture significant movements by the characters. The keyframesare later filled in with transitional frames in a processcalled tweening. Since it is possible to create algorithmsthat describe the optimal in-between frames, the advent ofsufficiently powerful computers has made computer animationboth possible and desirable. Today computer animationis used not only for cartoons but also for video games andmovies. The most striking use of this technique is morphing,where the creation of plausible intermediate imagesbetween two strikingly different faces creates the illusion ofone face being transformed into the other.Algorithms that can realistically animate people, animals,and other complex objects require the ability to createa model that includes the parts of the object that can moveseparately (such as a person’s arms and legs). Because themovement of one part of the model often affects the positionsof other parts, a treelike structure is often used todescribe these relationships. (For example, an elbow movesan arm, the arm in turn moves the hand, which in turnmoves the fingers). Alternatively, live actors performing arepertoire of actions or poses can be digitized using wearablesensors and then combined to portray situations, suchas in a video game.Less complex objects (such as clouds or rainfall) can betreated in a simpler way, as a collection of “particles” thatmove together following basic laws of motion and gravity.Of course when different models come into contact (forexample, a person walking in the rain), the interactionbetween the two must also be taken into consideration.While realism is always desirable, there is inevitablya tradeoff between the resources available. Computationallyintensive physics models might portray a very realisticspray of water using a high-end graphics workstation, butsimplified models have to be used for a program that runson a game console or desktop PC. The key variables are theframe rate (higher is smoother) and the display resolution.The amount of available video memory is also a consideration:many desktop PCs sold today have 256MB or more ofvideo memory.ApplicationsComputer animation is used extensively in many featurefilms, such as for creating realistic dinosaurs (JurassicPark) or buglike aliens (Starship Troopers). Computergames combine animation techniques with other techniques(see computer graphics) to provide smoothaction within a vivid 3D landscape. Simpler forms of animationare now a staple of Web site design, often writtenin Java or with the aid of animation scripting programssuch as Adobe Flash.

API 17The intensive effort that goes into contemporary computeranimation suggests that the ability to fascinate thehuman eye that allowed Walt Disney to build an empire isjust as compelling today.Further Reading“3-D Animation Workshop.” Available online. URL: http://www.webreference.com/3d/indexa.html. Accessed April 12, 2007.Comet, Michael B. “Character Animation: Principles and Practice.”Available online. URL: http://www.comet-cartoons.com/toons/3ddocs/charanim. Accessed April 12, 2007.Hamlin, J. Scott. Effective Web Animation: Advanced Techniques forthe Web. Reading, Mass.: Addison-Wesley, 1999.O’Rourke, Michael. Principles of Three-Dimensional Computer Animation:Modeling, Rendering, and Animating with 3D ComputerGraphics. New York: Norton, 1998.Parent, Rick. Computer Animation: Algorithms and Techniques. SanFrancisco: Morgan Kaufmann, 2002.Shupe, Richard, and Robert Hoekman. Flash 8: Projects for LearningAnimation and Interactivity. Sebastapol, Calif.: O’ReillyMedia, 2006.anonymity and the InternetAnonymity, or the ability to communicate without disclosinga verifiable identity, is a consequence of the way mostInternet-based e-mail, chat, or news services were designed(see e-mail, chat, texting and instant messaging, andnetnews and newgroups). This does not mean that messagesdo not have names attached. Rather, the names canbe arbitrarily chosen or pseudonymous, whether reflectingdevelopment of an online persona or the desire to avoidhaving to take responsibility for unwanted communications(see spam).AdvantagesIf a person uses a fixed Internet address (see tcp/ip), it maybe possible to eventually discover the person’s location andeven identity. However, messages can be sent through anonymousremailing services where the originating address isremoved. Web browsing can also be done “at arm’s length”through a proxy server. Such means of anonymity can arguablyserve important values, such as allowing persons livingunder repressive governments (or who belong to minoritygroups) to express themselves more freely precisely becausethey cannot be identified. However, such techniques requiresome sophistication on the part of the user. With ordinaryusers using their service provider accounts directly, governments(notably China) have simply demanded that theuser’s identity be turned over when a crime is alleged.Pseudonymity (the ability to choose names separatefrom one’s primary identity) in such venues as chat roomsor online games can also allow people to experiment withdifferent identities or roles, perhaps getting a taste of howmembers of a different gender or ethnic group are perceived(see identity in the online world).Anonymity can also help protect privacy, especially incommercial transactions. For example, purchasing somethingwith cash normally requires no disclosure of the purchaser’sidentity, address, or other personal information.Various systems can use secure encryption to create a cashequivalent in the online world that assures the merchantof valid payment without disclosing unnecessary informationabout the purchaser (see digital cash). There are alsofacilities that allow for essentially anonymous Web browsing,preventing the aggregation or tracking of information(see cookies).ProblemsThe principal problem with anonymity is that it can allowthe user to engage in socially undesirable or even criminalactivity with less fear of being held accountable. The combinationof anonymity (or the use of a pseudonym) and thelack of physical presence seems to embolden some peopleto engage in insult or “flaming,” where they might be inhibitedin an ordinary social setting. A few services (notablyThe WELL) insist that the real identity of all participantsbe available even if postings use a pseudonym.Spam or deceptive e-mail (see phishing and spoofing)takes advantage both of anonymity (making it hardfor authorities to trace) and pseudonymity (the abilityto disguise the site by mimicking a legitimate business).Anonymity makes downloading or sharing files easier(see file-sharing and P2P networks), but also makesit harder for owners of videos, music, or other content topursue copyright violations. Because of the prevalence offraud and other criminal activity on the Internet, therehave been calls to restrict the ability of online users toremain anonymous, and some nations such as South Koreahave enacted legislation to that effect. However, civil libertariansand privacy advocates believe that the impact onfreedom and privacy outweighs any benefits for securityand law enforcement.The database of Web-site registrants (called Whois)provides contact information intended to ensure thatsomeone will be responsible for a given site and be willingto cooperate to fix technical or administrative problems.At present, Whois information is publicly available.However, the Internet Corporation for Assigned Namesand Numbers (ICANN) is considering making the contactinformation available only to persons who can show alegitimate need.Further ReadingLessig, Lawrence. Code: Version 2.0. New York: Basic Books, 2006.Rogers, Michael. “Let’s See Some ID, Please: The End of Anonymityon the Internet?” The Practical Futurist (MSNBC), December13, 2005. Available online. URL: http://www.msnbc.msn.com/ID/10441443/. Accessed April 10, 2007.Wallace, Jonathan D. “Nameless in Cyberspace: Anonymity on theInternet.” CATO Institute Briefing Papers, no. 54, December8, 1999. Available online. URL: http://www.cato.org/pubs/briefs/bp54.pdf. Accessed April 10, 2007.AOL See America Online.API See applications program interface.

18 APLAPL (a programming language)This programming language was developed by Harvard(later IBM) researcher Kenneth E. Iverson in the early 1960sas a way to express mathematical functions clearly andconsistently for computer use. The power of the languageto compactly express mathematical functions attracted agrowing number of users, and APL soon became a full general-purposecomputing language.Like many versions of BASIC, APL is an interpreted language,meaning that the programmer’s input is evaluated“on the fly,” allowing for interactive response (see interpreter).Unlike BASIC or FORTRAN, however, APL hasdirect and powerful support for all the important mathematicalfunctions involving arrays or matrices (see array).APL has over 100 built-in operators, called “primitives.”With just one or two operators the programmer can performcomplex tasks such as extracting numeric or trigonometricfunctions, sorting numbers, or rearranging arraysand matrices. (Indeed, APL’s greatest power is in its abilityto manipulate matrices directly without resorting to explicitloops or the calling of external library functions.)To give a very simple example, the following line of APLcode:X [D X]sorts the array X. In most programming languages thiswould have to be done by coding a sorting algorithm in adozen or so lines of code using nested loops and temporaryvariables.However, APL has also been found by many programmersto have significant drawbacks. Because the languageuses Greek letters to stand for many operators, it requiresthe use of a special type font that was generally not availableon non-IBM systems. A dialect called J has been devised touse only standard ASCII characters, as well as both simplifyingand expanding the language. Many programmers findmathematical expressions in APL to be cryptic, makingprograms hard to maintain or revise. Nevertheless, APLSpecial Interest Groups in the major computing societiestestify to continuing interest in the language.Further ReadingACM Special Interest Group for APL and J Languages. Availableonline. URL: http://www.acm.org/sigapl/. Accessed April 12,2007.“APL Frequently Asked Questions.” Available from various sitesincluding URL: http://home.earthlink.net/~swsirlin/apl.faq.html. Accessed May 8, 2007.Gilman, Leonard, and Allen J. Rose. APL: An Interactive Approach.3rd ed. (reprint). Malabar, Fla.: Krieger, 1992.“Why APL?” Available online. URL: http://www.acm.org/sigapl/whyapl.htm. Accessed.Apple CorporationSince the beginning of personal computing, Apple has hadan impact out of proportion to its relatively modest marketshare. In a world generally dominated by IBM PC-compatiblemachines and the Microsoft DOS and Windows operatingsystems, Apple’s distinctive Macintosh computers andmore recent media products have carved out distinctivemarket spaces.Headquartered in Cupertino, California, Apple wascofounded in 1976 by Steve Jobs, Steve Wozniak, and RonaldWayne (the latter sold his interest shortly after incorporation).(See Jobs, Steve, and Wozniak, Steven.) Theirfirst product, the Apple I computer, was demonstrated tofellow microcomputer enthusiasts at the Homebrew ComputerClub. Although it aroused considerable interest, thehand-built Apple I was sold without a power supply, keyboard,case, or display. (Today it is an increasingly valuable“antique.”)Apple’s true entry into the personal computing marketcame in 1977 with the Apple II. Although it was moreexpensive than its main rivals from Radio Shack and Commodore,the Apple II was sleek, well constructed, and featuredbuilt-in color graphics. The motherboard includedseveral slots into which add-on boards (such as for printerinterfaces) could be inserted. Besides being attractive tohobbyists, however, the Apple II began to be taken seriouslyas a business machine when the first popular spreadsheetprogram, VisiCalc, was written for it.By 1981 more than 2 million Apple IIs (in several variations)had been sold, but IBM then came out with the IBMPC. The IBM machine had more memory and a somewhatmore powerful processor, but its real advantage was theaccess IBM had to the purchasing managers of corporateAmerica. The IBM PC and “clone” machines from othercompanies such as Compaq quickly displaced Apple asmarket leader.The MacintoshBy the early 1980s Steve Jobs had turned his attention todesigning a radically new personal computer. Using technologythat Jobs had observed at the Xerox Palo AltoResearch Center (PARC), the new machine would have afully graphical interface with icons and menus and the abilityto select items with a mouse. The first such machine,the Apple Lisa, came out in 1983. The machine cost almost$10,000, however, and proved a commercial failure.In 1984, however, Apple launched a much less expensiveversion (see Macintosh). Viewers of the 1984 SuperBowl saw a remarkable Apple commercial in which a femalefigure runs through a group of corporate drones (representingIBM) and smashes a screen. The “Mac” sold reasonablywell, particularly as it was given more processing power andmemory and was accompanied by new software that couldtake advantage of its capabilities. In particular, the Maccame to dominate the desktop publishing market, thanks toAdobe’s PageMaker program.In the 1990s Apple diversified the Macintosh line witha portable version (the PowerBook) that largely set thestandard for the modern laptop computer. By then Applehad acquired a reputation for stylish design and superiorease of use. However, the development of the rather similarWindows operating system by Microsoft (see MicrosoftWindows) as well as constantly dropping prices for IBMcompatiblehardware put increasing pressure on Apple andkept its market share limited. (Apple’s legal challenge to

applet 19Microsoft alleging misappropriation of intellectual propertyproved to be a protracted and costly failure.)Apple’s many Macintosh variants of the later 1990sproved confusing to consumers, and sales appeared to bogdown. The company was accused of trying to rely on anincreasingly nonexistent advantage, keeping prices high,and failing to innovate.However, in 1997 Steve Jobs, who had been forced out ofthe company in an earlier dispute, returned to the companyand brought with him some new ideas. In hardware therewas the iMac, a sleek all-in-one system with an unmistakableappearance that restored Apple to profitability in 1998.On the software side, Apple introduced new video-editingsoftware for home users and a thoroughly redesignedUNIX-based operating system (see OS X). In general, thenew incarnation of the Macintosh was promoted as the idealcompanion for a media-hungry generation.Consumer ElectronicsApple’s biggest splash in the new century, however, camenot in personal computing, but in the consumer electronicssector. Introduced in 2001, the Apple iPod has been phenomenallysuccessful, with 100 million units sold by 2006.The portable music player can hold thousands of songs andeasily fit into a pocket (see also music and video players,digital). Further, it was accompanied by an easy-touseinterface and an online music store (iTunes). (By early2006, more than a billion songs had been purchased anddownloaded from the service.) Although other types of portableMP3 players exist, it is the iPod that defined the genre(see also podcasting). Later versions of the iPod includethe ability to play videos.In 2005 Apple announced news that startled and perhapsdismayed many long-time users. The company announcedthat future Macintoshes would use the same Intel chipsemployed by Windows-based (“Wintel”) machines like theIBM PC and its descendants. The more powerful machineswould use dual processors (Intel Core Duo). Further, in2006 Apple released Boot Camp, a software package thatallows Intel-based Macs to run Windows XP. Jobs’s newstrategy seems to be to combine what he believed to be asuperior operating system and industrial design with industry-standardprocessors, offering the best user experienceand a very competitive cost. Apple’s earnings continuedstrong into the second half of 2006.In early 2007 Jobs electrified the crowd at the MacworldExpo by announcing that Apple was going to “reinventthe phone.” The product, called iPhone, is essentiallya combination of a video iPod and a full-featured Internet-enabledcell phone (see smartphone). Marketed byApple and AT&T (with the latter providing the phone service),the iPhone costs about twice as much as an iPod butincludes a higher-resolution 3.5-in. (diagonal) screen and a2 megapixel digital camera. The phone can connect to otherdevices (see Bluetooth) and access Internet services suchas Google Maps. The user controls the device with a newinterface called Multitouch.Apple also introduced another new media product, theApple TV (formerly the iTV), allowing music, photos, andvideo to be streamed wirelessly from a computer to an existingTV set. Apple reaffirmed its media-centered plans byannouncing that the company’s name would be changed fromApple Computer Corporation to simply Apple Corporation.In the last quarter of 2006 Apple earned a recordbreaking$1 billion in profit, bolstered mainly by verystrong sales of iPods and continuing good sales of Macintoshcomputers.Apple had strong Macintosh sales performance in thelatter part of 2007. The company has suggested that itspopular iPods and iPhones may be leading consumers toconsider buying a Mac for their next personal computer.Meanwhile, however, Apple has had to deal with questionsabout its backdating of stock options, a practice bywhich about 200 companies have, in effect, enabled executivesto purchase their stock at an artificially low price.Apple has cleared Jobs of culpability in an internal investigation,and in April 2007 the Securities and Exchange Commissionannounced that it would not take action against thecompany.Further ReadingCarlton, Jim. Apple: The Inside Story of Intrigue, Egomania and BusinessBlunders. New York: Random House, 1997.Deutschman, Alan. The Second Coming of Steve Jobs. New York:Broadway Books, 2000.Hertzfeld, Andy. Revolution in the Valley. Sebastapol, Calif.:O’Reilly, 2005.Kunkel, Paul. AppleDesign: The Work of the Apple Industrial DesignGroup. New York: Graphis, 1997.Levy, Steven. Insanely Great: The Life and Times of Macintosh, TheComputer that Changed Everything. New York: Penguin Books,2000.Linzmayer, Owen W. Apple Confidential 2.0: The Definitive Historyof the World’s Most Colorful Company. 2nd ed. San Francisco,Calif.: No Starch Press, 2004.appletAn applet is a small program that uses the resources of alarger program and usually provides customization or additionalfeatures. The term first appeared in the early 1990sin connection with Apple’s AppleScript scripting languagefor the Macintosh operating system. Today Java applets representthe most widespread use of this idea in Web development(see Java).Java applets are compiled to an intermediate representationcalled bytecode, and generally are run in a Webbrowser (see Web browser). Applets thus represent oneof several alternatives for interacting with users of Webpages beyond what can be accomplished using simple textmarkup (see html; for other approaches see Javascript,php, scripting languages, and ajax).An applet can be invoked by inserting a reference toits program code in the text of the Web page, using theHTML applet element or the now-preferred object element.Although the distinction between applets and scriptingcode (such as in PHP) is somewhat vague, applets usuallyrun in their own window or otherwise provide their owninterface, while scripting code is generally used to tailorthe behavior of separately created objects. Applets are also

20 application program interfacerather like plug-ins, but the latter are generally used toprovide a particular capability (such as the ability to reador play a particular kind of media file), and have a standardizedfacility for their installation and management (seeplug-in).Some common uses for applets include animations ofscientific or programming concepts for Web pages supportingclass curricula and for games designed to be playedusing Web browsers. Animation tools such as Flash andShockwave are often used for creating graphic applets.To prevent badly or maliciously written applets fromaffecting user files, applets such as Java applets are generallyrun within a restricted or “sandbox” environmentwhere, for example, they are not allowed to write or changefiles on disk.Further Reading“Java Applets.” Available online. URL: http://en.wikibooks.org/wiki/Java_Programming/Applets. Accessed April 10, 2007.McGuffin, Michael. “Java Applet Tutorial.” Available online. URL:http://www.realapplets.com/tutorial/. Accessed April 10, 2007.application program interface (API)In order for an application program to function, it mustinteract with the computer system in a variety of ways, suchas reading information from disk files, sending data to theprinter, and displaying text and graphics on the monitorscreen (see user interface). The program may need to findout whether a device is available or whether it can haveaccess to an additional portion of memory. In order to providethese and many other services, an operating systemsuch as Microsoft Windows includes an extensive applicationprogram interface (API). The API basically consists ofa variety of functions or procedures that an application programcan call upon, as well as data structures, constants, andvarious definitions needed to describe system resources.Applications programs use the API by including calls toroutines in a program library (see library, program andprocedures and functions). In Windows, “dynamic linklibraries” (DLLs) are used. For example, this simple functionputs a message box on the screen:MessageBox (0, “Program Initialization Failed!”,“Error!”, MB_ICONEXCLAMATION | MB_OK | MB_SYSTEMMODAL);In practice, the API for a major operating system such asWindows contains hundreds of functions, data structures,and definitions. In order to simplify learning to access thenecessary functions and to promote the writing of readablecode, compiler developers such as Microsoft and Borlandhave devised frameworks of C++ classes that package relatedfunctions together. For example, in the Microsoft FoundationClasses (MFC), a program generally begins by derivinga class representing the application’s basic characteristicsfrom the MFC class CWinApp. When the program wants todisplay a window, it derives it from the CWnd class, whichhas the functions common to all windows, dialog boxes,and controls. From CWnd is derived the specialized classModern software uses API calls to obtain interface objects such asdialog boxes from the operating system. Here the application callsthe CreateDialog API function. The operating system returns apointer (called a handle) that the application can now use to accessand manipulate the dialog.for each type of window: for example, CFrameWnd implementsa typical main application window, while CDialogwould be used for a dialog box. Thus in a framework suchas MFC or Borland’s OWL, the object-oriented concept ofencapsulation is used to bundle together objects and theirfunctions, while the concept of inheritance is used to relatethe generic object (such as a window) to specialized versionsthat have added functionality (see object-orientedprogramming and encapsulation inheritance).In recent years Microsoft has greatly extended the reachof its Windows API by providing many higher level functions(including user interface items, network communications,and data access) previously requiring separate software componentsor program libraries (see Microsoft.net).Programmers using languages such as Visual Basic cantake advantage of a further level of abstraction. Here thevarious kinds of windows, dialogs, and other controls areprovided as building blocks that the developer can insertinto a form designed on the screen, and then settings canbe made and code written as appropriate to control thebehavior of the objects when the program runs. While theprogrammer will not have as much direct control or flexibility,avoiding the need to master the API means that usefulprograms can be written more quickly.Further Reading“DevCentral Tutorials: MFC and Win32.” Available online. URL:http://devcentral.iftech.com/learning/tutorials/submfc.asp.Accessed April 12, 2007.

application service provider 21Petzold, Charles. Programming Windows: the Definitive Guide to theWin32 API. 5th ed. Redmond, Wash.: Microsoft Press, 1999.“Windows API Guide.” Available online. URL: http://www.vbapi.com/. Accessed April 12, 2007.application service provider (ASP)Traditionally, software applications such as office suites aresold as packages that are installed and reside on the user’scomputer. Starting in the mid-1990s, however, the idea ofoffering users access to software from a central repositoryattracted considerable interest. An application service provider(ASP) essentially rents access to software.Renting software rather than purchasing it outright hasseveral advantages. Since the software resides on the provider’sserver, there is no need to update numerous desktopinstallations every time a new version of the software (or a“patch” to fix some problem) is released. The need to shipphysical CDs or DVDs is also eliminated, as is the risk ofsoftware piracy (unauthorized copying). Users may be ableto more efficiently budget their software expenses, sincethey will not have to come up with large periodic expensesfor upgrades. The software provider, in turn, also receives asteady income stream rather than “surges” around the timeof each new software release.For traditional software manufacturers, the main concernis determining whether the revenue obtained by providingits software as a service (directly or through a thirdparty) is greater than what would have been obtained byselling the software to the same market. (It is also possibleto take a hybrid approach, where software is still sold, butusers are offered additional features online. Microsoft hasexperimented with this approach with its Microsoft OfficeLive and other products.)Renting software also has potential disadvantages. Theuser is dependent on the reliability of the provider’s serversand networking facilities. If the provider’s service is down,then the user’s work flow and even access to critical datamay be interrupted. Further, sensitive data that resides on aprovider’s system may be at risk from hackers or industrialspies. Finally, the user may not have as much control overthe deployment and integration of software as would beprovided by outright purchase.The ASP market was a hot topic in the late 1990s, andsome pundits predicted that the ASP model would eventuallysupplant the traditional retail channel for mainstreamsoftware. This did not happen, and more than a thousandASPs were among the casualties of the “dot-com crash” ofthe early 2000s. However, ASP activity has been steadier ifless spectacular in niche markets, where it offers more economicalaccess to expensive specialized software for applicationssuch as customer relationship management, supplychain management, and e-commerce related services—forexample, Salesforce.com. The growing importance of such“software as a service” business models can be seen inrecent offerings from traditional software companies suchas SAS. By 2004, worldwide spending for “on demand”software had exceeded $4 billion, and Gartner Researchhas predicted that in the second half of the decade abouta third of all software will be obtained as a service ratherthan purchased.Web-Based Applications and Free SoftwareBy that time a new type of application service providerhad become increasingly important. Rather than seekingto gain revenue by selling online access to software, thisnew kind of ASP provides the software for free. A strikingexample is Google Pack, a free software suite offered by thesearch giant (see Google). Google Pack includes a varietyof applications, including a photo organizer and search andmapping tools developed by Google, as well as third-partyprograms such as the Mozilla Firefox Web browser, Real-Player media player, the Skype Internet phone service (seevoip), and antivirus and antispyware programs. The softwareis integrated into the user’s Windows desktop, providingfast index and retrieval of files from the hard drive.(Critics have raised concerns about the potential violationof privacy or misuse of data, especially with regard to a“share across computers” feature that stores data about userfiles on Google’s servers.) America Online has also begun toprovide free access to software that was formerly availableonly to paid subscribers.This use of free software as a way to attract users toadvertising-based sites and services could pose a majorthreat to companies such as Microsoft that rely on softwareas their main source of revenue. In 2006 Google unveileda Google Docs & Spreadsheets, a program that allowsusers to create and share word-processing documents andspreadsheets over the Web. Such offerings, together withfree open-source software such as Open Office.org, mayforce traditional software companies to find a new modelfor their own offerings.Microsoft in turn has launched Office Live, a servicedesigned to provide small offices with a Web presence andproductivity tools. The free “basic” level of the service isadvertising supported, and expanded versions are availablefor a modest monthly fee. The program also has featuresthat are integrated with Office 2007, thus suggesting anattempt to use free or low-cost online services to add valueto the existing stand-alone product line.By 2008 the term cloud computing had become a popularway to describe software provided from a central Internetsite that could be accessed by the user through any formof computer and connection. An advantage touted for thisapproach is that the user need not be concerned with wheredata is stored or the need to make backups, which arehandled seamlessly.Further ReadingChen, Anne. “Office Live Makes Online Presence Known.” eWeek,November 2, 2006. Available online. URL: http://www.eweek.com/article2/0,1759,2050580,00.asp. Accessed May 22, 2007.Focacci, Luisa, Robert J. Mockler, and Marc E. Gartenfeld. ApplicationService Providers in Business. New York: Haworth,2005.Garretson, Rob. “The ASP Reincarnation: The Application ServiceProvider Name Dies Out, but the Concept Lives onamong Second-Generation Companies Offering Software asa service.” Network World, August 29, 2005. Available online.

22 application softwareURL: http://www.networkworld.com/research/2005/082905-asp.html. Accessed May 22, 2007.“Google Spreadsheets: The Soccer Mom’s Excel.” eWeek, June 6,2006. Available online. URL: http://www.eweek.com/article2/0,1759,1972740,00.asp.Accessed May 22, 2007.Schwartz, Ephraim. “Applications: SaaS Breaks Down the Wall:Hosted Applications Continue to Remove Enterprise Objections.”Infoworld, January 1, 2007. Available online. URL:http://www.infoworld.com/article/07/01/01/01FEtoyapps_1.html. Accessed May 22, 2007.application softwareApplication software consists of programs that enable computersto perform useful tasks, as opposed to programs thatare concerned with the operation of the computer itself (seeoperating system and systems programming). To mostusers, applications programs are the computer: They determinehow the user will accomplish tasks.The following table gives a selection of representativeapplications:Developing and Distributing ApplicationsApplications can be divided into three categories basedon how they are developed and distributed. Commercialapplications such as word processors, spreadsheets, andgeneral-purpose Database Management Systems (DBMS)are developed by companies specializing in such softwareand distributed to a variety of businesses and individualusers (see word processing, spreadsheet, and databasemanagement system). Niche or specialized applications(such as hospital billing systems) are designed for and marketedto a particular industry (see medical applicationsof computers). These programs tend to be much moreexpensive and usually include extensive technical support.Finally, in-house applications are developed by programmerswithin a business or other institution for their ownuse. Examples might include employee training aids or aWeb-based product catalog (although such applicationscould also be developed using commercial software such asmultimedia or database development tools).While each application area has its own needs and priorities,the discipline of software development (see softwareengineering and programming environment) isgenerally applicable to all major products. Software developerstry to improve speed of development as well as programreliability by using software development tools thatsimplify the writing and testing of computer code, as wellas the manipulation of graphics, sound, and other resourcesused by the program. An applications developer must alsohave a good understanding of the features and limitations ofthe relevant operating system. The developer of commercialsoftware must work closely with the marketing departmentto work out issues of feature selection, timing of releases,and anticipation of trends in software use (see marketingof software).Further Reading“Business Software Buyer’s Guide.” Available online. URL: http://businessweek.buyerzone.com/software/business_software/buyers_guide1.html. Accessed April 12, 2007.ZDnet Buyer’s Guide to Computer Applications. Available online.URL: http://www.zdnet.com/computershopper/edit/howtobuy/.Accessed April 12, 2007General Area Applications examplesBusiness Operations payroll, accounts receivable, specialized business software, general spreadsheets andinventory, marketingdatabasesEducation school management, curriculum attendance and grade book management, drill-and-practicereinforcement, reference aids, software for reading or arithmetic, CD or online encyclocurriculumexpansion orpedias, educational games or simulations, collaborativesupplementation, trainingand Web-based learning, corporate training programsEngineering design and manufacturing computer-aided design (CAD), computer-aided manufacturing(CAM)Entertainment games, music, and video desktop and console games, online games, digitized musicdistribution (MP3 files), streaming video (including movies)Government administration, law enforcement, tax collection, criminal records and field support for police,militarylegal citation databases, combat information and weaponscontrol systemsHealth Care hospital administration, health care hospital information and billing systems, medical recordsdeliverymanagement, medical imaging, computer-assisted treatmentor surgeryInternet and World web browser, search tools, browser and plug-in software for video and audio, searchWide Web e-commerce engines, e-commerce support and secure transactionsLibraries circulation, cataloging, reference automated book check-in systems, cataloging databases, CDor online bibliographic and full-text databasesOffice Operations e-mail, document creation e-mail clients, word processing, desktop publishingScience statistics, modeling, data analysis mathematical and statistical software, modeling of molecules,gene typing, weather forecasting

array 23application suiteAn application suite is a set of programs designed to beused together and marketed as a single package. For example,a typical office suite might include word processing,spreadsheet, database, personal information manager, ande-mail programs.While an operating system such as Microsoft Windowsprovides basic capabilities to move text and graphics fromone application to another (such as by cutting and pasting),an application suite such as Microsoft Office makes it easierto, for example, launch a Web browser from a link within aword processing document or embed a spreadsheet in thedocument. In addition to this “interoperability,” an applicationsuite generally offers a consistent set of commands andfeatures across the different applications, speeding up thelearning process. The use of the applications in one packagefrom one vendor simplifies technical support and upgrading.(The development of comparable applications suitesfor Linux is likely to increase that operating system’s acceptanceon the desktop.)Applications suites have some potential disadvantagesas compared to buying a separate program for eachapplication. The user is not necessarily getting the bestprogram in each application area, and he or she is alsoforced to pay for functionality that may not be needed ordesired. Due to their size and complexity, software suitesmay not run well on older computers. Despite these problems,software suites sell very well and are ubiquitous intoday’s office.(For a growing challenge to the traditional standalonesoftware suite, see application service provider.)Further ReadingVillarosa, Joseph. “How Suite It Is: One-Stop Shopping for SoftwareCan Save You Both Time and Money.” Available online.Forbes magazine online. URL: http://www.forbes.com/buyers/070.htm. Accessed April 12, 2007.arithmetic logic unit (ALU)The arithmetic logic unit is the part of a computer systemthat actually performs calculations and logical comparisonson data. It is part of the central processing unit (CPU), andin practice there may be separate and multiple arithmeticand logic units (see cpu).The ALU works by first retrieving a code that representsthe operation to be performed (such as ADD). The code alsospecifies the location from which the data is to be retrievedand to which the results of the operation are to be stored.(For example, addition of the data from memory to a numberalready stored in a special accumulator register withinthe CPU, with the result to be stored back into the accumulator.)The operation code can also include a specificationof the format of the data to be used (such as fixed or floating-pointnumbers)—the operation and format are oftencombined into the same code.In addition to arithmetic operations, the ALU can alsocarry out logical comparisons, such as bitwise operationsthat compare corresponding bits in two data words, correspondingto Boolean operators such as AND, OR, and XOR(see bitwise operations and Boolean operators).The data or operand specified in the operation code isretrieved as words of memory that represent numeric data,or indirectly, character data (see memory, numeric data,and characters and strings). Once the operation is performed,the result is stored (typically in a register in theCPU). Special codes are also stored in registers to indicatecharacteristics of the result (such as whether it is positive,negative, or zero). Other special conditions called exceptionsindicate a problem with the processing. Commonexceptions include overflow, where the result fills more bitsthan are available in the register, loss of precision (becausethere isn’t room to store the necessary number of decimalplaces), or an attempt to divide by zero. Exceptions aretypically indicated by setting a flag in the machine statusregister (see flag).The Big PictureDetailed knowledge of the structure and operation of theALU is not needed by most programmers. Programmerswho need to directly control the manipulation of data inthe ALU and CPU write programs in assembly language(see assembler) that specify the sequence of operations tobe performed. Generally only the lowest-level operationsinvolving the physical interface to hardware devices requirethis level of detail (see device driver). Modern compilerscan produce optimized machine code that is almost as efficientas directly-coded assembler. However, understandingthe architecture of the ALU and CPU for a particular chipcan help predict its advantages or disadvantages for variouskinds of operations.Further ReadingKleitz, William. Digital and Microprocessor Fundamentals: Theoryand Applications. 4th ed. Upper Saddle River, N.J.: PrenticeHall, 2002.Stokes, Jon. “Understanding the Microprocessor.” Ars Technica.Available online. URL: http://arstechnica.com/paedia/c/cpu/part-1/cpu1-1.html. Accessed May 22, 2007.arrayAn array stores a group of similar data items in consecutiveorder. Each item is an element of the array, and it can beretrieved using a subscript that specifies the item’s locationrelative to the first item. Thus in the C language, the statementint Scores (10);sets up an array called Scores, consisting of 10 integer values.The statementScores [5] = 93;stores the value 93 in array element number 5. One subtlety,however, is that in languages such as C, the first element ofthe array is [0], so [5] represents not the fifth but the sixthelement in Scores. (Many version of BASIC allow for settingeither 0 or 1 as the first element of arrays.)

24 arrayIn languages such as C that have pointers, an equivalentway to access an array is to declare a pointer and store theaddress of the first element in it (see pointers and indirection):int * ptr;ptr = &Scores [0];(See pointers and indirection.)Arrays are useful because they allow a program to workeasily with a group of data items without having to use separatelynamed variables. Typically, a program uses a loop totraverse an array, performing the same operation on eachelement in order (see loop). For example, to print the currentcontents of the Scores array, a C program could do thefollowing:int index;for (index = 0; i < 10; i++)printf (“Scores [%d] = %d \n”, index,Scores [index]);This program might print a table like this:Scores [0] = 22Scores [1] = 28Scores [2] = 36and so on. Using a pointer, a similar loop would incrementthe pointer to step to each element in turn.An array with a single subscript is said to have onedimension. Such arrays are often used for simple data lists,strings of characters, or vectors. Most languages also supportmultidimensional arrays. For example, a two-dimensionalarray can represent X and Y coordinates, as on ascreen display. Thus the number 16 stored at Colors[10][40]might represent the color of the point at X=10, Y=40 on a640 by 480 display. A matrix is also a two-dimensionalarray, and languages such as APL provide built-in supportfor mathematical operations on such arrays. A four-dimensionalarray might hold four test scores for each person.Some languages such as FORTRAN 90 allow for defining“slices” of an array. For example, in a 3 × 3 matrix, theexpression MAT(2:3, 1:3) references two 1 × 3 “slices” of thematrix array. Pascal allows defining a subrange, or portionof the subscripts of an array.Associative ArraysIt can be useful to explicitly associate pairs of data itemswithin an array. In an associative array each data elementhas an associated element called a key. Rather than usingsubscripts, data elements are retrieved by passing the keyto a hashing routine (see hashing). In the Perl language, forexample, an array of student names and scores might be setup like this:%Scores = (“Henderson” => 86, “Johnson” => 87, “Jackson”=> 92);The score for Johnson could later be retrieved using thereference:$Scores (“Johnson”)Associative arrays are handy in that they facilitate look-uptables or can serve as small databases. However, expandingthe array beyond its initial allocation requires rehashing allthe existing elements.A two-dimensional array can be visualized as a grid, with thearray subscripts indicating the row and column in which a particularvalue is stored. Here the value 4 is stored at the location(1,2), while the value at (2,0), which is 8, is assigned to N. Asshown, the actual computer memory is a one dimensional lineof successive locations. In most computer languages the array isstored row by row.Programming IssuesTo avoid error, any reference to an array must be withinits declared bounds. For example, in the earlier example,Scores[9] is the last element, and a reference to Scores[10]would be out of bounds. Attempting to reference an outof-boundsvalue gives an error message in some languagessuch as Pascal, but in others such as standard C and C++, itsimply retrieves whatever happens to be in that location inmemory.Another issue involves the allocation of memory for thearray. In a static array, such as that used in FORTRAN 77,the necessary storage is allocated before the program runs,and the amount of memory cannot be changed. Static arraysuse memory efficiently and reduce overhead, but are inflexible,since the programmer has to declare an array basedon the largest number of data items the program might becalled upon to handle. A dynamic array, however, can use aflexible structure to allocate memory (see heap). The programcan change the size of the array at any time while itis running. C and C++ programs can create dynamic arraysand allocate memory using special functions (malloc andfree in C) or operators (new and delete in C++).

art and the computer 25In the early days of microcomputer programming, arraystended to be used as an all-purpose data structure for storinginformation read from files. Today, since there are morestructured and flexible ways to store and retrieve such data,arrays are now mainly used for small sets of data (such aslook-up tables).Further ReadingJensen, Ted. “A Tutorial on Pointers and Arrays in C.” Availableonline. URL: http://pw2.netcom.com/~tjensen/ptr/pointers.htm. Accessed April 12, 2007.Sebesta, Robert W. Concepts of Programming Languages. 8th ed.Boston: Addison-Wesley, 2008.art and the computerWhile the artistic and technical temperaments are oftenviewed as opposites, the techniques of artists have alwaysshown an intimate awareness of technology, including thephysical characteristics of the artist’s tools and media. Thedevelopment of computer technology capable of generating,manipulating, displaying, or printing images has offered avariety of new tools for existing artistic traditions, as wellas entirely new media and approaches.Computer art began as an offshoot of research into imageprocessing or the simulation of visual phenomena, such asby researchers at Bell Labs in Murray Hill, New Jersey, duringthe 1960s. One of these researchers, A. Michael Noll,applied computers to the study of art history by simulatingtechniques used by painters Piet Mondrian and BridgetRiley in order to gain a better understanding of them. Inaddition to exploring existing realms of art, experimentersbegan to create a new genre of art, based on the ideas ofMax Bense, who coined the terms “artificial art” and “generativeesthetics.” Artists such as Manfred Mohr studiedcomputer science because they felt the computer could providethe tools for an esthetic strongly influenced by mathematicsand natural science. For example, Mohr’s P-159/A(1973) used mathematical algorithms and a plotting deviceto create a minimalistic yet rich composition of lines. Otherartists working in the minimalist, neoconstructivist, andconceptual art traditions found the computer to be a compellingtool for exploring the boundaries of form.By the 1980s, the development of personal computersmade digital image manipulation available to a much widergroup of people interested in artistic expression, includingthe more conventional realms of representational art andphotography. Programs such as Adobe Photoshop blend artand photography, making it possible to combine imagesfrom many sources and apply a variety of transformationsto them. The use of computer graphics algorithms makerealistic lighting, shadow, and fog effects possible to a muchgreater degree than their approximation in traditionalmedia. Fractals can create landscapes of infinite textureand complexity. The computer has thus become a standardtool for both “serious” and commercial artists.Artificial intelligence researchers have developed programsthat mimic the creativity of human artists. For example,a program called Aaron developed by Harold CohenAir, created by Lisa Yount with the popular image-editing programAdobe Photoshop, is part of a group of photocollages honoring theancient elements of earth, air, water, and fire. The “wings” in thecenter are actually the two halves of a mussel shell. (Lisa Yount)can adapt and extend existing styles of drawing and painting.Works by Aaron now hang in some of the world’s mostdistinguished art museums.An impressive display of the “state of the computer art”could be seen at a digital art exhibition that debuted inBoston at the SIGGRAPH 2006 conference. More than 150artists and researchers from 16 countries exhibited workand discussed its implications. Particularly interestingwere dynamic works that interacted with visitors and theenvironment, often blurring the distinction between digitalarts and robotics. In the future, sculptures may changewith the season, time of day, or the presence of people inthe room, and portraits may show moods or even conversewith viewers.Implications and ProspectsWhile traditional artistic styles and genres can be reproducedwith the aid of a computer, the computer has thepotential to change the basic paradigms of the visual arts.The representation of all elements in a composition in digitalform makes art fluid in a way that cannot be matched

26 artificial intelligenceby traditional media, where the artist is limited in the abilityto rework a painting or sculpture. Further, there is nohard-and-fast boundary between still image and animation,and the creation of art works that change interactivelyin response to their viewer becomes feasible. Sound, too,can be integrated with visual representation, in a way farmore sophisticated than that pioneered in the 1960s with“color organs” or laser shows. Indeed, the use of virtualreality technology makes it possible to create art that can beexperienced “from the inside,” fully immersively (see virtualreality). The use of the Internet opens the possibilityof huge collaborative works being shaped by participantsaround the world.The growth of computer art has not been without misgivings.Many artists continue to feel that the intimatephysical relationship between artist, paint, and canvas cannotbe matched by what is after all only an arrangement oflight on a flat screen. However, the profound influence ofthe computer on contemporary art is undeniable.Further ReadingComputer-Generated Visual Arts (Yahoo). Available online. URL:http://dir.yahoo.com/Arts/Visual_Arts/Computer_Generated/.Accessed April 13, 2007.Ashford, Janet. Arts and Crafts Computer: Using Your Computer asan Artist’s Tool. Berkeley, Calif.: Peachpit Press, 2001.Kurzweil Cyber Art Technologies homepage. Available online.URL: http://www.kurzweilcyberart.com/index.html. AccessedMay 22, 2007.Popper, Frank. Art of the Electronic Age. New York: Thames &Hudson, 1997.Rush, Michael. New Media in Late 20th-Century Art. New York:Thames & Hudson, 1999.SIGGRAPH 2006 Art Gallery. “Intersections.” Available online.URL: http://www.siggraph.org/s2006/main.php?f=conference&p=art. Accessed May 22, 2007.artificial intelligenceThe development of the modern digital computer followingWorld War II led naturally to the consideration of theultimate capabilities of what were soon dubbed “thinkingmachines” or “giant brains.” The ability to perform calculationsflawlessly and at superhuman speeds led someobservers to believe that it was only a matter of time beforethe intelligence of computers would surpass human levels.This belief would be reinforced over the years by the developmentof computer programs that could play chess withincreasing skill, culminating in the match victory of IBM’sDeep Blue over world champion Garry Kasparov in 1997.(See chess and computers.)However, the quest for artificial intelligence would facea number of enduring challenges, the first of which is alack of agreement on the meaning of the term intelligence,particularly in relation to such seemingly different entitiesas humans and machines. While chess skill is considereda sign of intelligence in humans, the game is deterministicin that optimum moves can be calculated systematically,limited only by the processing capacity of the computer.Human chess masters use a combination of pattern recognition,general principles, and selective calculation to comeup with their moves. In what sense could a chess-playingcomputer that mechanically evaluates millions of positionsbe said to “think” in the way humans do? Similarly, computerscan be provided with sets of rules that can be used tomanipulate virtual building blocks, carry on conversations,and even write poetry. While all these activities can be perceivedby a human observer as being intelligent and evencreative, nothing can truly be said about what the computermight be said to be experiencing.In 1950, computer pioneer Alan M. Turing suggesteda more productive approach to evaluating claims of artificialintelligence in what became known as the Turing test(see Turing, Alan). Basically, the test involves having ahuman interact with an “entity” under conditions where heor she does not know whether the entity is a computer oranother human being. If the human observer, after engagingin teletyped “conversation” cannot reliably determinethe identity of the other party, the computer can be said tohave passed the Turing test. The idea behind this approachis that rather than attempting to precisely and exhaustivelydefine intelligence, we will engage human experience andintuition about what intelligent behavior is like. If a computercan successfully imitate such behavior, then it at leastmay become problematic to say that it is not intelligent.Computer programs have been able to pass the Turingtest to a limited extent. For example, a program calledELIZA written by Joseph Weizenbaum can carry out whatappears to be a responsive conversation on themes chosenby the interlocutor. It does so by rephrasing statementsor providing generalizations in the way that a nondirectivepsychotherapist might. But while ELIZA and similarprograms have sometimes been able to fool human interlocutors,an in-depth probing by the humans has alwaysmanaged to uncover the mechanical nature of the response.Although passing the Turing test could be consideredevidence for intelligence, the question of whether a computermight have consciousness (or awareness of self) inthe sense that humans experience it might be impossible toanswer. In practice, researchers have had to confine themselvesto producing (or simulating) intelligent behavior, andthey have had considerable success in a variety of areas.Top-Down ApproachesThe broad question of a strategy for developing artificialintelligence crystallized at a conference held in 1956 at DartmouthCollege. Four researchers can be said to be foundersof the field: Marvin Minsky (founder of the AI Laboratory atMIT), John McCarthy (at MIT and later, Stanford), and HerbertSimon and Allen Newell (developers of a mathematicalproblem-solving program called Logic Theorist at the RandCorporation, who later founded the AI Laboratory at CarnegieMellon University). The 1950s and 1960s were a timeof rapid gains and high optimism about the future of AI (seeMinsky, Marvin and Mccarthy, John).Most early attempts at AI involved trying to specify rulesthat, together with properly organized data, can enable themachine to draw logical conclusions. In a production systemthe machine has information about “states” (situations) plusrules for moving from one state to another—and ultimately,

artificial intelligence 27to the “goal state.” A properly implemented production systemcannot only solve problems, it can give an explanationof its reasoning in the form of a chain of rules that wereapplied.The program SHRDLU, developed by Marvin Minsky’steam at MIT, demonstrated that within a simplified “microworld”of geometric shapes a program can solve problemsand learn new facts about the world. Minsky later developeda more generalized approach called “frames” to provide thecomputer with an organized database of knowledge aboutthe world comparable to that which a human child assimilatesthrough daily life. Thus, a program with the appropriateframes can act as though it understands a story abouttwo people in a restaurant because it “knows” basic factssuch as that people go to a restaurant to eat, the meal iscooked for them, someone pays for the meal, and so on.While promising, the frames approach seemed to founderbecause of the sheer number of facts and relationshipsneeded for a comprehensive understanding of the world.During the 1970s and 1980s, however, expert systems weredeveloped that could carry out complex tasks such as determiningthe appropriate treatment for infections (MYCIN)and analysis of molecules (DENDRAL). Expert systemscombined rules of inference with specialized databases offacts and relationships. Expert systems have thus been ableto encapsulate the knowledge of human experts and make itavailable in the field (see expert systems and knowledgerepresentation).The most elaborate version of the frames approach hasbeen a project called Cyc (short for “encyclopedia”), developedby Douglas Lenat. This project is now in its thirddecade and has codified millions of assertions about theworld, grouping them into semantic networks that representdozens of broad areas of human knowledge. If successful,the Cyc database could be applied in many differentdomains, including such applications as automatic analysisand summary of news stories.Bottom-Up ApproachesSeveral “bottom-up” approaches to AI were developed inan attempt to create machines that could learn in a morehumanlike way. The one that has gained the most practicalsuccess is the neural network, which attempts toemulate the operation of the neurons in the human brain.Researchers believe that in the human brain perceptions orthe acquisition of knowledge leads to the reinforcement ofparticular neurons and neural paths, improving the brain’sability to perform tasks. In the artificial neural network alarge number of independent processors attempt to performa task. Those that succeed are reinforced or “weighted,”while those that fail may be negatively weighted. This leadsto a gradual improvement in the overall ability of the systemto perform a task such as sorting numbers or recognizingpatterns (see neural network).Since the 1950s, some researchers have suggested thatcomputer programs or robots be designed to interact withtheir environment and learn from it in the way that humaninfants do. Rodney Brooks and Cynthia Breazeal at MIThave created robots with a layered architecture that includesmotor, sensory, representational, and decision-making elements.Each level reacts to its inputs and sends informationto the next higher level. The robot Cog and its descendantKismet often behaved in unexpected ways, generating complexresponses that are emergent rather than specificallyprogrammed.The approach characterized as “artificial life” adds agenetic component in which the successful componentspass on program code “genes” to their offspring. Thus, thepower of evolution through natural selection is simulated,leading to the emergence of more effective systems (seeartificial life and genetic algorithms).In general the top-down approaches have been moresuccessful in performing specialized tasks, but the bottomupapproaches may have greater general application, as wellas leading to cross-fertilization between the fields of artificialintelligence, cognitive psychology, and research intohuman brain function.Application AreasWhile powerful artificial intelligence is not yet ubiquitousin everyday computing, AI principles are being successfullyused in a number of application areas. These areas, whichare all covered separately in this book, include• devising ways of capturing and representing knowledge,making it accessible to systems for diagnosis andanalysis in fields such as medicine and chemistry (seeknowledge representation and expert systems)• creating systems that can converse in ordinary languagefor querying databases, responding to customerservice calls, or other routine interactions (see naturallanguage processing)• enabling robots to not only see but also “understand”objects in a scene and their relationships (see computervision and robotics)• improving systems for voice and face recognition, aswell as sophisticated data mining and analysis (seespeech recognition and synthesis, biometrics,and data mining)• developing software that can operate autonomously,carrying out assignments such as searching for andevaluating competing offerings of merchandise (seesoftware agent)ProspectsThe field of AI has been characterized by successive wavesof interest in various approaches, and ambitious projectshave often failed. However, expert systems and, to a lesserextent, neural networks have become the basis for viableproducts. Robotics and computer vision offer a significantpotential payoff in industrial and military applications. Thecreation of software agents to help users navigate the complexityof the Internet is now of great commercial interest.The growth of AI has turned out to be a steeper and morecomplex path than originally anticipated. One view suggestssteady progress. Another, shared by science fiction

28 artificial lifewriters such as Vernor Vinge, suggests a breakthrough, perhapsarising from artificial life research, might somedaycreate a true—but truly alien—intelligence (see singularity,technological).Further ReadingAmerican Association for Artificial Intelligence. “Welcome to AITopics.” Available online. URL: http://www.aaai.org/Pathfinder/html/welcome.html. Accessed April 13, 2007.“An Introduction to the Science of Artificial Intelligence.” Availableonline. URL: http://library.thinkquest.org/2705/. AccessedApril 13, 2007.Feigenbaum, E. A. and J. Feldman, eds. Computers and Thought.New York: McGraw-Hill, 1963.Henderson, Harry. Artificial Intelligence: Mirrors for the Mind. NewYork: Facts On File, 2007.Jain, Sanjay, et al. Systems that Learn: An Introduction to LearningTheory. 2nd ed. Cambridge, Mass: MIT Press, 1999.Kurzweil, Ray. The Age of Spiritual Machines: When ComputersExceed Human Intelligence. New York: Viking, 1999.McCorduck, Pamela. Machines Who Think. 25th Anniversaryupdate. Notick, Mass.: A. K. Peters, 2004.Shapiro, Stuart C. Encyclopedia of Artificial Intelligence. 2nd ed.New York: Wiley, 1992.artificial life (AL)This is an emerging field that attempts to simulate thebehavior of living things in the realm of computers androbotics. The field overlaps artificial intelligence (AI) sinceintelligent behavior is an aspect of living things. The designof a self-reproducing mechanism by John von Neumann inthe mid-1960s was the first model of artificial life (see vonNeumann, John). The field was expanded by the developmentof cellular automata as typified in John Conway’sGame of Life in the 1970s, which demonstrated how simplecomponents interacting according to a few specific rulescould generate complex emergent patterns. A program byCraig Reynolds uses this principle to model the flockingbehavior of simulated birds, called “boids” (see cellularautomata).The development of genetic algorithms by John Hollandadded selection and evolution to the act of reproduction.This approach typically involves the setting up of numeroussmall programs with slightly varying code, and having themattempt a task such as sorting data or recognizing patterns.Those programs that prove most “fit” at accomplishing thetask are allowed to survive and reproduce. In the act ofreproduction, biological mechanisms such as genetic mutationand crossover are allowed to intervene (see geneticalgorithms). A rather similar approach is found in theneural network, where those nodes that succeed better atthe task are given greater “weight” in creating a compositesolution to the problem (see neural network).A more challenging but interesting approach to AL is tocreate actual robotic “organisms” that navigate in the physicalrather than the virtual world. Roboticist Hans Moravecof the Stanford AI Laboratory and other researchers havebuilt robots that can deal with unexpected obstacles byimprovisation, much as people do, thanks to layers of softwarethat process perceptions, fit them to a model of theworld, and make plans based on goals. But such robots,built as full-blown designs, share few of the characteristicsof artificial life. As with AI, the bottom-up approach offersa different strategy that has been called “fast, cheap, andout of control”—the production of numerous small, simple,insectlike robots that have only simple behaviors, but arepotentially capable of interacting in surprising ways. If ameaningful genetic and reproductive mechanism can beincluded in such robots, the result would be much closer totrue artificial life (see robotics).The philosophical implications arising from the possibledevelopment of true artificial life are similar to thoseinvolved with “strong AI.” Human beings are used to viewingthemselves as the pinnacle of a hierarchy of intelligenceand creativity. However, artificial life with the capabilityof rapid evolution might quickly outstrip human capabilities,perhaps leading to a world like that portrayed by sciencefiction writer Gregory Benford, where flesh-and-bloodhumans become a marginalized remnant population.Further Reading“ALife Online 2.0.” Available online. URL: http://alife.org/.Accessed April 13, 2007.“Karl Sims Retrospective.” Available online. URL: http://www.biota.org/ksims/. Accessed April 13, 2007.Langton, Christopher G., ed. Artificial Life: an Overview. Cambridge,Mass.: MIT Press, 1995.Levy, Stephen. Artificial Life: the Quest for a New Creation. NewYork: Pantheon Books, 1992.Tierra homepage. Available online. URL: http://www.his.atr.jp/çray/tierra. Accessed.ASP See application service provider.assemblerAll computers at bottom consist of circuits that can performa repertoire of mathematical or logical operations. The earliestcomputers were programmed by setting switches foroperations and manually entering numbers in working storage,or memory. A major advance in the flexibility of computerscame with the idea of stored programs, where a set ofinstructions could be read in and held in the machine in thesame way as other data. These instructions were in machinelanguage, consisting of numbers representing instructions(operations to be performed) and other numbers representingthe address of data to be manipulated (or an addresscontaining the address of the data, called indirect addressing—seeaddressing). Operations include basic arithmetic(such as addition), the movement of data between storage(memory) and special processor locations called registers,and the movement of data from an input device (such as acard reader) and an output device (such as a printer).Writing programs in machine code is obviously atedious and error-prone process, since each operation mustbe specified using a particular numeric instruction codetogether with the actual addresses of the data to be used. Itsoon became clear, however, that the computer could itselfbe used to keep track of binary codes and actual addresses,

asynchronous JavaScript and XML 29In this assembly language example, the “define byte” (.db) directive is used to assign one memory byte to each of the symbolic names (variables)firstnum, secondnum, and total. The two mov commands then load 2 and 3 into firstnum and secondnum, respectively. Firstnum isthen loaded into the processor’s accumulator (a), and secondnum is then added to it. Finally, the sum is moved into the memory locationlabeled total.allowing the programmer to use more human-friendlynames for instructions and data variables. The programthat translates between symbolic language and machinelanguage is the assembler.With a symbolic assembler, the programmer can givenames to data locations. Thus, instead of saying (and havingto remember) that the quantity Total will be in location&H100, the program can simply define a two-byte chunk ofmemory and call it Total:Total DBThe assembler will take care of assigning a physical memorylocation and, when instructed, retrieving or storing thedata in it.Most assemblers also have macro capability. This meansthat the programmer can write a set of instructions (a procedure)and give it a name. Whenever that name is used inthe program, the assembler will replace it with the actualcode for the procedure and plug in whatever variables arespecified as operands (see macro).ApplicationsIn the mainframe world of the 1950s, the development ofassembly languages represented an important first steptoward symbolic programming; higher-level languages suchas FORTRAN and COBOL were developed so that programmerscould express instructions in language that was morelike mathematics and English respectively. High-level languagesoffered greater ease of programming and sourcecode that was easier to understand (and thus to maintain).Gradually, assembly language was reserved for systems programmingand other situations where efficiency or the needto access some particular hardware capability required theexact specification of processing (see systems programmingand device driver).During the 1970s and early 1980s, the same evolutiontook place in microcomputing. The first microcomputerstypically had only a small amount of memory (perhaps8–64K), not enough to compile significant programs in ahigh-level language (with the partial exception of some versionsof BASIC). Applications such as graphics and games inparticular were written in assembly language for speed. Asavailable memory soared into the hundreds of kilobytes andthen megabytes, however, high level languages such as Cand C++ became practicable, and assembly language beganto be relegated to systems programming, including devicedrivers and other programs that had to interact directlywith the hardware.While many people learning programming today receivelittle or no exposure to assembly language, some understandingof this detailed level of programming is still usefulbecause it illustrates fundamentals of computer architectureand operation.Further ReadingAbel, Peter. IBM PC Assembly Language and Programming. 5th ed.Upper Saddle River, N.J.: Prentice Hall, 2001.Duntemann, Jeff. Assembly Language Step by Step: Programmingwith DOS and Linux. 2nd ed. New York: Wiley, 2000.Miller, Karen. An Assembly Language Introduction to ComputerArchitecture Using the Intel Pentium. New York: Oxford UniversityPress, 1999.asynchronous JavaScript and XML See ajax.

30 Atanasoff, John VincentAtanasoff, John Vincent(1903–1995)AmericanComputer EngineerAccording to a federal court it was John Atanasoff, not JohnMauchly and Presper Eckert, who built the first digital computer.At any rate the “ABC” or Atanasoff-Berry computer representeda pioneering achievement in the use of binary logic circuits forcomputation. (Iowa State University)John V. Atanasoff is considered by many historians to bethe inventor of the modern electronic computer. He wasborn October 4, 1903, in Hamilton, New York. As a youngman, Atanasoff showed considerable interest in and a talentfor electronics. His academic background (B.S. in electricalengineering, Florida State University, 1925; M.S. in mathematics,Iowa State College, 1926; and Ph.D. in experimentalphysics, University of Wisconsin, 1930) well equipped himfor the design of computing devices. He taught mathematicsand physics at Iowa State until 1942, and during thattime, he conceived the idea of a fully electronic calculatingmachine that would use vacuum tubes for its arithmetic circuitsand would store binary numbers on a rotating drummemory that used high and low charges on capacitors.Atanasoff and his assistant Clifford E. Berry built a successfulcomputer called ABC (Atanasoff-Berry computer)using this design in 1942. (By that time he had taken a wartimeresearch position at the Naval Ordnance Laboratory inWashington, D.C.)The ABC was a special-purpose machine designed forsolving up to 29 simultaneous linear equations using analgorithm based on Gaussian elimination to eliminatea specified variable from a pair of equations. Because ofinherent unreliability in the system that punched cards tohold the many intermediate results needed in such calculations,the system was limited in practice to solving sets offive or fewer equations.Despite its limitations, the ABC’s design proved the feasibilityof fully electronic computing, and similar vacuumtube switching and regenerative memory circuits weresoon adopted in designing the ENIAC and EDVAC, whichunlike the ABC, were general-purpose electronic computers.Equally important was Atanasoff’s use of capacitors to storedata in memory electronically: The descendent of his capacitorscan be found in the DRAM chips in today’s computers.When Atanasoff returned to Iowa State in 1948, he discoveredthat the ABC computer had been dismantled tomake room for another project. Only a single memory drumand a logic unit survived. Iowa State granted him a fullprofessorship and the chairmanship of the physics department,but he never returned to that institution. Instead, hefounded the Ordnance Engineering Corporation in 1952,which grew to a 100-person workforce before he sold thefirm to Aerojet General in 1956. He then served as a vicepresident at Aerojet until 1961.Atanasoff then semi-retired, devoting his time to a varietyof technical interests (he had more than 30 patents tohis name by the time of his death). However, when SperryUnivac (owner of Eckert and Mauchly’s computer patents)began demanding license fees from competitors in the mid-1960s, the head lawyer for one of these competitors, Honeywell,found out about Atanasoff’s work on the ABC andenlisted his aid as a witness in an attempt to overturn thepatents. After prolonged litigation, Judge Earl Richard Larsonruled in 1973 that the two commercial computing pioneershad learned key ideas from Atanasoff’s apparatus andwritings and that their patent was invalid because of this“prior art.”Atanasoff received numerous awards for his work for theNavy on acoustics and for his pioneering computer work.These awards included the IEEE Computer Pioneer Award(1984) and the National Medal of Technology (1990). Inaddition, he had both a hall at Iowa State University andan asteroid (3546-Atanasoff) named in his honor. JohnAtanasoff died on June 15, 1995, in Monrovia, Maryland.Further ReadingBurks, A. R., and A. W. Burks. The First Electronic Computer: theAtanasoff Story. Ann Arbor, Mich: University of MichiganPress, 1988.Lee, J. A. N. Computer Pioneers. Los Alamitos, Calif.: IEEE ComputerSociety Press, 1995.“Reconstruction of the Atanasoff-Berry Computer (ABC).” Availableonline. URL: http://www.scl.ameslab.gov/ABC/ABC.html. Accessed April 13, 2007.

authentication 31auctions, onlineBy the late 1990s, millions of computer users had discovereda new way to buy and sell an immense variety of itemsranging from traditional collectibles to the exotic (such as aworking German Enigma encoding machine).Since its founding in 1995, leading auction site eBay hasgrown to 78 million users in mid-2006, with revenue ofabout $7.6 billion in 2007 (see eBay). (Two other e-commercegiants, Amazon.com and Yahoo!, also entered theonline auction market, but with much more modest results.)ProceduresOnline auctions differ from traditional auctions in severalways. Traditional auction firms generally charge the sellerand buyer a commission of around 10 percent of the sale or“hammer” price. Online auctions charge the buyer nothing,and the seller typically pays a fee of about 3–5 percent of theamount realized. Online auctions can charge much lowerfees because unlike traditional auctions, there is no liveauctioneer, no catalogs to produce, and little administration,since all payments pass from buyer to seller directly.An online auction is like a mail bid auction in that bidscan be posted at any time during the several days a typicalauction runs. A buyer specifies a maximum bid and ifhe or she becomes the current high bidder, the high bid isadjusted to a small increment over the next highest bid. Aswith a “live” auction, however, bidders can revise their bidsas many times as they wish until the close of the auction.An important difference between online and traditional liveauctions is that a traditional auction ends as soon as noone is willing to top the current high bid. With an onlineauction, the bidding ends at the posted ending time. Thishas led to a tactic known as “sniping,” where some bidderssubmit a bid just over the current high bid just before theauction ends, such that the previous high bidder has notime to respond.Future and ImplicationsOnline auctions have become very popular, and an increasingnumber of people run small businesses by selling itemsthrough auctions. The markets for traditional collectiblessuch as coins and stamps have been considerably affectedby online auctions. Knowledgeable buyers can often obtainitems for considerably less than a dealer would charge, orsell items for more than a dealer would pay. However, manyitems are overpriced compared to the normal market, andfaked or ill-described items can be a significant problem.Attempts to hold the auction service legally responsiblefor such items are met with the response that the auctionservice is simply a facilitator for the seller and buyer anddoes not play the role of traditional auctioneers who catalogitems and provide some assurance of authenticity. If courtsor regulators should decide that online auctions must bearthis responsibility, the cost of using the service may rise orthe variety of items that can be offered may be restricted.Further ReadingCohen, Adam. The Perfect Store: Inside eBay. Boston: Little, Brown,2002.Encell, Steve, and Si Dunn. The Everything Online Auctions Book:All You Need to Buy and Sell with Success—on eBay and Beyond.Avon, Mass.: Adams Publishing Group, 2006.Kovel, Ralph M., and Terry H. Kovel. Kovels’ Bid, Buy, and SellOnline: Basic Auction Information and Tricks of the Trade. NewYork: Three Rivers Press, 2001.auditing in data processingThe tremendous increase in the importance and extent ofinformation systems for all aspects of commerce and industryhas made it imperative that businesses be able to ensurethe accuracy and integrity of their accounting systems andcorporate databases. Errors can result in loss of revenueand even exposure to legal liability.Auditing involves the analysis of the security and accuracyof software and the procedures for using it. For example,sample data can be extracted using automated scriptsor other software tools and examined to determine whethercorrect and complete information is being entered into thesystem, and whether the reports on which managementrelies for decision making are accurate. Auditing is alsoneeded to confirm that data reported to regulatory agenciesmeets legal requirements.In addition to confirming the reliability of software andprocedures, auditors must necessarily also be concernedwith issues of security, since attacks or fraud involvingcomputer systems can threaten their integrity or reliability(see computer crime and security). The safeguarding ofcustomer privacy has also become a sensitive concern (seeprivacy in the digital age). To address such issues, theauditor must have a working knowledge of basic psychologyand human relations, particularly as they affect largeorganizations.Auditors recommend changes to procedures and practicesto minimize the vulnerability of the system to bothhuman and natural threats. The issues of backup andarchiving and disaster recovery must also be addressed(see backup and archive systems). As part accountantand part systems analyst, the information systems auditorrepresents a bridging of traditional practices and rapidlychanging technology.Further ReadingCannon, David L., Timothy S. Bergmann, and Brady Pamplin.CISA: Certified Information Systems Auditor Study Guide. Indianapolis:Wiley Publishing, 2006.Champlain, Jack. Auditing Information Systems. Hoboken, N.J.:Wiley, 2003.Information Systems Audit and Control Association. Availableonline. URL: http://www.isaca.org/. Accessed May 22, 2007.Pathak, Jagdish. Information Systems Auditing: An Evolving Agenda.New York: Springer-Verlag, 2005.authenticationThis process by which two parties in a communicationor transaction can assure each other of their identity is afundamental requirement for any transaction not involvingcash, such as the use of checks or credit or debit cards.(In practice, for many transactions, authentication is “one

32 authoring systemsway”—the seller needs to know the identity of the buyeror at least have some way of verifying the payment, but thebuyer need not confirm the identity of the seller—except,perhaps in order to assure proper recourse if somethingturns out to be wrong with the item purchased.)Traditionally, authentication involves paper-based identification(such as driver’s licenses) and the making andmatching of signatures. Since such identification is relativelyeasy to fake, there has been growing interest in theuse of characteristics such as voice, facial measurements,or the patterns of veins in the retina that can be matcheduniquely to individuals (see biometrics). Biometrics, however,requires the physical presence of the person before asuitable device, so it is primarily used for guarding entryinto high-security areas.Authentication in Online SystemsSince many transactions today involve automated systemsrather than face-to-face dealings, authentication systemsgenerally involve the sharing of information unique to theparties. The PIN used with ATM cards is a common example:It protects against the physical diversion of the card byrequiring information likely known only to the legitimateowner. In e-commerce, there is the additional problem ofsafeguarding sensitive information such as credit card numbersfrom electronic eavesdroppers or intruders. Here a systemis used by which information is encrypted before it istransmitted over the Internet. Encryption can also be usedto verify identity through a digital signature, where a messageis transformed using a “one-way function” such that it ishighly unlikely that a message from any other sender wouldhave the same encrypted form (see encryption). The mostwidespread system is public key cryptography, where eachperson has a public key (known to all interested parties) anda private key that is kept secret. Because of the mathematicalrelationship between these two keys, the reader of a messagecan verify the identity of the sender or creator.The choice of technology or protocol for authenticationdepends on the importance of the transaction, the vulnerabilityof information that needs to be protected, and theconsequences of failing to protect it. A Web site that is providingaccess to a free service in exchange for informationabout users will probably not require authentication beyondperhaps a simple user/password pair. An online store, on theother hand, needs to provide a secure transaction environmentboth to prevent losses and to reassure potential customersthat shopping online does not pose an unacceptable risk.Authentication ultimately depends on a combinationof technological and social systems. For example, cryptographickeys or “digital certificates” can be deposited witha trusted third party such that a user has reason to believethat a business is who it says it is.Further ReadingRatha, Nalini, and Ruud Bolie, eds. Automatic Fingerprint RecognitionSystems. New York: Springer-Verlag, 2004.Smith, Richard E., and Paul Reid. User Authentication Systems andRole-Based Security. Upper Saddle River, N.J.: Pearson CustomPublishing, 2004.Tung, Brian. Kerberos: A Network Authentication System. Reading,Mass.: Addison-Wesley, 1999.authoring systemsMultimedia presentations such as computer-based-training(CBT) modules are widely used in the corporate and educationalarenas. Programming such a presentation in a highlevellanguage such as C++ (or even Visual Basic) involveswriting code for the detailed arrangement and control ofgraphics, animation, sound, and user interaction. Authoringsystems offer an alternative way to develop presentations orcourses. The developer specifies the sequence of graphics,sound, and other events, and the authoring system generatesa finished program based on those specifications.Authoring systems can use a variety of models for organizingpresentations. Some use a scripting language thatspecifies the objects to be used and the actions to be performed(see scripting languages). A scripting languageuses many of the same features as a high-level programminglanguage, including the definition of variables and theuse of control structures (decision statements and loops).Programs such as the once ubiquitous Hypercard (for theMacintosh) and Asymetrix Toolbook for Windows organizepresentations into segments called “cards,” with instructionsfleshed out in a scripting language.As an alternative, many modern authoring systemssuch as Discovery Systems’ CourseBuilder use a graphicalapproach to organizing a presentation. The various objects(such as graphics) to be used are represented by icons, andthe icons are connected with “flow lines” that describethe sequence of actions, serving the same purpose as controlstructures in programming languages. This “iconic”type of authoring system is easiest for less experiencedprogrammers to use and makes the creation of small presentationsfast and easy. Such systems may become moredifficult to use for lengthy presentations (due to the numberof symbols and connectors involved), and speed of thefinished program can be a problem. Other popular modelsfor organizing presentations include the “timeline” ofMacromedia Flash, which breaks the presentation into“movies” and specifies actions for each frame, as well asproviding multiple layers to facilitate animation. With themigration of many presentations to the Internet, the abilityof authoring systems to generate HTML (or DHTML)code is also important.Further ReadingMakedon, Fillia, and Samuel A. Rebelsky, ed. Electronic MultimediaPublishing: Enabling Technologies and Authoring Issues. Boston:Kluwer Academic, 1998.“Multimedia Authoring Systems FAQ.” Available online. URL:http://fags.cs.uu.nl/na-dir/multimedia/authoring-systems/part1.html. Accessed August 8, 2007.Murray, T. “Authoring Intelligent Tutoring Systems: An analysis ofthe state of the art.” International J. of Artificial Intelligence inEducation 10 (1999): 98–129.Wilhelm, Jeffrey D., Paul Friedman, and Julie Erickson. Hyperlearning:where Projects, Inquiry, and Technology Meet. York,Me.: Stenhouse, 1998.

awk 33automatic programmingFrom the beginning of the computer age, computer scientistshave grappled with the fact that writing programsin any computer language, even relatively high-level onessuch as FORTRAN or C, requires painstaking attention todetail. While language developers have responded to thischallenge by trying to create more “programmer friendly”languages such as COBOL with its English-like syntax,another approach is to use the capabilities of the computerto automate the task of programming itself. It is truethat any high-level language compiler does this to someextent (by translating program statements into the underlyingmachine instructions), but the more ambitious taskis to create a system where the programmer would specifythe problem and the system would generate the high-levellanguage code. In other words, the task of programming,which had already been abstracted from the machine codelevel to the assembler level and from that level to the highlevellanguage, would be abstracted a step further.During the 1950s, researchers began to apply artificialintelligence principles to automate the solving of mathematicalproblems (see artificial intelligence). For example,in the 1950s Anthony Hoare introduced the definition ofpreconditions and postconditions to specify the states ofthe machine as it proceeds toward an end state (the solutionof the problem). The program Logic Theorist demonstratedthat a computer could use a formal logical calculus to solveproblems from a set of conditions or axioms. Techniquessuch as deductive synthesis (reasoning from a set of programmedprinciples to a solution) and transformation (stepby-steprules for converting statements in a specificationlanguage into the target programming language) allowed forthe creation of automated programming systems, primarilyin mathematical and scientific fields (see also prolog).The development of the expert system (combining aknowledge base and inference rules) offered yet anotherroute toward automated programming (see expert systems).Herbert Simon’s 1963 Heuristic Compiler was anearly demonstration of this approach.ApplicationsSince many business applications are relatively simple inlogical structure, practical automatic principles have beenused in developing application generators that can create,for example, a database management system given adescription of the data structures and the required reports.While some systems output code in a language such as C,others generate scripts to be run by the database managementsoftware itself (for example, Microsoft Access).To simplify the understanding and specification of problems,a visual interface is often used for setting up the applicationrequirements. Onscreen objects can represent itemssuch as data files and records, and arrows or other connectinglinks can be dragged to indicate data relationships.The line between automated program generators andmodern software development environments is blurry. Aprogramming environment such as Visual Basic encapsulatesa great deal of functionality in objects called controls,which can represent menus, lists, buttons, text input boxes,and other features of the Windows interface, as well asother functionalities (such as a Web browser). The VisualBasic programmer can design an application by assemblingthe appropriate interface objects and processing tools, setproperties (characteristics), and write whatever additionalcode is necessary. While not completely automating programming,much of the same effect can be achieved.Further ReadingAndrews, James H. Logic Programming: Operational Semantics andProof Theory. New York: Cambridge University Press, 1992.“Automatic Programming Server.” Available online. URL: http://www.cs.utexas.edu/users/novak/cgi/apserver.cgi. AccessedApril 14, 2007.“Programming and Problem Solving by Connecting Diagrams.”Available online. URL: http://www.cs.utexas.edu/users/novak/cgi/vipdemo.cgi. Accessed April 14, 2007.Tahid, Walid, ed. Semantics, Applications and Implementation ofProgram Generation. New York: Springer-Verlag, 2000.awkThis is a scripting language developed under the UNIXoperating system (see scripting languages) by Alfred V.Aho, Brian W. Kernighan, and Peter J. Weinberger in 1977.(The name is an acronym from their last initials.) The languagebuilds upon many of the pattern matching utilitiesof the operating system and is designed primarily for theextraction and reporting of data from files. A number ofvariants of awk have been developed for other operatingsystems such as DOS.As with other scripting languages, an awk program consistsof a series of commands read from a file by the awkinterpreter. For example the following UNIX commandline:awk -f MyProgram > Reportreads awk statements from the file MyProgram into theawk interpreter and sends the program’s output to the fileReport.Language FeaturesAn awk statement consists of a pattern to match and anaction to be taken with the result (although the pattern canbe omitted if not needed). Here are some examples:{print $1} # prints the first field of every# line of input (since no pattern# is specified)/debit/ {print $2} # print the second field of# every line that contains the# word “debit”if ( Code == 2 ) # if Code equals 2,print $3 # print third field# of each linePattern matching uses a variety of regular expressions familiarto UNIX users. Actions can be specified using a limitedbut adequate assortment of control structures similar to

34 awkthose found in C. There are also built-in variables (includingcounters for the number of lines and fields), arithmetic functions,useful string functions for extracting text from fields,and arithmetic and relational operators. Formatting of outputcan be accomplished through the versatile (but somewhatcryptic) print function familiar to C programmers.Awk became popular for extracting reports from datafiles and simple databases on UNIX systems. For moresophisticated applications it has been supplanted by Perl,which offers a larger repertoire of database-oriented features(see Perl).Further ReadingAho, Alfred V., Brian Kernighan, and Peter J. Weinberger. TheAwk Programming Language. Reading, Mass.: Addison-Wesley,1998.Goebel, Greg. “An Awk Primer.” Available online. URL: http://www.vectorsite.net/tsawk.html. Accessed May 22, 2007.

BBabbage, Charles(1791–1871)BritishMathematician, InventorCharles Babbage made wide-ranging applications of mathematicsto a variety of fields including economics, socialstatistics, and the operation of railroads and lighthouses.Babbage is best known, however, for having conceptualizedthe key elements of the general-purpose computer about acentury before the dawn of electronic digital computing.As a student at Trinity College, Cambridge, Babbagewas already making contributions to the reform of calculus,championing new European methods over the Newtonianapproach still clung to by British mathematicians.But Babbage’s interests were shifting from the theoreticalto the practical. Britain’s growing industrialization as wellas its worldwide interests increasingly demanded accuratenumeric tables for navigation, actuarial statistics, interestrates, and engineering parameters. All tables had to behand-calculated, a long process that inevitably introducednumerous errors. Babbage began to consider the possibilitythat the same mechanization that was revolutionizingindustries such as weaving could be turned to the automaticcalculation of numeric tables.Starting in 1820, Babbage began to build a mechanicalcalculator called the difference engine. This machineused series of gears to accumulate additions and subtractions(using the “method of differences”) to generatetables. His small demonstration model worked well,so Babbage undertook the full-scale “Difference EngineNumber One,” a machine that would have about 25,000moving parts and would be able to calculate up to 20 decimalplaces. Unfortunately, Babbage was unable, despitefinancial support from the British government, to overcomethe difficulties inherent in creating a mechanicaldevice of such complexity with the available machiningtechnology.Undaunted, Babbage turned in the 1830s to a new designthat he called the Analytical Engine. Unlike the DifferenceEngine, the new machine was to be programmable usinginstructions read in from a series of punch cards (as in theJacquard loom). A second set of cards would contain thevariables, which would be loaded into the “store”—a seriesof wheels corresponding to memory in a modern computer.Under control of the instruction cards, numbers could bemoved between the store and the “mill” (corresponding to amodern CPU) and the results of calculations could be sentto a printing device.Collaborating with Ada Lovelace (who translated his lecturetranscripts by L. F. Menebrea) Babbage wrote a seriesof papers and notes that explained the workings of the proposedmachine, including a series of “diagrams” (programs)for performing various sorts of calculations.Building the Analytical Engine would have been a farmore ambitious task than the special-purpose DifferenceEngine, and Babbage made little progress in the actual constructionof the device. Although Babbage’s ideas wouldremain obscure for nearly a century, he would then be recognizedas having designed most of the key elements of themodern computer: the central processor, memory, instructions,and data organization. Only in the lack of a capability35

36 backup and archive systemsthe economic value of data has increased. Potential threatsto data include bugs in the operating system or softwareapplications, malicious acts such as the introduction ofcomputer viruses, theft, hardware failure (such as in harddisk drives), power outages, fire, and natural disasters suchas earthquakes and floods.A variety of general principles must be considered indevising an overall strategy for creating and maintainingbackups:Reliability: Is there assurance that the data is stored accuratelyon the backup medium, and will automatic backupsrun reliably as scheduled? Can the data be accuratelyretrieved and restored if necessary?Physical storage: Is the backed-up data stored securely andorganized in a way to make it easy to retrieve particulardisks or tapes? Is the data stored at the site where it is tobe used, or off-site (guarding against fire or other disasterstriking the workplace).If it had been built, Charles Babbage’s Analytical Engine, althoughmechanical rather than electrical, would have had most of theessential features of modern computers. These included input,(via punched cards), a processor, a memory (store), and a printer.A reproduction of part of the early Difference Engine is shownhere. (Photo Researchers, Inc.)to manipulate memory addresses did the design fall short ofa modern computer.Further Reading“The Analytical Engine: the First Computer.” Available online. URL:http://www.fourmilab.ch/babbage/. Accessed April 20, 2007.Babbage, Henry Prevost, ed. Babbage’s Calculating Engines: A Collectionof Papers. With a new introduction by Allan G. Bromley.Los Angeles: Tomash, 1982.Campbell-Kelly, M., ed. The Works of Charles Babbage. 11 vols.London: Picerking and Chatto, 1989.“Who Was Charles Babbage?” Charles Babbage Institute. Availableonline. URL: http://www.cbi.umn.edu/exhibits/cb.html.Accessed April 20, 2007.Swade, Doron D. “Redeeming Charles Babbage’s Mechanical Computer.”Scientific American, February 1993.backup and archive systemsThe need to create backup copies of data has become increasinglyimportant as dependence on computers has grown andThe daughter of poet Lord Byron, Lady Ada Lovelace (1815–52)acquired mathematical training usually denied to her gender.When she met Charles Babbage and learned about his computerdesign, she translated his work and wrote the world’s firstcomputer programs. (Photo Researchers, Inc. / SciencePhoto Library)

ackup and archive systems 37Ease of Use: To the extent backups must be set up or initiatedby human operators, is the system easy to understandand use with minimal training? Ease of use bothpromotes reliability (because users will be more likelyto perform the backups), and saves money in trainingcosts.Economy: How does a given system compare to others interms of the cost of the devices, software, media (suchas tapes or cartridges), training, and administration?The market for storage and backup software and serviceshas grown rapidly in the mid-2000s, driven in part bya new awareness of the need of corporations to protect theirvital data assets from natural disasters or possible terroristattacks (see cyberterrorism and disaster planning andrecovery). In many corporations the amount of data thatneeds to be backed up or archived grows at a rate of 50 percentper year or more.Choice of MethodsThe actual choice of hardware, software, and media dependsconsiderably on how much data must be backed up (andhow often) as well as whether the data is being generatedon individual PCs or being stored at a central location. (Seefile server, data warehouse.)Backups for individual PCs can be accomplished usingthe backup software that comes with various versions ofMicrosoft Windows or through third-party software.In addition to traditional tapes, the media used includeCDs or DVDs (for very small backups), tiny USB “flashdrives” (generally up to a few gigabytes of data), cartridgedrives (up to 70 gigabytes or more), or even compact externalUSB hard drives that can store hundreds of gigabytes.(see cd and dvd rom, flash drive, hard drive, tapedrive, and usb.)In addition to backing up documents or other data generatedby users, the operating system and applications softwareis often backed up to preserve configuration informationthat would otherwise be lost if the program were reinstalled.There are utilities for Microsoft Windows and other operatingsystems that simplify the backing up of configurationinformation by identifying and backing up only those files(such as the Windows Registry) that contain informationparticular to the installation.The widespread use of local area networks makes it easierto back up data automatically from individual PCs andto store data at a central location (see local area networkand file server). However, having all data eggs inone basket increases the importance of building reliabilityand redundancy into the storage system, including the useof RAID (multiple disk arrays), “mirrored” disk drives, anduninterruptible power supplies (UPS). Despite such measures,the potential risk in centralized storage has led toadvocacy of a “replication” system, preferably at the operatingsystem level, that would automatically create backupcopies of any given object at multiple locations on the network.Another alternative of growing interest is the use of theInternet to provide remote (off-site) backup services.By 2005 Gartner Research was reporting that about94 percent of corporate IT managers surveyed were usingor considering the use of “managed backup” services.IDC has estimated that the worldwide market for onlinebackup services would reach $715 million by 2011. Onlinebackup offers ease of use (the backups can be run automatically,and the service is particularly handy for laptopcomputer users on the road) and the security of off-sitestorage, but raise questions of privacy and security of sensitiveinformation, particularly if encryption is not builtinto the process. Online data storage is also provided toindividual users by a variety of service providers such asGoogle. Application Service Providers (ASPs) have a naturalentry into the online storage market since they alreadyhost the applications their users use to create data (seeapplication service provider).A practice that still persists in some mainframe installationsis the tape library, which maintains an archive of dataon tape that can be retrieved and mounted as needed.ArchivingAlthough using much of the same technology as makingbackups, archiving of data is different in its objectives andneeds. An archive is a store of data that is no longer neededfor routine current use, but must be retrievable upondemand, such as the production of bank records or e-mailas part of a legal process. (Data may also be archived forhistorical or other research purposes.) Since archives mayhave to be maintained for many years (even indefinitely),the ability of the medium (such as tape) to maintain datain readable condition becomes an important consideration.Besides physical deterioration, the obsolescence of file formatscan also render archived data unusable.Management ConsiderationsIf backups must be initiated by individual users, the usersmust be trained in the use of the backup system and motivatedto make backups, a task that is easy to put off toanother time. Even if the backup is fully automated, samplebackup disks or tapes should be checked periodically tomake sure that data could be restored from them. Backuppractices should be coordinated with disaster recovery andsecurity policies.Further ReadingBackup Review. Available online. URL: http://www.backupreview.info/index.php. Accessed April 22, 2007.Jacobi, Jon L. “Online Backup Services Come of Age.” PC WorldOnline, July 28, 2005. Available online. URL: http://www.pcworld.com/article/id,121970-page,1-c,utilities/article.html.Accessed April 22, 2007.Jackson, William. “Modern Relics: NIST and Others Work on Howto Preserve Data for Later Use.” Available online. URL: http://www.gcn.com/print/25_16/41069-1.html. Accessed April 22,2007.Storage Search. Available online. URL: http://www.storagesearch.com/. Accessed April 22, 2007.Preston, W. Curtis. Backup & Recovery. Sebastapol, Calif.: O’ReillyMedia, 2006.

38 Backus-Naur formBackus-Naur formAs the emerging discipline of computer science struggledwith the need to precisely define the rules for new programminglanguages, the Backus-Naur form (BNF) was devisedas a notation for describing the precise grammar of a computerlanguage. BNF represents the unification of separatework by John W. Backus and Peter Naur in 1958, when theywere trying to write a specification for the Algol language.A series of BNF statements defines the syntax of a languageby specifying the combinations of symbols that constitutevalid statements in the language.Thus in a hypothetical language a program can bedefined as follows: ::= programbeginend;Here the symbol ::= means “is defined as” and items inbrackets are metavariables that represent placeholdersfor valid symbols. For example, can consist of a number of different statements defined elsewhere.Statements in square brackets [] indicate optional elements.Thus the If statement found in most programminglanguages is often defined as: ::= if >boolean_expression> then[ else ]end if ;This can be read as “an If statement consists of a boolean_expression (something that evaluates to “true” or “false”)followed by one or more statements, followed by an optionalelse that in turn is followed by one or more statements, followedby the keywords end if.” Of course each item in anglebrackets must be further defined—for example, a Boolean_expression.Curly brackets {} specify an item that can be repeatedone or more times. For example, in the definition ::= { | }An identifier is defined as a letter followed by one or moreinstances of either a letter or a digit.An extended version of BNF (EBNF) offers operatorsthat make definitions more concise yet easier to read. Thepreceding definition in EBNF would be:Identifier = Letter{Letter | Digit}EBNF statements are sometimes depicted visually inrailroad diagrams, so called because the lines and arrowsindicating the relationship of symbols resemble railroadtracks. The definition of expressed in a railroaddiagram is depicted in the above figure.This “railroad diagram” indicates that an identifier must beginwith a letter, which can be followed by a digit or another letter.The tracks curving back indicate that an element can appear morethan once.BNF and EBNF are useful because they can provideunambiguous definitions of the syntax of any computer languagethat is not context-dependent (which is to say, nearlyall of them). It can thus serve as a reference for introductionof new languages (such as scripting languages) and fordevelopers of parsers for compilers.Further ReadingGarshol, Lars Marius. “BNF and EBNF: What Are They and HowDo They Work?” Available online. URL: http://www.garshol.priv.no/download/text/bnf.html. Accessed April 23, 2007.Jensen, K., N. Wirth et al. Pascal User Manual and Report: ISO PascalStandard. New York: Springer-Verlag, 1985.Sebesta, Robert W. Concepts of Programming Languages. 9th ed.Boston: Addison-Wesley, 2008.bandwidthIn its original sense, bandwidth refers to the range of frequenciesthat a communications medium can effectivelytransmit. (At either end of the bandwidth, the transmissionbecomes too attenuated to be received reliably.) For a standardvoice telephone, the bandwidth is about 3kHz.In digital networks, bandwidth is used in a rather differentsense to mean the amount of data that can be transmittedin a given time—what is more accurately described asthe information transfer rate. A common measurement isMb/sec (megabits per second). For example, a fast Ethernetnetwork may have a bandwidth of 100 Mb/sec while a homephone-line network might have a bandwidth of from 1 to 10Mb/sec and a DSL or cable modem runs at about 1 Mb/sec.(By comparison, a typical dial-up modem connection has abandwidth of about 28–56 kb/sec, roughly 20 times slowerthan even a slow home network.)The importance of bandwidth for the Internet is that itdetermines the feasibility of delivering new media such assound (MP3), streaming video, and digital movies over thenetwork, and thus the viability of business models based onsuch products. The growth of high-capacity access to theInternet (see broadband) is changing the way people usethe network.Further ReadingBenedetto, Sergio, and Ezio Biglieri. Principles of Digital Transmission:With Wireless Applications. New York: Springer, 1999.Smith, David R. Digital Transmission Systems. 3rd ed. New York:Kluwer Academic Publishers, 2003.

BASIC 39banking and computersBeginning in the 1950s, banks undertook extensive automationof operations, starting with electronic funds transfer(EFT) systems. Check clearing (the sending of checksfor payment to the bank on which they are drawn) wasfacilitated by the development of magnetic ink characterrecognition (MICR) that allowed checks to be automaticallysorted and tabulated. Today an automated clearinghouse (ACH) network processes checks and other paymentsthrough regional clearinghouses.Starting in the 1960s, the use of credit cards became anincreasingly popular alternative to checks, and they weresoon joined by automatic teller machine (ATM) networksand the use of debit cards (cards for transferring funds froma checking account at the point of sale).Direct deposit of payroll and benefit checks has alsobeen promoted for its safety and convenience. Credit card,ATM, and debit card systems rely upon large data processingfacilities operated by the issuing financial institution.Because of the serious consequences of system failure bothin immediate financial loss and customer goodwill, thesefund transfer systems must achieve a high level of reliabilityand security. Reliability is promoted through the useof fault-tolerant hardware (such as redundant systems thatcan take over for one another in the event of a problem).The funds transfer messages must be provided a high levelof security against eavesdropping or tampering through theuse of algorithms such as the long-established DES (DataEncryption Standard)—see encryption. Designers ofEFT systems also face the challenge of providing a legallyacceptable paper trail. Electronic signatures are increasinglyaccepted as an alternative to written signatures forauthorizing fund transfers.Online BankingThe new frontier of electronic banking is the online bank,where customers can access many banking functions viathe Internet, including balance queries, transfers, automaticpayments, and loan applications. For the consumer, onlinebanking offers greater convenience and access to informationthan even the ATM, albeit without the ability to obtaincash.From the bank’s point of view, online banking offers anew way to reach and serve customers while relieving thestrain on the ATM hardware and network. However, use ofthe Internet increases vulnerability to hackers and raisesissues of privacy and the handling of personal informationsimilar to those found in other e-commerce venues (seecomputer crime and security and privacy in the digitalage). In 2006 a Pew Center survey found that 43 percentof Internet users were banking online—a total of about63 million American adults. Other surveys have foundabout a third of Internet users now pay bills online. Thereare also a relatively small but growing number of Internetonlybanks, many of which are affiliated with traditionalbanks. A particularly attractive feature of online banking isthe ability to integrate bank services with popular personalfinance software such as Quicken.As impressive as it has been, the growth in online bankingmay have been inhibited by a perceived lack of security.A 2006 Gartner Research survey reported that nearly halfof adults surveyed said that concerns over the potential forinformation theft and computer attacks had affected theiruse of online services such as banking and e-commercetransactions. Gartner translates this to an estimated 33 millionU.S. adults who do not bank online because of suchconcerns. (Banks are frequently impersonated in deceptiveemails and Web sites—see phishing and spoofing.)In response, government regulations (FFIEC or FederalFinancial Institutions Examination Council) guidelinesissued in October 2005 required banks by the end of 2006to provide detailed risk assessments and mitigation plansfor dealing with data breaches. Large banks spent about $15million each on this process in 2006. Much greater expensesare likely as banks find themselves compelled to purchaseand install more-secure user authentication software. Theyface the multiple challenge of securing their systems whilereassuring their users and not forcing them to go throughcomplicated, hard-to-remember log-in procedures.Credit card issuers are also starting to turn to the Internetto provide additional services. According to the com-Score service 524 million credit card bills were paid onlinein 2006. By 2007 about 70 percent of all credit card holdershad logged on to their accounts at least once. Many customershave responded to incentives to discontinue receivingpaper statements.Further ReadingFox, Susannah, and Jean Beier. “Online Banking 2006: Surfingto the Bank.” Pew Internet & American Life Project, June14, 2006. Available online. URL: http://www.pewinternet.org/pdfs/PIP_Online_Banking_2006.pdf. Accessed April 23,2007.Macklin, Ben. “Trust Has Value in E-Commerce,” November 30,2006. Available online. URL: http://www.emarketer.com/Article.aspx?1004323. Accessed April 23, 2007.BASICThe BASIC (Beginner’s All-purpose Symbolic InstructionCode) language was developed by J. Kemeny and T. Kurtzat Dartmouth College in 1964. At the time, the college wasequipped with a time-shared computer system linked toterminals throughout the campus, an innovation at a timewhen most computers were programmed from a single locationusing batches of punch cards. John G. Kemeny andThomas Kurtz wanted to take advantage of the interactivityof their system by providing an easy-to-learn computer languagethat could compile and respond immediately to commandstyped at the keyboard. This was in sharp contrast tothe major languages of the time, such as COBOL, Algol, andFORTRAN in which programs had to be completely writtenbefore they could be tested.Unlike the older languages used with punch cards,BASIC programs did not have to have their keywords typedin specified columns. Rather, statements could be typedlike English sentences, but without punctuation and witha casual attitude toward spacing. In general, the syntax for

40 basic input/output systemdecision and control structures is simpler than other languages.For example, a for loop counting from 1 to 10 in Clooks like this:for (i = 1; i

Bell, C. Gordon 41has changed. There are now two fewer face cards (12 - 2 = 10)and four fewer non-face cards (40 - 4 = 36), so the probabilitythat a given card is a face card becomes 10/36 or 5/18.While this is pretty straightforward, in many situationsone cannot easily calculate the shifting probabilities. WhatBayes discovered was a more general formula:P(T|E) =P(E|T) * P(T)P(E)In this formula T is a theory or hypothesis about afuture event. E represents a new piece of evidence thattends to support or oppose the hypothesis. P(T) is an estimateof the probability that T is true, before considering theevidence represented by E. The question then becomes: IfE is true, what happens to the estimate of the probabilitythat T is true? This is called a conditional probability, representedby the left side of the equation, P(T|E), which isread “the probability of T, given E.” The right side of Bayes’sequation considers the reverse probability—that E will betrue if T turns out to be true. This is represented by P(E|T),multiplied by the prior probability of T and divided by theindependent probability of E.Practical ApplicationsIn the real world one generally has imperfect knowledgeabout the future, and probabilities are seldom as clear cutas those available to the card counter at the blackjack table.However, Bayes’s formula makes it possible to continuallyadjust or “tune” estimates based upon the accumulatingevidence. One of the most common applications of Bayesiananalysis is in e-mail filters (see spam). Bayesian spamfilters work by having the user identify a sample of messagesas either spam or not spam. The filter then looks forpatterns in the spam and non-spam messages and calculatesprobabilities that a future message containing thosepatterns will be spam. The filter then blocks future messagesthat are (above some specified threshold) probablyspam. While it is not perfect and does require work on thepart of the user, this technique has been quite effective inblocking spam.A Bayesian algorithm’s effectiveness can be expressed interms of its rate of false positives (in the spam example, thiswould be the percentage of messages that have been mistakenlyclassified as spam). If the rate of “true positives” istoo low, the algorithm is not effective enough. However, ifthe rate of false positives is too high, the negative effects(blocking wanted e-mail) might outweigh the positiveones (blocking unwanted spam).Further ReadingKantor, Andrew. “Bayesian Spam Filters Use Math that WorksLike Magic.” USA Today online, September 17, 2004. Availableonline. URL: http://www.usatoday.com/tech/columnist/andrewkantor/2004-09-17-kantor_x.htm. Accessed March15, 2007.Lee, Peter M. Bayesian Statistics: An Introduction. 3rd ed. NewYork: Wiley, 2004.Sivia, D. S. Data Analysis: A Bayesian Tutorial. 2nd ed. New York:Oxford University Press, 2006.“Thomas Bayes, 1702–1761.” St. Andrews University Mac Tutor.Available online. URL: http://www-history.mcs.st-andrews.ac.uk/Mathematicians/Bayes.html. Accessed March 15, 2007.BBS See bulletin board system.Bell, C. Gordon(1934– )AmericanEngineer, Computer DesignerChester Gordon Bell (also known as Gordon Bennet Bell)was born August 19, 1934, in Kirksville, Missouri. As ayoung boy Bell worked in his father’s electrical contractingbusiness, learning to repair appliances and wire circuits.This work led naturally to an interest in electronics, andBell studied electrical engineering at MIT, earning a B.S. in1956 and an M.S. in 1957. After graduation and a year spentas a Fulbright Scholar in Australia, Bell worked in the MITSpeech Computation Laboratory (see speech recognitionand synthesis). In 1960 he was invited to join the DigitalEquipment Corporation (DEC) by founders Ken Olsen andHarlan Anderson.Bell was a key architect of DEC’s revolutionary PDPseries (see minicomputer), particularly as designer of theinput/output (I/O) hardware in the PDP-1 and the multitaskingPDP-6. Bell left DEC to teach computer science atCarnegie Mellon University (1966–72), but then returned toDEC until his retirement in 1983 following a heart attack.During this time Bell developed a deployment plan for thenew VAX series minicomputers, which were data-processingworkhorses in many organizations during the 1970sand 1980s.As a close observer of the computer industry, Bell formulated“Bell’s Law of Computer Classes” in 1972. It basicallystates that as new technologies (such as the microprocessor)emerge, they result about once a decade in the emergenceof new “classes” or computing platforms, each beinggenerally cheaper and being perceived as a distinct productwith new applications. Within a given class, price tends tohold constant while performance increases. Examples thusfar include mainframes, minicomputers, personal computersand workstations, networks, cluster or grid computing,and today’s ubiquitously connected wireless, portabledevices. Bell has indeed suggested that the trend to ubiquitouscomputing will continue (see ubiquitous computingand wearable computers).After retirement Bell soon became active again. Hefounded Encore Computer, a company that specialized inmultiprocessor computers, and later was a founding memberof Ardent Computer as well as participating in the establishmentof the Microelectronics and Computer TechnologyCorporation, a consortium that attempted to be America’sanswer to a surging competitive threat from Japanese companies.Bell was also active in debates over technology policy,playing an instrumental role as an assistant directorin the National Science Foundation’s computing initiatives

42 Bell Laboratoriesand the early adoption of the Internet. In 1987 Bell establishedthe Gordon Bell Prize for achievements in parallelprocessing.Bell began the 1990s in a new role, helping Microsoftdevelop a research group, where he was still working as of2008. Here Bell has developed what amounts to a new paradigmfor managing personal data, a project called MyLife-Bits. Its main idea is that pictures, e-mails, documents, andother materials that are important to a person’s life andwork should be organized according to their chronologicaland other relationships so they can be retrieved naturallyand virtually automatically, eschewing the often arbitraryconventions of traditional file systems and interfaces. In1992 Bell presciently told a Computer World interviewerthat “twenty-five years from now . . . computers will beexactly like telephones. They are probably going to be communicatingall the time.”Bell also retains a strong interest in the history of computing.He cofounded the Computer History Museum inBoston in 1979 and was also a founder of its successor, theComputer History Museum in Mountain View, California.Bell is a distinguished member of the American Academyof Arts and Sciences, American Association for theAdvancement of Science, the Association for ComputingMachinery (ACM), and the Institute of Electrical and ElectronicEngineering (IEEE). His awards include the IEEEVon Neumann Medal, the AEA Inventor Award, and theNational Medal of Technology (1991).Further ReadingGordon Bell Home Page. Microsoft Bay Area Research Center.Available online. URL: http://research.microsoft.com/users/gbell/. Accessed April 30, 2007.Slater, Robert. Portraits in Silicon. Boston: MIT Press, 1987.“Vax Man: Gordon Bell.” Computerworld, June 22, 1992, p. 13.Available online. URL: http://research.microsoft.com/~gbell//CGB%20Files/Computerworld%20Vax%20Ma n%20920622%20c.pdf. Accessed April 30, 2007.Bell LaboratoriesBell Telephone Laboratories was established in 1925 inMurray Hill, New Jersey: It was intended to take over theresearch arm of the Western Electric division of AmericanTelephone and Telegraph (AT&T) and was jointly administeredby the two companies. The organization’s principaltask was to design and develop telephone switching equipment,but there was also research in facsimile (fax) transmissionand television.The research that would have the greatest impact,however, would come from a relative handful of Bell scientistswho were given resources to undertake fundamentalresearch. In the 1930s Bell scientist Karl Jansky, investigatinginterference with long-range radio transmissions,discovered that radio waves were arriving from space,leading to the development of radio astronomy. Other BellLabs developments of the 1930s and 1940s included thevocoder, an early electronic speech synthesizer, and thephotovoltaic cell, with its potential application to solarpower systems.Several Bell Labs technologies would have a directimpact on the computer field. The transistor, developedby Bell Labs researchers John Bardeen, Walter Brattain,and William Shockley, would make a new generation ofmore compact and reliable computers possible. Informationtheory (see information theory and Shannon,Claude) would revolutionize telecommunications, signalprocessing, and data transfer. Work on the laser in the1960s would eventually lead to the compact disc (see cdromand dvd-rom). Other hardware contributions includethe charge-coupled device (CCD) that would revolutionizeastronomical and digital photography and fiber-optic cablesfor high-volume data communications.In software engineering the most important achievementsof Bell researchers were the development of the Cprogramming language and the UNIX operating system inthe early 1970s (see c; Ritchie, Dennis; and unix). Theelegant design of the modular UNIX system is still admiredtoday, and versions of UNIX and Linux power many serversand networks.New Corporate DirectionPerhaps ironically, AT&T’s near monopolistic position inthe telecommunications industry both provided substantialrevenue for fundamental research and shielded the labfrom competitive pressure and the need to tie research tothe development of commercial products. As a result, BellLabs arguably became the most important private researchinstitution in the 20th century. By the end of the 1980s,however, court decisions had reshaped the landscape of thecommunications field, and Bell Labs became a victim of thecompany’s change from monopolist to competitor.In 1996 AT&T divested Bell Labs along with its mainequipment manufacturing facilities into a new company,Lucent Technologies. A smaller group of researchers wereretained and reorganized as AT&T Laboratories. As the 2000sbegan these researchers made new achievements, includingtiny transistors whose size is measured in atoms, opticaldata routing (see optical computing) and nanotechnology,DNA-based computing (see molecular computing), andother esoteric but potentially momentous fields.In recent years, however, the organization has largelychanged its focus from long-term research in fundamentaltopics to the search for projects that can be quickly turnedinto commercial products—in essence the requirement thatthe Labs become a profit center. The merger of Lucent andanother communications giant, Alcatel, in 2006 has led torenewed concerns that consolidation and even tighter integrationof the Labs with corporate goals might come at theexpense of the kind of research culture that has inspiredthe Labs’ greatest breakthroughs.Further ReadingAlcatel-Lucent Bell Laboratories. Available online. URL: http://www.alcatel-lucent.com. Accessed May 2, 2007.Bell Labs Technical Journal. Available online. URL: http://www3.interscience.wiley.com. Accessed May 2, 2007.Gehani, Narain. Bell Labs: Life in the Crown Jewel. Summit, N.J.:Silicon Press, 2003.

Berners-Lee, Tim 43benchmarkA benchmark is a tool used to evaluate or compare theperformance of computer software or systems. Typically,this involves the design of a program (or suite of programs)that performs a series of operations that mimic “real world”activities. For example, computer processors (CPUs) can begiven calculations in floating-point arithmetic, yielding aresult in “flops” (floating point operations per second). Similarly,several different C-language compilers can be giventhe same files of source code and rated according to howquickly they produce the executable code, as well as thecode’s compactness, speed, or efficiency.Some examples of computer industry benchmarksinclude:• Dhrystone and Whetstone for integer and floatingpoint arithmetic, respectively• mIPS (millions of instructions per second) andMFLOPS (millions of floating point instructions persecond) for microprocessors• FPS (frames per second) for various types of graphics• 3DMark for three-dimensional graphics• test suites using Linpack and LAPACK for supercomputersThe devising of appropriate benchmarks is importantbecause they can help prospective purchasers decidewhich competing CPU, program development tool, databasesystem, or Web server to buy. Often the aspectsof systems that are highlighted in advertising are notthose that are most relevant to determining their actualutility. For example, CPUs are often compared accordingto clock speed, but a chip with a superior architectureand algorithm for handling instructions might actuallyoutperform chips with faster clock speeds. By puttingchips through their paces using the same arithmetic, datatransfer, or graphics instructions, the benchmark providesa more valid comparison.The most relevant benchmarks tend to focus on re-creatingreal-world use. Thus database systems can be comparedin their speed of retrieval or update of data records.Real-world benchmarks also help guard against manufacturers“tweaking” their systems to create artificially highbenchmark results. Nevertheless, benchmarks cannot beused mechanically. While a given industry may have an“industry standard” benchmark, and a given product maybe the highest performer using that test, the user must considerhow well that benchmark reflects the actual work forwhich the system or program is being purchased. Performance,however well benchmarked, is usually only one keyconsideration, with environment (such as network connections),reliability, security, ease of use, and of course costbeing other considerations.Further Readingcomp.benchmarks (USENET newsgroup).Jones, Capers. Software Assessments, Benchmarks, and Best Practices.Boston: Addison-Wesley, 2000.Netlib [repository for mathematical benchmarking software].Available online. URL: http://www.netlib.org/. Accessed May10, 2007.Berners-Lee, Tim(1955– )BritishComputer ScientistA graduate of Oxford University, Tim Berners-Lee createdwhat would become the World Wide Web in 1989 whileworking at CERN, the giant European physics researchinstitute. At CERN, he struggled with organizing the dozensof incompatible computer systems and software thathad been brought to the labs by thousands of scientistsfrom around the world. With existing systems each requiringa specialized access procedure, researchers had littlehope of finding out what their colleagues were doing or oflearning about existing software tools that might solve theirproblems.Berners-Lee’s solution was to bypass traditional databasesystems and to consider text on all systems as “pages”that would each have a unique address, a universal documentidentifier (later known as a uniform resource locator,or URL). He and his assistants used existing ideas of hypertextto link words and phrases on one page to another page(see hypertext and hypermedia), and adapted existinghypertext editing software for the NeXT computer to createthe first World Wide Web pages, a server to provide accessto the pages and a simple browser, a program that could beused to read pages and follow the links as the reader desired(see Web server and Web browser). But while existinghypertext systems were confined to browsing a single fileor at most, the contents of a single computer system, Berners-Lee’sWorld Wide Web used the emerging Internet toprovide nearly universal access.Between 1990 and 1993, word of the Web spreadthroughout the academic community as Web software waswritten for more computer platforms (see World WideWeb). As demand grew for a body to standardize and shapethe evolution of the Web, Berners-Lee founded the WorldWide Web Consortium (W3C) in 1994 and continues asits director. Together with his colleagues, he has struggledto maintain a coherent vision of the Web in the face of tremendousgrowth and commercialization, the involvementof huge corporations with conflicting agendas, and contentiousissues of censorship and privacy. His general approachhas been to develop tools that would empower the user tomake the ultimate decision about the information he or shewould see or divulge.Berners-Lee now works as a senior researcher at theMassachusetts Institute of Technology Computer Scienceand Artificial Intelligence Laboratory. In his original visionfor the Web, users would create Web pages as easily as theycould read them, using software no more complicated thana word processor. While there are programs today that hidethe details of HTML coding and allow easier Web page creation,Berners-Lee feels the Web must become even easier to

44 Bezos, Jeffrey P.use if it is to be a truly interactive, open-ended knowledgesystem. He is also interested in developing software thatcan take better advantage of the rich variety of informationon the Web, creating a “semantic” Web of meaningful connectionsthat would allow for logical analysis and permithuman beings and machines not merely to connect, but toactively collaborate (see semantic Web and xml).In the debate over a possible tiered Internet service (seeInternet access policy) Berners-Lee has spoken out for“net neutrality,” the idea that priority given to materialpassing over the Internet should not depend on its contentor origin. He describes equal treatment to be a fundamentaldemocratic principle, given the primacy of the Net today.Berners-Lee has garnered numerous awards and honorarydegrees. In 1997 he was made an Officer of the BritishEmpire, and in 2001 he became a Fellow of the British RoyalSociety. Berners-Lee also received the Japan Prize in 2002and in that same year shared the Asturias Award with fellowInternet pioneers Lawrence Roberts, Robert Kahn, andVinton Cerf. In 2007 Berners-Lee received the Charles StarkDraper Prize of the U.S. National Academy of Engineering.Further ReadingBerners-Lee, Tim. Home page with biography and links: Availableonline. URL: http://www.w3.org/People/Berners-Lee/.Accessed April 20, 2007.———. Papers on Web design issues. Available online. URL:http://www.w3.org/DesignIssues/.———. “Proposal for the World Wide Web, 1989.” Availableonline. URL: http://www.w3.org/History/1989/proposal.html.Berners-Lee, Tim, and Mark Fischetti. Weaving the Web. San Francisco:HarperSanFrancisco, 1999.Henderson, Harry. Pioneers of the Internet. San Diego, Calif.:Lucent Books, 2002.Markoff, John. “ ‘Neutrality’ Is New Challenge for Internet Pioneer.”New York Times, September 27, 2006. Available online. URL:http://www.nytimes.com/2006/09/27/technology/circuits/27neut.html. Accessed April 25, 2007.Bezos, Jeffrey P.(1964– )AmericanEntrepreneurWith its ability to display extensive information and interactwith users, the World Wide Web of the mid-1990s clearlyhad commercial possibilities. But it was far from clear howtraditional merchandising could be adapted to the onlineworld, and how the strengths of the new medium could betranslated into business advantages. In creating Amazon.com, “the world’s largest bookstore,” Jeff Bezos would showhow the Web could be used to deliver books and other merchandiseto millions of consumers.Jeff Bezos was born on January 12, 1964, and grew upin Miami, Florida. He would be remembered as an intense,strong-willed boy who was fascinated by gadgets but alsoliked to play football and other sports. His uncle, PrestonGise, a manager for the Atomic Energy Commission,encouraged young Bezos’s interest in technology by givinghim electronic equipment to dismantle and explore. BezosJeff Bezos, founder and CEO of Amazon.com, poses for a portraitin the Internet retailer’s distribution center. (© Jack Kurtz/TheImage Works)also liked science fiction and became an enthusiastic advocatefor space colonization.Bezos entered Princeton University in 1982. At first hemajored in physics, but later switched to electrical engineering,graduating in 1986 with highest honors. By thenBezos had become interested in business software applications,particularly financial networks. At the age of only23, he led a project at Fitel, a financial communicationsnetwork, managing 12 programmers and commuting eachweek between the company’s New York and London offices.As a vice president at Bankers Trust, a major Wall Streetfirm in the late 1980s, Bezos became very enthusiastic aboutthe use of computer networking and interactive software forproviding timely information for managers and investors.However, he found that the “old line” Wall Street firmsresisted his efforts and declined to invest in these new usesof information technology.In 1990, however, Bezos was working at the D.E. ShawCompany and his employer asked him to research the commercialpotential of the Internet, which was starting to grow(even though the World Wide Web would not reach mostconsumers for another five years). Bezos ranked the top 20possible products for Internet sales. They included computersoftware, office supplies, clothing, music—and books.Analyzing the publishing industry, Bezos identifiedways in which he believed it was inefficient. Even largebookstores could stock only a small portion of the availabletitles, while on the other hand many books that werein stock stayed on the shelves for months, tying up moneyand space. Bezos believed that by combining a single hugewarehouse with an extensive tracking database, an onlineordering system, and fast shipping, he could satisfy manymore customers while keeping costs low.Bezos pitched his idea to D.E. Shaw. When the companydeclined to invest in the venture, Bezos decided to put hispromising corporate career on hold and start his own onlinebusiness. By then it was the mid-1990s and the World WideWeb was just starting to become popular, thanks to the newgraphical Web browsers such as Netscape.

inding 45Looking for a place to set up shop, Bezos decided on Seattle,partly because the state of Washington had a relativelysmall population (the only customers who would have topay sales tax) yet had a growing pool of technically trainedworkers, thanks to the growth of Microsoft and other companiesin the area. After several false starts he decided tocall his store Amazon, deciding that the name of the Earth’sbiggest river would be suited to earth’s biggest bookstore.Amazon’s first headquarters was a converted garage.Bezos soon decided that the existing software for mailorderbusinesses was too limited and set a gifted programmernamed Shel Kaphan to work creating a custom programthat could keep track not only of each book in stock, buthow long it would take to get more copies from the publisheror book distributor.By mid-1995 Amazon.com was ready go online from anew Seattle office using $145,553 contributed by Bezos’smother from the family trust. As word about the storespread through Internet chat rooms and a listing on Yahoo!,the orders began to pour in and Bezos had to struggle tokeep up. Despite the flood of orders, the business was losingmoney as expenses piled up even more quickly.Bezos went to Silicon Valley in search of venture capital.Bezos’s previous experience as a Wall Street “star,” togetherwith his self-confidence, enabled him to raise $1 million.Bezos believed that momentum was the key to long-termsuccess. The company’s motto became “get big fast.” Revenuewas poured back into the business, expanding salesinto other product lines such as music, video, electronics,and software. The other key element of Bezos’s growth strategywas to take advantage of the vast database that Amazonwas accumulating—not only information about books andother products, but about what products a given individualor type of customer was buying. Once a customer hasbought something from Amazon, he or she is greeted byname and given recommendations for additional purchasesbased upon what items other customers who had boughtthat item had also purchased. Customers are encouragedto write reviews of books and other items so that each customergets the sense of being part of a virtual peer group.By 1997, the year of its first public stock offering, Amazonseemed to be growing at an impressive rate. A yearlater the stock was worth almost $100 a share, and by 1999Jeff Bezos’s personal wealth neared $7.5 billion. Bezos andAmazon proved to be one of the few Internet businessesto weather the “dot-bust” collapse of 2000 and 2001. In2003 Amazon.com chalked up its first annual profit, andthe company’s stock prices tripled during that time.Bezos gained a reputation as a very demanding CEO,insisting on recruiting top talent, then demanding that projectsset bold goals and complete them ahead of schedule.The pressure resulted in high turnover of top executives,but Bezos has also been quick to encourage and rewardinitiative. (The company’s “Just Do It” program encouragesmanagers to start projects without asking permission oftheir superiors.)Aside from Amazon.com, Bezos has maintained hisinterest in space travel. In 2002 he founded a companycalled Blue Origin, whose spaceship project has remainedshrouded in secrecy. However, in January 2007 the companyreleased video of the first successful (albeit brief) testof a prototype suborbital passenger craft.Bezos has written a new chapter in the history of retailing,making him a 21st-century counterpart to such pioneersas Woolworth and Montgomery Ward. Time magazineacknowledged this by making him its 1999 Person of theYear, while Internet Magazine put Bezos on its list of the 10persons who have most influenced the development of theInternet.Further ReadingBlue Origin website. Available online. URL: http://public.blueorigin.com/index.html.Accessed April 10, 2007.Byers, Ann. Jeff Bezos: The Founder of Amazon.com. New York:Rosen Publishing Group, 2006.Marcus, James. Amazonia: Five Years at the Epicenter of the Dot.Com Juggernaut. New York: New Press, 2004.Spector, Robert. Amazon.com: Get Big Fast: Inside the RevolutionaryBusiness Model that Changed the World. New York: HarperBusiness, 2000.bindingDesigners of program compilers are faced with the questionof when to translate a statement written in the source languageinto final instructions in machine language (see alsoassembler). This can happen at different times dependingon the nature of the statement and the decision of the compilerdesigner.Many programming languages use formal data types(such as integer, floating point, double, string, and so on)that result in allocation of an exact amount of storage spaceto hold the data (see data types). A statement that declaresa variable with such a type can be effectively bound immediately(that is, a final machine code statement can be generated).This is also called compile-time binding.However, there are a variety of statements for whichbinding must be deferred until more information becomesavailable. For example, it is common for programmers to uselibraries of precompiled routines. A statement that calls sucha routine cannot be turned immediately into machine languagebecause the compiler doesn’t know the actual addresswhere the routine will be embedded in the final compiledprogram. (That address will be determined by a programcalled a linker that links the object code from the sourceprogram to the library routines called upon by that code.)Another aspect of binding arises when there is morethan one object in a program with the same name. In languagessuch as C or Pascal that use a nested block structure,lexical binding can determine that a name refers to theclosest declaration of that name—that is, the smallest scopethat contains that name (see variable). In a few languagessuch as Lisp, however, the reference for a name depends onhow (or for what) the function is being called, so bindingcan be done only at run time.Binding and Object-Oriented LanguagesThe use of polymorphism in object-oriented languages suchas C++ raises a similar issue. Here there can be a base class

46 bioinformaticsand a hierarchy of derived classes. A function in the baseclass can be declared to be virtual, and versions of the samefunction can be declared in the derived classes. In this casea statement containing a pointer to the function in the baseclass cannot be bound until run time, because only thenwill it be known which version of the virtual function isbeing called. However, compilers for object-oriented languagescan be written so they do early binding on statementsfor which it is safe (such as those involving staticdata types), but do dynamic binding when necessary.From the point of view of efficiency, early binding is betterbecause memory can be allocated efficiently. Dynamicbinding provides greater flexibility, however, and facilitatesdebugging—for example, because the name of a variableis normally lost once it is bound and the machine code isgenerated.Further ReadingAho, Alfred V., et al. Compilers: Principles, Techniques, and Tools.2nd ed. Reading, Mass.: Addison-Wesley, 2006.Scott, Michael L. Programming Language Pragmatics. 2nd ed. SanFrancisco: Morgan Kaufmann, 2005.bioinformaticsBroadly speaking, bioinformatics (and the related field ofcomputational biology) is the application of mathematicaland information-science techniques to biology. This undertakingis inherently difficult because a living organism representssuch a complex interaction of chemical processes.Understanding any one process in isolation gives littleunderstanding of the role it plays in physiology. Similarly,as more has been learned about the genome of humansand other organisms, it has become increasingly clear thatthe “programs” represented by gene sequences are “interpreted”through complex interactions of genes and the environment.Given this complexity, the great strides that havebeen made in genetics and the detailed study of metabolicand other biological processes would have been impossiblewithout advances in computing and computer science.Application to GeneticsSince information in the form of DNA sequences is the heartof genetics, information science plays a key role in understandingits significance and expression. The sequences ofgenes that determine the makeup and behavior of organismscan be represented and manipulated as strings of symbolsusing, for example, indexing and search algorithms.It is thus natural that the advent of powerful computerworkstations and automated lab equipment would lead tothe automation of gene sequencing (determining the orderof nucleotides), comparing or determining the relationshipbetween corresponding sequences, and identifyingand annotating regions of interest. The completion of thesequencing of the human genome well ahead of schedulewas thus a triumph of computer science as much as biology.Today the systematic search for genetic and metabolic interactionshas been greatly sped up by the use of microarrays,silicon chips with grids of tiny holes that each contain aA scientist observes an experiment performed by roboticequipment. (Andrei Tchernov/iStockphoto)specified material that can be automatically tested for reactionto a given sample.Evolutionary BiologyThe ability to compare genes and to account for the effectsof mutation has also established evolutionary biology on afirm foundation. Given a good estimate of the mutation rate(a “molecular clock”) in mitochondrial DNA, the chronologyof species and common ancestors can be determinedwith considerable accuracy using statistical methods andappropriate data structures (see tree). The results of suchresearch have cast intriguing if sometimes controversiallight on such issues in paleontology as the relationshipbetween early modern humans and Neanderthals. Computationalgenetics can also measure the biodiversity of apresent-day ecosystem and predict the likely future of particularspecies in it.From Genes to ProteinsGene sequences are only half of many problems in biology.Computational techniques are also being increasinglyapplied to the analysis and simulation of the many intricate

iometrics 47chemical steps that link genetic information to expressionin the form of a particular protein and its three-dimensionalstructure in the process known as protein folding. Alreadymolecular simulations and predictive techniques are beingused to determine which of thousands of possible molecularconfigurations might have promising pharmaceuticalapplications. The development of better algorithms andmore powerful computing architectures for such analysiscan further speed up research, avoid wasteful “dead ends,”and bring effective treatments for cancer and other seriousdiseases to market sooner. Recently, the unlikely platformof a Sony PlayStation 3 and its powerful new processor hasbeen harnessed to turn gamers’ idle time to the processingof protein-folding data in the Folding@Home project.SimulationA variety of other types of biological computer simulationhave been employed. Examples include the chemicalcomponents (metabolites and enzymes) that are responsiblefor metabolic activity in organisms, the structure ofthe nervous system and the brain (see neural network),and the interaction of multiple predators and food sourcesin an ecosystem. Simulations can also incorporate algorithmsfirst devised by artificial intelligence researchers(see genetic algorithms and artificial life). Simulationsare combined with sophisticated graphics to enableresearchers to visualize structure. Such visualization canprovide insight and encourage intuitive “leaps” that mightbe missed when working only with formulas. Visualizationalgorithms developed for biomedical research can alsobe applied to the development of advanced MRI and otherscans for use in diagnosis and therapy.A Fruitful RelationshipBioinformatics has been one of the “hottest” areas in computingin recent years, often following trends in the broader“biotech” sector. This challenging field involves such diversesubjects as genetics, biochemistry, physiology, mathematics(structural and statistical), database analysis and searchtechniques (see data mining), simulation, modeling, graphics,and image analysis. Major projects often involve closecooperation between bioinformatics specialists and otherresearchers. Many computer scientists may find it profitableto study biology just as biologists will need to learn aboutand master the latest software tools. Researchers must alsoconsider how the availability of ever-increasing computingpower might make previously impossible projects feasible(see supercomputer and grid computing). (The NationalInstitutes of Health (NIH) currently funds seven biomedicalcomputation centers, including the National Center forPhysics-based Simulation of Biological Structures at StanfordUniversity. )The relationship between biology and computer scienceseems destined to be even more fruitful in coming years. Assoftware tools allow researchers to probe ever more deeplyinto biological processes and to bridge the gap betweenphysics, biochemistry, and the emergent behavior of livingorganisms, understanding of those processes may in turninspire the creation of new architectures and algorithms inareas such as artificial intelligence and robotics.Further ReadingBader, David A. “Computational Biology and High-PerformanceComputing.” Communications of the ACM 47, 11 (2004): 34–41.Brent, Roger, and Jehoshua Bruck. “Can Computers Help toExplain Biology?” Nature 440 (March 23, 2006): 416.Campbell, A. Malcolm, and Laurie J. Heyer. Discovering Genomics,Proteomics, and Bioinformatics. 2nd ed. San Francisco: BenjaminCummings, 2006.Claverie, Jean-Michel, and Cedric Notredame. Bioinformatics forDummies. 2nd ed. Indianapolis: Wiley, 2006.Cohen, Jacques. “Computer Science and Bioinformatics.” Communicationsof the ACM 48 (2005): 72–78.“Just the Facts: A Basic Introduction to the Science UnderlyingNCBI Resources: Bioinformatics.” National Center for BiotechnologyInformation. Available online. URL: http://www.ncbi.nlm.nih.gov/About/primer/bioinformatics.html. AccessedApril 24, 2007.Computers can create detailed representations that give scientistsunprecedented ability to visualize nature’s most intricate structures.This is a computer model of trypanathione Reductase, a proteincrystal. (NASA photo; Marshall Space Flight CenterImage Exchange)biometricsThe earliest use of biometrics was probably the developmentby Alphonse Bertillon in 1882 of anthropometry, a systemof classification by physical measurements and description.While this was soon supplanted by the discovery that fingerprintscould serve as an easier to use means of uniqueidentification of persons, the need for a less invasive meansof physical identification has led to the development of a

48 biometricsvariety of biometric scanners that take Bertillon’s ideas to amuch more detailed level.TechnologiesIn general, biometric scanning involves four steps: thecapture of an image using a camera or other device, theextraction of key features from the image, the creation ofa template that uniquely characterizes the person beingscanned, and the matching of the template to stored templatesin order to identify the person.There are several possible targets for biometric scanning,including the following areas:Facial ScanningFacial scanning uses cameras and image analysis softwarethat looks at areas of the human face that change littleduring the course of life and are not easily alterable, suchas the upper outline of the eye sockets and the shape ofthe cheekbones. Researchers at MIT developed a series ofabout 125 grayscale images called eigenfaces from whichfeatures can be combined to characterize any given face.The template resulting from a scan can be compared withthe one on file for the claimed identity, and coefficientsexpressing the degree of similarity are calculated. Varianceabove a specified level results in the person being rejected.Facial scanning is often viewed as less intrusive than theuse of fingerprints, and it can also be applied to surveillanceimages.However, iris scanning involves the front of the eye and ismuch less intrusive, and the person being scanned needsonly to look into a camera.Voice ScanningVoice scanning and verification systems create a “voiceprint”from a speech sample and compare it to the voiceof the person being verified. It is a quick and nonintrusivetechnique that is particularly useful for remote transactionssuch as telephone access to banking information.Behavioral BiometricsBiometrics are essentially invariant patterns, and these canbe found in behavior as well as in physical features. One ofthe most promising techniques (recently patented) analyzesthe pace or rhythm of a person’s typing on a keyboard andgenerates a unique numeric code. A similar approach mightbe applicable to mouse usage.Applications of BiometricsDue to the expense of the equipment and the time involvedin scanning, biometrics were originally used primarily inverifying identity for people entering high-security installations.However, the development of faster and less intrusivetechniques, combined with the growing need to verify usersof banking (ATM) and other networks has led to a growingFinger ScanningFinger scanning involves the imaging and automatic analysisof the pattern of ridges on one or more fingertips. Unliketraditional fingerprinting, the actual fingerprint is notsaved, but only enough key features are retained to providea unique identification. This information can be stored in adatabase and also compared with full fingerprints stored inexisting databases (such as that maintained by the FederalBureau of Investigation). Finger scanning can meet withresistance because of its similarity to fingerprinting and theassociation of the latter with criminality.Hand GeometryThis technique measures several characteristics of thehand, including the height of and distance between thefingers and the shape of the knuckles. The person beingscanned places the hand on the scanner’s surface, aligningthe fingers to five pegs. Hand-scanning is reasonably accuratein verifying an individual compared to the templateon file, but not accurate enough to identify a scan from anunknown person.Iris and Retina ScanningThese techniques take advantage of many unique individualcharacteristics of these parts of the eye. The scannedcharacteristics are turned into a numeric code similar to abar code. Retina scanning can be uncomfortable because itinvolves shining a bright light into the back of the eye, andhas generally been used only in high-security installations.A portable iris recognition scanner being demonstrated at the Biometrics2004 exhibition and conference in London. (Ian Waldie/Getty Images)

BIOS 49interest in biometrics. For example, a pilot program in theUnited Kingdom has used iris scanning to replace the PIN(personal identification number) as a means of verifyingATM users.The general advantage of biometrics is that it does notrely on cards or other artifacts that can be stolen or otherwisetransferred from one person to another, and in turn,a person needing to identify him or herself doesn’t haveto worry about forgetting or losing a card. However, whileworkers at high-security installations can simply be requiredto submit to biometric scans, citizens and consumers havemore choice about whether to accept techniques they mayview as uncomfortable, intrusive, or threatening to privacy.Recent heightened concern about the stealing of personalidentification and financial information (see identitytheft) may promote greater acceptance of biometric techniques.For example, a built-in fingerprint reader (alreadyprovided on some laptop computers) could be used tosecure access to the hard drive or transmitted to authenticatean online banking customer.Of course every security measure has the potential forcircumvention or misuse. Concerns about the stealing andcriminal use of biometric data (particularly online) mightbe addressed by a system created by Emin Martinian of theMitsubishi Electric Research Laboratories in Cambridge,Massachusetts. The algorithm creates a unique code basedon a person’s fingerprint data. The data itself is not stored,and the code cannot be used to re-create it, but only tomatch against the actual finger.The growing use of biometrics by government agencies(such as in passports and border crossings) is of concernto privacy advocates and civil libertarians. When combinedwith surveillance cameras and central databases, biometrics(such as face analysis and recognition) could aidpolice in catching criminals or terrorists, but could alsobe used to strip the anonymity from political protesters.The technology is thus double-edged, with the potentialboth to enhance the security of personal information and toincrease the effectiveness of surveillance.Further ReadingAshborn, Julian D. M. Biometrics: Advanced Identity Verification,the Complete Guide. New York: Springer-Verlag, 2000.“Biometrics Overview.” Available online. URL: http://www.biometricgroup.com/a_bio1/_technology/research_a_technology.htm.Accessed April 20, 2007.Biometrics Research Homepage at Michigan State University. Availableonline. URL: http://biometrics.cse.msu.edu/. AccessedApril 24, 2007.“Biometrics: Who’s Watching You?” Electronic Frontier Foundation.Available online. URL: http://www.eff.org/Privacy/Surveillance/biometrics/.Accessed April 24, 2007.Harreld, Heather. “Biometrics Points to Greater Security.” FederalComputer Week, July 22, 1999. Available online. URL:http://www.cnn.com/TECH/computing/9907/22/biometrics.idg/index.html.Jain, Anil, Ruud Bolle, and Sharath Pankanti. Biometrics: PersonalIdentification in Networked Society. Norwell, Mass.: KluwerAcademic Publishers, 1999.Woodward, John D., Nicholas M. Orlans, and Peter T. Higgins.Biometrics: Identity Assurance in the Information Age. NewYork: McGraw-Hill, 2002.BIOS (Basic Input-Output System)With any computer system a fundamental design problemis how to provide for the basic communication between theprocessor (see cpu) and the devices used to obtain or displaydata, such as the video screen, keyboard, and paralleland serial ports.In personal computers, the BIOS (Basic Input-OutputSystem) solves this problem by providing a set of routinesfor direct control of key system hardware such as diskdrives, the keyboard, video interface, and serial and parallelports. In PCs based on the IBM PC architecture, theBIOS is divided into two components. The fixed code isstored on a PROM (programmable read-only memory) chipcommonly called the “ROM BIOS” or “BIOS chip.” Thiscode handles interrupts (requests for attention) from theperipheral devices (which can include their own specializedBIOS chips). During the boot sequence the BIOS coderuns the POST (power-on self test) and queries variousdevices to make sure they are functional. (At this time thePC’s screen will display a message giving the BIOS manufacturer,model, and other information.) Once DOS is running,routines in the operating system kernel can accessthe hardware by making calls to the BIOS routines. In turn,application programs can call the operating system, whichpasses requests on to the BIOS routines.The BIOS scheme has some flexibility in that part ofthe BIOS is stored in system files (in IBM PCs, IO.SYS andIBMIO.COM). Since this code is stored in files, it can beupgraded with each new version of DOS. In addition, separatedevice drivers can be loaded from files during systemstartup as directed by DEVICE commands in CONFIG.SYS,a text file containing various system settings.For further flexibility in dealing with evolving devicecapabilities, PCs also began to include CMOS (complementarymetal oxide semiconductor) chips that allow for thestorage of additional parameters, such as for the configurationof memory and disk drive layouts.In modern PCs the BIOS setup screen also allows usersto specify the order of devices to be used for loading systemstartup code. This, for example, might allow a potentiallycorrupted hard drive to be bypassed in favor of a bootableCD or DVD with disk repair tools. Another scenario wouldallow users to boot from a USB memory stick (see flashdrive) and use a preferred operating system and workingfiles without disturbing the PC’s main setup.The data on these chips is maintained by a small onboardbattery so settings are not lost when the main systempower is turned off.Additionally, modern PC BIOS chips use “flash memory”(EEPROM or “electrically erasable programmable read-onlymemory”) to store the code. These chips can be “flashed” orreprogrammed with newer versions of the BIOS, enabling thesupport of newer devices without having to replace any chips.Beyond the BiosWhile the BIOS scheme was adequate for the earliest PCs,it suffered from a lack of flexibility and extensibility. Theroutines were generic and thus could not support all thefunctions of newer devices. Because BIOS routines for

50 bitmapped imagesuch tasks as graphics tended to be slow, applications programmersoften bypassed the BIOS and dealt with devicesdirectly or created device drivers specific to a particularmodel of device. This made the life of the PC user morecomplicated because programs (particularly games) maynot work with some video cards, for example, or at leastrequired an updated device driver.While both the main BIOS and the auxiliary BIOS chipson devices such as video cards are still essential to theoperation of the PC, modern operating systems, such asMicrosoft Windows and applications written for them, generallydo not use BIOS routines and employ high performancedevice drivers instead. (By the mid-1990s BIOSesincluded built-in support for “Plug and Play,” a system forautomatically loading device drivers as needed. Thus, theBIOS is now usually of concern only if there is a hardwarefailure or incompatibility.)Further Reading“System BIOS Function and Operation.” Available online. URL:http://www.pcguide.com/ref/mbsys/bios/func.htm. AccessedApril 20, 2007.bitmapped imageA bitmap is a series of bits (within a series of bytes inmemory) in which the bits represent the pixels in an image.In a monochrome bitmap, each pixel can be represented byone bit, with a 1 indicating that the pixel is “on.” For grayscaleor color images several bits must be used to store theinformation for each pixel. The pixel value bits are usuallypreceded by a data structure that describes various characteristicsof the image.For example, in the Microsoft Windows BMP format,the file for an image begins with a BITMAPFILEHEADERthat includes a file type, size, and layout. This is followedby a BITMAPINFOHEADER that gives information aboutthe image itself (dimensions, type of compression, andcolor format). Next comes a color table that describes eachIn a monochrome bitmapped image, a 1 is used to represent a pixelthat is turned on, while the empty pixels are represented by zeroes.Color bitmaps must use many more bits per pixel to store colornumbers.color found in the image in terms of its RGB (red, green,blue) components. Finally comes the consecutive bytes representingthe bits in each line of the image, starting fromlower left and proceeding to the upper right.The actual number of bits representing each pixeldepends on the dimensions of the bitmap and the numberof colors being used. For example, if the bitmap has amaximum of 256 colors, each pixel value must use one byteto store the index that “points” to that color in the colortable. However, an alternative format stores the actual RGBvalues of each pixel in three consecutive bytes (24 bits),thus allowing for a maximum of 24 (16,777,216) colors (seecolor in computing).Shortcomings and AlternativesThe relationship between number of possible colors andamount of storage needed for the bitmap means that themore realistic the colors, the more space is needed to storean image of a given size, and generally, the more slowly thebitmap can be displayed. Various techniques have been usedto shrink the required space by taking advantage of redundantinformation resulting from the fact that most imageshave areas of the same color (see data compression).Vector graphics offer an alternative to bitmaps, particularlyfor images that can be constructed from a series of lines.Instead of storing the pixels of a complete image, vector graphicsprovides a series of vectors (directions and lengths) plusthe necessary color information. This can make for a muchsmaller image, as well as making it easy to scale the image toany size by multiplying the vectors by some constant.Further ReadingArtymiak, Jacek. Dynamic Bitmap Graphics with PHP and Gd. 2nded. Lublin, Poland: devGuide.net, 2007.“Microsoft Windows Bitmap File Format Summary.” FileFormat-Info. Available online. URL: http://www.fileformat.info/format/bmp/egff.htm. Accessed May 10, 2007.Slaybaugh, Matt. Professional Web Graphics. Boston: Course Technology,2001.bits and bytesComputer users soon become familiar with the use of bits(or more commonly bytes) as a measurement of the capacityof computer memory (RAM) and storage devices suchas disk drives. They also speak of such things as “16-bitcolor,” referring to the number of different colors that canbe specified and generated by a video display.In the digital world a bit is the smallest discernablepiece of information, representing one of two possible states(indicated by the presence or absence of something such asan electrical charge or magnetism, or by one of two voltagelevels). Bit is actually short for “binary digit,” and a bit correspondsto one digit or place in a binary (base 2) number.Thus an 8-bit value of11010101corresponds, from right to left, to (1 * 2 0 ) + (0 * 2 1 ) + (1 *2 2 ) + (0 * 2 3 ) + (1 * 2 4 ) + (0 * 2 5 ) + (1 * 2 6 ) + (1 * 2 7 ), or 213in terms of the familiar decimal system.

itwise operations 51in terms of bytes. A byte is 8 bits or binary digits, whichamounts to a range of from 0 to 255 in terms of decimal (base10) numbers. A byte is thus enough to store a small integeror a character code in the standard ASCII character set(see character). Common multiples of a byte are a kilobyte(thousand bytes), megabyte (million bytes), gigabyte (billionbytes), and occasionally terabyte (trillion bytes). The actualnumbers represented by these designations are actually somewhatlarger, as indicated in the accompanying table.Further Reading“How Bits and Bytes work.” Available online. URL: http://www.howstuffworks.com/bytes.htm. Accessed April 22, 2007.One byte in memory can store an 8-bit binary number. Just as eachplace to the left in a decimal number represents the next higherpower of 10, the places in the byte increase as powers of 2. Here theplaces with 1 in them add up to a total decimal value of 213.With regard to computer architectures the numberof bits is particularly relevant to three areas: (1) The sizeof the basic “chunk” of data or instructions that can befetched, processed, or stored by the central processing unit(CPU); (2) The “width” of the data bus over which data issent between the CPU and other devices—given the sameprocessor speed, a 32-bit bus can transfer twice as muchdata in a given time as a 16-bit bus; and (3) The width of theaddress bus (now generally 32 bits), which determines howmany memory locations can be addressed, and thus themaximum amount of directly usable RAM.The first PCs used 8-bit or 16-bit processors, whiletoday’s PC processors and operating systems often use 32-bits at a time, with 64-bit processors now entering the market.Besides the “width” of data transfer, the number of bitscan also be used to specify the range of available values.For example, the range of colors that can be displayed bya video card is often expressed as 16 bit (65,536 colors) or32 bit (16,777,777,216 colors, because only 24 of the bits areused for color information).Since multiple bits are often needed to specify meaningfulinformation, memory or storage capacity is often expressedbitwise operationsSince each bit of a number (see bits and bytes) can holda truth value (1 = true, 0 = false), it is possible to use individualbits to specify particular conditions in a system, andto compare individual pairs of bits using special operatorsthat are available in many programming languages.Bitwise operators consist of logical operators and shiftoperators. The logical operators, like Boolean operators ingeneral (see Boolean operators), perform logical comparisons.However, as the name suggests, bitwise logical operatorsdo a bit-for-bit comparison rather than comparing theoverall value of the bytes. They compare the correspondingbits in two bytes (called source bits) and write result bitsbased on the type of comparison.The AND operator compares corresponding bits andsets the bit in the result to one if both are one. Otherwise, itsets it to zero.Example: 10110010 AND 10101011 = 10100010The OR operator compares corresponding bits and setsthe bit in the result to one if either or both of the bits areones.Example: 10110110 OR 10010011 = 10110111The XOR (“exclusive OR”) operator works like ORexcept that it sets the result bit to one only if either (notboth) of the source bits are ones.Example: 10110110 XOR 10010011 = 00100101The COMPLEMENT operator switches all the bits totheir opposites (ones for zeroes and zeroes for ones).Example: COMPLEMENT 11100101 = 00011010Measurement Number of Bytes examples of Usebyte 1 small integer, characterkilobyte 2 10 1,024 RAM (PCs in the 1980s)megabyte 2 20 1,048,576 hard drive (PCs to mid-1990s)RAM (modern PCs)gigabyte 2 30 1,073,741,824 hard drive (modern PCs)RAM (latest PCs)terabyte 2 40 1,099,511,627,776 large drive arrays

52 blogs and bloggingThe shift operators simply shift all the bits left (LEFTSHIFT) or right (RIGHT SHIFT) by the number of placesspecified after the operator. Thus00001011 LEFT SHIFT 2 = 00101100and00001011 RIGHT SHIFT 2 = 00000010 (bits that shift offthe end of the byte simply “drop off” and are replaced withzeroes).While we have used words in our general description ofthese operators, actual programming languages often usespecial symbols that vary somewhat with the language. Theoperators used in the C language are typical:& AND| OR^ Exclusive OR~ Complement>> Right Shift

Boolean operators 53Blogging can also be seen as part of a larger trend towardWeb users taking an active role in expressing and sharingopinion and resources (see user-created content, filesharingand p2p networks, and YouTube).Social and Economic ImpactBlogs first emerged in popular consciousness as a new wayin which people caught in the midst of a tragedy such as theSeptember 11, 2001, attacks could reassure friends abouttheir safety while describing often harrowing accounts. TheIraq war that began in 2003 was the first war to be bloggedon a large scale. Like their journalistic counterparts, bloggers,whether American or Iraqi, were “embedded” in theoften-violent heart of the protracted conflict, but they werealso effectively beyond the control of government or militaryauthorities. (See also political activism and theInternet.)Blogs are also being used widely in business. Within acompany, a blog can highlight ongoing activities and relevantresources that might otherwise be overlooked in a large corporatenetwork. Software developers can also report on theprogress of bug fixes or enhancements and solicit commentsfrom end users. There has been some concern, however, thatcorporate blogs are not sufficiently supervised to preventthe dissemination of sensitive information or the posting oflibelous or inflammatory material. (For the collaborative creationof large bodies of structured knowledge, see wikis andWikipedia.)Blogs have provided an outlet where other means ofexpression are unavailable because of war (as in Iraq),disaster (Hurricane Katrina), or government censorship—although China in particular has hired hundreds of censorsto remove offending postings as well as requiring blog providerssuch as MSN to police their content (see censorshipand the Internet).Further ReadingBlogger. Available online. URL: http://www.bloger.com. AccessedSeptember 2, 2007.Bloglines. Available online. URL: http://www.bloglines.com. AccessedApril 10, 2007.Blood, Rebecca. The Weblog Handbook: Practical Advice on Creatingand Maintaining Your Blog. Cambridge, Mass.: Perseus, 2002.Burden, Matthew Currier. The Blog of War: Front-Line Dispatchesfrom Soliders in Iraq and Afghanistan. New York: Simon &Schuster, 2006.Dedman, Jay. Videoblogging. New York: Wiley, 2006.Farber, Dan. “Reflections on the First Decade of Blogging.” February25. 2007. Available online. URL: http://blogs.zdnet.com/BTL/?p=4541&tag=nl.e539. Accessed April 10, 2007.Hasin, Hayder. WordPress Complete: Set Up, Customize, and MarketYour Blog. Birmingham, U.K.: Packt Publishing, 2006.Radio Userland. Available online. URL: http://radio.userland.com.Accessed September 2, 2007.Rebecca’s Pocket. Available online. URL: http://www.rebeccablood.net/. Accessed April 10, 2007.Technorati. Available online. URL: http://www.technorati.com.Accessed April 10, 2007.WordPress. Available online. URL: http:// www.wordpress.com.Accessed April 10, 2007.BluetoothLoosely named after a 10th-century Danish king, Bluetoothis a wireless data communications and networking systemdesigned for relatively short-range operation (generallywithin the same room, although it can be used over longerdistances up to several hundred feet [tens of meters]). Theradio transmission is in the 2.4-GHz band and is typicallylow power, making it suitable for battery-powered devicessuch as laptops.ApplicationsBluetooth was originally developed by Ericsson Corporationto provide a wireless connection for mobile telephoneheadsets. Today it is often used to “sync” (update data)between a PDA such as a Blackberry or Palm (see PDA)with a Bluetooth-equipped laptop or desktop. Many cellphones are also equipped with Bluetooth, allowing them tobe dialed from a PDA, although the growing use of phonesthat combine telephony and PDA functions is making thisscenario less common (see smartphone). Bluetooth canalso be used for wireless keyboards, mice, or printers.It is possible to connect PDAs or PCs to the Internet andlocal area networks using a Bluetooth wireless access point(WAP) attached to a router, but faster and longer range Wifi(802.11) wireless connections are much more widely usedfor this application (see Wifi).Bluetooth connections between devices are specifiedusing profiles. Profiles have been developed for commonkinds of devices, specifying how data is formatted andexchanged. For example, there are profiles for controllingtelephones, printers and faxes, digital cameras, and audiodevices. Most modern operating systems (including WindowsMobile, Linux, Palm OS, and Mac OS X) include supportfor basic Bluetooth profiles. Functions fundamental toall Bluetooth operations are found in Bluetooth Core Specifications(version 2.1 as of August 2007). Planned futureenhancements include accommodation for ultra-wide band(UWB) radio technology, allowing for data transfer up to480 megabits per second. At the same time, Bluetooth isextending the ultra-low-power modes that are particularlyimportant for wearable or implanted medical devices.Further Reading“Bluetooth.” Wikipedia. Available online. URL: http://en.wikipedia.org/wiki/Bluetooth. Accessed July 20, 2007.Bluetooth Special Interest Group. Available online. URL: http://www.bluetooth.com/bluetooth/. Accessed July 20, 2007.Layton, Julia, and Curt Franklin. “How Bluetooth Works.” Availableonline. URL: http://www.howstuffworks.com/bluetooth.htm. Accessed September 3, 2007.Boolean operatorsIn 1847, British mathematician George Boole proposed asystem of algebra that could be used to manipulate propositions,that is, assertions that could be either true or false. Inhis system, called propositional calculus or Boolean Algebra,propositions can be combined using the “and” and “or”

54 boot sequenceoperators (called Boolean operators), yielding a new propositionthat is also either true or false. For example:“A cat is an animal” AND “The sun is a star” is truebecause both of the component propositions are true.“A square has four sides” AND “The Earth is flat” is falsebecause only one of the component propositions is true.However “A square has four sides” OR “The Earth isflat” is true, because at least one of the component propositionsis true.A chart called a truth table can be used to summarizethe AND and OR operations. Here 1 means true and 0means false, and you read across from the side and downfrom the top to see the result of each combination.AND table0 10 0 01 0 1OR table0 10 0 11 1 1A variant of the OR operator is the “exclusive OR,”sometimes called “XOR” operator. The XOR operator yieldsa result of true (1) if only one of the component propositionsis true:XOR table0 10 0 11 1 0Additionally, there is a NOT operator that simplyreverses the truth value of a proposition. That is, NOT 1 is0 and NOT 0 is 1.ApplicationsNote the correspondence between the two values of Booleanlogic and the binary number system in which each digit canhave only the values of 1 or 0. Electronic digital computersare possible because circuits can be designed to follow therules of Boolean logic, and logical operations can be harnessedto perform arithmetic calculations.Besides being essential to computer design, Booleanoperations are also used to manipulate individual bits inmemory (see bitwise operations), storing and extractinginformation needed for device control and other purposes.Computer programs also use Boolean logic to make decisionsusing branching statements such as If and loop statementssuch as While. For example, the Basic loopWhile (Not Eof()) OR (Line = 50)Read (Line$)Print (Line$)Line = Line + 1Endwhilewill read and print lines from the previously opened fileuntil either the Eof (end of file) function returns a value ofTrue or the value of Line reaches 50. (In some programminglanguages different symbols are used for the operators. InC, for example, AND is &&, OR is ||, and NOT is !.)Users of databases and Web search engines are alsofamiliar with the use of Boolean statements for definingsearch criteria. In many search engines, the search phrase“computer science” AND “graduate” will match sites thathave both the phrase “computer science” and the word“graduate,” while sites that have only one or the other willeither not be listed or will be listed after those that haveboth (see search engine).Further ReadingUniversity at Albany Libraries. “Boolean Searching on the Internet.”Available online. URL: http://www.albany.edu/library/internet/boolean.html.Whitesitt, J. E. Boolean Algebra and Its Applications. New York:Dover, 1995.boot sequenceAll computers are faced with the problem that they needinstructions in order to be able to read in the instructionsthey need to operate. The usual solution to this conundrumis to store a small program called a “loader” in a ROM(read-only memory) chip. When the computer is switchedon, this chip is activated and runs the loader. The loaderprogram has the instructions needed to be able to accessthe disk containing the full operating system. This processis called booting (short for “bootstrapping”).Booting a PCWhile the details of the boot sequence vary with the hardwareand operating system used, a look at the booting of a“Wintel” machine (IBM architecture PC running DOS andMicrosoft Windows) can serve as a practical example.When the power is turned on, a chip called the BIOS(basic input-output system) begins to execute a small program(see bios). The first thing it does is to run a routinecalled the POST (power-on self test) that sends aquery over the system bus (see bus) to each of the keydevices (memory, keyboard, video display, and so on) fora response that indicates it is functioning properly. If anerror is detected, the system generates a series of beeps,the number of which indicates the area where the problemwas found, and then halts.Assuming the test runs successfully (sometimes indicatedby a single beep), the BIOS program then queries thedevices to see if they have their own BIOS chips, and if so,executes their programs to initialize the devices, such asthe video card and disk controllers. At this point, since thevideo display is available, informational and error messagescan be displayed as appropriate. The BIOS also sets variousparameters such as the organization of the disk drive, usinginformation stored in a CMOS chip. (There is generallya way the user can access and change these informationscreens, such as when installing additional memory chips.)

anching statements 55The BIOS now looks for a disk drive that is bootable—that is, that contains files with the code needed to load theoperating system. This is generally a hard drive, but couldbe a floppy disk or even a CD-ROM or USB device. (Theorder in which devices are checked can be configured.) Ona hard drive, the code needed to start the operating systemis found in a “master boot record.”The booting of the operating system (DOS) involves thedetermination of the disk structure and file system and theloading of the operating system kernel (found in files calledIO.SYS and MSDOS.SYS), and a command interpreter (COM-MAND.COM). The latter can then read the contents of thefiles AUTOEXEC.BAT and CONFIG.SYS, which specify systemparameters, device drivers, and other programs to beloaded into memory at startup. If the system is to run MicrosoftWindows, that more elaborate operating system will thentake over, building upon or replacing the foundation of DOS.Further ReadingPC Guide. “System Boot Sequence.” Available online. URL: http://www.pcguide.com/_ref/mbsys/bios/bootSequence-c.html.Accessed April 10, 2008.branching statementsThe simplest calculating machines (see calculator)could only execute a series of calculations in an unalterablesequence. Part of the transition from calculator to fullcomputer is the ability to choose different paths of executionaccording to particular values—in some sense, to makedecisions.Branching statements (also called decision statementsor selection statements) give programs the ability to chooseone or more different paths of execution depending on theresults of a logical test. The general form for a branchingstatement in most programming languages isif (Boolean expression)statementelse statementFor example, a blackjack game written in C might have astatement that reads:if ((Card_Count + Value(This_Card)) > 21)printf (“You’re busted!”);Here the Boolean expression in parenthesis following the ifkeyword is evaluated. If it is true, then the following statement(beginning with printf) is executed. (The Booleanexpression can be any combination of expressions, functioncalls, or even assignment statements, as long as they evaluateto true or false—see also boolean operators.)The else clause allows the specification of an alternativestatement to be executed if the Boolean expression is nottrue. The preceding example could be expanded to:if (Card_Count + Value (This_Card) > 21)printf (“You’re busted!”);elseprintf(“Do you want another card?”);In most languages if statements can be nested so that asecond if statement is executed only if the first one is true.For example:if (Turn > Max_Turns){if (Winner() )PrintScore();}Here the first if test determines whether the maximumnumber of turns in the game has been exceeded. If it has,the second if statement is executed, and the Winner() functionis called to determine whether there is a winner. Ifthere is a winner, the PrintScore() function is called. Thisexample also illustrates the general rule in most languagesthat wherever a single statement can be used a block ofstatements can also be used. (The block is delimited bybraces in the C family of languages, while Pascal usesBegin . . . End.)The switch or case statement found in many languagesis a variant of the if statement that allows for easy testing ofseveral possible values of a condition. One could write:if (Category = = “A”)AStuff();else if (Category = = “B”)BStuff();else if (Category = = “C”)CStuff();elseprintf “(None of the above\n”);However, C, Pascal, and many other languages provide amore convenient multiway branching statement (calledswitch in C and case in Pascal). Using a switch statement,the preceding test can be rewritten in C as:switch (Category) {case “A”:AStuff();break;case “B”:BStuff();break;case “C”CStuff();break;default:printf (“None of the above\n”);}(Here the break statements are needed to prevent executionfrom continuing on through the other alternatives whenonly one branch should be followed.)Further ReadingSebesta, Robert W. Concepts of Programming Languages. 8th ed.Boston: Addison-Wesley, 2008.

oadbandTechnically, broadband refers to the carrying of multiplecommunications channels in a single wire or cable. In thebroader sense used here, broadband refers to high-speeddata transmission over the Internet using a variety of technologies(see data communications and telecommubroadband57ficial skin and an array of 32 separate motors, Leonardo’sfacial expressions are much more humanlike than Kismet’s.Body language now includes shrugs. The robot can learnnew concepts and tasks both by interacting with a humanteacher and by imitating what it sees people do, startingwith facial expressions and simple games.Breazeal’s group at MIT is currently investigating waysin which computers can use “body language” to communicatewith users and even encourage better posture. “RoCo”is a computer whose movable “head” is a monitor screen.Using a camera, RoCo can sense the user’s posture andemotional state.Breazeal has also created “responsive” robots in newforms, and for venues beyond the laboratory. In 2003 theCooper-Hewitt National Design Museum in New Yorkhosted a “cyberfloral installation” designed by Breazeal. Itfeatured “flowers” of metal and silicone that exhibit behaviorssuch as swaying and glowing in bright colors when aperson’s hand comes near.Besides earning her a master’s degree (1993) and doctoraldegree (2000) from MIT, Breazeal’s work has broughther considerable acclaim and numerous appearances in themedia. She has been widely recognized as being a significantyoung inventor or innovator, such as by Time magazineand the Boston Business Forward. Breazeal is one of 100“young innovators” featured in MIT’s Technology Review.Further ReadingBar-Cohen, Yoseph, and Cynthia Breazeal. Biologically InspiredIntelligent Robots. Bellingham, Wash.: SPIE Press, 2003.Biever, Celeste. “Robots Like Us: They Can Sense Human Moods.”San Francisco Chronicle, May 6, 2007. Available online. URL:http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/05/06/ING9GPK9U51.DTL. Accessed May 7, 2007.Breazeal, Cynthia. Designing Sociable Robots. Cambridge, Mass.:MIT Press, 2002.Brooks, Rodney. Flesh and Machines: How Robots Will Change Us.New York: Pantheon Books, 2002.Dreifus, Claudia. “A Passion to Build a Better Robot, One withSocial Skills and a Smile.” New York Times, June 10, 2003, p.F3.Henderson, Harry. Modern Robotics: Building Versatile Machines.New York: Chelsea House, 2006.Robotic Life Group (MIT Media Lab). Available online. URL:http://robotic.media.mit.edu/. Accessed May 1, 2007.Brin, Sergey(1973– )Russian-AmericanEntrepreneurCofounder and current president of technology at Google,Sergey Brin has turned the needs of millions of Web usersto find information online into a gigantic and pervasiveenterprise.Brin was born in Moscow, Russia, on August 21, 1973to a Jewish family (his father, Michael, was a mathematicianand economist). However, the family immigratedto the United States in 1979, settling in Maryland. Brin’sfather supplemented his education, particularly in mathematics.Brin graduated with honors from the Universityof Maryland in 1993, earning a bachelor’s degree in computerscience and mathematics. Brin then went to Stanford,receiving his master’s degree in computer science in 1995.Along the way to his Ph.D., however, Brin was “sidetracked”by his growing interest in the Internet and World WideWeb, particularly in techniques for searching for and identifyingdata (see also data mining).Search Engines and GoogleThe year 1995 was pivotal for Brin because he met fellowgraduate student Larry Page (see Page, Larry). Pageshared Brin’s interests in the Web, and they collaboratedon a seminal paper titled “The Anatomy of a Large-ScaleHypertextual Web Search Engine.” This work (includingthe key “PageRank” algorithm) would form the basis for theworld’s most widely used search engine (see Google andsearch engine).In 1998 Brin took a leave of absence from the Ph.D. program.The fall of that year Brin and Page launched Google.The search engine was much more useful and accurate thanexisting competitors, and received a Technical ExcellenceAward from PC magazine in 1999. Google soon appearednear the top of many analysts’ lists of “companies to watch.”In 2004 the company went public, and Brin’s personal networth is now estimated to be more than $16 billion. (Brinand Page remain closely involved with Google, promotinginnovation such as the aggregation and presentation ofinformation including images and maps.)Besides Google, Brin’s diverse interests include moviemaking(he was an executive producer of the film BrokenArrow) and innovative transportation (he is an investor inTesla Motors, makers of long-range electric vehicles). In2005 Brin was named as one of Time magazine’s 100 mostinfluential people. In 2007 Brin was named by PC World asnumber one on their list of the 50 most important peopleon the Web.Further ReadingBrin, Sergey, and Lawrence Page. “The Anatomy of a Large-ScaleHypertextual Web Search Engine.” Available online. URL:http://infolab.stanford.edu/~backrub/google.html. AccessedSeptember 3, 2007.“The Founders of Google.” NPR Fresh Air interview, October 14,2003 [audio]. Available online. URL: http://www.npr.org/templates/story/story.php?storyId=1465274. Accessed September3, 2007.Sergey Brin’s Home Page. Available online. URL: http://infolab.stanford.edu/~sergey/. Accessed September 3, 2007.“Sergey Brin Speaks with UC Berkeley Class” [video]. Availableonline. URL: http://video.google.com/videoplay?docid=7582902000166025817. Accessed September 3, 2007.

58 broadbandnications). This can be distinguished from the relativelyslow (56 Kbps or slower) dial-up phone connections used bymost home, school, and small business users until the late1990s. A quantitative change in speed results in a qualitativechange in the experience of the Web, making continuousmultimedia (video and sound) transmissions possible.Broadband TechnologiesThe earliest broadband technology to be developed consistsof dedicated point-to-point telephone lines designated T1,T2, and T3, with speeds of 1.5, 6.3, and 44.7 Mbps respectively.These lines provide multiple data and voice channels,but cost thousands of dollars a month, making thempracticable only for large companies or institutions.Two other types of phone line access offer relativelyhigh speed at relatively low cost. The earliest, ISDN (IntegratedServices Digital Network) in typical consumer formoffers two 64 Kbps channels that can be combined for 128Kbps. (Special services can combine more channels, such asa 6 channel 384 Kbps configuration for videoconferencing.)The user’s PC is connected via a digital adapter rather thanthe usual analog-to-digital modem.The most common telephone-based broadband systemtoday is the digital subscriber line (see DSL). Unlike ISDN,DSL uses existing phone lines. A typical DSL speed todayis 1–2 Mbps, though higher speed services up to about 5Mbps are now being offered. The main drawback of DSL isthat the transmission rate falls off with the distance fromthe telephone company’s central office, with a maximumdistance of about 18,000 feet (5,486.4 m).The primary alternative for most consumers uses existingtelevision cables (see cable modem). Cable is generallya bit faster (1.5–3 Mbps) than DSL, with premium serviceof up to 8 Mbps or so available in certain areas. However,cable speed slows down as more users are added to a givencircuit. With both DSL and cable upload speeds (the rateat which data can be sent from the user to an Internet site)are generally fixed at a fraction of download speed (oftenabout 128 kbps). While this “throttling” of upload speeddoes not matter much for routine Web surfing, the growingnumber of applications that involve users uploading videosor other media for sharing over the Internet (see user-createdcontent) has led to some pressure for higher uploadspeeds.Ultra BroadbandRather surprisingly, the country that brought the world theInternet has fallen well behind many other industrializednations in broadband speed. In Japan, DSL speeds up to40 Mbps are available, and at less cost than in the UnitedStates. South Korea also offers “ultra broadband” speeds of20 Mbps or more. American providers, on the other hand,have tended to focus on expanding their networks andcompeting for market share rather than investing in higherspeed technologies. However, this situation is beginning toimprove as American providers ramp up their investmentin fiber networks (see fiber optics). For example, in 2005Verizon introduced Fios, a fiber-based DSL service that canreach speeds up to 15 Mbps. However, installing fiber networksis expensive, and as of 2007 it was available in onlyabout 10 percent of the U.S. market.Cable and phone companies typically offer Internet andTV as a package—many are now including long-distancephone service (and even mobile phone service) in a “tripleplay” package. (For long-distance phone carried via Internet,see voip).Wireless BroadbandThe first wireless Internet access was provided by a wirelessaccess point (WAP), typically connected to a wired Internetrouter. This is still the most common scenario in homesand public “hot spots” (see also Internet cafés and“hot spots”). However, with many people spending muchof their time with mobile devices (see laptop, PDA, andsmartphone), the need for always-accessible wireless connectivityat broadband speeds has been growing. The largestU.S. service, Nextlink, offered wireless broadband in 37markets in 2007 (including many large and mid-sized cities)at speeds starting at 1.5 Mbps. An alternative is offeredby cell phone companies such as Verizon and Sprint, which“piggy back” on the existing infrastructure of cell phonetowers. However, the speed of this “3G” service is slower,from 384 kbps up to 2 Mbps.Yet another alternative beginning to appear is WiMAX,a technology that is conceptually similar to Wifi but hasmuch greater range because its “hot spots” can be manymiles in diameter. WiMAX offers the possibility of coveringentire urban areas with broadband service, although questionsabout its economic viability have slowed implementationas of 2008.Satellite Internet services have the advantage of beingavailable over a wide area. The disadvantage is that there isabout a quarter-second delay for the signal to travel from ageostationary satellite at an altitude of 22,300 km. (Loweraltitudesatellites can be used to reduce this delay, but thenmore satellites are needed to provide continuous coverage.)Adoption and ApplicationsBy mid-2007, 53 percent of adult Americans had a broadbandconnection at home. This amounts to 72 percent ofhome Internet users. (About 61 percent of broadband connectionsused cable and about 37 percent DSL.)With dial-up connections declining to less than 25percent, Web services are increasingly designed with theexpectation that users will have broadband connections.This, however, has the implication that users such as ruralresidents and the inner-city poor may be subjected to a“second class” Web experience (see also digital divide).Meanwhile, as with connection speed, many other countriesnow surpass the United States in the percentage ofbroadband users.Broadband Internet access is virtually a necessity formany of the most innovative and compelling of today’sInternet applications. These include downloading media(see podcasting, streaming, and music and video distribution,online), uploading photos or videos to sites

Brooks, Rodney 59such as Flickr and YouTube, using the Internet as a substitutefor a traditional phone line (see voip), and even gaming(see online games). Broadband is thus helping drive theintegration of many forms of media (see digital convergence)and the continuous connectivity that an increasingnumber of people seem to be relying on (see ubiquitouscomputing).Further ReadingBates, Regis. Broadband Telecommunications Handbook. 2nd ed.New York: McGraw-Hill, 2002.Bertolucci, Jeff. “Broadband Expands.” PC World (August 2007):77–90.Cybertelecom. “Statistics: Broadband.” Available online. URL:http://www.cybertelecom.org/data/broadband.htm. AccessedJuly 17, 2007.Gaskin, James E. Broadband Bible. New York: Wiley, 2004.Hellberg, Chris, Dylan Greene, and Truman Boyes. BroadbandNetwork Architectures: Designing and Deploying Triple-PlayServices. Upper Saddle River, N.J.: Prentice Hall, 2007.Brooks, Rodney(1954– )Australian, AmericanRoboticistRodney Brooks’s ideas about robots have found their wayinto everything from vacuum cleaners to Martian rovers.Today, as director of the Artificial Intelligence Laboratoryat the Massachusetts Institute of Technology, Brookshas extended his exploration of robot behavior into newapproaches to artificial intelligence.Brooks was born in Adelaide, Australia, in 1954. Asa boy he was fascinated with computers, but it was stillthe mainframe era, and he had no access to them. Brooksdecided to build his own logic circuits from discardedelectronics modules from the defense laboratory where hisfather worked. Brooks also came across a book by GreyWalter, inventor of the “cybernetic tortoise” in the late1940s. He tried to build his own and came up with “Norman,”a robot that could track light sources while avoidingobstacles. In 1968, when young Brooks saw the movie 2001:A Space Odyssey, he was fascinated by the artificial intelligenceof its most tragic character, the computer HAL 9000(see artificial intelligence and robotics).Brooks majored in mathematics at Flinders Universityin South Australia, where he designed a computer languageand development system for artificial intelligence projects.He also explored various AI applications such as theoremsolving, language processing, and games. He was then ableto go to Stanford University in Palo Alto, California, in 1977as a research assistant.While working for his Ph.D. in computer science,awarded in 1981, Brooks met John McCarthy, one of the“elder statesmen” of AI in the Stanford Artificial IntelligenceLab (SAIL). He also joined in the innovative projectsbeing conducted by researchers such as Hans Moravec, whowere revamping the rolling robot called the Stanford Cartand teaching it to navigate around obstacles.In 1984 Brooks moved to the Massachusetts Instituteof Technology. For his Ph.D. research project, Brooks andhis fellow graduate students equipped a robot with a ringof sonars (adopted from a camera rangefinder) plus twocameras. The cylindrical robot was about the size of R2D2and was connected by cable to a minicomputer. However,the calculations needed to enable a robot to identify objectsas they appear at different angles were so intensive that therobot could take hours to find its way across a room.Brooks decided to take a lesson from biological evolution.He realized that as organisms evolved into more complexforms, they could not start from scratch each time theyadded new features. Rather, new connections (and ways ofprocessing them) would be added to the existing structure.For his next robot, called Allen, Brooks built three “layers”of circuits that would control the machine’s behavior. Thesimplest layer was for avoiding obstacles: If a sonar signalsaid that something was too close, the robot would changedirection to avoid a collision. The next layer generated arandom path so the robot could “explore” its surroundingsfreely. Finally, the third layer was programmed to identifyspecified sorts of “interesting” objects. If it found one, therobot would head in that direction.Each of these layers or behaviors was much simplerthan the complex calculations and mapping done by a traditionalAI robot. Nevertheless, the layers worked together ininteresting ways. The result would be that the robot couldexplore a room, avoiding both fixed and moving obstacles,and appear to “purposefully” search for things.In the late 1980s, working with Grinell More and anew researcher, Colin Angle, Brooks built an insectlikerobot called Genghis. Unlike Allen’s three layers of behavior,Genghis had 51 separate, simultaneously running computerprograms. These programs, called “augmented finitestate machines,” each kept track of a particular state orcondition, such as the position of one of the six legs. It isthe interaction of these small programs that creates therobot’s ability to scramble around while keeping its balance.Finally, three special programs looked for signals from theinfrared sensors, locked onto any source found, and walkedin its direction.Brooks’s new layered architecture for “embodied” robotsoffered new possibilities for autonomous robot explorers.Brooks’s 1989 paper, “Fast, Cheap, and Out of Control: ARobot Invasion of the Solar System,” envisaged flocks oftiny robot rovers spreading across the Martian surface,exploring areas too risky when one has only one or twovery expensive robots. The design of the Sojourner Marsrover and its successors, Spirit and Opportunity, would partiallyembody the design principles developed by Brooksand his colleagues.In the early 1990s Brooks and his colleagues begandesigning Cog, a robot that would embody human eyemovement and other behaviors. Cog’s eyes are mountedon gimbals so they can easily turn to track objects, aidedby the movement of the robot’s head and neck (it has nolegs). Cog also has “ears”—microphones that can help itfind the source of a sound. The quest for more humanlikerobots continued in the late 1990s with the development of

60 bufferingKismet, a robot that includes dynamically changing “emotions.”Brooks’s student Cynthia Breazeal would build herown research career on Kismet and what she calls “sociablerobots” (see Breazeal, Cynthia).By 1990, Brooks wanted to apply his ideas of behaviorbasedrobotics to building marketable robots that couldperform basic but useful tasks, and he enlisted two of hismost innovative and hard-working students, Colin Angleand Helen Greiner (see iRobot Corporation). The companyis best known for the Roomba robotic vacuum cleaner.Brooks remains the company’s chief technical officer.Meanwhile Brooks has an assured place as one of thekey innovators in modern robotics research. He is a FoundingFellow of the American Association for Artificial Intelligenceand a Fellow of the American Association for theAdvancement of Science. Brooks received the 1991 Computersand Thought Award of the International Joint Conferenceon Artificial Intelligence. He has participated innumerous distinguished lecture series and has served as aneditor for many important journals in the field, includingthe International Journal of Computer Vision.Further ReadingBrockman, John. “Beyond Computation.” Edge 2000. Availableonline. URL: http://www.edge.org/3rd_culture/brooks_beyond/beyond_index.html. Accessed May 3, 2007.———. “The Deep Question: A Talk with Rodney Brooks.” Edge29 (November 19, 1997). Available online. URL: http://www.edge.org/documents/archive/edge29.html. Accessed May 3,2007.Brooks, Rodney. Flesh and Machines: How Robots Will Change Us.New York: Pantheon Books, 2002.Computer Science and Artificial Intelligence Laboratory (CSAIL),MIT. Available online. URL: http://www.csail.mit.edu/index.php. Accessed May 3, 2007.Henderson, Harry. Modern Robotics: Building Versatile Machines.New York: Chelsea House, 2006.O’Connell, Sanjida. “Cog—Is It More than a Machine?” LondonTimes (May 6, 2002): 10. Rodney Brooks [homepage]. CSAIL.Available online. URL: http://people.csail.mit.edu/brooks/.Accessed May 3, 2007.“Rodney Brooks—The Past and Future of Behavior Based Robotics”[Podcast]. Available online. URL: http://lis.epfl.ch/resources/podcast/mp3/TalkingRobots-RodneyBrooks.mp3.Accessed May 3, 2007.bufferingComputer designers must deal with the way different partsof a computer system process data at different speeds. Forexample, text or graphical data can be stored in main memory(RAM) much more quickly than it can be sent to aprinter, and in turn data can be sent to the printer fasterthan the printer is able to print the data. The solution tothis problem is the use of a buffer (sometimes called aspool), or memory area set aside for the temporary storageof data. Buffers are also typically used to store data to bedisplayed (video buffer), to collect data to be transmittedto (or received from) a modem, for transmitting audio orvideo content (see streaming) and for many other devices(see input/output). Buffers can also be used for data thatmust be reorganized in some way before it can be furtherprocessed. For example, character data is stored in a communicationsbuffer so it can be serialized for transmission.Buffering TechniquesThe two common arrangements for buffering data are thepooled buffer and the circular buffer. In the pool buffer,multiple buffers are allocated, with the buffer size beingequal to the size of one data record. As each data record isreceived, it is copied to a free buffer from the pool. When itis time to remove data from the buffer for processing, datais read from the buffers in the order in which it had beenstored (first in, first out, or FIFO). As a buffer is read, it ismarked as free so it can be used for more incoming data.In the circular buffer there is only a single buffer, largeenough to hold a number of data records. The buffer is setup as a queue (see queue) to which incoming data recordsare written and from which they are read as needed for processing.Because the queue is circular, there is no “first” or“last” record. Rather, two pointers (called In and Out) aremaintained. As data is stored in the buffer, the In pointer isincremented. As data is read back from the buffer, the Outpointer is incremented. If either pointer reaches aroundback to the beginning, it begins to wrap around. The softwaremanaging the buffer must make sure that if the Inpointer goes past the Out pointer, then the Out pointermust not go past In. Similarly, if Out goes past In, then Inmust not go past Out.The fact that programmers sometimes fail to check forbuffer overflows has resulted in a seemingly endless seriesof security vulnerabilities, such as in earlier versions of theUNIX sendmail program. In one technique, attackers canuse a too-long value to write data, or worse, commandsinto the areas that control the program’s execution, possiblytaking over the program (see also computer crime andsecurity).Buffering is conceptually related to a variety of othertechniques for managing data. A disk cache is essentially aspecial buffer that stores additional data read from a disk inanticipation that the consuming program may soon requestit. A processor cache stores instructions and data in anticipationof the needs of the CPU. Streaming of multimedia(video or sound) buffers a portion of the content so it can beplayed smoothly while additional content is being receivedfrom the source.Depending on the application, the buffer can be a partof the system’s main memory (RAM) or it can be a separatememory chip or chips onboard the printer or other device.Decreasing prices for RAM have led to increases in thetypical size of buffers. Moving data from main memoryto a peripheral buffer also facilitates the multitasking featurefound in most modern operating systems, by allowingapplications to buffer their output and continue processing.Further ReadingBuffer Overflow [articles]. Available online. URL: http://doc.bughunter.net/buffer-overflow/.Accessed May 23, 2007.Grover, Sandeep. “Buffer Overflow Attacks and Their Countermeasures.”Linux Journal, March 3, 2003. Available online.URL: http://www.linuxjournal.com/article/6701. AccessedMay 23, 2007.

ulletin board systems 61bugs and debuggingIn general terms a bug is an error in a computer programthat leads to unexpected and unwanted behavior. (Lore hasit that the first “bug” was a burnt moth found in the relaysof the early Mark I computer in the 1940s; however, as earlyas 1878 Thomas Edison had referred to “bugs” in the designof his new inventions.)Computer bugs can be divided into two categories: syntaxerrors and logic errors. A syntax error results fromfailing to follow a language’s rules for constructing statements,or from using the wrong symbol. For example, eachstatement in the C language must end with a semicolon.This sort of syntax error is easily detected and reported bymodern compilers, so fixing it is trivial.A logic error, on the other hand, is a syntactically validstatement that does not do what was intended. For example,if a C programmer writes:if Total = 100instead ofif Total == 100the programmer may have intended to test the value of Totalto see if it is 100, but the first statement actually assigns thevalue of 100 to Total. That’s because a single equals sign inC is the assignment operator; testing for equality requiresthe double equals sign. Further, the error will result in theif statement always being true, because the truth value of anassignment is the value assigned (100 in this case) and anynonzero value is considered to be “true” (see branchingstatements).Loops and pointers are frequent sources of logical errors(see loop and pointers and indirection). The boundarycondition of a loop can be incorrectly specified (for example,< 10 when < = 10 is wanted). If a loop and a pointer orindex variable are being used to retrieve data from an array,pointing beyond the end of the array will retrieve whateverdata happens to be stored out there.Errors can also be caused in the conversion of data ofdifferent types (see data types). For example, in many languageimplementations the compiler will automatically convertan integer value to floating point if it is to be assignedto a floating point variable. However, while an integer canretain at least nine decimal digits of precision, a float mayonly be able to guarantee seven. The result could be a lossof precision sufficient to render the program’s results unreliable,particularly for scientific purposes.Debugging TechniquesThe process of debugging (identifying and fixing bugs) isaided by the debugging features integrated into most modernprogramming environments. Some typical featuresinclude the ability to set a breakpoint or place in the codewhere the running program should halt so the values of keyvariables can be examined. A watch can be set on specifiedcertain variables so their changing values will be displayedas the program executes. A trace highlights the source codeto show what statements are being executed as the programruns. (It can also be set to follow execution into and throughany procedures or subroutines called by the main code.)During the process of software development, debuggingwill usually proceed hand in hand with software testing.Indeed, the line between the two can be blurry. Essentially,debugging deals with fixing problems so that the programis doing what it intends to do, while testing determineswhether the program’s performance adequately meets theneeds and objectives of the end user.Further ReadingAgans, David J. Debugging: The Nine Indispensable Rules for FindingEven the Most Elusive Software and Hardware Problems. NewYork: AMACOM, 2002.Robbins, John. Debugging Applications. Redmond, Wash.: MicrosoftPress, 2000.Rosenberg, Jonathan B. How Debuggers Work: Algorithms, DataStructures, and Architecture. New York: Wiley, 1996.bulletin board systems (BBS)An electronic bulletin board is a computer application thatlets users access a computer (usually with a modem andphone line) and read or post messages on a variety of topics.The messages are often organized by topic, resultingin threads of postings, responses, and responses to theresponses. In addition to the message service, many bulletinboards provide files that users can download, suchas games and other programs, text documents, pictures, orsound files. Some bulletin boards expect users to uploadfiles to contribute to the board in return for the privilege ofdownloading material.The earliest form of bulletin board appeared in the late1960s in government installations and a few universities participatingin the Defense Department’s ARPANET (the ancestorto the Internet). As more universities came online in theearly 1970s, the Netnews (or Usenet) system offered a way touse UNIX file-transfer programs to store messages in topicalnewsgroups (see netnews and newsgroups). The newssystem automatically propagated messages (in the form of a“news feed”) from the site where they were originally postedto regional nodes, and from there throughout the network.By the early 1980s, a significant number of personalcomputer users were connecting modems to their PCs. Bulletinboard software was developed to allow an operator(called a “sysop”) to maintain a bulletin board on his orher PC. Users (one or a few at a time) could dial a phonenumber to connect to the bulletin board. In 1984, programmerTom Jennings developed the Fido BBS software, whichallowed participating bulletin boards to propagate postingsin a way roughly similar to the distribution of UNIX Netnewsmessages.Decline of the BBSIn the 1990s, two major developments led to a drastic declinein the number of bulletin boards. The growth of major servicessuch as America Online and CompuServe (see onlineservices) offered users a friendlier user interface, a comprehensiveselection of forums and file downloads, and

CCThe C programming language was developed in the early1970s by Dennis Ritchie, who based it on the earlier languagesBCPL and B. C was first used on DEC PDP-11computers running the newly developed UNIX operatingsystem, where the language provided a high-level alternativeto the use of PDP Assembly language for developmentof the many utilities that give UNIX its flexibility.Since the 1980s, C and its descendent, C++, have becomethe most widely used programming languages.Language FeaturesLike the earlier Algol and the somewhat later Pascal, Cis a procedural language that reflects the philosophy ofprogramming that was gradually taking shape duringthe 1970s (see structured programming). In general,C’s approach can be described as providing the necessaryfeatures for real world computing in a compact andefficient form. The language provides the basic controlstructures such as if and switch (see branching statements)and while, do, and for (see loop). The built-indata types provide for integers (int, short, and long),floating-point numbers (float and double), and characters(char). An array of any type can be declared, and a stringis implemented as an array of char (see data types andcharacters and strings).Pointers (references to memory locations) are used for avariety of purposes, such as for storing and retrieving datain an array (see pointers and indirection). While theuse of pointers can be a bit difficult for beginners to understand,it reflects C’s emphasis as a systems programminglanguage that can “get close to the hardware” in manipulatingmemory.Data of different types can be combined into a recordtype called a struct. Thus, for example:struct Employee_Record {char [10] First_Name;char [1] Middle_Initial;char [20] Last_Name;int Employee_Number;} ;(There is also a union, which is a struct where the samestructure can contain one of two different data items.)The standard mathematical and logical comparisonoperators are available. There are a couple of quirks: theequals comparison operator is = =, while a single equal sign= is an assignment operator. This can create a pitfall for thewary, since the conditionif (Total = 10)printf (“Finished!”);always prints Finished, since the assignment Total = 10returns a value of 10 (which not being zero, is “true” andsatisfies the if condition).C also features an increment ++ and decrement - - operator,which is convenient for the common operation of raisingor lowering a variable by one in a counting loop. In Cthe following statements are equivalent:65

66 CTotal = Total + 1;Total += 1;Total ++;Unlike Pascal’s two separate kinds of procedures (func,or function, which returns a value, and proc, or procedure,which does not), C has only functions. Arguments arepassed to functions by value, but can be passed by referenceby using a pointer. (See procedures and functions.)Sample ProgramThe following is a brief example program:#include float Average (void);main () {printf (“The average is: %f”, Average() );}float Average (void) {int NumbersRead = 0;int Number;int Total = 0;while (scanf(“%d\n”, &Number) == 1){Total = Total + Number;NumbersRead = NumbersRead + 1;}return (Total / NumbersRead);}}Statements at the beginning of the program that beginwith # are preprocessor directives. These make changes tothe source code before it is compiled. The #include directiveadds the specified source file to the program. Unlike manyother languages, the C language itself does not includemany basic functions, such as input/output (I/O) statements.Instead, these are provided in standard libraries.(The purpose of this arrangement is to keep the languageitself simple and portable while keeping the implementationof functions likely to vary on different platforms separate.)The stdio.h file here is a “header file” that definesthe I/O functions, such as printf() (which prints formatteddata) and scanf() (which reads data into the program andformats it).The next part of the program declares any functions thatwill be defined and used in the program (in this case, thereis only one function, Average). The function declarationbegins with the type of data that will be returned by thefunction to the calling statement (a floating point value inthis case). After the function name comes declarations forany parameters that are to be passed to the function by thecaller. Since the Average function will get its data from userinput rather than the calling statement, the value (void) isused as the parameter.Following the declaration of Average comes the main()function. Every C program must have a main function. Mainis the function that runs when the program begins to execute.Typically, main will call a number of other functionsto perform the necessary tasks. Here main calls Averagewithin the printf statement, which will print the average asreturned by that function. (Calling functions within otherstatements is an example of C’s concise syntax.)Finally, the Average function is defined. It uses a loopto read in the data numbers, which are totaled and thendivided to get the average, which is sent back to the callingstatement by the return statement.A programmer could create this program on a UNIXsystem by typing the code into a source file (test.c in thiscase) using a text editor such as vi. A C compiler (gcc inthis case) is then given the source code. The source code iscompiled, and linked, creating the executable program filea.out. Typing that name at the command prompt runs theprogram, which asks for and averages the numbers.% gcc test.c% a.out579.The average is: 7.000000Success and ChangeIn the three decades after its first appearance, C became oneof the most successful programming languages in history.In addition to becoming the language of choice for mostUNIX programming, as microcomputers became capable ofrunning high-level languages, C became the language ofchoice for developing MS-DOS, Windows, and Macintoshprograms. The application programming interface (API) forWindows, for example, consists of hundreds of C functions,structures, and definitions (see application programminginterface and Microsoft Windows).However, C has not been without its critics amongcomputer scientists. Besides containing idioms that canencourage cryptic coding, the original version of C (asdefined in Kernighan and Ritchie’s The C ProgrammingLanguage) did not check function parameters to makesure they matched the data types expected in the functiondefinitions. This problem led to a large number ofhard-to-catch bugs. However, the development of ANSIstandard C with its stricter requirements, as well as typechecking built into compilers has considerably amelioratedthis problem. At about the same time, C++ becameavailable as an object-oriented extension and partial rectificationof C. While C++ and Java have considerablysupplanted C for developing new programs, C programmershave a relatively easy learning path to the newerlanguages and the extensive legacy of C code will remainuseful for years to come.Further ReadingKernighan, B. W., and D. M. Ritchie. The C Programming Language,2nd ed. Upper Saddle River, N.J.: Prentice-Hall, 1988.Prata, Stephen. C Primer Plus. 5th ed. Indianapolis: SAMS, 2004.Ritchie, D. M. “The Development of the C Language,” in History ofProgramming Languages II, ed. T. J. Bergin and R. G. Gibson,678–698. Reading, Mass.: Addison-Wesley, 1995.

C++ 67C#Introduced in 2002, C# (pronounced “C sharp”) is a programminglanguage similar to C++ and Java but simplifiedin several respects and tailored for use with Microsoft’slatest programming platform (see Microsoft.net). C# isa general-purpose language and is thoroughly objectoriented—allfunctions must be declared as members ofa class or “struct,” and even fundamental data types arederived from the System.Object class (see class and objectorientedprogramming).Compared with C++, C# is stricter about the use andconversion of data types, not allowing most implicit conversions(such as from an enumeration type to the correspondinginteger—see data structures). Unlike C++,C# does not permit multiple inheritance (where a type canbe derived from two or more base types), thereby avoidingan added layer of complexity in class relationships inlarge software projects. (However, a similar effect can beobtained by declaring multiple “interfaces” or specifiedways of accessing the same class.)Unlike Java (but like C++), C# includes pointers (anda safer version called “delegates”), enumerations (enumtypes), structs (treated as lightweight classes), and overloading(multiple definitions for operators). The latest versionof the language, C# 3.0 (introduced in 2007), providesadditional features for list processing and functional programming(see functional languages).The canonical “Hello World” program looks like this inC#:using System;// A “Hello World!” program in C#namespace HelloWorld{class Hello{static void Main(){System.Console.WriteLine(“Hello World!”);}}}Essentially all program structures must be part of aclass. The first statement brings in the System class, fromwhich are derived basic interface methods. A program canhave one or more namespaces, which are used to organizeclasses and other structures to avoid ambiguity. This programhas only one class (Hello), which includes a Mainfunction (every program must have one and only one). Thisfunction calls the Console member of the System class, andin turn uses the WriteLine method to display the text.C++ and Microsoft DevelopmentC# is part of a family of languages (including C++, J#[an equivalent version of Java], and Visual Basic.NET). Allthese languages compile to a common intermediate language(IL). The common class framework, Microsoft.NET,has replaced earlier frameworks for Windows programmingand, increasingly, for modern Web development (seealso Ajax).Although it has been primarily associated with Microsoftdevelopment and Windows, the Mono and Dot GNUprojects provide C# and an implementation of the CommonLanguage Infrastructure, and many (but not all) of the.NET libraries for the Linux/UNIX environment.Further Reading“The C# Language.” MSDN. Available online. URL: http://msdn2.microsoft.com/en-us/vcsharp/aa336809.aspx. Accessed April28. 2007.Davis, Stephen Randy. C# for Dummies. New York: Hungry Minds,2002.Hejlsberg, Andres, Scott Wiltamuth, and Peter Golde. The C# ProgrammingLanguage. 2nd ed. Upper Saddle River, N.J.: Addison-Wesley,2006.C++The C++ language was designed by Bjarne Stroustrup atAT&T’s Bell Labs in Murray Hill, New Jersey, starting in1979. By that time the C language had become well establishedas a powerful tool for systems programming (seeC). However Stroustrup (and others) believed that C’s limiteddata structures and function mechanism were provinginadequate to express the relationships found in increasinglylarge software packages involving many objects withcomplex relationships.Consider the example of a simple object: a stack ontowhich numbers can be “pushed” or from which they can be“popped” (see stack). In C, a stack would have to be implementedas a struct to hold the stack data and stack pointer,and a group of separately declared functions that couldaccess the stack data structure in order to, for example“push” a number onto the stack or “pop” the top numberfrom it. In such a scheme there is no direct, enforceablerelationship between the object’s data and functions. Thismeans, among other things, that parts of a program couldbe dependent on the internal structure of the object, orcould directly access and change such internal data. In alarge software project with many programmers working onthe code, this invites chaos.An alternative paradigm already existed (see objectorientedprogramming) embodied in a few new languages(see Simula and Smalltalk). These languages allow for thestructuring of data and functions together in the form ofobjects (or classes). Unlike a C struct, a class can containboth the data necessary for describing an object and thefunctions needed for manipulating it (see class). A class“encapsulates” and protects its private data, and communicateswith the rest of the program only through calls to itsdefined functions.Further in object-oriented languages, the principle ofinheritance could be used to proceed from the most general,abstract object to particular versions suited for specifictasks, with each object retaining the general capabilitiesand revising or adding to them. Thus, a “generic” list foundationclass could be used as the basis for deriving a varietyof more specialized lists (such as a doubly-linked list).

68 C++While attracted to the advantages of the object-orientedapproach, Stroustrup also wanted to preserve the Clanguage’s ability to precisely control machine behaviorneeded for systems programming. He thus decided to builda new language on C’s familiar syntax and features withobject-oriented extensions. Stroustrup wrote the first version,called “C with Classes” as his Ph.D. thesis at CambridgeUniversity in England. This gradually evolved intoC++ through the early 1980s.C++ FeaturesThe fundamental building block of C++ is the class. A classis used to create objects of its type. Each object containsa set of data and can carry out specified functions whencalled upon by the program. For example, the followingclass defines an array of integers and declares some functionsfor working with the array. Typically, it would be putin a header file (such as stack.h):const int Max_size=20; // maximum elementsin Stackclass Stack { // Declare the Stack classpublic: // These functions are availableoutsideStack(); // Constructor to create Stackobjectsvoid push (int); // push int on Stackint pop(); // remove top elementprivate: // This data can only be used inclassint index;int Data[Max_size];};Next, the member functions of the Stack class aredefined. The definitions can be put in a source file Stack.cpp:#include “Stack.h” // bring in the declarationsStack::Stack() { index=0;} // set zero fornew stackvoid Stack::push (int item) { // put a numberon stackData[index++] = item;}int Stack::pop(){ // remove top numberreturn Data [index–];}Now a second source file (Stacktest.cpp) can be written.It includes a main() function that creates a Stack object andtests some of the class functions:#include “Stack.cpp” // include the Stackclass#include // include standard I/Olibrarymain() {Stack S; // Create a Stack object called Sint index;for (index = 1; index

cache 69particularly for writing software to run on Web servers andbrowsers (see Java). For an alternative approach to creatinga somewhat more “streamlined” C-type language, see c#.Further Reading“C++ Archive.” Available online. URL: http://www.austinlinks.com/CPlusPlus/. Accessed May 24, 2007.“Complete C++ Language Tutorial.” Available online. URL:http://www.cplusplus.com/_doc/tutorial/. Accessed May24, 2007.Prata, Stephen. C++ Primer Plus. 5th ed. Indianapolis: SAMS,2004.Stroustrup, Bjarne. “A History of C++: 1979–1991.” In History ofProgramming Languages II, edited by Thomas J. Bergin, Jr.,and Richard G. Gibson, Jr. New York: ACM Press; Reading,Mass.: Addison-Wesley, 1996, 699–755.———. The C++ Programming Language. Special 3rd ed. Reading,Mass.: Addison-Wesley, 2000.cable modemOne of the most popular ways to connect people to theInternet takes advantage of the cable TV infrastructure thatalready exists in most communities. (For another pervasivealternative, using telephone lines, see dsl.)Cable systems offer high-speed access (see broadband)up to about 6 megabits/second (Mb/s), at least 20 timesfaster than an ordinary telephone modem and generallysuitable for receiving today’s multimedia offerings, includingstreaming video. (Upload speeds are usually “throttled”to 384 kb/s or fewer.)In a typical installation, a splitter is used to separate thesignal used for cable TV from the one used for data transmission.The data cable is then connected to the modem.The modem can then either be connected directly to a computerusing a standard Ethernet “Cat 5” cable, or connectedto a switch (or more commonly, a router) that will in turnprovide the Internet connection to computers on the localnetwork. (If the cable modem is connected directly to acomputer, additional security against intrusions should alsobe provided. See firewall.)A typical cable TV system has from 60 channels to severalhundred, most of which are used for TV programming.A few channels are dedicated to providing Internet service.Users in a given division of the cable network (typically asmall neighborhood) thus share a fixed pool of bandwidth,which can reduce speed at times of high usage. The cablesystem can adjust by reallocating channels from TV to dataor by adding new channels.DOCSIS (Data Over Cable Service Interface Specification)is the industry standard for cable modems in NorthAmerica.Marketing ConsiderationsAs of 2007 there were about 30 million households in NorthAmerica with cable Internet service. Monthly service feesare $40–$60, though cable providers generally try to bundletheir cable TV and Internet services. Increasingly theyare also offering telephone service over the cable network,using voice over Internet protocol (see voip).In turn, telephone companies compete with cable companiesby offering DSL Internet access. Although “traditional”DSL is generally somewhat slower than cablemodems, Verizon in 2005 announced a new, much fasterfiber-based form of DSL called fios, with speeds of up to15 Mb/s (see also fiber optics). And just as cable companiescan now offer phone service over the Internet, phonecompanies can offer video content, potentially competingwith cable TV services. (Verizon has announced its ownInternet-based television network, IPTV.) In general there islikely to be increased competition and more (if sometimesperplexing) choices for consumers.Further ReadingCable Industry Insider. Available online. URL: http://www.lightreading.com/cdn/.Accessed May 10, 2007.Cable Modem Information Network. Available online. URL: http://www.cable-modem.net/. Accessed May 10, 2007.Dominick, Joseph R., Barry L. Sherman, and Fritz J. Messere.Broadcasting, Cable, the Internet and Beyond: An Introductionto Electronic Media. 6th ed. New York: McGraw-Hill, 2007.Dutta-Roy, Amitava. Cable Modem: Technology and Applications.New York: Wiley-Interscience, 2007.cacheA basic problem in computer design is how to optimizethe fetching of instructions or data so that it will be readywhen the processor (CPU) needs it. One common solutionis to use a cache. A cache is an area of relatively fast-accessmemory into which data can be stored in anticipation of itsbeing needed for processing. Caches are used mainly in twocontexts: the processor cache and the disk cache.CPU CacheThe use of a processor cache is advantageous becauseinstructions and data can be fetched more quickly fromthe cache (static memory chips next to or within the CPU)than they can be retrieved from the main memory (usuallydynamic RAM). An algorithm analyzes the instructionscurrently being executed by the processor and triesto anticipate what instructions and data are likely to beneeded in the near future. (For example, if the instructionscall for a possible branch to one of two sets of instructions,the cache will load the set that has been used mostoften or most recently. Since many programs loop overand over again through the same instructions until somecondition is met, the cache’s prediction will be right mostof the time.)These predicted instructions and data are transferredfrom main memory to the cache while the processor isstill executing the earlier instructions. If the cache’s predictionwas correct, when it is time to fetch these instructionsand data they are already waiting in the high-speed cachememory. The result is an effective increase in the CPU’sspeed despite there being no increase in clock rate (the rateat which the processor can cycle through instructions).The effectiveness of a processor cache depends on twothings: the mix of instructions and data being processed and

70 calculatorthe location of the cache memory. If a program uses longsequences of repetitive instructions and/or data, caching willnoticeably speed it up. A cache located within the CPU itself(called an L1 cache) is faster (albeit more expensive) than anL2 cache, which is a separate set of chips on the motherboard.Changes made to data by the CPU are normally writtenback to the cache, not to main memory, until the cache isfull. In multiprocessor systems, however, designers of processorcaches must deal with the issue of cache coherency.If, for example, several processors are executing parts of thesame code and are using a shared main memory to communicate,one processor may change the value of a variable inmemory but not write it back immediately (since its cacheis not yet full). Meanwhile, another processor may load theold value from the cache, unaware that it has been changed.This can be prevented by using special hardware that candetect such changes and automatically “write through” thenew value to the memory. The processors, having receiveda hardware or software “signal” that data has been changed,can be directed to reread it.Disk CacheA disk cache uses the same general principle as a processorcache. Here, however, it is RAM (either a part of mainmemory or separate memory on the disk drive) that is thefaster medium and the disk drive itself that is slower. Whenan application starts to request data from the disk, the cachereads one or more complete blocks or sectors of data from thedisk rather than just the data record being requested. Then, ifthe application continues to request sequential data records,these can be read from the high-speed memory on the cacherather than from the disk drive. It follows that disk cachingis most effective when an application, for example, loads adatabase file that is stored sequentially on the disk.Similarly, when a program writes data to the disk, thedata can be accumulated in the cache and written back tothe drive in whole blocks. While this increases efficiency,if a power outage or other problem erases or corrupts thecache contents, the cache will no longer be in synch withthe drive. This can cause corruption in a database.Microsoft’s Windows Vista introduced an ingenioustype of cache at the system level. The “ReadyBoost” featuresallows many inexpensive USB flash drives to be used automaticallyas disk caches to store recently used data that hadbeen paged out of main RAM memory.Network CacheCaching techniques can be used in other ways. For example,most Web browsers are set to store recently read pageson disk so that if the user directs the browser to go back tosuch a page it can be read from disk rather than having tobe retransmitted over the Internet (generally a slower process).Web servers and ISPs (such as cable services) can alsocache popular pages so they can be served up quickly.Further ReadingNottingham, Mark. “Caching Tutorial for Web Authors and Webmasters.”Available online. URL: http://www.wdvl.com/Internet/Cache/index._html. Accessed May 24, 2007.“System Cache.” Available online. URL: http://www.pcguide.com/ref/mbsys/cache/. Accessed April 14, 2008.Peir, J.-K., W. Hsu, and A. J. Smith. “Implementation Issues inModern Cache Memories.” IEEE Transactions on Computers,48, 2 (1998): 100–110.calculatorThe use of physical objects to assist in performing calculationsbegins in prehistory with such practices as countingwith pebbles or making what appears to be countingmarks on pieces of bone. Nor should such simple manipulationsbe despised: In somewhat more sophisticated form ityielded the abacus, whose operators regularly outperformedmechanical calculators until the advent of electronics.Generally, however, the term calculator is used to referto a device that is able to store a number, add it to anothernumber, and mechanically produce the result, taking careof any carried digits. In 1623, astronomer Johannes Keplercommissioned such a machine from Wilhelm Schickard.The machine combined a set of “Napier’s bones” (slidesmarked with logarithmic intervals, the ancestor of the sliderule) and a register consisting of a set of toothed wheels thatcould be rotated to displays the digits 0 to 9, automaticallycarrying one place to the left. This ingenious machine wasdestroyed in a fire before it could be delivered to Kepler.In 1642, French philosopher and mathematician BlaisePascal invented an improved mechanical calculator. Itsmechanism used a carry mechanism with a weight thatwould drop when a carry was reached, pulling the nextwheel into position. This avoided having to use excessiveforce to carry a digit through several places. Pascal produceda number of his machines and tried to market themto accountants, but they never really caught on.Schikard’s and Pascal’s calculators could only add, butin 1674 German mathematician Gottfried Wilhelm Leibnizinvented a calculator that could work with all the digits ofa number at once, rather than carrying from digit to digit.It worked by allowing a variable number of gear teeth tobe engaged in each digit wheel. The operator could, forexample, set the wheels to a number such as 215, and thenturn a crank three times to multiply it by three, giving aresult of 645. This mechanism, gradually improved, wouldremain fundamental to mechanical calculators for the nextthree centuries.The first calculator efficient enough for general businessuse was invented by an American, Dorr E. Felt, in 1886.His machine, called a Comptometer, used the energy transmittedthrough the number-setting mechanism to performthe addition, considerably speeding up the calculating process.Improved machines by William Burroughs and otherswould replace the arm of the operator with an electricmotor and provide a printing tape for automatically recordinginput numbers and results.Electronic CalculatorsThe final stage in the development of the calculator wouldbe characterized by the use of electronics to replacemechanical (or electromechanical) action. The use of logic

cars and computing 71circuits to perform calculations electronically was first seenin the giant computers of the late 1940s, but this was obviouslyimpractical for desktop office use. By the late 1960s,however, transistorized calculators comparable in size tomechanical desktop calculators came into use. By the 1970s,the use of integrated circuits made it possible to shrink thecalculator down to palm-size and smaller. These calculatorsuse a microprocessor with a set of “microinstructions” thatenable them to perform a repertoire of operations rangingfrom basic arithmetic to trigonometric, statistical, or business-relatedfunctions.The most advanced calculators are programmable bytheir user, who can enter a series of steps (including perhapsdecisions and branching) as a stored program, andthen apply it to data as needed. At this point the calculatorcan be best thought of as a small, somewhat limited computer.However, even these limits are constantly stretched:During the 1990s it became common for students to usegraphing calculators to plot equations. Calculator use isnow generally accepted in schools and even in the taking ofthe Scholastic Aptitude Test (SAT). However, some educatorsare concerned that overdependence on calculators maybe depriving students of basic numeracy, including the abilityto estimate the magnitude of results.Further ReadingAspray, W., ed. Computing Before Computers. Ames: Iowa StateUniversity Press, 1989.The Old Calculator Museum. Links to Interesting Calculator-RelatedSites. Available online. URL: http://www.oldcalculatormuseum.com/links.html. Accessed May 25, 2007.cars and computingDevelopment of automotive technology has tended to beincremental rather than revolutionary. The core “hardware”such as the engine and drive train has changed little overseveral decades, other than the replacement of carburetorswith fuel injection systems, and some improvements inareas such as brake design. On the other hand there havebeen significant improvements in safety features such asseat belts, air bags, and improved crash absorption barriers.In recent years, however, the incorporation of computersin automobile design (see also embedded system) hasled to a number of significant advances in areas such asfuel efficiency, traction/stability, crash response, and driverinformation and navigation. Put simply, cars are becoming“smarter” and are making driving easier and safer.Hybrid cars (such as gas/electric systems) depend oncomputers to sense how the car is being driven and whento augment electric power with the gas engine, as well ascontrolling the feeding of power back into the batteries (asin regenerative braking). In all cars, a general-purpose computingplatform (such as one that has been developed byMicrosoft) can keep drivers up to date on everything fromroad conditions to regular maintenance reminders. Manypurchasers of higher-end vehicles are purchasing servicessuch as OnStar that provide a variety of communication,navigation, and security and safety features. An example ofthe latter includes the automatic sending of a signal whenair bags are deployed. An operator then tries to determine ifassistance is needed, and contacts local dispatchers. Driverswho lock themselves out accidentally can also have theircars unlocked remotely.Another promising approach is to build systems thatcan monitor the driver’s condition or behavior. For example,by analyzing images of the driver’s eyes, facial features,and posture (such as slumping), the car may be able to tellwhen the driver has a high probability of being impaired(sleepy, drunk, or sick) and take appropriate action. (Ofcourse many drivers may object to having their car “watch”them all the time.)Ultimate Smart CarsMuch future progress in car computing will depend on creatingintegrated networking between vehicles and the road. Anadvanced navigation system could take advantage of real-timeinformation being transmitted by the surrounding vehicles.For example, a stalled car would transmit warning messagesto other drivers about the impending obstacle. Vehicles thatsense an oil slick, ice, or other road hazard could also “mark”the location so it can be avoided by subsequent drivers. Dataabout the speed and spacing of traffic could provide real-timeinformation about traffic jams, possibly routing vehicles intoalternative lanes or other roads to reduce congestion andtravel time (see mapping and navigation systems).For many futurists, the ultimate “smart car” is one thatcan drive itself with little or no input from its human occupant.Such cars (with appropriate infrastructure) couldeliminate most accidents, use roads more efficiently, andmaintain mobility for a rapidly aging population. Such eventsas the annual DARPA automated vehicle challenge show considerableprogress being made: Automated cars are alreadydriving cross-country, with the human driver or follow-onvehicle serving only as a safety backup. In 2005 for the firsttime some competitors actually made it across the finishline. “Stanley,” a robotic Volkswagen Touareg designed byStanford University, won the race over an arduous 131-mileThis Mercedes Benz has an integrated navigation system—a featureappearing increasingly in other higher-end cars. (© WolfgangMeier / Visum / The Image Works)

72 cascading style sheetsMojave Desert course, navigating by means of a camera, laserrange finders, and radar. In 2007 the contest entered a moredifficult arena, where the robot vehicles had to deal withsimulated urban traffic, negotiate intersections and trafficcircles, and merge with traffic, all while obeying traffic laws.Meanwhile efforts continue for developing a practicalautomated system that could be used for everyday driving. A“tethered” system using magnetic or radio frequency guidesembedded in the road would reduce the complexity of theon-board navigation system, but would probably require dedicatedroads. A “free” system linked only wirelessly would bemuch more flexible, but would require the ability to visualizeand assess a constantly changing environment and, ifnecessary, make split-second decisions to avoid accidents.Such systems may also feature extensive automatic communication,where cars can provide each other with informationabout road conditions as well as their intended maneuvers.The biggest obstacles to implementation of a fully automatedhighway system may be human rather than technical:the cost of the infrastructure, the need to convince thepublic the system is safe and reliable, and concerns aboutpotential legal liability.Ironically, just as information technology is making carssafer, such activities as cell phone use, text messaging, anduse of in-car entertainment systems seem to be makingdrivers more distracted. Whether cars will get smart fastenough to compensate for increasingly inattentive driversremains an open question.Further ReadingDARPA Grand Challenge. Available online. URL: http://www.darpa.mil/grandchallenge/index.asp. Accessed May 18, 2007.Edwards, John. “Robotic Cars Get Street Smart.” Electronic Design55 (June 29, 2007): 89 ff.Shladover, Steven E. “What if Cars Could Drive Themselves?” Availableonline. URL: http://faculty.washington.edu/jbs/itrans/ahspath.htm. Accessed May 18, 2007.Whelan, Richard. Smart Highways, Smart Cars. Boston: ArtechHouse, 1995.cascading style sheets (CSS)Most word processor users are familiar with the use of stylesin formatting text. Using a built-in style or defining one’sown, particular characteristics can be assigned to the structuralparts of a document, such as headings, lead and bodyparagraphs, quotations, references, and so on. There are severaladvantages to using styles. Once a style is associatedwith an element, the formatting attached to that style canautomatically be applied to all instances of the element. If thewriter decides that, for example, level two headings shouldbe in italics rather than normal font, a simple change to the“head2” style will change all level two headings to italics.Cascading style sheets (CSS) extend this idea to thecreation of Web pages. The style sheet defines the structuralelements of the document and applies the desired formatting.Instead of the main text of the document being filledwith formatting directives (see html), a style sheet is associatedwith the document. When a compatible Web browserloads the page, it also loads the associated style sheet andCascading Style sheets enable the appearance and formatting of aWeb page to be handled separately from the page contents. Specificationsprovided in one sheet can be inherited or modified by othersheets.uses it to determine how the page will be displayed. Inother words, the structure of the document is separatedfrom the details of its presentation. This not only makesit easier to change styles (as with word processing), but italso means that different style sheets can be used to tailorthe document to different viewing situations (for example,viewing in a browser on a handheld PDA).CSS uses a standard “box model” for laying out the presentationof a page. From outside in, the areas are definedas outer edge, margin, border, padding, inner edge, and thecontent area. Styles are applied in an order that dependson the relationship of the affected elements. For example,a style defined for the text body will be inherited by theparagraph, which can then redefine one or more of its elements.Similarly, an emphasis style used within a sentencemight override the paragraph style in turn. It is this flowingof definitions down through the hierarchy of styles that createsthe “cascading” part of CSS.As CSS developed further, separate specifications havebeen provided for different media that can be included ina Web page: speech (to be read by a speech synthesizer),Braille (for a tactile Braille system), Emboss (for Brailleprinting), Handheld (for PDAs and other devices with limiteddisplay space), Print, Projection (for computer projectionor transparencies), Screen, Tty (teletype-like displayswith fixed-width characters), and TV.Further Reading“CSS From the Ground Up.” Web Page Design. Available online.URL: http://www.wpdfd.com/editorial/basics/index.html.Accessed May 19, 2007.Lie, Hakon Wium, and Bert Ros. Cascading Style Sheets: Designingfor the Web. 3rd ed. Addison-Wesley Professional, 2005.

CASE 73Meyer, Eric A. CSS: The Definitive Guide. 3rd ed. Sebastapol, Calif.:O’Reilly, 2007.“Zen Garden: The Beauty of CSS Design.” Available online. URL:http://www.csszengarden.com. Accessed May 19, 2007.CASE (computer-aided software engineering)During the late 1950s and 1960s, software rapidly grew morecomplex—especially operating system software and largebusiness applications. With the typical program consistingof many components being developed by different programmers,it became difficult both to see the “big picture”and to maintain consistent procedures for transferring datafrom one program module to another. As computer scientistsworked to develop sounder principles (see structuredprogramming) it also occurred to them that the power ofthe computer to automate procedures could be used to createtools for facilitating program design and managing theresulting complexity. CASE, or computer-aided softwareengineering, is a catchall phrase that covers a variety of suchtools involved with all phases of development.Design ToolsThe earliest design tool was the flowchart, often drawnwith the aid of a template that could be used to trace thesymbols on paper (see flowchart). With its symbols forthe flow of execution through branching and looping, theflowchart provides a good tool for visualizing how a programis intended to work. However large and complex programsoften result in a sea of flowcharts that are hard torelate to one another and to the program as a whole. Startingin the 1960s, the creation of programs for manipulatingflow symbols made it easier both to design flowcharts andto visualize them in varying levels of detail.Another early tool for program design is pseudocode, alanguage that is at a higher level of abstraction than the targetprogramming language, but that can be refined by addingdetails until the actual program source code has beenspecified (see pseudocode). This is analogous to a writeroutlining the main topics of an essay and then refiningthem into subtopics and supporting details. Attempts weremade to create a well-defined pseudocode that could beautomatically parsed and transformed into compilable languagestatements, but they met with only limited success.During the 1980s and 1990s, the graphics capabilitiesof desktop computers made it attractive to use a visualrather than linguistic approach to program design. Symbols(sometimes called “widgets”) represent program functionssuch as reading data from a file or creating various kindsof charts. A program can be designed by connecting thewidgets with “pipes” representing data flow and by settingvarious characteristics or properties.CASE principles can also be seen in mainstream programmingenvironments such as Microsoft’s Visual Basicand Visual C++, Borland’s Delphi and Turbo C++, and others(see also programming environment). The designapproach begins with setting up forms and placing objects(controls) that represent both user interface items (such asmenus, lists, and text boxes) and internal processing (suchas databases and Web browsers). However these environmentsdo not in themselves provide the ability of full CASEtools to manage complex projects with many components.Analysis ToolsOnce a program has been designed and implementation isunder way, CASE tools can help the programmers maintainconsistency across their various modules. One such tool(now rather venerable) is the data dictionary, which is adatabase whose records contain information about the definitionof data items and a list of program components thatuse each item (see data dictionary). When the definitionof a data item is changed, the data dictionary can providea list of affected components. Database technology is alsoapplied to software design in the creation of a database ofobjects within a particular program, which can be used toprovide more extensive information during debugging.Integration and TrendsA typical CASE environment integrates a variety of toolsto facilitate the flow of software development. This processmay begin with design using visual flowcharting,Many tools are used today to aid the complex endeavor of softwareengineering. Design tools include the traditional flowchart, pseudocode,and design specifications document. Additionally, many systemstoday use interactive, visual layout tools. During the codingand debugging phase, a data dictionary and/or class database canbe used to describe and verify relationships and characteristics ofobjects in the program. Once the code is “built,” a version controlsystem keeps track of what was changed, and various automaticdocumentation features can be used to obtain listings of classes,functions, and other program elements.

74 CD-ROM and DVD-ROM“rapid prototyping,” or other design tools. Once the overalldesign is settled, the developer proceeds to the detailedspecification of objects used by the program and perhapscreates a data dictionary or other databases with informationabout program objects. During the coding process,source control or versioning facilities help log and keeptrack of the changes to code and the succession of newversions (“builds”). While testing the program, an integrateddebugger (see bugs and debugging) can use informationfrom the program components database to helppinpoint errors. As the code is finished, other tools canautomatically generate documentation and other supportingmaterials (see technical writing and documentationof program code).Just as some early proponents of the English-likeCOBOL language proclaimed that professional programmerswould no longer be needed for generating businessapplications, CASE tools have often been hyped as apanacea for all the ills of the software development cycle.Rather than causing the demise of the programmer, however,CASE tools have played an important role in keepingsoftware development viable.In recent years, tools for managing or debugging codehave been supplemented with tools to aid the design processitself (see modeling languages). There are also toolsto aid in refactoring, or the process of reorganizing andclarifying code to make it easier to maintain.In a broader sense, CASE can also include tools for managingthe programming team and its efforts. Even socialnetworking tools (see blogs and blogging and wikis andWikipedia) can play a part in keeping programmers intouch with issues and concerns relating to many differentaspects of a project.Further ReadingCarnegie Mellon Software Engineering Institute. “What Is a CASEEnvironment?” Available online. URL: http://www.sei.cmu.edu/legacy/case/case_whatis.html. Accessed May 18, 2007.CASE Tool Index. Available online. URL: http://www.cs.queensu.ca/Software-Engineering/tools.html. Accessed May 18,2007.Stahl, Thomas, and Markus Voelter. Model-Driven Software Development:Technology, Engineering, Management. New York:Wiley, 2006.CD-ROM and DVD-ROMCD-ROM (compact disk read-only memory) is an opticaldata storage system that uses a disk coated with a thin layerof metal. In writing data, a laser etches billions of tiny pitsin the metal. The data is encoded in the pattern of pits andspaces between them (called “lands”). Unlike the case witha magnetic hard or floppy disk, the data is written in asingle spiral track that begins at the center of the disk. TheCD-ROM drive uses another laser to read the encoded data(which is read from the other side as “bumps” rather thanpits). The drive slows down as the detector (reading head)moves toward the outer edge of the disk. This maintains aconstant linear velocity and allows for all sectors to be thesame size. This system was adapted from the one used forSchematic of the components of a CD drive. The tracking driveand tracking motor move the laser pickup assembly across thespinning disk drive to position it to the correct track. The laserbeam hits the disk surface, reflecting differently from the pits andflat areas (lands). This pattern of differences encodes the data asones and zeros.the audio CDs that largely supplanted phonograph recordsduring the 1980s.A CD can hold about 650 MB of data. By the early 1990s,the CD had become inexpensive and ubiquitous, and it hasnow largely replaced the floppy disk as the medium of softwaredistribution. The relatively large capacity meant thatone CD could replace multiple floppies for a distributionof products such as Microsoft Windows or Word, and italso made it practical to give users access to the entire textof encyclopedias and other reference works. Further, theCD was essential for the delivery of multimedia (graphics,video, and sound) to the desktop, since such applicationsrequire far more storage than is available on 1.44-MB floppydisks. CD drives declined in price from several hundreddollars to about $50, while their speeds have increased by afactor of 30 or more, allowing them to keep up with gamesand other software that needs to read data quickly from thedisk.Recordable CDsIn the late 1990s, a new consumer technology enabled usersto create their own CDs with data or audio tracks. Thecheapest kind, CD-R (Compact Disk Recordable) uses alayer of a dyed material and a thin gold layer to reflect thelaser beam. Data is recorded by a laser beam hitting the dyelayer in precise locations and marking it (in one of severalways, depending on technology). The lengths of marked(“striped”) track and unmarked track together encode thedata.A more versatile alternative is the CD-RW (CompactDisk, Readable/Writeable), which can be recorded on,erased, and re-recorded many times. These disks have alayer made from a mixture of such materials as silver, antimony,and rare earths such as indium and tellurium. The

cellular automata 75mixture forms many tiny crystals. To record data, an infraredlaser beam is directed at pinpoint spots on the layer.The heat from the beam melts the crystals in the targetspot into an amorphous mass. Because the amorphous statehas lower reflectivity than the original crystals, the readinglaser can distinguish the marked “pits” from the surroundinglands. Because of a special property of the material, abeam with a heat level lower than the recording beam canreheat the amorphous material to a point at which it will,upon cooling, revert to its original crystal form. This permitsrepeated erasing and re-recording.DVD-ROMThe DVD (alternatively, Digital Video Disc or Digital VersatileDisc) is similar to a CD, but uses laser light with ashorter wavelength. This means that the size of the pits andlands will be considerably smaller, which in turns meansthat much more data can be stored on the same size disk. ADVD disk typically stores up to 4.7 GB of data, equivalent toabout six CDs. This capacity can be doubled by using bothsides of the disk.The high capacity of DVD-ROMs (and their recordableequivalent, DVD-RAMs) makes them useful for storingfeature-length movies or videos, very large games andmultimedia programs, or large illustrated encyclopedias.The development of high-definition television (HDTV)standards spurred the introduction of higher capacityDVD formats. The competition between Sony’s Blu-Rayand HD-DVD (backed by Toshiba and Microsoft, amongothers) was resolved by 2008 in favor of the former. Blu-Ray offers high capacity (25GB for single layer discs, 50GBfor dual layer).Further ReadingAbout.com “Home Recording: Burning CDs.” Available online. URL:http://homerecording.about.com/cs/burningcds/. Accessed May10, 2007.Taylor, Jim. DVD Demystified. 3rd ed. New York: McGraw-Hill,2006.White, Ron, and Timothy Edward Downs. How Computers Work.8th ed. Indianapolis: Que, 2005.cellular automataIn the 1970s, British mathematician John H. Conwayinvented a pastime called the Game of Life, which was popularizedin Martin Gardner’s column in Scientific American.In this game (better termed a simulation), each cell in a grid“lived” or “died” according to the following rules:1. A living cell remains alive if it has either two orthree living neighbors.2. A dead cell becomes alive if it has three livingneighbors.3. A living cell dies if it has other than two or threeliving neighbors.Investigators created hundreds of starting patterns of livingcells and simulated how they changed as the rules wererepeatedly applied. (Each application of the rules to thecells in the grid is called a generation.) They found, forA screen from a Game of Life simulator called Mirek’s Celebration.(This version runs as a Web browser–accessible Java applet.) Thisand other programs make it easy to experiment with a variety ofLife patterns and track them across hundreds of “generations.”example, that a simple pattern of three living cells in a row“blinked” or switched back and forth between a horizontaland vertical orientation. Other patterns, called “gliderguns” ejected smaller patterns (gliders or spaceships) thattraveled across the grid.The Game of Life is an instance of the general classcalled cellular automata. Each cell operates like a tiny computerthat takes as input the states of its neighbors andproduces its own state as the output. (See also finite statemachine.) The cells can be arranged in one (linear), two(grid), or three dimensions, and a great variety of sets ofrules can be applied to them, ranging from simple variantsof Life to exotic rules that can take into account how long acell has been alive, or subject it to various “environmental”influences.ApplicationsCellular automata theory has been applied to a variety offields that deal with the complex interrelationships of components,including biology (microbe growth and populationdynamics in general), ecology (including forestry), andanimal behavior, such as the flight of birds. (The cues that abird identifies in its neighbors are like the input conditionsfor a cell in a cellular automaton. The “output” would be thebird’s flight behavior.)The ability of cellular automatons to generate a richcomplexity from simple components and rules mimics thedevelopment of life from simple components, and thus cellularautomation is an important tool in the creation andstudy of artificial life. This can be furthered by combininga set of cellular automation rules with a geneticalgorithm, including a mechanism for inheritance ofcharacteristics. Cellular automation principles can also beapplied to engineering in areas such as pattern or imagerecognition.

76 censorship and the InternetIn 2002, computer scientist and mathematician StephenWolfram (developer of the Mathematica program) publisheda book titled A New Kind of Science that undertakes themodest project of explaining the fundamental structure andbehavior of the universe using the principles of cellularautomation. Time will tell whether this turns out to besimply an idiosyncratic (albeit interesting) approach or agenerally useful paradigm.Further ReadingGutowitz, Howard, ed. Cellular Automata. Cambridge, Mass.: MITPress, 1991.“Patterns, Programs, and Links for Conway’s Game of Life.”Available online. URL: http://www.radicaleye.com/lifepage/.Accessed May 28, 2007.Wojtowicz, Mirek. “Welcome to Mirek’s Celebration.: 1D and2D Cellular Automation Explorer.” Available online. URL:http://www.mirwoj.opus.chelm.pl/ca/. Accessed May 28,2007.Wolfram, S. A New Kind of Science. Champaign, Ill.: WolframMedia, 2002.———. Theory and Applications of Cellular Automata. Singapore:World Scientific, 1986.censorship and the InternetGovernments have always to varying degrees concernedthemselves with the content of public media. The growinguse of the Internet for expressive activities (see blogsand blogging and journalism and computers) hasprompted authoritarian governments such as that of Chinato attempt to block “objectionable” material both throughfiltering techniques (see Web filter) and through pressureon service providers. Further, users identified as creators ofbanned content may be subjected to prosecution. Howeverbecause of the Internet’s decentralized structure and theability of users to operate relatively anonymously, Internetcensorship tends to be only partially effective (see anonymityand the Internet).In the democratic West, Internet censorship generallyapplies to only a few forms of content. Attempts to criminalizethe online provision of pornography to minors in the1996 Communications Decency Act have generally beenoverturned by the courts as excessively infringing on theright of adults to access such content. However, a successionof bills seeking to require schools and libraries to installWeb-filtering software culminated in the Children’s InternetProtection Act, which was upheld by the U.S. SupremeCourt in 2003.Another area of potential censorship involves the rightsof bloggers and other nontraditional journalists to post orlink to documents that might be involved with a legal case.Although the term “censorship” is sometimes limitedto government action under criminal law, there areother ways in which Internet content may be restricted.For example, content providers seek to protect their workfrom unauthorized copying or distribution (see intellectualproperty and computing). Civil sanctions can bebrought to bear on violators of copyright or in cases oflibel. However, as with other forms of censorlike activityon the Internet, the targeted behavior can be curtailed onlyto a limited extent.Censorship in ChinaChina has played a central role in the debate over censorship.The rapidly growing Chinese economy offersseemingly unlimited market potential for Internet-basedbusinesses and sellers of software and hardware. Howeverthe Chinese government’s desire to closely control thespread of “subversive” ideas has brought it into collisionwith the liberal ideas shared by many of the Internet’s mostimportant developers.Human rights organizations such as Amnesty Internationalhave criticized online service providers such as Yahoo,Google, and Microsoft for providing the Internet addressesof users who have then been arrested. The companies havebeen accused of putting the potential profits of China’s hugemarket ahead of ensuring free access to information. Generally,the companies say they have no choice but to complywith all local laws and legal demands for information aboutusers. However, critics charge that the technology companieshave often gone well beyond mere compliance to theprovision of sophisticated filtering software for Web sites,blogs, and online chat and discussion groups.The actual extent of censorship in China seems to varyconsiderably, depending on shifting political considerations.The nation’s increasingly sophisticated users oftenfind ways around the censorship, such as through using“proxy servers” that are inside the “Great Firewall” but canconnect to the outside Internet. (Encrypted protocols suchas VPN [virtual private networks] and SSH [secure shell]can also be used, because their content is not detected bymonitoring and filtering software.)Although generally not as highly organized, Internetcensorship can also be found in countries such as Burma(Myanmar), North Korea, Iran, and Syria and to a lesserextent in South Korea and Saudi Arabia.While Internet censorship can be viewed as being ultimatelya political problem, technical realities limit its effectiveness,and curtailing the free exchange of informationand open-ended communication that the Net affords islikely to have economic costs as well.Further ReadingAmnesty International. Available online. URL: http://www.amnestyusa.org. Accessed May 22, 2007.Axelrod-Contrada, Joan. Reno v. ACLU: Internet Censorship. NewYork: Benchmark Books, 2006.Chase, Michael. You’ve Got Dissent! Chinese Dissident Use of theInternet and Beijing’s Counter-Strategies. Santa Monica, Calif.:RAND Corporation, 2002.Herumin, Wendy. Censorship on the Internet: From Filters to Freedomof Speech. Berkeley Heights, N.J.: Enslow, 2004.Reporters without Borders. Handbook for Bloggers and Cyber-Dissidents. Available online. URL: http://www.rsf.org/rubrique.php3?id_rubrique=542. Accessed May 8, 2007.Ringmar, Erik. A Blogger’s Manifesto: Free Speech and Censorship inthe Age of the Internet. London: Anthem Press, 2007.

censorship and the Internet 77While some parents and many schools use filtering software to block Web sites considered to be inappropriate for children, another approach is toprovide a site with “child friendly” material and links. (Image courtesy of the estate of Keith Haring, www.haringkids.com)

78 central processing unitcentral processing unit See CPU.Cerf, Vinton D.(1943– )AmericanComputer ScientistVinton (Vint) Cerf is a key pioneer in the development ofthe packet-switched networking technology that is the basisfor the Internet. In high school, Cerf distinguished himselffrom his classmates by wearing a jacket and a tie and carryinga large brown briefcase, which he later described as“maybe a nerd’s way of being different.” He has a lifelonglove for fantasy and science fiction, both of which exploredifference. Finally, Cerf was set apart by being hearingimpairedas a result of a birth defect. He would overcomethis handicap through a combination of hearing aids andcommunications strategies. And while he was fascinated bychemistry and rocketry, it would be communications, math,and computer science that would form his lifelong interest.After graduating from Stanford in 1965 with a B.S. inmathematics, Cerf worked at IBM as an engineer on itstime-sharing systems, while broadening his background incomputer science. At UCLA he earned on M.S. and then aPh.D. in computer science while working on technologythat could link one computer to another. Soon he was workingwith Len Kleinrock’s Network Measurement Center toplan the ARPA network, a government-sponsored computerlink. In designing software to simulate a network that asyet existed only on paper, Cerf and his colleagues had toexplore the issues of network load, response time, queuing,and routing, which would prove fundamental for the realworldnetworks to come.By the summer of 1968, four universities and researchsites (UCLA, UC Santa Barbara, the University of Utah, andSRI) as well as the firm BBN (Bolt Beranek and Newman)were trying to develop a network. At the time, a customcombination of hardware and software had to be devisedto connect each center’s computer to the other. The hardware,a refrigerator-sized interface called an IMP, was stillin development.By 1970, the tiny four-node network was in operation,cobbled together with software that allowed a user on onemachine to log in to another. This was a far cry from asystem that would allow any computer to seamlessly communicatewith another, however. What was needed on thesoftware end was a universal, consistent language—a protocol—thatany computer could use to communicate withany other computer on the network.In a remarkable display of cooperation, Cerf and hiscolleagues in the Network Working Group set out to designsuch a system. The fundamental idea of the protocol is thatdata to be transmitted would be turned into a stream of“packets.” Each packet would have addressing informationthat would enable it to be routed across the network andthen reassembled back into proper sequence at the destination.Just as the Post Office doesn’t need to know what’sin a letter to deliver it, the network doesn’t need to knowwhether the data it is handling is e-mail, a news article, orsomething else entirely. The message could be assembledand handed over to a program that would know what to dowith it.With the development of what eventually became TCP/IP (Transmission Control Protocol/Internet Protocol) VintCerf and Bob Kahn essentially became the fathers of theInternet we know today (see tcp/ip). As the online worldbegan to grow in the 1980s, Cerf worked with MCI in thedevelopment of its electronic mail system, and then set upsystems to coordinate Internet researchers.In later years, Cerf undertook new initiatives in thedevelopment of the Internet. He was a key founder and thefirst president of the Internet Society in 1992, serving in thatpost until 1995 and then as chairman of the board, 1998–1999. This group seeks to plan for expansion and changeas the Internet becomes a worldwide phenomenon. Cerf’sinterest in science fiction came full circle in 1998 when hejoined an effort at the Jet Propulsion Laboratory (JPL) inPasadena, California. There they are designing an “interplanetaryInternet” that would allow a full network connectionbetween robot space probes, astronauts, and eventualcolonists on Mars and elsewhere in the solar system.In 2005 Cerf joined Google as its “chief Internet evangelist,”where he has the opportunity to apply his imaginationto network applications and access policies. Cerf alsoserved as chairman of the board of the Internet Corporationfor Assigned Names and Numbers (ICANN), a position thathe left in 2007.Cerf has received numerous honors, including the IEEEKobayashi Award (1992), International TelecommunicationsUnion Silver Medal (1995), and the National Medal of Technology(1997). In 2005 Cerf (along with Robert Kahn) wasawarded the Presidential Medal of Freedom, the nation’shighest civilian award.Further Reading“Cerf’s Up.” Personal Perspectives. Available online. URL: http://global.mci.com/ca/resources/cerfs_up/personal_perspective/.Accessed May 28, 2007.Hafner, Katie and Matthew Lyon. Where Wizards Stay Up Late: theOrigins of the Internet. New York: Simon & Schuster, 1996.Henderson, Harry. Pioneers of the Internet. San Diego, Calif.:Lucent Books, 2002.certificate, digitalThe ability to use public key encryption over the Internetmakes it possible to send sensitive information (suchas credit card numbers) to a Web site without electroniceavesdroppers being able to decode it and use it for criminalpurposes (see encryption and computer crime andsecurity). Any user can send information by using a personor organization’s public key, and only the owner of thepublic key will be able to decode that information.However, the user still needs assurance that a site actuallybelongs to the company that it says it does, ratherthan being an imposter. This assurance can be providedby a trusted third party certification authority (CA), suchas VeriSign, Inc. The CA verifies the identity of the appli-

certification of computer professionals 79program for accepting tax returns that are digitally certifiedand signed.Further ReadingAltreya, Mohan, et al. Digital Signatures. Berkeley, Calif.: Osborne/McGraw-Hill, 2002.Brands, Stefan A. Rethinking Public Key Infrastructures and DigitalCertificates. Cambridge, Mass.: MIT Press, 2000.Feghhi, Jalal, and Peter Williams. Digital Certificates: AppliedInternet Security. Reading, Mass.: Addison-Wesley, 1998.Digital certification relies upon public key cryptography and theexistence of a trusted third party, the Certificate Authority (CA).First a business properly identifies itself to the CA and receives adigital certificate. A consumer can obtain a copy of the business’sdigital certificate and use it to obtain the business’s public key fromthe CA. The consumer can now send encrypted information (suchas a credit card number) to the business.cant and then provides the company with a digital certificate,which is actually the company’s public key encryptedtogether with a key used by the CA and a text message.(This is sometimes called a digital signature.) When a userqueries the Web site, the user’s browser uses the CA’s publickey to decrypt the certificate holder’s public key. Thatpublic key is used in turn to decrypt the accompanyingmessage. If the message text matches, this proves that thecertificate is valid (unless the CA’s private key has somehowbeen compromised).The supporting technology for digital certification isincluded in a standard called Secure Sockets Layer (SSL),which is a protocol for sending encrypted data across theInternet. SSL is supported by leading browsers such asMicrosoft Internet Explorer and Netscape. As a result, digitalcertification is usually transparent to the user, unlessthe user is notified that a certificate cannot be verified.Digital certificates are often attached to software such asbrowser plug-ins so the user can verify before installationthat the software actually originates with its manufacturerand has not been tampered with (such as by introduction ofa virus).The use of digital certification is expanding. For example,VeriSign and the federal General Services Administration(GSA) have begun an initiative called ACES (AccessCertificates for Electronic Services) that will allow citizensa secure means to send information (such as loan applications)and to view benefits records. The IRS has a pilotcertification of computer professionalsUnlike medicine, the law, or even civil engineering, thecomputer-related fields do not have legally required certification.Given society’s critical dependence on computersoftware and hardware for areas such as infrastructuremanagement and medical applications, there have beenpersistent attempts to require certification or licensing ofsoftware engineers. However, the fluid nature of the informationscience field would make it difficult to decide whichapplication areas should have entry restrictions.At present, a variety of academic degrees, professionalaffiliations, and industry certificates may be considered inevaluating a candidate for a position in the computing field.Academic and Professional CredentialsThe field of computer science has the usual levels of academiccredentials (baccalaureate, master’s, and doctoraldegrees), and these are often considered prerequisites foran academic position or for industry positions that involveresearch or development in areas such as robotics or artificialintelligence. For business-oriented IT positions, abachelor’s degree in computer science or information systemsmay be required or preferred, and candidates whoalso have a business-oriented degree (such as an MBA) maybe in a stronger position. However, degrees are generallyviewed only as a minimum qualification (or “filter”) beforeevaluating experience in the specific application or platformin question. While not a certification, membership in themajor professional organizations such as the Associationfor Computing Machinery (ACM) and Institute for Electricaland Electronic Engineers (IEEE) can be viewed as partof professional status. Through special interest groups andforums, these organizations provide computer professionalswith a good way to track emerging technical developmentsor to broaden their knowledge.In the early years of computing and again, in the microcomputerindustry of the 1980s, programming experienceand ability were valued more highly than academic credentials.(Bill Gates, for example, had no formal college trainingin computer science.) In general, degree or certificationrequirements tend to be imposed as a sector of the informationindustry becomes well defined and established in thecorporate world. For example, as local area networks cameinto widespread use in the 1980s, certifications were developedby Microsoft, Novell, and others. In turn, collegesand trade schools can train technicians, using the certificateexaminations to establish a curriculum, and numerousbooks and packaged training courses have been marketed.

80 CGIIn a newly emerging sector there is less emphasis oncredentials (which are often not yet established) and moreemphasis on being able to demonstrate knowledge throughhaving actually developed successful applications. Thus, inthe late 1990s, a high demand for Web page design and programmingemerged, and a good portfolio was more importantthan the holding of some sort of certificate. However ase-commerce and the Web became firmly established in thecorporate world, the cycle is beginning to repeat itself ascertification for webmastering and e-commerce applicationsis developed.Industry CertificationsSeveral major industry certifications have achieved widespreadacceptance.Since 1973, the Institute for Certification of ComputingProfessionals (ICCP) has offered certification based on generalprogramming and related skills rather than mastery ofparticular platforms or products. The Associate ComputingProfessional (ACP) certificate is offered to persons who havea basic general knowledge of information processing andwho have mastered one major programming language. Themore advanced Certified Computing Professional (CCP) certificaterequires several years of documented experience inareas such as programming or information systems management.Both certificates also require passing an examination.A major trade group, the Computing Technology IndustryAssociation (CompTIA) offers the A+ Certificate forcomputer technicians. It is based on passing a Core ServiceTechnician exam focusing on general hardware-related skillsand a DOS/Windows Service Technician exam that emphasizesknowledge of the operating system. The exams areupdated regularly based on required job skills as assessedthrough industry practices.Networking vendor Novell offers the Certified NetWareEngineer (CNE) certificate indicating mastery of the installation,configuration, and maintenance of its networkingproducts or its GroupWise messaging system. The CertifiedNetWare Administrator (CNA) certificate emphasizes systemadministration.Microsoft offers a variety of certificates in its networkingand applications development products. The best knownis the Microsoft Certified System Engineer (MCSE) certificate.It is based on a series of required and elective examsthat cover the installation, management, configuration, andmaintenance of Windows 2000 and other Microsoft networks.A number of other vendors including Cisco Systems andOracle offer certification in their products. Given the everchangingmarketplace, it is likely that most computer professionalswill acquire multiple certificates as their careeradvances.Further ReadingCompTIA Certification Page. Available online. URL: http://www.comptia.org/. Accessed May 28, 2007.Institute for Certification of Computing Professionals. Availableonline. URL: http://www.iccp.org. Accessed May 28, 2007.“MCSE Guide.” Available online. URL: http://www.mcseguide.com/Novell Education Page. Available online. URL: http://www.novell.com/training/certinfo/howdoi.htm. Accessed May 28, 2007.CGI (common gateway interface)By itself, a Web page coded in HTML is simply a “static”display that does not interact with the user (other than forthe selection of links). (See html, dhtml, and xhtm.) ManyWeb services, including online databases and e-commercetransactions, require that the user be able to interact withthe server. For example, an online shopper may need tobrowse or search a catalog of CD titles, select one or morefor purchase, and then complete the transaction by providingcredit card and other information. These functions areprovided by “gateway programs” on the server that canaccess databases or other facilities.One way to provide interaction with (and through) a Webpage is to use the CGI (common gateway interface). CGI is afacility that allows Web browsers and other client programsto link to and run programs stored on a Web site. The storedprograms, called scripts, can be written in various languagessuch as JavaScript or PHP (see scripting languages) andplaced in a cgi-bin folder on the Web server.The CGI script is referenced by an HTML hyperlink onthe Web page, such asMyScript Or more commonly, it is included in an HTML formthat the user fills in, then clicks the Submit button. Ineither case, the script executes. The script can then processthe information the user provided on the form, andreturn information to the user’s Web browser in the formCGI or Common Gateway Interface allows a program linked toa Web page to obtain data from databases and use it to generateforms to be shown on users’ Web browsers. For example, a CGIprogram can link a Web user to a “shopping cart” and inventorysystem for online purchases.

characters and strings 81of an HTML document. The script can perform additionalfunctions such as logging the user’s query for marketingpurposes.The complexity of Web features and the heavy load onservers have prompted a number of strategies for servingdynamic content more efficiently. Traditionally, each timea CGI request is passed to the URL for a script, the appropriatelanguage interpreter must be loaded and initialized.However, modern Web servers such as Apache have built-inmodules for commonly used scripting languages such asPHP, Perl, Python, and Ruby. This allows the Web serverto run the script directly without the overhead of starting anew interpreter process.A more fundamental shift in implementation is thedevelopment of methods to tie together DHTML and XMLwith a document model and scripting languages to allowfor dynamic changes in page content without having toreload the page (see Ajax).Note: the acronym CGI can also stand for “computergeneratedimagery” (see computer graphics).Further Reading“A Guide to HTML and CGI Scripts.” Available online. URL: http://snowwhite.it.brighton.ac.uk/~mas/mas/courses/html/html.html. Accessed May 30, 2007.Hamilton, Jacqueline D. CGI Programming 101. Houston, Tex.:CGI101.com, 2000. (First six chapters are available freeonline at URL: http://www.cgi101.com/book/.) AccessedAugust 12, 2007.“The Most Simple Intro to CGI.” Available online. URL: http://bignosebird.com/prcgi.shtml. Accessed August 12, 2007.characters and stringsWhile the attention of the first computer designers focusedmainly on numeric calculations, it was clear that much ofthe data that business people and others would want tomanipulate with the new machines would be textual innature. Billing records, for example, would have to includecustomer names and addresses, not just balance totals.The “natural” representation of data in a computer is asa series of two-state (binary) values, interpreted as binarynumbers. The solution for representing text (letters of thealphabet, punctuation marks, and other special symbols) isto assign a numeric value to each text symbol. The result isa character code, such as ASCII (American Standard Codefor Information Interchange), which is the scheme usedmost widely today. (Another system, EBCDIC (ExtendedBinary-Coded Decimal Interchange Code) was used duringthe heyday of IBM mainframes, but is seldom used today.)The seven-bit ASCII system is compact (using one byteof memory to store each character), and was quite suitablefor early microcomputers that required only the basicEnglish alphabet, punctuation, and a few control characters(such as carriage return). In an attempt to use charactersto provide simple graphics capabilities, an “extendedASCII” was developed for use on IBM-compatible PCs.This used eight bits, increasing the number of charactersavailable from 128 to 256. However, the use of bitmappedgraphics in Windows and other operating systemsmade this version of ASCII unnecessary. Instead, the ANSI(American National Standards Institute) eight-bit characterset used the additional character positions to store avariety of special symbols (such as fractions and the copyrightsymbol) and various accent marks used in Europeanlanguages.Table of 7-Bit ASCII Character CodesThe following are control (nonprinting) characters:0 Null (nothing)7 Bell (rings on an old teletype; beeps on most PCs)8 Backspace9 Tab10 Line feed (goes to next line without changing columnposition)13 Carriage return (positions to beginning of next line)26 End of file27 [Esc] (Escape key)The characters with codes from 32 to 127 produce printablecharacters.32 [space] 64 @ 96 `33 ! 65 A 97 a34 “ 66 B 98 b35 # 67 C 99 c36 $ 68 D 100 d37 % 69 E 101 e38 & 70 F 102 f39 ‘ 71 G 103 g40 ( 72 H 104 h41 ) 73 I 105 i42 * 74 J 106 j43 + 75 K 107 k44 ‘ 76 L 108 l45 - 77 M 109 m46 . 78 N 110 n47 / 79 O 111 o48 0 80 P 112 p49 1 81 Q 113 q50 2 82 R 114 r51 3 83 S 115 s52 4 84 T 116 t53 5 85 U 117 u54 6 86 V 118 v55 7 87 W 119 w56 8 88 X 120 x57 9 89 Y 121 y58 : 90 Z 122 z59 ; 91 [ 123 {60 < 92 \ 124 |61 = 93 ] 125 }62 > 94 ^ 126 ~63 ? 95 - 127 [delete]

82 characters and stringsAs computer use became more widespread internationally,even 256 characters proved to be inadequate. A newstandard called Unicode can accommodate all of the world’salphabetic languages including Arabic, Hebrew, and Japanese(Kana Unicode schemes can also be used to encodeideographic languages (such as Chinese) and languagessuch as Korean that use syllabic components. At presenteach ideograph has its own character code, but Unicode 3.0includes a scheme for describing ideographs through theircomponent parts (radicals). Most modern operating systemsuse Unicode exclusively for character representation. However,support in software such as Web browsers is far fromcomplete, though steadily improving. Unicode also includesmany sets of internationally used symbols such as thoseused in mathematics and science. In order to accommodatethis wealth of characters, Unicode uses 16 bits to store eachcharacter, allowing for 65,535 different characters at theexpense of requiring twice the memory storage.Programming with StringsBefore considering how characters are actually manipulatedin the computer, it is important to realize that what thebinary value such as 1000001 (decimal 65) stored in a byteof memory actually represents depends on the context givento it by the program accessing that location. If the programdeclares an integer variable, then the data is numeric. If theprogram declares a character (char) value, then the data willbe interpreted as an uppercase “A” (in the ASCII system).Most character data used by programs actually representswords, sentences, or longer pieces of text. Multiplecharacters are represented as a string. For example, in traditionalBASIC the statement:NAME$ = “Homer Simpson”declares a string variable called NAME$ (the $ is a suffixindicating a string) and sets its value to the character string“Homer Simpson.” (The quotation marks are not actuallystored with the characters.)Some languages (such as BASIC) store a string in memoryby first storing the number of characters in the string,followed by the characters, with one in each byte of memory.In the family of languages that includes C, however,there is no string type as such. Instead, a string is stored asan array of char. Thus, in C the preceding example mightlook like this:char Name [20] = “Homer Simpson”;This declares Name as an array of up to 20 characters, andinitializes it to the string literal “Homer Simpson.”An alternative (and equivalent) form is:char * Name = “Homer Simpson”;Here Name is a pointer that returns the memory locationwhere the data begins. The string of characters “HomerSimpson” is stored starting at that location.Unlike the case with BASIC, in the C languages, thenumber of characters is not stored at the beginning of thedata. Rather, a special “null” character is stored to mark theend of the string.Programs can test strings for equality or even for greaterthan or less than. However, programmers must be carefulto understand the collating sequence, or the order given tocharacters in a character set such as ASCII. For example thetestIf State = “CA”will fail if the current value of State is “ca.” The lowercasecharacters have different numeric values than their uppercasecounterparts (and indeed must, if the two are to bedistinguished). Similarly, the expression:“Zebra” < “aardvark”is true because uppercase Z comes before lowercase “a” inthe collating sequence.Programming languages differ considerably in theirfacilities for manipulating strings. BASIC includes built-infunctions for determining the length of a string (LEN) andfor extracting portions of a string (substrings). For examplegiven the string Test consisting of the text “Test Data,” theexpression Right$ (Test, 4) would return “data.”Following their generally minimalist philosophy, theC and C++ languages contains no string facilities. Rather,they are provided as part of the standard library, which canbe included in programs as needed. In the following littleprogram:#include #include void main (){char String1[20];char String2[20];strcpy (String1, “Homer”);strcpy (String2, “Simpson”);//Concatenate string2 to the end of string1strcat (String1, String2);cout String1

chatterbots 83known for its sophisticated pattern-matching and patternprocessing capabilities. A similar language, Icon, is widelyused for specialized string-processing tasks today. Manyprogrammers working with textual data in the UNIX environmenthave found that the awk and Perl languages areeasier to use than C for extracting and manipulating datafields. (See awk and Perl.)Further ReadingGillam, Richard. Unicode Demystified: A Practical Programmer’sGuide to the Encoding Standard. Reading, Mass.: Addison-Wesley, 2002.Korpela, Jukka. Unicode Explained. Sebastapol, Calif.: O’Reilly,2006.A Tutorial on Character Code Issues. Available online. URL: http://www.cs.tut.fi/~jkorpela/chars.html. Accessed May 31, 2007.Unicode Consortium. Unicode Standard, Version 5.0. 5th ed. Reading,Mass.: Addison-Wesley, 2006.chat, onlineIn general terms, to “chat” is to communicate in real timeby typing messages to other online users who can immediatelytype messages in reply. It is this conversational immediacythat distinguishes chat services from conferencingsystems or bulletin boards.Commercial ServicesMany PC users have become acquainted with chattingthrough participating in “chat rooms” operated by onlineservices such as America Online (AOL). A chat room isa “virtual space” in which people meet either to socializegenerally or to discuss particular topics. At their best,chat rooms can develop into true communities whose participantsdevelop long-term friendships and provide oneanother with information and emotional support (see virtualcommunity).However, the essentially anonymous character of chat(where participants often use “handles” rather than realnames) that facilitates freedom of expression can also providea cover for mischief or even crime. Chat rooms haveacquired a rather lurid reputation in the eyes of the generalpublic. There has been considerable public concern aboutchildren becoming involved in inappropriate sexual conversation.This has been fueled by media stories (sometimesexaggerated) about children being recruited into face-tofacemeetings with pedophiles. AOL and other online serviceshave tried to reduce such activity by restricting onlinesex chat to adults, but there is no reliable mechanism fora service to verify its user’s age. A chat room can also besupervised by a host or moderator who tries to prevent“flaming” (insults) or other behavior that the online serviceconsiders to be inappropriate.Distributed ServicesFor people who find commercial online services to be tooexpensive or confining, there are alternatives available forjust the cost of an Internet connection. The popular InternetRelay Chat (IRC) was developed in Finland by JarkkoOikarinen in the late 1980s. Using one of the freely availableclient programs, users connect to an IRC server, whichin turn is connected to one of dozens of IRC networks.Users can create their own chat rooms (called channels).There are thousands of IRC channels with participants allover the world. To participate, a user simply joins a channeland sees all messages currently being posted by otherusers of the channel. In turn, the user’s messages are postedfor all to see. While IRC uses only text, there are nowenhanced chat systems (often written in Java to work with aWeb browser) that add graphics and other features.There are many other technologies that can be usedfor conversing via the Internet. Some chat services (suchas Cu-SeeMe) enable participants to transmit their images(see videoconferencing and Web cam). Voice can alsobe transmitted over an Internet connection (see voip). For avery pervasive form of “ad hoc” textual communication, seetexting and instant messaging.Further ReadingMcDonald, Wayne. Chat Rooms in Wonderland. Frederick, Md.:PublishAmerica, 2005.Ploch, Nicolas. “A Short IRC Primer.” Available online. URL: http://www.irchelp.org/irchelp/ircprimer.html. Accessed June 1,2007.Wasuki, Dennis D. Self-Games and Body-Play: Personhood in OnlineChat and Cybersex. Bern: Peter Lang, 2003.Weverka, Peter. Mastering ICQ: the Official Guide. Dulles, Va.: ICQPress, 2001.chatterbotsThe famous Turing test (see Turing, Alan M.) proposesthat if a human is unable to reliably distinguish messagesfrom a computer from those of another person, thecomputer program involved can at least be provisionallydeclared to be “intelligent.” The advent of textual communicationvia the Internet (see texting and instant messaging)has afforded a variety of ways to attempt to meetthis challenge. Programs that mimic human conversationalstyles have come to be known as “chatterbots.”The prototypical chatterbot was ELIZA, developed byJoseph Weizenbaum in the mid-1960s (see Weizenbaum,Joseph). ELIZA mimicked a form of nondirective psychotherapyin which the therapist echoes or plays off of the client’sstatements as a form of gentle encouragement and validation.Thus if one types, “My father didn’t really like me,” ELIZAmight reply, “Tell me more about your father.” Althoughprimitive, ELIZA once inadvertently fooled an executive intothinking he was exchanging messages with Weizenbaum.Other classic chatterbots include Parry, designed to mimic aparanoid, and the story-generating Racter.The first online chatterbot, Julia, was created by MichaelMauldin in 1994. (Mauldin also coined the term chatterbot.)More sophisticated chatterbots include Jabberwocky, whichincludes learning algorithms, and ELLA, which applieslinguistic principles to produce more realistic speech (seenatural language processing). On a negative note, somechatterbots have been designed to enter chat rooms andspew advertising (spambots) or even to elicit personal information(see identity theft and phishing and spoofing).

84 chess and computersOne of the best known and most versatile modern chatterbotsis ALICE (Artificial Linguistic Internet Computer Entity),developed by Richard Wallace. ALICE does much more thansimply echo statements; it includes an elaborate parser andsentence generator and specialized scripts for initiating orresponding to conversational gambits. ALICE can even telllies and spread “gossip” that it learns from other users.In the following dialog ALICE seems to be able torespond appropriately:Human: Are you intelligent?ALICE: I am highly intelligent. I have many intellectual functions.Human: How do you know you are intelligent?ALICE: By introspection.However the illusion breaks down as the matter ispressed further and the bot uses a “deflection” strategy:Human: What were you thinking while you said that?ALICE: I was minding my own business.Human: How do you feel about being interrogated in this way?ALICE: The opposite of not being interrogated in this way.Still, with more than 25,000 conversation templatesstored in XML files that are modifiable by the user, ALICEhas repeatedly won the Loebner Contest, a modern versionof the Turing test.Although many are created as programming exercisesor for amusement, chatterbots embody principles that areimportant in artificial intelligence research, including naturallanguage processing and machine learning (see artificialintelligence). Techniques first developed withchatterbots can contribute to the creation of programsdesigned to provide answers to users’ questions or otherforms of assistance (see software agent).moves for the computer chess player, the possible repliesof the opponent to each move, the possible next moves bythe computer, and so on for as many half moves or “plies”as possible. The moves would be evaluated by a “minimax”algorithm that would find the move that best improves thecomputer’s position despite the opponent’s best play.The fundamental problem with the brute force is the“combinatorial explosion”: Looking ahead just three moves(six plies) would involve evaluating more than 700,000,000positions. This was impractical given the limited computingpower available in the 1950s. Shannon realized thisand decided that a successful chess program would have toincorporate principles of chess strategy that would enable itto quickly recognize and discard moves that did not showa likelihood of gaining material or improving the position(such as by increasing control of center squares). As a resultof this “pruning” approach, only the more promising initialmoves would result in the program looking ahead—butthose moves could be analyzed much more deeply.The challenge of the pruning approach is the need toidentify the principles of good play and codify them in sucha way that the program can use them reliably. Progresswas slow at first—programs of the 1950s and 1960s couldscarcely challenge an experienced amateur human player,let alone a master. A typical program would play a mixtureof reasonable moves, odd-looking but justifiable moves,and moves that showed the chess version of “nearsightedness.”By the 1970s, however, computing power was rapidlyincreasing, and a new generation of programs such as Chess4.0 from Northwestern University abandoned most pruningtechniques in favor of brute-force searches that could nowextend further ahead. In practice, each programmer chose aparticular balance between brute force and pruning-selectionFurther ReadingA.L.I.C.E. Artificial Intelligence Foundation. Available online.URL: http://www.alicebot.org/. Accessed April 27, 2007.Chatterbot Central (The Simon Laven Page). Available online.URL: http://www.simonlaven.com/. Accessed April 27, 2007.Loebner Prize. Available online. URL: http://www.loebner.net/Prizef/loebner-prize.html. Accessed April 27, 2007.chess and computersWith simple rules but endless permutations, chess has fascinatedmillions of players for hundreds of years. Whenmechanical automatons became fashionable in the 18thcentury, onlookers were intrigued by “the Turk,” a chessplayingautomaton. While the Turk was eventually shownto be a hoax (a human player was hidden inside), the developmentof the electronic digital computer in the mid-20thcentury provided the opportunity to create a true automaticchess player.In 1950 Claude Shannon outlined the two basic strategiesthat would be used by future chess-playing programs.The “brute force” strategy would examine the possibleIn the 18th century the Turk, a mechanical chess player, astonishedonlookers. Although the original Turk was a fraud (a small humanplayer was hidden inside), the modern computer chess programFritz 9 pays its homage by simulating its predecessor. (Fritz 9,Chessbase GmbH, www.chessbase.com)

chip 85techniques. An ever-increasing search base could be combinedwith evaluation of particularly important positionalfeatures (such as the possibility of creating a “passed pawn”that could be promoted to a queen).By the end of the 1970s, International Master DavidLevy was still beating the best chess programs of the time(defeating Chess 4.7 in 1978). A decade later, however, Levywas defeated in 1989 by Deep Thought, a program thatran on a specially designed computer that could examinehundreds of millions of positions per move. That same yearWorld Champion Garry Kasparov decisively defeated themachine. In 1996, however, the successor program DeepBlue (sponsored by IBM) shocked the chess world by beatingKasparov in the first game of their match. Kasparovwent on to win the match, but the following year an updatedversion of Deep Blue defeated Kasparov 3 1/2–2 1/2. A computerhad arguably become the strongest chess player in theworld. As a practical matter, the match brought IBM invaluablepublicity as a world leader in supercomputing.Chess and AIThe earliest computer chess theorists such as Claude Shannonand Alan Turing saw the game as one potential wayto demonstrate true machine intelligence. Ironically, bythe time computers had truly mastered chess, the artificialintelligence (AI) community had concluded that masteringthe game was largely irrelevant to their goals. AI pioneersHerbert Simon and John McCarthy have referred to chessas “the Drosophila of AI.” By this they mean that, like theubiquitous fruit flies in genetics research, chess became aneasy way to measure computer prowess. But what was itmeasuring? The dominant brute-force approach was morea measure of computing power than the application of suchAI techniques as pattern recognition. (There is, however,still some interest in writing chess programs that “think”more like a human player.) In recent years there has beensome interest in programming computers to play the Asianboard game Go, where positional and structural elementsplay a greater role than in chess. However, even the latestgeneration of Go programs seem to be relying more on astatistical approach than a deep conceptual analysis.Further ReadingComputer History Museum. “Mastering the Game: A Historyof Computer Chess.” Available online. URL: http://www.computerhistory.org/chess/. Accessed April 28, 2007.Hsu, Feng-Hsiung. Behind Deep Blue: Building the Computer ThatDefeated the World Chess Champion. Princeton, N.J.: PrincetonUniversity Press, 2004.Levy, David, and Monty Newborn. How Computers Play Chess.New York: Computer Science Press, 1991.Shannon, Claude E. “Programming a Computer for PlayingChess.” Philosophical Magazine 41 (1950): 314. Available fromComputer History Museum. Available online. URL: http://archive.computerhistory.org. Accessed April 27, 2007.chipAs early as the 1930s, researchers had begun to investigatethe electrical properties of materials such as siliconand germanium. Such materials, dubbed “semiconductors,”were neither a good conductor of electricity (such as copper)nor a good insulator (such as rubber). In 1939, oneresearcher, William Shockley, wrote in his notebook “It hastoday occurred to me that an amplifier using semiconductorsrather than vacuum [tubes] is in principle possible.” Inother words, if the conductivity of a semiconductor couldbe made to vary in a controlled way, it could serve as anelectronic “valve” in the same way that a vacuum tube canbe used to amplify a current or to serve as an electronicswitch.The needs of the ensuing wartime years made it evidentthat a solid-state electronic device would bring manyadvantages over the vacuum tube: compactness, lowerpower usage, higher reliability. Increasingly complex electronicequipment, ranging from military fire control systemsto the first digital computers, further underscored theinadequacy of the vacuum tube.In 1947, William Shockley, along with John Bardeenand Walter Brattain, invented the transistor, a solid-stateelectronic device that could replace the vacuum tube formost low-power applications, including the binary switchingthat is at the heart of the electronic digital computer.But as the computer industry strove to pack more processingpower into a manageable volume, the transistor itselfbegan to appear bulky.Starting in 1958, two researchers, Jack Kilby of TexasInstruments and Robert Noyce of Fairchild Semiconductor,independently arrived at the next stage of electronicminiaturization: the integrated circuit (IC). The basic ideaof the IC is to make semiconductor resistors, capacitors,and diodes, combine them with transistors, and assemblethem into complete, compact solid-state circuits. Kilby didthis by embedding the components on a single piece of germaniumcalled a substrate. However, this method requiredthe painstaking and expensive hand-soldering of the tinygold wires connecting the components. Noyce soon cameup with a superior method: Using a lithographic process, hewas able to print the pattern of wires for the circuit onto aboard containing a silicon substrate. The components couldthen be easily connected to the circuit. Thus was born theubiquitous PCB (printed circuit board). This technologywould make the minicomputer (a machine that was roughlyrefrigerator-sized rather than room-sized) possible duringthe 1960s and 1970s. Besides the PCBs being quite reliablecompared to hand-soldered connections, a failed boardcould be easily “swapped out” for a replacement, simplifyingmaintenance.From IC to ChipThe next step to the truly integrated circuit was to form theindividual devices onto a single ceramic substrate (muchsmaller than the printed circuit board) and encapsulatethem in a protective polymer coating. The device then functionedas a single unit, with input and output leads to connectit to a larger circuit. However, the speed of this “hybridIC” is limited by the relatively large distance between components.The modern IC that we now call the “computerchip” is a monolithic IC. Here the devices, rather than being

86 chipsetattached to the silicon substrate, are formed by altering thesubstrate itself with tiny amounts of impurities (a processcalled “doping”). This creates regions with an excess ofelectrons (n-type, for negative) or a deficit (p-type for positive).The junction between a p and an n region functionsas a diode. More complex arrangements of p and n regionsform transistors. Layers of transistors and other devices canbe formed on top of one another, resulting in a highly compactintegrated circuit. Today this is generally done usingoptical lithography techniques, although as the separationbetween components approaches 100 nm (nanometers, orbillionths of a meter) it becomes limited by the wavelengthof the light used.In computers, the IC chip is used for two primary functions:logic (the processor) and memory. The microprocessorsof the 1970s were measured in thousands of transistorequivalents, while chips such as the Pentium and Athlonbeing marketed by the late 1990s are measured in tensof millions of transistors (see microprocessor). Meanwhile,memory chips have increased in capacity from the4K and 16K common around 1980 to 256 MB and more.In what became known as “Moore’s law,” Gordon Moorehas observed that the number of transistors per chip hasdoubled roughly every 18 months.Future TechnologiesAlthough Moore’s law has proven to be surprisingly resilient,new technologies will be required to maintain thepace of progress.In January 2007, Intel and IBM separately announced aprocess for making transistors out of the exotic metal hafnium.It turns out that hafnium is much better than the traditionalsilicon at preventing power leakage (and resultinginefficiency) through layers that are only about five atomsthick. Hafnium transistors can also be packed more closelytogether and/or run at a higher speed.Another approach is to find new ways to connect thetransistors so they can be placed closer together, allowingsignals to travel more quickly and thus provide fasteroperation. Hewlett-Packard (HP) is developing a way toplace the connections on layers above the transistors themselves,thus reducing the space between components. Thescheme uses two layers of conducting material separated bya layer of insulating material that can be made to conductby having a current applied to it. Although promising, theapproach faces difficulties in making the wires (only about100 atoms thick) reliable enough for applications such ascomputer memory or microprocessors.Ultimately, direct fabrication at the atomic level (seenanotechnology) will allow for the maximum densityand efficiency of computer chips.Further ReadingBaker, R. Jacob, Harry W. Li, and David E. Boyce. CMOS CircuitDesign, Layout and Simulation. New York: IEEE Press, 1998.Saint, Christopher and Judy Saint. IC Layout Basics. New York:McGraw-Hill, 2001.Semiconductor Industry Association. Available online. URL:http://www.sia-online.org/home.cfm. Accessed August 13,2007.Thompson, J. M. T., ed. Visions of the Future: Physics and Electronics.New York: Cambridge University Press, 2001.chipsetIn personal computers a chipset is a group of integratedcircuits that together perform a particular function. Systempurchasers generally think in terms of the processor itself(such as a Pentium III, Pentium IV, or competitive chipsfrom AMD or Cyrix). However they are really buying asystem chipset that includes the microprocessor itself (seemicroprocessor) and often a memory cache (which may bepart of the microprocessor or a separate chip—see cache)as well as the chips that control the memory bus (whichconnects the processor to the main memory on the motherboard—seebus.) The overall performance of the systemdepends not just on the processor’s architecture (includingdata width, instruction set, and use of instruction pipelines)but also on the type and size of the cache memory,the memory bus (RDRAM or “Rambus” and SDRAM) andthe speed with which the processor can move data to andfrom memory.In addition to the system chipset, other chipsets on themotherboard are used to support functions such as graphics(the AGP, or Advanced Graphics Port, for example), driveconnection (EIDE controller), communication with externaldevices (see parallel port, serial port, and USB), andconnections to expansion cards (the PCI bus).At the end of the 1990s, the PC marketplace had chipsetsbased on two competing architectures. Intel, whichoriginally developed an architecture called Socket 7, hasswitched to the more complex Slot-1 architecture, whichis most effective for multiprocessor operation but offersthe advantage of including a separate bus for accessing thecache memory. Meanwhile, Intel’s main competitor, AMD,has enhanced the Socket 7 into “Super Socket 7” and isoffering faster bus speeds. On the horizon may be completelynew architecture. In choosing a system, consumersare locked into their choice because the microprocessor pinsockets used for each chipset architecture are different.Further ReadingIntel. “Desktop Chipsets.” Available online. URL: http://www.intel.com/products/desktop/chipsets/. Accessed June 6, 2007.“Motherboards.” Available online. URL: http://www.motherboards.org/index.html. Accessed June 6, 2007.Walrath, Josh. “Chipsets Today and Tomorrow.” ExtremeTech.Available online. URL: http://www.extremetech.com/article2/0,1697,1845493,00.asp. Accessed June 6, 2007.Church, Alonzo(1903–1995)AmericanMathematicianBorn in Washington, D.C., mathematician and logicianAlonzo Church made seminal contributions to the fundamentaltheory of computation. Church was mentored bynoted geometer Oswald Veblen and graduated from Prince-

88 classclassA class is a data type that combines both a data structureand methods for manipulating the data. For example, astring class might consist of an array to hold the charactersin the string and methods to compare strings, combinestrings, or extract portions of a string (see charactersand strings).As with other data types, once a class is declared,objects (sometimes called instances) of the class can becreated and used. This way of structuring programs iscalled object-oriented programming because the classobject is the basic building block (see object-orientedprogramming).Object-oriented programming and classes provide severaladvantages over traditional block-structured languages.In a traditional BASIC or even Pascal program, there isno particular connection between the data structure andthe procedures or functions that manipulate it. In a largeprogram one programmer might change the data structurewithout alerting other programmers whose code assumesthe original structure. On the other hand, someone mightwrite a procedure that directly manipulates the internaldata rather than using the methods already provided. Eithertransgression can lead to hard-to-find bugs.With a class, however, data and procedures are boundtogether, or encapsulated. This means that the data in aclass object can be manipulated only by using one of themethods provided by the class. If the person in chargeof maintaining the class decides to provide an improvedimplementation of the data structure, as long as the dataparameters expected by the class methods do not change,code that uses the class objects will continue to functionproperly.A class encapsulates (or hides) its internal information from therest of the program. When the program calls MyCircle.GetPosition,the GetPosition member function of the MyCircle Circle class objectretrieves the private Position data and sends it back to the callingstatement, where it is assigned to the variable P. Private data cannotbe directly accessed or changed by an outside caller.Most languages that use classes also allow for inheritance,or the ability to create a new class that derives dataand methods from a “parent” class and then modifies orextends them. For example, a class that provides supportfor 3D graphics could be derived from an existing class for2D graphics by adding data items such as a third (Z) coordinateand replacing a method such as “line” with a versionthat works with three coordinates instead of two.In designing classes, it is important to identify theessential features of the physical situation you are trying tomodel. The most general characteristics can be put in the“base class” and the more specialized characteristics wouldbe added in the inherited (derived) classes.Classes and C++Classes first appeared in the Simula 67 language, whichintroduced the terms class and object (see Simula). As thename suggests, the language was used mainly for simulationand modeling, but its object-oriented ideas wouldprove influential. The Smalltalk language developed atXerox PARC in the 1970s ran on the Alto computer, whichpioneered the graphic user interface that would becomepopular with the Macintosh in the 1980s. Smalltalk usedclasses to build a seamless and extensible operating systemand environment (see Smalltalk).However it was Bjarne Stroustrup’s C++ language thatbrought classes into the programming mainstream (seec++). C++ essentially builds its classes by extending theC struct so that it contains both methods (class functions)and data. An access mechanism allows class variables to bedesignated as completely accessible (public), which is rare,accessible only by derived classes (protected), or accessibleonly within the class itself (private). The creation of a newobject of the class is specified by a constructor function,which typically allocates memory for the object and setsinitial default values. The corresponding destructor functionfrees up the memory when the object no longer exists.C++ allows for multiple inheritance, meaning that a classcan be derived from more than one parent or base class.The language also provides two powerful mechanisms forextending functionality. The first, called virtual functions,allows a base class and its derived classes to have functionsbased on the same interface. For example, a base graphicsclass might have virtual line, circle, setcolor, and otherfunctions that would be implemented in derived classes for3D objects, 3D solid objects, and so on. When the programcalls a method in a virtual class, the compiler automaticallysearches the class’s “family tree” until it finds the class thatcorresponds to the actual data type of the object.A template specifies how to create a class definitionbased on the type of data to be used by the class. In otherwords, where a regular procedure takes and manipulatesdata parameters and returns data, a template takes dataparameters and returns a definition of a class for workingwith that data (see template).Other languages of the 1980s and later have embracedclasses. Examples include descendants of the Algol familyof languages (see Pascal, Ada, c++’s close cousin—Java),and Microsoft’s Visual Basic. (There is even a version ofCOBOL with classes.)

90 clock speedSinclair, Joseph T., and Mark S. Merkow. Thin Clients ClearlyExplained. San Francisco: Morgan Kaufmann, 2000.clock speedThe transfer of data within the microprocessor and betweenthe microprocessor and memory must be synchronized toensure that the data needed to execute each instruction isavailable when the flow of execution has reached an appropriatepoint. This synchronization is accomplished by movingdata in intervals that correspond to the pulses of thesystem clock (a quartz crystal). This is done by sendingcontrol signals that tell the components of the processorand memory when to send or wait for data. Thus, if themicroprocessor is the heart of the computer, the clock is theheart’s pacemaker. Because most devices cannot run at thesame pace as the processor, circuits in various parts of themotherboard create secondary control signals that run atvarious ratios of the actual system clock speed.The following table shows the speed of various systemcomponents in relation to the system clock rate. Althoughthe example uses a 600-MHz clock, the ratios will generallyhold for faster processors.Device speed RelationshipProcessor 600 System bus * 4.5System(Memory) Bus 133 (depends on multiplier)Level 2 Cache 300 Processor / 2AGP 66 System bus / 2PCI bus 33 System bus / 4Microprocessors are rated according to the frequency(that is, number of pulses per second) of their associatedclock. For example, a 1.2-GHz Pentium IV processor has1.2 billion (giga-) pulses per second. It follows that all otherthings being equal, the higher a processor’s clock frequency,the more instructions it can process per second. An alternativeway to rate processors is according to the number of astandard type of instruction that it can process per second,hence MIPS (millions of instructions per second).The relationship between clock speed and processorperformance is not as simple as the preceding might imply,however. Each processor is designed with circuits that canmove data at a certain rate. In some cases a processor canbe run at a higher clock rate than specified (this is calledoverclocking), but then reliability comes into question.Also, the actual processing power of a processor dependson many other factors. If a processor implements instructionsin its microcode that are more efficient for handlingcertain operations (such as floating point math or graphicsrendering), applications that depend on these operationsmay run faster on one processor than on another, even ifthe two processors run at the same clock speed. The speedof the system bus (which connects the processor to theRAM memory) also affects the speed at which data can befetched, processed, and stored. A processor with a clockspeed of 733 MHz should perform better on a motherboardwith a bus speed of 133 MHz than on one with a bus speedof only 100 MHz.Speed is “sexy” in marketing terms, so the major chipmanufacturers always tout their fastest chips. However, thedifference in speed between, for example, a 2.2-GHz versionof a processor and a 2.0-GHz version may be unnoticeableto the user of all but the most processor-intensive applications(such as image processing). Indeed, if the system withthe slower chip has a faster bus, faster memory (such asRDRAM), or a larger processor cache (see cache) it maywell outperform the one with a faster chip.Another reason for caution in interpreting clock speedis that many recent PCs have two or even four processors(see multiprocessing). Performance in such systemsis likely to depend at least as much on optimization of theoperating system and applications as on any multiple of rawclock speed. This trend to multicore CPUs is also seen as analternative to any substantial increase in processor speed,because higher speeds bring increasing concerns about heatand power usage.In PCs the term “clock” can also refer to the battery-powered“real-time” clock that provides a timing interval thatcan be accessed by the operating system and applications.Further ReadingClock speed resources. TechRepublic. Available online. URL:http://search.techrepublic.com.com/search/clock+speed.html?t=11& s=0&o=0. Accessed June 6, 2007.“Understanding System Memory and CPU Speeds.” Available online.URL: http://www.directron.com/fsbguide.html. Accessed June6, 2007.“What Is CPU Overclocking?” Available online. URL: http://www.webopedia.com/DidYouKnow/Computer_Science/2005/overclocking.asp. Accessed June 6, 2007.COBOLCommon Business-Oriented Language was developed underthe impetus of a 1959 Department of Defense initiative tocreate a common language for developing business applicationsthat centered on the processing of data from files. (Themilitary, after all, was a “business” whose inventory controland accounting needs dwarfed those of all but the largestcorporations.) At the time, the principal business-orientedlanguage for mainframe computers was FLOW-MATIC, alanguage developed by Grace Hopper’s team at Remington-Rand UNIVAC and limited to that company’s computers(see Hopper, Grace Murray). The first COBOL compilersbecame available in 1960, and the American NationalStandards Institute (ANSI) issued a standard specificationfor the language in 1968. Expanded standards were issuedin 1974 and 1985 (COBOL-74 and COBOL-85) with a newstandard issued in 2002.The committee that outlined the language that wouldbecome COBOL focused on making program statementsresemble declarative English sentences rather than themathematical expressions used by FORTRAN for scientificprogramming. COBOL’s designers hoped that accountants,managers, and other business professionals could quicklymaster the language, reducing if not removing the need for

COBOL 91professional programmers. (This theme of “programmingwithout programmers” would recur with regard to otherlanguages such as RPG, BASIC, and various database systems,always with limited success.)Program StructureA COBOL program as a whole resembles a business form inthat it is divided into specific sections called divisions, eachwith required and optional items.The Identification division simply identifies the programmerand gives some information about the program:IDENTIFICATION DIVISION.PROGRAM-ID WEEKLY REPORT.AUTHOR JAMES BRADLEY.DATE-WRITTEN DECEMBER 10, 2000.DATE-COMPILED DECEMBER 12, 2000.REMARKS THIS IS AN EXAMPLE PROGRAM.The Environment division contains specifications aboutthe environment (hardware) for which the program willbe compiled. In some cases (for example, microcomputerversions of COBOL) it may not be needed. In other cases, itmight simply have a Configuration section that specifies themachine to be used:ENVIRONMENT DIVISION.CONFIGURATION SECTION.SOURCE-COMPUTER IBM-370.OBJECT-COMPUTER IBM-370.(The reason for the separate source and object computers isthat programs were sometimes compiled on one computerfor use on another, often smaller, one.)In some cases, the Environment Division must alsoinclude an Input-Output section that specifies devices andfiles that will be used by the program. For example:INPUT-OUTPUT SECTION.FILE-CONTROL.SELECT STUDENT-FILE ASSIGN TO READERSELECT STUDENT-LISTING ASSIGN TO LOCAL-PRINTERThe Data division gives a description of the data recordsand other items that will be processed by the program.It is roughly comparable to the declarations of variablesin languages such as Pascal, C, or BASIC. Since COBOLfocuses on the processing of file records and the formattingof reports, it tends to have fewer data types than manyother languages, but it makes it easier to describe the kindsof data structures commonly used in business applications.For example, it is easy to describe records that have fieldsand subfields by using level numbers to indicate the relationship:DATA DIVISION.FILE SECTION.FD INFILELABEL RECORDS ARE OMITTED.01 STUDENT-DATA.02 STUDENT-ID PIC 999999.02 STUDENT-NAME.03 LAST-NAME PIC X(15).03 INITIAL PIC X.03 FIRST-NAME PIC X(10).02 GPA PIC 9.99The “PIC” or picture clause specifies the type of data(using 9’s and a decimal point for numbers and X for text)and the length. In addition to specifying the input records,the Data division often includes items that specify the formatof the lines of output that are to be printed.The Procedure division provides the statements thatperform the actual data manipulation. Procedures can beorganized as subroutines (roughly equivalent to proceduresor functions on other languages). Some sample procedurestatements are:READ STUDENT-DATA INTO STUDENT-WORK-RECORDAT END MOVE ‘E’ TO PROC-FLAG-STGO TO EXIT-PRINTADD 1 TO TOTAL-STUDENT-RECORDSMathematical expressions can be computed using aCompute statement:COMPUTE GPA = TOTAL-GRADES / CLASSESBranching (if) statements are available, and looping isprovided by the Perform statement, for example:PERFORM 100-PRINT-LINEUNTIL LINES-FL IS EQUAL TO ‘E’(As with older versions of BASIC, subroutines are numbered.)Impact and ProspectsFrom the 1960s through the 1980s, COBOL became theworkhorse language for business applications for mainframeand mid-size computers, and it is still widely usedtoday. (The concerns about possible problems at the endof the century often involved older programs written inCOBOL, see y2k problem.) The main line of programminglanguage evolution bypassed COBOL and went throughAlgol (a contemporary of COBOL) and on into Pascal, C,and other block-structured languages (see also structuredprogramming).Some modern versions of COBOL have incorporatedlater developments in structured programming (such asmodularization) and even object-oriented design. COBOLhas also shown considerable versatility in accommodatingmodern development frameworks, including Microsoft.NETas well as processing now-ubiquitous XML data. Nevertheless,usage of COBOL continues to decline slowly as developersincreasingly turn to languages such as C++, scriptinglanguages, or database development systems.Further ReadingBivar de Oliveria, Rui. The Power of COBOL: For Systems Developersof the 21st Century. Charleston, S.C.: BookSurge, 2006.COBOL Portal. Available online. URL: http://www.cobolportal.com. Accessed June 8, 2007.

92 codecMurcah, Mike, Anne Prince, and Raul Menendez. Murach’s MainframeCOBOL. Fresno, Calif.: Murach and Associates, 2004.Sammet, J. E. “The Early History of COBOL,” in History of ProgrammingLanguages. Wexelblat, R. L., ed., 199–276. NewYork: Academic Press, 1985.codecShort for “coder/decoder,” a codec is essentially an algorithmfor encoding (and compressing) a stream of data fortransmission, and then decoding and decompressing it atthe receiving end. Usually the data involved representsaudio or video content (see streaming). Typically the datais being downloaded from a Web site to be played on apersonal computer or portable player (see multimedia andmusic and video players, digital).A codec is described as “lossy” if some of the originalinformation is lost in the compression process. It thenbecomes a question of whether the loss in quality is perceivedby the user as significant. A codec that preserves allthe information needed to re-create the original file is “lossless.”For most purposes, the much greater size of the losslessversion of a file is not worth the (often imperceptible)increase in quality or fidelity.A codec is usually used in connection with a “containerformat” that specifies how the encoded data is to be storedCodecAACAIFFALACAVIFLACCMP3MPEGOgg VorbisQuick TimeReal Audio andand RealVideoRIFFVorbisWAVWMAWMVContainer Descriptionadvanced audio coding; developed as asuccessor to MP3 and especially usedby Apple (iTunes, iPod, iPhone, etc.)audio interchange file format; audiocontainer format for transferring contentbetween applicationsApple lossless audio codecaudio video interleave; video and moviescontainer formatfree lossless audio codec; music, opensource, losslessactually MPEG-3, probably the mostcommon music codecMoving Picture Experts Group; video,movies, audio (four layers MPEG-1through MPEG-4)music, open source (often used on Linuxsystems)Apple multimediadeveloped by RealNetworks for manyplatformsresource interchange file format; containerformatfree, open-source audio codec (often usedin Linux)Windows audio format (usuallyuncompressed)Windows media audioWindows media videoin a file. Often a container can hold more than one datastream and even more than one kind of media (such asvideo and audio). When one refers to a Windows WAV file,for example, one is actually referring to a container.Most of the popular codecs and file formats are proprietary,which creates something of a dilemma for users whoprefer open-source solutions. However, while most Linuxdistributions do not include support for formats such asMP3 out of the box, distributions such as Ubuntu are nowmaking it easier for users to choose nonsupported proprietarycodecs if desired.The preceding table lists some codecs likely to beencountered by program developers and consumers.Further ReadingAudio Files. Available online. URL: http://www.fileinfo.net/filetypes/audio. Accessed September 3, 2007.Harte, Lawrence. Introduction to MPEG. Fuquay Varina, N.C.:Althos Publishing, 2006.Rathbone, Andy. MP3 for Dummies. 2nd ed. New York: HungryMinds, 2001.Richardson, Iain E. G. Video Codec Design: Developing Image andVideo Compression Systems. New York: Wiley, 2002.Roberts-Breslin, Jan. Making Media: Foundations of Sound andImage Production. Boston: Focal Press, 2003.Thurott, Paul. PC Magazine Windows XP Digital Media Solutions.Indianapolis: Wiley, 2005.Video Files. Available online. URL: http://www.fileinfo.net/filetypes/video. Accessed September 3. 2007.cognitive scienceCognitive science is the study of mental processes such asreasoning, memory, and the processing of perception. Itis necessarily an interdisciplinary approach that includesfields such as psychology, linguistics, and neurology. Theimportance of the computer to cognitive science is that itoffers a potential nonhuman model for a thinking entity.The attempts at artificial intelligence over the past 50 yearshave used the insights of cognitive science to help deviseartificial means of reasoning and perception. At the sametime, the models created by computer scientists (such asthe neural network and Marvin Minsky’s idea of “multipleintelligent agents”) have in turn been applied to the studyof human cognition (see Minsky, Marvin Lee and neuralnetwork).Since the late 19th century, technological metaphorshave been used to describe the human mind. The neuronsand synapses of the brain were compared to the multitudeof switches in a telephone company central office. Theinvention of digital computers seemed to offer an even morecompelling correspondence between neurons and their electrochemicalstates and the binary state of a vacuum tube ortransistor. It is only a small further step to assert that humanmental processes can be reduced in principle to computation,albeit a very complex tapestry of computation. Variousschools of popular psychology and personal improvementhave offered simplistic images of the human mind sufferingfrom “bad programming” that can be debugged or manipulatedthrough various processes. The simulation of someforms of reasoning and language construction by AI pro-

color in computing 93grams certainly suggests that there are fruitful analogiesbetween human and machine cognition, but constructionof a detailed model that would be applicable to both humanand artificial intelligences seemed almost as distant in thescience fictional year of 2001 as it was when Alan Turingand other AI pioneers first considered such questions in theearly 1950s (see Turing, Alan Mathison).Symbolists and ConnectionistsUnlike standard computer memory cells, neurons can havehundreds of potential connections (and thus states). If ahuman being is a computer, it must be to a considerableextent an analog computer, with input in the form of levels ofvarious chemicals and electrical impulses. Yet in the 1980s,Allen Newell and Herbert Simon suggested that the “output”of human mental experience can be effectively mapped asrelationships between symbols (words, images, and so forth)that correspond to physical states (this is called the PhysicalSymbol System Hypothesis). If so, then such a symbol systemwould be “computable” in the Turing-Church sense (seecomputability and complexity). Working from the computerend, AI researchers have created a variety of programsthat seem to “understand” restricted universes of discoursesuch as a table with variously shaped blocks upon it or“story frames” based upon common human activities suchas eating in a restaurant. Thus, symbol manipulators can atleast appear to be intelligent.The “connectionists,” however, argue that it is not symbolicrepresentations that are significant, but the structurewithin the mind that generates them. By designing neuralnetworks (or distributed processor networks) the connectionistshave been able to create systems that produceapparently intelligent behavior (such as pattern recognition)without any reference to symbolic representation.Critiques have also come from philosophers. HerbertDreyfus has pointed out that computers lack the body,senses, and social milieu that shape human thought. Thatmachines can generate symbolic representations accordingto some sort of programmed rules doesn’t make the machinetruly intelligent, at least not in the way experienced byhuman beings. John Searle responded to the famous Turingtest (which states that if a human being can’t distinguish acomputer’s conversation from a human’s, the computer isarguably intelligent). Searle’s “Chinese Room” imagines aroom in which an English-speaking person who knows noChinese is equipped with a program that lets him manipulateChinese words in such a way that a Chinese observerwould think he knows Chinese. Similarly, Searle argues,the computer might act “intelligently,” but it doesn’t reallyunderstand what it is doing.Advances in cognitive science will both influence anddepend on developments in brain research (especially theconnection between physical states and cognition) and inartificial intelligence.Further ReadingBechtel, William, and Adele Abrahamson. Connectionism and theMind: Parallel Processing, Dynamics, and Evolution in Networks.2nd ed. Cambridge, Mass.: Blackwell, 2000.“Cognitive Science.” Stanford Encyclopedia of Philosophy. Availableonline. URL: http://plato.stanford.edu/entries/cognitivescience/.Accessed June 10, 2007.Horgan, Terence, and John Tienson. Connectionism and the Philosophyof Psychology. Cambridge, Mass.: MIT Press, 1996.Sobel, Carolyn. Cognitive Science: An Interdisciplinary Approach.New York: McGraw-Hill, 2001.Thagard, Paul. Mind: Introduction to Cognitive Science. 2nd ed.Cambridge, Mass.: MIT Press, 2005.color in computingWith the exception of a few experimental systems, colorgraphics first became widely available only with the beginningsof desktop computers in the late 1970s. The firstmicrocomputers were able to display only a few colors(some, indeed, displayed only monochrome or grayscale).Today’s PC video hardware has the potential to displaymillions of colors, though of course the human eye cannotdirectly distinguish colors that are too close together. Thereare several important schemes that are used to define a“color space”—that is, a range of values that can be associatedwith physical colors.RGBOne of the simplest color systems displays colors as varyingintensities of red, green, and blue. This corresponds to theelectronics of a standard color computer monitor, whichuses three electron guns that bombard red, green, and bluephosphors on the screen. A typical RGB color scheme uses8 bits to store each of the red, green, and blue componentsfor each pixel, for a total of 24 bits (16,777,216 colors). The32-bit color system provides the same number of colors butincludes 8 bits for alpha, or the level of transparency. Thenumber of bits per pixel is also called the bit depth or colordepth.CMYKCMYK stands for cyan, magenta, yellow, and black. Thisfour component color system is standard for most types ofcolor printing, since black is an ink color in printing but issimply the absence of color in video. One of the more difficulttasks to be performed by desktop publishing softwareis to properly match a given RGB screen color to the correspondingCMYK print color. Recent versions of MicrosoftWindows and the Macintosh operating system include aCMS (color matching system) to support color matching.PalettesAlthough most color schemes now support thousands ormillions of colors, it would be wasteful and inefficient touse three or four bytes to store the color of each pixel inmemory. After all, any given application is likely to needonly a few dozen colors. The solution is to set up a palette,which is a table of (usually 256) color values currently inuse by the program. (A palette is also sometimes called aCLUT, or color lookup table.) The color of each pixel canthen be stored as an index to the corresponding value in thepalette.

94 COMcommon object request broker architectureSee corba.A color lookup table (CLUT) or palette can be used to store the colorsactually being used by an image. Here up to 256 colors can beselected out of millions of possibilities.The user of a paint program can select a palette fromthe full range of colors available from the operating system.Many color graphics image formats such as GIF (graphicinterchange format) store a palette of the colors used bythe image. When converting an image that has more colorsthat the palette can hold, various algorithms can be used tochoose a palette that preserves as much of the color rangeas possible.Further Reading“Color” Webopedia. Available online. URL: http://www.webopedia.com/Graphics/Color/. Accessed June 10, 2007.Drew, John, and Sarah Meyer. Color Management: A ComprehensiveGuide for Graphic Designers. East Sussex, U.K.: RotoVision,2005.“Introduction to Color and Color Management Systems.” AppleComputer Developer Connection. Available online. URL:http://developer.apple.com/documentation/mac/ACI/ACI46.html. Accessed June 10, 2007.Koren, Norman. “Color Management and Color Science: Introduction.”Available online. URL: http://www.normankoren.com/color_management.html. Accessed June 10, 2007.COM (common object model) See Microsoft.net.common gateway interface See cgi.compatibility and portabilityThe computers of the 1940s were each hand built andunique. When the first commercial models were developed,such as the UNIVAC and the first IBM mainframes, thequestion of compatibility was born. Broadly speaking, compatibilityis the degree to which a program or hardwaredevice designed for one system can work with or run onanother.The designers of high-level languages usually intend thata source program written using the proper language syntaxwill compile and run on any system for which a compiler isavailable. However, there are many factors that can destroycompatibility. For example, if one machine stores the bytesof a numeric value from least significant to most significantwhile another does it in the opposite order, program codethat depends on directly referencing memory locations willgive the wrong results on one machine or another. Similarly,standard data sizes such as “integer” might be 16 bitson one system and 32 bits on another.Language designers can minimize such problems byseparating hardware-related issues from the language itself,as is the case with C and C++. A program is then linkedwith standard libraries implemented for each hardware oroperating system environment.Manufacturers often design newer models of their computersso they are “upwardly compatible” with existingmodels. This means that a program written for the smallermachine should run correctly on the new, larger one. Thisis of obvious benefit to users who do not want to haveto rewrite their software every time they upgrade theirmachine. Often, however, such systems are not “downwardlycompatible”—a program written for the new, largermachine may rely on features or architectural characteristicsthat are not available on the older, smaller machines.Sometimes a “compatibility mode” can be specified for acompiler or operating system. This restricts the use of featuresto those available on the older system.Compatibility is also important with regard to software.Generally speaking, a newer version of a program such as aword processor will be able to read files that were originallycreated by a previous version, although this may not be truefor more than a few versions back. However, files saved fromthe newest version may well be incompatible with older versions,because they contain formatting or other informationthat is not understandable by the earlier version. Sometimesan intermediate format (for example, see rtf, or Rich TextFormat) can be used to transfer files between otherwiseincompatible systems.Compatibility between vendors can be an importantcompetitive issue. If a developer wants to enter a marketwhere one or two products are viewed as industry standards,the new product will have to be compatible with atleast most files created by the dominant products. A technicallysuperior product can thus be a market disaster if it isnot compatible with the industry standard. In areas (such

compiler 95as graphics file formats) where there are many alternativesin widespread use, most programs will support multipleformats.PortabilityPortability is the ability to adapt software or hardware toa wide variety of platforms (that is, computer systems oroperating systems). Developers want their products to beportable so they can adapt to an often rapidly changingmarketplace. A typical strategy for portability is to choosea language that is in widespread use and a compiler thatis certified as meeting the ANSI or other standard for thelanguage. The program should be written in such a way thatit makes as few assumptions as possible about hardwaredependentmatters such as how data is stored in memory. Itis also sometimes possible to use standard frameworks thatprovide the same functions in several different operatingsystems such as Windows, Macintosh, and UNIX.However, there is a tradeoff: The more “generic” a programis made in order to be portable, the less optimized itwill be for any given hardware or operating environment.The program will also not be able to take advantage of thespecial features of a given operating system, which may putit at a competitive disadvantage compared to the “nativeversion” of a program. (This is particularly true with Windows,given that operating system’s dominance in personalcomputing.)The Internet has in general been a force for portability.The Java language, in particular, is designed to be platformindependent.A Java program is compiled into an intermediatelanguage called byte code, which is interpreted orcompiled by a “virtual machine” program running on eachplatform. Thus, the same Java program should run in abrowser under Windows, Macintosh, or UNIX (see java).for addition, rather than some binary instruction code). Anassembler is essentially a compiler that needs to make onlyrelatively simple translations, because assembly language isstill at a relatively low level.Moving to higher-level languages with relatively English-likestatements makes programming easier and makesprograms easier to read and maintain. However, the taskof translating high-level statements to machine-level codebecomes a more complex multistep process.The Compilation ProcessCompilers are traditionally thought of as having a “frontend” that analyzes the source code (high-level languagestatements) and a “back end” that generates the appropriatelow-level code. The front end processing begins with lexicalanalysis. The compiler scans the source program looking formatches to valid tokens as defined by the language. A tokenis any word or symbol that has meaning in the language,Further ReadingHakuta, Mitsuari, and Masato Ohminami. “A Study of SoftwarePortability Evaluation.” Journal of Systems and Software 38(August 1997): 145–154.Robinson, John. “Delivering on Standards: Balancing Portabilityand Performance.” Available online. URL: http://ipdps.cc.gatech.edu/1999/papers/it2.pdf. Accessed August 11, 2007.“Software Portability Home Page.” Available online. URL: http://www.cs.wvu.edu/~jdm/research/portability/home.html.Accessed June 11, 2007.compilerA compiler is a program that takes as input a programwritten in a source language and produces as output anequivalent program written in another (target) language.Usually the input program is in a high-level language suchas C++ and the output is in assembly language for the targetmachine (see assembler).Compilers are useful because programming directlyin low-level machine instructions (as had to be done withthe first computers) is tedious and prone to errors. Use ofassembly language helps somewhat by allowing substitutionof symbols (variable names) for memory locations andthe use of mnemonic names for operations (such as “add”A parse tree showing how an assignment statement in Pascal canbe broken down into its component parts. Here ID stands for a variablename, or identifier. An expression can be broken all the waydown to a single number.

96 compilersuch as a keyword (reserved word) such as if or while.Next, the tokens are parsed or grouped according to therules of the language. The result of parsing is a “parse tree”that resolves statements into their component parts. Forexample, an assignment statement may be parsed into anidentifier, an assignment operator (such as =), and a value tobe assigned. The value in turn may be an arithmetic expressionthat consists of operators and operands.Parsing can be done either “bottom up” (finding theindividual components of the statement and then linkingthem together) or “top down” (identifying the type of statementand then breaking it down into its component parts).A set of grammatical rules specifies how each construct(such as an arithmetic expression) can be broken into (orbuilt up from) its component parts.The next step is semantic analysis. During this phase theparsed statements are analyzed further to make sure theydon’t violate language rules. For example, most languagesrequire that variables must be declared before they are referencedby the program. Many languages also have rules forwhich data types may be converted to other types when thetwo types are used in the same operation.The result of front-end processing is an intermediate representationsomewhere between the source statements andmachine-level statements. The intermediate representationis then passed to the back end.Code Generation and OptimizationThe process of code generation usually involves multiplepasses that gradually substitute machine-specific code anddata for the information in the parse tree. An importantconsideration in modern compilers is optimization, whichis the process of substituting equivalent (but more efficient)constructs for the original output of the front end. Forexample, an optimizer can replace an arithmetic expressionwith its value so that it need not be repeatedly calculatedwhile the program is running. It can also “hoist out” aninvariant expression from a loop so that it is calculated onlyonce before the loop begins. On a larger scale, optimizationcan also improve the communication between differentparts (procedures) of the program.The compiler must attempt to “prove” that the change itis making in the program will never cause the program tooperate incorrectly. It can do this, for example, by tracingthe possible paths of execution through the program (suchas through branching and loops) and verifying that eachpossible path yields the correct result. A compiler that istoo “aggressive” in making assumptions can produce subtleprogram errors. (Many compilers allow the user to controlthe level of optimization, and whether to optimize for speedor for compactness of program size.) During development,a compiler is often set to include special debugging code inthe output. This code preserves potentially important informationthat can help the debugging facility better identifyprogram bugs. After the program is working correctly, itwill be recompiled without the debugging code.The final code generation is usually accomplished byusing templates that match each intermediate constructionwith a construction in the target (usually assembly)Compilation is a multistep process. Lexical analysis breaks statementsdown into tokens, which are then parsed and subjected tosemantic analysis. The resulting intermediate representation can beoptimized before the final object code is generated.language, plugging items in as specified by the template.Often a final step, called peephole optimization, examinesthe assembly code and identifies redundancies or, if possible,replaces a memory reference so that a faster machineregister is used instead.In most applications the assembly code produced bythe compiler is linked to code from other source files. Forexample, in a C++ applications class definitions and codethat use objects from the classes may be compiled separately.Also most languages (such as C and C++) have operatingsystem-specific libraries that contain commonly usedsupport functions.

computability and complexity 97As an alternative to bringing the external code into thefinal application file, code can be “dynamically linked” tolibraries that will be accessed only while the program isbeing run. This eliminates the waste that would occur ifseveral running applications are all using the same standardlibrary code (see library, program).In mainframes compilers were usually invoked as part ofa batch file using some form of JCL (job control language).With operating systems such as UNIX and MS-DOS a programcalled make is typically used with a file that specifiesthe compiler, linker, and other options to be used to compilethe program. Modern visually oriented developmentenvironments (such as those provided by products such asVisual C++) allow options to be set via menus or simply byselecting from a variety of typical configurations.Compiler design has become a highly complex field.A modern compiler is developed using a variety of tools(including packaged parsers and lexical analyzers), andinvolves a large team of programmers. Nevertheless, theprinciples of compiler design are emphasized in the generalcomputer science curriculum because when a studentunderstands even a simplified compiler in detail, he or shehas become acquainted both with important ideas (suchas language grammar, parsing, and optimization) and withmany levels of understanding computer architecture.Further ReadingAho, Alfred V., Ravi Sethi, and Jeffrey D. Ullman. Compiler Design:Principles, Techniques, and Tools. 2nd ed. Reading, Mass.:Addison-Wesley, 2006.“Compiler Connection: A Resource for Compiler Developers andThose Who Use Their Products and Services.” Availableonline. URL: http://www.compilerconnection.com/. AccessedAugust 12, 2007.Grune, Dick, et al. Modern Compiler Design. New York: Wiley, 2000.component object model (Microsoft) SeeMicrosoft .net.computability and complexityInterestingly, one of the important discoveries of 20th-centurymathematics is that certain kinds of problems werenot computable. The Turing machine and Alonzo Church’slambda calculus provided equivalent models that could beused to determine what was computable (see Turing, AlanMathison, and Church, Alonzo). Thus far, the equivalencebetween the Turing machine and actual computershas held. That is, any decision problem (a problem with a“yes” or “no” answer) that can in theory be solved with aTuring machine can in theory be solved by any actual computer.Conversely, if a problem can’t be solved by a Turingmachine, it cannot be solved by a computer, no matter howpowerful.The Halting ProblemThe Halting problem is a classic example of an undecidableproblem (or proposition). The problem is this: Given anycomputer program, can you determine whether the programwill halt (end) given any input? There are specificprograms that can be shown to halt on particular inputs.For example, this program:If Input = 99 then end.will obviously halt on an input of 99. But to decide whethera determination can be made for any program for any input,it is only necessary to construct a logical paradox. Assumethat there is a program P that halts if and only if it receivesinput D. (Further assume that the program can print somethingto let you know that it has halted.)Since the input can be anything, you can let it be a copyof the program itself. The question then becomes: Will theprogram halt if it is given a copy of itself? Create a procedure(or subroutine) called HaltTest, and define it as:If P halts then print “Halted”else print “Didn’t Halt.”Now create another program called Main. It calls Halt-Test and is programmed to do the opposite of what HaltTestindicates.If HaltTest (Main) prints “Yes” then loopforever else halt;But what happens when Main is run? It calls HaltTest,giving itself (Main) as input. If HaltTest halts, then Mainloops forever. But if HaltTest doesn’t halt, then Main halts.But this means that Main halts if it doesn’t halt, and doesn’thalt if it halts. This paradox shows that whether Main haltsis undecidable.The undecidability of the Halting problem has someinteresting implications. For example, it means that thereis no way a computer can reliably determine that a programdoes not contain an infinite loop. Also, because a mathematicalfunction f(x) is equivalent to a computer programwith input x, similar proofs by contradiction can be writtento show that it can’t be decided whether a program will halton all inputs (which is equivalent to f(x) being defined forall x.) Nor can it be decided whether two different programs(or mathematical functions) are equivalent for all x.It is important to realize that a program (or function)being undecidable in all cases doesn’t necessarily mean thatit can’t be decided for some cases (or inputs). Indeed, theanswer of the Halting Problem for any given input can bedetermined by feeding that particular input to the program,which will either halt or run forever.ComplexityIf a problem turns out to be computable, we then enterthe realm of complexity—the analysis of how much computationwill be required (see algorithm). Sometimes adesigner can devise a significantly faster algorithm for agiven problem (such as finding prime factors or sorting).However, other problems appear to have complexity basedon an exponential expression, meaning that they becomemore complex much more rapidly as the input increases.An example is the Traveling Salesman Problem, which is to

98 computer-aided design and manufacturingfind the most efficient route for a person traveling to a numberof cities to visit each of the cities.Mathematicians therefore categorize the complexity ofproblems as P (solvable in a polynomial period of time),EXP (requiring an exponential time), or an intermediateclass NP, which means “nondeterministic polynomial.” AnNP problem is one that can be solved in polynomial time ifone is able to guess (and then verify) the answer. The TravelingSalesman Problem is believed to be in the NP class.While abstruse, the study of computability and complexityhas important implications for practical applications.For example, determining the complexity of a cryptographicalgorithm can help determine whether the resultingencryption is strong enough to withstand the efforts of afeasible attacker.Further ReadingBoolos, George S., John P. Burgess, and Richard C. Jeffrey. Computabilityand Logic. 4th ed. New York: Cambridge UniversityPress, 2002.Jones, Neil D. Computability and Complexity: From a ProgrammingPerspective. Cambridge, Mass.: MIT Press, 1997.Sipser, Michael. Introduction to the Theory of Computation. 2nd ed.Boston: Thomson Course Technology, 2006.computer-aided design and manufacturing(CAD/CAM)The use of computers in the design and manufacturing ofproducts revolutionized industry in the last quarter of the20th century. Although computer-aided design (CAD) andcomputer-aided manufacturing (CAM) are different areasof activity, they are now so closely integrated that they areoften discussed together as CAD/CAM.Computer-Aided DesignIn 1950, science fiction writer Robert Heinlein had hisfuture inventor create “Drafting Dan,” an automated draftingsystem that would enable designers to turn their ideasinto manufacturing plans in a fraction of the time requiredfor the hand preparation of schematics and parts lists. Bythe 1960s, engineers had developed the first computerassisteddesign programs, running on terminals attached tomainframe computers.The activity of a CAD workstation centers on the creationof geometrical models (first 2D, then 3D). With theaid of models, a virtual representation of the product beingdesigned can be built up. With its knowledge of geometricaland physical relationships, routines in the CAD system canperform not only measurement of dimensions and mass butalso structural analysis. (In some cases CAD can be interfacedwith systems that provide full-blown simulation ofthe effects of stresses, heat, and other factors.)The growth of desktop computing power in the 1980sand 1990s moved CAD from the mainframe to the high-endworkstation (such as those built by Sun Microsystems) andeven to high-end personal computers. The growing processingpower also meant that the geometric models couldbecome more sophisticated, including solid models withrealistically rendered surfaces rather than just wireframes.The model of surfaces can include such factors as reflectivity,friction, or even aerodynamic characteristics. In designinga product (or a subsystem of a product), engineers cannow use simulation software to determine how well a groupof parts in a complex assembly (such as a car’s steeringmechanism) will perform. The ability to get detailed data inreal time means that the CAD operator can work in a feedbackloop in which the design is incrementally refined untilthe required parameters are met.This growing modeling capability has been combinedwith the use of detailed databases containing the standardparts used in a particular industry or application.Libraries of templates allow the designer to “plug in” standardassemblies of parts and then modify them. The databasescan also be used with algorithms that can assist thedesigner in optimizing the design for some desired characteristic,such as strength, light weight, or lower cost.Recent systems even have the capability to set “strategic”design goals for a whole family of products and to identifyparticular optimizations that would help each part or subsystemachieve those goals.Computer-aided ManufacturingThe automated fabricating of products on the factory floororiginally developed independently of computer-aideddesign. Numerically controlled machine tools and lathes canbe programmed using specialized languages such as APT(Automatically Programmed Tool) or more recently, througha system that uses a graphical interface. Advances in patternrecognition and other artificial intelligence techniques havebeen used to improve the ability of the automatic tool toidentify particular features (such as holes into which boltsare to be inserted) and to properly orient surfaces. At somepoint the programmability and flexibility of the system withregard to its ability to manipulate the environment gives itthe characteristics of a robot (see robotics).Integration of CAD and CAMAs CAD systems became more capable, it soon became evidentthat there could be substantial benefits to be gainedfrom integrating the design and manufacturing process.The CAD software can also output detailed parts andassembly specifications that can be fed into the CAM process.In turn, manufacturing considerations can be appliedto the selection of parts during the design process.The integration of design, simulation, and manufacturingcontinues. The goal is to give the engineer aseamless way to “tweak” a design and have a number ofsimulation modules automatically depict the effects of thedesign change. In essence, the designer or engineer wouldbe working in a virtual world that accurately reflects thephysical constraints that the product will face in the realworld.The automation of the design and manufacturing processhas been mainly responsible for the increasing productivityof modern factories. Factories using traditional methods inproducing complex products such as automobiles or con-

computer-aided instruction 99sumer electronics have generally had to refit for CAD/CAMin order to remain competitive. Low-skill but relatively highpayingfactory jobs characteristic of the earlier industrial erahave given way to smaller numbers of more technical jobs.This has meant a greater emphasis on education and specializedtraining for the industrial workforce.Further ReadingAmirouche, Farid M. Principles of Computer Aided Design and Manufacturing.2nd ed. Upper Saddle River, N.J.: Prentice Hall, 2003.CADLAB (MIT). Available online. URL: http://cadlab.mit.edu/.Accessed June 12, 2007.“Computer-Aided Design” [outline and knowledge base]. Compinfo.ws.Available online. URL: http://www.compinfo-center.com/cad/cad.htm. Accessed June 12, 2007.Duggal, Vijay. CADD Primer: A General Guide to Computer AidedDesign and Drafting. New York: Mailmax Publications, 2000.computer-aided instruction (CAI)Also called computer based training (CBT), computer-aidedinstruction (CAI) is the use of computer programs to provideinstruction or training. (See education and computersfor a more comprehensive discussion of the use ofcomputers for teaching and learning.)The American reaction to Soviet space achievementsled to many attempts to modernize the educational system.While the high cost and limited capabilities of1950s computing technology allowed only for theoreticalresearch by IBM and some universities, by the 1960smore powerful solid-state computers were starting tomake what were then called “teaching machines” practicable.The first large-scale initiative was the PLATO teachingsystem designed by the Computer-based EducationalResearch Laboratory at the University of Illinois, Urbana.PLATO used a large timesharing system to provide educationalsoftware to about a thousand users at terminalsthroughout the university. PLATO pioneered the use ofgraphics and what would later be called multimedia, andwas eventually marketed by Control Data Corporation, aleading manufacturer of high-end mainframe computers.Stanford University also began a large-scale initiative todeliver computerized instruction.The early CAI systems required expensive hardware,however, and generally could be sustained only by researchfunding or where they met the growing training needs ofthe military, the aerospace industry, or other specializedusers. However, the advent of the personal computer in thelate 1970s provided both a new technology for deliveringeducational software and a potential market. With its colorgraphics and astute marketing the Apple II had became astaple of classrooms by the mid-1980s, when its successor,the Macintosh, brought more advanced graphics (seeMacintosh) and a program called Hypercard that made iteasy for educators to create simple interactive presentations(see hypertext and hypermedia). The Intel-based IBM PCand its “clones” also gained a foothold in the classroom, andMicrosoft Windows brought a graphical interface similar tothat on the Macintosh.ApplicationsThe simplest (and probably least interesting) form of CAI isoften called “drill and practice” programs. Such programs(usually found in the elementary grades) repetitively presentmath problems, reading vocabulary, or other exercisesand test the user’s understanding. (Teaching keyboard skillsto young students is another common application.) In anattempt to hold the student’s interest, many such programsprovide a gamelike atmosphere and offer periodic rewardsor reinforcement for success.More sophisticated programs allow the student morecreative scope, such as by letting the student program andtest virtual “robots” as a means of mastering a programminglanguage. Many computer games, while not designedexplicitly for instruction, provide simulations that exercisethinking and planning skills (see computer games). (Forexample, the strategy game Civilization incorporates conceptssuch as resource management, labor allocation, anda balanced economy.) Even more sophisticated programsuse advanced programming (see artificial intelligence)to interact with students in ways similar to those used byhuman teachers. For example, a program called CognitiveTutor, now used in many schools, can recognize different“styles” of learning and approaches to solving, for example,an algebra problem. The program can also identify a student’sspecific weaknesses and tailor practice and supplementalinstruction accordingly. These programs can teachand reinforce reasoning skills rather than just impartingspecific knowledge.Industry remains a large market for computer-based training.A variety of CBT packages are available for introducingand teaching programming languages such as C++ and Javaas well as for preparing students to earn industry certificatessuch as the A+ certificate for computer technicians.TrendsTwo continuing trends in CAI are the growing use ofgraphics and multimedia, including video or movies, andthe increasing delivery of training via the Internet. Sometraining software can be accessed directly over the Internetthrough a Web browser, without requiring special softwareon the user’s PC. Increasingly, even products delivered onCD and run from the user’s PC include links to supplementalmaterial on the Web.Further ReadingHorton, William. E-Learning by Design. San Francisco: Pfeiffer,2006.Ko, Suasan Schor and Steve Rossen. Teaching On-line: A PracticalGuide. 2nd ed. Boston: Houghton Mifflin, 2003.Rosenberg, Marc J. E-Learning: Strategies for Delivering Knowledgein the Digital Age. New York: McGraw-Hill, 2001.Viadero, Debra. “New Breed of Digital Tutors Yielding LearningGains.” Education Week, April 2, 2007. Available online. URL:http://www.edweek.org/ew/articles/2007/04/02/31intelligent.h26.html. Accessed June 13, 2007.Watkins, Ryan, and Michael Corry. E-Learning Companion: AStudent’s Guide to Online Success. Boston: Houghton Mifflin,2004.Web-Based Training Information Center. Available online. URL:http://wbtic.com. Accessed June 12, 2007.

100 computer crime and securitycomputer crime and securityThe growing economic value of information, products, andservices accessible through computer systems has attractedincreased attention from opportunistic criminals. In particular,the many potential vulnerabilities of online systemsand the Internet have made computer crime attractive andpose significant challenges to professionals whose task it isto secure such systems.The motivations of persons who use computer systemsin unauthorized ways vary. Some hackers primarily seekdetailed knowledge of systems, while others (often teenagers)seek “bragging rights.” Other intruders have the moretraditional criminal motive of gaining access to informationsuch as credit card numbers and personal identities thatcan be used to make unauthorized purchases (see identitytheft). Computer access can also be used to intimidate (seecyberstalking and harassment), as well as for extortion,espionage, sabotage, or terrorism (see cyberterrorism).Attacking and defending information infrastructure is nowa vital part of military and homeland security planning (seeinformation warfare).According to the federal Internet Crime Complaint Center,in 2006 the most commonly reported computer-relatedcrime was auction-related fraud (44.9 percent), followed bynondelivery of goods (19 percent)—these no doubt reflectthe high volume of auction and e-commerce transactions.Various forms of financial fraud (including identity theft)make up most of the rest.The new emphasis on the terrorist threat following September11, 2001, has included some additional attention tocyberterrorism, or the attack on computers controlling keyinfrastructure (including banks, water and power systems,air traffic control, and so on). So far ideologically inspiredattacks on computer systems have mainly amounted tosimple electronic vandalism of Web sites. Internal systemsbelonging to federal agencies and the military tend to berelatively protected and isolated from direct contact withthe Internet. However, the possibility of a crippling attackor electronic hijacking cannot be ruled out. Commercialsystems may be more vulnerable to denial-of-service attacks(see below) that cause economic losses by preventing consumersfrom accessing services.Forms of AttackSurveillance-based attacks involve scanning Internet trafficfor purposes of espionage or obtaining valuable information.Not only businesses but also the growing number ofInternet users with “always-on” Internet connections (seebroadband) are vulnerable to “packet-sniffing” softwarethat exploits vulnerabilities in the networking software oroperating system. The main line of defense against suchattacks is the software or hardware firewall, which both“hides” the addresses of the main computer or network andidentifies and blocks packets associated with the commonforms of attack (see firewall).In the realm of harassment or sabotage, a “denial of service”(DOS) attack can flood the target system with packetsthat request acknowledgment (an essential feature of networkoperation). This can tie up the system so that a Webserver, for example, can no longer respond to user requests,making the page inaccessible. More sophisticated DOSattacks can be launched by first using viruses to insert programsin a number of computers (a so-called botnet), andthen instructing the programs to simultaneously launchattacks from a variety of locations.Computer viruses can also be used to randomly vandalizecomputers, impeding operation or destroying data (seecomputer virus). But a virus can also be surreptitiouslyinserted as a “Trojan horse” into a computer’s operating systemwhere it can intercept passwords and other information,sending them to the person who planted the virus. Viruseswere originally spread through infected floppy disks (often“bootleg” copies of software). Today, however, the Internetis the main route of access, with viruses embedded in e-mailattachments. This is possible because many e-mail and otherprograms have the ability to execute programs (scripts) thatthey receive. The main defense against viruses is regularuse of antivirus software, turning off scripting capabilitiesunless absolutely necessary, and making a policy of notopening unknown or suspicious-looking e-mail attachmentsas well as messages that pretend to be from reputable banksor other agencies (see phishing and spoofing).Computer SecurityBecause there are a variety of vulnerabilities of computersystems and of corresponding types of attacks, computersecurity is a multifaceted discipline. The vulnerability ofcomputer systems is not solely technical in nature. Sometimesthe weakest link in a system is the human link.Hackers are often adept at a technique they call “socialengineering.” This involves tricking computer operatorsinto giving out sensitive information (such as passwords)by masquerading as a colleague or someone else who mighthave a legitimate need for the information.Since computer crimes and attacks can take so manyforms, the best defense is layered or in depth. It includesappropriate software (firewalls and antivirus programs,and network monitoring programs for larger installations).It emphasizes proper training of personnel, ranging fromsecurity investigators to clerical users. Finally, if informationis compromised, the use of strong encryption can makeit much less likely to be usable (see encryption).While the flexibility and speed of the Internet can aidattackers, it can also facilitate defense. Emergency responsenetworks and major vendors of antivirus software canquickly disseminate protective code or “patches” that closevulnerabilities in operating systems or applications.The growing concern about vulnerability to computerintrusion and information theft has also been reflected inattempts to make operating systems inherently more secure.The introduction of new security features in Microsoft WindowsVista has received mixed reviews. Some features, suchas User Account Control, make it harder for viruses orother automated attacks to access critical system resources,but also annoy users by constant requests for permission tocarry out common tasks. This reflects a fundamental truth:Security features that make everyday computing moretedious tend to be turned off or bypassed by users.

computer engineering 101Once a computer-based crime is detected, a systematicapproach to evidence gathering and investigation isrequired (see computer forensics). This is because evidencein computer crimes tends to be technical, intangible,and transient, and thus difficult to explain properly tojudges and juries.Individual consumers can reduce their vulnerability byensuring that they do not give out personal informationwithout verifying both the requester and the need for thedata. Use of secure Web sites for credit card transactionshas become standard. Generally speaking, vulnerabilityto computer crime is inversely proportional to the degreeof privacy individuals have with regard to their personalinformation (see privacy in the digital age). Public concernabout privacy and security has led to recent laws andinitiatives aimed at disclosure of organizations’ privacypolicy and limiting the redistribution of information oncecollected.Further ReadingBalkin, J. M. Cybercrime: Digital Cops in a Networked Environment.New York: New York University Press, 2007.CERT Coordination Center, Carnegie-Mellon University. Availableonline. URL: http://www.cert.org. Accessed August 12, 2007.Easttom, Chuck. Computer Security Fundamentals. Upper SaddleRiver, N.J.: Prentice Hall, 2005.McQuade, Sam C. Understanding and Managing Cybercrime. Boston:Allyn & Bacon, 2005.Mitnick, Kevin, and William L. Simon. The Art of Intrusion. NewYork: Wiley, 2005.computer engineeringComputer engineering involves the design and implementationof all aspects of computer systems. It is the practicalcomplement to computer science, which focuses onthe study of the theory of the organization and processingof information (see computer science). Because hardwarerequires software (particularly operating systems) in orderto be useful, computer engineering overlaps into softwaredesign, although the latter is usually considered to be aseparate field (see software engineering).To get an idea of the scope of computer engineering, considerthe range of components commonly found in today’sdesktop computers:ProcessorThe design of the microprocessor includes the number andwidth of registers, method of instruction processing (pipelining),the chipset (functions to be integral to the packagewith the microprocessor), the amount of cache, the connectionto memory bus, the use of multiple processors, theorder in which data will be moved and stored in memory(low or high-order byte first?), and the clock speed. (Seemicroprocessor, chipset, cache, bus, multiprocessing,memory, and clock speed.)MemoryThe design of memory includes the type (static or dynamic)and configuration of RAM, the maximum addressable memory,and the use of parity for error detection (see memory,addressing, and error correction). Besides randomaccessmemory, other types of memory include ROM (readonlymemory) and CMOS (rewritable persistent memory).MotherboardThe motherboard is the platform and data transfer infrastructurefor the computer system. It includes the main databus and secondary buses (such as for high-speed connectionbetween the processor and video subsystem—see bus).The designer must also decide which components will beintegral to the motherboard, and which provided as addonsthrough ports of various kinds.Peripheral DevicesPeripheral devices include fixed and removable disk drives;CD and DVD-ROM drives, tape drives, scanners, printers,and modems.Device ControlEach peripheral device must have an interface circuit thatreceives commands from the CPU and returns data (seegraphics card).Input/Output and PortsA variety of standards exist for connecting external devicesto the motherboard (see parallel port, serial port, andusb). Designers of devices in turn must decide which connectionsto support.There are also a variety of input devices to be handled,including the keyboard, mouse, joystick, track pad, graphicstablet, and so on.Of course this discussion isn’t limited to the desktop PC;similar or analogous components are also used in larger computers(see mainframe, minicomputer, and workstation).NetworkingNetworking adds another layer of complexity in controllingthe transfer of data between different computer systems,using various typologies and transport mechanisms (suchas Ethernet); interfaces to connect computers to the network;routers, hubs, and switches (see network).Other ConsiderationsIn designing all the subsystems of the modern computer andnetwork, computer engineers must consider a variety of factorsand tradeoffs. Hardware devices must be designed witha form factor (size and shape) that will fit efficiently into acrowded computer case. For devices that require their ownsource of power, the capacity of the available power supplyand the likely presence of other power-consuming devicesmust be taken into account. Processors and other circuitsgenerate heat, which must be dissipated. (In an increasinglyenergy-conscious world the reduction of energy consumption,such as through standby or “hibernation” modes, isalso an important consideration—see green pc.) Heat andother forms of stress affect reliability. And in terms of how

102 computer forensicsa device processes input data or commands, the applicablestandards must be met. Finally, cost is always an issue.Moving beyond hardware to operating system (OS)design, computer engineers must deal with many additionalquestions, including the file system, how the OS will communicatewith devices (or device drivers), and how applicationswill obtain data from the OS (such as the contents ofinput buffers). Today’s operating systems include hundredsof system functions. Since the 1980s, the provision of allthe objects needed for a standard user interface (such aswindows, menus, and dialog boxes) has been consideredto be part of the OS design. Finally, the building of securityfeatures into both hardware and operating systems hasbecome an integral part of computer engineering (see, forexample, biometrics and encryption).TrendsIn the early days of mainframe computing (and again atthe beginning of microcomputing) many distinctive systemarchitectures entered the market in rapid succession. Forexample, the Apple II (1977), IBM PC (1981), and AppleMacintosh (1984) (see ibm pc and Macintosh). Becausearchitectures are now so complex (and so much has beeninvested in legacy hardware and software), wholly newarchitectures seldom emerge today. Because of the complexityand cost involved in creating system architectures,development tends to be incremental, such as adding PCIcard slots to the IBM PC architecture while retaining olderISA slots, or replacing IDE controllers with EIDE.The growing emphasis on networks in general and theInternet in particular has probably diverted some effort andresources from the design of stand-alone PCs to networkand telecommunications engineering. At the same time,new categories of personal computing devices have emergedover the years, including the suitcase-size “transportable”PC, the laptop, the book-sized notebook PC, the handheldPDA (personal digital assistant), as well as network-orientedPCs and “appliances.” (See portable computers andsmartphone.)As computing capabilities are built into more traditionaldevices (ranging from cars to home entertainment centers),computer engineering has increasingly overlapped otherfields of engineering and design. This often means thinkingof devices in nontraditional ways: a car that is able to plantravel, for example, or a microwave that can keep track ofnutritional information as it prepares food (see embeddedsystem). The computer engineer must consider not only therequired functionality but the way the user will access thefunctions (see user interface).Further ReadingIEEE Computer Society. Available online. URL: http://www.computer.orgPatterson, D. A. and J. L. Hennessy. Computer Organization andDesign. 3rd ed. San Francisco: Morgan Kaufmann, 2004.“PC Guide.” Available online. URL: www.pcguide.com. AccessedJune 18, 2007.Stokes, John. Inside the Machine: An Illustrated Introduction toMicroprocessors and Computer Architecture. San Francisco: NoStarch Press, 2007.computer forensicsComputer forensics is the process of uncovering, documenting,analyzing, and preserving criminal evidence thathas been stored on (or created using) a computer system.(For the use of computers by police, see law enforcementand computers.)In general, computer forensics involves both adherenceto legal evidentiary standards and the use of sophisticatedtechnical tools. The legal standards requirepractices similar to those used in obtaining other typesof criminal evidence (observing expectations of privacy,knowing when a warrant is needed to search and seizeevidence, and so on).Once there is a go-ahead for a search, the first step is todocument the layout and nature of the equipment (generallyby photographing it) and to identify both devices thatmight be problematic or notes or other materials that mightreveal passwords for encrypted data.If the system is running it may be viewed or scanned todetermine what applications are running and what networkconnections may be active. However, this has to be done asunobtrusively as possible, since some machines can detectphysical intrusions.Step by step, the forensic technician must documenteach software program or other tool used, and why it isjustified (such as the possibility that simply shutting downthe system might lead to loss of data in RAM). There are avariety of such tools, particularly for UNIX/Linux environments,some of which have been ported to Windows. (Insome cases a Linux “live” CD might be booted and used toexplore a Windows file system.)The next step is to collect the evidence from storagemedia in such a way as to ensure that it is accurately andcompletely preserved. A running machine must generallyfirst be shut down in such a way as to prevent triggeringany “trip wire” or intrusion-detection or self-destructmechanism that may have been installed.As a practical matter, once the system has been properlyshut down or immobilized, it is usually taken to the forensiclaboratory for extraction, copying, and documenting ofthe evidence (such as files on a hard drive or other storagedevice).Once the data has been collected, each file or documentmust be analyzed to determine if it is relevant to the criminalinvestigation and what key information it contains. Forexample, e-mail headers may be analyzed to determine thesource and routing of the message.Some Typical CasesComputer-based evidence may be relevant for almost anytype of crime, but certain kinds of crimes are more likely toinvolve computer forensics. These include:• financial crimes, such as embezzlement• corporate crimes such as insider trading, where e-mails may reveal who knew what and when• data or identity theft, including online scams orphishing

computer games 103• stalking or harassment, particularly involving chatrooms or social networks• child pornography, particularly distribution of imagesIn recent years many law enforcement agencies havebecome aware of the importance of proper investigation andtreatment of evidence in our digital society, and demandfor trained computer forensic specialists is expected toincrease.Further ReadingBritz, Marjie T. Computer Forensics and Cyber Crime: An Introduction.Upper Saddle River, N.J.: Prentice Hall, 2003.Carrier, Brian. File System Forensic Analysis. Upper Saddle River,N.J.: Addison-Wesley Professional, 2005.“Searching and Seizing Computers and Obtaining ElectronicEvidence in Criminal Investigations.” U.S. Dept. of Justice,July 2002. Available online. URL: http://www.usdoj.gov/criminal/cybercrime/s&smanual2002.htm. Accessed September3, 2007.Steel, Chad. Windows Forensics: The Field Guide for ConductingCorporate Computer Investigations. Indianapolis: Wiley, 2006.Vacca, John R. Computer Forensics: Computer Crime Scene Investigation.2nd ed. Hingham, Mass.: Charles River Media, 2005.computer gamesToday, playing games is one of the most popular computingactivities. In the early days of computing, games offered away to test AI techniques (see artificial intelligence).Games have also encouraged the development of moresophisticated graphics (see computer graphics) and waysof interacting with the machine (see user interface).Games and AIAlthough modern computer games may draw upon severalgenres, several recognizably distinct types of games havebeen developed over the past half century or so. The firstwere computer versions of existing board games. “Deterministic”games (where there is no element of chance) suchas tick-tack-toe and, more important, checkers and chessoffered a challenge to the first computer scientists who wereseeking to learn how to make machines perform tasks thatare usually attributed to human intelligence. For example,Alan Turing and Claude Shannon both developed chessplayingprograms, although Turing’s came at a time whencomputers were still too primitive to handle the volume ofcalculations required, and was thus carried out by hand. Bythe time a computer program (Deep Blue) had defeated theworld champion in 1997, the AI field had long since left thegame behind (see chess and computers).Simulation GamesMilitary planners had devised war games since the 19thcentury, but the complexity of modern warfare (includinglogistics as well as tactics) cried out for the help of the computer.By 1955 the U.S. military was running large-scaleglobal cold war simulations pitting NATO against the USSRand the Eastern bloc. Unlike deterministic games such aschess, war games generally use complex rules to captureA scene from the computer strategy game Civilization. Some gamesspecialize in realistic physical simulation, while others (such as thisone) embody sophisticated economic and strategic considerations.the many interacting factors such as the morale, experience,and firepower of a military unit or the performanceof an air defense system against different types of targets.The results will be more or less realistic depending on howmany factors are properly accounted for—often only latercombat experience will tell.The use of game theory (the mathematics of competitivesituations) and economics also proved to be fruitful areasfor the use of computer simulations. In 1959 Carnegie Tech(later Carnegie-Melon University) introduced a simulationcalled “The Management Game.” Until the 1980s, however,lack of inexpensive computing power kept sophisticatedsimulations limited to large institutions such as the military,government, universities, and major corporations.Today simulation games are popular in both the educationaland consumer markets. They include flight simulators,a variety of sports including baseball, football, soccer,and golf, and games in which the player strives to build a19th-century railroad empire or run a modern city. Indeedsome games, such as the popular kingdom-building simulatorCivilization or the complex Sim City, while marketed primarilyas entertainment, can easily fit into a social studiescurriculum.Arcade and Graphic GamesStarting in the 1960s, CRT (television-like) displays gavethe new minicomputers the means to display simple graphics.In 1962, an intrepid band of game hackers at MIT createdSpacewar, the first interactive graphic game and theforerunner of the arcade boom of the 1970s. When thefirst home computers from Apple, Commodore, Atari, andIBM hit the market in the late 1970s and early 1980s, theyincluded rudimentary (but often colorful) graphics capabilities.Many amateur programmers used the computers’built-in BASIC language to create games such as lunarlander simulators and Star Trek–style space battles. Around

104 computer graphicsthe same time, the home game cartridge machine was introducedby Atari and other companies, while the arcade gamePac-Man became a phenomenal success in 1980 (see gameconsoles).Role-playing, Real-time, and Social WorldsAround the time of the first home computers, a noncomputergame called Dungeons and Dragons became extremelypopular. “D&D” and other role-playing games allowed playersto create and portray characters, with elaborate rulesbeing used to resolve events such as battles. Role-playinggames soon began to appear on PCs—early examplesinclude the Wizardry and Ultima series. Meanwhile, textbasedadventure games were becoming popular on earlycomputer networks, particularly at universities. Theseevolved into MUDs (Multi-User Dungeons) where players’characters could interact with each other. Eventually manyof these programs went beyond their adventuring roots tocreate a variety of social worlds in a sort of text-based virtualreality.By the 1990s, the typical PC had a special circuit (seegraphics card) capable of displaying millions of colors,together with video memory (now 256 MB or more) thatcould hold the complex images needed for high-resolutionanimation. Computer game graphics have become increasinglycomplex (see computer graphics), including realistictextures, shading and light, smooth animation, andspecial effects rivaling Hollywood. (Compare, for example,early wireframe graphics in games such as the Wizardry of1980 with games such as Diablo II and Warcraft with animatedcharacters moving in a richly textured world.)The way players interact with the game world has alsosignificantly changed. The first computer games tended tobe divided into turn-based strategy and role-playing gamesand real-time arcade-style “shoot ’em ups.” Today, however,most games, regardless of genre, run as RTS (real-time simulations)in which players must interact continuously withthe game situation.By the late 1990s gaming was no longer a solitary pursuit.The Internet made it possible to offer game worlds inwhich thousands of players could participate simultaneously(see online games). Games such as Everquest andAsheron’s Call have thousands of devoted players who spendmany hours developing their characters’ skills, while openendedworlds such as Second Life seem to no longer begames at all, but a virtual, parallel universe with a fullrange of social interaction. However, the increased realismof modern games has also heightened the controversyabout in-game violence and other antisocial behavior, asin the Grand Theft Auto series. (Although there is a ratingsystem for games similar to that for movies, its effectivenessin keeping adult-themed games out of the hands of youngchildren seems to be limited.)Game DevelopmentThe emphasis on state-of-the-art animation and graphicsand multiplayer design has changed the way game developmentis done. The earliest home computer games were typicallythe product of a single designer’s vision, such as ChrisCrawford’s Balance of Power and Richard Garriott (“LordBritish”) in the Ultima series. Today, however, commerciallycompetitive games are the product of teams that includegraphics, animation, and sound specialists, actors and voicetalent, and other specialists in addition to the game designers.While earlier games might be compared to books withsingle authors, modern game developers often comparetheir industry to the movie industry with its dominant studios.And, as with the movie industry, critics have arguedthat the high cost of development and of access to the markethas led to much imitation of successful titles and lessinnovation.On the other hand, a variety of modern programmingenvironments (such as Visual Basic or even MacromediaFlash) make it easy for young programmers to get a tasteof game programming, and for amateur programmers tocreate games that can be distributed via the Internet (seeshareware and freeware). Although computer scienceprograms have been slow to recognize the attraction andvalue of game programming, a variety of academic programsare now emerging. These range from computer arts,graphics, and animation programs to a full-fledged fouryeardegree program in game design at the University ofCalifornia, Santa Cruz. This program includes not onlycourses in game design and programming, but also courseson the game business and even ethics.Further ReadingAronson, Sean. “School Fills Need for Game Designers.” Medianews,June 18, 2007. Available online. URL: http://www.insidebayarea.com/sanmateocountytimes/localnews/ci_6168502. Accessed June 20, 2007.Chaplain, Heather, and Aaron Ruby. Smartbomb: The Quest forArt, Entertainment, and Big Bucks in the Videogame Revolution.Chapel Hill, N.C.: Algonquin Books, 2005.Crawford, Chris. Chris Crawford on Game Design. Indianapolis:New Riders, 2003.———. Chris Crawford on Interactive Storytelling. Berkeley, Calif.:New Riders, 2005.Game Developer. [magazine] Available online. URL: http://www.gdmag.com/homepage.htm. Accessed June 23, 2007.Howland, Geoff. “How Do I Make Games? A Path to Game Development.”Available online. URL: http://www.gamedev.net/reference/design/features/makegames/. Accessed June 23, 2007.Moore, Michael E., and Jennifer Sward. Introduction to the GameIndustry. Upper Saddle River, N.J.: Prentice Hall, 2006.computer graphicsMost early mainframe business computers produced outputonly in the form of punched cards, paper tape, or textprintouts. However, system designers realized that somekinds of data were particularly amenable to a graphical representation.In the early 1950s, the first systems using thecathode ray tube (CRT) for graphics output found specializedapplication. For example, the MIT Whirlwind and theAir Force’s SAGE air defense system used a CRT to displayinformation such as the location and heading of radar targets.By 1960, the new relatively inexpensive minicomputerssuch as the DEC PDP series were being connected toCRTs by experimenters, who among other things createdSpacewar, the first interactive video game.

computer graphics 105By the late 1970s, the microcomputers from Apple, RadioShack, Commodore, and others either included CRT monitorsor had adapters that allowed them to be hooked upto regular television sets. These machines generally camewith a version of the BASIC language that included commandsfor plotting lines and points and filling enclosedfigures with color. While crude by modern standards, thesegraphics capabilities meant that spreadsheet programscould provide charts while games and simulations couldshow moving, interacting objects. Desktop computers thatshowed pictures on television-like screens seemed less forbiddingthan giant machines spitting out reams of printedpaper (see graphics card).Research at the Xerox PARC laboratory in the 1970sdemonstrated the advantages of a graphical user interfacebased on visual objects, including menus, windows, dialogboxes, and icons (see user interface). The Apple Macintosh,introduced in 1984, was the first commercially viablecomputer in which everything displayed on the screen(including text) consisted of bitmapped graphics. Microsoft’ssimilar Windows operating environment becamedominant on IBM architecture PCs during the 1990s.Today Apple, Microsoft, and UNIX-based operating systemsinclude extensive graphics functions. Game and multimediadevelopers can call upon such facilities as AppleQuickDraw and Microsoft DirectX to create high resolution,realistic graphics (see also game console).Basic Graphics PrinciplesThe most basic capabilities needed for computer graphics arethe ability to control the display of pixels (picture elements)on the screen and a way to specify the location of the spotsto be displayed. A CRT screen is essentially a grid of pixelsthat correspond to phosphors (or groups of colored phosphors)that can be lit up by the electron beam(s). The firstIBM PCs, for example, often displayed graphics on a 320(horizontal) by 200 (vertical) grid, with 4 available colors.A memory buffer is set up whose bytes correspond to thevideo display. (A simple monochrome display needs onlyone bit per pixel, but color displays must use additionalspace to store the color for each pixel.) A screen image isset up by writing the data bytes to the buffer, which thenis sent to the video system. The video system uses the datato control the display device so the corresponding pixelsare shown (in the case of a CRT, this means lighting up the“on” pixels with the electron gun[s]).In most cases screen locations are defined in coordinateswhere point 0,0 is the upper left corner of the screen.The coordinates of the lower right corner depend on thescreen resolution, At 320 by 200, the lower right cornerwould be 319,199.For example, many versions of BASIC use statementssuch as the following:PSET 50,50 ’ draws a dot at X=50, Y=50LINE (100,50)-(150,100), B ’ draw squarewith UL’ corner at 100,50 and LR’ corner at 150,100Some example figures plotted by BASIC graphics statements usingscreen coordinates.CIRCLE (100,150), 50, 4 ’ draw a circle ofradius 50’ with center at 200,200 and’ color 4 (red)Languages such as C, C++ and Java don’t have built-ingraphics commands, but functions can be provided in programlibraries (see library, program). They would be usedmuch like the BASIC commands given above.More commonly, however, programmers use languageindependentgraphics platforms (see api). With Windows,this usually means DirectX, which includes Direct2D for3D graphics, as well as a variety of multimedia librariesfor sound, user interfacing, and networking. A competitorthat is particularly popular in the Mac and UNIX/Linuxworlds is OpenGL (Open Graphics Library). Both DirectXand OpenGL run on a wide variety of supported hardware.Graphics Models and EnginesModern applications (such as drawing programs and games)go well beyond simple two-dimensional objects. Indeed,multimedia developers typically use graphics enginesdesigned to work with C++ or Java. A graphics engineprovides a way to define and model 2D and 3D polygons.(Curves can be constructed by specifying “control points”for bicubic curves.)Complex objects can be built up by specifying hierarchies(for example, a human figure might consist of a head,neck, upper torso, arms, hands, lower torso, legs, feet, and

106 computer industryso on). By creating a hierarchy of arm, hand, fingers a transformation(scaling or rotation) of one object can be propagatedto its dependent objects (see animation). In manycases graphics are created from real-world objects that havebeen digitally photographed or scanned, and then manipulated(see image processing).In most scenes the relationships between graphicalobjects are also important. Modern graphics modeling programsuse a virtual “camera” to indicate the position andangle from which the graphics are to be viewed. In renderingthe scene, the Painter’s Algorithm can be used to sortobjects and draw closer surfaces on top of farther ones, asa painter might paint over the background. Alternatively,the Z-buffer algorithm stores depth information for eachpixel to determine which ones are drawn. This techniquerequires less calculation (because surfaces don’t need tobe sorted), but more memory, since the depth of each pixelmust be stored.Within a scene, the effects of light (and its absence,shadows) must be realistically rendered. A simple techniquecan be used to calculate an overall light level for anobject based on its angle in relation to the light source,plus a factor to account for ambient and diffuse light in theenvironment. The Gouraud shading technique can be usedto smooth out the artifacts caused by the simple flat shadingmethod. Another technique, Phong shading, can morerealistically reproduce highlights (the sharp image of a lightsource being reflected within a surface). But the most realisticlighting effects are provided through ray tracing, whichinvolves tracing how representative vectors (representingrays of light) reflect from or refract through various surfaces.However, ray tracing is also the most computationallyintensive lighting technique.Several techniques can be used to give objects morerealistic surfaces. Texture mapping can be used to “paint”a realistic texture (perhaps scanned from a real-worldobject) onto a surface. For example, pieces in a chess gamecould be given a realistic wood grain or marble texture.This can be further refined through bump mapping, whichcalculates variations in the texture at each point based onlight reflections.Applications and TradeoffsThe most graphics-intensive applications today are games,multimedia programs, and scientific visualization or modelingapplications. Because of the impact graphics have onusers’ perception of games and multimedia programs, developersspend a high proportion of their resources on graphics.Critics often complain that this is at the expense ofcore program functions. The software in turn places a highdemand on user hardware: The contemporary “multimedia-ready”PC has a video card that includes special “videoaccelerator” hardware to speed up the display of graphicsdata and a video memory buffer of 256 MB or more.Complex 3D graphics with lighting, shading, and texturesmay have to be displayed at a relatively low resolution(such as 640 × 480) because of the limitations of the mainprocessor (which performs necessary calculations) and thevideo card. However as processor speed and memory capacitycontinue to increase, many computer graphics now rivalvideo and even film in realistic detail.Further ReadingACMSIGGRAPH. [graphics special interest group] Availableonline. URL: http://www.siggraph.org/. Accessed June 24,2007.Computer Graphics World. [magazine] Available online. URL:http://www.cgw.com/ME2/Default.asp. Accessed June 24,2007.Govil-Pai, Shalini. Principles of Computer Graphics: Theory andPractice Using OpenGL and Maya. New York: Springer, 2005.Jones, Wendy. Beginning DirectX 10 Game Programming. Boston:Thomson Course Technology PTR, 2007.computer industryThe U.S. computer industry began with the marketing of theUnivac, designed by J. Presper Eckert and John Mauchly inthe early 1950s. The first computers were made one at a timeand only as ordered, and the market for the huge, expensivemachines was thought to be limited to government agenciesand the largest corporations. However, astute marketing bySperry-Univac, Burroughs, and particularly, InternationalBusiness Machines (see ibm) convinced a growing numberof companies that modern data processing facilities wouldbe essential for managing their growing and increasinglycomplex business (see mainframe).The mainframe market was controlled by a handful ofvendors who typically provided the complete computer system(including peripherals such as printers) and a long-termservice contract. (Eventually, third-party vendors began tomake compatible peripherals.) Companies that could notafford their own computers began to contract with servicebureaus for their data processing needs, such as payrollprocessing.By the 1960s, transistorized circuitry was replacingthe vacuum tube, and somewhat smaller machines becamepracticable (see minicomputer). While these computerswere the size of a desk, not a desktop, models such as DigitalEquipment Corporation’s PDP series and competitionfrom companies such as Data General provided computingpower for engineers and scientists to use in factories andlaboratories. During the 1970s, the dedicated word processingmachine marketed by the Wang Corporation beganthe digital transformation of the office. By the end of thatdecade, the first general-purpose desktop microcomputerswere marketed. The Apple II made a modest inroad intobusiness, fueled by VisiCalc, the first spreadsheet program.This new market attracted the attention of IBM, viewedby many microcomputer enthusiasts as a dinosaurlike relicof the mainframe age. Uncharacteristically, IBM managementgave the developers of their personal computer (PC)project free rein, and the result was the IBM PC introducedin 1981. The machine had two major advantages. One wasthe IBM name itself, which was comforting to executivescontemplating a bewildering new technology. The otherwas that IBM (again, uncharacteristically) had followedApple’s lead in designing their PC with an “open architecture,”meaning that third-party manufacturers could mar-

computer industry 107ket a variety of expansion cards to increase the machine’scapabilities. By 1990, about 10 million PCs worth about $80billion were being sold annually (see ibm pc).Although IBM tried to prevent other manufacturers from“cloning” the IBM chipset itself, it was unable to preventcompanies such as Compaq from creating “IBM compatible”PCs that often surpassed the capabilities of the IBM models.(IBM introduced its microchannel architecture in thelate 1980s in an unsuccessful attempt to regain proprietaryadvantage.) By the 1990s the IBM-compatible PCs (sometimescalled “Wintel,” for the Microsoft Windows operatingsystem and Intel-compatible processor) had becomean industry standard and a commodity manufactured andmarketed by everything from the big name brands suchas Dell and Gateway down to the corner computer store’sbackroom operation.The announcement of Apple’s Macintosh computer in1984 made a vivid impression on the public (see Macintosh).With its fully graphical user interface, mouse, drawingprogram, and fonts, it seemed light-years ahead of thetext-based IBM PCs. However, the Mac’s slow speed, relativelyhigh price, and closed architecture limited its penetrationinto the business market. The Mac did attract anenthusiastic minority of consumer users and achieved alasting niche presence in education and among graphicsand video professionals. Gradually, as Microsoft’s graphicalWindows operating system improved in the early 1990s,the Mac’s advantages over the IBM-compatible machinesdiminished.During the 1990s, desktop computers came with aseries of increasingly powerful series of Pentium processors,matched by offerings from AMD and Cyrix. Multimedia(including high-end graphics and sound capabilities)became a standard feature, particularly on consumer PCs.Increasingly, the business PC was being connected to alocal area network, and both business and consumer PCsincluded modems or broadband access to online servicesand the Internet. The need to manage network files and services(such as Web servers) led to the development of serverPCs featuring high-capacity mass storage. At the same time,high-end PCs also challenged the graphics workstationsmade by companies such as Sun. The traditional minicomputerand high performance workstation category beganto melt away. By 2002, an estimated 600 million personalcomputers were in use worldwide, with about half of themin homes.The personal computer also grew smaller. The suitcasesized“luggable” computers of the 1980s gave way to a rangeof laptop, notebook-sized, and palm-sized computers. Todaywireless networking technology allows users of diminutivemachines to access the full resources of the World WideWeb and local networks.The idea of “appliance computing” has also been arecurrent theme among industry pundits. Proponents arguethat there are still many people who feel intimidated by astandard computer interface but have become comfortablewith other consumer electronic products such as televisions,CD players, or microwaves. If computer functionscould be built into such devices, people might use themcomfortably. For example, WebTV is a box that allows theuser to surf the Web from the same armchair where he orshe watches TV, using controls little more complicated thanthose found on a regular TV remote. Kitchen appliancesmight be transformed, with the microwave providing recipesand the refrigerator keeping an inventory and automaticallyordering from the grocery store. However, as with thefully automated “wired home,” featured in Sunday newspapersupplements, the appliance computer has remaineddifficult to market to consumers (see smart buildings andhomes).The Software IndustryHardware is useless without software. Since the operatingsystem (OS) is the software that enables all other softwareto access the computer, the OS market is a key part of thecomputer industry. Through a historical accident, a youngprogrammer-entrepreneur named Bill (William) Gatesand his Microsoft Corporation received the contract todevelop the operating system for the first IBM PC. Microsoftbought and adapted an existing operating system tocreate MS-DOS (also called PC-DOS). Until the end of the1980s, DOS was the dominant operating system for IBMcompatiblePCs (see ms-dos). In the early 1990s, Microsoftintroduced Windows 3.0, the first successful version of itsgraphical operating environment (see Microsoft Windows).The dominance of Windows became so completethat a federal antitrust case against Microsoft resulted inthe company having to provide competitors greater accessto the operating system.The source of emerging challenges to Windows comesnot from another desktop vendor but from the Internet,where Java offers the potential of delivering applicationsthrough the user’s Web browser, regardless of whether thatuser is running Windows, the Macintosh OS, or Linux, avariant of UNIX that has been embraced by many enthusiasts.However, Java applications and Linux still representonly a tiny fraction of the market share held by Windows(see Java and Linux).The 1990s saw considerable consolidation in the officesoftware arena. Microsoft’s Office software suite overwhelmedonce formidable competitors such as WordPerfectand Corel. Packages such as Microsoft Office create theirown mini-industries where developers create templates andadd-ins. However, the widespread use of high-speed Internetaccess (see broadband) has made it practicable to offermany office software functions online, providing workerswith convenient access from any location. The most significantoffering here has been Google Apps, which includescalendar and communications features as well as GoogleDocs & Spreadsheets. In turn, Microsoft has been promptedto offer added-value online features to Microsoft Office.Outside the office there is considerably more competitionin the software industry. Today’s consumers can choosefrom a wide variety of software that fills utility or other nicheneeds, including shareware (“try before you buy”) offerings.In educational software and games some once-major innovatorshave been bought out or consolidated, but there is noone dominant company. Thousands of specialized software

108 computer industrypackages serve scientific, manufacturing, and businessneeds. While the general public is unaware of such programs,they make up much of the strength of the softwareindustry.Other Products and ServicesBy the 2000s there were many new niches in the computerindustry landscape. Powerful dedicated game machinessuch as the Microsoft Xbox 360 and the Sony PlayStation3 make for a vigorous software industry that potentiallygoes beyond games (see game consoles). Portable mediaplayers such as Apple’s iPod are ubiquitous (see music andvideo players, digital). The personal digital assistant (seepda) and the cell phone have largely merged and morphed(see smartphone), capable of running a variety of softwareincluding e-mail, Web browsing, games, and music.Meanwhile, digital cameras have virtually replaced film forall but the most high-end and specialized applications (seephotography, digital). The convergence and proliferationof all of these devices is continuing at a rapid pace, andcompetition is fierce.The services sector of the computer industry lacks thevisibility of new hardware products, but provides mostof the industry’s employment and much of its economicimpact. In addition to the hundreds of thousands of programmerswho provide business-related, consumer, andspecialized software, there are the legions of help deskemployees, computer and network technicians, creators ofsoftware development tools, writers of technical books andtraining products, industry investment analysts, reporters,and many others whose livelihood depends on the computerindustry.International ComputingThe computing industry came of age mainly in the UnitedStates. By the 1960s IBM had extended its dominant positionto Britain and Europe despite the efforts of indigenouscompanies and government initiatives. Japan was considerablymore successful in developing a competitive electronicsand computer industry under the long-term guidance ofMITI (Ministry of International Trade and Industry). TheJapanese became dominant in industrial robotics and strongin consumer electronics, including game machines (Sony),digital cameras (Sony and Fujitsu), and laptop computers(Toshiba). They have been less successful in desktop computers,Internet-related technology, and commercial software.China has become an increasingly important playerin the components and peripherals industry. The growingimportance of Asia in the international computer industryis also underscored by the large number of programmers,engineers, and support personnel being trained in India(see globalism and the computer industry).Major Internet industry players such as Google andYahoo! as well as hardware giant Dell have become heavilyinvolved in the Chinese market, which boasted about 100million users in 2006, second only to the United States.A number of initiatives are helping spread computingeven in the limited economies of many countries in Africa,Asia, and Latin America (see developing nations andcomputing). While illicit copying has hindered the marketingof commercial software in many countries, the alternativemodel of open-source software and very inexpensivelaptops (the One Laptop Per Child initiative) may offer aviable path to the true globalization of computing.Emerging TrendsAs the 2000 decade has progressed, a number of trendscontinue to reshape the computer industry. These include:• The recovery from the “bust” years of 2001–3 was followedby more modest but significant growth, withrapid growth in particular sectors such as mobiledevices, Web applications (see Web 2.0), and security.• Desktop PC sales were strong through 2005 (about200 million that year) but now appear to be stagnating(in the United States at least) in favor of laptops,smaller portable computers, and smart phones.• Although a new generation of multicore processorsand the resource-hungry Microsoft WindowsVista operating system may eventually speed up thereplacement of older PCs, businesses have been tendingto keep slightly obsolescent machines and operatingsystems longer.• Free or lower-cost alternative software and operatingsystems (see open source and Linux) are attractingconsiderable publicity, but it is unclear how muchpenetration they will achieve in the mainstream homeand small-business computing sectors.• Besides cost consciousness and other priorities (suchas networking and security), the trend toward Webbasedapplications may be shifting sales away fromhardware and traditional operating systems and softwaresuites. (See application service provider.)• Outsourcing of many IT functions is continuing,including network administration, managed backupand storage, and even security. Meanwhile, there hasbeen concern about lack of sufficient U.S. graduatesin computer science and engineering.While the computer hardware, software, and serviceindustries are likely to continue growing vigorously, theboundaries between sectors and applications are blurring,making it harder to consider the industry as a wholeas opposed to specific sectors and applications (seee-commerce).Further ReadingChandler, Alfred D., Jr. Inventing the Electronic Century: The EpicStory of the Consumer Electronics and Computer Industries.New ed. Cambridge, Mass.: Harvard University Press, 2005.Computer Industry Almanac. Available online. URL: http://www.c-i-a.com/. Accessed June 24, 2007.Computerworld. Available online. URL: http://www.computerworld.com/. Accessed June 24, 2007.Infoworld. Available online. URL: http://www.infoworld.com/.Accessed June 24, 2007.International Data Corporation. Available online. URL: http://www.idc.com/. Accessed June 24, 2007.

computer science 109PC World. Available online. URL: http://www.pcworld.com.Accessed June 24, 2007.Plunkett’s Info Tech, Computers & Software Industry. Availableonline. URL: http://www.plunkettresearch.com/Industries/InfoTechComputersSoftware/tabid/152/Default.aspx. Accessed June 24, 2007.Yost, Jeffrey R. The Computer Industry. Westport, Conn.: GreenwoodPress, 2005.ZDNet. Available online. URL: http://www.zdnet.com/. AccessedJune 24, 2007.computer literacyAs computers became integral to business, industry, trades,and professions, educators and parents became increasinglyconcerned that young people acquire a basic understandingof computers and master the related skills. Theterm computer literacy suggested that computer skills werenow as important as the traditional skills of reading, writing,and arithmetic. However, there has been disagreementabout the emphasis for a computer literacy curriculum.Some educators, such as Seymour Papert, computer scientistand inventor of the Logo language, believe that studentscan and should understand the concepts underlyingcomputing, and be able to write and appreciate a variety ofcomputer programs (see logo). By gaining an understandingof what computers can (and cannot) do, students willbe able to think critically about how to appropriately usethe machines, rather than simply mastering route skills.Indeed, by gaining a good grasp of general principles, thestudent should be able to easily master specific skills.An opposing view emphasizes the practical skills thatmost people (who will not become programmers) will needin everyday life and work. This sort of curriculum focuseson learning how to identify the parts of a computer andtheir functions, how to run popular applications suchas word processors, spreadsheets, and databases, how toconnect to the Internet and use its services, and so on.Computer literacy can also be broadened to include understandingthe impact that computers are having on dailylife and social issues that arise from computer use (such assecurity, privacy, and inequality).Today computer literacy is an important part of everyelementary and high school curriculum. Most students inmiddle-class or higher income brackets now have access tocomputers at home, and many thus gain considerable computerliteracy outside of school. In addition, adult educationand vocational schools often emphasize computer skills asa route to employment or career advancement. People alsohave the opportunity to learn on their own through booksand videos.The approach to computer literacy will vary with thebackground and resources of a given community. For example,programs for young people in developed countries cantake advantage of the fact that many young people alreadyhave considerable experience with using computers, includingrelated devices such as game consoles and music/videoplayers. On the other hand, a program targeted at a poor orminority community must cope with the likelihood thatmany members of the community have had little opportunityto interact with computers (see digital divide). Programsfor poor and developing countries may have to focusfirst on providing the basic infrastructure, as in the OneLaptop Per Child Program.Further ReadingGookin, Dan. PCs for Dummies. 10th ed. New York: Wiley, 2005.Jan’s Illustrated Computer Literacy 101. Available online. URL:http://www.jegsworks.com/Lessons/index.html. Accessed June24, 2007.Parsons, June, and Dan Oja. Practical Computer Literacy and Skills.Boston: Thomson Course Technology, 2004.White, Ron. How Computers Work. 8th ed. Indianapolis: Que,2005.computer scienceMost generally, computer science is the study of methodsfor organizing and processing data in computers. The fundamentalquestions of concern to computer scientists rangefrom foundations of theory to strategies for practical implementation.Fundamental Theory• What problems are susceptible to solving through anautomated procedure? (See computability and complexity.)• Given that a problem is solvable, can it be solvedwithout too much expenditure of time or computingresources?• Can a step-by-step procedure be devised for solvinga given problem? (See algorithm.) How do differentprocedures (such as for sorting data) compare in efficiencyand reliability? (See sorting and searching.)• What methods of organizing data are most useful?(See data structures.) What are the advantages anddrawbacks of particular forms of organization? (Seearray, list processing, and queue.)• Which structures are best for representing the dataneeded for a given application? What is the best wayto relate data to the procedures needed to manipulateit? (See encapsulation, class, and procedures andfunctions.)The Tools of Computing• How can programs be structured so they are easier toread and maintain? (See structured programmingand object-oriented programming.)• Can programmers keep up with growth of operatingsystems and application programs that have millionsof lines of code? (See software engineering andquality assurance, software.)• How can multiple simultaneous tasks (or even multipleprocessors) be coordinated to bring greatercomputing power to bear on problems? (See multitaskingand multiprocessing.)

110 computer virus• What is the best way to design an operating system,including the arrangement of different layers of theoperating system such as the hardware-specific drivers,kernel (essential functions), and interfaces (shellsor visual environments)? (See operating system,kernel, device driver, and shell.)• What should be emphasized in designing a programminglanguage? How does one specify the grammarof statements the declaration and handling of datatypes, and the mechanism for handling functions orprocedures? (See Backus-Naur form, data types,and procedures and functions.)• What considerations should be emphasized in designinga compiler for a given language? (See compiler.)• How should a network be organized, and what protocolsshould be used for transferring data? (Seenetwork, Internet, data communications, telecommunications,and tcp/ip.)Specific Application AreasThe general principles and tools must then be applied to avariety of application areas including:• text processing (see word processor, text editor,and font)• graphics (see computer graphics and image processing)• database management, including file structures andfile access (such as indexing and hashing), and databasearchitecture (relational databases) (see databasemanagement system, sql, and xml).• business data processing issues, including the designof MIS (management information systems) and decisionsupport systems• web applications, including commercial applications(see e-commerce), multimedia, database access, integrationof Web services (see bioinformatics serviceorientedarchitecture, mashups, and web 2.0 andbeyond), and appropriate programming techniques(see Ajax and scripting languages.)• scientific programming issues, including data acquisition,maintaining accuracy in calculations, andcreating visualizations driven by the data (see dataacquisition, numeric data and scientific computingapplications.)• user interface design (designing the interactionbetween human beings and the operating system orapplication) (see user interface)• the broad area of artificial intelligence, which affectsways of representing information and modeling reasoningprocesses (see artificial intelligence, neuralnetwork, expert systems, and knowledgerepresentation.)• robotics and control systems (an older term, “cybernetics,”has also been used for this field) (see roboticsand cybernetics.)Clearly the concerns of computer science overlap a numberof related fields. The design of computer hardware isoften considered to be computer engineering, but designersof hardware must be familiar with the algorithms that willbe used to operate it (see also computer engineering).Both artificial intelligence and user interface design areaffected by cognitive science (or psychology), the study ofhuman thought processes. Biology both inspires and is illuminatedby artificial life simulations, genetic algorithms,and neural networks. The most abstract questions of informationprocessing touch on the field of information science(or information theory).History of the FieldThe early computer pioneers such as Alan Turing, J. PresperEckert, and John Mauchly brought backgrounds inmathematics or engineering (see Turing, Alan; Eckert,J. Presper; and Mauchly, John). By the 1960s, however,a discipline and curriculum for computer science began toemerge. By the late 1990s more than 175 departments inAmerican and Canadian universities offered a doctorate incomputer science, with about a thousand new Ph.D.s beinggranted each year. However, in the following decade thenumber of students majoring in computer science declinedby about 50 percent. (See education in the computerfield for more details.)The traditional computer science field emphasizes thetheory of data representation, algorithms, and system architecture.In recent years a more practically oriented curriculumhas emerged as an alternative. Under the titles of“Information Technology” or “Information Systems,” thiscurriculum emphasizes application areas such as managementinformation systems, database management, systemadministration, and Web development.Further ReadingAssociation for Computing Machinery (ACM). Available online.URL: http://www.acm.org. Accessed June 24, 2007.Biermann, Alan W. Great Ideas of Computer Science with JAVA.Cambridge, Mass.: MIT Press, 2001.Computer Science [resources]. University of Albany Libraries.Available online. URL: http://library.albany.edu/subject/csci.htm. Accessed June 24, 2007.Dale, Nell, and John Lewis. Computer Science Illuminated. 3rd ed.Sudbury, Mass.: Jones & Bartlett, 2006.Hillis, Daniel W. The Pattern on the Stone: The Simple Ideas ThatMake Computers Work. New York: Basic Books, 1998.IEEE Computer Society. Available online. URL: http://www.computer.org/portal/site/ieeecs/index.jsp.Accessed June 24,2007.computer virusA computer virus is a program that is designed to copyitself into other programs. When the other programs arerun, they carry out the virus’s instructions, either instead ofor in addition to their own. Since one of the primary tasks

computer virus 111programmed into a virus is to reproduce itself, a virus programcan spread rapidly. Viruses are generally programmedto seek out program files that are likely to be executed inthe near future, such as those used by the operating systemduring the startup process. The result is a copy that canin turn generate an additional copy, and so on. (A virusdisguised as an innocuous program is sometimes calleda Trojan, short for “Trojan horse.” A distinction is sometimesmade between viruses and worms. A worm generallyuses flaws in a networking system to send copies to othermachines, without needing to insert code into a program.)Appearing in the 1980s, the first computer viruses weregenerally spread by infecting programs on floppy disks,which were often passed between users. Today, viruses generallyhave instructions that enable them to gain access tonetwork facilities (such as e-mail) to facilitate their spreadingto other systems on a local network or on the Internet.The spread of viruses is complicated by the fact that operatingsystems (particularly Microsoft Windows) and applications(such as Microsoft Office) have the ability to runscripts or “macros” that are attached to documents. Thisfacility can be useful for tasks such as sophisticated documentformatting or form-handling, but it also means thatviruses can attach themselves to scripts or macros and runwhenever a document containing them is opened. Sincemodern e-mail programs have the ability to include documentsas attachments to messages, this means that theunsuspecting recipient of a message can trigger a virus simplyby opening a message attachment.In today’s Web-centric world, viruses are often spreadusing links in e-mail that either entices or frightens thereader into clicking on a link to a Web site, which canbe made to closely resemble that of a legitimate institutionsuch as a bank or e-commerce site (see phishing andspoofing). Once connected to the site, the user’s computercan be infected with a virus or with some other form of“malware” (see spyware and adware). This route of infectionis particularly dangerous because normal antivirusprograms scan e-mail but not data being downloaded froma Web site, and firewalls are generally set to allow normalWeb requests.Once installed, a virus can be used for a variety of purposesaccording to the “payload” of instructions that areset to execute. Sensitive information such as credit carddetails can be stolen (see identity theft). Sometimes theinfected computer can appear to be unaffected, but has hada stealthy “bot” (robot) program inserted. Thousands ofbots can be linked into a “botnet” and later commanded totrigger large-scale “distributed denial of service” (DDOS)attacks to flood targeted Web sites with requests, crashingor disabling the site.Viruses can be further disguised by programming themto remain dormant until a certain date, time, or other conditionis reached. (Such a virus is sometimes called a logicbomb.) For example, a disgruntled programmer who isabout to be dismissed might insert a virus that will wipeout payroll data at the beginning of the next month. Afamous example of the time-triggered virus was the Michelangelovirus, so named because it was triggered to run onthe artist’s birthday, March 6, 1992. (See computer crimeand security.)Viruses can be overtly destructive (such as by reformattinga computer’s hard drive, wiping out its data). Otherviruses can simply tie up system resources. The most infamousexample of this was the “Internet Worm” introducedonto the network on November 2, 1988, by Robert Morris,Jr. This program was intended to reproduce slowly, plantingits “segments” on networked computers by exploiting aflaw in the UNIX sendmail program. Unfortunately, Morrismade an error that caused the worm to spread much morerapidly. Before the coordinated efforts of system administratorsat affected sites came up with countermeasures, theworm had cost somewhere in the hundreds of thousands ofdollars in lost computer and programmer time.CountermeasuresThe only certain defense of a computer system from viruseswould be through abstaining from contact between it andany other computers, either directly through a network orindirectly through exchange of programs on floppy disksor other removable media. In today’s highly networkedworld, this is usually impractical. A more practical defenseis to install antivirus software. Antivirus programs workby comparing the contents of files (either those already onthe disk or entering via the Internet) with “signatures” orpatterns of data found in known viruses. More sophisticatedantivirus programs include the ability to recognizeprogram code that is similar to that found in known virusesor that attempts suspicious operations (such as attempts toreformat a disk or bypass the operating system and writedirectly to disk). If an antivirus program recognizes a virus,it warns the user and can be told to actually remove thevirus. Because dozens of new viruses are identified eachweek, virus programs must be updated frequently with newvirus signature files in order to remain effective. Many antivirusprograms can update themselves by periodically linkingto a Web site containing the update files.Modern operating systems (such as Microsoft WindowsVista) have attempted to make it harder for unauthorizedprograms to access critical system files, such as by limitingdefault access permissions or prompting the user toapprove various activities. Such operating systems alsoinclude an updating feature that can automatically downloadand install security “patches”—a vital task, as can beseen from the volume and variety of such updates that seemto appear every month. Indeed the use of “blended” threats(including more than one potential infection mechanism)and the development of new “exploits” for hundreds of differentdata file formats make system protection an ongoingchallenge.Reducing user temptation and enhancing user awarenessis also important. Since unsolicited e-mail (see spam)is often a source of potentially malicious links and attachments,running a spam-blocking program can help protectthe computer. There are also programs that can detectand block “phishing” messages and their related Web sites.Since none of these programs can completely keep up withthe rapid appearance of new threats, caution and common

112 computer visionsense on the part of the user remain an important last lineof defense.Further ReadingAntivirus Software Buying Guide. PC World. Available online. URL:http://www.pcworld.idg.com.au/index.php/id;316975074.Accessed June 24, 2007.CERT Coordination Center. Available online. URL: http://www.cert.org. Accessed June 24, 2007.Gregory, Peter H. Computer Viruses for Dummies. Indianapolis:Wiley, 2004.Henderson, Harry. Computer Viruses. Detroit: Lucent Books/Thomson-Gale,2006.McAfee Corporation. Available online. URL: http://www.mcafee.com. Accessed June 24, 2007.Symantec Corporation. Available online. URL: http://www.symantec.com. Accessed June 24, 2007.computer visionIn the biological world, vision is the process of receivinglight signals from the environment through the eyes andoptic nerves, from which the brain can extract patternsthat contain useful information (such as recognizing foodor a potential predator). Computer vision (also known asmachine vision) is the analogous process by which lightis received by a sensor system (such as a digital camera).The light is then analyzed for meaningful patterns. Thus, arobot might be able to recognize the identity and positionsof various parts on an assembly line.Because computer vision involves pattern recognition, itis part of the discipline of artificial intelligence (see artificialintelligence and pattern recognition). The challengeis not in getting information about a visual scene fromthe camera and turning it into digital information (a grid ofpixels). Rather, it is the ability to recognize meaningful patternsin fragmented images, something human infants learnto do almost from birth when they encounter human faces.One way to approach the problem is to constrain thekinds of images the computer (or robot) has to deal with.If you can guarantee that a robot’s field of vision will containonly a few fixed objects (a hopper, perhaps, or a conveyerbelt) plus one or more distinctively shaped parts, itis relatively easy to program the dimensions of the possibleobjects into the vision system so that the robot can identifyobjects by comparing them with stored templates. However,if the robot encounters an object it isn’t prepared for, suchas a stray bit of packing material, it will be unable to identify(or properly deal) with the object.Vision is also complicated by the problem of parsingthree-dimensional objects in the visual field. Seen headon,the side of a cube appears to be a two-dimensionalsquare. Seen at an angle, it appears to be a three-dimensionalassemblage with some faces visible and some not.To interpret these and more complicated objects, the robotmight be programmed with rules that help it infer that anobject is really a cube, that all cubes have six equal sides,and so on. Another strategy is to give the robot more thanone “eye” so that images can be compared, much as humansdo unconsciously with binocular vision. Finally, the robotcan be given the ability to move its head and eyes in orderto find a viewpoint that yields more information about anambiguous object.Human infants, of course, are not born with a fullydeveloped understanding of the types of objects in theirworld. They are always learning new ways to distinguish,for example, a stuffed teddy bear from a live dog. Robotvision systems, too, can be programmed to learn (or at least,refine their ability to recognize objects). A statistical techniquecan be used to “sample” objects in the environmentand find which characteristics most reliably “predict” thetrue nature of an object. Characteristics can be resampledfrom different viewpoints to see which ones remain invariant(unchanged). For example, a cube will always have fouredges on each face. Another approach is to use a neural network,where the visual information is processed by a grid ofnodes that are reinforced to the extent they are successfulin identifying features (such as edges).ApplicationsComputer vision is a problem of great theoretical interestbecause it engages so many questions about perception,the ability to build models of the world, and the ability tolearn. The field also has considerable practical potential.Currently, most robots are fixed to stations on factory floorswhere they work with a limited number of objects (parts)in a highly constrained, stable environment. However “servicerobots” have been gradually developed to work in amuch less constrained environment (such as carrying suppliesdown hospital corridors or even serving as mobileassistants to astronauts in the weightless environment ofthe International Space Station). These robots would benefitgreatly by having robust vision systems so that they can, forexample, recognize individual human faces or detect potentiallydangerous situations.Of course computer vision systems find many applicationsbesides robotics. These include automatic quality controlor inventory management systems, advanced medicalimaging and computer-assisted surgery, as well as security,surveillance, and criminal investigation/forensics.Further ReadingDavies, E. R. Machine Vision: Theory, Algorithms, Practicalities. 3rded. San Francisco: Morgan Kaufmann, 2004.Henderson, Harry. Modern Robotics: Building Versatile Machines.New York: Chelsea House Publishers, 2006.Hornberg, Alexander, ed. Handbook of Machine Vision. Weinheim,Germany: Wiley-VCH, 2006.Machine Vision Online. Automated Imaging Association. Availableonline. URL: http://www.machinevisiononline.org/.Accessed June 24, 2007.Shapiro, Linda G., and George Stockman. Computer Vision. UpperSaddle River, N.J.: Prentice Hall, 2001.concurrent programmingTraditional computer programs do only one thing at a time.Execution begins at a specified point and proceeds accordingto decision statements or loops that control the processing.This means that a program generally cannot begin onestep until a previous step ends.

concurrent programming 113Concurrent programming is the organization of programsso that two or more tasks can be executed at thesame time. Each task is called a thread. Each thread is itselfa traditional sequentially ordered program. One advantageof concurrent programming is that the processor can beused more efficiently. For example, instead of waiting forthe user to enter some data, then performing calculations,then waiting for more data, a concurrent program can havea data-gathering thread and a data-processing thread. Thedata-processing thread can work on previously gathereddata while the data-gathering thread waits for the user toenter more data. The same principle is used in multitaskingoperating systems such as UNIX or Microsoft Windows.If the system has only a single processor, the programsare allocated “slices” of processor time according to somescheme of priorities. The result is that while the processorcan be executing only one task (program) at a time, forpractical purposes it appears that all the programs are runningsimultaneously (see multitasking).Multiprocessing involves the use of more than one processoror processor “core.” In such a system each task (or eveneach thread within a task) might be assigned its own processor.Multiprocessing is particularly useful for programs thatinvolve intensive calculations, such as image processing orpattern recognition systems (see multiprocessing).Programming IssuesRegular programs written for operating systems such asMicrosoft Windows generally require no special codeto deal with the multitasking environment, because theoperating system itself will handle the scheduling. (Thisis true with preemptive multitasking, which has generallysupplanted an earlier scheme where programs were responsiblefor yielding control so the operating system could giveanother program a turn.)Managing threads within a program, however, requiresthe use of programming languages that have special statements.Depending on the language, a thread might bestarted by a fork statement, or it might be coded in a waysimilar to a traditional subroutine or procedure. (The differenceis that the main program continues to run while theprocedure runs, rather than waiting for the procedure toreturn with the results of its processing.)The coordination of threads is a key issue in concurrentprogramming. Most problems arise when two or morethreads must use the same resource, such as a processorregister (at the machine language level) or the contentsof the same variable. Let’s say two threads, A and B, havestatements such as: Counter = Counter + 1. Thread A getsthe value of Counter (let’s say it’s 10) and adds one to it.Meanwhile, thread B has also fetched the value 10 fromCounter. Thread A now stores 11 back in counter. ThreadB, now adds 1 and stores 11 back in Counter. The result isthat Counter, which should be 12 after both threads haveprocessed it, contains only 11. A situation where the resultdepends on which thread gets to execute first is called arace condition.One way to prevent race conditions is to specify thatcode that deals with shared resources have the ability to“lock” the resource until it is finished. If thread A can lockthe value of Counter, thread B cannot begin to work with ituntil thread A is finished and releases it. In hardware terms,this can be done on a single-processor system by disablinginterrupts, which prevents any other thread from gainingaccess to the processor. In multiprocessor systems, an interlockmechanism allows one thread to lock a memory locationso that it can’t be accessed by any other thread. Thiscoordination can be achieved in software through the useof a semaphore, a variable that can be used by two threadsto signal when it is safe for the other to resume processing.In this scheme, of course, it is important that a threadnot “forget” to release the semaphore, or execution of theblocked thread will halt indefinitely.A more sophisticated method involves the use of messagepassing, where processes or threads can send a varietyof messages to one another. A message can be used to passdata (when the two threads don’t have access to a sharedmemory location). It can also be used to relinquish accessto a resource that can only be used by one process at a time.Message-passing can be used to coordinate programs orthreads running on a distributed system where differentthreads may not only be using different processors, but runningon separate machines (a cluster computing facility).Programming language support for concurrent programmingoriginally came through devising new dialectsof existing languages (such as Concurrent Pascal), buildingfacilities into new languages (such as Modula-2), or creatingprogram libraries for languages such as C and C++.However, in recent years concurrent programming languagesand techniques have been unable to keep up withthe growth in multiprocessor computers and distributedcomputing (such as “clusters” of coordinated machines).With most new desktop PCs having two or more processingcores, there is a pressing need to develop new programsthat can carry out tasks (such as image processing) usingmultiple streams of execution. Meanwhile, in very highperformancemachines (see supercomputer), the DefenseAdvanced Research Projects Agency (DARPA) has been tryingto work with manufacturers to develop languages towork better with computers that may have hundreds ofprocessors as well as distributed systems or clusters. Suchlanguages include Sun’s Fortress, intended as a modernreplacement for Fortran for scientific applications.The new generation of concurrent languages tries toautomate much of the allocation of processing, allowingprogrammers to focus on their algorithms rather thanimplementation issues. For example, program structuressuch as loops can be automatically “parallelized,” such asby assigning them to separate cores.Further ReadingAnthes, Gary. “Languages for Supercomputing Get ‘Suped’ Up.”Computerworld.com, March 12, 2007. Available online. URL:http://www.computerworld.com/action/article.do?command=viewArticleBasic&articleId=283477&intsrc=hm_list.Accessed June 24, 2007.Ben-Ari, M. Principles of Concurrent & Distributed Programming.2nd ed. Reading, Mass.: Addison-Wesley, 2006.

114 conferencing systemsFeldman, Michael. “Our Manycore Future.” HPCWire. Availableonline. URL: http://www.hpcwire.com/hpc/1295541.html.Accessed June 24, 2007.Lea, Douglas. Concurrent Programming in Java: Design Principlesand Patterns. 3rd ed. Reading, Mass.: Addison-Wesley Professional,2006.Merritt, Rick. “Where Are the Programmers? Enrollment WanesJust as Computer Scientists Grapple with Problem of Parallelism.”IEEE Times, March 12, 2007. Available online. URL:http://www.eetimes.com/showArticle.jhtml?articleID=197801653. Accessed June 24, 2007.Steele, Guy, and Jan-Willem Maessen. “Fortress ProgrammingLanguage Tutorial Slides.” Sun Microsystems. Availableonline. URL: http://research.sun.com/projects/plrg/PLDITutorialSlides9Jun2006.pdf.Accessed June 11, 2007.conferencing systemsConferencing systems are online communications facilitiesthat allow users to log in and participate in discussions ona variety of topics. Although this is a rather amorphous categoryof software, some distinguishing characteristics canbe identified. Conferencing is distinguished from chat orinstant messaging systems because the messages are asynchronous(that is, one person at a time leaves a message,and there is no real-time interaction between participants).Unlike Netnews newsgroups, conferencing systems such asSan Francisco Bay Area–based The Well tend to have userswho are committed to long-term discussions in conferences(topical discussion areas) that tend to persist for weeks,months, or even years. Conferencing systems are oftengrouped under the umbrella term of Computer-MediatedCommunications (CMC).HistoryIn the 1960s, researcher Murray Turoff at the Institute forDefense Analysis decided to adopt for computer use a discussionmethod called Delphi, developed at RAND corporation.This method was a collective process by which newideas were discussed and voted on by a panel of experts.After he implemented Delphi as a system of messages passedvia computer, he began to generalize his work into a moregeneral method of facilitating online discussions. His ElectronicInformation Exchange System (EIES, pronounced“eyes”) was designed to facilitate discussion within researchcommunities of 10–50 members.The emergence of topical online discussions can be seenin the development of the Usenet (or Netnews) newsgroupsin the early 1980s, the development of communicationsor memo systems within large offices (particularly withinthe government), and the emergence of bulletin boards andonline services for personal computer users. Most earlynews and bulletin board software had only rudimentaryfacilities for linking topics and responses. A more sophisticatedapproach to conferencing emerged within the PLATOeducational computing network in the 1970s, in the form ofPlato Notes. This system began as a simple way for users toleave messages or help requests in a text file, and evolvedinto a structure of “base notes” and linked response notes, atopic-and-response structure that became the general modelfor conferencing systems.In the mid-1980s, the Well (Whole Earth ’Lectronic’Link) began to provide online conferencing to anyone whosubscribed. It used a text-based system called Picospan.With its improbable eclectic mix well salted with GratefulDead fans and computer “nerds,” the Well became asort of petri dish for cultivating community (see virtualcommunity). Long-term friendships (and feuds) and occasionalromances have been nurtured by such conferencingsystems.Typical StructureA typical text-based conferencing system is divided intoconferences, which are generally devoted to relatively broadsubjects, such as UNIX, pop music, or politics. Each conferenceis further divided into topics, which usually reflectparticular aspects of the general subject (such as a particularUNIX version, a pop music group, or a political issue).Most conferencing systems have a person or persons whoact as a moderator (sometimes called a “host”) who triesto encourage new users, keep discussions more or less ontopic, and discourage personal attacks or vehement statements(“flames”).A user signs onto the system and “joins” one or moreconferences. Each time the user visits a conference that heor she has joined, any topics (or responses in existing topics)that were posted since the last visit are presented. Theuser can read the postings and, if desired, enter a reply thatbecomes part of the thread of messages. (Users are also generallyallowed to start new topics of their own.)Web-based ConferencingText-based systems such as Picospan are driven by the userentering command letters or words. While this paradigmis familiar to people who have experience with operatingsystems such as UNIX or MS-DOS, it can be more difficultfor users who are used to the point-and-click approachof Windows programs and the World Wide Web. Manynew conferencing systems use Web pages to present conferencetopics and messages, with buttons replacing text commands.(The Well continues to offer both the text-basedPicospan and the Web-based Engaged.)Although the Well and other conferencing systems suchas The River continue in operation, conferencing systemshave been largely supplanted by newer forms of onlineexpression (see blogs and blogging, social networking,and wikis and Wikipedia). (Note that “conferencingsystem” can also refer to video-based software such asMicrosoft Live Meeting for facilitating meetings betweengeographically dispersed participants.)Further ReadingHafner, Katie. The Well: A Story of Love, Death & Real Life in theSeminal Online Community. New York: Carroll & Graf, 2001.Rheingold, Howard. The Virtual Community: Homesteading on theElectronic Frontier. Rev. ed. Cambridge, Mass.: MIT Press,2000.Thurlow, Crispin, Laura Lengel, and Alice Tomic. Computer MediatedCommunication. Thousand Oaks, Calif.: SAGE Publications,2004.

content management 115Web Conferencing Review. Available online. URL: http://thinkofit.com/webconf/index.htm. Accessed June 25, 2007.The Well. Available online. URL: http://www.well.com. AccessedJune 25, 2007.constants and literalsConstants and literals are ways of describing data that doesnot change while a program runs. For example, a statementin C such asconst float pi = 3.14159;expresses a value that will be used in calculations, butnot changed. Constants can be of any data type, includingcharacter strings as well as numbers. String constants areusually enclosed in single or double quotes:char * Greeting = “Hello, World”;Actual strings and numerals found in programs are sometimescalled literals, meaning that they are to be acceptedexactly as given (literally) rather than standing for someother value. Thus 3.14159 and Hello, World as givenabove can be considered to be numeric and string literalsrespectively.Because many languages consider a value of 1 as representinga “true” result for a branch or loop test, and 0 asrepresenting “false,” programs in languages such as C ofteninclude declarations such as:const True = 1;const False = 0;This lets you later have a loop construction such aswhile (True) {’ body of program} ;which is a more readable way to code an endless loop than:while (1) {’ body of program} ;However languages such as Pascal and C++ have a specialboolean data type (bool in C++) that allows for constants orvariables that will have one of two values, true or false.Some languages provide a way to set up an orderedgroup of constant values (see enumerations and sets).Constants vs. VariablesThe difference between a constant and a variable is that avariable represents a quantity that can change (and is oftenexpected to). For example, in the statementint Counter = 0;Counter is set to a starting value of zero, but will presumablybe increased as whatever is to be counted is counted.Most compilers will issue an error message if they detectan attempt to change the value of a constant. Thus thesequence of statements:const float Tax_Rate = 8.25;Tax_Rate = Tax_Rate + Surtax;would be illegal, since Tax_Rate was declared as a constantrather than as a variable.Many compilers, as part of code optimization, candiscover values or expressions that will remain constantthroughout the life of the program, even if they includevariables. Such constants can be “propagated” or substitutedfor variables. This can speed up execution becauseunlike a variable, a constant does not need to be retrievedfrom memory (see compiler).Further ReadingSebesta, Robert W. Concepts of Programming Languages. 8th ed.Reading, Mass.: Addison-Wesley, 2007.content managementContent management is the process of creating, maintaining,and archiving data such as text and images to be usedfor a project such as a book, magazine, or Web site. Normallysuch projects involve a number of different people:content creators (such as writers or photographers), editors,reviewers, designers, and so on. A large project willoften have many documents in various stages—early drafts,material approved for publication, existing publications inneed of revision, older material ready to be archived, andso on.The purpose of content management is to make sureevery piece of a project has its status tracked, includingwho has worked on it and what has been done (or needs tobe done). Because more than one person may want to workon a given piece at the same time, some form of “versioncontrol” (as with program code) must be used to either“lock” the material while one person is using it, or to mergetheir separate work into a new version of the document.Naturally there must also be a way for members of the teamto communicate with each other in connection with specificparts of the project, and all members must be kept informedof key developments.Work FlowA key measurement of the effectiveness of a content managementsystem (CMS) is how well it facilitates work flow,or the movement of documents through the production process.Work flow begins with the importing of material suchas text documents or multimedia resources into the system.At this time the key users and their roles (such as editor orreviewer) are identified, and the system can then route thematerial to the next person automatically after each task iscompleted. Often messages are generated and sent to managersto keep them informed of progress or to alert them toproblems.Today Web sites are the most common large information-relatedprojects, and managing them can be quitechallenging. Usually multimedia material is included wellbeyond that found in printed projects, such as audio, video,animations, and information feeds (see rss). Web sites,

116 cookiesunlike most traditional publications, are under constantrevision and review.Once created, material will often be reused or repurposedfor different projects. Thus an important part of most contentmanagement systems is the repository, which makes thematerial easily searchable and retrievable for later use. Materialthat is less likely to be used but still must be retained(such as for legal reasons) may be stored in a separate archive(see backup and archive systems). Note: The term digitalasset management is also sometimes used for such systems.SoftwareContent management Systems are usually built upon aframework or programming interface (see applicationprogram interface), often using languages such as Java,Perl, Python, or PHP. There are many products to choosefrom, including free and open-source alternatives.An interesting alternative for some projects is to usea wiki as a content management system (see wikis andWikipedia). Especially for textual content, wikis offer theadvantage of already having revision tracking built in, andfull-scale wikis such as MediaWiki have many additionalfeatures or plug-ins to aid in content management.Further ReadingBoiko, Bob. Content Management Bible. 2nd ed. Indianapolis:Wiley, 2005.CMS Matrix. Available online. URL: http://www.cmsmatrix.org/.Accessed September 4, 2007.CMS Review. Available online. URL: http://www.cmsreview.com/.Accessed September 4, 2007.Hackos, JoAnn T. Content Management for Dynamic Web Delivery.New York: Wiley, 2001.cookiesCookies are simply tiny text files that a Web server sendsto the browser and retrieves each time the user accesses theWeb site. The purpose is to maintain a sort of profile of theuser containing such things as preferences as to how theuser wants to view or use the site, shopping cart selectionsfrom previous sessions, and so on. In short, cookies enable aWeb site to provide a more customized or personalized formof service and minimize the amount of repetitive data entryon the part of the user. (This type of cookie is called persistent,since it survives across sessions. There can also be temporarycookies that apply only to the current session.)However, cookies also have benefits for the Web siteowner. They can be used to track which pages or items theuser has looked at in the past. This information can then beused (see data mining) to create generic user profiles thatcan help with marketing or targeting advertising. In thecase of some companies (notably Amazon.com) much moreelaborate profiles associated with the cookie’s identity canbe used to create personalized recommendations, in effectcontinually directing targeted advertising at the user.Security and Privacy ConcernsThere are many popular misconceptions about cookies.Cookies contain only data, not executable code. This meansthey cannot function as worms or viruses or otherwiseinteract with the user’s system. However, while cookies donot in themselves represent a security threat, they do haveprivacy implications. Although most profiles created usingcookies are anonymous (containing no personal identifyingdata), an unscrupulous site could attach such data (such asaddresses or credit card numbers entered by the user) to aprofile and sell it for purposes ranging from spamming toidentity theft.Another risk comes from “third party” cookies such asare often included in advertisements (see online advertising).Potentially, these could be used to create a much morecomprehensive profile of a user based on his or her actionson multiple Web sites.Users do have some control over how cookies are stored.Most browsers allow the user to reject all cookies, accept orreject cookies from certain sites, or store cookies only temporarily.However, sites may in turn refuse services to userswho do not accept cookies, and at any rate the user wouldsee only a generic rather than a personalized view.There has been a certain amount of government regulationof Web cookies. The U.S. government has strict rulesfor the use of cookies on federal Web sites. The EuropeanUnion also has recommended (but not fully implemented)regulations that require that users be told how the storeddata will be used and be given the opportunity to opt out.Further ReadingKuner, Christopher. European Data Privacy Laws and Online Business.New York: Oxford University Press, 2003.Kymin, Jennifer. “What are HTTP Cookies?” Available online. URL:http://webdesign.about.com/cs/cookies/a/aa082498a.htm.Accessed September 4, 2007.Levine, John R., Ray Everett-Church, and Gregg Stebben. InternetPrivacy for Dummies. New York: Wiley, 2002.cooperative processingHistorically there have been two basic ways to bring greatercomputer power to bear on a task. One is to build morepowerful single computers (see supercomputer). The otheris to link one or more computers or processors together andtightly coordinate them to process the data (see grid computing).Both of these approaches require great expertiseand considerable expense.However, there is another quite interesting ad hocapproach to cooperative processing that first appeared withthe SETI@Home project launched in 1999. The basic idea isto take advantage of the fact that millions of computer usersare already connected via the Internet. The typical PC hasmany processing cycles to spare—idle time when the user isdoing nothing and the operating system is doing very little.A program like SETI@Home is designed to be downloadedto volunteer users. The program can run only whenno other applications are being used (one way to ensurethis is to make the program a screen saver), or it can runcontinuously but only use cycles not being requested byanother program.The data to be analyzed (signals from space in this case)is broken up into chunks or “work units” that are parceled

copy protection 117out to the volunteers. When a given unit has been analyzedby the program on the user’s machine, the results are sentback to the central server and a new work unit is sent.Although no evidence of extraterrestrial intelligencehad been found as of mid-2008, SETI@Home’s more than 5million participants have contributed more than 2 millionyears of CPU time, and can process at the collective rate of256 TeraFLOPS (trillion floating point operations per second),comparable with the fastest single supercomputers.There are currently a number of other cooperative distributedcomputing projects underway. Many of them arepart of the Berkeley Open Infrastructure for Network Computing(BOINC), which includes SETI@Home, Proteins@home (protein folding), and the World Community Grid(humanitarian projects).Ad hoc cooperative processing is not suitable for alltypes of projects. There must be a way to break the datainto batches that can be separately processed. The projectis also dependent on the number of volunteers and theirdegree of commitment.Cooperative processing can be seen as part of a spectrumof emerging ways in which the line between producersand consumers of data is being blurred. Other examplesinclude media-sharing services such as Gnutella (see filesharingand p2p networks). Cooperative programs canalso be used to gather information about software use andbugs from thousands of users to allow for faster debuggingand optimization.People can do more than passively share their computer’sprocessors—they can add their own brains tothe effort. Some of the most effective spam filters (seespam) use the “collective intelligence” of users by havingthem identify and mark spam messages, which can thenbe used by the software as a template for automaticallyrejecting similar messages. Another interesting applicationby the Carnegie Mellon Human Computation programuses a computer game where a pair of randomlyselected volunteers assigns keywords to an image. Forthe players, the object of the game is to come up withmatching keywords, thereby scoring points. However, thereal work that is being accomplished is that thousands ofpreviously uncategorized images are receiving appropriatekeywords to enable them to be retrieved. In effect,the system is taking advantage of an image-recognitiondevice that is far more capable than any computer algorithm—thehuman brain! (One might call this synergistichuman–computer processing.)Further ReadingBerkeley Open Infrastructure for Network Computing. Availableonline. URL: http://boinc.berkeley.edu/. Accessed September4, 2007.DeHon, Andre, et al. “Global Cooperative Computing.” Availableonline. URL: http://www.ai.mit.edu/projects/iiip/colab/gcc-abstract.html. Accessed September 4, 2007.Gomes, Lee. “Computer Scientists Pull a Tom Sawyer.” WallStreet Journal (June 27, 2007): p. B1. Available online. URL:http://online.wsj.com/article/SB118288538741648871.html.Accessed September 4, 2007.SETI@Home. Available online. URL: http://setiathome.berkeley.edu/. Accessed September 4, 2007.Shankland, Stephen. “Cooperative Computing Finds Top PrimeNumber.” ZDNet. Available online. URL: http://news.zdnet.com/2100-9584_22-5112827.html. Accessed September 4,2007.Taylor, Ian J. From P2P to Web Services and Grids: Peers in a Client/Server World. New York: Springer, 2004.copy protectionCompanies that produce software have had to cope withsoftware that is expensive to develop, while the disks onwhich it is distributed are inexpensive to reproduce. Themaking and swapping of “pirated” copies of software isjust about as old as the personal computer itself. Softwarepiracy has taken a number of forms, ranging from teenagedhackers making extra copies of games to factories (often inAsia) that stamp out thousands of bogus copies of Windowsoperating systems and programs that would cost hundredsof dollars apiece if legitimate (see software piracy andcounterfeiting).To prevent such copying, software producers in the1980s often recorded the programs on floppy disks in a specialformat that made them hard to copy successfully. Oneway to do this is to record key information on disk tracksthat are not normally read by the operating system and thusnot reproduced by an ordinary copy command. When sucha program runs, it can use a special device control routineto read the “hidden” track. If it does not find the identifyinginformation there, it knows the disk is not a legitimate copy.Another way to do copy protection is by having theprogram look for a small hardware device called a “dongle”connected to the computer, usually to the parallel printerport. Since the dongle is distributed only with the legitimateprogram, it can serve as an effective form of copyprotection. (Encryption can also be used to render copiesunusable without the key.)Decline of Copy ProtectionCopy protection has a number of drawbacks. Because diskbasedcopy protection writes on nonstandard tracks, evenlegitimate programs may not work with certain models ofdisk or CD drive. And because the legitimate user is unableto make a backup copy of the disk, if it is damaged, the userwill be unable to use the program. Dongles, on the otherhand, can interfere with the operation of other devices connectedto the port, and a user might be required to use multipledongles for multiple programs.During the 1990s, copy protection was generally phasedout, except for some games. A variety of other strategies areused against software piracy. The Software Publishers Association(SPA) maintains a program in which disgruntledusers can report unauthorized copying of software at theirworkplace. Companies that allow unauthorized copying ofsoftware can be sued for violating the terms of their softwarelicense. International trade negotiations can includeprovisions for cracking down on the massive “cloning” ofmajor software packages abroad.With modern software, “soft” copy protection generallystill exists in the form of requiring the typing in of aserial number from the CD, often combined with online

118 CORBA“activation” or “validation,” as with Microsoft Windowsand Office products. The online validation process canforestall the use of valid but duplicated serial numbers(see digital rights management and software piracyand counterfeiting).Hackers and cyber-libertarians have often argued thatthe problem of software piracy has been overrated, andthat allowing the copying of software would enable morepeople who would not otherwise buy programs to try themout. Once someone likes the program, they might buy itnot only for legitimacy of ownership, but in order to getaccess to the technical support and regular upgrades thatare often required for complex business software packages.For less expensive software, an alternative channel (seeshareware) allows for a “try before you buy” distributionof software.Further ReadingAldrich, John. “Implementing Simple Copy Protection: TechnicalOverview.” Available online. URL: http://www.codeproject.com/win32/simplecopyprotection.asp?df=100&foru mid=4250&exp=0&select=878288. Accessed September 6, 2007.Gilmore, John. “What’s Wrong with Copy Protection.” February16, 2001. Available online. URL: http://www.toad.com/gnu/whatswrong.html. Accessed September 6, 2007.Wikipedia. “Copy Protection.” Available online. URL: http://en.wikipedia.org/wiki/Copy_protection. Accessed September6, 2007.CORBA (Common Object Request BrokerArchitecture)CORBA (Common Object Request Broker Architecture) is astandardized way to specify how different applications (onthe same or different machines) can call upon the servicesof database objects (see database and object-orientedprogramming). The CORBA standard is defined by theObject Management Group (OMG), a consortium of morethan 700 companies or organizations, including the majorplayers in distributed database technology.Structure and UsageCreating a CORBA application involves three basic steps.First, specifications are provided using an interface definitionlanguage (IDL) that specifies in generic terms whatservices an object will provide. An IDL compiler then createsa “skeleton” interface that the developer can fill in withactual code for a class for that object in a programming language(such as Java).To use CORBA, a client application accesses an ObjectRequest Broker (ORB), which is software that locates thereferenced object on the network (thus the program doesnot need to know or keep track of specific locations). TheORB sends the request to the object, which processes it andreturns the results, which are then sent back to the clientapplication.The intent of CORBA is to make objects implementedby different vendors fully interoperable (able to call oneanother using the same syntax). While CORBA 1.0 did notcompletely meet this goal, CORBA 2.0 explicitly providedfor a protocol called IIOP (Internet Inter-ORB Protocol)that, if adhered to, does make brokers (ORBs) and objectsinteroperable across vendors and programming languages.CORBA 3 adds a new CORBA Component Model (CCM)and specifications that, among other things, provide forbetter negotiation with firewalls, a problem that had madeCORBA hard to use in Web development.Corba ServicesIn addition to the interfaces defined for particular objects,CORBA provides a number of services that apply to allobjects. These services include creating, moving/copying,or removing objects; allowing more readable names forobjects; concurrency and transaction control; setting propertiesfor objects; and sending queries to objects.A competing framework for distributed object computingis COM/DCOM (Common Object Model/DistributedCommon Object Model, now supplanted by .NET (seeMicrosoft.net). A simpler (though possibly less secure)way to connect programs running on different machines isto use the Simple Object Access Protocol (see soap).Further ReadingBolton, Fintan. Pure CORBA. Indianapolis: Sams, 2001.“Introduction to CORBA” [Java implementation]. Availableonline. URL: http://java.sun.com/developer/onlineTraining/corba/corba.html. Accessed September 4, 2007.McHale, Ciaran. “CORBA Explained Simply, 2007.” Availableonline. URL: http://www.ciaranmchale.com/corba-explainedsimply/.Accessed September 4, 2007.counterterrorism and computersCounterterrorism is the effort to detect, identify, and neutralizeterrorist groups and prevent attacks. Not surprisingly,information technology plays a part in every phaseof this effort—and sometimes even becomes part of thebattlefield.Intelligence and SurveillanceThe Web and other Internet services are an important partof the battle against terrorism, not least because terroriststhemselves are beginning to use online tools effectively(see cyberterrorism). The Internet inherently allows forconsiderable anonymity (see anonymity and the Internet).However, any online activity leaves traces, howevervirtual, and surveillance, intelligence, and forensic techniquesare being adapted to this new medium (see computerforensics).By putting so much material online, terrorists are exposingthemselves to the increasingly sophisticated data miningand “semantic Web” tools that are being developed.These tools can, for example, identify material likely to beof interest (and summarize it) and even analyze the relationshipbetween individuals or groups based on their writingor verbal communications. Of course such results muststill be reviewed and acted upon by trained human analysts.Further, surveillance tools that are deployed too widely orindiscriminately are liable to raise privacy concerns.

CPU 119In recent years the U.S. Department of Homeland Securityhas apparently been developing more sophisticateddata-mining and pattern-recognition programs (see biometricsand data mining). One is called ADVISE, or Analysis,Dissemination, Visualization, Insight, and SemanticEnhancement. This at least suggests an attempt not to simplyfind matches between e-mail, online postings, or othertextual data, but to construct profiles of a person’s activityand/or intentions, which could presumably then be comparedwith terrorist or criminal profiles.Surveillance or wiretapping of specific individuals alsoraises legal issues, particularly with recent revelations ofso-called warrantless wiretaps. Officials have claimed thatthere are relatively few such cases (perhaps fewer than 100per year), but the Bush administration’s claim that it didnot need to follow Foreign Intelligence Surveillance Act(FISA) procedures raised considerable controversy, and acourt decision forced the administration to seek affirmationof its powers by Congress.Intelligence officials argue that existing FISA proceduresare too cumbersome to deal with the Internet. Oldstylewiretapping involved specific telephone instrumentsand lines, but on the Internet the routing of information isconstantly changing, and a person may use several differentdevices and types of communication. Thus it is argued thatthe warrant must be broad enough to apply to the person,not a particular means of communication. It is also arguedthat the global nature of the network also means that distinctionsabout whether persons are inside or outside of theUnited States may no longer be as relevant.Privacy and civil liberties advocates tend to agree thatsome updating of warrant procedures to deal with moderntechnology is necessary, but they point to secretivenessand lack of effective legal oversight resulting in a lackof accountability for government surveillance programs.This concern has also been fueled by a succession of revelationsthat surveillance programs are more extensivethan previously thought. (This includes the involvementof telecommunications and Internet service providersand the use of FBI “national security letters”—essentiallysecret subpoenas.)Coordinating EffortsBesides the gathering and analysis of intelligence, computerapplications are used in the intelligence and counterterrorismcommunity for many of the same functions foundin any large enterprise. These applications include e-mail,personal information management, collaborative creationor review of documents, scheduling and project management,and so on.Intelligence agencies are even adopting some popularemerging Web technologies. First came Intellipedia, a classifiedversion of Wikipedia serving as a knowledge basefor intelligence professionals (see wikis and Wikipedia).In late 2007 the director of national intelligence (DNI)launched A-Space, which includes Intellipedia, while addingother extensive databases, online office facilities (similarto Google Apps), and even blogs and a MySpace-likecomponent (see social networking).Further ReadingDerosa, Mary. Data Mining and Data Analysis for Counterterrorism.Washington, D.C.: Center for Strategic & International Studies,2004.Hoover, J. Nicholas. “U.S. Spy Agencies Go Web 2.0 in Effortto Better Share Information.” InformationWeek, August 23,2007. Available online. URL: http://www.informationweek.com/story/showArticle.jhtml?articleID=201801990. AccessedSeptember 10, 2007.Lichtblau, Eric. “F.B.I. Data Mining Reached beyond Initial Targets.”New York Times, September 9, 2007. Available online.URL: http://www.nytimes.com/2007/09/09/washington/09fbi.html. Accessed September 10, 2007.Miller, Greg. “Spy Chief Reveals Details of Operations.” Los AngelesTimes. Available online. URL: http://www.latimes.com/news/nationworld/nation/la-na-intel23aug23,0,6229712.story?coll=la-home-center. Accessed September 10, 2007.Mohammed, Arshad, and Sara Kehaulani Goo. “GovernmentIncreasingly Turning to Data Mining.” Washington Post,June 15, 2006, p. D03. Available online. URL: http://www.whisperingwires.info/. Accessed September 10, 2007.National Research Council. Information Technology for Counterterrorism:Immediate Actions and Future Possibilities. Washington,D.C.: National Academies Press, 2003.Taipale, K. A. “Whispering Wires and Warrantless Wiretaps: DataMining and Foreign Intelligence Surveillance.” Bulletin onLaw & Security, spring 2006. Available online. URL: http://www.whisperingwires.info/. Accessed September 10, 2007.CPUThe CPU, or central processing unit, is the heart of a computer,the place where data is brought in from input devices,processed, and sent to output devices. (This article describesthe CPU from the point of view of desktop micromputers,where it is a single large silicon chip and supporting chips;see mainframe for a discussion of that earlier architecture,microprocessor for desktop and portable CPUs, and chipand chipset for physical design of components.)The CPU consists of two major parts. The arithmeticlogicunit performs arithmetic or logical operations on pairsof numbers brought in from memory and stored in speciallocations called registers (see arithmetic logic unit). Forexample, the CPU can add a value from main memory toa value stored in a register and store the result back intomemory. In addition to addition, subtraction, multiplication,and division, the CPU can logically compare the individualbits in two values, performing such operations asAND, where the result is 1 only if both bits are ones, or OR,where the result is 1 if either bit is one. The power of a CPUis measured either in the number of clock cycles that driveit each second (see clock speed) or the number of standardinstructions it can execute in a second. For modern PCs,clock speeds range into the billions of cycles per second(gigahertz) and millions of instructions per second (mostinstructions take more than one cycle to be completed).The other key part of the CPU is the control unit, whichdetermines when (and which) instructions will be executed.Operations to be performed are specified by instruction valuesthat are the lowest level representation of program code,sometimes called machine code. An index register is usedto keep track of the current instruction. As instructions areprocessed, control signals can indicate special conditions,

120 CraigslistMano, M. Morris, and Charles Kime. Logic and Computer DesignFundamentals. 4th ed. Upper Saddle River, N.J.: Prentice Hall,2007.Stokes, Jon. Inside the Machine: An Illustrated Introduction to Microprocessorsand Computer Architecture. San Francisco: NoStarch Press, 2006.The CPU uses the Instruction Pointer (IP) to keep track of theaddress of the next instruction in memory, which is stored in theInstruction Register (IR). The Address Register (AR) and DataRegister (DR) perform a similar function with program data. Datacan also be moved between main memory and the CPU’s registers,which are special fast-retrieval memory locations. Instructions aredecoded by the control unit and passed to the arithmetic Logic Unit(ALU) for execution.such as a result being negative. Based on the instructionsand signals, the CPU can skip over some instructions, jumpingto another location in the program.The main memory or RAM (random access memory)contains both the program instructions and the data beingused by the program, which in turn can be read from adisk or other medium or written back to storage. The effectivespeed of the system is derived not only from the clockspeed but from the speed at which data travels over the systembus, a set of wires that each carry one data bit, as wellas the operating speed of the memory chips themselves (seeclock speed and bus).The access of programs to the CPU is controlled in turnby the operating system. Modern operating systems sharethe CPU with several running programs, doling out executiontime according to a scheduling algorithm that takesinto account the possible special priority of some programs(see multitasking).Further ReadingBrain, Marshall. “How Microprocessors Work.” Available online.URL: http://computer.howstuffworks.com/microprocessor.htm.Accessed June 30, 2007.CraigslistSome of the most successful Web services involve just oneor two basic changes in a traditional business or socialmodel. Online auctions, for example, came from the realizationthat the auctioneer and auction house could beeliminated and a platform provided by which people couldbuy from or sell to one another directly. (The platform, ofcourse, does have to include such things as listing policies,payment methods, and feedback systems.)Craigslist has done for the newspaper “personal” ad andlaundromat bulletin board what eBay has done for auctions.It was founded in 1995 by Craig Newmark, a San FranciscoBay Area software developer who saw a need for an onlineforum for news about local events. The “list” part of Craigslistreflects its origin as an e-mail list.News about the list spread rapidly in Newmark’s milieuof well-connected professionals, and the volume of postingsgrew correspondingly large. Furthermore, many peoplebegan to post things other than event listings—includingjob openings, for which Newmark soon set up a separatecategory on the list. As the number and kinds of postingsgrew, the mailing list format became unwieldy, so Newmarkand some volunteers put together a Web interface thatusers could use to browse the various categories. By 2000Craigslist.org had become a full-time job for Newmark andnine employeesCraiglist’s Web site is organized by community, includingU.S. states and cities and a variety of other countriesand international cities. Each local site is further dividedinto sections such as community activities (including peopleseeking or providing childcare or sharing rides), personalads (seeking relationships), housing (mostly rentals), jobs,services, items for sale, and a variety of discussion forums.As of 2007 Craigslist had 24 employees. The site is nearlycompletely free of charge, with revenue coming only frompaid job listings and apartment broker listings in selectedcities. The site’s popularity has been impressive, with morethan 5 billion page views, 10 million visitors, and over 10million classified ads per month.Newmark and CEO Jim Buckimaster have suggestedthat they have little interest in either turning Craigslistinto a public company or “going commercial” and tappingwhat many observers consider to be much greater revenuepotential.Problems and IssuesCraiglist’s success has raised some issues. In 2004 eBaybought a 25 percent stake in the company, leading somesupporters to worry about pressure to raise more revenueby carrying banner ads or charging for posting on the site.However, as of 2008 the site remains free to users.

Cray, Seymour 121As with eBay, Craigslist has to strike a balance betweenprotecting users from criminal activity and exercising directoversight with the attendant expenses and legal problems.For keeping out illegal ads (such as discriminatory housingor job offers or solicitations for prostitution), Craigslisthas relied mainly on users to be “good citizens” and to“flag” offending ads for removal by the service. Nevertheless,police have reported use of Craigslist by prostitutionrings and other organized criminals and identity thievesseeking personal information. A 2006 suit (subsequentlydismissed) accused Craigslist of “allowing” discriminatoryhousing ads in Chicago. (Under federal law, Web sites aregenerally not liable for content posted by users, unless thesite has edited content.)Because Craigslist has been so successful, newspapershave complained that it has dried up much of their revenuefrom classified advertising, costing them an estimated $50–$65 million in 2004 in the Bay Area alone. This is particularlya concern of small local and independent newspapersfor which ads may be their only source of revenue.Craigslist has won a 2001 Webby award for Best CommunitySite, and was voted Best Local Web site in a 2003Manhattan Reader’s Poll.Further ReadingCarney, Brian M. “Zen and the Art of Classified Advertising.” WallStreet Journal.com OpinionJournal, June 17, 2006. Availableonline. URL: http://www.opinionjournal.com/editorial/feature.html?id=110008531.Accessed September 9, 2007.Craigslist. Available online. URL: http://www.craigslist.org.Accessed September 9, 2007.“Craigslist Hits Bay Area Classifieds Hard.” NewsInc 16 (December27, 2004): n.p. Available online. URL: http://www.newsinc.net/morgue/2004/NI041227.html. Accessed September 9, 2007.Sentementes, Gus G. “Web Site Vice Stings.” Baltimoresun.com,September 8, 2007. Available online. URL: http://www.baltimoresun.com/news/local/annearundel/bal-md.ar.prostitution08sep08,0,179750 1.story. Accessed September 9,2007.Cray, Seymour(1925–1996)AmericanComputer Engineer, InventorSeymour Cray was a computer designer who pioneered thedevelopment of high-performance computers that cameto be called supercomputers. Cray was born in ChippewaFalls, Wisconsin. After serving in World War II as an armyelectrical technician, Cray went to the University of Minnesotaand earned a B.S. in electrical engineering and thenan M.S. in applied mathematics. (This combination is acommon background for many of the designers who wouldhave to combine mathematics and engineering principles tocreate the first computers.)In 1951, he joined Engineering Research Associates(ERA), one of a handful of companies that sought to commercializethe digital computing technology that had beendeveloped during and just after the war. Cray soon becameSeymour Cray is considered by many people to be the fatherof the supercomputer. His innovative Cray computers looked—and performed—like something out of science fiction. (CrayResearch)known for his ability to grasp every aspect of computingfrom logic circuits to the infant discipline of software development.When ERA and its competitor, the Eckert-MauchlyComputer Company were bought by Remington Rand, Craybecame the chief designer for the Univac, the first commerciallysuccessful computer. In 1957, however, Cray andtwo colleagues struck out on their own to form ControlData Corporation (CDC). Their CDC 1604 was one of thefirst computers to move from vacuum tubes to transistors.The CDC 6600 was considered by many to be technicallysuperior to the IBM 360. However, by then IBM had becomepreeminent in the business computing market, while theCDC machines found favor with scientists.By the late 1960s, Cray had persuaded CDC to providehim with production facilities within walking distance ofhis home in Chippewa Falls. There he designed the CDC7600. This computer was hailed as the world’s first supercomputer(see supercomputer). However CDC disagreed withCray about the commercial feasibility of even more powerfulcomputers. In 1972, Cray formed his own company, CrayResearch, Inc. By then Cray’s reputation as a computer architectwas so great that investors flocked to buy stock in hiscompany. His series of Cray supercomputers looked like sleekmonoliths from a science fiction movie. The machines werethe first supercomputers to use parallel processing, where

122 CRMtasks can be assigned to different processors to speed upthroughput. While costing millions of dollars apiece, theCray supercomputers made it possible to perform simulationsin atomic physics, aerodynamics, and other fieldsthat were far beyond the capabilities of earlier computers.However, the Cray Computer Corporation ran into financialproblems and was bought by Silicon Graphics (SGI) in 1996.Cray received many honors including the IEEE ComputerSociety Pioneer Award (1980) and the ACM/IEEEEckert-Mauchly Award (1989). Cray died on October 5,1996, in Colorado Springs, Colorado.Further ReadingBell, Gordon. “A Seymour Cray Perspective.” Available online. URL:http://_research.microsoft.com/users/gbell/craytalk/. AccessedJuly 1, 2007.Breckenridge, Charles W. “A Tribute to Seymour Cray.” Availableonline. URL: http://www.cgl.ucsf.edu/home/tef/cray/tribute.html. Accessed July 1, 2007.Murray, C. J. The Supermen: the Story of Seymour Cray and theTechnical Wizards behind the Supercomputer. New York: JohnWiley, 1997.Smithsonian Institute. National Museum of American History.“Seymour Cray Interview.” Available online. URL: http://americanhistory.si.edu/collections/comphist/cray.htm.CRM See customer relationship management.CSS See cascading style sheets.Cunningham, Howard (Ward)(1949– )AmericanSoftware DeveloperToday the first place many Web users look for informationabout a topic is Wikipedia, the vast and ever growingonline collaborative encyclopedia. The type of software thatmakes Wikipedia (and thousands of other wikis) possiblewas invented by Howard G. Cunningham, better known asWard Cunningham.Born on May 26, 1949, Cunningham learned to programin high school. He then attended Purdue University, wherehe received a bachelor’s degree in electrical engineering andcomputer science and then a master’s in computer science.After graduation Cunningham worked as a researcher inmicrocomputer systems for Tektronix, where he encounteredan intriguing style of programming (see Smalltalk).In a later position at Wyatt Software, Cunningham becameinvolved with larger-scale software projects and began tothink about better ways to manage them.In the early 1980s Cunningham encountered a book thatlooked at architecture in terms of the combining of intuitivepatterns. Cunningham began to apply similar principles tothe design of software (see also design patterns). One resultwas the holding of the first conference on pattern languagesat the University of Illinois at Urbana-Champaign in 1994.Around that time, Cunningham was seeking a way forprogrammers to collaborate in working with design patterns.He had already encountered the power of linking(see hypertext) in HyperCard, developed by Apple for theMacintosh in the late 1980s. Because it was so easy to use,HyperCard encouraged many nonprofessional programmers(including teachers) to develop and share applications.Developing the WikiUsing HyperCard, Cunningham built an application thatallowed users to add free-form data to a database and linkit to other entries by clicking a button. Users who tried itwere fascinated by its potential. Cunningham then wantedto expand it so users could access it over networks. However,he was unable to develop a networked version of hisHyperCard application.One colleague suggested using the World Wide Web (seeBerners-Lee, Tim and World Wide Web). Cunninghamimplemented his free-form linking system as Web pages,and the result was something he at first thought of callingQuickWeb. He then remembered hearing the phrase wikiwiki or “quickly, quickly”) in Hawaii, and he decided to callhis system wikiwikiWeb. Today, it is just known as a wiki(see wikis and Wikipedia). This first wiki, called the PortlandPattern Repository, came online in 1995 and continuesto operate today.Collaborative Software DevelopmentCunningham worked for a few years on open-source projectsat Microsoft. The giant software maker is not generallywell regarded among open-source developers, though Cunninghamhas acknowledged its technical prowess. At anyrate, Cunningham decided to move on. He served as directorfor community development at the Eclipse Foundation,which oversees development of Eclipse, a versatile and verypopular open-source programming environment. In 2007Cunningham left Eclipse to become chief technology officer(CTO) of AboutUs, a company founded to further developwikis and collaborative communities.Cunningham continues to be an enthusiastic proponentof open source. He argues that the most important advantageof open source is not lower cost, but the way it putsaccess to powerful tools into the hands of thousands ofusers and encourages them to develop new features andcapabilities.Cunningham’s contributions to programming methodsare also extensive, including the use of design patterns for“quick and agile” development and what became known as“extreme programming.”Further ReadingCunningham, Ward. Home Page. Available online. URL: http://www.c2.com/cgi/wiki?WardCunningham. Accessed September9, 2007.Leuf, Bo, and Ward Cunningham. The Wiki Way: Quick Collaborationon the Web. Upper Saddle River, N.J.: Addison-WesleyProfessional, 2001.Siddalingaiah, Madhu. “Ward Cunningham Interview: Eclipse,Collaboration and Software Trends.” Includes links to Cunningham’sEclipseCon 2006 presentation. SQL Summit.

cyberlaw 123Available online [audio]. URL: http://www.sqlsummit.com/People/WCunningham.htm. Accessed September 9, 2007.Taft, Darryl K. “Father of Wiki Speaks Out on Communityand Collaborative Development.” eWeek, March 20, 2006.Available online. URL: http://www.eweek.com/article2/0,1759,1939982,00.asp. Accessed September 9, 2007.Wiki Wiki Web. Available online. URL: http://c2.com/cgi-bin/wiki?WikiWikiWeb. Accessed September 9, 2007.customer relationship management (CRM)In recent years there has been increasing emphasis, particularlyin online business, on communicating with and“cultivating” customers as well as in systematically usinginformation about transactions and customer behavior (seealso e-commerce). Collectively, these activities (and thesoftware used to implement them) are often known as customerrelationship management (CRM).The basic data stream in CRM is a complete contacthistory for each customer, including not only purchases,but also product or customer support inquiries. The resultingdatabase is used to ensure that with each new contact(such as through a call center), the person responding hasaccess to all the information about previous contacts withthe customer. Thus, for example, in the course of answeringa query or solving a problem, the representative can reviewa list of which products the customer has purchased andsuggest additional products that might help deal with theproblem.Besides dealing with customer-initiated contacts, CRMdata can be very useful in designing marketing campaigns,advertising, promotions, and so on (see online advertising).The database can be analyzed to determine, forexample, the likelihood that a customer who buys a digitalcamera might also buy a particular printer or memory card(see data mining). Once this is known, a customer who isin the process of buying a camera might be offered a specialprice on a memory card during checkout. (For an exampleof extensive integration, mining, and use of CRM data, seeamazon.com.) For longer-term planning, “strategic CRM”can help a company decide on what types of products andmarkets to focus.In addition to a database with extensive analysis andreporting facilities, a CRM system requires software thatsales or support persons can use to access information inreal time and update it with the results of the current call.Organizations can buy turnkey products or design theirown CRM systems by selecting and integrating softwarecomponents. However implemented, effective CRM requiresthat everyone in contact with a customer keep the ongoingcultivation of that relationship in mind, and search for waysto deliver more value than the competition.Successful CRM also requires a balance between thedesire to get as much information as possible and allayingcustomers’ concerns. If the CRM software (or how it isused) slows down the resolution of support calls, ends upgenerating unwanted solicitations (particularly from thirdparties), or conveys a sense of disregard for privacy, it coulddamage customer relations and lead to loss of business andreputation.Further ReadingButtle, Francis. Customer Relationship Management: Concepts andTools. Burlington, Mass.: Elsevier Butterworth-Heinemann,2004.CRM Today. Available online. URL: http://www.crm2day.com/.Accessed September 9, 2007.Customer Relationship Management Association. Available online.URL: http://www.crmassociation.org/. Accessed September 9,2007.Kincaid, Judith W. Customer Relationship Management: Getting ItRight. Upper Saddle River, N.J.: Prentice-Hall/HP ProfessionalBooks, 2002.Kumar, V., and Werner J. Reinartz. Customer Relationship Management:A Databased Approach. New York: Wiley, 2005.Prahalad, C. K., et al. Harvard Business Review on Customer RelationshipManagement. Cambridge, Mass.: Harvard BusinessSchool, 2001.cyberlawLegal scholars and law schools have begun to use the termcyberlaw to refer to a variety of legal issues that are ofteninvolved in online interactions (see cyberspace). Whiletraditional legal fields such as contract law, property law,privacy, and jurisdiction do apply online, cyberlaw recognizesthat certain common features of the digital worldpose unique challenges.The first question in any legal dispute is which court, ifany, has jurisdiction. In the physical world there are welldemarcatedspheres (in the United States) for federal, state,and municipal law. However, participants in an onlinetransaction or other act may often be in different physicaljurisdictions. Indeed, the World Wide Web’s structuredoes not inherently follow physical boundaries, with linkagebeing largely semantic rather than geographical. SomeInternet advocates such as John Perry Barlow have gone sofar as to argue that the Web must develop its own laws andcustoms that reflect its technical and social nature—eventuallyforming its own social contract.A more pragmatic approach is taken by Lawrence Lessig,who argues that a legal regime must evolve that takesinto account the needs and concerns of both traditionalphysical jurisdictions and the new realm of cyberspace (seeLessig, Lawrence).Diverse IssuesIn practice, when crimes or disputes occur online, politicalpressure or legal duty will impel federal and state officialsto become involved. For example, users of file-sharing servicesare being sued for alleged violations of copyright law(see file-sharing and P2P networks and intellectualproperty and computing). The question of whether theprovider of an online service should be held responsiblefor violations by users must also be decided; in the UnitedStates, federal law has exempted providers from most legalliabilities. Matters can become even more complicatedwhen people involved in a case are living in different countries.(Many countries have lax or no regulation of onlineactivity, and activity prohibited in countries such as theUnited States can flourish there—see, for example, onlinegambling.)

124 cyberneticsMany issues regarding freedom of speech and expressionarise in the online world. Should a blogger be accordedthe rights of a traditional journalist? Should an Americancompany such as Google or Yahoo! be held responsible forturning dissidents over to Chinese authorities?The growth of immersive and persistent online gameworlds such as Second Life raises other difficult questions forcyberlaw (see identity in the online world and onlinegames). Can promises (whether business contracts or evenmarriage proposals) made through online personas (“avatars”)be binding? Who owns property (such as a house)created or purchased in the virtual world? What if someonesteals or vandalizes the virtual property? Should a virtualworld be treated as a kind of parallel jurisdiction andperhaps allowed to have its own legal system and courts,perhaps even a form of limited sovereignty? While thesequestions may seem far-fetched, they take on more urgencyas millions of people begin to spend a significant part oftheir waking time in a virtual world and generate economicactivity that can be denominated in real money. The resolutionof these and other cyberlaw issues will both depend onand influence how the Internet itself is organized and governed(see Internet organization and governance).For some organizations currently involved in trying to promotecyber rights and shape policy, see cyberspace advocacygroups.Further ReadingBarlow, John Perry. “A Declaration of the Independence of Cyberspace.”Available online. URL: http://homes.eff.org/~barlow/Declaration-Final.html. Accessed September 9, 2007.Electronic Frontier Foundation. “Internet Law Treatise.” Availableonline. URL: http://ilt.eff.org/index.php/Table_of_Contents.Accessed April 23, 2008.Gahtan, Alan. Cyberlaw Encyclopedia. Available online. URL:http://www.gahtan.com/cyberlaw/. Accessed September 9,2007.Ku, Raymond S., and Jacqueline D. Lipton. Cyberspace Law: Casesand Materials. 2nd ed. New York: Aspen Publishers, 2006.Lessig, Lawrence. Code: Version 2.0. New York: Basic Books, 2006.Zittrain, Jonathan L. Jurisdiction (Internet Law Series). New York:Foundation Press, 2005.cyberneticsCybernetics may not be familiar to many readers today,except as part of words like “cyberspace.” The term wascoined by mathematician Norbert Wiener (see Wiener,Norbert) in his book about control and communicationin animals and machines. The root comes from the Greekkybernetes, meaning steersman or governor.Cybernetics looks at systems as a whole. A key conceptis feedback, which allows a system to adjust itself inresponse to changes in the environment. A familiar exampleis a thermostat, which includes a switch that expands asthe air heats, turning off the heater when the temperaturereaches its indicated setting. Similarly, as the air cools theswitch contracts and restarts the heater.In addition to feedback, cybernetics looks at how informationis communicated between the environment and amachine or organism, or between component parts. Cyberneticsis also interested in structures that may be builtup through feedback and communication—ultimately, inhumans: the structures of self, identity, and consciousness.Cybernetics is fundamental to the operation of robots(see robotics). Around the time of Wiener’s book, GreyWalter built one of the earliest robots, a “cybernetic turtle”that could autonomously explore an environment, respondingto changes in light.In computers, any program that changes its behavior inresponse to new data might be called cybernetic. Cyberneticsis relevant to a variety of fields in computer science thatinvolve machine learning or reasoning (see artificial intelligence,genetic programming, and neural network).During the 1950s and 1960s cybernetics conceptsbecame quite influential and were applied to such diversefields as neurology, cognitive science, psychology, philosophy,anthropology, sociology, and economics. However,the term cybernetics itself gradually fell out of favor,even though the concepts remain at the heart of systemsthinking. For some writers such as Gregory Bateson andanthropologist Margaret Mead, the focus shifted to a “newcybernetics” or “second-order cybernetics” that studies theinteraction of observers with phenomena and attempts toconstruct a model of the mind itself.Further ReadingAmerican Society for Cybernetics. Available online. URL: http://www.asc-cybernetics.org/. Accessed September 10, 2007.Gasperi, Michael. “Grey Walter’s Machina Speculatrix.” Availableonline. URL: http://www.extremenxt.com/walter.htm.Accessed September 10, 2007.Principia Cybernetica Web. Available online. URL: http://pespmc1.vub.ac.be/. Accessed September 10, 2007.Wiener, Norbert. Cybernetics: or Control and Communication inthe Animal and the Machine. 2nd ed. Cambridge, Mass.: MITPress, 1961.cyberspace advocacy groupsBy the mid-1990s a number of issues were arising as theInternet and Web became an increasingly important factorin commerce and society (see censorship and theInternet, intellectual property and computing, andprivacy in the digital age). Often in response to proposedor enacted federal legislation, a number of advocateshave organized groups to keep track of developments thatthey believe threaten the free exchange of information andexpression, as well as opposing government surveillanceand corporate practices believed to intrude on privacy.Although there are dozens of groups advocating for therights of Internet users, three groups have been particularlyprominent and effective.Electronic Frontier FoundationThe Electronic Frontier Foundation (EFF) was founded in1990 by Mitch Kapor, John Gilmore, and John Perry Barlow.Its immediate motivation was the federal search andseizure of computers belonging to Steve Jackson Gamesas part of an investigation into illegal distribution of proprietarydocuments. Although the game company was not

cyberspace and cyber culture 125involved in any crime, the seizure of its equipment andinformation threatened to put it out of business. Ultimately,Jackson prevailed in federal court, establishing that unconventionalmeans of expression such as games were entitledto First Amendment protection. In another high-profilecase, computer scientist Daniel Bernstein sued and wonthe right to publish encryption software and related papers,again extending First Amendment protections in the digitalworld.The EFF has also been involved in the dispute betweenusers of file-sharing services and the Recording IndustryInstitute of America (RIAA) over subpoenas of service providersseeking alleged illegal downloaders.Most recently, the EFF has expanded its efforts furtherwith regard to issues of government surveillance and theprosecution of computer crimes, such as collection and useof evidence.Center for Democracy and TechnologyFounded in 1994, the Center for Democracy and Technology(CDT) somewhat overlaps the EFF in interests, buthas a greater emphasis on the connections between onlineactivities and the political process. The organization’s firstmajor battle involved the Computer Decency Act. Whileintended by its proponents to ban obscenity and particularlychild pornography from the Internet, cyberspacerightsadvocates saw the law as vague, poorly written, andlikely to deny access to material that is constitutionallyprotected for adults—an argument that the Supreme Courtultimately accepted in ACLU v. Reno (1997).More recently, the CDT has supported the free-speechrights of bloggers (see blogs and blogging), arguingthat they should be accorded journalistic rights (see alsojournalism and computers). Besides issue advocacy, theorganization’s overall focus is on developing public policythat recognizes the unique features of cyberspace and promotesfreedom of expression, protection of privacy, andwidespread access to the Net (see also Internet accesspolicy).Electronic Privacy Information CenterAlso founded in 1994, the Electronic Privacy InformationCenter (EPIC) is a Washington, D.C.–based public interestresearch center devoted to privacy and civil libertiesissues. The group’s electronic newsletter EPIC Alert providesa useful summary of ongoing developments, cases,and issues. The organization also publishes regularlyupdated compendiums on developments in open government/freedomof information, privacy and human rights,and privacy law.(For online activists involved in general political issuesand campaigns, see political activism and the Internet.)Further ReadingCenter for Democracy and Technology. Available online. URL:http://www.cdt.org/. Accessed September 10, 2007.Center for Democracy and Technology. “CDT: A Decade of InternetAdvocacy.” Available online. URL: http://www.cdt.org/mission/2006aao.pdf. Accessed September 10, 2007.Electronic Frontier Foundation. Available online. URL: http://www.eff.org/. Accessed September 10, 2007.Electronic Privacy Information Center. Available online. URL:http://www.epic.org/. Accessed September 10, 2007.Godwin, Mike. Cyber Rights: Defending Free Speech in the DigitalAge. Revised ed. Cambridge, Mass.: MIT Press, 2003.Privacy.org. Available online. URL: http://www.privacy.org/.Accessed September 10, 2007.cyberspace and cyber cultureThe term cyberspace first came to prominence whenit appeared in Neuromancer, a 1984 novel by science fictionwriter William Gibson. The word is a combinationof “cyber” (meaning related to computers) and “space.”As another SF writer, Bruce Sterling, wrote in The HackerCrackdown (1993), cyberspace is “the place between thephones. The indefinite place out there, where the two of you,human beings, actually meet and communicate.”While the elite telegraphers of the 19th century andlater telephone users first experienced the sense of disembodiedelectronic communication, it took the developmentof widespread computer terminals, personal computers,and connecting networks to create a sense of an ongoingplace in which people meet and interact. The first “villages”in cyberspace came into being during the 1970s asresearch networks (ARPA), and the Usenet newsgroupsof UNIX users began to carry messages and news postings.During the 1980s, many more settlements began tolight up the map of cyberspace, ranging from cities (largeonline services such as The Source, BIX, and CompuServe)to thousands of villages (tiny bulletin board systems runningon personal computers). (See online services andbulletin board systems.)Wherever human beings build communities, they shapeculture. The cyber culture that grew up in cyberspace hasfeatured many diverse strands. Hackers (not originally apejorative term) had their distinctive hangouts and lingo.Bulletin board cultures varied from the hacker hardcore touser groups that tried to assist beginners. On the nascentInternet multiplayer game worlds called MUDs (Multi-UserDungeons) and Muses used words to create richly detailedfantasy cyberspaces. Together with chat rooms and conferencingsystems, they fostered virtual communities that,like physical communities, express a full range of humanbehavior (see blogs and blogging, conferencing systems,chat, social networking, texting and instantmessaging, and virtual community).While cyber culture shares the characteristics of otherhuman cultures, it also has unique characteristics that aredictated by the nature of the online, virtual medium. Sincethe online user reveals only what he or she chooses toreveal, identities can be fluid: playful or deceptive. Whilepeople are not physically vulnerable in cyberspace, theyare certainly emotionally vulnerable. (Virtual eroticism, or“cyber sex” has even led to virtual rapes.) The issue of protectingprivacy becomes important because sensitive personalinformation is constantly being exposed in order tocarry on commerce (see identity in the online worldand privacy in the digital age.)

126 cyberstalking and harassmentThe Future of CyberspaceBy the end of the 1990s, the face of cyberspace was nolonger that of text screens but that of the World Wide Webwith its graphical pages. Multiplayer games now often featuregraphics and even real-time voice communication ispossible. With ubiquitous digital cameras, the boundarybetween cyberspace and physical space has become fluid,with people able to enter into each other’s physical environmentsin realistic ways. Meanwhile, the developmentof virtual reality techniques has made computer-generatedworlds much more vivid and realistic (see virtual reality).As more people are linked continually to the networkby broadband and wireless connections, cyberspace mayeventually disappear as a separate reality, having mergedwith physical space.Further ReadingBell, David. An Introduction to Cybercultures. New York: Routledge,2001.Bell, David, and Barbara M. Kennedy, eds. The CyberculturesReader. New York: Routledge, 2007.Jenkins, Henry. Convergence Culture: Where Old and New MediaCollide. New York: New York University Press, 2006.Resource Center for Cyberculture Studies. Available online. URL:http://rccs.usfca.edu/default.asp. Accessed July 1, 2007.Silver, David, and Adrienne Massari, eds. Critical CybercultureStudies. New York: New York University Press, 2006.Wired magazine. Available online. URL: http://www.wired.com.Accessed July 1, 2007.cyberstalking and harassmentCyberstalking and harassment or “cyber bullying” involvethe use of online communications and facilities (such asinstant messaging, chat rooms, e-mail, or Web sites) tostalk, harass, or otherwise abuse a person or group. Theseactivities may be carried on entirely online or in connectionwith physical stalking or harassment.Stalking and threatening a person has been a crime inthe physical world for some time, and similar principlesapply to online stalking. Generally, to be guilty of stalking, aperson must repeatedly harass or threaten the victim, oftenfollowing him or her and intruding or violating privacy.Cyberstalkers take advantage of the fact that there isa great deal of information about many people online.(Indeed, the popularity of sites such as MySpace meansthat many users can unwittingly provide that informationin well-organized, easy-to-access form—see social networking.)The stalker can also use search engines to finde-mail or even physical addresses and phone numbers, orcan join chat rooms used by the prospective victim,Motives for stalking can range from sexual obsession toanger at some real or imagined slight, to more idiosyncraticreasons. As with physical stalking in an earlier generation,law enforcement agencies were often slow to acknowledgethe potential seriousness of the crime or to develop effectiveways to deal with it.This began to change with the tragic and highly publicizedcase of Amy Boyer, who had been found onlinethrough a data broker, stalked, harassed, and ultimatelymurdered. In 1999 California became the first state to passa law against cyberstalking, and in 2000 cyberstalking wasmade part of the federal Violence against Women Act.CyberbullyingLike traditional bullying in schools or other settings, cyberbullyinginvolves harassment, sometimes organized, ofpeople considered to be weak or different in some way.However, the ability to hide or disguise one’s identity online(see anonymity and the Internet) facilitates cyberbullyingby making it harder for victims to identify and confrontor report their tormentors. Media for cyberbullying includetext and instant messaging, photos or videos, blogs, andincreasingly, pages on social networking sites. Contents caninclude threats, racial or other slurs, and unwelcome sexualsolicitations.In March 2007 a number of organizations joined withthe U.S. Department of Justice in a public service advertisingcampaign to educate young people about cyberbullyingand what they can do to prevent it. Some schools are adoptinganti-cyberbullying policies and programs.Besides potentially serious psychological trauma to victims,cyberbullying can sometimes lead victims to lash out,and in extreme cases, cyberbullying may play a role in campusshootings.Further ReadingBocij, Paul. Cyberstalking: Harassment in the Internet Age and Howto Protect Your Family. Westport, Conn.: Praeger, 2004.Bolton, Jose, and Stan Graeve, eds. No Room for Bullies: From theClassroom to Cyberspace: Teaching Respect, Stopping Abuse,and Rewarding Kindness. Boys Town, Nebr.: Boys Town Press,2005.“Cyberbullying: Identifying the Causes and Consequences ofOnline Harassment” [news and resources]. Available online.URL: http://www.cyberbullying.us/. Accessed September 10,2007.Cyberbullying.org. Available online. URL: http://www.cyberbullying.org/. Accessed September 10, 2007.Henderson, Harry. Internet Predators (Library in a Book). NewYork: Facts On File, 2005.Widhalm, Shelley. “New Teen Bullies.” Washington Times, September10, 2007. Available online. URL: http://washingtontimes.com/article/20070910/METRO/109100038/1004. Accessed September10, 2007.Willard, Nancy E. Cyberbullying and Cyberthreats: Responding tothe Challenge of Online Social Aggression, Threats, and Distress.Champaign, Ill.: Research Press, 2007.cyberterrorismCyberterrorism can include several types of activities:the promotion of terrorist or militant groups on the Web(including propaganda and recruitment), the coordinationor facilitation of terrorist activities, and actual attacks onWeb sites or other information infrastructure.Terrorists on the WebThere is little doubt that terrorist groups are increasinglycomputer savvy and willing to use the technology to furthertheir purposes. Many groups have Web sites that are

cyberterrorism 127used for propaganda and recruiting. (In 2007 a British courtsentenced three men, calling them “cyber-jihadis” and sayingthey had used a Web site to urge Muslims to attack non-Muslims.) In fact extremist groups of many kinds (includingneo-Nazis and other racial extremists) have long used Websites to attract young followers through propaganda, music,and even games.Other material posted by terrorist groups onlineincludes bomb-making plans, lists of potential targets (possiblyincluding maps or blueprints), and “tips” for penetratingdefenses or evading detection. (A project called DarkWeb at the University of Arizona searches for, compiles,and analyzes massive amounts of Web content generated byterrorist groups.)Attacks on Web SitesAttempts to jam or disrupt Web sites (such as denial ofservice attacks or DOS) have been made for a variety of reasons.At one end of the spectrum are individuals or smallgroups engaged in criminal activity (such as attemptedextortion) or expressing political protest (“hacktivists”). Atthe other end are alleged online offensives by national governments(see Information warfare).Although there have been no major disruptions as ofmid-2008, terrorists (or sympathizers) have already conductedcyberattacks. One site has even offered a downloadable“electronic jihad” program that users can use to selectfrom a list of targets to launch an automated DOS. Whilesuch sites are usually taken down after a few months, it isrelatively easy to start another, especially because informationprovided for site registration is often not verified.Fighting CyberterrorismStrategies and tactics to combat cyberterrorism involve bothgeneral antiterrorist intelligence and other techniques aswell as those particularly adapted to the cyberspace arena(see counterterrorism and computers, computercrime and security, and computer forensics).The cyberterrorist threat also plays an important rolein the effort to better protect vital infrastructure. Althoughattacks on banking and other financial computer systemshave the potential to cause severe economic damage, muchattention has focused on computer-based attacks that havethe potential to directly injure or even kill people. Back in2000, an individual hacker in Australia took over a pumpingstation and dumped more than 264,000 gallons of raw sewageinto public lands and waterways. Although no humanswere directly harmed, it is easy to see that such contaminationin the drinking water supply could be deadly.Regardless of the type of computer system, followingbest security practices can go a long way to “hardening”potential targets. Such practices include the use of robustfirewalls and antivirus programs, regular security updatesfor the operating system and software, network monitoringand intrusion detection, sharing information about securitythreats, and training personnel to be aware of typicalattacker techniques, including deception (social engineering).There needs to be a comprehensive protection plan foreach facility that takes both physical and electronic securityinto accountAssessmentIn recent years cyberterrorism has been a much publicizedtopic. Some critics believe that the threat of cyberterrorismhas been overestimated—not because many computer systemsare not vulnerable, but because the most vulnerablephysical systems are generally not on the Internet and noteasily accessible. It has also been argued that terrorists generallyuse simpler, more direct weapons (e.g., bombs) andaim to produce physically spectacular or terrifying results.Most cyberattacks would not seem to meet those criteria.On the other hand, a cyberattack might be launched inconjunction with physical attacks, either as a distractionor to make it harder for authorities to respond to the mainattack.Properly assessing risks and allocating resources willalways be difficult, and will always be influenced by politicaland economic as well as technological factors.Further ReadingBlane, John V., ed. Cybercrime and Cyberterrorism: Current Issues.New York: Novinka Books, 2003.Brown, Lawrence V., ed. Cyberterrorism and Computer Attacks.New York: Novinka Books, 2006.Chen, Hsinchun. “How Terrorists Use the Internet” [interviewtranscript]. The Science Show, March 31, 2007. Availableonline. URL: http://www.abc.net.au/rn/scienceshow/stories/2007/1885902.htm#transcript. Accessed September 7, 2007.Colarik, Andrew M. Cyber Terrorism: Political and Economic Implications.Hershey, Penn.: Idea Group, 2006.“Cyber-Terrorism: Propaganda or Probability?” About.com. Availableonline. URL: http://antivirus.about.com/library/weekly/aa090502a.htm. Accessed September 7, 2007.Greenmeier, Larry. “Cyberterrorism: By Whatever Name, It’s onthe Increase.” InformationWeek, July 7, 2007. Available online.URL: http://www.informationweek.com/story/showArticle.jhtml?articleID=200900812. Accessed July 12, 2007.O’Day, Alan, ed. Cyberterrorism. Burlington, Vt.: Ashgate, 2004.Wagner, Breanne. “Electronic Jihad: Experts Downplay ImminentThreat of Cyberterrorism. National Defense 92 (July 1, 2007):p. 34 ff.

DdataToday the term data is associated in many peoples’ mindsmainly with computers. However, data (as in “given facts”or measurements) has been used as a term by scientists andscholars for centuries. Just as with a counting bead, a notchin a stick, or a handwritten tally, data as stored in a computer(or on digital media) is a representation of facts aboutthe world. These facts might be temperature readings, customeraddresses, dots in an image, the characteristics ofa sound at a given instant, or any number of other things.But because computer data is not a fact but a representationof facts, its accuracy and usefulness depends not only onthe accuracy of the original data, but on its context in thecomputer.At bottom, computer data consists of binary states (representednumerically as ones or zeroes) stored using somephysical characteristic such as an electrical or magneticcharge or a spot capable of absorbing or reflecting light.A string of ones and zeroes in a computer has no inherentmeaning. Is the bit pattern 01000001 a number equivalentto 65 in the decimal system? Yes. Is it the capital letter “A”?It may be, if interpreted as an ASCII character code. Is itpart of some larger number? Again, it may be, if the memorylocation containing this pattern is interpreted as part ofa set of two, four, or more memory locations.In order to be interpreted, data must be assigned a categorysuch as integer, floating point (decimal), or character(see data types). The programming language compiler usesthe data type to determine how many memory locationsmake up that data item, and which bits in memory correspondto which bits in the actual number. Data items can betreated as a batch (see array) for convenience, or differentkinds of data such as names, addresses, and Social Securitynumbers can be grouped together into records or structuresthat correspond to an entity of interest (such as a customer).In creating a structure within the program to represent thedata, the programmer must be cognizant of its purpose andintended use.The programming language and code statements definethe context of data within the rules of the language. However,the meaning of data must ultimately be constructedby the human beings who use it. For example, whether atest score is good, bad, or indifferent is not a characteristicof the data itself, but is determined by the purposes ofthe test designer. This is why a distinction is often madebetween data, as raw numbers or characters, and informationas data that has been placed in a meaningful contextso that it can be useful and perhaps even enlightening tothe user.Further ReadingBierman, Alan W. Great Ideas in Computer Science: a Gentle Introduction.2nd ed. Cambridge, Mass.: MIT Press, 1997.Hillis, Daniel W. The Pattern on the Stone: the Simple Ideas thatMake Computers Work. New York: Basic Books, 1998.data abstractionAbstract data types are used to describe a “generic” type ofdata, specifying how the data is stored and what operationscan be performed on it (see object-oriented programming,list processing, stack, and queue).128

data acquisition 129For example, an abstract stack data type includes astructure for storing data (such as a list or array) and aset of operations, such as “pushing” an integer onto thestack and “popping” (removing) an integer from the stack.(For the process of combining data and operations into asingle entity, see encapsulation.) Abstract data types canbe implemented directly in object-oriented programminglanguages (see class, c++, Java, and Smalltalk).One advantage of using abstract data types is that itseparates a structure and functionality from its implementation.In designing the abstract stack type, for example,one can focus on what a stack does and its essential functions.One avoids becoming immediately bogged downwith details, such as what sorts of data items can be placedon the stack, or exactly what mechanism will be used tokeep track of the number of items currently stored. Thisapproach also avoids “featuritis,” the tendency to see howmany possible functions or features one can add to thestack object. For example, while it might be useful to give astack the ability to print out a list of its items, it is probablybetter to wait until one needs such a capability than to burdenthe basic stack idea with extra baggage that may makeit more cumbersome or less efficient.An abstract data type or its embodiment, a class, is notused directly by the program. Rather, it is used to create anentity (object) that is a particular instance of the abstractdata type (for example, an actual stack that will be usedto manipulate data). The data stored inside the object isnot accessed directly, but through functions that the objectreceives from the abstract data type (such as the push andpop operations for a stack). (For more information abouthow such objects are used, see class.)Because the abstract data type is not directly used bythe program, the implementation of how the data is storedor manipulated can be changed without affecting programsthat use objects of that type. This information hiding isone of the chief benefits of object-oriented programming.Another advantage is inheritance, the ability to derive morespecialized versions of the abstract data type or class. Thus,one can create a derived stack class that includes the printingfunction mentioned earlier.the ASCII character code for the key pressed. Moving themouse sends a stream of signals that are proportional to therotation of the ball which in turn is calibrated into a seriesof coordinates and ultimately to a position on the screenwhere the cursor is to be moved. Digital cameras and scannersconvert the varying light levels of what they “see” intoa digital image.Besides the devices that are familiar to most computerusers, there are many specialized data acquisition devices(DAQs). Indeed, most instruments used in science andengineering to measure physical characteristics are nowdesigned to convert their readings into digital form. (Sometimesthe instrument includes a processor that provides arepresentation of the data, such as a waveform or graph. Inother cases, the data is sent to a computer for processingand display.)Components of a Data Acquisition SystemThe data acquisition system begins with a transducer,which is a device that converts a physical phenomenon(such as heat) into a proportional electrical signal. Transducersinclude devices such as thermistors, thermocouples,and pressure or strain gauges. The output of the transduceris then fed into a signal conditioning circuit. The purposeof signal conditioning is to make sure the signal fits intothe range needed by the data processing device. Thus theFurther ReadingCarrano, Frank M. Data Abstraction and Problem Solving with C++:Walls and Mirrors. 4th ed. Reading, Mass.: Addison-Wesley,2004.“Introduction to Data Abstraction.” MIT Press. Available online.URL: http://mitpress.mit.edu/sicp/full-text/sicp/book/node27.html. Accessed July 3, 2007.Koffman, Elliot B., and Paul A. T. Wolfgang. Objects, Abstraction,Data Structures and Design Using Java Version 5.0. New York:Wiley, 2004.data acquisitionThere are a variety of ways in which data (facts or measurementsabout the world) can be turned into a digitalrepresentation suitable for manipulation by a computer. Forexample, pressing a key on the keyboard sends a signal thatis stored in a memory buffer using a value that representsData acquisition is the process of gathering real-time data fromscientific instruments and making it available in digital form. Sensorsignals are “conditioned” by filtering extraneous values, andare then sampled and digitized. Software can now provide elaborategraphic displays as well as alert scientists to unusual readings.

130 database administrationsignal may be amplified or its voltage may be adjusted orscaled to the required level. Another function of signal conditioningis to isolate the incoming signal from the computerto which the acquisition device is connected. Thisis necessary both to protect the delicate computer circuitsfrom possible “spikes” in the incoming signal and to prevent“noise” (extraneous electromagnetic signals created bythe computer itself) from distorting the signal, and thusthe ultimate measurements. Various sorts of filters can beadded for this purpose.The conditioned signal is fed as an analog input into thedata acquisition device, which is often a board inserted intoa personal computer. The purpose of the board is to samplethe signal and turn it into a stream of digital data. Thedigital data is stored in a buffer (either on the board or in thecomputer’s main memory). Software then takes over, analyzingthe data and creating appropriate displays (such as digitalreadings, graphs, or warning signals) as configured bythe user. If the data is being displayed in real time, the speedof the software, the operating system, and the computer’sclock speed may become significant (see clock speed).Performance ConsiderationsThe sampling rate, or the number of times the signal is measuredper second, is of fundamental importance. A highersampling rate usually means a more accurate representationof the physical data (thus audio sampled at higher ratessounds more “natural”). The faster the sampling rate, thelarger the amount of data to be processed and the greaterthe amount of computer resources needed. Thus, picking asampling rate usually involves a tradeoff between accuracyand speed (for a real-time application, data must be processedfast enough so that whoever is using it can respondto it as it comes in).Three internal factors determine the performance ofa DAQ. The resolution is the number of bits available toquantify each measurement. Clearly the ability to measurethousands of voltage levels is useless if the resolution of asystem is only 8 bits (256 possible values.) The range is thedistance between the minimum and maximum voltage levelsthe DAQ can recognize. If a signal must be “squeezed”into too narrow a range, a corresponding amount of resolutionwill be lost. Finally, there is the gain or the ratiobetween changes in the measured quantity and changes inthe signal strength.ApplicationsData acquisition systems are essential to gathering and processingthe detailed data required by scientific and engineeringapplications. The automated control of chemicalor biochemical processes requires the ability of the controlsoftware to assess real-time physical data in order to maketimely adjustments to such factors as temperature, pressure,and the presence of catalysts, inhibitors, or other componentsof the process. The highly automated systems used inmodern aviation and increasingly, even in ground vehicles,depend on real-time data acquisition. It is not surprising,then, that data acquisition is one of the fastest-growingfields in computing.Further ReadingBeyon, Jeffrey Y. LabVIEW Programming, Data Acquisition andAnalysis. Upper Saddle River, N.J.: Prentice Hall, 2000.“Data Acquisition (DAQ) Fundamentals.” Available online. URL:http://zone.ni.com/devzone/cda/tut/p/id/3216. Accessed June8, 2007.James, Kevin. PC Interfacing and Data Acquisition: Techniques forMeasurement, Instrumentation and Control. Boston: Newnes,2000.database administrationDatabase administration is the management of databasesystems (see database management system). Databaseadministration can be divided into four broad areas: datasecurity, data integrity, data accessibility, and systemdevelopment.Data SecurityWith regard to databases, ensuring data security includesthe assignment and control of users’ level of access to sensitivedata and the use of monitoring tools to detect compromise,diversion, or unauthorized changes to database files(see data security). When data is proprietary, licensingagreements with both database vendors and content providersmay also need to be enforced.Data IntegrityData integrity is related to data security, since the completenessand accuracy of data that has been compromisedcan no longer be guaranteed. However, data integrity alsorequires the development and testing of procedures for theentry and verification of data (input) as well as verifyingthe accuracy of reports (output). Database administratorsmay do some programming, but generally work with theprogramming staff in maintaining data integrity. Since mostdata in computers ultimately comes from human beings,the training of operators is also important.Within the database structure itself, the links betweendata fields must be maintained (referential integrity) anda locking system must be employed to ensure that a newupdate is not processed while a pending one is incomplete(see transaction processing).Internal procedures and external regulations mayrequire that a database be periodically audited for accuracy.While this may be the province of a specially trained informationprocessing auditor, it is often added to the dutiesof the database administrator. (See also auditing in dataprocessing.)Data AccessibilityAccessibility has two aspects. First, the system must be reliable.Data must be available whenever needed by the organization,and in many applications such as e-commerce,this means 24 hours a day, 7 days a week (24/7). Reliabilityrequires making the system as robust as possible, such asby “mirroring” the database on multiple servers (which inturn requires making sure updates are stored concurrently).Failure must also be planned for, which means the imple-

database management system 131mentation of onsite and offsite backups and procedures forrestoring data (see backup and archive systems).System DevelopmentAn enterprise database is not a static entity. The demand fornew views or applications of data requires the developmentand testing of new queries and reports. While this is normallydone by the database programmers, the administratormay need to consider its impact on the operation of thesystem. The administrator also helps plan for the needs of agrowing, changing, organization by designing or evaluatingproposals for expanding the system, possibly moving it tonew hardware or a new operating system or migrating thedatabase applications to a new database management system(DBMS).Because of the importance of database management tocorporations, government, and other organizations, databaseadministration became a “hot” employment area inthe 1990s. Most database administrators specialize in aparticular database platform, such as Oracle or MicrosoftAccess. The growing need to make databases accessible viathe Internet has added a new range of challenges to thedatabase administrator, including the management of servers,remote authentication of users, and the mastery of Java,Common Gateway Interface (CGI), and scripting languagesin order to tie the database to the server and user (see Java,cgi, Perl, and xml).Further ReadingAbout.com. Database Administration [links]. Available online. URL:http://databases.about.com/od/administration/Database_Administration.htm. Accessed July 8, 2007.Alapati, Sam R. Expert Oracle Database 10g Administration. Berkeley,Calif.: Apress, 2005.Mannino, Michael A. Database Design, Application Development,and Administration. 3rd ed. New York: McGraw-Hill, 2005.Mullins, Craig S. Database Administration: The Complete Guide toPractices and Procedures. Reading, Mass: Addison-Wesley Professional,2002.MySQL AB. MySQL Administrator’s Guide and Language Reference.Indianapolis: MySQL Press, 2005.Wood, Dan, Chris Leiter, and Paul Turley. Beginning SQL Server2005 Administration. Indianapolis: Wrox, 2006.database management system (DBMS)A database management system consists of a database (acollection of information, usually organized into recordswith component fields) and facilities for adding, updating,retrieving, manipulating, and reporting on data.Database StructureIn the early days of computing, a database generally consistedof a single file that was divided into data blocks thatin turn consisted of records and fields within records. TheCOBOL language was (and is) particularly suited to reading,processing, and writing data in such files. This flatfile database model is still used for many simple applicationsincluding “home data managers.” However, for morecomplex applications where there are many files containinginterrelated data, the flat file model proves inadequate.Because both the Customer Record and the Transaction Recordinclude the Customer Number field, it is easy to pull informationfrom both databases into a single report, such as a summary of purchasesfor each customer.In 1970, computer scientist E. F. Codd proposed a relationalmodel for data organization. In the relational model,data is not viewed as files containing records, but as a setof tables, where the columns represent fields and the rowsindividual entities (such as customers or transactions).A field (column) that two tables have in common (calledthe key) can be used to link the two. For example, considera table of customer information (name, customer number,address, current balance, and so on) and a table of transactioninformation (product number, quantity, customernumber of purchaser, and so on).To find all the items purchased by a particular customer,the relational database uses the common field (the customeraccount number) to join the two tables. A query can thenselect all records in the transaction file whose customernumber field matches the current customer in the customerfile. (Notice that the validity of a key field depends on itsbeing unique: If each customer doesn’t have one [and onlyone] customer number, any report of purchases will not bedependable.)A procedure called normalization is often used to createa set of tables from a set of data files and records, such thatno fields contain duplicate information. This is necessary inorder to ensure that a piece of information can be updatedand the update “propagated” to the entire database withoutmissing any instances.Relational databases usually also enforce referential integrity.This means preventing changes to the database fromcausing inconsistencies. For example, if table A and table Bare linked and a record is deleted from table A, any links tothat record from records in table B must be removed. Similarly,if a change is made in a linked field in a table, recordsin a linked table must be updated to reflect the change.During the 1980s, the dBase relational database programbecame the most popular DBMS on personal computers.Microsoft Access is now popular on Windows systems,

132 database management systemMicrosoft Access is a popular relational database program for personal computers. It can be used for both simple (“flat file”) databases andfor complex databases with many interrelated files.and Oracle is prominent in the UNIX world. Beginningin the 1980s, SQL (Structured Query Language) became awidely used standard for querying and manipulating datatables, and most DBMS implement SQL (see sql).TrendsThe embracing of object-oriented programming principlesstarting in the 1980s has led to development of object-orienteddatabase structures (see object-oriented programming).In this approach tables, queries, views, and othercomponents of the DBMS are treated as objects that presenttheir functionality through interfaces (much in the way aclass in an object-oriented program does). This approachcan improve data integrity, flexibility (such as through theability to define new operations), and the development ofnew capabilities derived from predecessor objects. Objectmodels are also helpful in dealing with a networked worldin which data tables are often stored on separate computers.As important as changes in the architecture of databaseshave been, the impact of a changing environment has probablybeen even more significant. In particular, Web sites ofall kinds are increasingly being driven by databases (such asfor inventory and order processing for e-commerce). In turn,many databases of all sizes and types are now accessible andsearchable via the Web. This has meant a new emphasis onrapid development of database programs, particularly usingscripting languages, as well as fast and efficient Web-baseddatabase processing (see also Ajax). While the traditionalhigh-end corporate database systems such as Oracle andSQL Server are still vital for the enterprise, open-sourcealternatives (particularly MySQL) are in widespread use formany applications including wikis and content-managementsystems. The use of flexibly structured data (see xml andsemantic Web) to link and transform databases has alsoexpanded database concepts in the Web-centric world.Further ReadingAllen, Christopher, Catherine Creary, and Simon Chatwin. Introductionto Relational Databases. Berkeley, Calif.: McGraw-HillOsborne, 2003.

data communications 133Hellerstein, Joseph S., and Michael Stonebreaker, eds. Readingsin Database Systems. 4th ed. Cambridge, Mass.: MIT Press,2005.Hoffer, Jeffrey A., Mary Prescott, and Fred McFadden. ModernDatabase Management. 8th ed. Upper Saddle River, N.J.: PrenticeHall, 2006.Powell, Gavin. Beginning XML Databases. Indianapolis: Wrox,2006.“Web Programming: Databases.” Available online. URL: http://www.webreference.com/programming/databases.html.Accessed July 8, 2007.Williams, Hugh E., and David Lane. Web Database Applicationswith PHP and MySQL. 2nd ed. Sebastapol, Calif.: O’ReillyMedia, 2004.data communicationsBroadly speaking, data communications is the transfer ofdata between computers and their users. At its most abstractlevel, data communications requires two or more computers,a device to turn data into electronic signals (and backagain), and a transmission medium. Telephone lines, fiberoptic cable, network (Ethernet) cable, video cable, radio(wireless), or other kinds of links can be used. Finally, theremust be software that can manage the flow of data.Until recently, the modem was the main device usedto connect personal computers to information services orModern data communications can be thought of as a series of layers,from the actual physical connection (such as a cable) at the“bottom” to the operations of software such as Web browsers or e-mail programs at the highest level.networks (see modem). In general, data being sent over acommunications link must be sent one bit at a time (this iscalled serial transmission, and is why an external modem isconnected to a computer’s serial port). However most phonecables and other links are multiplexed, meaning that theycarry many channels (with many streams of data bits) atthe same time.To properly recognize data in a bit stream coming over alink, the transmission system must use some method of flowcontrol and have some way to detect errors (see error correction).Typically, the data is sent as groups or “frames”of bits. The frame includes a checksum that is verified bythe receiver. If the expected and actual sums don’t match,the recipient sends a “negative acknowledgment” messageto the sender, which will retransmit the data. In the originalsystem, the sender waited until the recipient acknowledgedeach frame before sending the next, but modern protocolsallow the sender to keep sending while the frames beingreceived are waiting to be checked.The actual transmission of data over a line can be consideredto be the lowest level of the data communicationsscheme. Above that is packaging of data as used and interpretedby software. Unless two computers are directly connected,the data is sent over a network, either a local areanetwork (LAN) or a wide-area network such as the globalInternet. A network consists of interconnected nodes thatinclude switches or routers that direct data to its destination(see network). Networks such as the Internet usepacket-switching: Data is sent as individual packets thatcontain a “chunk” of data, an address, and an indicationof where the data fits within the message as a whole. Thepackets are routed at the routers using software that triesto find the fastest link to the destination. When the packetsarrive at the destination, they are reassembled into theoriginal message.ApplicationsData communications are the basis both for networks andfor the proper functioning of servers that provide servicessuch as World Wide Web pages, electronic mail,online databases, and multimedia content (such as audioand streaming video). While Web page design and e-commerceare the “bright lights” that give cyberspace its character,data communications are like the plumbing withoutwhich computers cannot work together. The growingdemand for data communications, particularly broadbandservices such as DSL and cable modems, translates into asteady demand for engineers and technicians specializingin the maintenance and growth of this infrastructure (seebroadband).Besides keeping up with the exploding demand formore and faster data communications, the biggest challengefor data communications in the early 21st centuryis the integration of so many disparate methods of communications.A user may be using an ordinary phoneline (19th-century technology) to connect to the Internet,while the phone company switches might be a mixtureof 1970s or later technology. The same user mightgo to the workplace and use fast Ethernet cables over a

134 data compressionlocal network, or connect to the Internet through DSL,an enhanced phone line. Traveling home, the user mightuse a personal digital assistant (PDA) with a wireless linkto make a restaurant reservation (see wireless computing).The user wants all these services to be seamless andessentially interchangeable, but today data communicationsis more like roads in the early days of the automobile—afew fast paved roads here and there, but manybumpy dirt paths.Further ReadingForouszan Behrouz. Data Communications and Networking. NewYork: McGraw Hill, 2006.Stallings, William. Data and Computer Communications. 8th ed.Upper Saddle River, N.J.: Prentice Hall, 2006.Strangio, Christopher E. “Data Communications Basics.” Availableonline. URL: http://www.camiresearch.com/Data_Com_Basics/data_com_tutorial.html. Accessed July 8, 2007.White, Curt. Data Communications and Computer Networks: A BusinessUser’s Approach. 4th ed. Boston: Course Technology,2006.data compressionThe process of removing redundant information from dataso that it takes up less space is called data compression.Besides saving disk space, compressing data such as e-mailattachments can make data communications faster.Compression methods generally begin with the realizationthat not all characters are found in equal numbers intext. For example, in English, letters such as e and s arefound much more frequently than letters such as j or x.By assigning the shortest bit codes to the most commoncharacters and the longer codes to the least common characters,the number of bits needed to encode the text can beminimized.Huffman coding, first developed in 1952, is an algorithmthat uses a tree in which the pairs of the least probable (thatis, least common) characters are linked, the next least probablelinked, and so on until the tree is complete.Another coding method, arithmetic coding, matchescharacters’ probabilities to bits in such a way that the samebit can represent parts of more than one encoded character.This is even more efficient than Huffman coding, but thenecessary calculations make the method somewhat slowerto use.Another approach to compression is to look for words(or more generally, character strings) that match thosefound in a dictionary file. The matching strings are replacedby numbers. Since a number is much shorter than a wholeword or phrase, this compression method can greatlyreduce the size of most text files. (It would not be suitablefor files that contain numerical rather than text data, sincesuch data, when interpreted as characters, would look like arandom jumble.)The Lempel-Ziv (LZ) compression method does notuse an external dictionary. Instead, it scans the file itselffor text strings. Whenever it finds a string that occurredearlier in the text, it replaces the later occurrences withan offset, or count of the number of bytes separating theA basic approach to data compression is to look for recurring patternsand store them in a “dictionary.” Each occurrence of thepattern can then be replaced by a brief reference to the dictionaryentry. The resulting file may then be considerably smaller than theoriginal.occurrences. This means that not only common words butcommon prefixes and suffixes can be replaced by numbers.A variant of this scheme does not use offsets to thefile itself, but compiles repeated strings into a dictionaryand replaces them in the text with an index to their positionin the dictionary.Graphics files can often be greatly compressed by replacinglarge areas that represent the same color (such as a bluesky) with a number indicating the count of pixels with thatvalue. However, some graphics file formats such as GIF arealready compressed, so further compression will not shrinkthem much.More exotic compression schemes for graphics can usefractals or other iterative mathematical functions to encodepatterns in the data. Most such schemes are “lossy” in thatsome of the information (and thus image texture) is lost,but the loss may be acceptable for a given application. Lossycompression schemes are not used for binary (numeric dataor program code) files because errors introduced in a programfile are likely to affect the program’s performance (ifnot “break” it completely). Though they may have less seriousconsequences, errors in text are also generally consideredunacceptable.TrendsThere are a variety of compression programs used onunix systems, but variants of the Zip program are nowthe overwhelming favorite on Windows-based systems. Zipcombines compression and archiving. Archiving, or thebundling together of many files into a single file, contributesa further reduction in file size. This is because files inmost file systems must use a whole number of disk sectors,even if that means wasting most of a sector. Combining filesinto one file means that at most a bit less than one sectorwill be wasted.

data mining 135Further ReadingArimura, Mitsuharu. “Mitsuharu Arimura’s Bookmarks on SourceCoding/Data Compression.” Available online. URL: http://www.hn.is.uec.ac.jp/~arimura/compression_links.html.Accessed July 8, 2007.“Data Compression Reference Center.” Available online. URL:http://www.rasip.fer.hr/_research/compress/index.html.Accessed July 8, 2007.Saloman, David. Data Compression: The Complete Reference. 4th ed.New York: Springer-Verlag, 2006.Sayood, Khalid. Introduction to Data Compression. 3rd ed. SanFrancisco: Morgan Kaufmann, 2005.data conversionThe developer of each application program that writes datafiles must define a format for the data. The format mustbe able to preserve all the features that are supported bythe program. For example, a word processing program willinclude special codes for font selection, typestyles (such asbold or italic), margin settings, and so on.In most markets there are more than one vendor, sothere is the potential for users to encounter the need toconvert files such as word processing documents from onevendor’s format to another. For example, a Microsoft Worduser needing to send a document to a user who has Word-Perfect, or the user may encounter another user who alsohas Microsoft Word, but a later version.There are some ways in which vendors can relieve someof their users’ file conversion issues (and thus potentialcustomer dissatisfaction). Vendors often include facilities toread files created by their major rivals’ products, and to savefiles back into those formats. This enables users to exchangefiles. Sometimes the converted document will look exactlylike the original, but in some cases there is no equivalencebetween a feature (and thus a code) in one application and afeature in the other application. In that case the formattingor other feature may not carry over into the converted version,or may be only partially successful.Vendors generally make a new version of an applicationdownwardly compatible with previous versions (seealso compatability and portability). This means that thenew version can read files created with the earlier versions.(After all, users would not be happy if none of their existingdocuments were accessible to their new software!) Similarly,there is usually a way to save a file from the later version inthe format of an earlier version, though features added in thelater version will not be available in the earlier format.Another strategy for exchanging otherwise incompatiblefiles is to find some third format that both applications canread. Thus Rich Text Format (RTF), a format that includesmost generic document features, is supported by most modernword processors. A user can thus export a file as RTFand the user of a different program will be able to read it(see rtf). Similarly, many database and other programs canexport files as a series of data values separated by commas(comma-delimited files), and the files can be then read by adifferent program and converted to its “native” format.A variety of format conversion utilities are available aseither commercial software or shareware. There are also businessesthat specialize in data conversion. While their servicescan be expensive, using them may be the best way to convertlarge numbers of files, rather than having to individuallyload and save them. Data conversion services can also handlemany “ancient” data files from the 1970s or even early 1980swhose formats are no longer supported by current software.Further ReadingHeuser, Werner. “Data Conversion and Migration Tools.” Availableonline. URL: http://dataconv.org/. Accessed July 8, 2007.“Media Conversion: Online File Conversions.” Available online.URL: http://www.iconv.com/. Accessed July 8, 2007.data dictionaryA modern enterprise database system can contain hundredsof separate data items, each with important characteristicssuch as field types and lengths, rules for validating the data,and links to various databases that use that item (see databasemanagement system). There can also be many differentviews or ways of organizing subsets of the data, and storedprocedures (program code modules) used to perform variousdata processing functions. A developer who is creatingor modifying applications that deal with such a vast databasewill often need to check on the relationships between dataelements, views, procedures, and other aspects of the system.One fortunate characteristic of computer science is thatmany tools can be applied to themselves, often because thecontents of a program is itself a collection of data. Thus, it ispossible to create a database that keeps track of the elementsof another database. Such a database is sometimes called adata dictionary. A data dictionary system can be developedin the same way as any other database, but many databasedevelopment systems now contain built-in facilities for generatingdata dictionary entries as new data items are defined,and updating definitions as items are linked together and newviews or stored procedures are defined. (A similar approachcan be seen in some software development systems that createa database of objects defined within programs, in order topreserve information that can be useful during debugging.)Data dictionaries are particularly important for creatingdata warehouses (see data warehouse), which are largecollections of data items that are stored together with theprocedures for manipulating and analyzing them.Further ReadingKreines, David. Oracle Data Dictionary Pocket Reference. Sebastapol,Calif.: O’Reilly Media, 2003.Pelzer, Trudy. “MySQL 5.0 New Features: Data Dictionary.”Available online. URL: http://dev.mysql.com/tech-resources/articles/mysql-datadictionary.html. Accessed July 8, 2007.data glove See haptics.data miningThe process of analyzing existing databases in order to finduseful information is called data mining. Generally, a database,whether scientific or commercial, is designed for a

136 data securityparticular purpose, such as recording scientific observationsor keeping track of customers’ account histories. However,data often has potential applications beyond thoseconceived by its collector.Conceptually, data mining involves a process of refiningdata to extract meaningful patterns—usually with somenew purpose in mind. First, a promising set or subset of thedata is selected or sampled. Particular fields (variables) ofinterest are identified. Patterns are found using techniquessuch as regression analysis to find variables that are highlycorrelated to (or predicted by) other variables, or throughclustering (finding the data records that are the most similaralong the selected dimensions). Once the “refined” datais extracted, a representation or visualization (such as areport or graph) is used to express newly discovered informationin a usable form.Similar (if simpler) techniques are being used to targetor personalize marketing, particularly to online customers.For example, online bookstores such as Amazon.com canfind what other books have been most commonly boughtby people buying a particular title. (In other words, identifya sort of reader profile.) If a new customer searches forthat title, the list of correlated titles can be displayed, withan increased likelihood of triggering additional purchases.Businesses can also create customer profiles based on theirlonger-term purchasing patterns, and then either use themfor targeted mailings or sell them to other businesses (seee-commerce). In scientific applications, observations canbe “mined” for clues to phenomena not directly related tothe original observation. For example, changes in remotesensor data might be used to track the effects of climateor weather changes. Data-mining techniques can even beapplied to the human genome (see bioinformatics).TrendsData mining of consumer-related information has emergedas an important application as the volume of e-commercecontinues to grow, the amount of data generated by largesystems (such as online bookstores and auction sites)increases, and the value of such information to marketersbecomes established. However, the use of consumer datafor purposes unrelated to the original purchase, often bycompanies that have no pre-existing business relationshipto the consumer, can raise privacy issues. (Data is oftenrendered anonymous by removing personal identificationinformation before it is mined, but regulations or otherways to assure privacy remain incomplete and uncertain.)The most controversial applications of data mining arein the area of intelligence and homeland security. Becausesuch applications are often shrouded in secrecy, the publicand even lawmakers have difficulty in assessing their valueand devising privacy safeguards. According to the GovernmentAccountability Office, as of 2007 some 199 differentdata-mining programs were in use by at least 52 federalagencies. One of the most controversial is ADVISE (AnalysisDissemination, Visualization, Insight and SemanticEnhancement), developed by the Department of HomelandSecurity since 2003. The program purportedly can matchand create profiles using government records and users’Web sites and blogs. Privacy advocates and civil libertarianshave raised concerns, and legislation has been introducedthat would require that all federal agencies report their dataminingactivities to Congress (see also counterterrorismand computers and privacy in the digital age.)Further ReadingClayton, Mark. “U.S. Plans Massive Data Sweep.” Christian ScienceMonitor, February 9, 2006, n.p. Available online. URL: http://www.csmonitor.com/2006/0209/p01s02-uspo.html. AccessedJuly 8, 2007.Dunham, Margaret H. Data Mining: Introductory and Advanced Topics.Upper Saddle River, N.J.: Prentice Hall, 2002.Markov, Zdravko, and Daniel T. Larose. Data Mining the Web:Uncovering Patterns in Web Content, Structure, and Usage.Hoboken, N.J.: Wiley, 2007.Tan, Pang-Ning, Michael Steinbach, and Vipin Kumar. Introductionto Data Mining. Upper Saddle River, N.J.: Pearson Education,2006.data securityIn most institutional computing environments, access toprogram and data files is restricted to authorized persons.There are several mechanisms for restricting file access in amultiuser or networked system.User StatusBecause of their differing responsibilities, users are oftengiven differing restrictions on access. For example, theremight be status levels ranging from root to administrator to“ordinary.” A user with root status on a UNIX system is ableto access any file or resource. Any program run by such auser inherits that status, and thus can access any resource.Generally, only the user(s) with ultimate responsibility forthe technical functioning of the system should be givensuch access, because commands used by root users have thepotential to wipe out all data on the system. A person withadministrator status may be able to access the files of otherusers and to access certain system files (in order to changeconfigurations), but will not be able to access certain coresystem files. Ordinary users typically have access only tothe files they create themselves and to files designated as“public” by other users.File PermissionsFiles themselves can have permission status. In UNIX,there are separate statuses for the user, any group to whichthe user belongs, and “others.” There are also three differentactivities that can be allowed or disallowed: reading, writing,and executing. For example, if a file’s permissions areUser Group Otherrwx rw- r—the user can read or write the file or (if it is a directory orprogram), execute it. Members of the same group can reador write, but not execute, while others can only read the filewithout being able to change it in any way. Operating systemssuch as Windows NT use a somewhat different struc-

data structures 137ture and terminology, but also provide for varying userstatus and access to objects.Record-level SecuritySecurity on the basis of whole directories or even files maybe too “coarse” for many applications. In a particular databasefile, different users may be given access to differentdata fields. For example, a clerk may have read-only accessto an employee’s basic identification information, but notto the results of performance evaluations. An administratormay have both read and write access to the latter. Usingsome combination of database management and operatingsystem level capabilities, the system will maintain lists ofuser accounts together with the objects (such as recordtypes or fields) they can access, and the types of access(read only or read/write) that are permitted. Rather thanassigning access capabilities separately for each user, theymay be defined for a group of similar users, and then individualusers can be assigned to the group.Other Security MeasuresSecurity is also important at the program level. Because abadly written (or malicious) program might destroy importantdata or system files, most modern operating systemsrestrict programs in a number of ways. Generally, each programis allowed to access only such memory as it allocatesitself, and is not able to change data in memory belongingto other running programs. Access to hardware devices canalso be restricted: an operating system component may havethe ability to access the innermost core of the operating system(where drivers interact directly with devices), whilean ordinary applications program may be able to accessdevices only through facilities provided by the operatingsystem.There are a number of techniques that unauthorizedintruders can use to try to compromise operating systems(see computer crime and security). Access capabilitiesthat are tied to user status are vulnerable if the user can getthe login ID and password for the account. If the accounthas a high (administrator or root) status, then the intrudermay be able to give viruses, Trojan horses, or other maliciousprograms the status they need in order to be able topenetrate the defenses of the operating system (see alsocomputer virus).Files that have intrinsically sensitive or valuable dataare often further protected by encoding them (see encryption).Encryption means that even intruders who gain readaccess to the file will need either to crack the encryption(very difficult without considerable time and computerresources) or somehow obtain the key. Encryption does notprevent the deletion or copying of a file, however, just theunderstanding of its contents.The dispersal of valuable or sensitive data (such as customers’social security numbers) across expanding networksincreases the risk of “data breaches” where the privacy,financial security, and even identity of thousands of peopleare compromised (see also identity theft). In recentyears, for example, there have been numerous cases wherelaptop computers containing thousands of sensitive recordshave been stolen from universities, financial institutions,or government agencies—in such cases there is often noway to know whether the thief will actually access the data.(Often affected individuals are notified that they may beat risk, and such prophylactic measures as credit monitoringare provided.) In response to public anxiety there hasbeen pressure for federal or state legislation that wouldmake companies responsible for breaches of their data andspecify compensation or other recourse for affected customers.(Opponents of such laws cite government reports thatfind that most data breaches do not lead to identity theft,and that the regulations would increase the cost of millionsof daily transactions.)There is a continuing tradeoff between security and easeof use. From the security standpoint, it might be assumedthat the more barriers or checkpoints that can be set upfor verifying authorization, the safer the system will be.However, as security systems become more complex, itbecomes more difficult to ensure that authorized users arenot unduly inconvenienced. If users are sufficiently frustrated,they will be tempted to try to bypass security, suchas by sharing IDs and passwords or making files they create“public.”Further ReadingGarretson, Cara. “The Do’s and Don’ts of Data Breaches: HowSecurity Professionals Can Lessen the Impact.” NetworkWorld, June 18, 2007, p. 1.Grant, Gross. “Gov’t Report: Data Breaches Don’t Often Result inID Theft.” PC World, July 6, 2007, n.p. Available online. URL:http://www.pcworld.com/article/id,134203-c,privacysecurity/article.html. Accessed July 8, 2007.Killmeyer, Jan. Information Security Architecture: An IntegratedApproach to Security in the Organization. 2nd ed. Boca Raton,Fla.: Auerbach Publications, 2006.Rasch, Max. “Strict Liability for Data Breaches?” Availableonline. URL: http://www.securityfocus.com/columnists/387.Accessed July 8, 2007.Tipton, Harold F., and Micki Krause. Information Security ManagementHandbook. 6th ed. Boca Raton, Fla.: Auerbach Publications,2007.data structuresA data structure is a way of organizing data for use in acomputer program. There are three basic components to adata structure: a set of suitable basic data types, a way toorganize or relate these data items to one another, and a setof operations, or ways to manipulate the data.For example, the array is a data structure that canconsist of just about any of the basic data types, althoughall data must be of the same type. The way the data is organizedis by storing it in sequentially addressable locations.The operations include storing a data item (element) in thearray and retrieving a data item from the array.Types of Data StructuresThe data structures commonly used in computer scienceinclude arrays (as discussed above) and various types oflists. The primary difference between an array and a list isthat an array has no internal links between its elements,

138 data typeswhile a list has one or more pointers that link the elements.There are several types of specialized list. A tree is a listthat has a root (an element with no predecessor), and eachother element has a unique predecessor. The guarantee ofa unique path to each tree node can make the operationsof inserting or deleting an item faster. A stack is a listthat is accessible only at the top (or front). Any new itemis inserted (“pushed”) on top of the last item, and removing(“popping”) an item always removes the item that waslast inserted. This order of access is called LIFO (last in,first out). A list can also be organized in a first in, first out(FIFO) order. This type of list is called a queue, and isuseful in a situation where tasks must “wait their turn” forattention.Implementation IssuesThe implementation of any data structure depends on thesyntax of the programming language to be used, the datatypes and features available in the language, and the algorithmschosen for the data operations that manipulate thestructure. In traditional procedural languages such as C, thedata storage part of a data structure is often specified in onepart of the program, and the functions that operate on thatstructure are defined separately. (There is no mechanismin the language to link them.) In object-oriented languagessuch as C++, however, both the data storage declarationsand the function declarations are part of the same entity, aclass. This means that the designer of the data structurehas complete control over its implementation and use.Together with algorithms, data structures make up theheart of computer science. While there can be numerousvariations on the fundamental data structures, understandingthe basic forms and being able to decide which oneto use to implement a given algorithm is the best way toassure effective program design.Further ReadingDrozdek, Adam. Data Structures and Algorithms in C++. 3rd ed.Boston: Course Technology, 2004.Ford, William H., and William R. Topp. Data Structures with Java.Upper Saddle River, N.J.: Prentice Hall, 2004.Lafore, Robert. Data Structures & Algorithms in Java. 2nd ed. Indianapolis:Sams, 2003.Storer, J. A. An Introduction to Data Structures and Algorithms. NewYork: Springer, 2002.data typesAs far as the circuitry of a computer is concerned, there’sonly one kind of data—a series of bits (binary digits) fillinga series of memory locations. How those bits are to beinterpreted by the people using the computer is entirelyarbitrary. The purpose of data types is to define useful conceptssuch as integer, floating-point number, or character interms of how they are stored in computer memory.Thus, most computer languages have a data type calledinteger, which represents a whole number that can be storedin 16 bits (two bytes) of memory. When a programmerwrites a declaration such as:int Counter;in the C language, the compiler will create machine instructionsthat set aside two bytes of memory to hold the contentsof the variable Counter. If a later statement says:Counter = Counter + 1;(or its equivalent, Counter++) the program’s instructionsare set up to fetch two bytes of memory to the processor’saccumulator, add 1, and store the result back into the twomemory bytes.Similarly, the data type long represents four bytes (32bits) worth of binary digits, while the data type float storesa floating-point number that can have a whole part and adecimal fraction part (see numeric data). The char (character)type typically uses only a single byte (8 bits), whichis enough to hold the basic ASCII character codes up to 255(see characters and strings).The Bool (Boolean) data type represents a simple true orfalse (usually 1 or 0) value (see Boolean operators).Structured Data TypesThe preceding data types all hold single values. However,most modern languages allow for the construction of datatypes that can hold more than one piece of data. The arrayis the most basic structured data type; it represents a seriesof memory locations that hold data of one of the basictypes. Thus, in Pascal an array of integer holds integers,each taking up two bytes of memory.Many languages have composite data types that canhold data of several different basic types. For example, thestruct in C or the record in Pascal can hold data such as aperson’s first and last name, three lines of address (all arraysof characters, or strings), an employee number (perhaps aninteger or double), a Boolean field representing the presenceor absence of some status, and so on. This kind of data typeis also called a user-defined data type because programmerscan define and use these types in almost the same ways asthey use the language’s built-in basic types.What is the difference between data types and datastructures? There is no hard-and-fast distinction. Generally,data structures such as lists, stacks, queues, andtrees are more complex than simple data types, becausethey include data relationships and special functions(such as pushing or popping data on a stack). However,a list is the fundamental data type in list-processing languagessuch as Lisp, and string operators are built intolanguages such as Snobol. (See list processing, stack,queue, and tree.)Further, in many modern languages fundamental andstructured data types are combined seamlessly into classesthat combine data structures with the relevant operations(see class and object-oriented programming).Further ReadingPrata, Stephen. C Primer Plus. 5th ed. Indianapolis: Sams, 2003.———. C++ Primer Plus. 5th ed. Indianapolis: Sams, 2005.“Type System.” Wikipedia. Available online. URL: http://en.wikipedia.org/wiki/Type_system. Accessed July 8, 2007.Watt, David A., and Deryck F. Brown. Java Collections: An Introductionto Abstract Data Types, Data Structures, and Algorithms.New York: Wiley, 2001.

decision support system 139data warehouseModern business organizations create and store a tremendousamount of data in the form of transactions that becomedatabase records. Increasingly, however, businesses arerelying on their ability to use data that was collected for onepurpose (such as sales, customer service, and inventory)for purposes of marketing research, planning, or decisionsupport. For example, transaction data might be revisitedwith a view to identifying the common characteristics ofthe firm’s best customers or determining the best way tomarket a particular type of product. In order to conductsuch research or analysis, the data collected in the course ofbusiness must be stored in such a way that it is both accurateand flexible in terms of the number of different ways inwhich it can be queried. The idea of the data warehouse isto provide such a repository for data.When data is used for particular purposes such as salesor inventory control, it is usually structured in recordswhere certain fields (such as stock number or quantity)are routinely processed. It is not so easy to ask a differentquestion such as “which customers who bought thisproduct from us also bought this other product within sixmonths of their first purchase?” One way to make it easierto query data in new ways is to store the data not in recordsbut in arrays where, for example, one dimension mightbe product numbers and another categories of customers.This approach, called Online Analytical Processing (OLAP)makes it possible to extract a large variety of relationshipswithout being limited by the original record structure.ImplementationThe key in designing a data warehouse is to provide a waythat researchers using analytical tools (such as statisticsprograms) can access the raw data in the underlying database.Software using query languages such as SQL canserve as such a link. Thus, the researcher can define a queryThe general process of warehousing data. The data warehouse addsvalue to the data by further structuring it so relationships can beexplored by analysts.using the many dimensions of the data array, and the OLAPsoftware (also called middleware) translates this query intothe appropriate combination of queries against the underlyingrelational database.The data warehouse is closely related to the conceptof data mining. In fact, data mining can be viewed as theexploitation of the collection of views, queries, and otherelements that can be generated using the data warehouse asthe infrastructure (see data mining).Further ReadingData Warehousing Information Center. Available online. URL:http://www.dwinfocenter.org/. Accessed July 8, 2007.DM Review/dataWarehouse.com Available online. URL: http://www.datawarehouse.com/. Accessed July 8, 2007.Inmon, W. H. Building the Data Warehouse. 4th ed. Indianapolis:Wiley, 2005.Kimball, Ralph, and Margy Ross. The Data Warehouse Toolkit: TheComplete Guide to Dimensional Modeling. 2nd ed. Indianapolis:Wiley, 2002.DBMS See database management system.decision support systemA decision support system (DSS) is a computer applicationthat focuses on providing access to or analysis of thekey information needed to make decisions, particularly inbusiness. (It can be thought of as a more narrowly focusedapproach to computer assistance to management—see managementinformation system.)The development of DSS has several roots reaching backto the 1950s. This includes operational analysis and the theoryof organizations and the development of the first interactive(rather than batch-processing) computer systems.Indeed, the SAGE automated air defense system developedstarting in the 1950s could be described as a military DSS.The system presented real-time information (radar plots)and enabled the operator to select and focus on particularelements using a light pen. By the 1960s more-systematicresearch on DSS was underway and included the provocativeidea of “human-computer symbiosis” for problem solving(see Licklider, J. C. R.).The “back end” of a DSS is one or more large databases(see data warehouse) that might be compiled from transactionrecords, statistics, online news services, or other sources.The “middle” of the DSS process includes the ability to analyzethe data (online analytical processing, or OLAP; see alsodata mining). Other elements that might be included in aDSS are rules-based systems (see expert system) and interactivemodels (see simulation). These elements can help theuser explore alternatives and “what if” scenarios.The structure of a DSS is sometimes described as modeldriven (generally using a small amount of selected data),data driven (based on a large collection of historical data),knowledge driven (perhaps using an expert system), orcommunications driven (focusing on use of collaborativesoftware—see groupware, as well as more recent developments)(see wikis and Wikipedia).

140 Dell, Inc.User Interface—The “Front End”All the data and tools in the world are of little use if theuser cannot work with it effectively (see user interface).Information or the results of queries or modeling must bedisplayed in a way that is easy to grasp and use. (A spreadsheetwith nothing highlighted or marked would be a poorchoice.) Graphical “widgets” such as dials, buttons, sliders,and so on can help the user see the results and decide whatto look at next (see digital dashboard).Another key principle is that decision making in themodern world is as much a social as an individual process.Therefore a DSS should facilitate communication and collaboration(or interface with software that does so).A variety of specialized DSSs have been developed forvarious fields. Examples include PROMIS (for medical decisionmaking) and Carnegie Mellon’s ZOG/KMS, which hasbeen used in military and business settings.Further ReadingGreenes, Robert A., ed. Clinical Decision Support: The Road Ahead.Orlando, Fla.: Academic Press, 2006.Gupta, Jatinder N. D., Guisseppi A. Forgionne, and Manuel Mora T.,eds. Intelligent Decision-Making Support Systems. New York:Springer, 2006.Power, D. J. “A Brief History of Decision Support Systems.” Version4.0. Available online. URL: http://dssresources.com/history/dsshistory.html. Accessed September 10, 2007.Turban, Efraim, et al. Decision Support and Business Intelligence Systems.8th ed. Upper Saddle River, N.J.: Prentice-Hall, 2006.Dell, Inc.Dell Computer (NASDAQ: DELL) is one of the world’s leadingmanufacturers and sellers of desktop and laptop computers(see personal computer). By 2008 Dell had morethan 88,000 employees worldwide.The company was founded by Michael Dell, a student atthe University of Texas at Austin whose first company wasPC’s Limited, founded in 1984. Even at this early stage Dellsuccessfully employed several practices that would cometo typify the Dell strategy: Sell directly to customers (notthrough stores), build each machine to suit the customer’spreferences, and be aggressive in competing on price.In 1988 the growing company changed its name toDell Computer Corporation. In the early 1990s Dell triedan alternative business model, selling through warehouseclubs and computer superstores. When that met with littlesuccess, Dell returned to the original formula. In 1999 Dellovertook Compaq to become the biggest computer retailerin America.Generally, the Dell product line has aimed at two basicsegments: business-oriented (OptiPlex desktops and Latitudelaptops) and home/consumer (XPS desktops andInspiron laptops, and in 2007, Inspiron desktops).Challenges and DiversificationAround 2002, Dell, perhaps facing the growing commoditypricing of basic PCs, began to expand into computerperipherals (such as printers) and even home entertainmentproducts (TVs and audio players). In 2003 the companychanged its name to Dell, Inc. (dropping “Computer”). Dellalso experienced an increase in international sales in 2005,while achieving a first place ranking in Fortune magazineas “most admired company.” However, the company alsomade some missteps, losing $300 million because of faultycapacitors on some motherboards. Earnings continued tofall short of analysts’ expectations, and in January 2007Michael Dell returned as CEO after the resignation of KevinB. Rollins, who had held the post since 2004.Meanwhile, Dell has made further attempts at diversifyingthe product line. In 2006 the company began, for thefirst time, to introduce AMD (instead of Intel) processorsin certain products, and in 2007 Dell responded to customersuggestions by announcing that some models couldbe ordered with Linux rather than Microsoft Windowsinstalled. Also in 2007, Dell acquired Alienware, maker ofhigh-performance gaming machines.Dell has struggled to boost its sagging revenue as itlost ground to competitors, notably HP. Known primarilyas a mail-order and online company, Dell has announcedthat it will also sell PCs through “big box” retailers suchas Wal-Mart.Dell continues to receive praise and criticism from variousquarters. On the positive side, the company has beenpraised for its computer-recycling program by the NationalRecycling Coalition. Dell products also tend to score at ornear the top in performance reviews by publications suchas PC Magazine.On the other hand, there have been complaints aboutDell’s technical support operation. Technicians apparentlyfollow “scripts” very closely, making customers take systemsapart and follow troubleshooting directions regardlessof what the customer might already know or have done.The increasing “offshoring” of support has also led to complaintsabout language and communication problems.Further ReadingDell, Inc. Available online. URL: http://www.dell.com. AccessedSeptember 10, 2007.Dell, Michael, and Catherine Fredman. Direct from Dell: Strategiesthat Revolutionized an Industry. New York: HarperBusiness,2006.Holzner, Steven. How Dell Does It: Using Speed and Innovation toAchieve Extraordinary Results. New York: McGraw-Hill, 2006.demonThe unusual computing term demon (sometimes spelleddaemon) refers to a process (program) that runs in thebackground, checking for and responding to certain events.The utility of this concept is that it allows for automation ofinformation processing without requiring that an operatorinitiate or manage the process.For example, a print spooler demon looks for jobs thatare queued for printing, and deals with the negotiations necessaryto maintain the flow of data to that device. Anotherdemon (called chron in UNIX systems) reads a file describingprocesses that are designated to run at particular datesor times. For example, it may launch a backup utility everymorning at 1:00 a.m. E-mail also depends on the periodicoperation of “mailer demons.”

Dertouzos, Michael L. 141While the term demon originated in the UNIX culture,similar facilities exist in many operating systems. Even inthe relatively primitive MS-DOS for IBM personal computersof the 1980s, the ability to load and retain small utilityprograms that could share the main memory with the currentlyrunning application allowed for a sort of demon thatcould spool output or await a special keypress. MicrosoftWindows systems have many demon-like operating systemcomponents that can be glimpsed by pressing the Ctrl-Alt-Delete key combination.The sense of autonomy implied in the term demon is insome ways similar to that found in bots or software agentsthat can automatically retrieve information on the Internet,or in the Web crawler, which relentlessly pursues, records,and indexes Web links for search engines. (See softwareagent and search engine.)Further ReadingBrock, Dean, and Bob Benites. Mastering Tools, Taming Daemons:UNIX for the Wizard Apprentice. Greenwich, Conn.: ManningPublications, 1995.Stevens, W. Richard. Advanced Programming in the UNIX Environment.Upper Saddle River, N.J.: Addison-Wesley, 2005.“UNIX Daemons in Perl.” Available online. URL: http://www.webreference.com/perl/tutorial/9/. Accessed July 8, 2007.Dertouzos, Michael L.(1936–2001)Greek-AmericanComputer Scientist, FuturistBorn in Athens, Greece, on November 5, 1936, MichaelDertouzos spent adventurous boyhood years accompanyinghis father (an admiral) in the Greek navy’s destroyersand submarines. He became interested in Morse Code,shipboard machinery, and mathematics. At the age of 16he read an article about Claude Shannon’s work in informationtheory and a project at the Massachusetts Instituteof Technology that sought to build a mechanical robot“mouse.” He quickly decided that he wanted to come toAmerica to study at MIT.After the hardships of the World War II years intervened,Dertouzos received a Fulbright scholarship thatplaced him in the University of Arkansas, where he earnedhis bachelor’s and master’s degrees while working on acoustic-mechanicaldevices for the Baldwin Piano Company. Hewas then able to fulfill his boyhood dream by receiving hisPh.D. from MIT, then promptly joined the faculty. He wasdirector of MIT’s Laboratory for Computer Science (LCS)starting in 1974. The lab has been a hotbed of new ideasin computing, including computer time-sharing, Ethernetnetworking, and public-key cryptography. Dertouzos alsoembraced the growing Internet and serves as coordinator ofthe World Wide Web consortium, a group that seeks to createstandards and plans for the growth of the network.Combining theoretical interest with an entrepreneur’seye on market trends, Dertouzos started a small companycalled Computek in 1968. It made some of the first “smartterminals” that included their own processors.In the 1980s, Dertouzos began to explore the relationshipbetween developments and infrastructure ininformation processing and the emerging “informationmarketplace.” However, the spectacular growth of theinformation industry has taken place against a backdrop ofthe decline of American manufacturing. Dertouzos’s 1989book, Made In America, suggested ways to revitalize Americanindustry.During the 1990s, Dertouzos brought MIT into closerrelationship with the visionary designers who were creatingand expanding the World Wide Web. When Tim Berners-Lee and other Web pioneers were struggling to create theWorld Wide Web consortium to guide the future of the newtechnology, Dertouzos provided extensive guidance to helpthem set their agenda and structure. (See World WideWeb and Berners-Lee, Tim.)Dertouzos was dissatisfied with operating systems suchas Microsoft Windows and with popular applications programs.He believed that their designers made it unnecessarilydifficult for users to perform tasks, and spent moretime on adding fancy features than on improving the basicusability of their products. In 1999, Dertouzos and the MITLCS announced a new project called Oxygen. Working incollaboration with the MIT Artificial Intelligence Laboratory,Oxygen was intended to make computers “as natural apart of our environment as the air we breathe.”As a futurist, Dertouzos tried to paint vivid pictures ofpossible future uses of computers in order to engage thegeneral public in thinking about the potential of emergingtechnologies. His 1995 book, What Will Be, paints a vividportrait of a near-future pervasively digital environment.His imaginative future is based on actual MIT research,such as the design of a “body net,” a kind of wearablecomputer and sensor system that would allow people tonot only keep in touch with information but also to communicatedetailed information with other people similarlyequipped. This digital world will also include “smartrooms” and a variety of robot assistants, particularly in thearea of health care. However, this and his 2001 publication,The Unfinished Revolution, are not unalloyed celebrationsof technological wizardry. Dertouzos has pointed outthat there is a disconnect between technological visionarieswho lack understanding of the daily realities of mostpeoples’ lives, and humanists who do not understand theintricate interconnectedness (and thus social impact) ofnew technologies.Dertouzos was given an IEEE Fellowship and awardedmembership in the National Academy of Engineering, Hedied on August 27, 2001, after a long bout with heart disease.He was buried in Athens near the finish line for theOlympic marathon.Further ReadingDertouzos, Michael. L. The Unfinished Revolution: How to MakeTechnology Work for Us—Instead of the Other Way Around.New York: HarperCollins, 2002.———. What Will Be: How the New World of Information WillChange Our Lives. New York: HarperCollins, 1997.“Farewell to a Visionary of the Computer Age.” Business Week,September 17, 2001, p. 101.

142 design patternsdesign patternsDesign patterns are an attempt to abstract and generalizewhat is learned in solving one problem so that it canbe applied to future similar problems. The idea was firstapplied to architecture by Christopher Alexander in hisbook A Pattern Language. Alexander described a pattern asa description of situations in which a particular problemoccurs, with a solution that takes into account the factorsthat are “invariant” (not changed by context). Guidance forapplying the solution is also provided.For example, a bus stop, a waiting room, and a line ata theme park are all places where people wait. A “place towait” pattern would specify the problem to be solved (howto make waiting as pleasant as possible) and suggest solutions.Patterns can have different levels of abstraction orscales on which they apply (for example, an intimate theaterand a stadium are both places of entertainment, butone is much larger than the other).Patterns in turn are linked into a network called a patternlanguage. Thus when working with one pattern, thedesigner is guided to consider related patterns. For example,a pattern for a room might relate to patterns for seatingor grouping the occupants.Patterns in SoftwareThe concept of patterns and pattern languages carries overwell into software design. As with architectural patterns,a software pattern describes a problem and solution, alongwith relevant structures (see class and object-orientedprogramming). Note that patterns are not executable code;they are at a higher level (one might say abstract enough tobe generalizable, specific enough to be applicable).Software patterns can specify how objects are createdand ways in which they function and interface with otherobjects. Patterns are generally documented using a commonformat; one example is provided in the book Design Patterns.This scheme has the following sections:• name and classification• intent or purpose• alternative names• problem—the kind of problem the pattern addresses,and conditions under which it can be used• applicability—typical situations of use• structure description—such as class or interactiondiagrams• participants—classes and objects involved in the patternand the role each plays• collaboration—how the objects interact with oneanother• consequences—the expected results of using the pattern,and possible side effects or shortcomings• implementation—explains a way to implement thepattern to solve the problem• sample code—usually in a commonly used programminglanguage• known uses—actual working applications of thepattern• related patterns—other patterns that are similar orrelated, with a description of how they differAn example given in Design Patterns is the “publishsubscribe”pattern. This pattern describes how a numberof objects (observers) can be dependent on a “subject.” Allobservers are “subscribed” to the subject, so they are notifiedwhenever any data in the subject changes. This patterncould be used, for example, to set up a system where differentreports, spreadsheets, etc., need to be updated whenevernotified by a controlling object that has received new data.Some critics consider the use of patterns to be tooabstract and inefficient. Since a pattern has to be re-implementedfor each use, it has been argued that well-documented,reusable classes or objects would be more useful.Proponents, however, argue that “design reuse” is morepowerful than mere “object reuse.” A pattern provides awhole “language” for talking about a problem and its provensolutions, and can help both the original designer and othersunderstand and extend the design.Further ReadingAlexander, Christopher. A Pattern Language: Towns, Buildings,Construction. New York: Oxford University Press, 1977.“Design Patterns.” IBM Research. Available online. URL: http://www.research.ibm.com/designpatterns/. Accessed September10, 2007.Freeman, Eric, and Elisabeth Freeman. Head First Design Patterns.Sebastapol, Calif.: O’Reilly, 2004.Gamma, Erich, et al. Design Patterns: Elements of Reusable Object-Oriented Software. Upper Saddle River, N.J.: Addison-WesleyProfessional, 1995.Kurotsuchi, Brian T. “Welcome to the Wonderful World of DesignPatterns.” Available online. URL: http://www.csc.calpoly.edu/~dbutler/tutorials/winter96/patterns/. Accessed September10, 2007.desktop publishing (DTP)Traditionally documents such as advertisements, brochures,and reports were prepared by combining typed or printedtext with pasted-in illustrations (such as photographs anddiagrams). This painstaking layout process was necessaryin order to produce “camera-ready copy” from which aprinting company could produce the final product.Starting in the late 1980s, desktop computers becamepowerful enough to run software that could be used to createpage layouts. In addition, display hardware gained ahigh enough resolution to allow for pages to be shown onthe screen in much the same form as they would appear onthe printed page. (This is known by the acronym WYSI-WYG, or “what you see is what you get.”) The final ingredientfor the creation of desktop publishing was the advent ofaffordable laser or inkjet printers that could print near printquality text and high-resolution graphics (see printers).This combination of technologies made it feasible fortrained office personnel to create, design, and produce many

developing nations and computing 143documents in-house rather than having to send copy to aprinting company. Adobe’s PageMaker program soon becamea standard for the desktop publishing industry, appearing firston the Apple Macintosh and later on systems running MicrosoftWindows. (The Macintosh’s support for fonts and WYSI-WYG displays gave it a head start over the Windows PC in theDTP industry, and to this day many professionals prefer it.)There is no hard-and-fast line between desktop publishingand the creation of text itself. Modern word processingsoftware such as Microsoft Word includes a variety of featuresfor selection and sizing of fonts, and the ability to definestyles for creating headings, types of paragraphs, and so on(see word processing). Word and other programs also allowfor the insertion and placement of graphics and tables, thedivision of text into columns, and other layout features. Ingeneral, however, word processing emphasizes the creationof text (often for long documents), while desktop publishingsoftware emphasizes layout considerations and the fine-tuningof a document’s appearance. Thus, while a word processormight allow the selection of a font in a given point size, adesktop publishing program allows for the exact specificationof leading (space between lines) and kerning (the adjustmentof space between characters). Most desktop publishing programscan import text that was originally created in a wordprocessor. This is helpful because using desktop publishingsoftware to create the original text can be tedious.Desktop publishing is generally used for short documentssuch as ads, brochures, and reports. Material to bepublished as a book or magazine article is normally submittedby the author as a word processing document. The publisher’sproduction staff then creates a print-ready version.Books and other long documents are generally producedusing in-house computer typesetting facilities.Today desktop publishing is part of a range of technologiesused for the production of documents and presentations.Document designers also use drawing programs (suchas Corel Draw) and photo manipulation programs (such asAdobe Photoshop) in preparing illustrations. Further, thegrowing use of the Web means that many documents mustbe displayable on Web pages as well as in print. Adobe’s PortableDocument Format (PDF) is one popular way of creatingfiles that exactly portray printed text (see PDF).Further ReadingBlattner, D., and N. Davis, eds. The QuarkXPress Book: For Macintoshand Windows. Berkeley, Calif.: Peachpit Press, 1998.“Desktop Publishing News.” Available online. URL: http://desktoppublishing.com/_news1.html. Accessed November2007.Parker, Roger C. Web Design and Desktop Publishing for Dummies.2nd ed. New York: Hungry Minds, 1997.“Resources for Desktop Publishers.” Available online. URL: http://www.nlightning._com/dtpsbiblio.html. Accessed November2007.Shushan, R. and D. Wright, with L. Lewis. Desktop Publishing byDesign: Everyone’s Guide to PageMaker6. 4th ed. Redmond,Wash.: Microsoft Press, 1996.developing nations and computingMost writing about computer technology tends to focus ondevelopments in technically advanced nations, such as theUnited States, European Union, and Japan. There is alsogrowing coverage of the rapidly developing informationeconomy in the world’s two most populous nations, Indiaand China. But what about the poorest or least developednations, particularly those in Africa?InfrastructureA common problem in developing countries is a lack ofbasic infrastructure to support electronic devices—phonelines, television cables, even a reliable power grid. (Abouttwo billion people on this planet still have no access to electricity!)One way around this obstacle is to skip over the wiredstage of development in favor of wireless connections, perhapsusing battery or even solar power. The necessity forlarge government investments in infrastructure can then beavoided in favor of mobile, distributed, flexible access thatcan be gradually spread and scaled up. Already, in some ofthe poorest nations mobile phone use has been growing atan annual rate of 50 percent or more.Once access to communications and data is provided,users can immediately start getting an economic return orotherwise improving their lives. Farmers, for example, canget weather reports and keep in touch with market prices.Of course online communications might also give farmersa tool for organizing themselves politically or economically(such as into co-ops). People start to get in touch withdevelopments around the world that might affect them, anddiscover possible ways to a better life. However, authoritariangovernments often resist such trends because theyfear the development of well-connected democratic reformmovements.Closing the GapMuch of the barrier to developing countries joining the networkedworld is human rather than technological. Beforepeople can learn to use computers, they need to be able toread. They also need some idea of what science and technologyare about and why they are important for their economicwell-being.Beyond people learning to use computers to communicate,or in agriculture or commerce, a developing countryneeds to have enough people with the advanced skillsneeded for a self-sustaining information economy. Theseinclude technicians, support staff, teachers, engineers, programmers,and computer scientists.One reason for the rapid growth of computing in Indiaand especially China is that these countries, while still havingmillions of people living on subsistence, also have effectiveeducational systems including advanced training. Theirgrowing pool of skilled but relatively inexpensive workersin turn attracts foreign investment capital. In additionto China and India, other nations with strong electronicsmanufacturing industries include Singapore, Korea, Malaysia,Mexico, and Brazil.The United Nations has developed the TechnologyAchievement Index (TAI) to measure the ability of a countryto innovate, to effectively use new and existing technology,and to build a base of technically skilled workers.

144 device driverOne Laptop per ChildWhile the conventional view of technological developmentstresses the importance of infrastructure and skills, somevisionary educational activists are suggesting a way to“jump-start” the information economy in poor and developingcountries. They note that despite the potential ofwireless technology, adequate computing power for joiningthe world network has simply been too expensive for allbut the elite in developing countries. (A $400 no-frills PCcosts more than the annual per capita income of Haiti, forexample.)In response, MIT computer scientists (see Mit MediaLab and Negroponte, Nicholas) have started an initiativecalled One Laptop Per Child. Their machine (introduced asa prototype in 2005) includes the following features:• very low power consumption (2–3 watts)• lower and higher power modes (the latter, for example,can provide backlighting for the screen when anexternal power source is available)• ability to use a variety of batteries or an externalpower source, including a hand-powered generator• built-in wireless networking• tough construction, including a water-resistant membranekeyboard• flash memory instead of a hard drive or CD-ROM• built-in color camera, microphone, and stereo speakers• open-source Linux operating system and other software,including programming languages especiallyuseful for learnersThe computer is intended ultimately to cost no more than$100 per unit, and is to be distributed through participatinggovernments. Countries that have made at least tentativecommitments to the project as of 2007 include Argentina,Cambodia, Costa Rica, Dominican Republic, Egypt, Greece,Libya, Nigeria, Pakistan, Peru, Rwanda, Tunisia, Uruguay,and, in the United States, the states of Massachusetts andMaine.The underlying philosophy of the project is based on“constructivist learning,” the idea that children can learnpowerful ideas through using suitable interactive systems(see logo and Papert, Seymour). In a way it is intendedto be a sort of lever to create a generation with the skills tofunction in the 21st-century information economy, withoutre-creating the cumbersome industrial-style educationalsystems of the previous 200 years.Although, generally, some well received critics are concernedabout the environmental impact of producing (andeventually disposing of) millions more computers, whileothers (including some officials in developing countries)believe the money for providing computers to childrenshould be used instead for more urgent needs such as cleanwater, public health, and basic school supplies.Whether using top-down or bottom-up approaches, theweb of connection, communication, and information continuesits rapid though uneven spread around the world.However, as new technologies continue to emerge in thedeveloped world, the position of technological “have-nots”may worsen if effective education and access programs arenot developed.Further ReadingDesai, Meghnad, et al. “Measuring the Technological Achievementof Nations and the Capacity to Participate in the NetworkAge.” Journal of Human Development 3 (2002): 95–122.Available online. URL: http://unpan1.un.org/intradoc/groups/public/documents/apcity/unpan014340.pdf. Accessed September11, 2007.One Laptop per Child. Available online. URL: http://laptop.org/vision/index.shtml. Accessed September 11, 2007.Wilson, Ernest J., III. The Information Revolution and DevelopingCountries. Cambridge, Mass.: MIT Press, 2004.Wireless Internet Institute. The Wireless Internet Opportunity forDeveloping Countries. Boston, Mass.: World Times, 2003.device driverA fundamental problem in computer design is the controlof devices such as disk drives and printers. Each deviceis designed to respond to a particular set of control commandssent as patterns of binary values through the portto which the device is connected. For example, a printerwill respond to a “new page” command by skipping linesto the end of the current page and moving the print headto the start of the next page, taking margin settings intoaccount. The problem is this: When an applications programsuch as a word processor needs to print a document,how should the necessary commands be provided to theprinter? If every application program has to include theappropriate set of commands for each device that might bein use, programs will be bloated and much developmenteffort will be required for supporting devices rather thanextending the functionality of the product itself. Instead,the manufacturers of printers and other devices such asscanners and graphics tablets typically provide a programcalled a driver. (A version of the driver is created for eachmajor operating system in use.) The driver serves as theintermediary between the application, the operating systemand the low-level device control system. It is sometimesuseful to have drivers in the form of continually runningprograms that monitor the status of a device and wait forcommands (see demon).Modern operating systems such as Microsoft Windowstypically take responsibility for services such as printingdocuments. When a printer is installed, its driver programis also installed in Windows. When the application programrequests to print a document, Windows’s print systemaccesses the driver. The driver turns the operating system’s“generic” commands into the specific hardware controlcommands needed for the device.While the use of drivers simplifies things for both programdevelopers and users, there remains the need for usersto occasionally update drivers because of an upgrade eitherin the operating system or in the support for device capabilities.Both Windows and the Macintosh operating system

Diffie, Bailey Whitfield 145DHTML See html, dhtml, and xhtml.Diffie, Bailey Whitfield(1944– )AmericanMathematician, Computer ScientistThe device driver is the link between the operating system andthe hardware that controls a specific device. Program requests arepassed by the operating system to the device driver, which issues thedetailed instructions needed by the device controller.implement a feature called plug and play. This allows for anewly installed device to be automatically detected by thesystem and the appropriate driver loaded into the operatingsystem (see plug and play). Other device managementcomponents enable the OS to keep track of the driver versionassociated with each device. Some of the newest operatingsystems include auto-update features that can search onthe Web for the latest driver versions and download them.The need to provide drivers for popular devices createssomething of a barrier to the development of new operatingsystems. In a catch-22, device manufacturers are unlikely tosupport a new OS that lacks significant market share, whilethe lack of device support in turn will discourage usersfrom adopting the new OS. (Users of the Linux operatingsystem faced this problem. However, that system’s opensource and cooperative development system made it easierfor enthusiasts to write and distribute drivers without waitingfor manufacturers to do so.)Further ReadingMr. Driver: Device Drivers. Available online. URL: http://www.mrdriver.com. Accessed July 8, 2007.Oney, Walter. Programming the Microsoft Windows Driver Manual.2nd ed. Redmond, Wash.: Microsoft Press, 2005.Rubini, Alessandro, and Jonathan Corbet. Linux Device Drivers.3rd ed. Sebastapol, Calif.: O’Reilly, 2005.Windows Driver Kit (WDK) Overview. Available online. URL:http://www.microsoft.com/whdc/devtools/wdk/default.mspx.Accessed July 8, 2007.Bailey Whitfield Diffie created the system of public keycryptography that many computer users depend on todayto protect their sensitive information (see encryption).Diffie was born on June 5, 1944, in the borough ofQueens, New York City. As a youngster he read about secretcodes and became fascinated. Although he was an indifferenthigh school student who barely qualified for graduation,Diffie scored so high on standardized tests that he wonadmission to the University of California, Berkeley, in 1962,where he studied mathematics for two years. However, in1964 he transferred to the Massachusetts Institute of Technology(MIT) and obtained his B.S. in mathematics in 1965.After graduation Diffie took a job at Mitre Corporation,a defense contractor, where he plunged into computer programming,helping create Mathlab, a program that allowedmathematicians to not merely calculate with a computer,but also to manipulate mathematical symbols to solve equations.(The program would eventually evolve into Macsyma,a software package used widely in the mathematical community—seemathematics software.)By the early 1970s Diffie had moved to the West Coast,working at the Stanford Artificial Intelligence Laboratory(SAIL), where he met Lawrence Roberts, head of informationprocessing research for ARPA, the Defense Department’sresearch agency. Roberts’s main project was thecreation of the ARPAnet, the computer network that wouldlater evolve into the Internet.Roberts was interested in providing security for the newnetwork, and (along with AI researcher John McCarthy)he helped revive Diffie’s dormant interest in cryptography.By 1974 Diffie had learned that IBM was developinga more secure cipher system, the DES (Data EncryptionStandard), under government supervision. However, Diffiesoon became frustrated with the way the National SecurityAgency (NSA) doled out or withheld information on cryptography,making independent research in the field verydifficult. Seeking to learn the state of the art, Diffie traveledwidely, seeking out people who might have fresh thoughtson the subject.Diffie found one such person in Martin Hellman, a Stanfordprofessor who had also been struggling on his own todevelop a better system of encryption. They decided to pooltheir ideas and efforts, and Diffie and Hellman came upwith a new approach, which would become known as publickey cryptography. It combined two important ideas thathad already been discovered to an extent by other researchers.The first idea was the “trap-door function”—a mathematicaloperation that can be easily performed “forward”but that was very hard to work “backward.” Diffie realized,however, that a trap-door function could be devised that

146 digital cashcould be worked backward easily if the person had theappropriate key.The second idea was that of key exchange. In classicalcryptography, there is a single key used for both encryptionand decryption. In such a case it is absolutely vital to keepthe key secret from any third party, so arrangements haveto be made in advance to transmit and protect the key.Diffie, however, was able to work out the theory for asystem that generates pairs of mathematically interrelatedkeys: a private key and a public key. Each participantpublishes his or her public key, but keeps the correspondingprivate key secret. If one wants to send an encryptedmessage to someone, one uses that person’s public key(obtained from the electronic equivalent of a phone directory).The resulting message can only be decrypted by theintended recipient, who uses the corresponding secret,private key.The public key system can also be used as a form of“digital signature” for verifying the authenticity of a message.Here a person creates a message encrypted with his orher private key. Since such a message can only be decryptedusing the corresponding public key, any other person canuse that key (together with a trusted third-party key service)to verify that the message really came from its purportedauthor.Diffie and Hellman’s 1976 paper in the IEEE Transactionson Information Theory began boldly with the statementthat “we stand today on the brink of a revolution in cryptography.”This paper soon came to the attention of threeresearchers who would create a practical implementationcalled RSA (for Rivest, Shamir, and Adelman).Through the 1980s Diffie, resisting urgent invitationsfrom the NSA, served as manager of secure systems researchfor the phone company Northern Telecom, designing systemsfor managing security keys for packet-switched datacommunications systems (such as the Internet).In 1991 Diffie was appointed Distinguished Engineerfor Sun Microsystems, a position that has left him free todeal with cryptography-related public policy issues. Thebest known of these issues has been the Clipper Chip, aproposal that all new computers be fitted with a hardwareencryption device that would include a “back door” thatwould allow the government to decrypt data. Along withmany civil libertarians and privacy activists, Diffie did notbelieve users should have to trust largely unaccountablegovernment agencies for the preservation of their privacy.Their opposition was strong enough to scuttle the ClipperChip proposal by the end of the 1990s. Another proposal,using public key cryptography but having a third-party“key escrow” agency hold the keys for possible criminalinvestigation, also fared poorly. In 1998 Diffie and SusanLandau wrote Privacy on the Line, a book about the politicsof surveillance and encryption. The book was revised andexpanded in 2007.Diffie has received a number of awards for both technicalexcellence and contributions to civil liberties. These includethe IEEE Information Theory Society Best Paper Award(1979), the IEEE Donald Fink Award (1981), the ElectronicFrontier Foundation Pioneer Award (1994), and even theNational Computer Systems Security Award (1996), given bythe NIST and NSA.Further ReadingDiffie, Whitfield. “Interview with Whitfield Diffie on the Developmentof Public Key Cryptography.” Conducted by FrancoFurger; edited by Arnd Weber, 1992. Available online. URL:http://www.itas.fzk.de/mahp/weber/diffie.htm. Accessed September12, 2007.Diffie, Whitfield, and Susan Landau. Privacy on the Line: the Politicsof Wiretapping and Encryption. Updated and expanded ed.Cambridge, Mass.: MIT Press, 2007.Kahn, David. The Codebreakers: The Story of Secret Writing. Reviseded. New York: Scribner, 1996.Levy, Steven. Crypto: How the Code Rebels Beat the Government:Saving Privacy in the Digital Age. New York: Viking Penguin,2001.digital cashAlso called digital money or e-cash, digital cash representsthe attempt to create a method of payment for online transactionsthat is as easy to use as the familiar bills and coinsin daily commerce (see e-commerce). At present, creditcards are the principal means of making online payments.While using credit cards takes advantage of a well-establishedinfrastructure, it has some disadvantages. From asecurity standpoint, each payment potentially exposes thepayer to the possibility that the credit card number andpossibly other identifying information will be diverted andused for fraudulent transactions and identity theft. Whilethe use of secure (encrypted) online sites has reduced thisrisk, it cannot be eliminated entirely (see computer crimeand security). Credit cards are also impracticable for verysmall payments from cents to a few dollars (such as foraccess to magazine articles) because the fees charged by thecredit card companies would be too high in relation to thevalue of the transaction.One way to reduce security concerns is to make transactionsthat are anonymous (like cash) but guaranteed.Products such as DigiCash and CyberCash allow users topurchase increments of a cash equivalent using their creditcards or bank transfers, creating a “digital wallet.” The usercan then go to any Web site that accepts the digital cash andmake a payment, which is deducted from the wallet. Themerchant can verify the authenticity of the cash throughits issuer. Since no credit card information is exchangedbetween consumer and merchant, there is no possibilityof compromising it. The lack of wide acceptance and standardshas thus far limited the usefulness of digital cash.The need to pay for small transactions can be handledthrough micropayments systems. For example, usersof a variety of online publications can establish accountsthrough a company called Qpass. When the user wants toread an article from the New York Times, for example, thefee for the article (typically $2–3) is charged against theuser’s Qpass account. The user receives one monthly creditcard billing from Qpass, which settles accounts with thepublications. Qpass, eCharge, and similar companies havehad modest success. A similar (and quite successful) serviceis offered by companies such as PayPal and Billpoint,

digital convergence 147which allow winning auction bidders to send money fromtheir credit card or bank account to the seller, who wouldnot otherwise be equipped to accept credit cards. Truemicropayments would extend down to just a few cents.“True” digital cash, allowing for anonymous paymentsand micropayments, has been slow to catch on. However,the successful digital cash system is likely to have the followingcharacteristics:• Protects the anonymity of the purchaser (no creditcard information transmitted to the seller)• Verifiable by the seller, perhaps by using one-timeencryption keys• The purchaser can create digital cash freely fromcredit cards or bank accounts• micropayments can be aggregated at a very low transactioncostAs use of digital cash becomes more widespread, it is likelythat tax and law enforcement agencies will press for theinclusion of some way to penetrate the anonymity of transactionsfor audit or investigation purposes. They will beopposed by civil libertarians and privacy advocates. Onelikely compromise may be requiring that transaction informationor encryption keys be deposited in some sort ofescrow agency, subject to being divulged upon court order.Further ReadingKou, Weidong. Payment Technologies for E-Commerce. New York:Springer, 2003.Lamb, Gregory M. “ ‘Nickel and Diming’ across the Internet.”Christian Science Monitor, February 23, 2004, n.p. Availableonline. URL: http://www.csmonitor.com/2004/0223/p13s01-wmgn.html. Accessed July 8, 2007.Orr, Bill. “Cashless Society, Ahoy! Suddenly Micropayments AreHot Again.” ABA Banking Journal 98 (March 2006): ff.Rosenborg, Victoria. PayPal for Dummies. Hoboken, N.J.: Wiley,2005.Warwick, David R. “Violent Crime and Cash: The Connection;Privacy Concerns About Digital Cash May Be Overblown.”The Futurist, May 1, 2007, p. 42.digital convergenceSince the late 20th century, many forms of communicationand information storage have been transformed from analogto digital representations (see analog and digital).For example, the phonograph record (an electromechanicalanalog format) gave way during the 1980s to a whollydigital format (see cd-rom). Video, too, is now increasinglybeing stored in digital form (DVD or laser disks) rather thanin the analog form of videotape. Voice telephony, whichoriginally involved the conversion of sound to analogouselectrical signals, is increasingly being digitized (as withmany cell phones) and transmitted in packet form over thecommunications network.The concept of digital convergence is an attempt toexplore the implications of so many formerly disparate analogmedia now being available in digital form. All forms ofdigital media have key features in common. First, they areDigital convergence results from the fact that many formerly analogmedia (such as sound, film, and video) are now being acquiredand processed digitally. Once in digital form, the content can beprocessed and played by a variety of software and used on manydifferent platforms ranging from desktop computers to electronicbooks (e-books) and portable MP3 music players. Content can alsobe linked and organized using hypertext or hypermedia techniques,as on the Web.essentially pure information (computer data). This meansthat regardless of whether the data originally representedstill images from a camera, video, or film, the sound of ahuman voice, music, or some other form of expression,that data can be stored, manipulated, and retrieved underthe control of computer algorithms. This makes it easierto create seamless multimedia presentations (see multimediaand hypertext and hypermedia). Services or productspreviously considered to be separate can be combined innew ways. For example, many radio stations now providetheir programming in the form of “streaming audio” thatcan be played by such utilities as RealPlayer or MicrosoftWindows Media Player (see streaming). Similarly, televisionnews services such as CNN can offer selected excerptsof their coverage in the form of streaming video files. Asmore users gain access to broadband Internet connections(such as cable or DSL), it is gradually becoming feasible todeliver TV programs and even full-length feature films indigital format. By the middle of the decade, media deliverybegan to proliferate on new platforms that representa further convergence of function. Many “smart phones”can play audio and video (see smartphone). In July 2007Apple’s iPhone entered the market, combining phone, mediaplayer, and Web browsing functions, and similar deviceswill no doubt follow (see also pda).Emerging IssuesThe merging of traditional media into a growing streamof digital content has created a number of difficult legaland social issues. Digital images or sounds from varioussources can easily be combined, filtered, edited, or otherwisealtered for a variety of purposes. As a result, the valueof photographs as evidence may be gradually compromised.

148 digital dashboardThe ownership and control of the intellectual property representedby music, video, and film has also been complicatedby the combination of digitization and the pervasiveInternet. For example, during 2000–2001 the legal battlesinvolving Napster, a program that allows users to sharemusic files pitted the rights of music producers and artiststo control the distribution of their product against the technologicalcapability of users to freely copy and distributethe material. While a variety of copy protection systems(both software and hardware-based) have been developedin an attempt to prevent unauthorized copying, historicallysuch measures have had only limited effectiveness(see copy protection, digital rights management, andintellectual property and computing).Digital convergence also raises deeper philosophicalissues. Musicians, artists, and scholars have frequently suggestedthat the process of digitization fails to capture subtletiesof performance that might have been accessible in theoriginal media. At the same time, the richness and immersivequalities of the new multimedia may be drawing peoplefurther away from the direct experience of the “real” analogworld around them. Ultimately, the embodiment of digitalconvergence in the form of virtual reality likely to emergein the early 21st century will pose questions as profound asthose provoked by the invention of printing and the developmentof mass broadcast media (see virtual reality).Further ReadingCovell, Andy. Digital Convergence: How the Merging of Computers,Communications and Multimedia Is Transforming Our Lives.Newport, R.I.: Aegis Publishing, 2000.———. Digital Convergence Phase 2: A Field Guide for Creator-Collaborators.Champaign, Ill.: Stipes Publishing, 2004Jenkins, Henry. Convergence Culture: Where Old and New MediaCollide. New York: New York University Press, 2006.Park, Sangin. Strategies and Policies in Digital Convergence. Hershey,Penn.: Information Science Reference, 2007.digital dashboardThe dashboard of a car is designed to present vital real-timeinformation to the driver, such as speed, fuel supply, andengine status. Ideally this information should be easy tograsp at a glance, allowing for prompt action when necessary.Conversely, unnecessary and potentially distractinginformation should be avoided, or at least relegated to anunobtrusive secondary display.A digital dashboard is a computer display that uses similarconcepts. Its goal is to provide an executive or managerwith the key information that allows him or her to monitorthe health of the enterprise and to take action when necessary.(A digital dashboard can also be part of a larger set ofmanagement tools—see decision support system.)The screen display for a digital dashboard can use avariety of objects (see graphical user interface). Thesecan include traditional charts (line, bar, or pie), color-codedmaps, depictions of gauges, and a variety of other interfaceelements sometimes known as “widgets.”However information is depicted, the dashboard isdesigned to summarize the current status of business orother functions, identify trends, and warn the user whenattention is required. For example, a dashboard mightsummarize production and shipping for each of a company’sfactories. Bars on a chart might be green when levelsare within normal parameters, but turn red if, for example,production has fallen more than 20 percent belowtarget goals. Dashboard displays can also be useful forgraphically showing the degree to which project objectivesare being met.Digital dashboards can be custom built or obtainedin forms specialized for various types of business. Typicallythe dashboard is hosted on the corporate Web serverand is accessible through Web browsers—perhaps with anabbreviated version that can be viewed on PDAs and smartphones.CritiqueToday dashboards are in widespread use in many top corporations,from Microsoft to Home Depot. An oft-citedadvantage of dashboard technology is that it keeps managersfocused and provides for quick response in situationswhere time may be crucial. No longer is it necessary for themanager to track down key individuals and try to makesense of their reports over the phone.Some critics, however, worry that dashboards may makemanagement too “data driven.” Those regular calls, afterall, can form an important part of the relationship betweenan executive or manager and subordinates, as well as gettinga sense of morale and possible personnel problems thatmay be affecting productivity. Overreliance on dashboardsand “bottom line” numbers may also hurt the morale ofsalespeople and others who come to feel that they are beingmicromanaged. Further, the dashboard may omit importantconsiderations that in turn are likely to receive less attentionand support.Further ReadingAnte, Spencer E., and Jena McGregor. “Giving the Boss the BigPicture: A ‘Dashboard’ Pulls Up Everything the CEO Needsto Run the Show.” BusinessWeek, February 13, 2006. Availableonline. URL: http://www.businessweek.com/magazine/content/06_07/b3971083.htm. Accessed September 12, 2007.Dashboard Examples. Available online. URL: http://www.enterprise-dashboard.com/. Accessed September 12, 2007.Dashboard Insight. Available online. URL: http://www.dashboardinsight.com/. Accessed September 12, 2007.Eckerson, Wayne W. Performance Dashboards: Measuring, Monitoring,and Managing Your Business. New York: Wiley, 2006.Few, Stephen. Information Dashboard Design: The Effective VisualCommunication of Data. Sebastapol, Calif.: O’Reilly, 2006.digital divideThe term digital divide was coined in the late 1990s amidgrowing concern that groups such as minorities, the elderly,and rural residents were not becoming computer literateand connecting to the Internet at the same rate as theyoung, educated, and relatively affluent.Nearly a decade later this perception of a chasm hasdiminished somewhat. According to the Pew Internet &American Life project, as of 2006 about two-thirds (70 per-

digital rights management 149cent) of American adults were using the Internet, and thenumber has continued to increase, though more slowly(there is evidence of a “hard core” unconnected population).Groups that lagged in Internet usage included Americans65 years or older (35 percent), African Americans (58percent), and persons without at least a high school education(36 percent).The digital divide is more severe if one looks at theworld as a whole (see developing nations and computing).Rapidly industrializing nations such as China andIndia are seeing considerable increases in the number ofpeople with some form of computer and Internet access,though the numbers are still small in relation to the totalpopulation. In severely underdeveloped countries (such asmany in Africa), connectivity may be improved by the “OneLaptop per Child” project, which has designed a prototypecomputer designed to cost less than $100.Broadband UseNot all Internet access is equal. High-speed connections(see broadband, cable modem, and dsl) encourage frequentInternet use throughout the day, and make it feasibleto access and share rich media (images, videos, podcasts,and so on). According to the Pew Internet & American Lifeproject, 47 percent of all adult Americans had a broadbandInternet connection at home as of 2007. The rate of broadbandadoption continues to lag for rural residents (31 percent)and African Americans (40 percent).However, the broadband adoption rate for AfricanAmericans has been increasing rapidly (it was only 14 percentin early 2005). There are a number of factors that correlatewith the likelihood that a person or community willhave access to the Web. People in lower-income bracketsare less likely to own PCs. Phone service may be less reliable(particularly in rural areas), and Internet access mayrequire expensive toll charges. While schools and publiclibraries can offer an alternative venue for Internet access,inner-city schools have tended to lag behind in connectingto the Internet and in the ratio of networked computers tostudents. (The Net Day activities in the mid-1990s first publicizedand sought to ameliorate this problem.)Internet access also correlates to education. While personslacking a college education are likely to be poorer thancollege graduates, they are also less likely to be workingin jobs that include regular computer access. A deficiencyin basic reading and keyboard skills can also serve as abarrier to participation in the online world (see also computerliteracy). People over age 50 are also less likely tobe online. They are more likely to have spent their career innoncomputerized jobs and may feel that they cannot masterthe new technology.Targeted attempts to close the digital divide throughproviding more Internet access through schools and librariesare likely to continue to be successful. The marketplaceitself is perhaps making the biggest contribution, since theprice of an Internet-capable PC with a basic dial-up connectionis now around $400 plus about $10/month.Improvement in the teaching of general literacy as wellas technical skills in the K-12 schools is necessary if thenext generation is to be able to participate fully and equallyin the online world.Further ReadingCompaine, Benjamin M., ed. The Digital Divide: Facing a Crisis orCreating a Myth? Cambridge, Mass.: MIT Press, 2001.Digital Divide Network. Available online. URL: http://www.digitaldivide.net/. Accessed July 9, 2007.Norris, Pippa. Digital Divide: Civic Engagement, Information Poverty,and the Internet Worldwide. Cambridge, Mass.: CambridgeUniversity Press, 2001.Nulens, Gert. The Digital Divide in Developing Countries: Towardsan Information Society in Africa. Brussels: VUB Brussels UniversityPress, 2001.Pew Internet & American Life Project. “Digital Divisions.” Availableonline. URL: http://www.pewinternet.org/pdfs/PIP_Digital_Divisions_Oct_5_2005.pdf. Accessed July 9, 2007.———. “Home Broadband Adoption 2007.” Available online. URL:http://www.pewinternet.org/pdfs/PIP_Broadband%202007.pdf. Accessed July 9, 2007.digital rights management (DRM)By default, once information is digitized it is simply a patternof bits that can be easily copied within the same or adifferent medium, using a variety of software or the built-infacilities of the operating system. Of course the developmentof tape-recording technology in the mid-20th centuryalready made it possible to copy audio recordings, and thelater development of videotape and the VCR did the same forvideo. However, while analog copying techniques lose someaccuracy (or fidelity) with each generation of copying, digitalfiles can be copied exactly each time. It is equally easy toe-mail, upload, or otherwise distribute audio or video files.Legally, the creator of an original work can assert copyright—literally,the “right to copy” or to control when andhow the work is distributed. Digital rights management(DRM) refers to a variety of technologies that can be usedto enforce this right by making it at least difficult for thepurchaser of one copy of a work to copy and distribute it inturn. (Similar technologies have also been used to preventcopying of software, which is, after all, just another patternof bits—see copy protection and software piracy andcounterfeiting.)DRM for Film and VideoIn the mid-1990s, movies on DVD were protected using theContent Scrambling System (CSS). This proprietary formatwas licensed only for certain hardware and operating systems,but in 1999 an activist programmer released DeCSS, aprogram that could decode protected discs and allow themto be played on operating systems such as Linux, which hadnot been licensed. A similar story unfolded in 2007 whenhackers broke the Advanced Access Content System (AACS)that was used to protect the new high-definition HD DVDand Blu-Ray discs.Protecting MusicDRM has also been used on many audio CDs. Many consumerscomplained that their CD players (particularly when usedwith Windows PCs) were not compatible with the protected

150 Dijkstra, Edsger W.discs. A bigger controversy arose in 2005 when Sony beganto use DRM technology that (without notification) installeda rootkit (a kind of “back door” to the operating system) thatpotentially left systems open to attack. Facing public outcryand several lawsuits, Sony withdrew the DRM, which, ironically,was rather ineffective at preventing copying. By 2007music CD producers had concluded that DRM had morecosts than benefits, and such protection is no longer foundon audio CDs.Music distributed online is often protected by DRM.However, some services such as Apple iTunes now offer theoption of buying DRM-free music at a higher price. (Apple’sSteve Jobs has called upon the online music industry tocompletely eliminate DRM.)Legal and Other IssuesGenerally, the argument for DRM has been straightforward:If people can get something for free, they will not buy it.Content creators and publishers would go out of business.Organizations such as the Recording Institute Associationof America (RIAA) have aggressively sued college studentsand others accused of sharing copyrighted music or videoonline and successfully forced the best known file-sharingservice, Napster, to become a licensed music service (seefile-sharing and p2p networks).The principal legal means for enforcing DRM is the DigitalMillennium Copyright Act (DMCA), passed in 1998. Thelaw prohibits the production or dissemination of technology(software or hardware) that allows users to circumvent DRM.However, it has been difficult in practice to prevent the rapiddissemination of “cracks” for DRM over the Internet.There are also a number of legal arguments againstDRM. One is that it prevents certain actions allowed to consumersunder copyright law, such as making a backup copyof media that one has purchased (see intellectual propertyand computing). Also, because many DRM schemeswork only with Windows or Macintosh machines, users ofother operating systems (notably Linux) must “crack” DRMin order to be able to use the protected media. (Under thelaw, such action to promote “interoperability” is allowed,though not if the purpose is to facilitate illegal copying. Butlike most matters of intent, this can be hard to determine.)There have also been First Amendment issues. Althoughthe DMCA includes a “scholarly research” exception, somecryptography researchers have said that they have beeninhibited from publishing analysis of DRM for fear of legalprosecution.A number of activists and groups have opposed DRM,including open-source advocate Richard Stallman and theElectronic Frontier Foundation (see cyberspace advocacygroups). One of their efforts has been promotion of theFree Software Foundation’s General Public License (GPL3),which prohibits the use of DRM in products distributedunder that open-source license.Further ReadingDefective by Design: A Campaign of the Free Software Foundation.Available online. URL: http://defectivebydesign.org/.Accessed September 12, 2007.Electronic Frontier Foundation. Available online. URL: http://www.eff.org. Accessed September 12, 2007.May, Christopher. Digital Rights Management: The Problem ofExpanding Ownership Rights. Oxford, U.K.: Chandos, 2007.Motion Picture Association of America. Available online. URL:http://www.mpaa.org/. Accessed September 12, 2007.Recording Industry Association of America. Available online.URL: http://www.riaa.org/. Accessed September 12, 2007.Van Tassel, Joan. Digital Rights Management: Protecting and MonetizingContent. Burlington, Mass.: Focal Press, 2006.Zeng, Wenjun, Heather Yu, and Ching-Yung Lin. Multimedia SecurityTechnologies for Digital Rights Management. Burlington,Mass.: Academic Press, 2006.Dijkstra, Edsger W.(1930–2002)DutchComputer ScientistEdsger W. Dijkstra was born in Rotterdam, Netherlands,in 1930 into a scientific family (his mother was a mathematicianand his father was a chemist). He received anintensive and diverse intellectual training, studying Greek,Latin, several modern languages, biology, mathematics, andchemistry. While majoring in physics at the University ofLeiden in 1951, he attended a summer school at Cambridgethat kindled what soon became a major interest in programming.He continued this pursuit at the MathematicalCenter in Amsterdam in 1952 while finishing studies for hisEdsger Dijkstra’s ideas about structured programming helpeddevelop the field of software engineering, enabling programmersto organize and manage increasingly complex softwareprojects. (Department of Computer Sciences, UT Austin)

disabled persons and computing 151physics degree. At the time there were no degrees in computerscience; indeed, programming did not yet exist as anacademic discipline. Like most other computers of the time,the Mathematical Center’s ARMAC was custom-built. Withno high-level languages yet in use, programming requiredintimate familiarity with the machine’s architecture andlow-level instructions. Dijkstra soon found that he thrivedin such an environment.By 1956, Dijkstra had discovered an algorithm for findingthe shortest path between two points. He applied thealgorithm to the practical problem of designing electricalcircuits that used as little wire as possible, and generalizedit into a procedure for traversing treelike data structures.During the 1960s, Dijkstra began to explore the problemof communication and resource-sharing within computers.He developed the idea of a semaphore. Like therailroad signaling device that allows only one train at atime to pass through a single section of track, the programmingsemaphore provides mutual exclusion, ensuring thattwo processes don’t try to access the same memory or otherresource at the same time.Another problem Dijkstra tackled involved the sequencingof several processes that are accessing the sameresources. He found ways to avoid a deadlock situationwhere one process had part of what it needed but was stuckbecause the process holding the other needed resource wasin turn waiting for the first process to finish. His algorithmsfor allowing multiple processes (or processors) to take turnsgaining access to memory or other resources would becomefundamental for the design of new computing architectures.During the 1970s, Dijkstra immigrated to the UnitedStates, where he became a research fellow at Burroughs, oneof the major manufacturers of mainframe computers. Duringthis time he helped launch the “structured programming”movement. His paper “GO TO Considered Harmful”criticized the use of that unconditional “jump” instructionbecause it made programs hard to read and verify. Thenewer structured languages such as Pascal and C affirmedDijkstra’s belief in avoiding or discouraging such haphazardprogram flow (see structured programming).Dijkstra spent the last decades of his career as a professorof mathematics at the University of Texas at Austin,where he held the Schlumberger Centennial Chair inComputer Science. Dijkstra had some unusual quirks fora computer scientist. His papers were handwritten with afountain pen, and he did not even own a personal computeruntil late in life.In 1972 Dijkstra won the Association for ComputingMachinery’s Turing Award. After his death on August 6, 2002,in Nuenen, The Netherlands, the ACM renamed its award forpapers in distributed computing as the Dijkstra Prize.Perhaps Dijkstra’s greatest testament, however, is foundin the millions of lines of computer code that are betterorganized and easier to maintain because of the widespreadadoption of structured programming.Further ReadingDijkstra, Edsger Wybe. A Discipline of Programming. Upper SaddleRiver, N.J.: Prentice Hall, 1976.———. Selected Writings on Computing: A Personal Perspective. NewYork: Springer, 1982.———, and W. H. J. Feijen. A Method of Programming. Reading,Mass.: Addison-Wesley, 1988.Shasha, Dennis, and Cathy Lazere. Out of Their Minds: The Livesand Discoveries of 15 Great Computer Scientists. New York:Springer-Verlag, 1995.disabled persons and computingThe impact of the personal computer upon persons havingdisabilities involving sight, hearing, or movement hasbeen significant but mixed. Computers can help disabledpeople communicate and interact with their environment,better enabling them to work and live in the mainstream ofsociety. At the same time, changes in computer technologycan, if not ameliorated, exclude some disabled persons fromfuller participation in a society where computer access andskills are increasingly taken for granted.Computers as EnablersComputers can be very helpful to disabled persons. Withthe use of text-to-speech software, blind people can haveonline documents read to them. (With the aid of a scanner,printed materials can also be input and read aloud.)Persons with low vision can benefit from software thatcan present text in large fonts or magnify the contents ofthe screen. Text can also be printed (embossed) in Braille.Deaf or hearing-impaired persons can now use e-mail orinstant messaging software for much of their communicationneeds, largely replacing the older and more cumbersometeletype (TTY and TTD) systems. As people who haveseen presentations by physicist Stephen Hawking know,even quadriplegics who have only the use of head or fingermovements can input text and have it spoken by a voicesynthesizer. Further, advances in coupling eye movements(and even brain wave patterns) to computer systems androbotic extensions offer hope that even profoundly disabledpersons will be able to be more self-sufficient.ChallengesUnfortunately, changes in computer technology can alsocause problems for disabled persons. The most pervasiveproblem arose when text-based operating systems such asMS-DOS were replaced by systems such as Microsoft Windowsand the Macintosh that are based on graphic iconsand the manipulation of objects on the screen. While textcommands and output on the older system could be easilyturned into speech for the visually impaired, everything,even text, is actually graphics on a Windows system. Whileit is possible to have software “hook into” the operating systemto read text within Windows out loud, it is much moredifficult to provide an alternative way for a blind person tofind, click on, drag, or otherwise manipulate screen objects.Thus far, while Microsoft and other operating system developershave built some “accessibility” features such as screenmagnification into recent versions of their products, thereis no systematic, integrated facility that would allow a blindperson to have the same facility as a sighted person.

152 disaster planning and recoveryThe growth of the World Wide Web also poses problemsfor the visually impaired, since many Web pages relyon graphical buttons for navigation. Software plug-ins canprovide audio cues to help with screen navigation. WhileWeb browsers usually have some flexibility in setting thesize of displayed fonts, some newer features (such as cascadingstyle sheets) can remove control over font sizefrom the user.Because most computer systems today use graphicaluser interfaces, the failure to provide effective access may bedepriving blind and visually impaired persons of employmentopportunities. Meanwhile, the computer industry, educationalinstitutions, and workplaces face potential challenges underthe Americans with Disabilities Act (ADA), which requiresthat public and workplace facilities be made accessible tothe disabled. Some funding through the Technology-RelatedAssistance Act has been provided to states for promoting theuse of adaptive technology to improve accessibility.Further ReadingAdaptive Computer Products. Available online. URL: http://www.makoa.org/computers.htm. Accessed July 9, 2007.Better Living through Technology. Available online. URL: http://www.bltt.org/. Accessed July 9, 2007.Gnome [Linux]. Accessibility Project. Available online. URL:http://developer.gnome.org/projects/gap/. Accessed July 9,2007.Microsoft Accessibility. Available online. URL: http://www.microsoft.com/enable/default.aspx. Accessed July 9, 2007.Slatin, John M., and Sharron Rush. Maximum Accessibility: MakingYour Web Site More Usable for Everyone. Boston: Addison-Wesley Professional, 2003.Thatcher, Jim, et al. Web Accessibility: Web Standards and RegulatoryCompliance. New York: Springer, 2006.Vanderheiden, Gregg C. Making Software More Accessible for Peoplewith Disabilities. Collingdale, Penn.: Diane Pub. Co., 2004.disaster planning and recoveryMost businesses, government offices, or other organizationsare heavily dependent on having continuous access to theirdata and the hardware, network, and software necessary towork with it. Activities such as procurement (see supplychain management), inventory, order fulfillment, and customerlists are vital to day-to-day operations. Any disasterthat might disrupt these activities, whether natural (such asan earthquake or severe weather) or human-made (see computervirus and cyberterrorism), must be planned for.Such planning is often called “business continuity planning.”The most basic way to protect against data loss is tomaintain regular backups (see backup and archive systems).On-site backups can protect against hardware failure,and can consist of separate storage devices (see networkedstorage) or the use of redundant storage within the mainsystem itself (see raid). However, for protection against fireor other larger-scale disaster, it is also necessary to haveregular off-site backups, whether using a dedicated facilityor an online backup service.To protect against power failure or interruption, one ormore uninterruptible power supplies (UPS) can be used,and possibly a backup generator to deal with longer-termoutages. All equipment should also have surge protection toavoid damage from power fluctuations.Of course anything that can minimize the chance ofdisaster happening or the extent of its effects should also bepart of disaster planning. This can include structural reinforcement,physical security, firewalls and antivirus software,and fire alarms and suppression systems.Disaster PlanningDespite the best precautions, disasters will continue to happen.Organizations whose continued existence depends ontheir data and systems need to plan systematically how theyare going to respond to foreseeable risks, and how they aregoing to recover and resume operations. Planning for disastersinvolves the following general steps:• specify the potential costs and other impacts of loss ofdata or access• use that data to prioritize business functions or units• assess how well facilities are currently being protected• determine what additional hardware or services (suchas additional file servers, attached storage, or remotebackup) should be installed• develop a comprehensive recovery plan that specifiesprocedures for dealing with various types of disastersor extent of damage, and including immediateresponse, recovery or restoration of data, and resumptionof normal services• develop plans for communicating with customers,authorities, and the general public in the event of adisaster• specify the responsibilities of key personnel and providetraining in all procedures• arrange ahead of time for sources of supplies, additionalsupport staff, and so on• establish regular tests or drills to verify the effectivenessof the plan and to maintain the necessary skillsRecent natural disasters as well as the 9/11 terroristattacks have spurred many organizations to begin orenhance their disaster planning and recovery procedures.Further ReadingBenton, Dick. “Disaster Recovery: A Pragmatist’s Viewpoint.”Disaster Recovery Journal, Winter 2007, pp. 79–81. Availableonline. URL: http://www.drj.com/articles/win07/2001-16.pdf.Accessed September 13, 2007.Disaster Recovery Guide. Available online. URL: http://www.disasterrecovery-guide.com/.Accessed September 13, 2007.Disaster Recovery World: The Business Continuity Planning &Disaster Recovery Planning Directory. Available online. URL:http://www.disasterrecoveryworld.com/. Accessed September13, 2007.Snedaker, Susan. Business Continuity and Disaster Recovery Planningfor IT Professionals. Rockland, Md.: Syngress, 2007.Wallace, Michael. The Disaster Recovery Handbook: A Step-by-StepPlan to Ensure Business Continuity and Protect Vital Operations,Facilities, and Assets. New York: AMACOM, 2004.

distance education 153disk array See raid.distance educationDistance education (also called distance learning or virtuallearning) is the use of electronic information and communicationtechnology to link teachers and students withouttheir being together in a physical classroom.Distance education in the form of correspondenceschools or classes actually began as early as the mid-19thcentury with teaching of the Pitman Shorthand writingmethod. Later, correspondence classes became part ofChautauqua, a movement to educate the rural and urbanworking classes, taking advantage of the growing reach ofmail service through Rural Free Delivery. In correspondenceschools, each lesson is typically mailed to the student,who completes the required work and returns it forgrading. A certificate is awarded upon completion of courserequirements. A few universities (such as the University ofWisconsin) also began to offer correspondence programs.By the middle of the 20th century, radio and then televisionwas being used to bring lectures to students. Thisincreased the immediacy and spontaneity of teaching. Theinvention of videotape in the 1970s allowed leading teachersto create customized courses geared for different audiences.However, the ability of students to interact with teachersremained limited.In the 1960s computers also began to be used for education.One of the earliest and most innovative programswas PLATO (Programmed Logic for Automatic TeachingOperations), which began at the University of Illinois butwas later expanded to hundreds of networked terminals.PLATO in many ways pioneered the combining of text,graphics, and sound—what would later be called multimedia.PLATO also provided for early forms of both e-mail andcomputer bulletin boards.Meanwhile, with the development of ARPANET andeventually the Internet, a new platform became availablefor delivering instruction. By the mid-1990s, courses werebeing delivered via the Internet (see World Wide Web).Modern Distance EducationAs broadband Internet access becomes the norm, more Internet-basedlearning environments are taking advantage ofvideo conferencing technology, allowing teachers and studentsto interact face to face. This helps answer a commonobjection by critics that distance education cannot replicatethe personal and social dimensions of face-to-face education.Distance education technologies such as this Polycom video conferencing software enable teachers and students to see, talk, and interact witheach other. Here, Manhattan School of Music student Wu Jie of the Zukerman Performance Program demonstrates her violin technique toMaestro Zukerman. (Photo by Andrew Lepley for Business Wire via Getty Images)

154 distributed computingAnother way this objection is sometimes addressed by universitiesis by having a period of physical residency (perhapsa few weeks) as part of the semester.New platforms for distance education continue toemerge. Class content including lectures has been formattedfor delivery to mobile devices such as iPods (see pdaand smartphone). Another intriguing idea is to establishthe classroom within an existing virtual world, such asthe popular game Second Life (see online games.) Herestudents and teachers can meet “face to face” through theirvirtual embodiments (avatars). It seems only a matter oftime before entire universities will exist in such burgeoningalternative worlds.Further ReadingBates, A. W. (Tony). Technology, E-Learning and Distance Education.2nd ed. New York: Routledge, 2005.Distance Education at a Glance. University of Idaho. Availableonline. URL: http://www.uidaho.edu/eo/distglan. AccessedSeptember 13, 2007.Distance Learning. About.com. Available online. URL: http://distancelearn.about.com/. Accessed September 13, 2007.Moore, Michael Grahame, ed. Handbook of Distance Education. 2nded. Lawrence Mahwah, N.J.: Erlbaum, 2007.Peterson’s Online Degrees and Distance Learning Programs. Availableonline. URL: http://www.petersons.com/distancelearning/.Accessed September 13, 2007.Simonson, Michael, et al. Teaching and Learning at a Distance:Foundations of Distance Education. 3rd ed. Upper Saddle River,N.J.: Prentice Hall, 2005.distributed computingThis concept involves the creation of a software systemthat runs programs and stores data across a number of differentcomputers, an idea pervasive today. A simple formis the central computer (such as in a bank or credit cardcompany) with which thousands of terminals communicateto submit transactions. While this system is in some sensedistributed, it is not really decentralized. Most of the workis done by the central computer, which is not dependent onthe terminals for its own functioning. However, responsibilitiescan be more evenly apportioned between computers(see client-server computing).Today the World Wide Web is in a sense the world’slargest distributed computing system. Millions of documentsstored on hundreds of thousands of servers can beaccessed by millions of users’ Web browsers running ona variety of personal computers. While there are rules forspecifying addresses and creating and routing data packets(see Internet and tcp/ip), no one agency or computercomplex controls access to information or communication(such as e-mail).Elements of a Distributed Computing SystemThe term distributed computer system today generally refersto a more specific and coherent system such as a databasewhere data objects (such as records or views) can reside onany computer within the system. Distributed computer systemsgenerally have the following characteristics:• The system consists of a number of computers (sometimescalled nodes). The computers need not necessarilyuse the same type of hardware, though theygenerally use the same (or similar) operating systems.• Data consists of logical objects (such as databaserecords) that can be stored on disks connected toany computer in the system. The ability to movedata around allows the system to reduce bottlenecksin data flow or optimize speed by storing the mostfrequently used data in places from which it can beretrieved the most quickly.• A system of unique names specifies the location ofeach object. A familiar example is the DNS (DomainNaming System) that directs requests to Web pages.• Typically, there are many processes running concurrently(at the same time). Like data objects, processescan be allocated to particular processors to balancethe load. Processes can be further broken down intothreads (see concurrent programming). Thus, thesystem can adjust to changing conditions (for example,processing larger numbers of incoming transactionsduring the day versus performing batches of“housekeeping” tasks at night).• A remote procedure call facility enables processes onone computer to communicate with processes runningon a different computer.• In inter-process communication protocols specify theprocessing of “messages” that processes use to reportstatus or ask for resources. Message-passing can beasynchronous (not time-dependent, and analogousto mailing letters) or synchronous (with interactiveresponses, as in a conversation).• The capabilities of each object (and thus the messagesit can respond to or send) are defined in terms of aninterface and an implementation. The interface is likethe declaration in a conventional program: It definesthe types of data that can be received and the typesof data that will be returned to the calling process.The implementation is the code that specifies how theactual processing will be done. The hiding of implementationdetails within the object is characteristic ofobject-oriented programming (see class).• A distributed computing environment includes facilitiesfor managing objects dynamically. This includeslower-level functions such as copying, deleting, ormoving objects and systemwide capabilities to distributeobjects in such as way as to distribute theload on the system’s processors more evenly, to makebackup copies of objects (replication), and to reclaimand reorganize resources (such as memory or diskspace) that are no longer allocated to objects.Three widely used systems for distributed computingare Microsoft’s DCOM (Distributed Component ObjectModel), OMG’s Common Object Request Broker Architecture(see Microsoft .net and corba), and Sun’s Java/

DNS 155Remote Method Invocation (Java/RMI). While these implementationsare quite different in details, they provide mostof the elements and facilities summarized above.ApplicationsDistributed computing is particularly suited to applicationsthat require extensive computing resources and thatmay need to be scaled (smoothly enlarged) to accommodateincreasing needs (see grid computing). Examplesmight include large databases, intensive scientific computing,and cryptography. A particularly interesting exampleis SETI@home, which invites computer users to install aspecial screen saver that runs a distributed process duringthe computer’s idle time. The process analyzes radiotelescope data for correlations that might indicate receipt ofsignals from an extraterrestrial intelligence (see cooperativeprocessing).Besides being able to marshal very large amounts ofcomputing power, distributed systems offer improved faulttolerance. Because the system is decentralized, if a particularcomputer fails, its processes can be replaced byones running on other machines. Replication (copying) ofdata across a widely dispersed network can also provideimproved data recovery in the event of a disaster.Further ReadingFarley, Jim, and Mike Loukides. Java Distributed Computing. Sebastopol,Calif.: O’Reilly, 1998.Garg, Vijay K. Concurrent and Distributed Computing in Java. NewYork: Wiley, 2004.———. Elements of Distributed Computing. New York: Wiley,2002.Goff, Max K. Network Distributed Computing: Fitscapes and Fallacies.Upper Saddle River, N.J.: Prentice Hall, 2003.MacDonald, Matthew. Microsoft .NET Distributed Applications:Integrating XML Web Services and .NET Remoting. Redmond,Wash.: Microsoft Press, 2003.Obasanjo, Dare, and Sanjay Bhatia. “An Introduction to DistributedObject Technologies.” Available online. URL:http://www.25hoursaday.com/_IntroductionToDistributedComputing.html. Accessed February 1, 2008.Shan, Yen-Ping, Ralph H. Earle, and Marie A. Lenzi. EnterpriseComputing with Objects: from Client-Server Environments to theInternet. Reading, Mass.: Addison-Wesley, 1997.SETI@Home. Available online. URL: http://setiathome.ssl.berkeley.edu/. Accessed August 14, 2007.DNS (domain name system)The operation of the Internet requires that each participatingcomputer have a unique address to which data packetscan be routed (see Internet and tcp/ip). The DomainName System (DNS) provides alphabetical equivalents tothe numeric IP addresses, giving the now familiar-lookingWeb addresses (URLs), e-mail addresses, and so on.The system uses a set of “top-level” domains to categorizethese names. One set of domains is based on thenature of the sites involved, including: .com (commercial,corporate), .edu (educational institutions), .gov (government),.mil (military), .org (nonprofit organizations), .int(international organizations), .net (network service providers,and so on).The other set of top-level domains is based on the geographicallocation of the site. For example, .au (Australia),.fr (France), and .ca (Canada). (While the United States hasthe .us domain, it is generally omitted in practice, becausethe Internet was developed in the United States).ADAEAFAGAIALAMANAOAQARASATAUAWAZBABBBDBEBFBGBHBIBJBMBNBOBRBSBTBVBWBYBZCACCCFCGCHCICKCLCMCNCOCRINTERNET COUNTRY CODES(partial list)AndorraUnited Arab EmiratesAfghanistanAntigua and BarbudaAnguillaAlbaniaArmeniaNetherlands AntillesAngolaAntarcticaArgentinaAmerican SamoaAustriaAustraliaArubaAzerbaijanBosnia and HerzegovinaBarbadosBangladeshBelgiumBurkina FasoBulgariaBahrainBurundiBeninBermudaBrunei DarussalamBoliviaBrazilBahamasBhutanBouvet IslandBotswanaBelarusBelizeCanadaCocos (Keeling) IslandsCentral African RepublicCongoSwitzerlandCôte d’Ivoire (Ivory Coast)Cook IslandsChileCameroonChinaColombiaCosta Rica

156 DNSCSCUCVCXCYCZDEDJDKDMDODZECEEEGEHERESETFIFJFKFMFOFRFXGAGBGDGEGFGHGIGLGMGNGPGQGRGSGTGUGWGYHKHMHNHRHTHUIDIEILINIOIQCzechoslovakia (former)CubaCape VerdeChristmas IslandCyprusCzech RepublicGermanyDjiboutiDenmarkDominicaDominican RepublicAlgeriaEcuadorEstoniaEgyptWestern SaharaEritreaSpainEthiopiaFinlandFijiFalkland Islands (Malvinas)MicronesiaFaroe IslandsFranceFrance, MetropolitanGabonGreat Britain (UK)GrenadaGeorgiaFrench GuianaGhanaGibraltarGreenlandGambiaGuineaGuadeloupeEquatorial GuineaGreeceS. Georgia and S. Sandwich Isls.GuatemalaGuamGuinea-BissauGuyanaHong KongHeard and McDonald IslandsHondurasCroatia (Hrvatska)HaitiHungaryIndonesiaIrelandIsraelIndiaBritish Indian Ocean TerritoryIraqIRISITJMJOJPKEKGKHKIKMKNKPKRKWKYKZLALBLCLILKLRLSLTLULVLYMAMCMDMGMHMKMLMMMNMOMPMQMRMSMTMUMVMWMXMYMZNANCNENFNGNINLIranIcelandItalyJamaicaJordanJapanKenyaKyrgyzstanCambodiaKiribatiComorosSaint Kitts and NevisKorea (North)Korea (South)KuwaitCayman IslandsKazakhstanLaosLebanonSaint LuciaLiechtensteinSri LankaLiberiaLesothoLithuaniaLuxembourgLatviaLibyaMoroccoMonacoMoldovaMadagascarMarshall IslandsMacedoniaMaliMyanmarMongoliaMacauNorthern Mariana IslandsMartiniqueMauritaniaMontserratMaltaMauritiusMaldivesMalawiMexicoMalaysiaMozambiqueNamibiaNew CaledoniaNigerNorfolk IslandNigeriaNicaraguaNetherlands

DNS 157NONPNRNTNUNZOMPAPEPFPGPHPKPLPMPNPRPTPWPYQARERORURWSASBSCSDSESGSHSISJSKSLSMSNSOSRSTSUSVSYSZTCTDTFTGTHTJTKTMTNTOTPNorwayNepalNauruNeutral ZoneNiueNew Zealand (Aotearoa)OmanPanamaPeruFrench PolynesiaPapua New GuineaPhilippinesPakistanPolandSt. Pierre and MiquelonPitcairnPuerto RicoPortugalPalauParaguayQatarReunionRomaniaRussian FederationRwandaSaudi ArabiaSolomon IslandsSeychellesSudanSwedenSingaporeSt. HelenaSloveniaSvalbard and Jan Mayen IslandsSlovak RepublicSierra LeoneSan MarinoSenegalSomaliaSurinameSao Tome and PrincipeUSSR (former)El SalvadorSyriaSwazilandTurks and Caicos IslandsChadFrench Southern TerritoriesTogoThailandTajikistanTokelauTurkmenistanTunisiaTongaEast TimorTRTTTVTWTZUAUGUKUMUSUYUZVAVCVEVGVIVNVUWFWSYEYTYUZAZMZRZWTurkeyTrinidad and TobagoTuvaluTaiwanTanzaniaUkraineUgandaUnited KingdomUS Minor Outlying IslandsUnited StatesUruguayUzbekistanVatican City State (Holy See)Saint Vincent and the GrenadinesVenezuelaVirgin Islands (British)Virgin Islands (U.S.)Viet NamVanuatuWallis and Futuna IslandsSamoaYemenMayotteYugoslaviaSouth AfricaZambiaZaireZimbabweDomains and AddressesA complete Internet address generally consists of a wordrepresenting the name of the organization or company, possiblyfollowed by the name of a department or division.This is followed by the top-level domain. Here are someexamples:well.com The Well conferencing system, a business in theU.S.acm.org The Association for Computing Machinery, a nonprofitprofessional organizationstate.gov United States Department of Stateberkeley.edu University of California, Berkeleywww2.physics.ox.ac.uk Department of Physics, Oxford University,Oxfordshire, United Kingdom.To access a service at a given site, the host address is prefixedto indicate the server or service. Most commonly, thisis www for World Wide Web. Thus www.well.com indicatesthe Web server at the well.com host, while ftp.well.comwould indicate the ftp (file transfer protocol) server. (Insome cases, if there is no prefix, www will be assumed.)A complete Web address or URL (Uniform ResourceLocator) also includes a prefix for the protocol to be used(see World Wide Web). Most commonly this is http:// (forhypertext transfer protocol), though most Web browsers

158 documentation of program codewill treat this as the default and not require that it be typed.ftp:// can be used to access ftp servers via the Web. Finally,a URL must include the path to the directory that actuallycontains the HTML document or other resource, as wellas its filename. Thus a complete address for a hypotheticaluser’s home page might be:http://www.BigUniversity.edu/users/tomr/index.htmlInternal AddressingWhen a Web user types such an address, the Web browserconnects to a nearby name server. This program translatesthe name into an IP (Internet Protocol) address. Theaddress consists of four 8-bit numbers called tuples, separatedby periods. For example, the domain name www.well.com currently translates to 208.178.101.2. The first numberrepresents one of five classes of networks, with thefirst three classes (A-C) organized according to the numberand size of networks and D and E being reserved for oneto-many“broadcast” transmissions and experimentationrespectively.To obtain a domain name, a person or organizationcontacts one of several registration services accredited byICANN (the nonprofit Internet Corporation for assignedNames and Numbers). Each name must be unique. Considerablelegal disputation has occurred when someonenot connected with a company has registered a domaincontaining that company’s name. The tremendous growthof e-commerce has made distinctive or easy-to-rememberdomain names a scarce and valuable commodity. Foreseeingthis, some speculators bought up attractive domains inthe hope (sometimes realized) of selling them to corporationsat a huge profit. Anti–“domain squatting” laws werepassed in reaction. In other cases, disgruntled employees orconsumers have registered domains for Web sites critical ofmajor corporations such as airlines and telephone companies.In the courts, this pits the right of free speech againstthe right of a company to control the use of its name.Expanding the SystemThe expansion of the Internet has strained the capacity ofthe existing DNS. The shortage of “name space” is beingaddressed by the release of IP Version 6, which replaces the32-bit addresses with 128-bit ones. In addition, in November2000 ICANN announced the creation of seven new topleveldomains: .aero (air transport), .biz (business), .coop(cooperatives), .info (general-purpose), .museum (museums),.name (personal sites), and .pro (professionals suchas lawyers, accountants, and physicians). However, the situationis muddled by the existence of competing proposalsand the use of unofficial DNS systems that provide theirown domains (but require special software for access, sincethey are not recognized by regular DNS servers).Perhaps a more fundamental issue is the adopting ofa system designed by English speakers to a world thatincreasingly seeks international access and standards (seeinternationalization). The problem is how to meet localneeds without creating new barriers through incompatibleaddressing schemes. The proposal being implemented as ofthe mid-2000s is called Internationalizing Domain Namesin Applications (IDNA). This standard includes an algorithmby which address labels written using the many charactersets and diacritical marks in the world’s languages(as rendered in Unicode) can be translated to the standardASCII characters used by the existing DNS (see charactersand strings).Further ReadingAlbitz, Paul, and Cricket Liu. DNS and BIND, 4th ed. Sebastopol,Calif.: O’Reilly, 2001.ICANN (Internet Corporation for Assigned Names and Numbers).Available online. URL: http://www.icann.org/. AccessedAugust 14, 2007.“Internationalization of Domain Names: A History of Technology.”Internet Society. www.isoc.org/pubpolpillar/docs/i18n-dnschronology.pdf.Accessed July 10, 2007.InterNIC. Available online. URL: http://www.internic.net/. AccessedAugust 14, 2007.InterNIC Registry WhoIs [domain look-up]. Available online.URL: http://www.internic.net/whois.html. Accessed August14, 2007.documentation of program codeComputer system documentation can be divided into twomain categories based upon the intended audience. Manualsand training materials for users focus on explaininghow to use the program’s features to meet the user’s needs(see documentation, user). This entry, however, focuseson the creation of documentation for programmers and othersinvolved in software development and maintenance (seealso technical writing).Software documentation can consist of commentsdescribing the operation of a line or section of code. Earlyprogramming with its reliance on punched cards had onlyminimal facilities for incorporating comments. (Some of theproponents of COBOL thought that the language’s Englishlikesyntax would make additional documentation unnecessary.Like the similar claim that trained programmerswould no longer be needed, the reality proved otherwise.)After the switch from punchcard input to the use ofkeyboards, adding comments became easier. For example, acomment in C looks like this:printf(“Hello, world\n”);/* Display the traditional message */while C++ uses comments in this form:cout

documentation, user 159In addition to the commented source code, externaldocumentation is usually provided. Design documents canrange from simple flowcharts or outlines to detailed specificationsof the program’s purpose, structure, and operations.Rather than being considered an afterthought, documentationhas been increasingly integrated into the practice ofsoftware engineering and the software development process.This practice became more prevalent during the 1960s and1970s when it became clear that programs were not onlybecoming larger and more complex, but also that significantprograms such as business accounting and inventory applicationswere likely to have to be maintained or revised forperhaps decades to come. (The lack of adequate documentationof date-related code in programs of this vintage becamean acute problem in the late 1990s. See y2k problem.)Documentation ToolsAs programmers began to look toward developing theircraft into a more comprehensive discipline, advocates ofstructured programming placed an increased emphasis notonly on proper commenting of code but on the developmentof tools that could automatically create certain kindsof documentation from the source code. For example, thereare utilities for C, C++, and Java (javadoc) that will extractinformation about class declarations or interfaces and formatthem into tables. Most software development environmentsnow include features that cross-reference “symbols”(named variables and other objects). The combination ofcomments and automatically generated documentation canhelp with maintaining the program as well as being helpfulfor creating developer and user manuals.While programmers retain considerable responsibilityfor coding standards and documentation, larger programmingstaffs typically have specialists who devote their fulltime to maintaining documentation. This includes the loggingof all program change requests and the resulting newdistributions or “patches,” the record of testing and retestingof program functions, the maintenance of a “versionhistory,” and coordinating with technical writers in theproduction of revised manuals.Further ReadingBarker, Thomas T. Writing Software Documentation: A Task-OrientedApproach. 2nd ed. New York: Longman, 2002.Goodliffe, Pete. Code Craft: The Practice of Writing Excellent Code.San Francisco: No Starch Press, 2007.Knuth, Donald E. Literate Programming. Stanford, Calif.: Centerfor the Study of Language and Information, 1992.Rüping, Andreas. Agile Documentation: A Pattern Guide to ProducingLightweight Documents for Software Projects. Hoboken,N.J.: Wiley, 2003.Society for Technical Communication. Available online. URL:http://www.stc.org/. Accessed July 9, 2007.documentation, userAs computing moved into the mainstream of offices andschools beginning in the 1980s and accelerating throughthe 1990s, the need to train millions of new computer usersspawned the technical publishing industry. In addition tothe manual that accompanied the software, third-partypublishers produced full-length books for beginners andadvanced users as well as “dictionaries” and reference manuals(see also technical writing). A popular program suchas WordPerfect or (today) Adobe Photoshop can easily fillseveral shelves in the computer section of a large bookstore.A number of publishers targeted particular audiencesand adopted distinctive styles. Perhaps the best known isthe IDG “Dummies” series, which eventually diversified itsofferings from computer-related titles to everything fromhome remodeling to investing. Berkeley, California, publisherPeachpit Press created particularly accessible introductionsfor Windows and Macintosh users. At the otherend of the spectrum, publishers Sams, Osborne, WaiteGroup, and Coriolis targeted the developer and “poweruser” community and the eclectic, erudite volumes fromO’Reilly grace the bookshelves of many UNIX users.Online DocumentationDuring the 1980s, the lack of a multitasking, window-basedoperating system limited the ability of programs to offerbuilt-in (or “online”) documentation. Traditionally, userscould press the F1 key to see a screen listing key commandsand other rudimentary help. However, both the Macintoshand Windows-based systems of the 1990s includedthe ability to incorporate a standardized, hypertext-basedhelp system in any program. Users could now search forhelp on various topics and scroll through it while keepingtheir main document in view. Another facility, the “wizard,”offered the ability to guide users step by step througha procedure.The growth of the use of the Web has provided a new avenuefor online help. Today many programs link users to theirWeb site for additional help. Even help files stored on theuser’s own hard drive are increasingly formatted in HTMLfor display through a Web browser. Additional sources ofhelp for some programs include training videos and animatedpresentations using programs such as PowerPoint.By the late 1990s, printed user manuals were becoming aless common component in software packages. (Instead, themanual was often provided as a file in the Adobe Acrobatformat, which reproduces the exact appearance of printedmaterial on the screen.) The computer trade book industryhas also declined somewhat, but the bookstore still offersplenty of alternatives for users who are more comfortablewith printed documentation.Further ReadingCasabona, Helen. “From Good to Great—The Finer Points of WritingUser Documentation.” www.stc.org/confproceed/1995/PDFs/PG437440.PDF. Accessed July 9, 2007.“How to Publish a Great User Manual.” Available online. URL:http://www.asktog.com/columns/017ManualWriting.html.Accessed July 9, 2007.Kukulska-Hulme, Agnes. Language and Communication: EssentialConcepts for User Interface and Documentation Design. NewYork: Oxford University Press, 1999.Online Technical Writing [textbook]. Available online. URL: http://www.io.com/~hcexres/textbook/acctoc.html. Accessed July 9,2007.

160 document modelSociety for Technical Communication. Available online. URL:http://www.stc.org/. Accessed July 9, 2007.document modelMost early developers and users of desktop computing systemsthought in terms of application programs rather thanfocusing on the documents or other products being createdwith them. From the application point of view, filesare opened or created, content (text or graphics) is created,and the file is then saved. There is no connection betweenthe files except in the mind of the user. The dominant wordprocessors of the 1980s (such as WordStar and WordPerfect)were designed as replacements for the typewriter andemphasized the efficient creation of text (see word processing).Users who wanted to work with other types ofinformation had to run completely separate applications,such as dBase for databases or Lotus 1-2-3 for spreadsheets.Working with graphics images (to the extent it was possiblewith early PCs) required still other programs.This “application-centric” way of thinking suited programdevelopers at a time when most computer systems(such as those running MS-DOS) could run only one programat a time. But increasing processor power, memory,and graphics display capabilities during the late 1980s madeit possible to create an operating system such as MicrosoftWindows that could display text fonts and formatting,graphics and other content in the same window, and runseveral different program windows at the same time (seemultitasking). In turn, this made it possible to present amodel that was more in keeping with the way people hadworked in the precomputer era.In the new “document model,” instead of thinking interms of individual application programs working withfiles, users could think in terms of creating documents.A document (such as a brochure or report) could containformatted text, graphics, and data brought in from databaseor spreadsheet programs. This meant that in the course ofworking with a document users would actually be invokingthe services of several programs: a word processor, graphicseditor, database, spreadsheet, and perhaps others. To theuser, however, the focus would be on a screen “desktop” onwhich would be arranged documents (or projects), not onthe process of running individual programs and loadingfiles.Implementing the Document ModelThere are two basic approaches to maintaining documents.One is to create large programs that provide all of the featuresneeded, including word processing, graphics, and datamanagement (see application suite). While such tightintegration can (ideally at least) create a seamless workingenvironment with a consistent user interface, it lacksflexibility. If a user needs capabilities not included in thesuite (such as, perhaps the ability to create an HTML versionof the document for the Web), one of two cumbersomeprocedures would have to be followed. Either the operatingsystem’s “cut and paste” facilities might be used to copydata from another application into the document (possiblywith formatting or other information lost in the process),or possibly the document could be saved in a file formatthat could be read by the program that was to provide theadditional functionality (again with the possibility of losingsomething in the translation).Linking and EmbeddingA more sophisticated approach is to create a protocol thatapplications could use to call upon one another’s services.The Windows COM (Component Object Model) uses a technologyformerly called OLE (Object Linking and Embedding).Using this facility, someone working on a documentin Microsoft Word could “embed” another object such asan Excel spreadsheet or an Access database into the currentdocument (which becomes the container). When theuser double-clicks on the embedded object, the appropriateapplication is launched automatically, and the user sees thescreen menus and controls from that application instead ofthose in Word. (One can also think of Word in this examplebeing the client and Excel or Access as the server—see client-servercomputing). All work done with the embeddedobject is automatically updated by the server applicationand everything is stored in the same document file. Alternatively,an application may be linked rather than embedded.In that case, the container document simply containsa pointer to the file in the other application. Wheneverthat file is changed, all documents that are linked to it areupdated. Object embedding thus preserves a document-centricapproach but works with any applications that supportthat facility, regardless of vendor. The Macintosh operatingsystem offers a similar facility. Apple and IBM attemptedunsuccessfully to create a competing standard called Open-Doc. This should not be confused with the more recentOpen Document standard from the popular open-sourceapplication Open Office. Meanwhile Microsoft’s COM, graduallyintroduced during the later 1990s, has been largelysuperseded by .NET (see Microsoft .NET). This reflectsa shift in emphasis from a document model (within a sin-The Document Object Model (DOM) treats a Web page as an objectthat can be manipulated using a variety of scripting languages.

Dreyfus, Hubert 161gle computer) to a more comprehensive “network objectmodel.”Document and object models are also increasinglyimportant for working on the Web. This can be seen inthe increasing use of XML documents and the DocumentObject Model (see xml and dom). This involves the use of aconsistent programming interface (see api) by which manyapplications can create or process XML documents for datacommunication or display.Further ReadingBornestein, Niel M. .NET and XML. Sebastapol, Calif.: O’ReillyMedia, 2003.“Document Object Model (DOM).” World Wide Web Consortium.Available online. URL: http://www.w3.org/DOM/. AccessedAugust 12, 2007.Lowry, Juval. Programming .NET Components. 2nd ed. Sebastapol,Calif.: O’Reilly Media, 2005.“Open Document Format for Office Applications: OASIS Standard.”Available online. URL: http://docs.oasis-open.org/office/v1.0. Accessed July 10, 2007.DOM (Document Object Model)The Document Object Model (DOM) is a way to representa Web document (see html and xml) as an object thatcan be manipulated using code in a scripting language (seeJavaScript). The DOM was created by the World Wide WebConsortium (W3C) as a way to standardize methods ofmanipulating Web pages at a time when different browsersused different access models. The full specification isdivided into four levels (0 through 3). By 2005, most DOMspecifications were supported by the major Web browsers.Using DOM, a programmer can navigate through thehierarchical structure of a document, following links or“descending” into forms and user-interface objects. WithDOM one can also add HTML or XML elements, as well asload, save, or format documents.Code can also be written to respond to a number of“events,” including user keyboard or mouse activity andinteractions with specific user-interface elements andHTML forms. For example, the “mouseover” event will betriggered when the user moves the mouse cursor over adefined region. The code can then perform an action suchas popping up a box with explanatory text. The “submit”event will be triggered when the user has finished fillingin a form and clicked the button to send it to the Website. When an event occurs, the event object is used topass detailed information about it to the program, such aswhich key or button was pressed, the location of the mousepointer, and so on.Although learning the DOM methods and how to usethem takes some time, and familiarity with JavaScript ishelpful, the syntax for accessing DOM methods should befamiliar to anyone who has used an object-oriented programminglanguage. Here are some simple sample statements.Get the document with the specified ID:document.getElementById(ID)Get the element with the specified tag:document.getElementByTagName(tagname)Get the specified attribute (property) ofthe specified element:myElement.getAttribute(attributeName)Create an element with the specified tag andreference it through a variable:var myElementNode = document.createElement(tagname)EvaluationAlthough dynamic HTML (DHTML) also has an objectmodel that can be used to access and manipulate individualelements, DOM is more comprehensive because it providesaccess to the document as a whole and the ability to navigatethrough its structure.By providing a uniform way to manipulate documents,DOM makes it easier to write tools to process them in aseries of steps. For example, database programs and XMLparsers can produce DOM document “trees” as output, andan XSLT (XML style sheet processor) can then be used toformat the final output.For working with XML, another popular alternative isthe Simple API for XML (SAX). The SAX model is quite differentfrom DOM in that the former “sees” a document asa stream of events (such as element nodes) and the parseris programmed to call methods as events are encountered.DOM, on the other hand, is not a stream but a tree that canbe entered arbitrarily and traversed in any direction. Onthe other hand, SAX streams do not require that the entiredocument be held in memory, and processing can sometimesbe faster.Further ReadingDocument Object Model FAQ. World Wide Web Consortium.Available online. URL: http://www.w3.org/DOM/faq.html.Accessed September 16, 2007.Heilmann, Christian. Beginning JavaScript with DOM Scripting andAjax: From Novice to Professional. Berkeley, Calif.: APress, 2006.Keith, Jeremy. DOM Scripting: Web Design with JavaScript and theDocument Object Model. Berkeley, Calif.: APress, 2005.Robie, Jonathan. “What Is the Document Object Model?” WorldWide Web Consortium. Available online. URL: http://www.w3.org/TR/WD-DOM/introduction.html. Accessed September14, 2007.Sambells, Jeffrey, and Aaron Gustafson. Advanced DOM Scripting:Dynamic Web Design Techniques. Berkeley, Calif.: APress,2007.DOS See ms-dos.Dreyfus, Hubert(1929– )AmericanPhilosopher, Cognitive PsychologistAs the possibilities for computers going beyond “numbercrunching” to sophisticated information processing becameclear starting in the 1950s, the quest to achieve artificial intelligence(AI) was eagerly embraced by a number of innovative

162 DRMresearchers. For example, Allen Newell, Herbert Simon, andCliff Shaw at the RAND Corporation, attempted to writeprograms that could “understand” and intelligently manipulatesymbols rather than just literal numbers or characters.Similarly, MIT’s Marvin Minsky (see Minsky, Marvin) wasattempting to build a robot that could not only perceive itsenvironment, but in some sense understand and manipulateit. (See artificial intelligence and robotics.)Into this milieu came Hubert Dreyfus, who had earnedhis Ph.D. in philosophy at Harvard. Dreyfus had specializedin the philosophy of perception (how meaning can bederived from a person’s environment) and phenomenology(the understanding of processes). When Dreyfus began toteach a survey course on these areas of philosophy, someof his students asked him what he thought of the artificialintelligence researchers who were taking an experimentaland engineering approach to the same topics the philosophershad discussed abstractly.Philosophy had attempted to explain the process of perceptionand understanding (see also cognitive science).One tradition, the rationalism represented by such thinkersas Descartes, Kant, and Husserl took the approach offormalism and attempted to elucidate rules governing theprocess. They argued that in effect the human mind was amachine (albeit a wonderfully complex and versatile one).The opposing tradition, represented by the phenomenologistsWittgenstein, Heidegger, and Merleau-Ponty, took aholistic approach in which physical states, emotions, andexperience were inextricably intertwined in creating theworld that people perceive and relate to.If computers, which at that time had only the mostrudimentary “senses” and no emotions could perceive andunderstand in the way humans did, then the rules-basedapproach of the rationalist philosophers would be vindicated.But when Dreyfus had examined the AI efforts, hewrote a paper titled “Alchemy and Artificial Intelligence.”His comparison of AI to alchemy was provocative in that itsuggested that like the alchemists, the modern AI researchershad met with only limited success in manipulatingtheir materials (such as by teaching computers to performsuch intellectual tasks as playing checkers and even provingmathematical theorems). However, Dreyfus concludedthat the kind of flexible, intuitive, and ultimately robustintelligence that characterizes the human mind couldn’t bematched by any programmed system. Each time AI researchersdemonstrated the performance of some complex task,Dreyfus examined the performance and concluded that itlacked the essential characteristics of human intelligence.Dreyfus expanded his paper into the book What ComputersCan’t Do. Meanwhile, critics complained that Dreyfus wasmoving the goal posts after each play, on the assumptionthat “if a computer did it, it must not be true intelligence.”Two decades later, Dreyfus reaffirmed his conclusions inWhat Computers Still Can’t Do, while acknowledging that theAI field had become considerably more sophisticated in creatingsystems of emergent behavior (such as neural networks).Currently a professor in the Graduate School of Philosophyat the University of California, Berkeley, Dreyfuscontinues his work in pure philosophy (including a commentaryon phenomenologist philosopher Martin Heidegger’sBeing and Time) while still keeping an eye on thecomputer world in his latest publication, On the Internet.Further ReadingDreyfus, Hubert. What Computers Can’t Do: A Critique of ArtificialReason. New York: Harper and Row, 1972.———. What Computers Still Can’t Do. Cambridge, Mass.: MITPress, 1992.Dreyfus, Hubert, and Stuart Dreyfus. Mind over Machine: the Powerof Human Intuitive Expertise in the Era of the Computer. Rev.ed. New York: Free Press, 1988.Henderson, Harry. Artificial Intelligence: Mirrors for the Mind. NewYork: Chelsea House, 2007.DRM See digital rights management.DSL (digital subscriber line)DSL (digital subscriber line) is one of the two most prevalentforms of high-speed wired access to the Internet (seebroadband and cable modem). DSL can operate overregular phone lines (sometimes called POTS or “plainold telephone service”). DSL takes advantage of the factthat existing phone lines can carry frequencies far beyondthe narrow band used for voice telephony. When installingDSL, the phone company must evaluate the quality ofexisting lines to determine how many frequency bands areusable, and thus how much data can be transmitted. Further,because the higher the frequency the shorter the distancethe signal can travel, the available bandwidth dropsas one gets farther from the central office or a local DSLaccess Multiplexer (DSLAM).Typical DSL services can range in speed from 128 kbpsto 3 Mbps. Many providers offer higher speeds at additionalcost. Speeds quoted are generally maximums; actual speedmay be less due to poor line quality or greater distancefrom the central office.The most common form of DSL is ADSL (asymmetricDSL), which has much higher download speeds than uploadspeeds. This is generally not a problem, since most usersconsume much more content than they generate. The lowerfrequencies are generally reserved for regular voice and faxservice. A single DSL modem can serve multiple users in alocal network by being connected to a router.As more people move from land-line phone service tocellular, there has been greater demand for offering socallednaked DSL—DSL without traditional phone service.DSL can also be provided over optical fiber (see fiberoptics).Note that an older and lower-bandwidth version of thetechnology called ISDN (Integrated Services Digital Network)is still in use, but has largely been superseded byDSL/ADSL.Alternatives to DSLCable is still more popular than DSL, though the latter hasclosed the gap somewhat. The fact that the two services canboth provide fast Internet access (mostly) through existing

DVR 163DSL uses special modems to convert between computer data and signals that can travel over ordinary phone lines. This technology is widelyused to provide broadband Internet access.infrastructure has created considerable competition. Thusa cable provider can now offer telephone service via theInternet (see voip) at the same time a phone provider usingDSL can offer movies and television programming streamedover the network. The fact that in many locations DSL andcable providers are in competition can result in lower ratesor more attractive “bundles” of services for consumers.On average, cable modem speeds are somewhat fasterthan DSL; however, cable speeds can degrade as more usersare added to a circuit. Although both services have had theirshare of glitches, they now both tend to be quite reliable.Further ReadingGolden, Philip, Herve Dedieu, and Krista S. Jacobsen, eds. Implementationand Applications of DSL Technology. Boca Raton,Fla.: CRC Press, 2007.Mitchell, Bradley. “DSL vs. Cable: Modem Comparison.” Availableonline. URL:http://compnetworking.about.com/od/dslvscablemodem/a/dslcablecompare.htm. Accessed September16, 2007.Reynolds, Janice. A Practical Guide to DSL: High-Speed Connectionsfor Local Loop and Network. New York: CMP Books, 2001.Smith, Roderick W. Broadband Internet Connections: A User’s Guideto DSL and Cable. Upper Saddle River, N.J.: Addison-WesleyProfessional, 2007.DTP See desktop publishing.DVR (digital video recording)A digital video recorder (DVR) records digital televisionbroadcasts and stores them on a disk (see hard disk andcd-rom and dvd-rom). DVRs first appeared as commercialproducts in 1999 in Replay TV and TiVo, the latter becomingthe most successful player in the field.A DVR works with digital signals and discs rather thantape used by the video cassette recorders (VCRs) that hadbecome popular starting in the 1980s. The digital recorderhas several advantages over tape:• much larger capacity, limited only by hard drive size• instant (random) access to any recorded programmingwithout having to go forward or backward through atape• the ability to “time shift” within a live broadcast,including pausing and instant replay• the ability to skip over commercials• digital special effectsDVR and Integrated EntertainmentBesides what it can do with the program itself, the otherbig advantage of DVR technology stems from the fact thatit produces digital data in a standard format (usually an

164 DVRMPEG file) that is fully compatible with PCs and other computingdevices. Indeed, by installing one or more TV tunersor “cable cards” (for access to digital cable signals) to a PC,one need only add suitable software to turn a Windows,Macintosh, or Linux PC into a versatile DVR. Alternatively,many cable and satellite TV services are offering set-topboxes with built-in DVRs.Services such as TiVo also provide access to an onlineprogram schedule (for a monthly charge). This works withfeatures that allow the user to scan for and review programlistings and to arrange, for example, to record all new episodesof a weekly series as they arrive. DVRs with dual tunersallow for recording two live programs simultaneously,or recording one while watching another.DVR technology is also now being used for closed-circuittelevision (CCTV) surveillance systems, due to superiorstorage and playback capabilities. Similar technology isalso found in digital video cameras (camcorders).DVRs are part of a landscape where entertainment thatused to be confined to television broadcast, cable, or satellitesystems can now be received digitally over the Internet.Since DVRs produce digital output, recorded programscan be easily shared over the Internet, such as by postingon the popular YouTube site, possibly leading to lossof revenue for the original providers (see intellectualproperty and computing). In response, HBO and otherproviders have argued for requiring that DVRs recognizecontent that is flagged as “copy never” and refuse to copysuch programs.Another problem for providers is the growing numberof DVR users who have the ability to easily skip over commercials.Attempts are being made to make commercialsshorter and more entertaining, or to rely more on productplacement within the programming itself.Further ReadingDVR Buying Guide. Available online. URL: http://products.howstuffworks.com/dvr-buying-guide.htm. Accessed September16, 2007.ReplayTV. Available online. URL: http://www.replaytv.com/.Accessed September 16, 2007.TiVo. Available online. URL: http://www.tivo.com/. Accessed September16, 2007.

EeBayeBay Inc. (NASDAQ symbol: EBAY) is the world’s largestonline auction and shopping site. The first appearance ofthe auction service was in 1995 as AuctionWeb, part of thepersonal Web site of Pierre Omidyar (see auctions, onlineand Omidyar, Pierre). Omidyar was surprised at how rapidlythe auction service (which was initially free) grew. Afterhe imposed a modest listing fee, Omidyar found himselfreceiving thousands of dollars in small checks, and decidedthat online auctions could become a full-time business.In September 1997, with Jeff Skoll now on board aspresident, AuctionWeb officially became eBay. When thecompany went public in 1998 (at the height of the first“Internet boom”), Omidyar and Skoll became instant millionaires.Meanwhile, eBay took on Margaret (Meg) Whitmanas its new CEO, and under her leadership the companyhas expanded rapidly through its first decade.eBay also seeks new markets and revenue through strategicacquisitions. These include payment services such asthe very popular PayPal, other e-commerce sites such asHalf.com, shopping.com, and rent.com, and even Skype,the Internet phone service. eBay’s net revenue for 2007 was$7.67 billion.Online AuctionsAuctions remain at the core of eBay’s business, with millionsof items in dozens of categories being listed and soldeach day. Offerings can range from factory equipment (inthe Business & Industrial category) to books, toys, sportsmemorabilia—even cars and, in a limited fashion, realestate. There are now hundreds of small- to medium-sizebusinesses who derive their revenue from eBay, whetherselling their own merchandise, acting as agents for others,or selling software or templates for managing auctions.eBay does not charge any buyer’s fees, but makes itsmoney by charging the seller for each listing and then apercentage of the selling price. As of 2007 eBay has regionaloperations in more than 20 countries, including China andIndia. (Yahoo, a distant second to eBay in online auctions,discontinued its U.S. auction site in mid-2007.)Beyond AuctionsIn recent years eBay has increasingly tried to build a more“traditional” online shopping experience in parallel with itsauctions. The Buy It Now feature allows a seller to list anitem at a fixed price, either instead of auctioning the itemor as an option that can be exercised if there have been noauction bids. Sellers can organize their offerings into regular“stores” to make it easier for customers to browse theirmerchandise. (Many traditional stores, such as antiques orcollectibles dealers, now offer some of their items via theireBay store.) eBay Express, introduced in 2006, adds convenienceby allowing users to buy selected items from multiplesellers using a standard online shopping cart.Like Amazon.com, eBay has focused considerable attentionon developing more ways for users to comment ontheir purchases and otherwise contribute content (seeuser-created content). The most important mechanismis feedback, which lets buyers summarize their opinionsof a transaction after its completion. The feedback system165

166 e-books and digital librarieshas been recently expanded and structured to allow usersto give specific ratings on aspects of the transaction, suchas accuracy of description and shipping cost and speed.Although not perfect (feedback can be “pumped up” bysetting up phony transactions between two accounts), thesystem does allow buyers to exercise a certain amountof caution before bidding on an expensive item from anunknown seller. eBay also offers various forms of “consumerprotection” if items are not received or are substantiallynot as described.Not surprisingly in a marketplace of this size, thereis opportunity for various forms of fraud, including saleof counterfeit, defective, or lower-grade merchandise and,on the part of buyers, credit card fraud. eBay has beencriticized for not policing fraud adequately. Generally, theservice has maintained the position that it is only a facilitatorof transactions. If it had to guarantee the authenticity ofmerchandise, it would have to operate like a conventionalauction house, with the attendant fees. However, eBay hassolicited the help of experts in fields such as coins andstamps to help them identity counterfeit or misdescribeditems.eBay provides a number of forums for user comments,including discussion boards and chat rooms. Users canalso write reviews and guides to help, for example, novicecollectors who might find themselves overwhelmed bythe coin or stamp listings. In mid-2006 eBay expanded its“community content” to include an eBay Community Wiki(see wikis and Wikipedia) and eBay blogs (see blogs andblogging).eBay is always trying to make it easier to match users’specific needs with the thousands of potentially relevantofferings. Providing recommendation information (includinguser-generated recommendations) is another way tomake shopping easier and more satisfying, as has beenshown by Amazon.com. Another possible way to get a biggershare of users’ day-to-day purchases is to make eBayavailable on mobile devices as well as linking it to sitessuch as Facebook, where young people in particular spendmuch of their time (see social networking.)Long-time eBay CEO Meg Whitman stepped down inMarch 2008, while calling for innovation to reinvigoratea company that many observers now consider to be staidand “old school” in the age of Web 2.0. Whitman’s successor,John Donahoe, has announced a new fee structure andnew ways of searching for and displaying listings—developmentsthat have provoked some controversy in the sellercommunity.Further ReadingBergstein, Brian. “Middle-aged eBay in for Changes.” AssociatedPress/San Francisco Chronicle, June 18, 2007. p. C3.Cohen, Adam. The Perfect Store: Inside eBay. Boston: Little, Brown,2002.Collier, Marsha. eBay for Dummies. 5th ed. Hoboken, N.J.: Wiley,2006.———. Starting an eBay Business for Dummies. Hoboken, N.J.:Wiley, 2007.eBay. Available online. URL: http://www.ebay.com. Accessed September16, 2007.e-books and digital librariesAn e-book is a book whose text is stored in digital formand can be read on a PC or a handheld reading device.Since most books today are created on word processors andtypesetting systems, it is easy for a publisher to create anelectronic version. Older books that exist only in printedform can be scanned and converted to text (see opticalcharacter recognition).An e-book has a number of advantages over its printedcounterpart. The text can be searched and can include linksto sections or even to documents on the World Wide Web.Reading software or devices can easily enlarge text for thevisually handicapped, or read it in a synthesized voice.Since only bits need to be moved around, e-books save treesas well as the cost of manufacturing, transporting, warehousing,and displaying conventional books.There are some disadvantages. Many people are notcomfortable reading large amounts of text at a computer.Portable reading devices that may be more convenient arerelatively expensive and not standardized. There is no universalformat for e-books, so some software or readers maynot be able to read all e-books.As of 2008 the e-book landscape may be in the processof being reshaped. Amazon’s Kindle book reader is the latestattempt to marry e-books to handheld devices. Weighingless than a paperback book, the Kindle can downloadbooks and other content directly over a cellular broadbandconnection and display text using an “electronic ink” technologythat simulates print. Amazon is offering a largeselection of e-books including electronic versions of currentbest sellers at prices several dollars below that of the hardbackversion.Authors and publishers, like other content creators, mayhave to deal with the illicit copying and distribution of textin digital form, as happened with the last Harry Potter bookeven before its publication in 2007. Some e-books contain aform of copy protection (see digital rights management).This, as with video and music, can lead to compatibilityproblems.A number of e-publishers as well as conventional publishersnow offer books online, most commonly as pdf(portable document format) files. A hybrid service, “publishon demand,” keeps the book on file and prints and shipsbound copies as they are ordered, eliminating the problemof remainders. In the future, so-called digital paper (a thinmembrane that can display text), may be used to create amore booklike reading experience.Digital LibrariesA digital library is to e-books what a conventional libraryis to printed books. Sometimes called an electronic libraryor virtual library, digital libraries can be created in avariety of ways. Printed books can now be scanned anddigitized rapidly. Google has said that it can scan 3,000volumes a day using a proprietary system. (This is notnecessary, of course, for books that were originally createdin digital form.)Advantages of digital libraries include the following:

Eckert, J. Presper 167• There is never a shortage of copies or the need for areader to wait for access.• many digital libraries allow full searching of the textof all volumes. Libraries can also use a common dataformat (such as “Open Archives.”) to make their materialsearchable throughout the Internet.• many older, hard-to-find books can be made more“discoverable” and accessible.Project Gutenberg is one of the oldest and best-knowndigital library projects, dating back to 1971. Most of thecollection consists of scanned or transcribed texts of publicdomain (no longer subject to copyright) books. As of late2007, Project Gutenberg had more than 17,000 differenttitles in its collection.Of course more recent books are covered by copyright.In order to include copyrighted books in a digital library,some sort of compensation to the copyright holder generallyneeds to be made, and it is unclear how that might beimplemented in a way that preserves free access.There are also what might be called “digital pseudolibraries”such as Google Book Search. Google has beenscanning part or all of the collections of universities such asStanford, Harvard, and Oxford as well as the New York PublicLibrary. Google provides full access to public domainbooks (or those for which permission has been obtainedfrom the publisher). For copyrighted books there is a limitedability to search by keyword and view a limited numberof pages. Amazon.com’s “Search inside the Book” worksrather similarly, but only with books for which the publisherhas granted permission.Google’s initiative has aroused some controversy because,according to traditional practice, someone wanting access toa copyrighted work beyond “fair use” is supposed to obtainpermission. Google has reversed this presumption, allowingpublishers who do not want their material to be available toopt out. The Authors Guild of America and the Association ofAmerican Publishers have separately sued Google for copyrightinfringement. Google argues that the limited amountof text provided for copyrighted books falls within the fairuse provisions of copyright law. The authors and publishers,however, point to the fact that Google is copying thewhole text of the book in order to allow for searching.If the legal issues can be settled in such a way as toallow robust digital libraries, the benefits for researcherswill be considerable. Google already offers a “my library”feature that users can use to search for books they alreadyknow and organize and search them digitally.Further ReadingGoogle Book Search. Available online. URL: http://books.google.com/. Accessed September 16, 2007.Hirschhorn, Michael. “The Hapless Seed: Publishers and AuthorsShould Stop Cowering. Google Is Less Likely to Destroy theBook Business Than to Slingshot It into the 21st Century.”Atlantic Monthly, June 2007, p. 134 ff.Kelly, Kevin. “Scan This Book!” New York Times Magazine, May 14,2006. pp. 42–49, 64, 71.Kresh, Diane, ed. The Whole Digital Library Handbook. Chicago:American Library Association, 2007.Lesk, Michael. Understanding Digital Libraries. 2nd ed. San Francisco:Morgan Kaufmann, 2004.Project Gutenberg. Available online. URL: http://www.gutenberg.org/wiki/Main_Page. Accessed September 16, 2007.Thompson, Bob. “Google Wants to Digitize Every Book. PublishersSay Read the Fine Print First.” Washington Post, August12, 2006, p. D1.Eckert, J. Presper(1919–1995)AmericanComputer EngineerJ. Presper Eckert played a key role in the design of what isoften considered to be the first general-purpose electronicdigital computer, then went on to pioneer the commercialcomputer industry. An only child, Eckert grew up ina prosperous Philadelphia family that traveled widely andhad many connections with Hollywood celebrities such asDouglas Fairbanks and Charlie Chaplin. He was a star studentin his private high school and also did well at the Universityof Pennsylvania, where he graduated in 1941 with adegree in electrical engineering and a strong mathematicsbackground.Continuing at the university as a graduate student andresearcher, Eckert met an older researcher, John Mauchly.They found they shared a deep interest in the possibilitiesof electronic computing, a technology that was beingspurred by the needs of war research. After earning hismaster’s degree in electrical engineering, in 1942 Eckertjoined Mauchly in submitting a proposal to the BallisticResearch Laboratory of the Army Ordnance Department fora computer that could be used to calculate urgently neededfiring tables for guns, bombs, and missiles. The Armygranted the contract, and they organized a team that grewto 50 people. Begun in April 1943, their ENIAC (ElectronicNumerical Integrator and Computer) was finished in 1946.While it was too late to aid the war effort, the room-sizemachine filled with 18,000 vacuum tubes demonstrated thepracticability of electronic computing. Its computation rateof 5,000 additions per second far exceeded other calculatorsof the time.With some input from mathematician John von Neumann,Eckert and Mauchly began to develop a newmachine, EDVAC, for the University of Pennsylvania (seevon Neumann, John). While this effort was still underway, they formed their own business, the Eckert-MauchlyComputer Corporation and began to develop the BINAC(BINary Automatic Computer), which was intended to bea (relatively) compact and lower-cost version of ENIAC.This machine demonstrated a key principle of modern computers—thestorage of program instructions along withdata. The ability to store, manipulate, and edit instructionsvastly increased the flexibility and ease of use of computingmachines (see history of computing).By the late 1940s, Eckert and Mauchly began to developUnivac I, the first commercial implementation of the newcomputing technology. When financial difficulties threatenedto sink their company in 1950, it was acquired by

168 e-commerceRemington Rand. Working as a division within that company,the Eckert-Mauchly team completed Univac I in timefor the computer to make a remarkably accurate forecast ofthe 1952 presidential election results.Eckert continued with the Sperry-Rand Corporation(later called Univac and then Unisys Corporation) andbecame a vice president and senior technical adviser. Heretired in 1989. He received an honorary doctorate fromthe University of Pennsylvania in 1964. In 1969, he wasawarded the National Medal of Science, the nation’s highestaward for achievement in science and engineering.Further ReadingEckstein, P. “Presper Eckert.” IEEE Annals of the History of Computing18, vol. 1, Spring 1996, 25–44.McCartney, Scott. Eniac: the Triumphs and Tragedies of the World’sFirst Computer. New York: Berkley Books, 1999.Smithsonian Institution. National Museum of American History.“Presper Eckert Interview.” Available online. URL: http://americanhistory.si.edu/collections/comphist/eckert.htm.Accessed August 14, 2007.e-commerceSince the introduction of credit cards and the beginningof banking automation in the 1960s, computers and communicationsnetworks have played an increasing role in theinfrastructure of commerce (see banking and computers).Some businesses also established proprietary networks (forexample, to allow pharmacies to order drugs directly fromsuppliers).Electronic sales directly to consumers were pioneeredby “teletex,” such as the French Minitel, as well as such servicesas CompuServe and America Online. However, theseservices were proprietary, meaning that businesses couldonly market to subscribers. The widespread adoption of theInternet in the mid-1990s (see World Wide Web) createdan open and potentially much larger marketplace.The first e-commerce boom came in the late 1990s,when enthusiasm about the seeming potential for unlimitedprofits drove numerous online startups, often withpoorly conceived business plans that assumed that rapidexpansion and low prices would result in gaining controlof a particular sector and achieving a dominant (andprofitable) position. Among the numerous casualties ofthe “dot-bust” of 2000–2001 was WebVan, a companythat sold and delivered groceries directly to consumer’shomes.While the bursting of the “dot-com bubble” was painfulto investors, entrepreneurs, and workers, recoverywas soon underway. The recovery was aided by the steadygrowth of Internet users (particularly those with broadbandconnections), innovative software for interacting withconsumers and analyzing transaction information, and thecoming of age of a generation that had virtually grown uponline.Today e-commerce is a steadily growing sector, and it isincreasingly international, fed by nearly 1.5 billion Internetusers worldwide. (China, with more than 250 million Webusers, has become the world’s largest online market.)Meanwhile in the United States in 2007 total consumerretail sales on the Internet reached $136 billion, up nearly20 percent over the previous year. According to a reportfrom Forrester Research, online retail revenues (excludingtravel-related services) will pass $250 billion by 2011. Surveysshow that about 80 percent of American Internet usershave bought something online, while many users who buyproducts off-line originally searched for information aboutthem online.The most popular e-commerce sectors today include theselling of books, music and movies, travel-related services,electronics, clothing, luxury goods, and medications. (In2006, online buyers actually spent more money on clothingthan on computers and related products.) A numberof other online activities can be considered part of e-commerce,although they are usually not included in retailingstatistics (see auctions, online; online gambling;online games; and social networking).InfrastructureSuccessful e-commerce depends on a complex array of services,facilities, and software. For marketing and consumercommunications, see online advertising and customerrelationship management. Behind the scenes, transactiondata is constantly being collected and analyzed todetermine the success of the marketing program and to“personalize” the customer experience and allow for targetedmarketing (see cookies and data mining).The actual transaction processing requires shoppingcart software and a connection to the credit card processinginfrastructure (see digital cash). Specialized forms of sellingrequire additional software and support systems (see,for example, auctions, online). An ongoing e-businessmust also deal with functions shared by “brick and mortar”(traditional) stores: inventory control, ordering from suppliers(see supply chain management), taxes, payroll, andso on. The broader e-commerce sector also includes businessesthat do not target consumers but, rather, the needsof business itself—so-called business to business or B2B.Security and PrivacyOne continuing obstacle to the growth of e-commerce hasbeen consumers’ concerns about the theft or misuse of personalinformation gathered as part of the shopping process.This can involve either fake Web sites (see phishing andspoofing) or legitimate businesses that sell informationabout customers without their knowledge or consent (seeprivacy in the digital age). According to a report fromGartner Research, more than $900 million in e-commercesales during 2006 was lost because of consumers’ securityconcerns, and about a billion dollars more in sales was lostbecause customers decided not to buy online at all.TrendsE-commerce is maturing even as it continues to evolve.Some trends in the second half of the 2000 decade reflectchanges in what is presented to the consumer, how it isdelivered, and how users can participate in ways other thansimply viewing content and selecting products:

education and computers 169Jupiter Research. Available online. URL: http://www.jupiterresearch.com. Accessed July 10, 2007.Laudon, Kenneth, and Carol Traver. E-Commerce: Business, Technology,Society. 3rd ed. Upper Saddle River, N.J.: PrenticeHall, 2006.education and computersComputers are widely used in educational institutions fromelementary school to college. While computers have had asyet little impact on the structure or organization of schools,educational software and the use of the Internet has had agrowing impact on how education is delivered.E-commerce involves far more than just advertising and sellinggoods and services. In a typical e-commerce system a “shoppingcart” records consumers’ selections. The items ordered must beprocessed against inventory and prepared for shipping. Meanwhile,information about the user’s selections and viewing is fedinto a database from which patterns of consumer behavior can beextracted. Some techniques of information gathering raise privacyconcerns, however.• delivery of richer and more interactive multimediaexperience, catering to the widespread availability ofbroadband connections• integration of marketing using programming interfaces(see mashups) with popular online servicessuch as Google Maps, online game worlds, and socialnetworking sites (see online games and social networking)• increasing participation of consumers in developingthe quality of the shopping experience, such asthrough user product reviews and blogs (see usercreatedcontent)• increased emphasis on serving rapidly growing foreignmarkets, such as India and China• the spread of e-commerce to new mobile platforms(see pda and smartphone)Further ReadingCombe, Colin. Introduction to e-Business: Management and Strategy.Burlington, Mass.: Elsevier, 2006.eCommerce Info Center. Available online. URL: http://www.ecominfocenter.com/. Accessed July 15, 2007.eCommerce Times. Available online. URL: http://www.ecommercetimes.com.Accessed July 16, 2007.Forrester Research. Available online. URL: http://www.forrester.com. Accessed July 10, 2007.Grant, Graeme. “Trends in 2007 Online Retailing.” Availableonline. URL: http://www.destinationcrm.com/articles/default.asp?ArticleID=6938. Accessed July 10, 2007.HistoryDuring the 1950s and early 1960s, computer resources weregenerally too scarce, expensive, and cumbersome to be usedfor teaching, although universities aspired to have computersto aid their graduate and faculty researchers. However,during the 1960s computer engineers and educators at theComputer-based Education Research Laboratory at the Universityof Illinois, Urbana, formed a unique collaborationand designed a computer system called PLATO. The PLATOsystem used mainframe computers to deliver instructionalcontent to up to 1,000 simultaneous users at terminalsthroughout the University of Illinois and other educationalinstitutions in the state. PLATO pioneered the interactiveapproach to instruction and the use of graphics in additionto text. The PLATO system was later marketed by ControlData Corporation (CDC) for use elsewhere. During thistime Stanford University also set up a system for deliveringcomputer-assisted instruction (CAI) to users connectedto terminals throughout the nation. (See computer-aidedinstruction.)By the early 1980s, microcomputers had become relativelyaffordable and capable of running significant educationalsoftware including graphics. Apple Computer’sApple II became an early leader in the school market, andthe introduction of the Macintosh in 1984 with the Hypercardscripting language inspired many teachers and otherenthusiasts to create their own educational software. Bythe early 1990s, IBM compatible PCs with Windows werecatching up. Commercially available computer games(such as Civilization or Railroad Tycoon) also offered waysto enrich social studies and other classes (see computergames).The advent of the World Wide Web and graphical Webbrowsing in the mid-1990s spurred schools to connect tothe Internet. The Web offered the opportunity for educatorsto create resources that could be accessed by colleaguesand students anywhere in the world. The use ofWeb portals such as Yahoo!, library catalogs, and onlineencyclopedias gave teachers and students potential accessto a far greater variety of information than could possiblybe found in textbooks. The Web also offered theopportunity for students at different schools to participatein collaborative projects, such as community surveys orenvironmental studies.

170 education and computersApplicationsEducational applications of computing can be divided intoseveral categories, as summarized in the following table.While small compared to the business market, theeducational software industry is a significant market, targetingboth schools and parents seeking to improve theirchildren’s academic performance. However, the educationaluse of computers extends far beyond specialized software.Schools are in effect a major industry in themselves, requiringmuch of the same support software as large businesses.TrendsThe growth of the World Wide Web has led to some shiftof emphasis away from stand-alone, CD-ROM based applicationsrunning on local PCs or networks. Educators areexcited about the possibilities for online collaboration.Public concern about children achieving an adequate levelof technical skill (see computer literacy) has fueled anincreasing commitment of funds for computer hardware,software, and networking for schools.Some visionaries speak of a 21st-century “virtual school”that has no classroom in the conventional sense, but usesthe Internet and conferencing software to bring teachersand students together. While there has been only limitedexperimentation in creating virtual secondary schools,thousands of university courses are now offered online, andmany degree programs are now available. Some institutionssuch as the University of Phoenix have made such “distancelearning” a core part of their growth strategy.Several factors have caused other observers to have misgivingsabout the rush to get schools onto the “informationsuperhighway.” Many schools lack adequate physical facilitiesand teacher training. Under those circumstances otherpriorities might deserve precedence over the installation oftechnology that may not be effectively utilized. At the sametime, the lagging in access to technology by minorities andthe poor may suggest that schools must play a significantrole in providing such access and enabling the coming generationto catch up (see digital divide).The debate over how best to use technology in theschools also reflects fundamental theories about teachingand learning. Critics of information technology such asClifford Stoll (see Stoll, Clifford) have reacted againstthe mechanical, rote nature of much educational software.They also decry the hype of some advocates who have suggestedtechnology as a panacea for the problems of lowperformance, poor motivation, and lack of accountability inmany schools.Some advocates of computer use agree with the criticismof uncreative and poorly planned “e-learning” programs,but argue that the answer is to use technology that helpsgood teachers unlock creativity. For example, Seymour Papertand his LOGO language are based on “constructivist”principles where students learn through doing (see Papert,Seymour and logo). From this point of view, “computerliteracy” should not be a focus in itself, but one outcomeof a program that creates literate and capable learners (seecomputer literacy.)Application Area Users examplesComputer-aided Generally high school and up Course modules for science, social studies, etc. Studentsinstruction (CAI) evaluated and materials presented on the basis of student performance(see computer-aided instruction).Drill-and-practice Elementary school students Sets of math problems, geography quizzes, etc. Sounds or graphicsused for reward for correct answers.Online collaborative Elementary and high school Students from different schools use e-mail or chat to coordinate alearning students project, such as creating a Web site about local environmentalissues.Online classes Mainly college and adults Students participate remotely through videoconferencing, chat,e-mail, etc. (see distance education).Educational Junior high and older students Gamelike programs that simulate real-world problems, such assimulationsmanaging a city to investing in the stock market. Often commerciallyavailable games can be used.Reference and Elementary and older students Online encyclopedias and knowledge bases (see also wikis andresourcesWikipedia); specialized references on CD-ROM or DVD; onlinereference and bibliographical databases; library catalogs; andWeb site of universities, museums, and government agencies.General software Students and teachers Use of general-purpose software such as word processors,applicationspublishing, or presentation programs for creating class projectsand reports. Also use of e-mail, chat, and blogs for collaborationand after-hours communication between students and teachers.Administrative Teachers and administrators Use of specialized or general-purpose software to maintainapplicationsattendance, grades, and other class and school administrationfunctions.

education in the computer field 171Further ReadingCuban, Larry. Oversold & Underused: Computers in the Classroom.Cambridge, Mass.: Harvard University Press, 2001.Global Schoolhouse. Available online. URL: http://www.globalschoolnet.org. Accessed July 19, 2007.November, Alan. Empowering Students with Technology. Arlington,Ill.: SkyLight Professional Development, 2001.Paley, Amit R. “Software’s Benefits on Tests in Doubt: Study SaysTools Don’t Raise Scores.” Washington Post, April 5, 2007, p. 1.Pflaum, William D. The Technology Fix: The Promise and Realityof Computers in Our Schools. Alexander, Va.: Association forSupervision and Curriculum Development, 2004.Richardson, Will. Blogs, Wikis, Podcasts, and Other Powerful WebTools for Classrooms. Thousand Oaks, Calif.: Corwin Press,2006.Stoll, Clifford. High Tech Heretic: Why Computers Don’t Belong inthe Classroom and Other Reflections by a Computer Contrarian.New York: Doubleday, 1999.“Technology Integration.” Education World. Available online.URL: http://www.educationworld.com/a_tech/. Accessed July19, 2007.Warlick, David. Classroom Blogging: A Teacher’s Guide to the Blogosphere.Morrisville, N.C.: Lulu.com, 2005.education in the computer fieldEducation and training in computer-related fields runs thegamut from courses in basic computer concepts in adulteducation or junior college programs to postgraduate programsin computer science and engineering. Curricula canbe roughly divided into the following areas• computer literacy and applications• computer science• information systemsComputer Literacy and ApplicationsThere is a general consensus that basic knowledge of computerterminology and mastery of widely used types of softwarewill be essential for a growing number of occupations(see computer literacy). The elementary and junior highschool curriculum now generally includes computer classesor “labs” where students learn the basics of word processing,spreadsheets, databases, graphics software, and useof the World Wide Web. There may also be introductorycourses in programming, usually featuring easy-to-use programminglanguages such as Logo or BASIC.Some high schools offer a track geared toward preparationfor college studies in computer science. This track mayinclude courses in more advanced languages such as C++ orJava. Because of public interest and marketability, courses ingraphics (such as use of Adobe Photoshop), multimedia, andWeb design are also increasingly popular. Adult educationand community college programs feature a similar range ofcourses. Many of today’s adult workers went to school at atime when personal computers were not readily available andcomputer literacy was not generally emphasized. The careerprospects of many older workers are thus increasingly limitedif they don’t receive training in basic computer skills.Technical or vocational schools offer tightly focused programsthat are geared toward providing a set of marketableskills, often in conjunction with gaining industry certifications(see certification of computer professionals).Computer ScienceIn the early 1950s, knowledge of computing tended to havean ad hoc nature. On the practical level, computing staffstended to train newcomers in the specific hardware andmachine-level programming languages in use at a particularsite. On the theoretical level, programmers in scientificfields were likely to come from a background in electronics,electrical engineering, or similar disciplines.As it became clear that computers were going to play anincreasingly important role, courses specific to computingwere added to curricula in mathematics and engineering.By the late 1950s, however, leading people in the computingfield had become convinced that a formal curriculum incomputer science was necessary for further advance in anincreasingly sophisticated computing arena (see computerscience). By the early 1960s, efforts at the University ofMichigan, University of Houston, Stanford, and other institutionshad resulted in the creation of separate graduatedepartments of computer science. By the mid-1960s, theNational Academy of Sciences and the President’s ScienceAdvisory Committee had both called for a major expansionof efforts in computer science education to be aided byfederal funding. During the 1970s and 1980s, mathematicaland engineering societies (in particular the Associationfor Computing Machinery (ACM) and Institute for Electricaland Electronic Engineering (IEEE) worked to establisheddetailed computer science curricula that extendedto undergraduate study. By 2000, there were 155 accreditedprograms in computer science in the United States.Information SystemsThe traditional computer science curriculum emphasizestheoretical matters such as algorithm and program designand computer architecture. Hiring managers in corporateinformation systems departments have observed thatcomputer science graduates often have little experience insuch practical considerations as systems analysis, or thedesigning of computer systems to meet business requirements.There has also been an increasing need for systemsadministrators, database administrators, and networkingprofessionals who are well versed in the management andmaintenance of particular systems.In response to demand from industry, many universitieshave instituted degree programs in information systems(sometimes called MIS or Management InformationSystems) as an alternative to computer science. While theseprograms include some study of theory, they focus on practicalconsiderations and often include internships or otherpractical work experience. Some programs offer more ambitiousstudents a dual track leading to an MBA.ChallengesThere has always been a gap between the emphases in computerand information science programs and the needs ofa rapidly changing marketplace. However, additional chal-

172 e-governmentlenges face education in the computer field today. The numberof undergraduate computer science degrees awarded inPh.D.-granting universities in the United States has steadilydeclined since 2000. In part this may be a delayed reactionto the decline in employment of programmers early in thedecade (due to the bursting of the “dot-com bubble”) that hassince leveled off but has not significantly grown (see employmentin the computer field). This, together with the outsourcingof many jobs (see globalism and the computerindustry) may have in turn discouraged young people fromentering the field.At the same time, many observers insist that prospectsare good for educators and students who can target emerginghigh-demand skills. These include areas such as computersecurity, data mining, bioinformatics, Web contentmanagement, and even aspects of business management.Educators will be challenged to strike a balance between acomprehensive treatment of concepts that have many potentialapplications and the need to provide specific skills thatare in demand in the market.Further ReadingACM-IEEE Joint Task Force on Computing Curricula. “ComputerScience. 2001.” Available online. URL: http://acm.org/education/curric_vols/cc2001.pdf. Accessed July 22, 2007.———. “Information Systems.” 2001 Available online. URL:http://www.acm.org/education/is2002.pdf. Accessed July 22,2007.Anthes, Gary. “Computer Science Looks for a Remake.” Computerworld.May 1, 2006. Available online. URL: http://www.computerworld.com/careers/story/0,10801,110959,00.html.Accessed July 22, 2007.Computer Science Directory. Available online. URL: http://csdir.org/. Accessed July 22, 2007.Denning, Peter J. “Great Principles in Computing Curricula.”ACM SIGCSE Bulletin, vol. 36, March 2004. Available online.URL: http://portal.acm.org/citation.cfm?id=1028174.971303.Accessed July 22, 2007.Greening, Tony, ed. Computer Science Education in the 21st Century.New York: Springer-Verlag, 2000.Open Directory Project. “Computer Science.” Available online. URL:http://dmoz.org/Computers/Computer_Science/. Accessed July22, 2007.e-governmentJust as the way business is organized and conducted hasbeen profoundly changed by information and communicationstechnology, the operation of government at all levelshas been similarly affected. The term e-government (or electronicgovernment) is a way of looking at these changes asa whole and of considering how government uses (or mightuse) various computer applications.The use of information technology in government caninvolve changes in the organization and internal communicationsof government departments, changes in how servicesare delivered to the public, and providing new waysfor the public to interact with the agency.Internally, government agencies have many of the sameinformation management and sharing needs as privateenterprises (see data mining, database administration,e-mail, groupware, personal information manager,and project management software). However, governmentagencies are likely to have to adapt their informationsystems to account for complex, specialized regulations(both those the agency administers and others it is subjectto). The standards of openness and accountability are generallydifferent from and stricter than those that apply toprivate organizations.A major focus of e-government is in expanding agencies’presence on the Web and making government sites moreuseful. This can include providing summaries of regulationsor other complicated information, offering online assistance,allowing filing of tax or other forms electronically,and helping with applications such as for Social Security orMedicare. Where applicants must physically visit the office,a computerized system can make it easy to make appointmentsto reduce time waiting in line (a welcome option nowoffered by many state departments of motor vehicles).ImplementationObtaining employees with the necessary skills for maintainingsophisticated information systems and modern dynamicWeb sites is not easy. The government hiring process tendsto be cumbersome and slow to respond to changing needs.Government must often compete with a private sector thatis willing to pay high prices for top talent.In many cases, adopting comprehensive e-governmentwould require a rethinking of an agency’s purpose and priorities.There is also a tension between the Web culture,which focuses on linking information across conventionalboundaries, and the tendency of bureaucracies to compartmentalizeand centrally control information. Nevertheless,even without fundamentally restructuring how agenciesoperate, there has been considerable success with bringinginformation to the public through a central portal (USA.gov, formerly FirstGov).Once a service is offered, it has to be promoted. Whilesome services (such as “e-filing” of tax returns) can be readilypromoted for their convenience, other services are moreobscure or may be of interest only to a narrow constituency.Social and Political ImpactA survey by the Hart-Teeter poll found that respondentsconsidered the most important potential benefit of e-governmentto be greater government accountability; thesecond was greater access to information; and, perhaps surprisingly,convenience came third.One criticism of e-government initiatives is that theyoften lack central coordination and may be implementedwithout keeping in mind the need of an agency to provideuniform, consistent, and impartial treatment to all citizens.For example, if an agency focuses its resources on developingits Web site, people who lack online access may cometo feel that they are receiving “second class” service (seedigital divide). This is particularly unfortunate becausethe unconnected people are likely to be in poor and isolatedcommunities that are most likely to be in need of governmentservices.

Eiffel 173As with private enterprise, there can also be importantonline privacy issues. Information that has been collecteddigitally is easy to transfer to other agencies or even (as inthe case of DMV information in some states) sold to privatecompanies. Having a clearly spelled-out privacy policy iscrucial.Besides keeping private what people expect to be private,government agencies must also provide informationthat helps ensure public accountability. Information collectedby government agencies is often subject to the Freedomof Information Act (FOIA). This may require that databe provided in a format that is readily accessible.Further ReadingBriefing Book Outline: E-Government. Advisory Committee to theCongressional Internet Caucus. Available online. URL: http://www.netcaucus.org/books/egov2001/. Accessed September18, 2007.Center for Technology in Government. Available online. URL:http://www.ctg.albany.edu. Accessed September 18, 2007.Cordella, Antonio. “E-Government: Towards the E-bureaucraticForm?” Journal of Information Technology 22 (2007): pp. 265–274.Government Computerization (Open Directory). Availableonline. URL: http://www.dmoz.org/Society/Issues/Science_and_Technology/Computers/Government_Computerization/.Accessed September 18, 2007.LaVigne, Mark. “E-Government: Creating Tools of the Trade.”Available online. URL: http://www.netcaucus.org/books/egov2001/pdf/e-govt.pdf. Accessed September 18, 2007.Rosencrance, Linda. “User Satisfaction with Federal GovernmentWeb Sites down Slightly.” Computerworld, September18, 2007. Available online. URL: http://www.computerworld.com/action/article.do?command=viewArticleBasic&articleId=9037079. Accessed September 18, 2007.USA.gov: “Government Made Easy” [Official U.S. GovernmentPortal]. Available online. URL: http://www.usa.gov/. AccessedSeptember 18, 2007.EiffelEiffel is an interesting programming language developedby Bertrand Meyer and his company Eiffel Software in the1980s. The language was named for Gustav Eiffel, the architectwho designed the famous tower in Paris. The languageand accompanying methodology attracted considerableinterest at software engineering conferences.Eiffel fully supports (and in some ways pioneered) programmingconcepts found in more widely used languagestoday (see class and object-oriented programming). Syntactically,Eiffel emphasizes simple, reusable declarations thatmake the program easier to understand, and tries to avoidobscure or lower-level code such as compiler optimizations.Program StructureAn Eiffel program is called a “system,” emphasizing itsstructure as a set of classes that represent the types of realworlddata that need to be processed. A simple class mightlook like this:classCOUNTERfeature—access counter valuetotal: INTEGERfeature—manipulate counter valueincrement is—increase counter by onedototal :- total + 1enddecrement is—decrease counter by onedototal := total - 1endreset is—reset counter to zerodototal := 0endend(In this listing language, keywords are in bold and userdefinedobjects are in italics. This formatting will be doneautomatically as the user enters the text.) Once the class isdefined, making an instance of it is very simple:my_counter COUNTERcreate my_counterThe Eiffel compiler itself compiles to an intermediate“bytecode” that, in the final stage, is compiled into C, takingadvantage of the ready availability of optimized C compilers.A unique feature of Eiffel is the ability to set up “contracts”that specify in detail how classes will interact withone another. (This goes well beyond the usual declarationsof parameters and enforcement of data types.) For example,with the COUNTER class an “invariant” can be declaredsuch that total >= 0. This means that this condition mustalways remain true no matter what. A method can alsorequire that the caller meet certain conditions. After processingand before returning to the caller, the method canensure that a particular condition is true. The point of thesespecifications is that they make explicit what a given unit ofcode expects and what it promises to do in return. This canalso improve program documentation.Implementation and UsesEiffel’s proponents note that it is more than a language: Itis designed to provide consistent ways to revise and reuseprogram components throughout the software developmentcycle. The current implementation of Eiffel is available forvirtually all platforms and has interfaces to C, C++, andother languages. This allows Eiffel to be used to create adesign framework for reusing existing software componentsin other languages. Eiffel’s consistent object-oriented designalso makes it useful for documenting or modeling softwareprojects (see modeling languages).Eiffel was developed around the same time as C++. Eiffelis arguably cleaner and superior in design to the latter language.However, two factors led to the dominance of C++:the ready availability of inexpensive or free compilers andthe existence of thousands of programmers who alreadyknew C. Eiffel ended up being a niche language used for

174 Electronic Artsteaching software design and for a limited number of commercialapplications using the EiffelStudio programmingenvironment.Eiffel has been recognized for its contributions to thedevelopment of object-oriented software design, mostrecently by the Association for Computing Machinery’s2006 Software System Award for Impact on SoftwareQuality.Further Reading“Eiffel in a Nutshell.” Available online. URL: http://archive.eiffel.com/eiffel/nutshell.html. Accessed September 19, 2007.Eiffel Zone. Available online. URL: http://eiffelzone.com/. AccessedSeptember 19, 2007.“Introduction to Eiffel” [Flash presentation]. Available online.URL: http://www.eiffel.com/developers/presentations/eiffel_introduction/player.html?slide=. Accessed September 19,2007.Meyer, Bertrand. Eiffel: The Language. Englewood Cliffs, N.J.:Prentice Hall, 1991.———. Object-Oriented Software Construction. 2nd ed. Upper SaddleRiver, N.J.: Prentice Hall, 2000.Wiener, Richard. An Object-Oriented Introduction to ComputerScience Using Eiffel. Upper Saddle River, N.J.: Prentice Hall,1996.Electronic ArtsElectronic Arts (NASDAQ symbol: ERTS) is a pioneeringand still prominent maker of games for personal computers(see computer games). Its fortunes largely mirror those ofthe game industry itself.In 1982 Trip Hawkins and several colleagues left AppleComputer and founded a company called Amazin’ Software.The company was founded with the goal of making“software that makes a personal computer worth owning.”Hawkins also had an ambitious goal of turning it into a billion-dollarcompany, but this goal would not be achieveduntil the mid-1990s. Meanwhile, after considerable internaldebate, the company changed its name to Electronic Arts inlate 1982. This name reflects Hawkins’s belief that computergames were an emerging art form and that their developersshould be respected as artists. This would be reflected ingame box covers that looked like record jackets and prominentlyfeatured the names of the developers.In 1983 EA published three games for the Atari 800computer that typified playability and diversity. Archoncombined chesslike strategy with arcade-style battles; PinballConstruction Set let users create and play their ownlayouts; and the unique M.U.L.E. was a deceptively simplegame of strategic resources—and one of the first multiplayervideo games. EA titles published in the later 1980sinclude an exploration game Seven Cities of Gold, the graphicallyinnovative space conquest game Starflight, and therole-playing series The Bard’s Tale.In its early years the company published games developedby independent programmers, but in the late 1980sit began to develop some games in house. EA sought outinnovative games and promoted them directly to retailers.While it was difficult at first to market often-obscure gamesto stores, as the games became successful and regular retailchannels were established, EA’s revenue began to outpacethat of competitors. (Hawkins left in 1991 to found thegame company 3DO.)Challenges and CriticismBy the 2000s EA, now under Larry Probst, had sufferedloss of its once-dominant position in what had becomean increasingly diverse industry. EA was criticized bysome investment analysts for declining to follow thetrend toward ultraviolent, M-rated games such as GrandTheft Auto, though the company later softened that stand.In recent years the company’s big sellers have been itsgraphically intense and realistic sports simulations, notablyJohn Madden Football. (Besides the NFL, EA has contractswith NASCAR, FIFA [soccer], and the PGA andTiger Woods.)In 2007 EA announced that it would come out withMacintosh versions of many of its top titles. However, criticshave noted that the company seems to be publishingfewer original titles in favor of yearly updates (particularlyin their sports franchises).Along with much of the game industry, EA has increasinglyfocused on console games (see game console). EAcurrently develops games for the leading consoles; in fact,about 43 percent of EA’s 2005 revenue came from salesfor the Sony PlayStation2 alone. (Total revenue in 2008was $4.02 billion.) EA has also been expanding into onlinegames, starting in 2002 with an online version of The Sims,a “daily life simulator.” (See online games.)Some critics have objected to EA’s practice of buyingsmaller companies in order to get control over their populargames, and then releasing versions that had not beenproperly tested. Perhaps the most-cited example is EA’sacquiring of Origin Systems and its famous Ultima series ofrole-playing games. Once acquired, EA produced two newtitles in the series that many gamers consider to not be upto the Ultima standard.The company has also been criticized for requiring verylong work hours from developers; it eventually settled suitsfrom game artists and programmers demanding compensationfor unpaid overtime.EA has shown continuing interest in promoting the professionof game development. In 2004 the company madea significant donation toward the development of a gamedesign and production program at the University of SouthernCalifornia.Meanwhile, founder Hawkins has founded a companycalled Digital Chocolate, focusing on games for mobiledevices.Further ReadingEA.com Web site. Available online. URL: http://www.ea.com.Accessed September 19, 2007.EA Sports Home Page. Available online. URL: http://www.easports.com/. Accessed September 19, 2007.“Mobile Games: Way beyond Phone Tag” [Interview with TripHawkins]. Business Week Online, April 3, 2006. Availableonline. URL: http://www.businessweek.com/technology/content/apr2006/tc20060403_840834.htm. Accessed September19, 2007.

electronic voting systems 175Waugh, Eric-Jon Rossel. “A Short History of Electronic Arts.” BusinessWeek Online, August 25, 2006. Available online. URL:http://www.businessweek.com/innovate/content/aug2006/id20060828_268977.htm. Accessed September 19, 2007.electronic voting systemsThere are a variety of ways to electronically register, store,and process votes. In recent years older manual systems(paper ballots or mechanical voting machines) have beenreplaced in many areas with systems ranging from purelydigital (touch screens) to hybrid systems where markedpaper ballots are scanned and tabulated by machine. However,voting systems have been subject to considerable controversy,particularly following the Florida debacle in the2000 U.S. presidential election.The criteria by which voting systems are evaluatedinclude:• how easy it is for the voter to understand and use thesystem• accessibility for disabled persons• whether the voter’s intentions are accurately recorded• the ability to make a permanent record of the vote• prevention of tampering (physical or electronic)• provisions for independent auditing of the votes incase of disputeThe degree to which a given system meets these criteriacan vary considerably because of both design and implementationissues.Early SystemsThe earliest form of voting system consisted of paper ballotsmarked and tabulated entirely by hand. The first generationof “automatic” voting systems involved mechanical votingmachines (where votes were registered by pulling levers).Next came two types of hybrid systems where votes werecast mechanically but tabulated automatically. These systemsused punch cards (see punched cards and papertape) or “marksense” or similar systems where the voterfilled in little squares and the ballots were then scannedand tabulated automatically.The ultraclose and highly disputed 2000 U.S. presidentialelection “stress-tested” voting systems that most peoplehad previously believed were reasonably accurate. The principalproblems were the interpretation of punch cards thatwere not properly punched through (so-called dimpled orhanging chads) and the fact that some ballot layouts provedto be confusing or ambiguous. Two types of voting systemshave been proposed as replacements for the problematicearlier technology.TouchscreenThis type of system uses a screen display that can bedirectly manipulated by the voter (see touchscreen). Inthe most common type, called DRE (direct-recording electronic),a computer program interprets and tabulates thevote as it is cast, storing an image in a removable memoryunit and (usually) printing out a copy for backup. After votingis complete, the memory module can be sent to the centralcounting office. (Alternatively, votes can be transmittedover a computer network in batches throughout the day.)In a few cases, voting has also been implemented throughsecure Internet sites.There are several types of electronic voting systems, such as this boxthat automatically tallies specially marked ballots. Common concernsinclude the potential for tampering and the need to provide for independentverification of results. (Lisa McDonald/istockphoto)Optical ScanConcern about potential tampering with computers has ledmany jurisdictions to begin to replace touchscreen systemswith optical-scan systems, where the voter marks a sturdypaper ballot. (About half of U.S. counties now use optical-scansystems.) The advantage of optical systems is thatthe voter physically marks the ballot and can see how heor she has voted, and after tabulation the physical ballotsare available for review in case of problems. However, optical-scanballots must be properly marked using the correcttype of pencil, or they may not be read correctly. Unlike thetouchscreen, it is not possible to give the voter immediatefeedback so that any errors can be corrected. Optical-ballotsystems may cost more because of paper and printing costsfor the ballots, which may have to be prepared in several

176 e-maillanguages. However this cost may be offset by not having todevelop or validate the more complicated software neededfor all-electronic systems.Whatever system is used, federal law requires that visuallyor otherwise disabled persons be given the opportunity,wherever possible, to cast their own vote in privacy.With optical-scan ballots, this is accommodated with a specialdevice that plays an audio file listing the candidatesfor each race, with the voter pressing a button to markthe choice. However, disability rights advocates have complainedthat existing systems still require that another personphysically insert the marked ballot into the scanner.Touchscreen systems, however, with the aid of audio cues,can be used by visually disabled persons without the needfor another person to be present. They are thus preferred bysome advocates for the disabled.Reforms and IssuesIn response to the problems with the 2000 election, Congresspassed the Help America Vote Act in 2002. Since then,the federal government has spent more than $3 billion tohelp states replace older voting systems—in many caseswith touchscreen systems.The biggest concern raised about electronic voting systemsis that they, like other computer systems, may be susceptibleto hacking or manipulation by dishonest officials.In 2007 teams of researchers at the University of California–Daviswere invited by the state to try to hack into itsvoting systems. For the test, the researchers were providedwith full access to the source code and documentation forthe systems, as well as physical access. The hacking teamswere able to break into and compromise every type of votingsystem tested. In their report, the researchers outlinedwhat they claimed to be surprisingly weak electronic andphysical security, including flaws that could allow hackersto introduce computer viruses and take over control of thesystems.Manufacturers and other defenders of the technologyhave argued that the testing was unrealistic and that realworldhackers would not have had nearly as much informationabout or access to the systems. (This may underestimatethe resourcefulness of hackers, as shown with other systems,such as the phone system and computer networks.)Another issue is who will be responsible for independentlyreviewing the programming (source) code for eachsystem to verify that it does not contain flaws. Manufacturersgenerally resist such review, considering the source codeto be proprietary. (A possible alternative might be an opensourcevoting system. Advocates of open-source softwareargue that it is safer precisely because it is open to scrutinyand testing—see open-source movement.)One common response to these security concerns is torequire that all systems generate paper records that can beverified and audited. Some defenders of existing technologysay that adding a parallel paper system is unnecessarilyexpensive and introduces other problems such as printerfailures. They argue that all-electronic systems can be madesafer and more secure, such as through the use of encryption.(A proposed compromise would be for the machine toprint out a simple receipt with a code that the voter coulduse to verify online that the vote was tabulated.)As of 2007, 28 states had passed laws requiring that votingsystems produce some sort of paper receipt or recordthat shows the voter what has been voted and that can beused later for an independent audit or recount,Although control of elections is primarily a state or localresponsibility, the federal government does have jurisdictionover elections for federal office. As a practical matter,any changes in voting technology or procedures mandatedby Congress for federal elections will end up being used inlocal elections as well.In 2007, congressional leaders decided not to require amajor overhaul of the nation’s election systems until at least2012. However, the inclusion of some sort of paper record isbeing mandated for the 2008 election. For users of touchscreensystems, the simplest way to accommodate this is toadd small paper-spool printers, but some states have complainedthat their systems would require more-expensiveaccommodations.Meanwhile, a lively debate continues in many states andother jurisdictions about how to meet the need for accessiblebut secure voting systems without breaking the budget.Further ReadingDrew, Christopher. “Accessibility Isn’t Only Hurdle in VotingSystem Overhaul.” New York Times, July 21, 2007. Availableonline. URL: http://www.nytimes.com/2007/07/21/washington/21vote.html. Accessed September 20, 2007.Open Voting Consortium. Available online. URL: http://www.openvotingconsortium.org/. Accessed September 20, 2007.Rubin, Aviel. Brave New Ballot: The Battle to Safeguard Democracyin the Age of Electronic Voting. New York: Morgan Road Books,2006.Saltman, Roy G. The History and Politics of Voting Technology: InQuest of Integrity and Public Confidence. New York: PalgraveMacmillan, 2006.United States Election Assistance Commission. “2005 VoluntaryVoting System Guidelines.” Available online. URL: http://www.eac.gov/voting%20systems/voting-system-certification/2005-vvsg. Accessed September 20, 2007.“Verified Voting: Mandatory Manual Audits of Voter-VerifiedPaper Records.” Available online. URL: http://www.verifiedvoting.org/. Accessed September 20, 2007.Wildemuth, John. “State Vote Machines Lose Test to Hackers.”San Francisco Chronicle, July 28, 2007, p. A-1. Availableonline. URL: http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/07/28/MNGP6R8TJO1.DTL. Accessed September 20,2007.e-mailElectronic mail is perhaps the most ubiquitous computerapplication in use today. E-mail can be defined as the sendingof a message to one or more individuals via a computerconnection.Development and ArchitectureThe simplest form of e-mail began in the 1960s as a way thatusers on a time-sharing computer system could post andread messages. The messages consisted of text in a file thatwas accessible to all users. A user could simply log into the

embedded system 177Instead, companies such as Microsoft and Google competeto offer full-featured e-mail programs that include grouporientedfeatures such as task lists and scheduling (see alsopersonal information manager).Transmission of an e-mail message depends on widely used protocolssuch as SMTP, which controls message format and processing,and POP3, which handles interaction between mail servers andclient programs. As long as the formats are properly followed, userscan employ a wide variety of mail programs (agents), and serviceproviders can use a variety of mail server programs.system, open the file, and look for messages. In 1971, however,the ARPANET (ancestor of the Internet—see internet)was used by researchers at Bolt Beranek and Newman(BBN) to send messages from a user at one computer to auser at another. The availability of e-mail helped fuel thegrowth of the ARPANET through the 1970s and beyond.As e-mail use increased and new features were developed,the question of a standardized protocol for messagesbecame more important. By the mid-1980s, the world ofe-mail was rather fragmented, much like the situation inthe early history of the telephone, where users often had tochoose between two or more incompatible systems. Apranet(or Internet) users used SMTP (Simple Mail Transport Protocol)while a competing standard (OSI MHS, or MessageHandling System) also had its supporters. Meanwhile, thedevelopment of consumer-oriented online services such asCompuServe and America Online threatened a further balkanizationof e-mail access, though systems called gatewayswere developed to transport messages from one system toanother.By the mid-1990s, however, the nearly universal adoptionof the Internet and its TCP/IP protocol had establishedSMTP and the ubiquitous Sendmail mail transport programas a uniform infrastructure for e-mail. The extension of theInternet protocol to the creation of intranets has largelyeliminated the use of proprietary corporate e-mail systems.E-mail TrendsThe integration of e-mail with HTML for Web-style formattingand MIME (for attaching graphics and multimediafiles) has greatly increased the richness and utility ofthe e-mail experience. E-mail is now routinely used withinorganizations to distribute documents and other resources.However, the addition of capabilities has also opened securityvulnerabilities. For example, Microsoft Windows andthe popular Microsoft Outlook e-mail client together providethe ability to run programs (scripts) directly fromattachments (files associated with e-mail messages). Thismeans that it is easy to create a virus program that will runwhen an enticing-looking attachment is opened. The viruscan then find the user’s mailbox and mail copies of itself tothe people found there. E-mail has thus replaced the floppydisk as the preferred medium for such mischief. (See computervirus.)Beyond security issues, e-mail is having considerablesocial and economic impact. E-mail has largely replacedpostal mail (and even long-distance phone calls) as a wayfor friends and relatives to keep in touch. As more companiesbegin to use e-mail for providing routine bills andstatements, government-run postal systems are seeing theirfirst-class mail revenue drop considerably. Despite the riskof viruses or deception and the annoyance of electronicjunk mail (see spam), e-mail has become as much a part ofour way of life as the automobile and the telephone.Further ReadingCostales, Bryan, and Eric Allman. Sendmail. 3rd ed. Sebastapol,Calif.: O’Reilly, 2002.Sendmail Consortium. Available online. URL: http://www.sendmail.org/. Accessed July 22, 2007.Shipley, David, and Will Schwalbe. Send: The Essential Guide toEmail for Office and Home. New York: Knopf, 2007.Song, Mike, Vicki Halsey, and Tim Burress. The Hamster Revolution:How to Manage Your Email Before It Manages You. SanFrancisco: Bennett-Koehler, 2007.embedded systemWhen people think of a computer, they generally think ofa general-purpose computing system housed in a separatebox, for use on the desk or as a laptop or hand-held device.However, the personal computer and its cousins are only thesurface of a hidden web of computing capability that reachesdeep into numerous devices used in our daily lives. Moderncars, for example, often contain several specialized computersystems that monitor fuel injection or enhance the car’s gripon the road under changing conditions. Many kitchen appliancessuch as microwaves, dishwashers, and even toasterscontain their own computer chips. Communications systemsranging from cell phones to TV satellite dishes includeembedded computers. Most important, embedded systemsare now essential to the operation of critical infrastructure

178 employment in the computer fieldBecause available memory is limited, embedded programcode tends to be compact. Since embedded systems areoften responsible for critical infrastructure, their operatingprograms must be carefully debugged. Designers tryto make programs “robust” so they can respond sensiblyto unexpected conditions or at least “fail gracefully” ina way least likely to cause damage. Other strategies toimprove the reliability of embedded systems include theuse of overdesigned, fault-tolerant components (as in themilitary “milspec”) and the use of separate, redundantsystems so that a failing system can be “locked out” andprocessing can continue elsewhere.An embedded system is a computer processor that is part of a“real-world” device that must interact with its environment. Sensorinputs (such as torque or pressure sensors) provide real-time dataabout conditions faced by the device (such as a vehicle). This datais processed by the onboard processor under the control of a permanent(ROM) program, and commands are issued to the effectorcontrols, which might, for example, apply braking pressure.such as medical monitoring systems and power transmissionnetworks. (The potential vulnerability of embedded systemsto the Y2K date-related problems was a major concern inthe months leading up to 2000, especially because manyembedded systems might have to be replaced rather thanjust reprogrammed. In the event, it turned out that therewere relatively few date-dependent systems and only minordisruptions were experienced. See y2k problem.)Characteristics of Embedded SystemsWhat most distinguishes an embedded system from a desktopcomputer is not that it is hidden inside some other device,but that it runs a single, permanent program whose job it isto monitor and respond to the environment in some way.For example, an oven controller would accept a user input(the desired temperature), monitor a sensor or thermostat,and control the heat to ensure that the correct temperatureis being maintained. Embedded systems are thus similar torobots in that they sense and manipulate their environment.Architecturally, an embedded system typically consists ofa microprocessor, some nonvolatile memory (memory that canmaintain its contents indefinitely), sensors (to receive readingsfrom the environment), signal processors (to convertinputs into usable information), and “effectuators” (switchesor other controls that the embedded system can use to changeits environment). In practice, an embedded system may nothave its own sensors or effectors, but instead interface withother systems (such as avionics or steering).Programmers of embedded systems often use specialcompilers or languages that are particularly suitedfor creating embedded software (see ada and forth).Further ReadingCatsoulis, John. Designing Embedded Hardware. 2nd ed. Sebastapol,Calif.: O’Reilly, 2005.Embedded.com: “Thinking inside the Box.” Available online. URL:http://www.embedded.com/. Accessed July 22, 2007.Embedded Systems. Dr. Dobb’s Portal. Available online. URL:http://www.ddj.com/dept/embedded/. Accessed July 22, 2007.Norergaard, Tammy. Embedded Systems Architecture: A ComprehensiveGuide for Engineers and Programmers. Burlington, Mass.:Newnes/Elsevier, 2005.Simon, David E. An Embedded Software Primer. Upper Saddle River,N.J.: Addison-Wesley/Pearson Education, 1999.employment in the computer fieldThe number of computer-related positions has grown rapidlyover the past few decades. According to the U.S. Bureauof Labor Statistics, by the mid-1990s the fastest-growingprofessions in the United States included systems analysts,computer scientists, and computer engineers. By the mid-2000s, computer-related occupations were still near the topof the list, which by then also included network and communicationsanalysts (second only to “home health aids”).Computer-related employment can be broken down intothe following general categories:• hardware design and manufacturing, including computersystems, peripherals, communications and networkhardware, and other devices• the software industry, ranging from business applicationsto consumer software, games, and entertainment• the administrative sector (systems administration,network administration, database administration,computer security, and so on)• the Web sector, including ISPs, Web hosts and pagedevelopers, and e-commerce applications• the support sector, including training and education,computer book publishing, technical support, andsystems repair and maintenanceIn addition to these “pure” computer-related jobs, thereare many other positions that involve working with PCs.These include word processing/desktop publishing, statistics,scientific research, accounting and billing, shipping,retail sales and inventory, and manufacturing. (See alsoprogramming as a profession.)

emulation 179Job Market ConsiderationsIn the late 1990s, a number of sources forecast a growinggap between the number of positions opening in computerrelatedfields and the number of new people entering thejob market (estimates of the gap’s size ranged into the hundredsof thousands nationally). Particularly in the Internetsector, demand for programmers and system administratorsmeant that new college graduates with basic skills couldearn unprecedented salaries, while experienced professionalscould often become highly paid consultants. Despite thegrowing emphasis on computing in secondary and highereducation, computer science and engineering candidateswere in particularly short supply. As a result, many companiesreceived permission to hire larger numbers of immigrantsfrom countries such as India.The “dot crash” of 2001–2002 saw a sharp if temporarydecline in demand for computer professionals, particularlyin the Web and e-commerce sectors, but it impacted hardwaresales as well. The industry then saw a resurgence, butwith an emphasis on somewhat different skill sets. Skills instrong demand toward the end of the 2000 decade include:• detection, prevention, and investigation of computerattacks (see computer crime and security and computerforensics)• improvements in operating system and softwaresecurity• use of open-source software and operating systems(see open-source movement and Linux)• surveillance and physical security (see biometrics)• transaction analysis for both security and marketingapplications (see data mining)• e-commerce applications and management (see customerrelationship management)• rapid development of efficient, highly interactive Webservices (see Ajax, Web 2.0 and beyond, and scriptinglanguages)• hardware and software for mobile and wireless devices(particularly delivery and integration of media)• content management for Web sites and media services• scientific computing, particularly genetic and biologicalapplications (see bioinformatics)On the other hand, with the successful passing of theY2K crisis, the outlook for mainframe programmers (particularlyusing COBOL) is increasingly dim. Prospects arealso poor for certain operating, network, and database systemswith declining market share (such as OS/2, Novellnetworking, and some older database systems). It is truethat as baby boomer programmers retire, there will besome demand for maintenance or conversion of obsolescentsystems. Finally, as global trends toward outsourcing andrelocating of lower-level support and even programmingcontinue, it may become harder for domestic workers tobegin to climb the IT ladder.Socially, the key challenges that must be met to ensurea healthy computer-related job market are the improvementof education at all levels (see education and computers)and the increasing of ethnic and gender diversity in thefield (which is related to the fostering of more equal educationalopportunity), and adapting to changes in the globaleconomy (see globalism and the computer industry).Further ReadingBrandel, Mary. “12 IT Skills that Employers Can’t Say No To.”Computerworld, July 11, 2007. Available online. URL: http://www.computerworld.com/action/article.do?command=viewArticleBasic&articleId=9026623. Accessed July 22, 2007.Farr, Michael. Top 100 Computer and Technical Careers. 3rd ed. St.Paul, Minn.: JIST Works, 2006.Henderson, Harry. Career Opportunities in Computers and Cyberspace.2nd ed. New York: Facts On File, 2004.Information Technology Jobs in America. New York: Info TechEmployment Publications, 2007.U.S. Department of Labor. Occupational Outlook Handbook,2006–07 edition. Available online. URL: http://www.bls.gov/oco/. Accessed July 22, 2007.Vocational Information Center. Computer Science Career Guide.Available online. URL: http://www.khake.com/page17.html.Accessed July 22, 2007.emulationOne consequence of the universal computer concept (seevon Neumann, John) is that in principle any computercan be programmed to imitate the operation of any other.An emulator is a program that runs on one computer butaccurately processes instructions written for another (seealso microprocessor and assembler). For example, fansof older computer games can now download emulationprograms that allow modern PCs to run games originallyintended for an Apple II microcomputer or an Atari gamemachine. Emulators allowing Macintosh and Linux users torun Windows programs have also achieved some success.In order to work properly, the emulator must set up asort of virtual model of the target microprocessor, includingappropriate registers to hold data and instructions and asuitably organized segment of memory. While carrying outinstructions in software rather than in hardware imposesa considerable speed penalty, if the processor of the emulatingPC is much faster than the one being emulated, theemulator can actually run faster than the original machine.An entire hardware and software environment can alsobe emulated; this is called a virtual machine. For example,programs such as VMware can be used to run Windows,Linux, and BSD UNIX, each in a separate “compartment”that appears to be a complete machine, with all the necessaryhardware drivers and emulated facilities.The term virtual machine can also refer to language suchas Java, where programs are first compiled into a platformindependentintermediate “byte code,” which is then runby a Java virtual machine that produces the instructionsneeded for a given platform.In the past, emulation was sometimes used to allow programmersto develop software for large, expensive mainframeswhile using smaller machines. Emulators can also

180 encapsulationconsist of a combination of specially-designed chips andsoftware, as in the case of the “IBM 360 on a chip” thatbecame available for the IBM PCs.The term emulation is also sometimes used to refer to aprogram that accurately simulates the operation of a hardwaredevice. For example, when printers that includedhardware for processing the PostScript typographical languagewere expensive, programs were developed that couldprocess the PostScript instructions in the PC itself and thensend the output as graphics to a less expensive printer.Further ReadingComparison of Virtual Machines. Wikipedia. Available online.URL: http://en.wikipedia.org/wiki/Comparison_of_virtual_machines. Accessed July 23, 2007.Smith, Jim, and Ravi Nair. Virtual Machines: Versatile Platformsfor Systems and Processes. San Francisco: Morgan Kaufmann,2005.VMware. Available online. URL: http://www.vmware.com. AccessedJuly 23, 2007.encapsulationIn the earliest programming languages, any part of a programcould access any other part simply by executing aninstruction such as “jump” or “goto.” Later, the concept ofthe subroutine helped impose some order by creating relativelyself-contained routines that could be “called” fromthe main program. At the time the subroutine is called, it isprovided with necessary data in the form of global variablesor (preferably) parameters, which are variable referencesor values passed explicitly when the subroutine is called.When the subroutine finishes processing, it may return valuesby changing global variables or changing the values ofvariables that were passed as parameters (see proceduresand functions).While an improvement over the totally unstructuredprogram, the subroutine mechanism has several drawbacks.If it is maintained as part of the main program code, oneprogrammer may change the subroutine while another programmeris still expecting it to behave as previously defined.If not properly restricted, variables within the subroutinemight be accessed directly from outside, leading to unpredictableresults. To minimize these risks, languages such asC and Pascal allow variables to be defined so that they are“local”—that is, accessible only from code within the functionor procedure. This is a basic form of encapsulation.The class mechanism in C++ and other object-orientedlanguages provides a more complete form of encapsulation(see object-oriented programming, class, and C++). Aclass generally includes both private data and procedures ormethods (accessible only from within the class) and publicmethods that make up the interface. Code in the main programuses the class interface to create and manipulate newobjects of that class.Encapsulation thus both protects code from uncontrolledmodification or access and hides information (details) thatprogrammers who simply want to use functionality don’tneed to know about. Thus, high-quality classes can bedesigned by experts and marketed to other developers whocan take advantage of their functionality without having to“reinvent the wheel.”Further ReadingBerard, Edward V. “Abstraction, Encapsulation, and InformationHiding.” Available online. URL: http://www.itmweb.com/essay550.htm. Accessed July 23, 2007.Booch, G. Object-Oriented Analysis and Design with Applications.3rd ed. Upper Saddle River, N.J.: Addison-Wesley, 2007.Müller, Peter. “Introduction to Object-Oriented ProgrammingUsing C++.” Available online. URL: http://www.gnacademy.org/uu-gna/text/cc/Tutorial/tutorial.html. Accessed August14, 2007.Poo, Danny, and Derek Kiong. Object-Oriented Programming andJava. 2nd ed. New York: Springer-Verlag, 2007.encryptionThe use of encryption to disguise the meanings of messagesgoes back thousands of years (the Romans, for example,used substitution ciphers, where each letter in a messagewas replaced with a different letter). Mechanical ciphermachines first came into general use in the 1930s. DuringWorld War II the German Enigma cipher machineused multiple rotors and a configurable plugboard to createa continuously varying cipher that was thought to beunbreakable. However, Allied codebreakers built electromechanicaland electronic devices that succeeded in exploitingflaws in the German machine (while incidentally advancingcomputing technology). During the cold war Western andSoviet cryptographers vied to create increasingly complexcryptosystems while deploying more powerful computersto decrypt their opponent’s messages.In the business world, the growing amount of valuableand sensitive data being stored and transmitted on computersby the 1960s led to a need for high-quality commercialencryption systems. In 1976, the U.S. National Bureau ofStandards approved the Data Encryption Standard (DES),which originally used a 56-bit key to turn each 64-bitchunk of message into a 64-bit encrypted ciphertext. DESrelies upon the use of a complicated mathematical functionto create complex permutations within blocks and charactersof text. DES has been implemented on special-purposechips that can encrypt millions of bytes of message persecond.Public-Key CryptographyTraditional cryptosystems such as DES use the same key toencrypt and decrypt the message. This means that the keymust be somehow transmitted to the recipient before thelatter can decode the message. As a result, security may becompromised. However, the same year DES was officiallyadopted, Whitfield Diffie and Martin Hellman proposed avery different approach, which became known as publickeycryptography. In this scheme each user has two keys, aprivate key and a public key. The user publishes his or herpublic key, which enables any interested person to send theuser an encrypted message that can be decrypted only byusing the user’s private key, which is kept secret. The systemis more secure because the private key is never trans-

encryption 181Public key encryption allows users to communicate securely withouthaving to exchange their private keys. In part 1, person Apublishes a public key, which can be used by anyone else (such asperson B) to encrypt a message that only person A can read. In part2, person A encrypts a message with his or her private key. Sincethis message can only be encrypted using person A’s public key, personB can use the published public key to verify that the message isindeed from person A.mitted. Further, a user can distribute a message encryptedwith his or her private key that can be decrypted only withthe corresponding public key. This provides a sort of signaturefor authenticating that a message was in fact created byits putative author.In 1978, Ron Rivest, Adi Shamir, and Leonard Adelmanannounced the first practical implementation of public-keycryptography. This algorithm, called RSA, became the prevailingstandard in the 1980s. While keys may need to belengthened as computer power increases, RSA is likely toremain secure for the foreseeable future.Legal ChallengesUntil the 1990s, the computer power required for routineuse of encryption was generally beyond the reach of mostsmall business and consumer users, and there was littleinterest in a version of the RSA algorithm for microcomputers.Meanwhile, the U.S. federal government tried to maintaintight controls over encryption technology, includingprohibitions on the export of encryption software to manyforeign countries.However, the growing use of electronic mail and thehosting of commerce on the Internet greatly increased concernabout security and the need to implement an easy-touseform of encryption. In 1990, Philip Zimmermann wrotean RSA-based email encryption program that he calledPretty Good Privacy (PGP). However, RSA, Inc. refused togrant him the necessary license for its distribution. Further,FBI officials and sympathetic members of Congress seemedpoised to outlaw the use of any form of encryption that didnot include a provision for government agencies to decodemessages.Believing that people’s liberty and privacy were at stake,Zimmermann gave copies of PGP to some friends. The programsoon found its way onto computer bulletin boards,and then spread worldwide via Internet newsgroups andftp sites. Zimmermann then developed PGP 2.0, whichoffered stronger encryption and a modular design thatmade it easy to create versions in other languages. TheU.S. Customs Department investigated the distribution ofPGP but dropped the investigation in 1996 without bringingcharges. (At about the same time a federal judge ruledthat mathematician Daniel Bernstein had the right to publishthe source code for an encryption algorithm withoutgovernment censorship.)Government agencies eventually realized that theycould not halt the spread of PGP and similar programs. Inthe early 1990s, the National Security Agency (NSA), thenation’s most secret cryptographic agency, proposed thatstandard encryption be provided to all PC users in the formof hardware that became known as the Clipper Chip. However,the hardware was to include a “back door” that wouldallow government agencies and law enforcement (presumablyupon fulfilling legal requirements) to decrypt any message.Civil libertarians believed that there was far too muchpotential for abuse in giving the government such power,and a vigorous campaign by privacy groups resulted in themandatory Clipper Chip proposal being dropped by themid-1990s in favor of a system called “key escrow.” Thissystem would require that a copy of each encryption keybe deposited with one or more trusted third-party agencies.The agencies would be required to divulge the key if presentedwith a court order. However, this proposal has beenmet with much the same objections that had been madeagainst the Clipper Chip.In the early 21st century, the balance is likely to continueto favor the code-makers over the code-breakers.While it is rumored that the NSA can use arrays of supercomputersto crack any encrypted message given enoughtime, and a massive eavesdropping system called Echelonfor analyzing message traffic has been partially revealed, asa practical matter most of the world now has access to highqualitycryptography. Only radically new technology (seequantum computing) is likely to reverse this trend.Further ReadingCobb. Chey/ Cryptography for Dummies. Hoboken, N.J.: John Wiley& Sons, 2004.Henderson, Harry. Privacy in the Information Age (Library in aBook) 2nd ed. New York: Facts On File, 2006.“The International PGP Home Page.” Available online. URL: http://www.pgpi.org/. Accessed February 2, 2008.Levy, Stephen. Crypto. New York: Viking, 2001.Singh, Simon. The Code Book: the Science of Secrecy from Ancient Egyptto Quantum Cryptography. New York: Anchor Books, 2000.

182 Engelbart, DouglasEngelbart, Douglas(1925– )AmericanComputer EngineerDouglas Engelbart invented key elements of today’s graphicaluser interface, including the use of windows, hypertextlinks, and the ubiquitous mouse. Engelbart grew up ona small farm near Portland, Oregon, and acquired a keeninterest in electronics. His electrical engineering studiesat Oregon State University were interrupted by wartimeservice in the Philippines as a radar technician. During thattime he read a seminal article by Vannevar Bush entitled“As We May Think.” Bush presented a wide-ranging visionof an automated, interlinked text system not unlike thedevelopment that would become hypertext and the WorldWide Web (see Bush, Vannevar).After returning to college for his Ph.D. (awarded in1955), Engelbart worked for NACA (the predecessor ofNASA) at the Ames Laboratory. Continuing to be inspiredby Bush’s vision, Engelbart conceived of a computer displaythat would allow the user to visually navigate throughinformation displays. Engelbart received his doctorate inelectrical engineering in 1955 at the University of California,Berkeley, taught there a few years, and then went tothe Stanford Research Institute (SRI), a hotbed of futuristicideas. In 1962, Engelbart wrote a seminal paper ofhis own, titled “Augmenting Human Intellect: A ConceptualFramework.” In this paper Engelbart emphasized thecomputer not as a mere aid to calculation, but as a toolthat would enable people to better visualize and organizecomplex information to meet the increasing challenges ofthe modern world. The hallmark of Engelbart’s approachto computing would continue to be his focus on the centralrole played by the user.In 1963, Engelbart left SRI and formed his own researchlab, the Augmentation Research Center. During the 1960sand 1970s, he worked on implementing linked text systems(see hypertext and hypermedia). In order to help usersinteract with the computer display, he came up with theidea of a device that could be moved to control a pointeron the screen. Soon called the “mouse,” the device wouldbecome ubiquitous in the 1980s.Engelbart also took a key interest in the developmentof the ARPANET (ancestor of the Internet) and adapted hisNLS hypertext system to help coordinate network development.(However, the dominant form of hypertext on theInternet would be Tim Berners-Lee’s World Wide Web—(seeBerners-Lee, Tim.) In 1989, Engelbart founded the BootstrapInstitute, an organization dedicated to improving thecollaboration within organizations, and thus their performance.During the 1990s, this nurturing of new businessesand other organizations would become his primary focus.Engelbart received the MIT-Lemuelson Award and thea.m. Turing Award in 1997 and the National Medal of Technologyin 2000. Public recognition of Engelbart’s work andideas about human-computer interaction was also reflectedin a Stanford University symposium called “Engelbart’sUnfinished Revolution.”Further ReadingBardini, Thierry. Bootstrapping: Douglas Engelbart, Coevolution,and the Origins of Personal Computing. Stanford, Calif.: StanfordUniversity Press, 2000.Bootstrap Institute. Available online. URL: http://www.bootstrap.org. Accessed July 23, 2007.“Engelbart’s Unfinished Revolution.” Stanford University Symposium.Available online. URL: http://www.itmweb.com/essay550.htm. Accessed July 23, 2007.“Internet Pioneers: Doug Engelbart.” Available online. URL: http://www.ibiblio.org/pioneers/Engelbart.html. Accessed April 18,2008.Engelberger, Joseph(1925– )AmericanEntrepreneur, RoboticistJoseph Engelberger and George Devol created the first industrialrobot, revolutionizing the assembly line. Engelbergerwent on to develop other robots that can work in hospitalsand other settings while tirelessly promoting industrialrobotics.Engelberger was born on July 26, 1925, in New YorkCity. During World War II he was selected for a special programwhere promising students were paid to study physicsat Columbia University. Just after the war he worked asan engineer on early nuclear tests in the Pacific. He alsoworked on aerospace and nuclear power projects. After completinghis military duties, Engelberger attended ColumbiaUniversity’s School of Engineering and earned B.S. (1946)and M.S. degrees in physics and electrical engineering. Thissolid background in science and engineering would shapeEngelberger’s practical approach to robot design.A number of technologies of the 1940s and 1950s contributedto the later development of robotics. The war hadgreatly increased the development of automatic controlsand servomechanisms that allow for precise positioning andmanipulation of machine parts. The rise of nuclear powerand the need to safely handle radioactive materials alsospurred the development of automatic controls. Engelbergerbegan to develop business ventures in the automation field,starting a company called Consolidated Controls.In the mid-1950s Engelberger met George Devol, an inventorwho had patented a programmable transfer machine. Thiswas a device that could automatically move components fromone specified position to another, such as in a die-castingmachine that formed parts for automobiles. Engelbergerrealized that Devol’s machine could, with some additionalextensions and capabilities, become a robot that could beprogrammed to work on an assembly line.In 1956 Engelberger and Devol founded Unimate, Inc.—the world’s first industrial robot company. Their robot,also called Unimate, is essentially a large “shoulder” andarm. The shoulder can move along a track to position thearm near the materials to be manipulated. The arm can beequipped with a variety of specialized grasping “hands” tosuit the task. The robot is programmed to perform a set ofrepetitive motions. It is also equipped with various devices

enterprise computing 183for aligning the workpiece (the object to be manipulated)and to make small adjustments for variations.In spring 1961 the first Unimate robot began operationson the assembly line at the General Motors Plant inTurnstedt, a suburb of Trenton, New Jersey. Most of thefactory’s 3,000 human workers welcomed the newcomerbecause Unimate would be doing a job involving the castingof car doors and other parts from molten metal—hot,dangerous work. That first Unimate worked for nearly 10years, tirelessly keeping up with three shifts of humanworkers each day.In 1980 Engelberger published Robotics in Practice. Thisbook, together with Robotics in Service (1988), became astandard textbook that defined the growing robotics industry.The two titles also marked a shifting of Engelberger’sfocus from industrial robots to service robots—robots thatwould do their jobs not in factories, but in workplaces suchas warehouses or hospitals.In the 1980s Engelberger founded HelpMate Robotics,Inc. The company’s most successful product has been theHelpMate robot. The robot is designed to dispatch records,laboratory samples, and supplies throughout a busy hospital.HelpMate does not follow a fixed track. Rather, it isprogrammed to visit a succession of areas or stations andmakes its own way, using cameras to detect and go aroundobstacles. HelpMate can even summon an elevator to go toa different floor!Along with other robotics entrepreneurs, Engelbergeris also looking toward a time when robots will be able toperform a number of useful tasks in the home. In particular,Engelberger sees great potential for robots in helpingto care for the growing population of elderly people whoneed assistance in the tasks of daily life. He points out thatno government or insurance company can afford to hire afull-time human assistant to enable older people to continueto live at home. However, a suitable robot could fetchthings, remind a person when it is time to take medication,and even perform medical monitoring and summon help ifnecessary.Joseph Engelberger’s achievements in industrial and servicerobotics have won him numerous plaudits and awardsfrom the industry. He has also received honorary doctoratesfrom five institutions, including Carnegie Mellon Universityin Pittsburgh—one of the great centers of robotics researchin the United States.Since 1977, the Robotics Industries Association has presentedthe annual Joseph F. Engelberger Award to honor themost significant innovators in the science and technologyof robotics. Engelberger was elected to the National Academyof Engineering in 1984. He also received the ProgressAward of the Society of Manufacturing Engineers andthe Leonardo da Vinci Award of the Society of MechanicalEngineers, as well as the 1982 American Machinist Award.In 1992 Engelberger was included in the London SundayTimes series on “The 1000 Makers of the 20th Century.”Japan has awarded him the Japan Prize for his key role inthe establishment of that nation’s thriving robotics industry.In 2000 Engelberger delivered the keynote address tothe World Automation Congress, which was also dedicatedto him. In 2004 he received the IEEE Robotics and AutomationAward.Further ReadingBrain, Marshall. “Robotic Nation.” Available online. URL: http://marshallbrain.com/robotic-nation.htm. Accessed May 3,2007.Engelberger, Joseph F. Robotics in Practice: Management and Applicationsof Industrial Robots. New York: AMACOM, 1980.———. Robotics in Service. Cambridge, Mass.: MIT Press, 1989.———. “Whatever Became of Robotics Research.” Robotics Online.http://www.roboticsonline.com/public/articles/articlesdetails.cfm?id=769. Accessed May 3, 2007.Henderson, Harry. Modern Robotics: Building Versatile Machines.New York: Chelsea House, 2006.Nof, Shimon Y. Handbook of Industrial Robotics. 2nd ed. New York:Wiley, 1999.Robotics Online. Available online. URL: http://www.roboticsonline.com/. Accessed May 3, 2007.enterprise computingThis concept refers to the organization of data processingand communications across an entire corporation or otherorganization. Historically, computing technology and infrastructureoften developed at different rates in the variousdepartments of a corporation. For example, by the 1970s,departments such as payroll and accounting were makingheavy use of electronic data processing (EDP) using mainframecomputers. The introduction of the desktop computerin the 1980s often resulted in operations such as marketing,corporate communications, and planning being conductedusing a disparate assortment of software, databases, anddocument repositories. Even the growing use of networkingoften meant that an enterprise had several different networkswith at best rudimentary intercommunication.The movement toward enterprise computing, while oftenfunctioning as a buzzword for the selling of new networkingand knowledge management technology, conveys a realneed both to manage and leverage the growing informationresources used by a large-scale enterprise. The infrastructurefor enterprise computing is the network, which todayis increasingly built using Internet protocol (see tcp/ip),although legacy networks must often still be supported.Enterprise-oriented software uses the client-server model,with an important decision being which operating systemsto support (see client-server computing).The need for flexibility in making data available acrossthe organization is leading to a gradual shift from the olderrelational database (RDBMs) to object-oriented databases(OODBMs). One advantage of object-oriented databases isthat it is more scalable (able to be expanded without runninginto bottlenecks) and data can be distributed dynamicallyto take advantage of available computing resources.(An alternative is the central depository. See data warehouse.)The dynamic use of storage resources is also important(see disk array).The payoffs for a well-integrated enterprise informationsystem go beyond efficiency in resource utilization andinformation delivery. If, for example, the marketing departmenthas full access to data about sales, the data can be

184 entrepreneurs in computinganalyzed to identify key features of consumer behavior (seedata mining).Further ReadingBernard, Scott A. An Introduction to Enterprise Architecture Planning.2nd ed. Bloomington, Ind.: AuthorHouse, 2005.Blanding, Steve, ed. Enterprise Operations Management Handbook.2nd ed. Boca Raton, Fla.: CRC Press, 1999.Carbone, Jane. IT Architecture Toolkit. Upper Saddle River, N.J.:Prentice Hall PTR, 2004.Zachman Institute for Framework Advancement. Available online.URL: http://www.zifa.com/. Accessed July 29, 2007.entrepreneurs in computingMuch publicity has been given to figures such as Microsoftfounder and multibillionaire Bill Gates, who turned avest-pocket company selling BASIC language tapes into thedominant seller of operating systems and office software forPCs. Historically, however, the role of key entrepreneurs inthe establishment of information technology sectors repeatsthe achievements of such 19th- and early 20th-centurytechnology pioneers as Thomas Edison and Henry Ford.There appear to be certain times when scientific insight andtechnological capability can be translated into businessesthat have the potential to transform society while makingthe pioneers wealthy.Like their counterparts in earlier industrial revolutions,the entrepreneurs who created the modern computerindustry tend to share certain common features. In positiveterms one can highlight imagination and vision suchas that which enabled J. Presber Eckert and John Mauchlyto conceive that the general-purpose electronic computercould find an essential place in the business and scientificworld (see Eckert, J. Presper and Mauchly, John). Inthe software world, observers point to Bill Gates’s intensefocus and ability to create and market not just an operatingsystem but also an approach to computing that wouldtransform the office (see Gates, William, III). The Internetrevolution, too, was sparked by both an “intellectual entrepreneur”such as Tim Berners-Lee, inventor of the WorldWide Web (see Berners-Lee, Tim) and by Netscape foundersMark Andreessen and Jim Clark, who turned the Webbrowser into an essential tool for interacting with informationboth within and outside of organizations.While technological innovation is important, the abilityto create a “social invention”—such as a new vehicle or planfor doing business, can be equally telling. At the beginningof the 21st century, the World Wide Web, effectively lessthan a decade old, is seeing the struggle of entrepreneurssuch as Amazon.com’s Jeff Bezos, eBay’s Pierre Omidyar,and Yahoo!’s Jerry Yang to expand significant toeholds inthe marketing of products and information into sustainablebusinesses.Historically, as industries mature, the pure entrepreneurtends to give way to the merely effective CEO. Inthe computer field, however, it is very hard to sort out thewaves of innovation that seem to follow close upon oneanother. Some sectors, such as the selling of computer systems(a sector dominated by entrepreneurs such as MichaelDell [Dell Computers] and Compaq’s Rod Canion) seem tohave little remaining scope for innovation. In other sectors,such as operating systems (an area generally dominatedby Microsoft), an innovator such as Linus Torvalds (developerof Linux) can suddenly emerge as a viable challenger.And as for the Internet and e-commerce, it is too early totell whether the pace of innovation has slowed and theshakeout now under way will lead to a relatively stablelandscape. (Note: a number of other biographies of computerentrepreneurs are featured in this book. For example,see Andreessen, Marc; Bezos, Jeffrey P.; Engelberger,Joseph; Moore, Gordon E.; and Omidyar, Pierre.)Further ReadingCringely, R. X. Accidental Empires. New York: Harper, 1997.Henderson, Harry. A to Z of Computer Scientists. New York: FactsOn File, 2003.———. Communications and Broadcasting. (Milestones in Scienceand Invention). New York: Chelsea House, 2006.Jager, Rama Dev and Rafael Ortiz. In the Company of Giants. NewYork: McGraw-Hill, 1997.Malone, Michael S. Betting It All: The Technology Entrepreneurs.New York: Wiley, 2001.———. The Valley of Heart’s Delight: A Silicon Valley Notebook,1963–2001. New York: Wiley, 2001.Reid, R. H. Architects of the Web. New York: John Wiley, 1997.Spector, Robert. amazon.com: Get Big Fast. New York: Harper-Business,2000.enumerations and setsIt is sometimes useful to have a data structure that holdsspecific, related data values. For example, if a program is toperform a particular action for data pertaining to each dayof the week, the following Pascal code might be used:type Day is (Monday, Tuesday, Wednesday,Thursday, Friday, Saturday, Sunday)Such a data type (which is also available in Ada, C, andC++) is called an enumeration because it enumerates, or“spells out” each and every value that the type can hold.Once the enumeration is defined, a looping structurecan be used to process all of its values, as in:var Today: Day;for Today: = Monday to Sunday do (some statements)Pascal, C, and C++ do not allow the same item to beused in more than one enumeration in the same name space(area of reference). Ada, however, allows for “overloading”with multiple uses of the same name. In that case, however,the name must be qualified by specifying the enumerationto which it belongs, as in:If Day = Days (‘Monday’) . . .As far as the compiler is concerned, an enumerationvalue is actually a sequential integer. That is, Monday = 0,Tuesday = 1, and so on. Indeed, built-in data types such asBoolean are equivalent to enumerations (false = 0, true =1) and in a sense the integer type itself is an enumeration

ergonomics of computing 185consisting of 0, 1, 2, 3, . . . and their negative counterparts.Pascal also includes built-in functions to retrieve the precedingvalue in the enumeration (pred), the following element(succ), or the numeric position of the current element(ord).The main advantage of using explicit enumerations isthat a constant such as “Monday” is more understandableto the program’s reader than the value 0. Enumerations arefrequently used in C and C++ to specify a limited groupof items such as flags indicating the state of device or fileoperation.Unlike most other languages Pascal and Ada also allowfor the definition of a subrange, which is a sequential portionof a previously defined enumeration. For example, oncethe Day type has been defined, an Ada program can definesubranges such as:subtype Weekdays is Days range Monday . .Friday;subtype Weekend is Days range Saturday . .Sunday;SetsThe set type (found only in Pascal and Ada) is similar to anenumeration except the order of the items is not significant.It is useful for checking to see whether the item being consideredbelongs to a defined group. For example, instead ofa program checking whether a character is a vowel as follows:if (char = ‘a’) or (char = ‘e’) or (char = ‘i’)or (char = ‘o’) or (char = ‘u’) . . .the program can define:type Vowels = (a, e, i, o, u);if char in Vowels . . .Further ReadingSebesta, Robert W. Concepts of Programming Languages. 8th ed.Boston: Pearson, 2007.ergonomics of computingErgonomics is the study of the “fit” between people andtheir working environment. Because computers are sucha significant part of the working life of so many people,finding ways for people to maximize efficiency and reducehealth risks associated with computer use is increasinglyimportant.Since the user will be looking at the computer monitorfor hours on end, it is important that the display be largeenough to be comfortably readable and that there be enoughcontrast. Glare on the monitor surface should be avoided.It is recommended that the monitor be placed so that thetop line of text is slightly below eye level. A distance ofabout 18 inches to two feet (roughly arm’s length) is recommended.There has been concern about the health effects ofelectromagnetic radiation generated by monitors. Most newmonitors are designed to have lower emissions.While the “standard” keyboard has changed little in20 years of desktop computing, there have been attemptsat innovation. One, the Dvorak keyboard, uses an alternativearrangement of letters to the standard “QWERTY.”Although it is a more logical arrangement from the point ofview of character frequency, studies have generally failedto show sufficient advantage that would compensate forthe effort of retraining millions of typists. There have alsobeen specially shaped “ergonomic” keyboards that attemptto bring the keys into a more natural relationship with thehand (see keyboard).The use of a padded wrist rest remains controversial.While some experts believe it may reduce strain on the armand neck, others believe it can contribute to Carpal TunnelSyndrome. This injury, one of the most serious repetitivestress injuries (RSIs), is caused by compression of a nervewithin the wrist and hand.Because of reliance on the mouse in many applications,experts suggest selecting a mouse that comfortably fits thehand, with the buttons falling “naturally” under the fingers.When moving the mouse, the forearm, wrist, and fingersshould be kept straight (that is, in line with the mouse).Some people may prefer the use of an alternative pointingdevice (such as trackball or “stub” within the keyboarditself, often found in laptop computers).A variety of so-called ergonomic chairs of varying qualityare available. Such a chair can be a good investment inworker safety and productivity, but for best results the chairmust be selected and adjusted after a careful analysis ofthe individual’s body proportions, the configuration of theworkstation, and the type of applications being used. Ingeneral, a good ergonomic chair should have an adjustableseat and backrest and feel stable rather than rickety.The operating system and software in use are alsoimportant. Providing clear, legible text, icons or othercontrols and a consistent interface will contribute to theuser’s overall sense of comfort, as well as reducing eyestrain.It is also important to try to eliminate unnecessaryrepetitive motion. For example, it is helpful to provideshortcut key combinations that can be used instead of aseries of mouse movements. Beyond specific devices, thedevelopment of an integrated design that reduces stressand improves usability is part of what is sometimes calledhuman factors research.In March 2001, President Bush cancelled new OSHAstandards that would have further emphasized reportingand mitigating repetitive stress and musculo-skeletal disorders(MSDs). However, the legal and regulatory climateis likely to continue to place pressure on employers to takeergonomic considerations into account.Further ReadingCoe, Marlana. Human Factors for Technical Communicators. NewYork: Wiley, 1996.Dul, Jan, and Bernard Weerdmeester. Ergonomics for Beginners:A Quick Reference Guide. 2nd ed. Grand Rapids, Mich.: CRCPress, 2001.“Ergonomic Design for Computer Workstations.” Available online.URL: http://www.ergoindemand.com/computer-workstationergonomics.htm.Accessed July 30, 2007.

186 error correctionSalvendy, Gavriel. Handbook of Human Factors and Ergonomics. 3rded. New York: Wiley, 2006.U.S. Department of Labor. Occupational Safety & Health Administration.“Computer Workstations.” Available online. URL:http://www.osha.gov/SLTC/etools/computerworkstations/index.html. Accessed July 30, 2007.Vredenberg, Karel, Scott Isensee, and Carol Righi. User-CenteredDesign: an Integrated Approach. Upper Saddle River, N.J.:Prentice Hall, 2001.For even parity, if the number of ones in the byte is odd, the paritybit is set to one to make the total number of ones even. Odd paritywould work the same way, except the parity bit would be set whennecessary to ensure an odd number of ones.error correctionTransmitting data involves the sending of bits (ones andzeros) as signaled by some alternation in physical characteristics(such as voltage or frequency). There are a numberof ways in which errors can be introduced into the datastream. For example, electrical “noise” in the line might beinterpreted as spurious bits, or a bit might be “flipped” fromone to zero or vice versa. Generally speaking, the faster therates at which bits are being sent, the more sensitive thetransmission is to effects that can cause errors.While a few wrong characters might be tolerated insome text messages or graphics files, binary files representingexecutable programs must generally be received perfectly,since random changes can make programs fail orproduce incorrect results. Data communications engineershave devised a number of methods for checking the accuracyof data transmissions.The simplest scheme is called parity. A single bit isadded to each eight-bit byte of data. In even parity, theextra (parity) bit is set to one when the number of ones inthe byte is odd. In odd parity, a one is added if the data bytehas an even number of ones. This means that the receiver ofthe data can expect it to be even or odd respectively. Whenthe byte arrives at its destination, the receiving programchecks the parity bit and then counts the number of onesin the rest of the byte. If, for example, the parity is evenbut the data as received has an odd number of ones, thenat least one of the bits must have been changed in error.Parity is a fast, easy way to check for errors, but it has someunreliability. For example, if there were two errors in transmissionsuch that a one became a zero and a different zerobecame a one, the parity would be unchanged and the errorwould not be detected.The checksum method offers greater reliability. Thebinary value of each block of data is added and the sumis sent along with the block. At the destination, the bits inthe block are again added to see if they still match the sum.A variation, the cyclical redundancy check or CRC, breaksthe data into blocks and divides them by a fixed number.The remainder for the division for each block is appendedto the block and the calculation is repeated and checked atthe destination. Today most modem control software implementsparity or CRC checking.A more sophisticated method called the Hamming Codeoffers not only high reliability but also the ability to automaticallycorrect errors. In this scheme the data and checkbits are encrypted together to create a code word. If theword received is not a valid code word, the receiver can usea series of parity checks to find the original error. Increasingthe ratio of redundant check bits to message bits improvesthe reliability of the code, but at the expense of having todo more processing to encrypt that data and requiring moretime to transmit it.Further Reading“Error-Correcting Code.” Wolfram MathWorld. Available online.URL: http://mathworld.wolfram.com/Error-CorrectingCode.html. Accessed July 31, 2007.Fung, Francis Yein Chei. “A Survey of the Theory of Error-CorrectingCodes.” Available online. URL: http://cadigweb.ew.usna.edu/~wdj/teach/ecc/codes.html. Accessed July 31, 2007.Wicker, S. B. Error Control Systems for Digital Communication andStorage. Upper Saddle River, N.J.: Prentice Hall, 1995.error handlingAn important characteristic of quality software is its abilityto handle errors that arise in processing (also calledrun-time errors or “exceptions”). Before it is released forgeneral use, a program should be thoroughly tested witha variety of input (see quality assurance, software).When errors are found, the soundness of the algorithm andits implementation must be checked, as well as the programlogic (see algorithm). Interaction between the programand other programs (including the operating system) aswell as with hardware must also be considered. (See bugsand debugging.)However, even well-tested software is likely to encountererrors. Therefore a program intended for widespread usemust include instructions for dealing with errors, anticipatedor otherwise. The process of error handling can bedivided into four stages: validation, detection, communication,and amelioration.Data validation is the first line of defense. At the “frontend” of the program, data being entered by a user (or readfrom a disk file or communications link) is checked to seewhether it falls within the prescribed parameters. (In thecase of a program such as a data management system, theuser interface plays an important role. Data input fieldscan be designed so that they accept only valid characters.

expert systems 187On-line help and error messages can explain to users why aparticular input is invalid.)However, data validation can ensure only that data fallswithin the generally acceptable parameters. Some particularcombination or context of data might still be erroneous,and calculations performed within the program can alsoproduce errors. Some examples include a divisor becomingzero (not allowable mathematically) or a number overflowingor underflowing (becoming too large or too small forregister or memory space allotted for it).Error communication is generally handled by a set oferror codes (special numeric values) returned to the mainprogram by the function used to perform the calculation.In addition, errors that arise in file processing (such as “filenot found”) also return error codes. For example, supposethere is a division function in C++double Quotient(double dividend, doubledivisor) throw(ZERODIV){if (0.0 == divisor)throw ZERODIV();return dividend / divisor;}In C++ “throw” means to post an error that can be“caught” by the appropriate error-handling routine. Thus,the corresponding “catch” code might have:catch( ZERODIV ){cout

188 expert systemsAnatomy of an Expert SystemAn expert system has two main components, a knowledge baseand an inference engine. The knowledge base consists of a setof assertions (facts) or of rules expressed as if . . . then statementsthat specify conditions that, if true, allow a particularinference to be drawn (see prolog). The inference engineaccepts new assertions or queries and tests them against thestored rules. Because satisfying one rule can create a conditionthat is to be tested by a subsequent rule, chains of reasoningcan be built up. If the reasoning is from initial factsto an ultimate conclusion, it is called forward chaining. If aconclusion is given and the goal is to prove that conclusion,there can be backward chaining from the conclusion to theassertions (similar to axioms in mathematical proofs).While some rules are ironclad (for example, if a closedstraight figure has three sides, it’s a triangle) in many realworldapplications it is necessary to take a probabilisticapproach. For example, experience might suggest that if acustomer buys reference books there is a 40 percent chancethe customer will also buy a related CD-ROM product.Thus, rules can be given weights or confidence factors and asthe rules are chained, a cumulative probability for the conclusioncan be generated and some threshold probabilityfor asserting a conclusion can be specified. (See also fuzzylogic and uncertainty).While rules-based inference systems are relatively easyto traverse automatically, they may lack the flexibility tocodify the knowledge needed for complex activities (such asautomatic analysis of news stories). An alternative approachinvolves the construction of a knowledge base consistingof frames. A frame (also called a schema) is an encodeddescription of the characteristics and relationships of entities.For example, an expert system designed to analyzecourt cases might have frames that describe the roles andinterests of the defendant, defense counsel, prosecutor, andso on, and other frames describing the trial and sentencingprocess. Using this knowledge, the system might be able topredict what sort of plea agreement a particular defendantmight reach with the state. While potentially more robustthan a rules-based system, a frames-based system faces thetwin challenges of building and maintaining a complex andopen-ended knowledge base and of developing methods ofreasoning more akin to generalized artificial intelligence(see artificial intelligence).Building an expert system requires that the knowledge of expertsbe “captured” in the form of a series of assertions and rules calleda knowledge base. Once the knowledge base is established, usersseeking advice can use an inference engine to examine the knowledgebase for valid conclusions that can be expressed as recommendations,often with varying degrees of confidence.TrendsExpert systems (particularly of the rules-based variety) nowhave an established place in business, industry, and science.The field of genomics and genetic engineering, widelyseen as the “technology of the 21st century” may be a particularlyfruitful applications area for analytical expert systems.Another promising area is the use of expert systemsfor e-commerce marketing analysis (see data mining). Anemerging emphasis in expert system development is theuse of object-oriented concepts (see object-oriented programming)and distributed database and knowledge sharingtechnology to build and maintain large knowledge basesmore efficiently.Further Reading“Expert Systems.” American Association for Artificial Intelligence.Available online. URL: http://www.aaai.org/AITopics/html/expert.html. Accessed July 31, 2007.Giarrartano, Joseph C., and Gary D. Riley. Expert Systems: Principlesand Programming. 4th ed. Boston: Thomson CourseTechnology, 2004.“Introduction to Expert Systems.” Available online. URL: http://www.expertise2go.com/webesie/tutorials/ESIntro/. AccessedJuly 31, 2007.Jackson, Peter. Introduction to Expert Systems. 3rd ed. Reading,Mass.: Addison-Wesley, 1998.

Ffault toleranceFault tolerance is a design concept that recognizes that allcomputer-based systems will fail eventually. The question iswhether a system as a whole can be designed to “fail gracefully.”This means that even if one or more componentsfail, the system will continue to operate according to itsdesign specifications, even if its speed or throughput mustdecrease.Methods and ImplementationsThere are a number of ways to make a system more faulttolerant. Individual components such as hard drives can becomposed of multiple units so that the remaining units cantake over if one fails (see also raid). If each key componenthas at least one backup, then there should be time to replacethe primary before the backup also fails.Another way to achieve fault tolerance is to provide multiplepaths to successful completion of the task. In fact, thisis how packet-switched networks like the Internet work(see tcp/ip). If one communications link is down or toocongested, packets are given an alternative routing.Fault diagnosis software can also play an important roleboth in determining how to respond to a problem (beyondany automatic response) and for providing data that will beuseful later to system administrators or technicians. Somefault diagnosis systems can use elaborate rules (see expertsystems) to pinpoint the cause of a fault and recommend asolution.The amount of fault tolerance to be provided for a systemdepends on a number of factors:• How important is it that the system not fail?• How critical is a given component to the operation ofthe system?• How likely is it that a given component will fail?(Mean time between failures, or MBTF)• How expensive is it to make the component or systemfault tolerant?A related concept is fail-safe. While fault toleranceemphasizes continued operation despite one or more failures,fail-safe emphasizes the ability to shut down safelyin case of an unrecoverable failure. With computer-basedsystems, fail-safe design can use redundant systems (asin avionics) to perform calculations, with a failing system“outvoted” if necessary by the good ones. In most casesthere should also be a provision to alert the pilot or operatorin time to take over operations from the automaticsystem.Another common example of fail-safe is modern operatingsystems that create a “journal” of pending operations tofiles that can be used to restore the integrity of the systemafter a power failure or other abrupt shutdown (see filesystem.)Further ReadingIsermann, Rolf. Fault-Diagnosis Systems: An Introduction from FaultDetection to Fault Tolerance. New York: Springer, 2006.Koren, Israel, and C. Mani Krishna. Fault-Tolerant Systems. SanFrancisco: Morgan Kauffman, 2007.National Institute of Standards and Technology. “A ConceptualFramework for System Fault Tolerance.” Available online. URL:189

190 Feigenbaum, Edwardhttp://hissa.nist.gov/chissa/SEI_Framework/framework_1.html. Accessed September 20, 2007.Pullum, Laura L. Software Fault Tolerance: Techniques and Implementation.Norwood, Mass.: Artech House, 2001.Feigenbaum, Edward(1936– )AmericanComputer ScientistEdward Feigenbaum is a pioneer artificial intelligenceresearcher, best known for his development of expert systems(see artificial intelligence). Feigenbaum was bornin Weehawken, New Jersey. His father, a Polish immigrant,died before Feigenbaum’s first birthday. His stepfather, anaccountant and bakery manager, was fascinated by scienceand regularly brought young Edward to the Hayden Planetarium’sshows and to every department of the vast Museumof Natural History. The electromechanical calculator hisfather used to keep accounts at the bakery particularly fascinatedEdward. His interest in science gradually turned toa perhaps more practical interest in electrical engineering.While at the Carnegie Institute of Technology (nowCarnegie Mellon University), Feigenbaum was encouragedto venture beyond the more mundane curriculum tothe emerging field of computation. He became interestedin John Von Neumann’s work in game theory and decisionmaking and also met Herbert Simon, who was conductingpioneering research into how organizations madedecisions (see von Neumann, John). This in turn broughtFeigenbaum into the early ferment of artificial intelligenceresearch in the mid-1950s. Simon and Alan Newell had justdeveloped Logic Theorist, a program that simulated theprocess by which mathematicians proved theorems throughthe application of heuristics, or strategies for breaking problemsdown into simpler components from which a chain ofassertions could be assembled leading to a proof.Feigenbaum quickly learned to program IBM mainframesand then began writing AI programs. For his doctoralthesis, he explored the relation of artificial problemsolving to the operation of the human mind. He wrote acomputer program that could simulate the human processof perceiving, memorizing, and organizing data forretrieval. Feigenbaum’s program, the Elementary Perceiverand Memorizer (EPAM), was a seminal contribution to AI.Its “discrimination net,” which attempted to distinguishbetween different stimuli by retaining key bits of information,would eventually evolve into the neural network (seeneural network). Together with Julian Feldman, Feigenbaumedited the 1962 book Computers and Thought, whichsummarized both the remarkable progress and perplexingdifficulties encountered during the field’s first decade.During the 1960s, Feigenbaum worked to develop systemsthat could perform induction (that is, derive generalprinciples based on the accumulation of data about specificcases). Working on a project to develop a mass spectrometerfor a Mars probe, Feigenbaum and his fellow researchersbecame frustrated at the computer’s lack of knowledgeabout basic rules of chemistry. Feigenbaum then decidedthat such rules (or knowledge) might be encoded in sucha way that the program could apply it to the data beinggathered from chemical samples. The result in 1965 wasDendral, the first of what would become a host of successfuland productive expert systems (see expert system). Afurther advance came in 1970 with Meta-Dendral, a programthat could not only apply existing rules to determinethe structure of a compound, it could also compare knownstructures with the existing database of rules and infer newrules, thus improving its own performance.During the 1980s, Feigenbaum coedited the four-volumeHandbook of Artificial Intelligence. He also introduced expertsystems to a lay audience in two books, The Fifth Generation(co-authored with Pamela McCorduck) and The Rise of theExpert Company.Feigenbaum combined scientific creativity with entrepreneurshipin founding a company called IntelliGeneticsand serving as a director of Teknowledge and IntelliCorp.These companies pioneered the commercialization ofexpert systems. In doing so, Feigenbaum and his colleaguespublicized the discipline of “knowledge engineering”—thecapturing and encoding of professional knowledge in medicine,chemistry, engineering, and other fields so that it canbe used by an expert system. In what he calls the “knowledgeprinciple” he asserts that the quality of knowledge ina system is more important than the algorithms used forreasoning. Thus, Feigenbaum has tried to develop knowledgebases that might be maintained and shared as easily asconventional databases.Remaining active in the 1990s, Feigenbaum was secondpresident of the American Association for Artificial Intelligenceand (from 1994 to 1997) chief scientist of the U.S.Air Force. In 1995, Feigenbaum received the Association forComputing Machinery’s prestigious A. M. Turing Award.Founder of the Knowledge Systems Laboratory at StanfordUniversity, Feigenbaum remains a professor emeritus ofcomputer science at that institution.Further ReadingFeigenbaum, Edward, Julian Feldman, and Paul Armer, eds. Computersand Thought. Cambridge, Mass.: MIT Press, 1995.Feigenbaum, Edward, Pamela McCorduck, and H. Penny Nii. TheRise of the Expert Company: How Visionary Companies areUsing Artificial Intelligence to Achieve Higher Productivity andProfits. New York: Vintage Books, 1989.Henderson, Harry. Artificial Intelligence: Mirrors for the Mind. NewYork: Chelsea House, 2007.Shasha, Dennis, and Cathy Lazere. Out of Their Minds: The Livesand Discoveries of 15 Great Computer Scientists. New York:Copernicus/Springer-Verlag, 1995.fiber opticsA fiber optic (or optical fiber) cable transmits photons(light) instead of electrons. Depending on the diameter ofthe cable, the light is guided either by total internal reflectionor as a waveguide (manipulating refraction). Theseprinciples were known as early as the mid-19th century andbegan to be used in the 20th century for such applications

file 191as dental and medical illumination and in experiments intransmitting images for television.DevelopmentOptical fiber in its modern form was developed in the1950s. The glass fiber through which the light passes issurrounded by a transparent cladding designed to providethe needed refractive index to keep the light confined. Thecladding in turn is surrounded by a resin buffer layer andoften an outer jacket and plastic cover. Fiber used for communicationis flexible, allowing it to bend if necessary.Early optical fiber could not be used for practical communicationbecause of progressive attenuation (weakening)of the light as it traveled. However, by the 1970s the attenuationwas being reduced to acceptable levels by removingimpurities from the fibers. Today the light signals can travelhundreds of miles without the need for repeaters or amplifiers.In the 1990s a new type of optical fiber (photonic crystal)using diffraction became available. This kind of fiberis particularly useful in applications that require higherpower signals.Communications and Network ApplicationsOptical fiber has several advantages over ordinary electriccable for communications and networking. The signals cantravel much farther without the need for a repeater to boostthe signal. Also, the ability to modulate wavelengths allowsoptical fiber to carry many separate channels, greatly increasingthe total data throughput. Optical fiber does not emit RF(radio frequency) energy, a source of “cross talk” (interference)in electrical cable. Fiber is also more secure than electricalcable because it is hard for an eavesdropper to tap.Today fiber is used for most long-distance phone linesand Internet connections. Many cable television systemsare upgrading from video cable to fiber because of itsgreater reliability and ability to carry more bandwidth andenhanced data services.The last area where electrical (copper) cable predominatesis in the “last mile” between main lines and housesor buildings, and within local networks. However, newbuildings and higher-end homes often include built-in fiber.Increasingly, phone companies are upgrading service bybridging the last mile through fiber-to-the-home (FTTH)networks. While requiring a considerable investment, FITHallows phone companies to replace relatively slow DSL withfaster (higher bandwidth) service better suited to delivervideo, data, and phone service simultaneously (see bandwidth,cable modem, and dsl). As of 2008, 3.3 millionAmerican homes had fiber connections, mainly throughVerizon’s FIOS service. It is expected that FTTH will bebuilt into many new housing developments.In 2007 Corning announced the development of “nanostructured”optical fibers that can be bent more sharply(such as around corners) without loss of signal. Corning isworking with Verizon to develop easier and cheaper waysto provide FTTH.(Related optical principles can also be applied to computerdesign. See optical computing.)Further ReadingThe Fiber Optic Association. “User’s Guide to Fiber Optic SystemDesign and Installation.” Available online. URL: http://www.thefoa.org/user/. Accessed September 20, 2007.“Fiber Optics: The Basics of Fiber Optic Cable: A Tutorial.” Availableonline. URL: http://www.arcelect.com/fibercable.htm.Accessed September 20, 2007.Fiber to the Home Council. Available online. URL: http://www.ftthcouncil.org/. Accessed September 20, 2007.Hecht, Jeff. Understanding Fiber Optics. 5th ed. Upper Saddle River,N.J.: Prentice Hall, 2005.Palais, Joseph C. Fiber Optic Communications. 5th ed. Upper SaddleRiver, N.J.: Prentice Hall, 2004.fileAt bottom, information in a computer is stored as a series ofbits, which can be grouped into larger units such as bytesor “words” that represent particular numbers or characters.In order to be stored and retrieved, a collection of suchbinary data must be given a name and certain attributesthat describe how the information can be accessed. Thisnamed entity is the file.Files and the Operating SystemFiles can be discussed at three levels, the physical layout,the operating system, and the application program. At thephysical level, a file is stored on a particular medium. (Seefloppy disk, hard disk, cd-rom, and tape drives.) Ondisk devices a file takes up a certain number of sectors,which are portions of concentric tracks. (On tape, files areusually stored as contiguous segments or “blocks” of data.)The file system is the facility of the operating system thatorganizes files (see operating system). For example, on DOSand older Windows PCs, there is a file allocation table (FAT)that consists of a linked list of clusters (each cluster consistsof a fixed number of sectors, varying with the overall size ofthe disk). When the operating system is asked to access a file,it can go through the table and find the clusters belonging tothat file, read the data and send it to the requesting application.Modern file systems further organize files into groupscalled folders or directories, which can be nested several layersdeep. Such a hierarchical file system makes it easier forusers to organize the dozens of applications and thousands offiles found on today’s PCs. For example, a folder called Bookmight have a subfolder for each chapter, which in turn containsfolders for text and illustrations relating to that chapter.Besides storing and retrieving files, the modern file systemsets characteristics or attributes for each file. Typicalattributes include write (the file can be changed), read (thefile can be accessed but not changed), and archive (whichdetermines whether the file needs to be included in the nextbackup). In multi-user operating systems such as UNIXthere are also attributes that indicate ownership (that is,who has certain rights with regard to the file). Thus a filemay be executable (run as a program) by anyone, but writeable(changeable) only by someone who has “superuser”status (see also data security).The current generation of file systems for PCs includesadditional features that promote efficiency and particularly

192 file serverdata integrity. Versions of Windows starting with NT, 2000,and XP come standardly with NTFS, the “New TechnologyFile System,” which includes journaling, or the keeping ofa record of all transactions affecting the system (such asdeleting or adding a file). In the event of a mishap such asa power failure, the transactions can be “replayed” fromthe journal, ensuring that the file system reflects the actualcurrent status of all files. NTFS also uses “metadata” thatdescribes each file or directory. Database principles canthus be applied to organizing and retrieving files at a higherlevel.Linux (based on UNIX) uses a single file system hierarchythat incorporates all devices in the system. (The networkfile system, NFS, effectively extends the hierarchy toall machines on the local network.) The popular Linux ext3file system also includes journaling.Files and ApplicationsThe ultimate organization of data in a file depends on theapplication. A typical approach is to define a data recordwith various fields. The program might have a loop thatrepeatedly requests a record from the file, processes it insome way, and repeats until the operating system tells itthat it has reached the end of the file. This would be asequential access; a program can also be set up for randomaccess, which means that an arbitrary record can berequested and that request will be translated into the correctphysical location in the file. The two approaches canbe combined in ISAM (Indexed Sequential Access Method),where the records are stored sequentially but fields areindexed so a particular record can be retrieved.Since files such as graphics (images), sound, and formattedword processing documents can only be read and usedby particular applications, files are often given names withextensions that describe their format. When a Windowsuser sees, for example, a Microsoft Word document, thefilename will have a .DOC extension (as in chapter.doc) andwill be shown with an icon registered by the application forsuch files. Further, a file association will be registered sothat when a user opens such a file the Word program willrun and load it.From a user interface point of view, the use of the file asthe main unit of data has been criticized as not correspondingto the actual flow of most kinds of work. While fromthe computer’s point of view, the user is opening, modifying,and saving a succession of separate files, the user oftenthinks in terms of working with documents (which mayhave components stored in a number of separate files.) Thus,many office software applications offer a document-orientedor project-oriented view of data that hides or minimizes thedetails of individual files (see document model).Further ReadingCallaghan, Brent. XFS Illustrated. Reading, Mass.: Addison-WesleyProfessional, 1999.Matloff, Norman. “File Systems in UNIX.” Available online. URL:http://heather.cs.ucdavis.edu/~matloff/UnixAndC/Unix/FileSyst.html. Accessed August 1, 2007.Nagar, Rajeev. Windows NT File System Internals. Reprint. Amherst,N.H.: OSR Press, 2006.Pate, Steven. UNIX File Systems: Evolution, Design, and Implementation.New York: Wiley, 2003.file serverThe growth in desktop computing since the 1980s hasresulted in much data being moved from mainframe computersto desktop PCs, which are now usually linked bynetworks. While a network enables users to exchange files,there remains the problem of storing large files or collectionsof files (such as databases) that are too large for a typicalPC hard drive or that need to be accessed and updatedby many users.The common solution is to obtain a computer withlarge, fast disk drives (see also raid). This computer, thefile server, is equipped with software (often included withthe networking package) that serves (provides) files asrequested by users or applications on the other PCs onthe network. (See also client-server computing.) Thespecifics of configuring the server for optimum efficiency,providing adequate security, and arranging for backup orarchiving varies with the particular network operating systemin use (the most popular environments are WindowsNT, Vista, and the various versions of UNIX and Linux).The file server has many advantages over storing thefiles needed by each user on his or her own PC. By storingthe files on a central server, ordinary users’ PCs do not needto have larger, more expensive disk drives. Central storagealso makes it easier to ensure that backups are run regularly(see backup and archive systems).There are some potential problems with this approach.With central storage, a failure of the file server could bringwork throughout the network to a halt. (The use of RAIDwith its redundant “mirror” disks is designed to preventthe failure of a single drive from making data inaccessible).As the network and/or size of the data store gets larger,multiple servers are usually used. The performance of a fileserver is also greatly affected by the efficiency of the cachingmechanism used (see cache).As the amount of data that must be stored increases,organizations will consider storage area network (SAN) andnetwork attached storage (NAS, see networked storage)technologies. SAN makes it easier for numerous users toshare a resource such as an automated tape library or diskRAID, while NAS is an efficient way to allow files to be centrallystored but readily shared.All but the simplest servers require special software orextensions to the operating system. For example, MicrosoftWindows Server is essentially a version of Windows withbuilt-in facilities for managing a file or application server,including the ability to organize “clusters” of servers andbalance the load of requests. Linux often comes in serverversions as well, though this is basically simply a distributionpreconfigured with the programs needed to manageservers (such as Samba).Meanwhile, the reason for having a file server is changing.Cost of storage is much less of an issue for smalleroffices with the recent availability of high-capacity drives(500 GB or more) starting at approximately $100. However,

file transfer protocols 193a central server still may offer better security and can serveas a central repository from which documents or sourcecode can be “checked out” and updated in an orderly way(version control).Further Reading“Designing and Deploying File Servers.” Microsoft TechNet.Available online. URL: http://technet2.microsoft.com/windowsserver/en/library/42befce4-7c15-4306-8edc-a80b8c57c67d1033.mspx. Accessed August 1, 2007.Eckstein, Robert, David Collier-Brown, and Peter Kelly. UsingSamba. 2nd ed. Sebastapol, Calif.: O’Reilly Media, 2003.Matthews, Martin S. Windows Server 2003: A Beginner’s Guide. 2nded. Berkeley, Calif.: McGraw-Hill Osborne, 2003.“Samba: Opening Windows to a Wider World.” Available online.URL: http://us3.samba.org. Accessed August 1, 2007.Tulloch, Mitch. Introducing Windows Server 2008. Redmond,Wash.: Microsoft Press, 2007.file-sharing and P2P networksFile-sharing services allow participants to provide access tofiles on their personal computers, such as music or video.In turn, the user can browse the service to find and downloadmaterial of interest. The structure is generally that of apeer-to-peer (P2P) network with no central server.The first major file-sharing service was Napster. Thiswas a P2P network but had a central server that providedthe searchable list of files and locations—but not the filesthemselves, which were downloaded from users’ PCs.Napster was forced to close in 2001 by legal action fromcopyright holders (see intellectual property and computing).A new but unrelated for-pay service opened laterunder the same name.Because of the legal vulnerability of centralized-list P2Pservices, a new model was developed, typified by Gnutella.This is a fully P2P model with both indexing and datadecentralized in nodes throughout the network. As of mid-2006, Gnutella and similar services such as Kazaa had anestimated 10 million users.BitTorrentMany services today use the popular BitTorrent file-sharingprotocol. A BitTorrent client (either the program of thatname or another compatible one) can transmit or receiveany type of data. To share a file, the client creates a “torrent”—asmall file that contains metadata describing thefile and an assignment to a “tracker.” The tracker is anothercomputer (node) that coordinates the distribution of thefile. Although this sounds complicated and a request takeslonger to set up than an ordinary HTTP connection, theadvantage is that once set up, downloading is efficientlymanaged even for files for which there is high demand.The downloading client connects to multiple clients thatprovide pieces of the desired file. Because of its efficiency,BitTorrent allows for distribution of substantial amounts ofdata at low cost, particularly since the system “scales up”automatically without having to provide extra resources.BitTorrent is currently being used for a variety of legallydistributed material, including video, sound, and textualcontent (see blogs and blogging, podcasting, and rss).Legal IssuesBecause of their frequent use to share copyrighted music,video, or other material, a variety of organizations of copyrightowners have sued file-sharing services and/or theirusers. The biggest problem for the courts is to determinewhether there is “substantial non-infringing use”—that is,the service is being used to exchange legal data.Some file-sharing services have been accused of distributingmalware (viruses or spyware) or of being usedto distribute material that is illegal per se (such as childpornography).In response to litigation threats, file-sharing serviceshave tended to become more decentralized, and some havefeatures that increase anonymity of users (see anonymityand the Internet) or use encryption.Further ReadingBitTorrent. Available online. URL: http://www.bittorrent.com/.Accessed September 20, 2007.Gardner, Susannah, and Kris Krug. BitTorrent for Dummies. Hoboken,N.J.: Wiley, 2006.Gnutella. Available online. URL: http://www.gnutella.com/.Accessed September 20, 2007.Roush, Wade. “P2P: From Internet Scourge to Savior.” TechnologyReview. December 15, 2006. Available online. URL: http://www.technologyreview.com/Biztech/17904. Accessed September21, 2007.Schmidt, Aernout, Wilfred Dolfsma, and Wim Keuvelaar. Fightingthe War on File Sharing. Cambridge: Cambridge UniversityPress, 2007.Silverthorne, Sean. “Music Downloads: Pirates—or Customers?”[Q&A with Felix Oberholzer-Gee]. Harvard Business SchoolWorking Knowledge. Available online. URL: http://hbswk.hbs.edu/item/4206.html. Accessed September 20, 2007.Wang, Wallace. Steal This File Sharing Book: What They Won’t TellYou About File Sharing. San Francisco: No Starch Press, 2004.file transfer protocolsWith today’s networked PCs and the use of e-mail attachmentsit is easy to send a copy of a file or files from onecomputer to another, because networks already include allthe facilities for doing so. Earlier, many PCs were not networkedbut could be connected via a dial-up modem. Toestablished the connection, a terminal program running onone PC had to negotiate with its counterpart on the othermachine, agreeing on whether data would be sent in 7- or8-bit chunks, and the number of parity bits that would beincluded for error-checking (see error correction). Thesending program would inform the receiving program asto the name and basic type of the file. For binary files(files intended to be interpreted as literal binary codes, aswith executable programs, images, and so on) the contentswould be sent unchanged. For text files, there might be theissue of which character set (7- bit or 8-bit ASCII) was beingused, and whether the ends of lines were to be marked witha CR (carriage return) character, an LF (linefeed), or both(see characters and strings).

194 film industry and computingImplementationsOnce the programs agree on the basic parameters for a filetransfer, the transfer has to be managed to ensure that itcompletes correctly. Typically, files are divided into blocksof data (such as 1K, or 1024 bytes each). During the 1970s,Ward Christensen developed Xmodem, the first widely usedfile transfer program for PCs running CP/M (and later, MS-DOS and other operating systems). Xmodem was quite reliablebecause it incorporated a checksum (and later, a moreadvanced CRC) to check the integrity of each data block.If an error is detected, the receiving program requests aretransmission.The Ymodem program adds the capability of specifyingand sending a batch of files. Zmodem, the latest in this lineof evolution, automatically adjusts for the amount of errorscaused by line conditions by changing the size of the datablocks used and also includes the ability to resume after aninterrupted file transfer. Another widely used file transferprotocol is Kermit, which has been implemented for virtuallyevery platform and operating system. Besides file transfer,Kermit software offers terminal emulation and scriptingcapabilities. However, despite their robustness and capability,Zmodem and Kermit have been largely supplanted bythe ubiquitous Web download link.In the UNIX world, the ftp (file transfer protocol) programhas been a reliable workhorse for almost 30 years.With ftp, the user at the PC or terminal connects to an ftpserver on the machine that has the desired files. A variety ofcommands are available for specifying the directory, listingthe files in the directory, specifying binary or text mode,and so on. While the traditional implementation uses typedtext commands, there are now many ftp clients available forPCs that use a graphical interface with menus and buttonsand allow files to be selected and dragged between the localand remote machines.Even though many files can now be downloaded throughHTML links on Web pages, ftp is still the most efficient wayto transfer batches of files, such as for uploading content toa Web server.Further Reading“FTP New User Guide.” Available online. URL: http://www.ftpplanet.com/ftpresources/basics.htm.Accessed August 4,2007.Loshin, Peter. Big Book of Internet File Transfer RFCs. San Diego,Calif.: Morgan Kaufmann, 2000.Pike, Mary Ann, and Noel Estabrook. Using FTP. Indianapolis:Que, 1995.“What Is Kermit?” Columbia University. Available online. URL:http://www.columbia.edu/kermit/kermit.html. AccessedAugust 4, 2007.film industry and computingAnyone who compares a science fiction film of the 1960s or1970s with a recent offering will be struck by the realism withwhich today’s movie robots, monsters, or aliens move againstvistas of giant starships and planetary surfaces. The computerhas both enhanced the management of cinematic productionprocesses and made possible new and startling effects.The role of the computer in film begins well beforethe first camera rolls. Writers can use computers to writescripts, while specialized programs can be used to layout storyboards. Using 3D programs somewhat like CAD(drafting) programs, set designers can experiment withthe positioning of objects before deciding on a final designand obtaining or creating the physical props. For mattes(backgrounds against which the characters will be shot ina scene), a computer-generated scene can now be inserteddirectly into the film without the need for an expensive,hand-painted backdrop.Similarly, animation and special effects can now be renderedin computer animation form and integrated into thestoryboard so that the issues of timing and combining ofeffects can be dealt with in the design stage. The actualeffects can then be created (such as by using extremelyrealistic computer-controlled puppets and models togetherwith computer generated imagery, or CGI) with the assurancethat they will properly fit into the overall sequence.The ability to combine physical modeling, precise control,and added textures and effects can now create a remarkablyseamless visual result in which the confrontation between abeleaguered scientist and a vicious velociraptor seems quitebelievable.Just as the physical and virtual worlds are frequentlyblended in modern moviemaking, the traditional categoriesof visual media have also merged. Disney’s fully animatedfilms such as The Lion King benefit from the same computergeneratedlighting and textures as the filming of live actors.Using 3D graphics engines, computer game scenes are nowrendered with almost cinematic quality (see computergames). Even characters from old movies can be digitallycombined (composited) with new footage. (Of course, theartistic value of such efforts may be controversial.)Computer technology, now relatively inexpensive, canalso give the generally lower budget world of televisionaccess to higher-quality effects. As computers continue tobecome more powerful yet cheaper, amateur or independentfilmmakers are gaining abilities previously reserved tobig Hollywood studios.The delivery of film and video has also been greatlyaffected by digitization. Classic movies can be digitizedto rescue them from deteriorating film stock, while videoscan be delivered digitally over cable TV systems or over theInternet. The ability to easily copy digital content does raiseissues of piracy or theft of intellectual property (see intellectualproperty and computing).More recently, digital camcorders (and video modes indigital cameras and even cell phones) are making access tobasic “film” technology a part of everyday life. A few minutesbrowsing a video-sharing site (see YouTube) revealsa wide variety of documentary and creative productionsranging from the equivalent of the old “home movie” toprofessional quality.Further ReadingHarris, Tom. “How Digital Cinema Works.” Available online. URL:http://entertainment.howstuffworks.com/digital-cinema.htm.Accessed August 4, 2007.

finite-state machine 195Masson, Terrence, ed. CG 101: A Computer Graphics Industry Reference.2nd ed. Williamstown, Mass.: Digital Fauxtography,2007.McKernan, Brian. Digital Cinema: The Revolution in Cinematography,Post-Production, and Distribution. New York: McGraw-Hill, 2005.“Milestones in Film History: Greatest Visual and Special Effects.”Available online. URL: http://www.filmsite.org/visualeffects.html. Accessed August 4, 2007.Sawicki, Mark. Filming the Fantastic: A Guide to Visual Effects Cinematography.Burlington, Mass.: Focal Press, 2007.Slone, Michael. Special Effects: How to Create a Hollywood Film ona Home Studio Budget. Studio City, Calif.: Michael Wiese Productions,2007.Swartz, Charles S, ed. Understanding Digital Cinema: A ProfessionalHandbook. Burlington, Mass.: Focal Press, 2005.Willis, Holly. New Digital Cinema: Reinventing the Moving Image.London: Wallflower Press, 2005.financial softwareLarge businesses use complex database systems, spreadsheets,and other applications for activities such as accounting,planning/forecasting, and market research (seebusiness applications of computers). Here we will considerthe variety of consumer and small business softwareapplications that are available to help with the planningand management of financial activities, such as• home budgeting and money management• investment and retirement planning• college financing• tax planning and filing• home buying or selling• basic accounting, inventory, and other activities forsmall businessBasic home money management programs (such as the popularQuicken) handle the budgeting and recording of dailyand monthly expenses. The program can usually also interfacewith on-line banking services (see banking and computers)as well as exporting data to tax filing software.For small or home-based businesses, programs such asQuickBooks can provide basic management of inventory,sales, taxes, expenses, and other functions. There are alsoniche programs for applications such as managing on-lineauctions or Web-based sales.For financial planning, there are a variety of programs(ranging from small free or shareware utilities available onlineto full commercial packages) that offer special calculators,graphs, and other aids for planning for the future. Forexample, the future value of a savings account at variouspoints can be calculated given the interest rate, or the fullcost of a loan or mortgage similarly calculated. Full-featuredprograms usually include helpful explanations of thevarious types of financial instruments. Some programs conductan “interview” where the program asks the user abouthis or her objectives, priorities, or tolerance for risk, andthen recommends a course of action. Such programs can behelpful even though they lack the experience and breadthof knowledge available to a human financial planner.Tax preparation software is perhaps the fastest-growingconsumer financial application. Programs normally mustbe purchased each year to incorporate the latest changesin tax law. An important incentive has been created by theInternal Revenue Service encouraging electronic filing oftax returns by promising speedier refunds to “e-filers.”TrendsPublishers of respected guidebooks (such as for collegeadmissions and financial aid) are creating electronic versionsthat can be easier to use and more up to date thanthe printed counterpart. Meanwhile, many Web sites areoffering utilities such as financial calculators, implementedin Java and run on-line without any software having tobe downloaded by the user. The services can be offeredto attract users for paid services or simply to acquire e-mail addresses for solicitation. Users should be cautiousabout revealing sensitive identification or financial data tounknown on-line sites.The growth in small and home-based businesses islikely to continue in an economy that continues to offernew opportunities while reducing job security. While startinga small business is always an uncertain enterprise, easyto-useaccounting software offers the budding entrepreneura better chance of being able to stay on top of expenses duringthe crucial first months of business.The growing complexity of financial choices availableto average consumers and the need for more people totake responsibility for their retirement planning is likelyto increase the range and capability of financial planningapplications in the future.Further ReadingFinancial Software Reviews—Personal Finance Software. Availableonline. URL: http://financialsoft.about.com/od/reviewsfinancesoftware/Software_Reviews_Personal_Finance_Software.htm. Accessed August 4, 2007.Heady, Robert K., Christy Heady, and Hugo Ottolenghi. The CompleteIdiot’s Guide to Managing Your Money. 4th ed. Indianapolis:Alpha Books, 2005.Ivens, Kathy. Quickbooks 2007: The Official Guide. Berkeley, Calif.:Osborne/McGraw-Hill, 2007.Nelson, Stephen L. Quicken 2007 for Dummies. Hoboken, N.J.:Wiley, 2007.finite-state machineThere are many calculations or other processes that can bedescribed using a specific series of states or conditions. Forexample, the state of a combination lock depends not onlyon what numeral is being dialed or punched at the moment,but on the numbers that have been previously entered. Aneven simpler example is a counter (such as a car odometer),whose next output is equal to one increment plus its currentsetting. In other words, a state-based device has aninherent “memory” of previous steps.In computing, a program can be set up so that eachpossible input, when combined with the current state, will

196 firewallcontrolled by a state table. The interaction of such automatacan produce astonishingly complex patterns (see cellularautomata).ApplicationsMany programs and operating systems are structured as anendless loop where an input (or command) is processed,the results returned, the next input is processed, and soon, until an exit command is received. A mode or state canbe used to determine the system’s activity. For example, aprogram might be in different modes such as waiting forinput, processing input, displaying results, and so on. Theprogram logic will refer to the current state to determinewhat to do next and at some point the logic will transitionthe system to the next state in the sequence. The validity ofsome kinds of programs, protocols, or circuits can thereforebe proven by showing that there is an equivalent finite-statemachine—and thus that all possible combinations of inputshave been accounted for.Finite-state machines have many other interesting applications.Simple organisms can be modeled as a set of statesthat interact with the environment (see artificial life).The lower-level functions of robots can also be representedas a set of interacting finite-state machines. Even videogame characters often use FSMs to give them a repertoire ofplausible behavior.Further ReadingFinite State Machine Editor [software]. Available online. URL:http://fsme.sourceforge.net/. Accessed August 4, 2007.Meyer, Nathaniel. “Finite State Machine Tutorial.” Availableonline. URL: http://www.generation5.org/content/2003/FSM_Tutorial.asp. Accessed August 4, 2007.Wagner, Ferdinand, et al. Modeling Software with Finite StateMachines: A Practical Approach. Boca Raton, Fla.: CRC Press,2006.This diagram shows a finite-state representation of a ZIP code. Thearrows link each state (within a circle) to its possible successor. Inthis simple example each digit must be followed by another digituntil the fifth digit, which can either be followed by a blank (indicatinga five-digit ZIP code) or four more digits for a 9-digit ZIP.result in a specified output. That output becomes the newstate of the machine. (Alternatively, the machine can beset so that only the current state determines the output,without regard to the previous state.) This is supportedby the underlying structure of the logic switching withincomputer circuits as well as the “statefulness” of all calculations.(Given n, n+1 is defined, and so on.) Alan Turingshowed that combining the state mechanism with aninfinite memory (conceptualized as an endless roll of tape)amounted to a universal computer—that is, a mechanismthat could perform any valid calculation, given enough time(see Turing, Alan).The idea of the sequential (or state) machine is closelyrelated to automata, which are entities whose behavior isfirewallThe vulnerability of computer systems to malicious orcriminal attack has been greatly increased by the growingnumber of connections between computers (and local networks)and the worldwide Internet (see computer crimeand security, Internet, and tcp/ip). The widespread useof permanent broadband connections by consumers (suchas DSL and cable modem links) has increased the risk tohome users. Intruders can use “port scanning” programsto determine what connections a given system or networkhas open, and can use other programs to snoop and steal ordestroy sensitive data.A firewall is a program (or combination of software andhardware) that sits between a computer (or local network)and the Internet. Typical firewall functions include:• Examining incoming data packets and blocking thosethat include commands to examine or use unauthorizedports or IP addresses• Blocking data packets that are associated with commonhacking techniques such as “trojans” or “backdoor”exploitations

flag 197• Hiding all the internal network addresses on a localnetwork, presenting only a single address to theoutside world (this is also called NAT, or NetworkAddress Translation)• monitoring particular applications such as ftp (filetransfer protocol) and telnet (remote login), restrictingthem to certain addresses. Often a special addresscalled a proxy is established rather than allowingdirect connections between the outside and the localnetwork.Firewalls are usually configured by providing a rule thatspecifies what is to be done based on the origin address orother characteristics of an incoming packet. Because connectionsmade by local programs to the outside can alsocompromise the system, rules are also created for suchapplications. The firewall package may come with a set ofdefault rules for common applications and situations. Whensomething not covered by the rules happens, the user willbe prompted and guided to establish a new rule.Modern firewalls are “stateful,” meaning that they keeptrack not only of the source and destination of individualpackets but their context (including originating application).Microsoft Windows Vista has improved the operatingsystem’s built-in firewall, at the expense of added complexity.Zone Labs’s ZoneAlarm is another popular PC firewall.Linux provides a default firewall called iptables, which canbe configured by a variety of applications. For added protection,users of broadband Internet connections should notconnect their PC directly to the Internet. Rather, an inexpensivewired or wireless router that includes a built-infirewall can be connected on one side to the cable or DSLmodem and on the other side to one or more computers inthe local network.Internet security packages for home users often combinea firewall with other services such as virus protection,parental control, and blocking of objectionable content oradvertising.Further ReadingHome PC Firewall Guide. Available online. URL: http://www.firewallguide.com/. Accessed August 4, 2007.Komar, Brian, Ronald Beekelaar, and Joern Wettern. Firewalls forDummies. 2nd ed. New York: Wiley, 2003.Noonan, Wes, and Ido Dubrawsky. Firewall Fundamentals. Indianapolis:Cisco Press, 2006.ZoneAlarm. Available online. URL: http://www.zonealarm.com.Accessed August 4, 2007.Zwicky, Elizabeth D., Simon Cooper, and D. Brent Chapman.Building Internet Firewalls. 2nd ed. Sebastapol, Calif.: O’ReillyMedia, 2000.FireWireFireWire is a high-speed serial interface used by personalcomputers and digital audio and video equipment. (Thename FireWire is an Apple brand name, but it is used generically.Technically it is the IEEE 1394 Serial Bus.)FireWire was developed in the 1990s by the IEEE P1394Working Group with substantial funding from Apple andhelp from engineers from major corporations includingIBM, Digital Equipment Corporation (DEC), Sony, andTexas Instruments. In 1993 it was hailed as the “most significantnew technology” by Byte magazine.FireWire was intended to replace Apple’s parallel SCSI(Small Computer System Interface). (Sony’s implementation,called I.Link, omits the two power pins in favor of aseparate power connector.) However, because Apple askedfor $1.00 per port in patent royalties, Intel instead developeda faster version of the universal serial bus (see usb)and that, rather than FireWire, is the standard port on mostWindows machines.Common uses for FireWire include connecting digitalvideo (such as camcorder) devices, audio devices, and somedata storage devices. FireWire is favored over USB 2.0 formany professional applications because of its higher speedand power distribution capabilities. However, it is moreexpensive than USB 2.0, which provides sufficient speedfor many consumer peripherals such as digital cameras andprinters.Further ReadingAnderson, Don, and MindShare, Inc. FireWire System Architecture.2nd ed. Boston: Addison-Wesley Pearson Education, 1998.FireWire (Apple Developer Connection). Available online. URL:http://developer.apple.com/hardwaredrivers/firewire/index.html. Accessed September 20, 2007.flagA flag is a variable that is used to specify a particular conditionor status (see variable). Usually a flag is either true orfalse. For example, a flag Valid_Form could be set to truebefore the input form is processed. If the validation checkfor any data field fails, the flag would be set to false. Afterthe input procedure has ended, the main program wouldcheck the Valid_Form flag. If it’s true, the data on the formis processed (for example, continuing on to the paymentprocess). If the flag is false, the input form might be redisplayedwith errors or omissions highlighted.Flags can be combined to check multiple conditions. Forexample, suppose the input form routine also looked up thecustomer’s account and checked to make sure the customerwas approved for purchasing. The test for this might read:If Valid_Form and Valid_Customer then// continue processing else// display error messagesIn such cases, the flags are combined using the appropriateand or or operators (see Boolean operators).While flags are often used inside a routine to keep trackof processing, modern programming practice discouragesthe use of “global” flags at the top level of the program. Aswith other global variables, such flags are vulnerable tobeing unpredictably changed or to having two parts of theprogram check the same flag without being able to rely onits state. (Thus a routine relies on a global flag being truebut calls another routine that sets the flag to false withoutthe original routine checking it again.) If several routines

198 flash and smart mobs(or even programs) are being run at the same time, the situationgets even more complicated and a semaphore that canbe controlled by one process at a time is more appropriate(see concurrent programming). However, a main programthat sets a flag to indicate the program mode and doesnot allow the flag to be changed by routines within the programis relatively safe.Flags can also have more than two valid conditions,such as for specifying a number of possible states for a fileor device. This usage is found mostly in operating systems.Further Reading“C++ I/O Flags.” Available online: URL: http://www-control.eng.cam.ac.uk/~pcr20/www.cppreference.com/cppio_flags.html.Accessed August 4, 2007.“Class Flags” [Java]. Available online. URL: http://java.sun.com/j2ee/sdk_1.3/techdocs/api/javax/mail/Flags.html. AccessedAugust 4, 2007.Myers, Gene. “Becoming Bit Wise.” C-Scene Issue 09. Availableonline. URL: http://www.gmonline.demon.co.uk/cscene/cs9/cs9-02.html. Accessed April 28, 2008.Vincent, Alan. “Flag Variables, Validation and Function Control.”Available online. URL: http://wsabstract.com/javatutors/valid1.shtml. Accessed February 4, 2008.flash and smart mobsA flash mob is a spontaneously organized public gatheringfacilitated by ubiquitous mobile communications (see especiallytexting and instant messaging). The earliest flashmobs were a mixture of whimsy and social experiment. Thefirst reported example, coordinated by Bill Wasik, senioreditor of Harper’s Magazine, occurred in June 2003 whena hundred people suddenly showed up on the ninth floorof Macy’s in New York City, claiming to be shopping for a“love rug.”Smart MobsSmart mobs are similar in organization to flash mobs buttend to be more purposeful and enduring forms of socialorganization. The phenomenon was first described by HowardRheingold in his book Smart Mobs: The Next SocialRevolution (see Rheingold, Howard). Rheingold describesseveral examples of smart mobs, including teenage “thumbtribes” in Tokyo and Helsinki, Finland (named for their useof tiny thumb-operated keyboards on cell phones). Theirtypical activities included organizing impromptu raves orconverging on rock stars or other celebrities.Smart mobs took on a more political bent in 1999 withspontaneously organized, fast-moving antiglobalizationprotests in Seattle. Police had considerable difficulty containingthe protests, their communications and coordinationcapabilities not being equal to the task.Another political smart mob occurred in 2001 whenprotesters in the Philippines used text messaging to organizedemonstrations against the government of PresidentJoseph Estrada. The protests grew rapidly, and Estrada wassoon forced from office (see political activism and theInternet). Smart mob techniques were also used startingin 2003 to coordinate protests against the Iraq War. Aswireless communication continues to become ubiquitous,aspects of smart mob organization can be expected to turnup in future mass movements.Even as the term has faded from public use, flash mobshave continued to flourish, appealing to a desire to have funwhile striking out against an overly regimented consumersociety. The term urban playground movement has also beenused for the promotion of such gatherings.Further ReadingBerton Justin. “Flash Mob 2.0: Urban Playground MovementInvites Participation.” San Francisco Chronicle, November 10,2007. Available online. URL: http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/11/10/MNMVT8UM9.DTL. AccessedApril 23, 2008.“Howard Rheingold: Smart Mobs.” Edge, July 16, 2002. Availableonline. URL: http://www.edge.org/3rd_culture/rheingold/rheingold_print.html. Accessed September 21, 2007.Packer, George. “Smart-Mobbing the War.” New York Times, March9, 2003. Available online. URL: http://query.nytimes.com/gst/fullpage.html?res=9D02E5D61F3CF93AA35750C0A9659C8B63. Accessed September 21, 2007.Rheingold, Howard. Smart Mobs: The Next Social Revolution. Cambridge,Mass.: Basic Books, 2002.———. Smart Mobs Web site. Available online. URL: http.://www.smartmobs.com/. Accessed September 21, 2007.Schwartz, John. “New Economy: In the Tech Meccas, Massesof People, or ‘Smart Mobs,’ are Keeping in Touch throughWireless Devices.” New York Times, July 22, 2002. Availableonline. URL: http://query.nytimes.com/gst/fullpage.html?sec=technology&res=98 02E5D61638F931A15754C0A9649C8B63. Accessed March 28, 2008.flash driveA flash or “thumb” drive is a small data storage device thatuses semiconductor flash memory rather than a disk drive.It is connected to a digital device using the universal serialbus (see usb). Because most computers, digital cameras,and other digital devices have USB ports, a flash drive is aconvenient way to provide up to 16 GB (as of 2007) of lowpower, rewritable memory. Flash drives first appeared inlate 2000.Flash drives can use a separate USB cable (useful whenseveral devices need to be connected to closely spaced USBports) or simply have a connector that plugs directly intothe port. Many people who regularly work with severalcomputers carry their backup data or even a complete operatingsystem (such as Linux) on a flash drive, perhaps connectedto their keyring.In Windows Vista some recent flash drives can be usedto provide an additional system memory cache through afeature called ReadyBoost.Flash drives can also be built into portable devices,including video and audio players. A competing technology(particularly found in digital cameras and PDAs) is theSecure Digital (SD) memory card developed by Matsushita,SanDisk, and Toshiba, which offers comparable capacitybut is proprietary and requires a special interface.For high-security applications, flash drives can includebuilt-in encryption or fingerprint readers (see biometrics).However, as with other readily portable media, unsecured

floppy disk 199flash drives containing sensitive data pose a real risk tomany organizations.Under development by SanDisk and Intel are larger flashdrives (32 or 80 GB) suitable for replacing hard drives in laptops.The benefits are lower weight and power consumption.Further ReadingAxelson, Jan. USB Mass Storage: Designing and Programming Devicesand Embedded Hosts. Madison, Wis.: Lakeview Research, 2006.Oreskovic, Alexei. “Intel Prepares Flash Attack.” The Street.com, September 9, 2007. Available online. URL: http://www.thestreet.com/s/intel-prepares-flash-attack/newsanalysis/techsemis/10380471.html. Accessed September 20, 2007.Tyson, Jeff. “How Flash Memory Works.” Available online. URL:http://developer.apple.com/hardwaredrivers/firewire/index.html. Accessed September 20, 2007.flat-panel displayThe traditional computer display uses a cathode ray tube(CRT) like that in a television set (see monitor). The flatpaneldisplay is an alternative used in most laptop computersand some higher-end desktop systems. The mostcommon type uses a liquid crystal display (LCD). The displayconsists of a grid of cells with one cell for each of thethree colors (red, green, and blue) for each pixel.The LCD cells are sandwiched between two polarizingfilter layers that consist of many fine parallel grooves. Thetwo filters are set so that the grooves on the second arerotated 90 degrees with respect to the first. By default, thelight is polarized by the first filter, twisted by the liquidcrystals so it is parallel to the grooves of the second filter,and thus passes through to be seen by the viewer. (For colordisplays, the light is first passed through one of three colorfilters to make it red, green, or blue as set for that pixel.)However, if current is applied to a crystal cell, the crystalsrealign so that the light passes through them withouttwisting. This means that the second polarizing filter nowblocks the light and the cell appears opaque (or dark) to theviewer.Color LCD displays can use two different mechanisms forsending the current through the crystals. In passive matrixdisplays, the current is timed so that it briefly charges thecorrect crystal cells. The charges fade quickly, making theimage look dim, and the display cannot be refreshed quicklybecause of the persistence of ghost images. This means thatsuch displays do not work well with games or other programswith rapidly changing displays.In an active matrix display, each display cell is controlledby its own thin film transistor (TFT). These displaysare sharper, brighter, and can be refreshed more frequently,allowing better displays for animations and games. However,fabrication costs for TFT displays are higher, and thedisplays are also vulnerable to having a few transistorsfail, leading to permanent dark spots on the display. Activematrix displays also use more power, reducing battery lifeon laptop PCs. A general disadvantage of flat panel displaysis that their pixel dimensions are fixed, so setting the displayto a resolution smaller than its full dimensions usuallyresults in an unsatisfactory image.When the current is off, the liquid crystals remain twisted so thelight passes through both polarizing panels and illuminates the display.However, when current is applied, the crystals straighten out,causing the light to be blocked by the second polarizing panel.As newer technologies bring down the cost of flat-panelLCD displays they are increasingly being seen on desktopPCs, where they have the advantage of taking up muchless space than conventional monitors while drawing lesspower.Further Reading“The PC Technology Guide. Flat panel displays.” Available online.URL: http://www.pctechguide.com/43FlatPanels.htm. AccessedAugust 14, 2007.White, Ron. How Computers Work. 8th ed. Indianapolis: Que,2005.floppy diskUntil the mid-1990s, the floppy disk or diskette was theprimary method for distributing software and providingremovable data storage for personal computers. Diskettesfirst appeared in the late 1960s on IBM minicomputers, andbecame more widespread on a variety of minicomputersand early microcomputers during the 1970s.The now obsolete 8-inch and 5-¼ inch disks were madefrom Mylar with a metal oxide coating, the assembly beinghoused in a flexible cardboard jacket (hence the term “floppydisk”). The more compact 3.5-inch diskettes first widelyintroduced with the Apple Macintosh in 1984 became thestandard type for all PCs by the 1990s. These diskettes areno longer truly “floppy” and come in a rigid plastic case.A typical floppy disk drive has a controller with twomagnetic heads so that both sides of the diskette can be

200 flowchartused to hold data. The surface is divided into concentrictracks that are in turn divided into sectors. (For more ondisk organization, see hard drive.) The heads are preciselypositioned to the required track/sector location using steppermotors under control of the disk driver. The data capacityof a disk depends on how densely tracks can be writtenon it. Today’s 3.5-inch diskettes typically hold 1.44 MB ofdata.In recent years, drive technology has advanced so thatmany more tracks can be precisely written in the sameamount of surface. The result is found in products such asthe popular Zip disks, which can hold 100 MB or even 250MB, making them comparable in capacity and speed witholder, smaller hard drives.Since the late 1990s, the traditional floppy disk has becomeless relevant for most users. With more computers connectedto networks, the use of network copying commands or e-mailattachments has made it less necessary to exchange files viafloppy, a practice dubbed “sneaker-net.” When data needs tobe backed up or archived, the high-capacity USB drive, tape,or writable CD is a more practical alternative to low-capacityfloppies. (See backup and archive systems.) With its iMacline, Apple actually discontinued including a floppy drive asstandard equipment. In PC-compatible laptops, a floppy driveis often available as a plug-in module that can be alternatedwith other devices. Desktop systems still sometimes comewith a single 3.5-inch drive.Further ReadingWhite, Ron. How Computers Work. 8th ed. Indianapolis: Que,2005.flowchartA flowchart is a diagram showing the “flow” or progress ofoperations in a computer program. Flowcharting was oneof the earliest aids to program design and documentation,and a plastic template with standard flowcharting symbolswas a common programming accessory. Today CASE (computer-aidedsoftware engineering) systems often includeutilities that can automatically generate flowcharts basedon the control structures and procedure calls found in theprogram code (see case).The standard flowchart symbols include blocks of variousshapes that represent input/output, data processing,sorting and collating, and so on. Lines with arrows indicatethe flow of data from one stage or process to the next. Adiamond-shaped symbol indicates a decision to be madeby the program. If the decision is an “if” (see branchingstatements) separate lines branch off to the alternatives.If the decision involves repeated testing (see loop), the linereturns back to the decision point while another line indicatesthe continuation of processing after the loop exits.Devices such as printers and disk drives have their ownsymbols with lines indicating the flow of data to or fromthe device.Complex software systems can employ several levels offlowcharts. For example, a particular routine within a programmight have its own flowchart. The routine as a wholeA flowchart uses a set of simple symbols to describe the stepsinvolved in a data processing operation. The parallelograms indicatean input/output operation (such as reading or writing a file).The “decision diamonds” have yes and no branches depending onthe result of a test or comparison.would then appear as a symbol in a higher-level flowchartrepresenting the program as a whole. Finally, a system chartmight show each program that is run as part of an overalldata processing system.While still useful, flowcharting is often supplemented byother techniques for program representation (see pseudocode).Also, modern program design tends to shift theemphasis from charting the flow of processing to elucidatingthe properties and relationships of objects (see objectorientedprogramming).Further ReadingBoillot, M. H., G. M. Gleason, and L. W. Horn. Essentials of Flowcharting.New York: WCB/McGraw-Hill, 1995.fontIn computing, a font refers to a typeface that has a distinctiveappearance and style. In most word processing, desktoppublishing, and other programs the user can select thepoint size at which the font is to be displayed and printed(in traditional typography each point size would be consideredto be a separate font). Operating systems such as Win-

Forth 201dows and Macintosh usually come with an assortment offonts, and applications can register additional fonts to makethem available to the system.Fonts are often presented as a “family” that includesthe same type design with different attributes such as boldfaceand italic. The spacing of letters could be uniform(monospace) as in the Courier font often used for printingcomputer program code or proportional (as with most textfonts). For proportional fonts the design can include kerning,or the precise fitting together of adjacent letters for amore attractive appearance. Fonts are also described as serifif they have small crossbars on the ends of letters such as atthe end of the crossbar on a T in the Times Roman font.Other fonts such as Arial lack the tiny bars and are calledsans serif (without serif).There are two basic ways to store font data in thecomputer system. Bitmapped fonts store the actual patternof tiny dots that make up the letters in the font. Thishas the advantage of allowing each letter in each pointsize to be precisely designed. The primary disadvantageis the amount of memory and system resources requiredto store a font in many point sizes. In practice, this considerationresults in only a relatively few fonts and sizesbeing available.The alternative, an outline or vector font uses a “pagedescription language” such as Adobe PostScript or TrueTypeto provide graphics commands that specify the drawingof each letter in a font. When the user specifies a font,the text is rendered by processing the graphics commandsin an interpreter. Since the actual bitmap doesn’t need to bestored and all point sizes of a font can be generated fromone description, outline fonts save memory and disk space(although they require additional processor resources forrendering). While sophisticated scaling techniques are usedto maintain a pleasing appearance as the font size changes,outline fonts will not look as polished as bitmapped fontsthat are hand-designed at each point size. (For use of fontssee typography, computerized.)Strictly speaking, a particular type design is called a typeface, anda font is a rendering of a typeface with specified characteristicssuch as height in points and possibly width or pitch in charactersper inch. Thus there are usually many fonts for each typeface.Further ReadingAaron, B. TrueType Display Fonts. San Francisco: Sybex, 1993.Adobe Systems. Adobe Type Library Reference Book. 2nd ed. MountainView, Calif.: Adobe Press, 2003.Headley, Gwyn. The Encyclopedia of Fonts. London: Cassell Illustrated,2005.Lupton, Ellen. Thinking with Type: A Critical Guide for Designers,Writers, Editors & Students. New York: Princeton ArchitecturalPress, 2007.Microsoft Typography. Available online. URL: http://www.microsoft.com/typography/default.mspx. Accessed August 4, 2007.TrueType Typography. Available online. URL: http://www.truetype-typography.com/. Accessed August 4, 2007.ForthThe unusual Forth programming language was designedby Charles H. Moore in 1970. An astronomer, Moore wasinterested in developing a compact language for controllingmotors to drive radio telescopes and other equipment.Language StructureForth has a very simple structure. The Forth system consistsof a collection of words. Each word is a sequence ofoperations (which can include other existing words). Forexample, the DUP word makes a copy of a data value. Datais held by a stack. For example, the arithmetic expressionwritten as 2 + 3 in most languages would be written inForth as + 2 3. When the + operator (which in Forth is apre-defined word) executes, it adds the next two numbersit encounters (2 and 3) together, and puts the sum on thestack (where in turn it might be fetched for further processingby the next word in the program (see stack). This representationis also called postfix notation and is familiar tomany users of scientific calculators.The words in the dictionary are “threaded” or linked sothat each word contains the starting address of the next one.The Forth interpreter runs a simple loop where it fetchesthe next token (one or more characters delimited by spaces)and scans the dictionary to see if it matches a defined word(including variables). If a word is found, the code in theword is executed. If no word is found, the interpreter interpretsthe token as a numeric constant, loads it on the stack,and proceeds to the next word.A key feature of Forth is its extensibility. Once you havedefined a word, the new word can be used in exactly the sameway as the predefined words. The various forms of definingwords allow for great control over what happens when a newword is created and when the word is later executed. (Inmany ways Forth anticipated the principles of object-orientedprogramming, with words as objects with implicit constructorsand methods. A well-organized Forth program builds upfrom “primitive” operations to the higher-level words, withthe program itself being the highest-level word.)Forth has always attracted an enthusiastic following ofprogrammers who appreciate a close communion with theflow of data in the machine and the ability to preciselytailor programs. The language is completely interactive,since any word can be typed at the keyboard to executeit and display the results. Forth was also attractive in the

202 FORTRANearly days of microcomputing because the lack of need fora sophisticated interpreter or compiler meant that Forthsystems could run comfortably on systems that had perhaps16K or 64K of available RAM.Forth never caught on with the mainstream of programmers,however. Its very uniqueness and the unusual mindsetit required probably limited the number of people willing tolearn it. While Forth programs can be clearly organized,badly written Forth programs can be virtually impossibleto read. However, Forth is sometimes found “under thehood” in surprising places (for example, the PostScript pagedescription language is similar to Forth) and the languagestill has a considerable following in designing hardwarecontrol devices (see embedded systems).Further ReadingBrodie, L. Starting FORTH. 2nd ed. Upper Saddle River, N.J.: PrenticeHall, 1987.———. Thinking FORTH. 2nd ed. Upper Saddle River, N.J.: PrenticeHall, 1994.Forth Interest Group. Available online. URL: http://www.forth.org. Accessed August 14, 2007.Rather, Elizabeth D. Forth Application Techniques. Hawthorne,Calif.: FORTH, Inc., 2006.FORTRANAs computing became established throughout the 1950s,the need for a language that could express operations in amore “human-readable” language began to be acutely felt.In a high-level language, programmers define variables andwrite statements and expressions to manipulate them. Theprogrammer is no longer concerned with specifying thedetailed storage and retrieval of binary data in the computer,and is freed to think about program structure and theproper implementation of algorithms.Fortran (FORmula TRANslator) was the first widelyused high-level programming language. It was developedby a project begun in 1954 by a team under the leadershipof IBM researcher John Backus. The goal of the project wasto create a language that would allow mathematicians, scientists,and engineers to express calculations in somethingclose to the traditional notation. At the same time, a compilerwould have to be carefully designed so that it wouldproduce executable machine code that would be nearly asefficient as the code that would have been created throughthe more tedious process of using assembly languages. (Seecompiler and assembler.)The first version of the language, Fortran I, becameavailable as a compiler for IBM mainframes in 1957. Animproved (and further debugged version) soon followed.Fortran IV (1963) expanded the number of supporteddata types, added “common” data storage, and includedthe DATA statement, which made it easier to load literalnumeric values into variables. This mature version of Fortranwas widely embraced by scientists and engineers, whocreated immense libraries of code for dealing with calculationscommonly needed for their work.By the 1970s, the structured programming movementwas well under way. This school of programming emphasizeddividing programs into self-contained procedures intowhich data would be passed, processed, and returned. Theuse of unconditional branches (GOTO statements) as wascommon in Fortran was now discouraged. A new version ofthe language, Fortran 77 (or F77), incorporated many of thenew structural features. The next version, Fortran 90 (F90),added support for recursion, an important technique forcoding certain kinds of problems (see recursion). Mathematicslibraries were also modernized. FORTRAN 2003contains a number of new features, including support formodern programming structures (see object-orientedprogramming) and the ability to interface smoothly withprograms written in the C language. A relatively minor furtherrevision has the tentative name FORTRAN 2008.Sample ProgramThe following simple example illustrates some features of atraditional FORTRAN program:INTEGER INTARRAY(10)INTEGER ITEMS, COUNTER, SUM, AVGSUM = 0READ *, ITEMSDO 10 COUNTER = 1, ITEMSREAD *, INTARRAY(COUNTER)SUM = SUM + INTARRAY(COUNTER)10 CONTINUEAVG = SUM / ITEMSPRINT ‘SUM OF ITEMS IS: ’, SUMPRINT ‘AVERAGE IS: ’, AVGSTOPENDThe program creates an array holding up to ten integers(see array). The first number it reads is the number of itemsto be added up. It stores this in the variable ITEMS. A DOloop statement then repeats the following two statementsonce for each number from 1 to the total number of items.Each time the two statements are executed, COUNTER isincreased by 1. The statements read the next number fromthe array and add it to the running total in SUM. Finally, theaverage is calculated and the sum and average are printed.Like its contemporary, COBOL, Fortran is viewed bymany modern programmers as a rather clumsy and anachronisticlanguage (because of its use of line number references,for example). However, there is a tremendous legacyof tested, reliable Fortran code and powerful math libraries.(For example, a Fortran program can call library routinesto quickly get the sum or cross-product of any array ormatrix.) These features ensure that Fortran has continuingappeal and utility to users who are more concerned withgetting fast and accurate results than with the niceties ofprogramming style.Further ReadingChapman, Stephen J. Fortran 95/2003 for Scientists & Engineers.3rd ed. New York: McGraw-Hill, 2007.Chivers, Ian, and Jane Sleightholme. Introduction to Programmingwith Fortran: With Coverage of Fortran 90, 95, 2003 and 77.New York: Springer, 2005.

functional languages 203Page, Clive. “Clive Page’s List of Fortran Resources.” Availableonline. URL: http://www.star.le.ac.uk/~cgp/fortran.html.Accessed August 4, 2007.Reid, John. “The Future of Fortran.” Available online. URL: http://www.ieeexplore.ieee.org/iel5/5992/27213/01208645.pdf.Accessed August 4, 2007.fractals in computingFractals and the related idea of chaos have profoundlychanged the way scientists think about and model theworld. Around 1960, Benoit Mandelbrot noticed that supposedlyrandom economic fluctuations were not distributedevenly but tended to form “clumps.” As he investigated othersources of data, he found that many other things exhibitedthis odd behavior. He also discovered that the patterns ofdistribution were “self-similar”—that is, if you magnified aportion of the pattern it looked like a miniature copy of thewhole. Mandelbrot coined the term fractal (meaning fractured,or broken up) to describe such patterns. Eventually,a number of simple mathematical functions were found toexhibit such behavior in generating values.Fractals offered a way to model many phenomena innature that could not be handled by more conventionalgeometry. For example, a coastline that might be measuredas 1,600 miles on a map might be many thousands of mileswhen measured on local maps, as the tiny inlets at everybay and beach are measured. Fractal functions could replicatethis sort of endless generation of detail in nature.Fractals showed that seemingly random or chaotic datacould form a web of patterns. At the same time, Mandelbrotand others had discovered that the pattern radicallydepended on the precise starting conditions: A very slightdifference at the start could generate completely differentpatterns. This “sensitive dependence on initial conditions”helped explain why many phenomena such as weather (asopposed to overall climate) resisted predictability.Computing ApplicationsMany computer users are familiar with the colorful fractalpatterns generated by some screen savers. There are hundredsof “families” of fractals (beginning with the famousMandelbrot set) that can be color-coded and displayed inendless detail. But there are a number of more significantapplications. Because of their ability to generate realistictextures at every level of detail, many computer games andsimulations use fractals to generate terrain interactively.Fractals can also be used to compress large digital imagesinto a much smaller equivalent by creating a mathematicaltransformation that preserves (and can be used to recreate)the essential characteristics of the image. Militaryexperts can use fractal analysis either to distinguish artificialobjects from surrounding terrain or camouflage, or togenerate more realistic camouflage. Fractals and chaos theoryare likely to produce many surprising discoveries in thefuture, in areas ranging from signal analysis and encryptionto economic forecasting.Further ReadingFractal Resources & Links. Available online. URL: http://home.att.net/~Novak.S/resources.htm. Accessed August 4, 2007.Gleick, J. Chaos: The Making of a New Science. New York: Viking,1987.Mandelbrot, Benoit. The Fractal Geometry of Nature. New York:W.H. Freeman, 1982.Peitgen, Heinz-Otto, Hartmunt Jüurgens, and Dietmar Saupe.Chaos and Fractals. 2nd ed. New York: Springer, 2004.A Mandelbrot fractal generated using Adobe PhotoShop and theKPT (Kai’s Power Tools) Fraxplorer filter. (Lisa Yount)functional languagesMost commonly used computer languages such as C++and FORTRAN are imperative languages. This means thata statement is like a “sentence” in which the value of anexpression or the result of a function is used in some way,such as assigning it to another variable or printing it. Forexample:A = cube(3)passes the parameter 3 to the cube function, which returnsthe value 27, which is then assigned to the variable A.In a functional language, the values of functions are notassigned to variables (or stored in intermediate locations asfunctions are evaluated). Instead, the functions are manipulateddirectly, together with data items (atoms) arrangedin lists. The earliest (and still best-known) functional languageis LISP (see lisp). Programming is accomplished by

204 fuzzy logicdefining and arranging functions until the desired processingis accomplished. (The decision making accomplishedby branching statements in imperative languages is accomplishedby incorporating conditionals in function definitions.)Many functional languages (including LISP) for convenienceincorporate some features of imperative languages.The ML language, for example, includes data type declarations.A similar language, Haskell, however, eschews allsuch imperative features.ApplicationsFunctional languages have generally been used for specializedpurposes, although they can in principle perform anytask that an imperative language can. APL, which is basicallya functional language, has devotees who appreciate itscompact and powerful syntax for performing calculations(see apl). LISP and its variants have long been favored formany artificial intelligence applications, particularly naturallanguage processing, where its representation of data aslists and the facility of its list-processing functions seems anatural fit.Proponents of functional languages argue that they freethe programmer from having to be concerned with explicitlysetting up and using variables. In a functional language,problems can often be stated in a more purely mathematicalway. Further, because functional programs are not organizedas sequentially executed tasks, it may be easier toimplement parallel processing systems using functionallanguages.However, critics point out that imperative languages aremuch closer to how computers actually work (employingactual storage locations and sequential operation) and thusproduce code likely to be much faster and more efficientthan that produced by functional languages.Further ReadingBird, R. Introduction to Functional Programming Using Haskell. 2nded. London: Prentice Hall, 1998.Hudak, Paul. The Haskell School of Expression: Learning FunctionalProgramming through Multimedia. New York: Cambridge UniversityPress, 2000.Michaelson, Greg, Phil Trinder, and Hans-Wolfgang. Loidl, eds.Trends in Functional Programming. 2 vols. Portland, Oreg.:Intellect, 2000.Thompson, S. Haskell. Miranda: The Craft of Functional Programming.2nd ed. Reading, Mass.: Addison-Wesley, 1996.fuzzy logicAt bottom, a data bit in a computer is “all or nothing”(1 or 0). Most decisions in computer code are also all ornothing: Either a condition is satisfied, and execution takesone specified path, or the condition is not satisfied and itgoes elsewhere. In real life, of course, many situations fallbetween the cracks. For example, a business might want totreat a credit applicant who almost qualifies for “A” statusdifferent from one who barely made “B.” While a programcould be refined to include many gradations between B andA, another approach is to express the degree of “closeness”(or certainty) using fuzzy logic.In 1965, mathematician L. A. Zadeh introduced the conceptof the fuzzy set. In a fuzzy set, a given item is notsimply either a member or not a member of a specified set.Rather, there is a degree of membership or “suitability”somewhere between 0 (definitely not a member) and 1 (definitelya member). A program using fuzzy logic must includea variety of rules for determining how much certainty toassign in a given case. One way to create rules is to askexperts in a given field (such as credit analysis) to articulatethe degree of certainty or confidence they would feel in agiven set of circumstances. For physical systems, data canalso be correlated (such as the relationship of temperatureto the likelihood of failure of a component) and used to createa rule to be followed by, for example, a chemical processcontrol system.Fuzzy logic is particularly applicable to the creation ofprograms (see expert system) that are better able to copewith uncertainty and the need to weigh competing factorsin coming to a decision. It can also be used in engineeringto allow designers to specify which factors they wantto tightly constrain (such as for safety reasons) and whichcan be allowed more leeway. The system can then come upwith optimized design specifications. Fuzzy logic has alsobeen applied to areas such as pattern recognition and imageanalysis where a number of uncertain observations mustoften be accumulated and a conclusion drawn about theoverall object.Further ReadingBojadziev, George, and Maria Bojadziev. Fuzzy Logic for Business,Finance, and Management. 2nd ed. Hackensack, N.J.: WorldScientific Publishing Co., 2007.“Fuzzy Logic Tutorial.” Encoder (Seattle Robotics Society). March1998. Available online. URL: http://www.seattlerobotics.org/encoder/mar98/fuz/flindex.html. Accessed August 4,2007.Mendel, Jerry M. Uncertain Rule-Based Fuzzy Logic Systems: Introductionand New Directions. Upper Saddle River, N.J.: PrenticeHall PTR, 2000.Nguyen, Hung T., and Elbert A. Walker. A First Course in FuzzyLogic. 3rd ed. Bocal Raton, Fla.: Chapman & Hall/CRC,2006.Sanchez, E. Fuzzy Logic and the Semantic Web. Amsterdam: Elsevier,2006.

Ggame consolesGame consoles are computer devices dedicated to (or primarilyused for) playing video games. The earliest suchdevices appeared in the 1970s from Magnavox and thenAtari, and could only play simple games like Pong (a crudesimulation of ping-pong). Slightly later systems began tofeature cartridges that allowed them to play a greater varietyof games.After a shakeout in the late 1970s, Atari revived thevideo game industry with its hit game Space Invaders.However, this was followed by another industry crash asthe market became glutted by often imitative and inferiorgames. The next leader was Nintendo, with its own hit,Super Mario Brothers. By the end of the 1980s another Japanesefirm, Sega, had entered the American market.During the 1990s consoles grew in power and graphicsophistication. CDs (and later DVDs) replaced cartridgesand allowed for larger, more complex games. By the end ofthe decade the main competitors were the Sony Playstation2 and the Nintendo 64 (indicating a 64-bit processor) andGameCube. Meanwhile Microsoft entered the game consolemarket with its Xbox, which featured a more PC-like architectureincluding a built-in hard drive (soon also adoptedby Sony).New TechnologiesA technology with applications far beyond games is the“cell chip” technology introduced by Sony in its Play-Station 3, introduced in late 2006. The Sony cell chiphas seven cores and can reach nearly supercomputer-scalespeeds (and in fact is being used to create impromptusupercomputers).Sony also opted to include a high-definition “Blu-ray”DVD player in the PS3, strengthening its application as amedia device as well as a gaming device, with Microsoftand its Xbox 360 initially opting for the ultimately unsuccessfulHD DVD.Nintendo’s Wii, the third major competitor as of 2007,innovates in a different area: the user interface. The Wiicomes with a controller that can track both where it ispointing and how it is being used, allowing for rather realisticsports and combat simulations.Further ReadingAmirch, Dan. PlayStation 2 for Dummies. New York: HungryMinds, 2001.Farkas, Bart G. The Nintendo Wii Pocket Guide. Berkeley, Calif.:Peachpit Press, 2007.Forster, Winnie. The Encyclopedia of Game Machines. Utting, Germany:Game Plan, 2005.Johnson, Brian. Xbox 360 for Dummies. Hoboken, N.J.: Wiley,2006.Kent, Steven L. The Ultimate History of Video Games. New York:Three Rivers Press, 2001.Kim, Ryan. “New Era of Game Devices Arrives: Sony and NintendoMeet the Challenge of Microsoft’s Xbox.” San FranciscoChronicle, November 13, 2006, p. F-1. Available online. URL:http://sfgate.com/cgi-bin/article.cgi?file=/c/a/2006/11/13/BUGS1MAGAN1.DTL. Accessed September 21, 2007.Nintendo. Available online. URL: http://www.nintendo.com.Accessed September 21, 2007.Playstation (Sony). Available online. URL: http://www.us.playstation.com/. Accessed September 21, 2007.205

206 Gates, William, IIIGame consoles such as this Microsoft Xbox are now more powerfulthan many desktop computers. (Microsoft Corporation)Takahashi, Dean. The Xbox 360 Uncloaked: The Real Story BehindMicrosoft’s Next-Generation Video Game Console. Spiderworks,2006.Xbox (Microsoft). Available online. URL: http://www.microsoft.com/xbox/. Accessed September 21, 2007.Gates, William, III (Bill)(1955– )AmericanEntrepreneur, ProgrammerBill Gates built Microsoft, the dominant company in thecomputer software field and in doing so, became the world’swealthiest individual, with a net worth measured in thetens of billions. Born on October 28, 1955, to a successfulprofessional couple in Seattle, Gates’s teenage years coincidedwith the first microprocessors becoming available toelectronics hobbyists.Gates showed both technical and business talent as earlyas age 15, when he developed a computerized traffic-controlsystem. He sold his invention for $20,000, then droppedout of high school to work as a programmer for TRW forthe very respectable salary of $30,000. By age 20, Gateshad returned to his schooling and become a freshman atHarvard, but then he saw a cover article in Popular Electronics.The story introduced the Altair, the first commerciallyavailable microcomputer kit.Gates believed that microcomputing would soon becomea significant industry. To be useful, however, the newmachines would need software, and Gates and his friendPaul Allen began by creating an interpreter for the BASIClanguage that could run in only 4 KB of memory, makingit possible for people to write useful applications withouthaving to use assembly language. This first product wasquite successful, although to Gates’s annoyance it was illicitlycopied and distributed for free.In 1975, Gates and Allen formed the Microsoft Corporation.Most of the existing microcomputer companies,including Apple, Commodore, and Tandy (Radio Shack)signed agreements to include Microsoft software with theirmachines. However, the big breakthrough came in 1980,when IBM decided to market its own microcomputer. Whennegotiations for a version of CP/M (then the dominant operatingsystem) broke down, Gates agreed to supply IBM witha new operating system. Buying one from a small Seattlecompany, Microsoft polished it a bit and sold it as MS-DOS1.0. Sales of MS-DOS exploded as many other companiesrushed to create “clones” of IBM’s hardware, each of whichneeded a copy of the Microsoft product.In the early 1980s, Microsoft was only one of manythriving competitors in the office software market. Wordprocessing was dominated by such names as WordStarand WordPerfect, Lotus 1-2-3 ruled the spreadsheet roost,and dBase II dominated databases (see word processing,spreadsheet, and database management system). ButGates and Microsoft used the steady revenues from MS-DOS to undertake the creation of Windows, a much largeroperating system that offered a graphical user interface (seeuser interface). While the first versions of Windows wereclumsy and sold poorly, by 1990 Windows (with versions3.1 and later, 95 and 98) had become the new dominant OSand Microsoft’s annual revenues exceeded $1 billion (seeMicrosoft Windows). Gates relentlessly leveraged boththe company’s technical knowledge of its own OS and itsnear monopoly in the OS sector to gain a dominant marketshare for the Microsoft word processing, spreadsheet, anddatabase programs.By the end of the decade, however, Gates and Microsoftfaced formidable challenges. The growth of the Internet andthe use of the Java language with Web browsers offered anew way to develop and deliver software, potentially gettingaround Microsoft’s operating system dominance (see Java).That dominance, itself, was being challenged by Linux, aversion of LINUX created by Finnish programmer LinusTorvalds (see linux). Gates responded that Microsoft, too,would embrace the networked world and make all its softwarefully integrated with the Internet and distributable innew ways.However, antitrust lawyers for the U.S. Department ofJustice and a number of states began legal action in the late1990s, accusing Microsoft of abusing its monopoly status

genetic algorithms 207by virtually forcing vendors to include its software withtheir systems. In 2000, a federal judge agreed with the government.In November 2002, an appeals court accepted aproposed settlement that would not break up Microsoft butwould instead restrain a number of its unfair business practices.Gates’s personality often seemed to be in the center ofthe ongoing controversy about Microsoft’s behavior. Positively,he has been characterized as having incredibleenergy, drive, and focus in revolutionizing the developmentand marketing of software.On the other hand, Gates has been unapologetic abouthis dominance of the market. During the 1990s he oftenappeared defensive and abrasive in giving legal depositionsor making public statements. As an executive, he has at timesshown little tolerance for what he considers to be incompetenceor shortsightedness on the part of subordinates.There is another face to Bill Gates: He is one of theleading philanthropists of our time. In 2000 he and hiswife founded the Bill and Melinda Gates Foundation. Thefoundation’s endowment was about $33 billion by 2006,and Warren Buffet pledged to nearly double that throughstock donations. The foundation gives over $800 million ayear to global health programs (including vaccination programs),supports a variety of global development efforts,and donates money and software to libraries and educationalinstitutions. In June 2006 Gates announced that hewould be withdrawing from involvement in the day-to-dayaffairs of Microsoft, in order to devote more time to philanthropy.Since 2004, Gates has been featured on Time magazine’sannual list of 100 most influential people. In 2005, themagazine made Gates, along with his wife and U2’s leadsinger Bono, “Persons of the Year.” Gates has also receivedfour honorary doctorates.Further ReadingBank, David. Breaking Windows: How Bill Gates Fumbled the Futureof Microsoft. New York: Free Press, 2001.Bill & Melinda Gates Foundation. Available online. URL: http://www.gatesfoundation.org/default.htm. Accessed August 5,2007.Lesinski, Jeanne M. Bill Gates (Biography A&E). Rev. ed. Minneapolis:Lerner Publications, 2007.Lowe, Jane C. Bill Gates Speaks: Insights from the World’s GreatestEntrepreneur. New York: Wiley, 1998.Markoff, John. “Exit, Pursued by 1,000 Bears (Microsoft Corp.’sBill Gates)” New York Times, July 30, 2007, p, C1.Wallace, James, and Jim Erickson. Hard Drive: Bill Gates and theMaking of the Microsoft Empire. New York: HarperBusiness,1993.Bill Gates is the multibillionaire cofounder of Microsoft Corporation,the leader in operating systems and software for personalcomputers. The company has faced antitrust actions since thelate 1990s. (Microsoft Corporation)genetic algorithmsThe normal method for getting a computer to perform atask is to specify the task clearly, choose the appropriateapproach (see algorithm), and then implement and testthe code. However, this approach requires that the programmerfirst know the appropriate approach, and evenwhen there are many potentially suitable algorithms, it isn’talways clear which will prove optimal.Starting in the 1960s, however, researchers began toexplore the idea that an evolutionary approach might beadaptable to programming. Biologists today know thatnature did not begin with a set of highly optimized algorithms.Rather, it addressed the problems of survivalthrough a proliferation of alternatives (through mutationand recombination) that are then subjected to natural selection,with the fittest (most successful) organisms survivingto reproduce. Researchers began to develop computer programsthat emulated this process.A genetic program consists of a number of copies of aroutine that contain encoded “genes” that represent elementsof algorithms. The routines are given a task (suchas sorting data or recognizing patterns) and the most successfulroutines are allowed to “reproduce” by exchanginggenetic material. (Often, further “mutation” or variation isintroduced at this stage, to increase the range of availablesolutions.) The new “generation” is then allowed to tacklethe problem, and the process is repeated. As a result, theroutines become increasingly efficient at solving the givenproblem, just as organisms in nature become more perfectlyadapted to a given environment.

208 Geographical Information SystemsApplicationsVariations of genetic algorithms or “evolutionary programming”have been used for many applications. In engineeringdevelopment, a virtual environment can be set up in whicha simulated device such as a robot arm can be allowed toevolve until it is able to perform to acceptable specifications.(NASA has also used genetic programs competing on80 computers to design a space antenna.) Different versionsof an expert system program can be allowed to compete atperforming tasks such as predicting the behavior of financialmarkets. Finally, a genetic program is a natural way tosimulate actual biological evolution and behavior in fieldssuch as epidemiology (see also artificial life).Further Reading“Bibliography on Genetic Programming.” Available online. URL: http://liinwww.ira.uka.de/bibliography/Ai/genetic.programming.html. Accessed August 5, 2007.Brown, Chappell. “Darwin’s Ideas Evolve Design.” EE Times, February6, 2006. Available online. URL: http://www.eetimes.com/showArticle.jhtml?articleID=178601156. Accessed August 5,2007.Eiben, A. E., and J. E. Smith. Introduction to Evolutionary Computing.New York: Springer, 2003.Genetic-programming.org [Resources]. Available online. URL: http://www.genetic-programming.org/. Accessed August 5, 2007.“The GP Tutorial.” Available online. URL: http://www.geneticprogramming.com/Tutorial/. Accessed August 5, 2007.Keats, Jonathon. “John Koza Has Built an Invention Machine.”Popular Science, April 2006. Available online. URL: http://www.popsci.com/popsci/science/0e13af26862ba010vgnvcm1000004eecbccdrcrd.html. Accessed August 5, 2007.Langdon, William B., and Riccardo Poli. Foundations of GeneticProgramming. New York: Springer, 2002.Riolo, Rick, and Bill Worzel, eds. Genetic Programming Theoryand Practice. Norwell, Mass.: Kluwer Academic Publishers,2003.Geographical Information SystemsCartography, or the art of mapmaking, has been transformedin many ways by the use of computers. Traditionally,mapmaking was a tedious process of recording, compiling,and projecting or plotting information about the location,contours, elevation, or other characteristics of natural geographicfeatures or the demographic or political structureof human communities.Instead of being transcribed from the readings of surveyinginstruments, geographic information can be acquiredand digitized by sensors such as cameras aboard orbitingsatellites. The availability of such extensive, detailedinformation would overwhelm any manual system of transcribingor plotting. Instead, the Geographical InformationSystem (GIS, first developed in Canada in the 1960s)integrates sensor input with scanning and plotting devices,together with a database management system to compilethe geographic information.The format in which the information is stored is dependenton the scope and purpose of the information system. Adetailed topographical view, for example, would have physicalcoordinates of latitude, longitude, and elevation. On theother hand, a demographic map of an urban area mightA raster grid showing annual rainfall totals in inches for mythicalSquare County. Raster data is easy to work with, but the “coarseness”of the grid means that it does not capture much local variationor detail.have regions delineated by ZIP code or voting precinct, orby individual address.Geographic data can be stored as either a raster or avector representation. A raster system divides the area intoa grid and assigns values to each cell in the grid. For example,each cell might be coded according to its highest pointof elevation, the amount of vegetation (ground cover) it has,its population density, or any other factor of interest. Thesimple grid system makes raster data easy to manipulate,but the data tends to be “coarse” since there is no informationabout variations within a cell.Unlike the arbitrary cells of the raster grid, a vector representationis based upon the physical coordinates of actualpoints or boundaries around regions. Vector representationis used when the actual shapes of an entity are important,as with property lines. Vector data is harder to manipulatethan raster data because geometric calculations must bemade in order to yield information such as the distancebetween two points.The power of geographic information systems comes fromthe ability to integrate data from a variety of sources, whetheraerial photography, census records, or even scanned papermaps. Once in digital form, the data can be represented in avariety of ways for various purposes. A sophisticated gis canbe queried to determine, for example, how much of a proposeddevelopment would have a downhill gradient and bebelow sea level such that flooding might be a problem. Theseresults can in turn be used by simulation programs to determine,for example, whether release of a chemical into thegroundwater from a proposed plant site might affect a particulartown two miles away. Geographic information systemsare thus vital for the management of a variety of complexsystems that are distributed over a geographical area, suchas water and sewage systems, power transmission grids, andtraffic control systems. Other applications include emergencyplanning (and evacuation routes) and the long-term study ofthe effects of global warming trends.

globalization and the computer industry 209from information to navigationThe earliest use of maps was for facilitating navigation.The development of the Global Positioning System (GPS)made it possible for a device to triangulate readings fromthree of 24 satellites to pinpoint the user’s position onEarth’s surface within a few meters (or even closer in militaryapplications). The mobile navigation systems thathave now become a consumer product essentially use thecurrent physical coordinates to look up information in theonboard geographical information system. Depending onthe information stored and the user’s needs, the resultingdisplay can range from a simple depiction of the user’slocation on a highway or city street map to the generatingof detailed driving directions from the present locationto a desired location. As these systems are fitted withincreasingly versatile natural language systems (and perhapsvoice-recognition capabilities), the user will be ableto ask questions such as “Where’s the nearest gas station?”or even “Where’s the nearest French restaurant rated atleast three stars?”Further ReadingBurrough, P.A., and R. McDonnell. Principles of Geographical InformationSystems. 2nd ed. New York: Oxford University Press,1998.Demers, M. N. Fundamentals of Geographic Information Systems.New York: Wiley, 1997.Longley, P. A., (and others) eds. Geographical Information Systems:Principles, Techniques, Management and Applications. NewYork: Wiley, 1998.Ramadan, K. “The Use of GPS for GIS Applications.” http://www.geogr.muni.cz/lgc/gis98/proceed/RAMADAN.htmlU.S. Geological Survey. “Geographic Information Systems.” http://www.usgs.gov/research/gis/title.html.globalization and the computer industryGlobalization can be described as a group of trends thatare breaking down the boundaries between national andregional economies, making countries more dependent onone another, and resulting in the freer flow of labor andresources. These trends have been praised by free tradeadvocates and decried by proponents of labor rights andenvironmentalism. However one feels about them, it isclear that global trends are reshaping the computer andinformation industry in many ways, and pose significantchallenges.Global trends that affect computer technology, software,and services include:• offshoring, or the continuing movement of manufacturingof high-value components (and whole systems)from the industrialized West to regions such as Asia• outsourcing—moving functions (such as technicalsupport) from a company’s home country to areaswhere suitable labor forces are cheaper (see employmentin the computer field)• removal of traditional intermediaries such as brokersand agents, with some of their functions being takenover by software (see software agent)• decentralized networks (of which the Internet itselfis the most prominent example) and the tendency ofinformation to flow freely and quickly despite barrierssuch as censorship• virtualization—creation of work groups or wholecompanies that are distributed across both spaceand time (24 hours), coordinated by the Internet andmobile communications (see virtualization)• increasing use of open-source and collaborative modelsof software and information development (seeopen source)• blurring of the distinction between consumers andproducers of information (see social networkingand user-created content)These global trends can be divided roughly into three categories:movement of labor and resources, restructuring ofmarkets, and changes in the nature and flow of production.Movements and ShiftsOffshoring is the movement of manufacturing operationsfrom the traditional developed industrial nations (suchas the United States and Europe) to developing nations(see also developing nations and computing). Theprincipal motivation for this (as well as outsourcing, themovement of corporate functions and services) is lowerlabor and related costs. India, with its large populationof well-trained, English-speaking workers, was the firstbeneficiary of these trends in the 1990s. Many major U.S.computer companies such as IBM, Intel, Microsoft, andHP have made major investments in software developmentoperations in India. However, it should be notedthat offshoring/outsourcing is a truly global trend, withother industrialized nations taking advantage of similarsituations, particularly where there are language compatibilities.Thus Japanese companies have invested heavilyin China, while Germans and other Europeans have preferredto look toward Eastern Europe.Besides lower costs, outsourcing can speed developmentby taking advantage of differences in time zones, allowingfor coordinated 24-hour production cycles.Free-Trade ControversiesProponents of these trends generally include them underthe umbrella of “free trade.” Their arguments include:• greater productivity through more efficient tapping oftalent and resources• improvement in the standard of living in developingnations• lower prices for goods and services in developednations• spurring innovation through competition and themovement of displaced workers to higher-value jobsOpponents point to a number of serious problems andissues, including:

210 Google• downward wage pressure and/or unemployment asworkers in developed nations are displaced by offshoreworkers• difficulty in retraining displaced workers• lack of adequate protective regulations and laborrights for workers in developing nations• potential deterioration in the quality of services (suchas technical support) after outsourcing• risks of dependence on offshore supply sources intimes of crisisRestructuring of MarketsComputer-related businesses must also deal with the effectsof globalization on the market for hardware, software, andservices. Lower-cost offshore manufacturing has helpedcontribute to making many computer systems and peripheralsinto commodity items. This certainly benefits consumers(consider the ubiquitous $100 or less computer printer).However, it becomes more difficult to extract a premiumfor a brand as opposed to a generic name. Some companieshave responded by relentless efforts to maximize efficiencyin manufacturing (for example, see Dell, Inc.), while a fewothers have maintained a reputation for style or innovation(see Apple, Inc.). Consumers have increasingly objected,however, to the difficulty in dealing with offshore technicalsupport.While the power of the Internet has opened many newways of reaching potential customers around the world,dealing with a global marketplace brings considerableadded complications, such as the need to deal with differentregulatory systems (such as the European Union). In someareas (notably Asia) there is also the problem of unauthorizedcopying of software and media products (see softwarepiracy and counterfeiting).New Ways of WorkingA global, connected economy is not only changing wherework is done, but also how it is done. If a software developer,for example, has operations in the United States,Europe, India, and China, at any time of day there willbe work going on somewhere. With the complexity andspeed of operations, managers in the United States mayhave to keep quite long and irregular hours in order tohave real-time communication with counterparts abroad.This interaction is made possible by a variety of technologies,including Internet-based phone and video conferencingand, of course, e-mail. However, this is not withoutadded stress. Overall operations can be structured to takeadvantage of the time zone differences. Code or documentswritten in Bangalore might be reviewed and revised in SiliconValley the same day.Global trends are likely to continue and even accelerateas the computer and information industry continues todevelop around the world. While technology can help dealwith some of the challenges, there are many larger economicand political issues involved, and whether they canbe satisfactorily resolved may ultimately have the greatestimpact on the industry.Further ReadingBlinder, Alan E. “Offshoring: The Next Industrial Revolution?”Foreign Affairs 85 (March/April 2006): 113–128.Carmel, Erran, and Paul Tjia. Offshoring Information Technology:Sourcing and Outsourcing to a Global Workforce. New York:Cambridge University Press, 2005.Currie, Wendy. The Global Information Society. New York: Wiley,2000.Friedman, Thomas L. The World Is Flat: A Brief History of theTwenty-First Century. 2nd rev. ed. New York: Picador, 2007.Quinn, Michelle. “Working Around the Clock.” Los Angeles Times,June 19, 2007. Available online. URL: http://www.latimes.com/news/la-fi-timezone19jun19,1,7843626.story?ctrack=1&cset=true. Accessed September 21, 2007.Samii, Massood, and Gerald D. Karush, eds. International Business& Information Technology. New York: Routledge, 2004.Sood, Robin. IT, Software, and Services: Outsourcing and Offshoring:The Strategic Plan with a Practical Viewpoint. Austin, Tex.:AiAiYo Books, 2005.Steger, Manfred B. Globalization: A Very Short Introduction. NewYork: Oxford University Press, 2003.GoogleGoogle Inc. (NASDAQ symbol: GOOG) has built a businesscolossus by focusing on helping users find what theyare looking for on the Internet while selling advertisingtargeted at those same users. By 2006, “to google” could befound in dictionaries as a verb meaning to look up anyoneor anything online.Google was founded by two Stanford students (see Brin,Sergey and Page, Larry) who, for their doctoral thesis,had described a Web search algorithm that could give a betteridea of the likely relevance of a given site based on thenumber of sites that linked to it. The two students implementeda search engine based on their ideas and hosted iton the Stanford Web site, where its popularity soon irritatedthe university’s system administrators. In 1998 theirbusiness was incorporated as Google, Inc., and moved tothe archetypal Silicon Valley entrepreneur’s location—afriend’s garage. However, as the company attracted investmentcapital and grew rapidly, it moved to Palo Alto andthen its present home in Mountain View.Google’s initial public stock offering was in 2004, andthe market’s enthusiastic response made many senioremployees instant millionaires. Google’s steady growth insubsequent years has kept its stock in demand, reaching arecord peak of $560 in September 2007. (In 2006 Googlewas added to the S&P 500 Index.)Search and Its Larger ContextPeople tend to think of Google as a search engine. Actually,it is better to think of it as an ever-expanding networkof Web-based services that include general andspecialized searches but also tools for content creationand collaboration.It is true that search and the accompanying advertisingare the core of Google’s revenue and thus the engine that

Google 211drives its proliferation. In 2000 Google adopted keywordbasedadvertising. (This was not a new idea, but Googlewas the first to really make it work.) Basically, advertisersbid for the right to have their ad accompany the results of asearch that contains a given word, on a per “click through”basis—that is, how often the user clicks on the ad to go tothe advertiser’s site. Advertisers are prioritized accordingto how much they bid, their previous click-through rate,and their ad’s relevance to the search. If someone searches,for example, “widget” and Acme Widget Co. is in line forplacement, the Acme ad is shown. If the user then clicks onit, Acme makes a payment to Google (and hopes to somebusiness).The power of keyword-based and other “contextual”advertising is that, by definition, any accompanying ad istargeted to someone who is quite probably already lookingfor what one is selling. And what makes this such arevenue-maker for Google is that, since the company servesover half of all Web searches, anyone wanting an ad toreach the biggest share of its potential audience will have toturn to Google.Google’s ability to offer more precisely targeted advertisinghas been enhanced in several ways:• AdSense, which can be installed on a Web site whereit displays ads keyed to the site’s content. Revenue isshared by Google and the site owner.• Advertisers can specify an AdWord and Google willplace it on participating sites in its “content network”that it believes are relevant. The advertiser pays perthousand viewings of the ads (“impressions”).• Specialized shopping-oriented searches such asGoogle Product Search, which returns lists of sellersand a price comparison.• Searches can also be local (particularly useful formobile devices) and results can be keyed to maps.Other ApplicationsGoogle has greatly expanded beyond its core business ofsearch and accompanying advertising. In general, the companyhas been emphasizing acquiring or developing toolsthat help users create content and collaborate. These offeringinclude:• Blogger, an easy-to-use blogging tool (see blogs andblogging)• JotSpot, developer of wiki collaboration tools (seewikis and Wikipedia)• YouTube, the largest video-sharing service, acquiredby Google in 2006 (see YouTube)• Gmail, a free e-mail service• Google Apps, which provides a Web-based office environmentincluding a calendar and Google Docs &Spreadsheets. (The standard edition is free and representsa competitive challenge for Microsoft Office, particularlyfor small businesses and simpler applications.)In addition to office and collaboration tools, Google hasseveral other prominent applications that do not easily fit inone category:• google News provides a constantly updated newspaperlikeformat that groups stories under headlines.• google Book Search offers access to thousands ofpublic-domain books and summaries or limited previewsof copyrighted works (see e-books and digitallibraries)• Google Maps and Google Earth are vast troves of mapinformation, satellite imagery, and even street-levelviews of some cities.A key to the growth of Google’s new Web services is thatmany of them come with programming interfaces that canbe used to integrate them into Web sites and applications.It is relatively easy, for example, to combine maps and dataabout stores or other locations (see mashups).CriticismAs of mid-2008 Google had more than 19,500 full-timeemployees. The company’s workplace culture at its MountainView “Googleplex” is famous for its gourmet food,elaborate recreation center, and other perks. (In 2007 Fortunemagazine rated Google first in the nation as a place towork.)Google has a market capitalization of about $180 billion,ahead of such giants as Hewlett-Packard and IBM. In 2008Google took in $16.6 billion, with $4.2 billion in profit.Google’s impact on the online world has been immense.As of mid-2007 Google was processing 54 percent of allInternet search requests, followed distantly by Yahoo! at 20percent and Microsoft at 13 percent.Google sets a high standard for itself. Its mission statementis “to organize the world’s information and make ituniversally accessible and useful.” A corporate motto is“don’t be evil” in the pursuit of success. A number of criticshave suggested, however, that Google has fallen short of itsstandards in a number of respects:• google Book Search had led to accusations of copyrightviolations by publishers and authors. Google hasalso been accused of benefiting from rampant copyingof copyrighted content on its YouTube subsidiary.• Google has been criticized for aiding China in censoringsearch results (see censorship and the Internet).• The detailed imagery available from Google Earth hasbeen criticized by some nations on security grounds,and street-level views have raised privacy questions.• Some Google practices, including the extensive use ofcookies and analysis of users’ e-mail and other content,have also aroused privacy concerns (see cookiesand data mining).• Google has also been criticized for keeping its Page-Rank system secret, making it hard to determine if itis treating users fairly.

212 government funding of computer researchIn 2007 Google acquired DoubleClick for $3.1 billion.Although the combination of the leading search companyand a major online advertising service provoked concernsabout a possible monopoly, the acquisition was approved byU.S. and European regulators.While Google continues to be a subject of both admirationand debate, it is clear that it has placed powerful toolsand enormous new resources in the hands of Web usersaround the world.Further ReadingBattelle, John. The Search: How Google and Its Rivals Rewrote theRules of Business and Transformed Our Culture. New York:Portfolio, 2005.Davis, Harold. Google Advertising Tools: Cashing In with AdSense,AdWords, and the Google APIs. Sebastapol, Calif.: O’Reilly,2006.Kopytoff, Verne. “Who’s Afraid of Google? Firms in Silicon Valleyand beyond Fear Search Giant’s Plans for Growth.” SanFrancisco Chronicle. May 11, 2007, p. A-1. Available online.URL: http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/05/11/MNGRIPPB2N1.DTL. Accessed September 22, 2007.Marshall, Perry, and Bryan Todd. Ultimate Guide to GoogleAdWords: How to Access 100 Million People in 10 Minutes.Irvine, Calif.: Entrepreneur Media, 2007.Vise, David A., and Mark Malseed. The Google Story: Inside theHottest Business, Media and Technology Success of Our Time.Canada: Random House/Delta, 2006.government funding of computer researchWhile the popular version of the story of the informationage tends to focus on lone inventors in garages or would-beentrepreneurs working out of college dorm rooms, many ofthe fundamental technologies underlying computers and networkshave been the results of government-funded projects.ENIAC, the first operational full-scale electronic digitalcomputer, was an Army Ballistic Research Laboratoryproject developed during and just after World WarII. Early computers were also sponsored and used by thearmy and navy in areas such as guided missile development,and in national laboratories such as Los Alamos,where nuclear weapons were being developed. (Later theAtomic Energy Agency and its successor in the Departmentof Energy would play a similar role in obtaining computers,in particular developing an appetite for the more powerfulmachines—see supercomputer.)The Office of Naval Research (ONR) played an importantrole in developing the underlying theory and design forcomputer architecture (see von Neumann, John), as wellas sponsoring many of the early conferences on computerscience, helping the discipline emerge.As the cold war got underway, an increasing amountof funding went to military-related technology. Since computerswere becoming essential for designing or operatingcomplex technologies in aerospace, weapons systems, andother areas, it is not surprising that computer scientistshave received a significant share of government researchdollars.A pattern of cooperation emerged between governmentagencies and companies such as Univac and particularlyIBM, who were creating the computer industry. AT&T BellLaboratories (see Bell Labs) received support for communicationsand semiconductor technology. Leading-edgeresearch funded for military purposes tended to turn upfive or ten years later in new generations of commercialproducts.Begun in the late 1950s, one of the biggest defense computingprojects was the ambitious (but only marginally successful)SAGE automated air defense system. It began withWhirlwind, the first computer designed for multitaskingand continuous, real-time operation and data storage usingmagnetic core memory. Equally innovative were the userconsoles, which pioneered such features as CRT-based outputand a touch interface using a light pen.Defense Advanced ResearchProjects Agency (DARPA)Established in 1958 and sometimes known as the AdvancedResearch Projects Agency (ARPA), this agency through itsInformation Processing Technology Office has funded orcontributed to some of the most important developments ofthe information age, including:• time-sharing computer and operating systems (MITProject Mac)• packet-switched networks; the Internet (implementedas ARPANET)• NLS, an early hypertext system (see hypertext)• artificial intelligence topics including speech recognitionARPA was unusual as a government agency in its agilemanagement. Managers were given considerable latitude tobring together the most innovative computer scientists andturn them loose with a minimum of bureaucratic oversight.Funding Academic Research andComputer ScienceAlthough military-related research has been the largestportion of government funding for computer science, othergovernment agencies have also played important roles.Vannevar Bush worked tirelessly to create a new nationalresearch infrastructure, and this eventually bore fruit inthe National Science Foundation (NSF). Starting in the1960s the NSF began with a focus on providing computersupport for the sciences, but soon concluded that universityresearchers were being crippled by lack of both computersand people who could design software. The agencybegan to directly support the funding of university computerpurchases and the development of computer scienceprograms. By 1970 the NSF was also supporting the developmentof computer networks as a way for institutions toshare resources. NSF funding for computer science andrelated activities continued to grow. In the mid-1980s NSFset up the National Center for Supercomputing Applications(NCSA), which in turn set up regional centers from whichresearchers could tap into supercomputer power through ahigh-speed network.

graphics card 213Industrial CompetitivenessBy the 1980s strong competitive threats to the U.S. computerindustry (notably from Japan) and some governmentfunding began to go to helping the American industry coordinateits research. An example is SEMATECH, the semiconductormanufacturing research consortium. (DARPAalso played an important role in the development of VLSI[very large-scale integration] circuits.)Another effort of this era was the Strategic ComputingInitiative, which was also in part a response to Japanesedevelopments—their Fifth Generation Computer Program.SCI aimed to develop hardware and software for advancedartificial intelligence projects, starting with a militaryfocus, such as autonomous vehicles, voice-controlled “glasscockpit” aircraft interfaces, and expert systems for battlemanagement.Although there is always fluctuation and changing politicalpriorities, there is no reason to believe that governmentfunding will not continue to play a very important role incomputer-related research and development. There will alsocontinue to be debates over the uses to which governmentsput computing technology, particularly in the military,intelligence, and national security areas.Further ReadingDefense Advanced Research Projects Agency (DARPA). Availableonline. URL: http://www.arpa.mil/. Accessed September 22,2007.National Center for Supercomputing Applications (NCSA). Availableonline. URL: http://www.ncsa.uiuc.edu/. Accessed September22, 2007.National Research Council. Funding a Revolution: Government Supportfor Computing Research. Washington, D.C.: National AcademiesPress, 1999. Available online. URL: http://www.nap.edu/readingroom/books/far/contents.html. Accessed September22, 2007.National Science Foundation. “Exploring the Frontiers of Computing.”Available online. URL: http://www.nsf.gov/dir/index.jsp?org=CISE. Accessed September 22, 2007.Redmond, Kent C., and Thomas M. Smith. From Whirlwind toMITRE: The R&D Story of the SAGE Air Defense Computer.Cambridge, Mass.: MIT Press, 2000.Roland, Alex, and Philip Shiman. Strategic Computing: DARPA andthe Quest for Machine Intelligence, 1983–1993. Cambridge,Mass.: MIT Press, 2002.graphics cardPrior to the late 1970s, most computer applications (otherthan some scientific and experimental ones) did not usegraphics. However, the early microcomputer systems suchas the Apple II, Radio Shack TRS-80, and Commodore PETcould all display graphics, either on a monitor or (with theaid of a video modulator) on an ordinary TV set. Whileprimitive (low resolution; monochrome or just a handful ofcolors) this graphics capability allowed for a thriving marketin games and educational software.The earliest video displays for mainstream PCs providedbasic text display capabilities (such as the MDA, ormonochrome display adapter, with 25 lines of text up to80 characters per line) plus the ability to create graphicsby setting the color of individual pixels. The typical lowendgraphics card of the early 1980s was the CGA (ColorGraphics Adapter), which offered various modes such as320 by 200 pixels with four colors. Computers marketedfor professional use offered the EGA (Enhanced GraphicsAdapter), which could show 640 by 350 pixels at 16colors.The ultimate video display standard during the timeof IBM dominance was the VGA (Video Graphics Array),which offered a somewhat improved high resolution of 640by 480 pixels at 16 colors, with an alternative of a lower320 by 280 pixels but with 256 colors. Because of its use ofa color palette containing index values, the 256 colors canactually be drawn from a range of 262,144 possible choices.VGA also marked a break from earlier standards becausein order to accommodate such a range of colors it had toconvert digital information to analog signals to drive themonitor, rather than using the digital circuitry found inearlier monitors.Modern video cards can be loosely described as implementingSVGA (Super VGA), but there are no longer discretestandards. Typical display resolutions for desktop PCstoday are 1024 by 768 or 1280 by 1024 pixels. (Laptops traditionallyhave had a lower-resolution 800 by 600 display,but many are now comparable to desktop displays.) Therange of colors is vast, with up to 16,777,216 possible colorsstored as 32 bits per pixel.Storing 32 bits (4 bytes) for each of the pixels on a 1024by 768 screen requires more than 3 megabytes. However,this is just for static images. Games, simulations, and otherapplications use moving 3D graphics. Since a computerscreen actually has only two dimensions, mathematicalalgorithms must be used to transform the representationThe basic parts of a graphics card. The card is connected to theCPU by the bus (often a special bus called the AGP, or AcceleratedGraphics Port). Graphics data can be generated by the CPU andtransferred directly to the graphics card’s memory, but most cardstoday perform a lot of the graphics processing using the card’s ownon-board processor for sophisticated 3D, textures, shading, andother effects.

214 graphics formatsof objects so they look as if they have three dimensions,appearing in proper perspective, with regard to what objectsare behind other objects, and with realistic lighting andshading (see computer graphics).Traditionally, all of the work of producing the actualscreen data was undertaken by the PC’s main processor,executing instructions from the application program anddisplay driver. By putting a separate processor on the videocard (called a video accelerator), together with its own supplyof memory (now up to 256 MB), the main system wasfreed from this burden. A new high-bandwidth connectionbetween the PC motherboard and the graphics card becameavailable with the development of the AGP (AcceleratedGraphics Port). (See bus.) Memory used on video cards isalso optimized for video operations, such as by using typesof memory such as Video RAM (VRAM) that do not need tobe refreshed as frequently.Increasingly, the algorithms for creating realistic images(such as lighting, shading, and texture mapping) are nowsupported by the software built into the video card. Ofcourse, the applications program needs a way to tell thegraphics routines what to draw and how to draw it. Insystems running Microsoft Windows, a program functionlibrary called Direct3D (part of a suite called DirectX) hasbecome the standard interface between applications andgraphics hardware. Video card manufacturers in turn haveoptimized their cards to carry out the kinds of operationsimplemented in DirectX. (A nonproprietary standard calledOpenGL has also achieved some acceptance, particularly onnon-Windows systems.)In evaluating video cards, the tradeoff is between theextent to which advanced graphic features are supportedand the number of frames per second that can be calculatedand sent to the display. If the processing becomes too complicated,the frame rate will slow down and the display willappear to be jerky instead of smooth.Further Reading“Graphics and Displays.” Tom’s Hardware. Available online. URL:http://www.tomshardware.com/graphics/index.html. AccessedAugust 5, 2007.Jones, Wendy. Beginning DirectX 10 Game Programming. Boston:Course Technology, 2007.Luna, Frank. Introduction to 3D Game Programming with DirectX9.0c: A Shader Approach. Plano, Tex.: Wordware Publishing,2006.Sanchez, Julio, and Maria P. Canton. The PC Graphics Handbook.Boca Raton, Fla.: CRC Press, 2003.Shreiner, Dave, et al. OpenGL Programming Guide. 5th ed. UpperSaddle River, N.J.: Addison-Wesley Professional, 2005.“Video Cards.” PC Guide. Available online. URL: http://www.pcguide.com/ref/video/index.htm. Accessed August 5, 2007.graphics formatsBroadly speaking, a graphics file consists of data that specifiesthe color of each pixel (dot) in an image. Since there aremany ways this information can be organized, there are avariety of graphics file formats. The most important andwidely used ones are summarized below.BMP (Windows Bitmap)In a bitmap format there is a group of bits (i.e. a binaryvalue) that specifies the color of each pixel. Windows providesstandard bitmap (BMP) formats for 1-bit (2 colorsor monochrome), 4-bit (16 colors), 8-bit (256 colors), or24-bit (16 million colors). The Windows bitmap format isalso called a DIB (device-independent bitmap) because thestored colors are independent of the output device to beused (such as a monitor or printer). The relevant devicedriver is responsible for translating the color to one actuallyused by the device. Because it is “native” to Windows, BMPis widely used, especially for program graphics resources.Bitmap formats have the advantage of storing the exactcolor of every pixel without losing any information. However,this means that the files can be very large (fromhundreds of thousands of bytes to several megabytes forWindows screen graphics). BMP and other bitmap formatsdo support a simple method of compression called runlengthencoding (RLE), where a series of identical pixels isreplaced by a single pixel and a count. Bitmap files can befurther compressed through the use of utilities such as thepopular Zip program (see data compression).EPSEPS (Encapsulated PostScript) is a vector-based rather thanbitmap (raster) format. This means that an EPS file consistsnot of the actual pixel values of an image, but the instructionsfor drawing the image (including coordinates, colors,and so on). The instructions are specified as a text file inthe versatile PostScript page description language. This formatis usually used for printing, and requires a printer thatsupports PostScript (there are also PostScript renderers thatrun entirely in software, but they tend to be slow and somewhatunreliable).GIFGIF, or Graphics Interchange Format, is a bitmapped formatpromulgated by CompuServe. Instead of reserving enoughspace to store a large number of colors in each pixel, thisformat uses a color table that can hold up to 256 colors.Each pixel contains a reference (index into) the color table.This means that GIF works best with images that have relativelyfew colors and for applications (such as Web pages)where compactness is important. GIF also uses compressionto achieve compactness, but unlike the case with JPEGit is a lossless compression called LZW. There is also a GIFformat that stores simple animations.JPEGJPEG, which stands for Joint Photographic Experts Group,is widely used for digital cameras because of its ability tohighly compress the data in a color graphics image, allowinga reasonable number of high-resolution pictures to bestored in the camera’s onboard memory. The compressionis “lossy,” meaning that information is lost during compression(see data compression). At relatively low compressionratios (such as 10:1, or 10 percent of the original image size)changes in the image due to data loss are unlikely to be

green PC 215perceived by the human eye. At higher ratios (approaching100:1) the image becomes seriously degraded. JPEG’s abilityto store thousands of colors (unlike GIF’s limit of 256)makes the format particularly suitable for the subtleties ofphotography.PCXPCX is a compressed bitmap format originally used by thepopular PC Paintbrush program. In recent years it has beenlargely supplanted by BMP and TIFF.TIFFTIFF, or Tagged Image File Format, is also a compressedbitmap format. There are several variations by differentvendors, which can lead to compatibility problems. Implementationscan use various compression methods, generallyleading to ratios of 1.5 to 1 to about 2 to 1.Further ReadingBrown, C. Wayne, and Barry J. Shepherd. Graphics File FormatsReference and Guide. Greenwich, Conn.: Manning Publications,1995.Miano, John. Compressed Image File Formats. Upper Saddle River,N.J.: Addison-Wesley Professional, 1999.“Web Style Guide: Graphics.” Available online. URL: http://webstyleguide.com/graphics/. Accessed August 5, 2007.Murray, James D., and William vanRyper. Encyclopedia of GraphicsFile Formats. 2nd ed. (on CD-ROM). Sebastopol, Calif.:O’Reilly, 1996.“Wotsit’s Format: The Programmer’s Resource.” Available online.URL: http://www.wotsit.org/. Accessed August 14, 2007.graphics tabletWhile conventional pointing devices (see mouse) are quitesatisfactory for making selections and even manipulatingobjects, many artists prefer the control available onlythrough a pen or pencil, which allows the angle and pressureof the stylus tip to be varied, creating precise lines andshading. A graphics tablet (also called a digitizing tablet) isa device that uses a specially wired pen or pencil with a flatsurface (tablet). Besides tracking the location of the pen andtranslating it into X/Y screen coordinates, the tablet alsohas pressure sensors (depending on sensitivity, the tabletMany graphics tablets use a stylus or pen. The system can track thepen’s position and, often, the amount of pressure being exerted, anddraw the line accordingly.can recognize 256, 512, or 1024 levels of pressure). In combinationwith buttons on the pen, the pressure level can beused to control the line thickness, transparency, or color.In addition, the driver software for some graphics tabletsincludes additional functions such as the ability to programthe pen to control features of such applications as AdobePhotoshop.The tablet is connected to the PC (usually through a USBport). The pen may be connected to the tablet by a tether, orit may be wireless. If the pen has an onboard battery, it canprovide additional features at the expense of weight and theneed to replace batteries occasionally.A variant implementation uses a small “puck” insteadof a pen. The puck, which can be moved smoothly over thetablet surface, often has a window with crosshairs in thecenter. This makes it particularly useful for tracing detaileddrawings such as in engineering applications.Many artists find that wielding a pen with a graphicstablet offers not only finer control, but also more naturaland less fatiguing method of input than with the mouse.Further ReadingChastain, Sue. “Before You Buy a Graphics Tablet.” Availableonline. URL: http://graphicssoft.about.com/od/aboutgraphics/a/graphicstablets.htm. Accessed August 5, 2007.Kolle, Iril C. Graphics Tablet Solutions. Cincinnati, Ohio: Muska &Lipman, 2001.Threinen-Pendarvis, Cher. The Photoshop and Painter Artist TabletBook: Creative Techniques in Digital Painting. Berkeley, Calif.:Peachpit Press, 2004.green PCThis is a general term for features that reduce the growingenvironmental impact of the manufacture or use of computers.This impact has several aspects: energy consumption,resource consumption, e-waste, and pollution and greenhouseemissions.Energy ConsumptionThe greatest part of a typical computer system’s power consumptionis from the monitor, followed by the hard driveand CPU. It follows that considerable energy can be saved ifthese components are powered down when not in use. Onthe other hand, most users do not want to go through thewhole computer startup process several times a day. Onesolution is to design a computer system so that it turns offmany components when not in use but is still able to restorefull function in a few seconds.When applied to a personal computer, the federallyadopted Energy Star designation indicates a computer systemthat includes an energy saving mode that can powerdown the monitor, hard drive, or CPU after a specifiedperiod elapses without user activity, such that the inactivesystem consumes no more than 30 watts. In the ultimateenergy-saving feature a suspend mode saves the currentstate of the computer’s memory (and thus of program operation)to a disk file. When the user presses a key (or movesthe mouse), the computer “wakes up” and reloads its memorycontents from the disk, resuming operation where it left

216 grid computingoff. By 2000, virtually all new PCs were Energy Star compliant,though many users fail to actually enable the powersavingfeatures.In July 2007 stricter Energy Star specifications for desktopPCs were adopted. Power supplies must now be at least80 percent efficient. Meanwhile, the International EnergyAgency has been promoting an initiative to reduce powerconsumption of idle PCs (and other appliances) to 1 wattor less.Resource ConsumptionComputers consume a variety of resources, starting with theirmanufacturing and packaging. Resource consumption can bereduced by building more compact units and by designingcomponents so they can be more readily stripped and recycledor reused. Adopting reusable storage media (such as rewritableCDs), recycling printer toner cartridges, and changingoffice procedures to minimize the generation of paper documentsare also ways to reduce resource consumption.E-WasteIn recent years the disposal of obsolete computers and otherelectronic equipment (“e-waste”) has been both a growingconcern and a business opportunity. There are manytoxic substances in electronics components, including lead,mercury, and cadmium. Processing e-waste to recover rawmaterials is expensive, so greater emphasis has been placedon disassembling machines and reusing or refurbishingtheir individual components. Meanwhile, many communitieshave banned disposing of e-waste in regular trash, andsome have offered opportunities to drop off e-waste at no orminimal charge. States such as California have also instituteda recycling fee that is collected upon sale of devicessuch as CRT monitors and televisions.Pollution and Greenhouse EmissionsFabrication of computer chips in more than 200 large plantsaround the world involves a variety of toxic chemicals andwaste products. The Silicon Valley alone is home to 29 toxicsites under the EPA’s Superfund Program. The shift of muchof semiconductor and computer component manufacturingto countries such as China that have less strict pollutioncontrols has also exacerbated what has become a globalproblem.Whether through regulation or enlightened self-interest,companies that want to reduce future emissions can useseveral strategies. Manufacturing equipment and processescan be modified so they create fewer toxic substances or atleast keep them from getting into the environment. Nontoxic(or less toxic) materials can be substituted wherepossible—for example, use of ozone-depleting chlorofluorocarbons(CFCs) as cleaning agents has been largely eliminated.Finally, waste can be properly sorted and disposedof, and recycled wherever feasible.Like other major manufacturing sectors, the computerindustry is also faced with the need to reduce the amountof the greenhouse gases (particularly CO 2 ) contributing toglobal warming. This mainly means further reducing theenergy consumption of new PCs. In June 2007 a numberof major players, including Google, Intel, Dell, Hewlett-Packard, Microsoft, and Sun, established the Climate SaversComputing Initiative. Going beyond Energy Star, the programis expected to reduce power consumption equivalentto 54 million tons of greenhouse gases annually—about thesame as that produced by 11 million cars or 20 large coalfiredpower plants.Further ReadingBrandon, John. “Build a Green PC.” ExtremeTech, March 2,2007. Available online. URL: http://www.extremetech.com/article2/0,1697,2097765,00.asp. Accessed August 5, 2007.Cascio, Jamais. Green PC: How to Dispose of Unwanted Tech Equipmentwithout Hassles, and Where to Find Great New EnvironmentallyFriendly Gear. PC World, May 22, 2006. Availableonline. URL: http://www.pcworld.com/article/id,125708/article.html. Accessed August 5, 2007.“Cleaner Computers? Industry to Cut Carbon.” (AP/MSNBC). June12, 2007. Available online. URL: http://www.msnbc.msn.com/id/19203144/. Accessed August 5, 2007.Esty, Daniel, and Andrew S. Winston. Green to Gold: How SmartCompanies Use Environmental Strategy to Innovate, CreateValue, and Build Competitive Advantage. New Haven, Conn.:Yale University Press, 2006.Kuehr, Ruediger, and Eric Williams, eds. Computers and the Environment:Understanding and Managing Their Impacts. Norvell,Mass.: Kluwer Academic Publishers, 2003.Weil, Nancy. “The Realities of Green Computing.” PC World,August 3, 2007. Available online. URL: http://www.pcworld.com/article/id,135509/article.html. Accessed August 5, 2007.grid computingGrid or cluster computing involves the creation of a singlecomputer architecture that consists of many separatecomputers that function much like a single machine. Thecomputers are usually connected using fast networks (seelocal area network). The purpose of the arrangementcan be to provide redundant processing in case of systemfailures, to dynamically balance a fluctuating work load,or to split large computations into many parts that can beperformed simultaneously. This latter approach to “highperformancecomputing” creates the virtual equivalent of avery large and powerful machine (see supercomputer).ArchitectureGrid and cluster architectures often overlap, but the termgrid tends to be applied to a more loosely coordinatedstructure where the computers are dispersed over a widerarea (not a local network). In a grid, the work is usuallydivided into many separate packets that can be processedindependently without the computers having to share data.Each task can be completed and submitted without waitingfor the completion of any other task. Clusters, or the otherhand, more closely couple computers to act more like asingle large machine.The first commercially successful product based on thisarchitecture was the VAXcluster released in the 1980s forDEC VAX minicomputers. These systems implemented parallelprocessing while sharing file systems and peripherals.

groupware 217In 1989 an open-source cluster solution called ParallelVirtual Machine (PVM) was developed. These clusterscould mix and match any computers that could connectover a TCP/IP network (i.e., the Internet).Current Implementations and ApplicationsClusters made from hundreds of desktop-class computerprocessors can achieve supercomputer levels of performanceat comparatively low prices. An example is the System Xsupercomputer cluster at Virginia Tech, which generates12.25 TFlops (trillion floating point operations per second)from 1100 Apple XServe G5 dual-processor desktops runningMac OS X.Additional savings and flexibility can be found inBeowulf clusters, which use standard commodity PCs runningopen-source operating systems (such as Linux) andsoftware such as the Globus Toolkit.Another type of implementation is the “ad hoc” computergrid. These are projects where users sign up to receiveand process work packets using their PC’s otherwise idletime. Examples include SETI@Home (search for extraterrestrialintelligence) and Folding@Home (protein-foldingcalculations). For more on this type of arrangement, seecooperative processing.Although there has been some recent interest in enterprisegrids, most grid computing applications are in science.The world’s most powerful computer grid, TeraGrid,is funded by the National Science Foundation and tiestogether major supercomputing and advanced computinginstallations at universities and government laboratories.Current applications for TeraGrid include weather and climateforecasting, earthquake simulation, epidemiology, andmedical visualization.Further ReadingGlobus Toolkit Homepage. Available online. URL: http://www.globus.org/toolkit/. Accessed September 23, 2007.Haynos, Matt. “Perspectives on Grid: Grid Computing—Next-Generation Distributed Computing.” IBM, January 27, 2004.Available online. URL: http://www.ibm.com/developerworks/grid/library/gr-heritage/. Accessed September 23, 2007.Kacsuk, Peter, Thomas Fahringer, and Zsolt Nemeth. Distributedand Parallel Systems: From Cluster to Grid Computing. NewYork: Springer Science/Business Media, 2007.Kopper, Karl. Linux Enterprise Cluster: Build a Highly AvailableCluster with Commodity Hardware and Free Software. SanFrancisco: No Starch Press, 2005.Plaszczak, Pawel, and Richard Wellner, Jr. Grid Computing: The SavvyManager’s Guide. San Francisco: Morgan Kaufman, 2006.Robbins, Stuart. Lessons in Grid Computing: The System Is a Mirror.New York: Wiley, 2006.TeraGrid. Available online. URL: http://www.teragrid.org/. AccessedSeptember 23, 2007.groupwareWhen PCs were first introduced into the business world,they tended to be used in isolation. Individual workerswould prepare documents such as spreadsheets and databasereports and then print them out and distribute themas memos, much in the way of traditional paper documents.However, as computers began to be tied together into localarea networks (see local area network) in the 1980s,focus began to shift toward the use of software to facilitatecommunication, coordination, and collaboration amongworkers. This loosely defined genre of software was dubbedgroupware.Popular groupware software suites such as Lotus Notesand Microsoft Exchange generally offer at least some of thefollowing features:• e-mail coordination, including the creation of group ortask-oriented mail lists• shared calendar, giving each participant informationabout all upcoming events• meeting management, including scheduling (ensuringcompatibility with everyone’s existing schedule)and facilities booking• scheduling tasks with listing of persons responsiblefor each task, progress (milestones met), and checkingoff completed tasks• real-time “chat” or instant message capabilities• documentation systems that allow a number of peopleto make comments on the same document and seeand respond to each other’s comments• “whiteboard” systems that allow multiple users todraw a diagram or chart in real time, with everyoneable to see and possibly modify itGroupware is increasingly integrated with the Internet,with documents and shared resources (calendars, schedules,and so on) implemented in HTML as Web pages orWeb-linked databases. (See also personal informationmanager.)An attractive alternative to locally installed groupwareis a suite of collaboration and productivity applicationsdelivered directly via the Web and accessible using onlya Web browser. Google introduced such a package calledGoogle Apps in 2007. It has a free basic version but isexpected to offer fee-based enhanced services for largerorganizations.Groupware is likely to be an increasingly importantaspect of institutional information processing in a global,mobile economy. With workgroups often geographicallydistributed (as well as including telecommuters), traditionalface-to-face meetings become increasingly impractical aswell as often being considered wasteful and inefficient. Newforms of collaboration are supplementing the traditional e-mail and conferencing (see blogs and blogging and wikisand Wikipedia). Wikis are particularly interesting in thatthey can not only track current resources, but also providea knowledge base with lasting value.Further ReadingAndriessen, J. H. Erik. Working with Groupware: Understandingand Evaluating Collaboration Technology. New York: Springer,2003.Boles, David. Google Apps Administrator Guide: A Private-Label WebWorkspace. Boston: Course Technology, 2007.

218 Grove, Andrew S.Cavalancia, Nick. Microsoft Exchange Server 2007: A Beginner’sGuide. 2nd ed. Berkeley, Calif.: McGraw-Hill Osborne Media,2007.Google Apps. Available online. URL: https://www.google.com/a/.Accessed August 5, 2007.Gookin, Dan. Google Apps for Dummies. Hoboken, N.J.: Wiley,2008.Morimoto, Rand, et al. Microsoft Exchange Server 2007 Unleashed.Indianapolis: Sams, 2007.Munkvold, Bjorn Erik, et al. Implementing Collaboration Technologiesin Industry. New York: Springer, 2003.Udell, Jon. Practical Internet Groupware. Sebastapol, Calif.:O’Reilly, 1999.Grove, Andrew S.(1936– )Hungarian-AmericanEntrepreneurAndrew Grove is a pioneer in the semiconductor industryand builder of Intel, the corporation whose processors nowpower the majority of personal computers. Grove was bornAndrás Gróf on September 2, 1936, in Budapest to a Jewishfamily. Grove’s family was disrupted by the German occupationof Hungary later in World War II. Andrew’s father wasconscripted into a work brigade and then into a Hungarianformation of the German army. Andrew and his mother,Maria, had to hide from the Nazi roundup in which manyHungarian Jews were sent to death in concentration camps.Although the family survived and was reunited after thewar, Hungary had come under Soviet control. Andrew, now20, believed his freedom and opportunity would be verylimited, so he and a friend made a dangerous border crossinginto Austria. Grove came to the United States, wherehe lived with his uncle in New York and studied chemicalengineering. He then earned his Ph.D. at the University ofCalifornia at Berkeley and became a researcher at FairchildSemiconductor in 1963 and then assistant director of developmentin 1967. He soon became familiar with the earlywork toward what would become the integrated circuit, keyto the microcomputer revolution that began in the 1970sand wrote a standard textbook (Physics and Technology ofSemiconductor Devices).In 1968, however, he joined colleagues Robert Noyce andGordon Moore in leaving Fairchild and starting a new company,Intel. Grove switched from research to management,becoming Intel’s director of operations. He established amanagement style that featured what he called “constructiveconfrontation”—a vigorous, objective discussion whereopposing views could be aired without fear of reprisal. Critics,however, sometimes characterized the confrontationsas more harsh than constructive.Grove became a formidable competitor. In the late 1970s,it was unclear whether Intel (maker of the 8008, 8080, andsubsequent processors) or Motorola (with its 68000 processor)would dominate the market for microprocessors to runthe new desktop computers. Grove emphasized the trainingand deployment of a large sales force, and by the time theIBM PC debuted in 1982, it and its imitators would all bepowered by Intel chips.During the 1980s, Grove would be challenged to beadaptable when Japanese companies eroded Intel’s share ofthe DRAM (memory) chip market, often “dumping” productbelow their cost. Grove decided to get Intel out of thememory market, even though it meant downsizing the companyuntil the growing microprocessor market made up forthe lost revenues. In 1987, Grove had weathered the stormand become Intel’s CEO. He summarized his experience ofthe rapidly changing market with the slogan “only the paranoidsurvive.”During the 1990s, Intel introduced the popular Pentiumline, having to overcome mathematical flaws in the first versionof the chip and growing competition from AdvancedMicro Devices (AMD) and other companies that made chipscompatible with Intel’s. Grove also had to fight prostatecancer, apparently successfully, and relinquished his CEOtitle in 1998, remaining chairman of the board.Through several books and numerous articles, Grove hashad considerable influence on the management of modernelectronics manufacturing. He has received many industryawards, including the IEEE Engineering Leadership Recognitionaward (1987), and the AEA Medal of Achievementaward (1993). In 1997, he was CEO of the Year (CEO magazine)and Time magazine’s Man of the Year.Further Reading“Andy Grove.” Intel. Available online. URL: http://www.intel.com/pressroom/kits/bios/grove.htm. Accessed August 5, 2007.Grove, Andrew S. High Output Management. 2nd ed. New York:Vintage Books, 1995.———. One-on-One with Andy Grove. New York: Putnam, 1987.———. Only the Paranoid Survive. New York: Currency Doubleday,1996.Tedlow, Richard S. Andrew Grove: The Life and Times of an American.New York: Penguin/Portfolio, 2006.

Hhackers and hackingStarting in the late 1950s, in computer facilities at MIT,Stanford, and other research universities people began toencounter persons who had both unusual programmingskill and an obsession with the inner workings of themachine. While ordinary users viewed the computer simplyas a tool for solving particular problems, this peculiarbreed of programmers reveled in extending the capabilitiesof the system and creating tools such as program editorsthat would make it easier to create even more powerfulprograms. The movement from mainframes that could runonly one program at a time to machines that could simultaneouslyserve many users created a kind of environmentalniche in which these self-described hackers could flourish.Indeed, while administrators sometimes complained thathackers took up too much of the available computer time,they often depended on them to fix the bugs that infestedthe first versions of time-sharing operating systems. Hackersalso tended to work in the wee hours of the night whilenormal users slept.Early hackers had a number of distinctive characteristicsand tended to share a common philosophy, even if itwas not always well articulated:• Computers should be freely accessible, without arbitrarylimits on their use (the “hands-on imperative”).• “Information wants to be free” so that it can reach itsfull potential. Conversely, government or corporateauthorities that want to restrict information accessshould be resisted or circumvented.• The only thing that matters is the quality of the“hack”—the cleverness and utility of the code andwhat it lets computers do that they could not dobefore.• As a corollary to the above, the reputation of a hackerdepends on his (it was nearly always a male) work—not on age, experience, academic attainment, or anythingelse.• Ultimately, programming was a search for truth andbeauty and even a redemptive quality—coupled withthe belief that technology can change the world.Hackers were relatively tolerated by universities andsometimes prized for their skills by computer companiesneeding to develop sophisticated software. However, as thecomputer industry grew, it became more concerned withstaking out, protecting, and exploiting intellectual property.To the hacker, however, intellectual property was abarrier to the unfettered exploration and exploitation of thecomputer. Hackers tended to freely copy and distribute notonly their own work but also commercial systems softwareand utilities.During the late 1970s and 1980s, the microcomputer createda mass consumer software market, and a new generationof hackers struggled to get the most out of machines that hada tiny amount of memory and only rudimentary graphicsand sound capabilities. Some became successful game programmers.At the same time a new term entered the lexicon,software piracy (see software privacy and counterfeiting).Pirate hackers cracked the copy protection on games219

220 handwriting recognitionand other commercial software so the disks could be copiedfreely and exchanged at computer fairs, club meetings,and on illicit bulletin boards (where they were known as“warez”). (See copy protection and intellectual propertyand computing.)The growing use of on-line services and networks in the1980s and 1990s brought new opportunities to exploit computerskills to vandalize systems or steal valuable informationsuch as credit card numbers. The popular media usedthe term hacker indiscriminately to refer to clever programmers,software pirates, and people who stole information orspread viruses across the Internet. The wide availability ofscripts for password cracking, Web site attacks, and viruscreation means that destructive crackers often have littlereal knowledge of computer systems and do not share theattitudes and philosophy of the true hackers who sought toexploit systems rather than destroy them.During the 1980s, a new genre of science fiction calledcyberpunk became popular. It portrayed a fractured, dystopianfuture where elite hackers could “jack into” computers,experiencing cyberspace directly in their mind, asin William Gibson’s Neuromancer and Count Zero. In suchtales the hacker became the high-tech analog of the cowboyor samurai, a virtual gunslinger who fought for high stakeson the newest frontier (see science fiction and computing).Meanwhile, lurid stories about such notorious realworldhackers (see Mitnick, Kevin) brought the dark sideof hacking into popular consciousness.By the turn of the new century, the popular face of hackingwas again changing. Some of the most effective techniquesfor intruding into systems and for stealing sensitiveinformation (see computer crime and identity theft)have always been psychological rather than technical. Whatstarted as one-on-one “social engineering” (such as posingas a computer technician to get a user’s password) hasbeen “industrialized” in the form of e-mails that frighten orentice recipients into supplying credit card or bank information(see spam and phishing and spoofing.) Criminalhackers have also linked up with more-traditional criminalorganizations, creating rings that can efficiently turn stoleninformation into cash.In response to public fears about hackers’ capabilities,federal and local law enforcement agencies have steppedup their efforts to find and prosecute people who crackor vandalize systems or Web sites. Antiterrorism expertsnow worry that well-financed, orchestrated hacker attackscould be used by rogue nations or terrorist groups to paralyzethe American economy and perhaps even disrupt vitalinfrastructure such as power distribution and air trafficcontrol (see counterterrorism and information warfare).In this atmosphere the older, more positive image ofthe hacker seems to be fading—although the free-wheelingcreativity of hacking at its best continues to be manifestedin cooperative software development (see open source).Further Reading2600 magazine. Available online. URL: http://www.2600.com.Accessed February 2, 2008.Erickson, Jon. Hacking: The Art of Exploitation. 2nd ed. San Francisco:No Starch Press, 2007.Gibson, William. Neuromancer. West Bloomfield, Mich.: PhantasiaPress, 1986.Hafner, Katie, John Markoff. Cyberpunk: Outlaws and Hackers onthe Computer Frontier. New York: Simon & Schuster, 1991.Harris, Shon, et al. Gray Hat Hacking: The Ethical Hacker’s Handbook.Berkeley, Calif.: McGraw-Hill/Osborne Media, 2004.Levy, Stephen. Hackers: Heroes of the Computer Revolution. NewYork: Doubleday, 1984.Littman, J. The Fugitive Game: On-line with Kevin Mitnick. Boston:Little, Brown, 1996.Mitnick, Kevin, and William L. Simon. The Art of Deception: Controllingthe Human Element of Security. Indianapolis: Wiley,2002.———. The Art of Intrusion: The Real Stories behind the Exploits ofHackers, Intruders & Deceivers. Indianapolis: Wiley, 2005.Raymond, Eric. The New Hacker’s Dictionary. 3rd ed. Cambridge,Mass.: MIT Press, 1996.handwriting recognitionWhile the keyboard is the traditional means for enteringtext into a computer system, both designers and users havelong acknowledged the potential benefits of a system wherepeople could enter text using ordinary script or printedhandwriting and have it converted to standard computercharacter codes (see characters and strings). With sucha system people would not need to master a typewriter-stylekeyboard. Further, users could write commands or takenotes on handheld or “palm” computers the size of a smallnote pad that are too small to have a keyboard (see portablecomputers). Indeed, such facilities are available to alimited extent today.A handwriting recognition system begins by buildinga representation of the user’s writing. With a pen or stylussystem, this representation is not simply a graphical imagebut includes the recorded “strokes” or discrete movementsthat make up the letters. The software must then create arepresentation of features of the handwriting that can beused to match it to the appropriate character templates.Handwriting recognition is actually an application of thelarger problem of identifying the significance of features ina pattern.One approach (often used on systems that work frompreviously written documents rather than stylus strokes)is to identify patterns of pixels that have a high statisticalcorrelation to the presence of a particular letter in the rectangular“frame” under consideration. Another approach isto try to identify groups of strokes or segments that can beassociated with particular letters. In evaluating such tentativerecognitions, programs can also incorporate a networkof “recognizers” that receive feedback on the basis of theiraccuracy (see neural network). Finally, where the identityof a letter remains ambiguous, lexical analysis can be usedto determine the most probable letter in a given context,using a dictionary or a table of letter group frequencies.Implementation and ApplicationsA number of handheld computers beginning with Apple’sNewton in the mid-1990s and the now popular Palm devicesand BlackBerry have some ability to recognize handwriting.However, current systems can be frustrating to use

haptic interfaces 221Currently, handwriting recognition is used mainly inniche applications, such as collecting signatures for deliveryservices or filling out “electronic forms” in applicationswhere the user must be mobile and relatively hands-free(such as law enforcement).Further ReadingCrooks, Clayton E. II. Developing Tablet PC Applications. Hingam,Mass.: Charles River Media, 2003.“Handwriting Recognition.” TechRepublic Resources. Availableonline. URL: http://search.techrepublic.com.com/search/handwriting+recognition.html. Accessed August 6, 2007.Liu, Zhi-Qiang, Jin-Hai Cai, and Richard Buse. Handwriting Recognition:Soft Computing and Probabilistic Approaches. New York:Springer, 2003.Matthews, Craig Forrest. Absolute Beginner’s Guide to Tablet PCs.Indianapolis: Que, 2003.Taylor, Paul. “Cast Off Your Keyboard.” Financial Times/FT.comAugust 2, 2007. Available online. URL: http://www.ft.com/cms/s/04546598-410d-11dc-8f37-0000779fd2ac.html.Accessed August 6, 2007.Van West, Jeff. “Using Tablet PC: Handwriting Recognition 101.”Available online. URL: http://www.microsoft.com/windowsxp/using/tabletpc/getstarted/vanwest_03may28hanrec.mspx.Accessed August 6, 2007.Zimmerman, W. Frederick. Complete Guide to OneNote. Berkeley,Calif.: Apress, 2003.One approach to handwriting recognition involves the extraction ofa stroke pattern and its comparison to a database of templates representingvarious letters and symbols. Ultimately the correspondingASCII character is determined and stored.because accuracy often requires that users write very carefullyand consistently or (as in the case of the Palm) evenreplace their usual letter strokes with simplified alternativesthat the computer can more easily recognize. If the user isallowed to use normal strokes, the system must be gradually“trained” by the user giving writing samples and confirmingthe system’s guess about the letters. As the softwarebecomes more adaptable and processing power increases(allowing more sophisticated algorithms or larger neuralnetworks to be practical) users will be able to write morenaturally and systems will gain more consumer acceptance.(One step in this direction is the Tablet PC, a notepad-sizedcomputer with a digitizer tablet and a stylus and handwritingrecognitions software, included in Windows XP andexpanded in Windows Vista. Programs such as MicrosoftOneNote use handwriting recognition to allow users toincorporate handwritten text into notes that can be organizedand quickly retrieved.)haptic interfacesMost interfaces between users and computer systems involvethe equivalent of switches—keyboard keys or mouse buttons.These interfaces cannot respond to degrees of pressure(for an exception, see graphics tablet). Further, thereis no feedback returned to the user through the interfacedevice—the key or mouse does not “push back.”Haptic (from the Greek word for “touch”) interfaces aredifferent in that they do register the pressure and motion oftouch, and they often provide touch feedback as well.Force-feedback systems use movement of the controlas a way to provide feedback to the operator. A commonexample is the control stick in an aircraft that begins tovibrate as the aircraft approaches a stall (where it wouldlose control). This provides immediate feedback to the pilotusing the device by which he or she is already controllingthe plane.More sophisticated forms of force feedback are used inremote-controlled devices for manipulation or exploration.The first application was developed in the 1950s for handlingradioactive materials. Today a combination of positionand movement sensing and force feedback can be usedwith special gloves to enable users to grasp and heft 3Dvirtual objects while getting a sense of their weight, shape,and even texture.In games, haptic joysticks and other controls such assteering wheels can provide sensations such as resistance toa car’s turn or the sensation of a bat hitting a ball. The NintendoWii game console comes with a controller that tracksthe direction and speed of its movement along with a set ofsimple but engrossing sports games to show its capabilities.Some emerging or near-future uses of haptic technologyinclude:

222 hard disk• remote surgery, where the surgeon can feel the resistanceof tissues and the location of anatomical features• use of haptic technology to provide robots with morehumanlike gripping capabilities• 3D sculpture in a virtual 3D world modeling the characteristicsof different materials and toolsLike virtual reality itself, haptics is currently foundin niche applications such as entertainment, control, andtraining systems. Besides the expense of the technologyitself, there is the need for specialized programming. However,the time may come when haptic support, like mouseand pen support, is included in operating systems andwidely available programming libraries.Further ReadingBurdea, Grigore C. Force and Touch Feedback for Virtual Reality.New York: Wiley, 2006.Haptic Interface Research Laboratory (Purdue University).Available online. URL: http://www.ecn.purdue.edu/HIRL/.Accessed September 23, 2007.McLaughlin, Margaret L., Joao P. Hespanha, and Gaurav S.Sukhatme. Touch in Virtual Environments: Haptics and theDesign of Interactive Systems. Upper Saddle River, N.J.: PrenticeHall, 2002.Zyga, Lisa. “Artists ‘Draw on Air’ to Create 3D Illustrations.” Availableonline. URL: http://www.physorg.com/news109425896.html. Accessed September 23, 2007.hard diskEven after decades of evolution in computing, the harddisk drive remains the primary means of fast data storageand retrieval in computer systems of all sizes. The diskitself consists of a rigid aluminum alloy platter coated witha magnetic oxide material. The platter can be rotated atspeeds of more than 10,000 rpm. A typical drive consists ofa stack of such platters mounted on a rotating spindle, witha read/write head mounted above each platter.Early hard drive heads were controlled by a steppermotor, which positioned the head in response to a series ofelectrical pulses. (This system is still used for floppy drives.)Today’s hard drives, however, are controlled by a voice-coilactuator, similar in structure to an audio speaker. The coilsurrounds a magnet. When a current enters the coil, it generatesa magnetic field that interacts with that of the permanentmagnet, moving the coil and thus the disk head. Unlikethe stepper motor, the voice coil is continuously variable andits greater precision allows data tracks to be packed moretightly on the platter surface, increasing disk capacity.The storage capacity of a drive is determined by thenumber of platters and the spacing (and thus number) oftracks that can be laid down on each platter. Capacitieshave steadily increased while prices have plummeted: In1980, for example, a hard drive for an Apple II microcomputercost more than $1,000 and held only 5 MB of data. Asof 2007 internal hard drives with a capacity of 500 GB ormore cost around a $150.00.Data is organized on the disk by dividing the tracksinto segments called sectors. When the disk is preparedParts of a typical hard disk drive. Many hard drives have multipleheads and platters to allow for storage of larger amounts of data.to receive data (a process called formatting), each sectoris tested by writing and reading sample data. If an erroroccurs, the operating system marks the sector as unusable(virtually any hard disk will have at least a few such badsectors).The set of vertical corresponding tracks on the stack ofplatters that make up the drive is called a cylinder. Sincethe drive heads are connected vertically, if a head is currentlyreading or writing for example sector 89 on oneplatter, it is positioned over that same sector on all theothers. Therefore, the operating system normally storesfiles by filling the full cylinder before going to a new sectornumber.Another way to improve data flow is to use sector interleaving.Because many disk drives can read data faster thanthe operating system can read it from the disk’s memorybuffer, data is often stored by skipping over adjacent sectors.Thus, instead of storing a file on sectors 1, 2, and 3,it might be stored on sectors 1, 3, and 5 (this is called a 2:1interleave). Moving the head from sector 1 to sector 3 givesthe system enough time to process the data. (Otherwise,by the time the system was ready to read sector 2, the diskwould have rotated past it and the system would have towait through a complete rotation of the disk.) Newer CPUsare often fast enough to keep up with contiguous sectors,avoiding the need for interleaving.Data throughput tends to decrease as a hard drive isused. This is due to fragmentation. The operating systemruns out of sufficient contiguous space to store new filesand has to write new files to many sectors widely scatteredon the disk. This means the head has to be moved moreoften, slowing data access. Using an operating system (or

hashing 223third party) defragmentation utility, users can periodicallyreorganize their hard drive so that files are again stored incontiguous sectors.Files can also be reorganized to optimize space ratherthan access time. If an operating system has a minimumcluster size c4K, a single file with only 32 bytes of datawill still consume 4,096 bytes. However, if all the files arewritten together as one huge file (with an index that specifieswhere each file begins) that waste of space would beavoided. This is the principle of disk compression. Diskcompression does slow access somewhat (due to the needto look up and position to the actual data location for afile) and the system becomes more fragile (since garblingthe giant file would prevent access to the data in perhapsthousands of originally separate files). The low cost ofhigh capacity drives today has made compression lessnecessary.Interfacing Hard DrivesWhen the operating system wants to read or write datato the disk, it must send commands to the driver, a programthat translates high-level commands to the instructionsneeded to operate the disk controller, which in turnoperates the motors controlling the disk heads. The twomost commonly used interfaces for PC internal hard drivestoday are both based on the ATA (Advanced TechnologyAttachment) standard. The older standard is PATA (parallelATA), also called IDE (Integrated Drive Electronics)or EIDE (Enhanced IDE). Increasingly common today isSATA, or serial ATA. Another alternative, more commonlyused on servers, is SCSI (Small Computer System Interface).SCSI is more expensive but has several advantages: It hasthe ability to organize incoming commands for greater efficiencyand also features greater flexibility (an EIDE controllercan connect only two hard drives, while SCSI can “daisychain” a large number of disk drives or other peripherals).In practice, the two interfaces perform about equally well.USB (Universal Serial Bus) is frequently used to interfacewith external hard drive units (see usb).The capacity continues to increase, with data able tobe written more densely or perhaps in multiple layers onthe same disk surface. Denser storage also offers the abilityto make drives more compact. Already hard drives with adiameter of about an inch have been built by IBM and othersfor use in digital cameras.The proliferation of multimedia (including video) andthe growth of databases has fed a voracious appetite forhard drive space. Disks with a capacity of 1 TB (terabyte,or trillion bytes) were starting to come onto the market by2007. For larger installations, disk arrays (see raid) offerhigh capacity and data-protecting redundancy.Perpendicular hard drive recording technology recentlydeveloped by Hitachi aligns the magnetic “grains” that holdbits of data vertically instead of horizontally, allowing fora considerably higher data density (and thus capacity, for agiven size disk). Hitachi suggests that eventually 1 TB canbe stored on a 3.5" disk.Drive speeds (and thus data throughput) have also beenincreasing, with more users choosing 7200 rpm rather thanthe formerly standard 5400 rpm drives. (There are drives asfast as 15,000 rpm, but for most applications the benefits ofhigher speed drop off rapidly.)Another factor in data access time and throughput is theuse of a dedicated memory device (see cache) to “pre-fetch”data likely to be needed. Windows Vista allows memoryfrom some USB memory sticks (see flash drive) to workas a disk cache. “Hybrid” hard drives directly integratingRAM and drive storage are also available.Further ReadingJacob, Bruce, Spencer Ng, and David Wang. Memory Systems:Cache, DRAM, Disk. San Francisco: Morgan Kaufmann, 2007.“Perpendicular Hard Drive Recording Technology.” Available online.URL: http://www.webopedia.com/DidYouKnow/Computer_Science/2006/perpendicular_hard_drive_technology.asp.Accessed August 6, 2007.“Storage.” Tom’s Hardware Guide. Available online. URL: http://www.tomshardware.com/storage/index.html. Accessed August 6,2007.“What’s Inside a Hard Drive?” Available online. URL: http://www.webopedia.com/DidYouKnow/Hardware_Software/2002/InsideHardDrive.aspdYouKnow/Hardware_Software/2002/InsideHardDrive.asp. Accessed August 6, 2007.hashingA hash is a numeric value generated by applying a mathematicalformula to the numeric values of the charactersin a string of text (see characters and strings). The formulais chosen so that the values it produces are always thesame length (regardless of the length of the original text)and are very likely to be unique. (Two different stringsshould not produce the same hash value. Such an event iscalled a collision.)ApplicationsThe two major application areas for hashing are informationretrieval and cryptographic certification. In databases,an index table can be built that contains the hash values forthe key fields and the corresponding record number for eachfield, with the entries in hash value order. To search thedatabase, an input key is hashed and the value is comparedwith the index table (which can be done using a very fastbinary search). If the hash value is found, the correspondingrecord number is used to look up the record. This tends tobe much faster than searching an index file directly.Alternatively, a “coarser” but faster hashing function canbe used that will give the same hash value to small groups(called bins) of similar records. In this case the hash fromthe search key is matched to a bin and then the recordswithin the bin are searched for an exact match.In cryptography an encrypted message can be hashed,producing a unique fixed-length value. (The fixed lengthprevents attackers from using mathematical relationshipsthat might be discoverable from the field lengths.) Thehashed message can then be encrypted again to create anelectronic signature (see certificate, digital). For longmessages this is more efficient than having to apply the signaturefunction to each block of the encrypted message, yet

224 health, personalTo search a hashed database, the hashing formula is first applied tothe search key, yielding a hash value. That value can then be usedin a binary search to quickly zero in on the matching record, if any.the unique relationship between the original message andthe hash maintains a high degree of security.Finally, hashing can be used for error detection. If amessage and its hash are sent together, the recipient canhash the received text. If the hash value generated matchesthe one received, it is highly likely the message was receivedintact (see also error correction).Further ReadingPartow, Arash. “General Purpose Hash Function Algorithms.”Available online. URL: http://www.partow.net/programming/hashfunctions/. Accessed August 6, 2007.Pieprzyk, Josef, and Babak Sadeghiyan. Design of Hashing Algorithms.New York: Springer-Verlag, 1993.health, personal See personal health informationmanagement.heapIn operating systems and certain programming languages(such as LISP), a heap is a pool of memory resources availablefor allocation by programs. The memory segments(sometimes called cells) can be the same size or of variablesize. If the same size, they are linked together by pointers(see list processing). Memory is then allocated for a variableby traversing the list and setting the required numberof cells to be “owned” by that variable. (While some languagessuch as Pascal and C use explicit memory allocationor deallocation functions, other languages such as LISP usea separate runtime module that is not the responsibility ofthe programmer.)Deallocation (the freeing up of memory no longerneeded by a variable so it can be used elsewhere) is morecomplicated. In many languages several different pointerscan be used to refer to the same memory location. It istherefore necessary not only to disconnect a given pointerfrom the cell, but to track the total number of pointers connectedto the cell so that the cell itself is deallocated onlywhen the last pointer to it has been disconnected. Oneway to accomplish this is by setting up an internal variablecalled a reference counter and incrementing or decrementingit as pointers are connected or disconnected. The disadvantagesof this approach include the memory overhead neededto store the counters and the execution overhead of havingto continually check and update the counters.An alternative approach is garbage collection. Here theruntime system simply connects or disconnects pointersas required by the program’s declarations, without makingan attempt to reclaim the disconnected (“dead”) cells. Ifand when the supply of free cells is exhausted, the runtimesystem takes over and begins a three-stage process. First,it provisionally sets the status indicator bit for each cell toshow that it is “garbage.” Each pointer in the program isthen traced (that is, its links are followed) into the heap,and if a valid cell is found that cell’s indicator is reset to“not garbage.” Finally, the garbage cells that remain arelinked back to the pool of free cells available for future allocation.The chief drawback of garbage collection is that themore cells actually being used by the program, the longerthe garbage-collecting process will take (since all of thesecells have to be traced and verified). Yet it is precisely whenmost cells are in use that garbage collection is most likely tobe required.The need for garbage collection has diminished in manyprogramming environments because modern computersnot only have large amounts of memory, most operatingsystems also implement virtual memory, which allows adisk or other storage device to be treated as an extension ofmain memory.Note: the term heap is also used to describe a particulartype of binary tree. (See tree.)Further ReadingLafore, Robert. Data Structures & Algorithms in Java. 2nd ed. Indianapolis:Sams, 2002.Preiss, Bruno R. “Heaps and Priority Queues.” Available online.URL: http://www.brpreiss.com/books/opus4/html/page352.html. Accessed August 6, 2007.Sebesta, Robert W. Concepts of Programming Languages. 8th ed.Boston: Addison-Wesley, 2007.help systemsIn the early days of computing, the programmers of a systemtended to also be its users and were thus intimatelyfamiliar with the program’s operation and command set.

hexadecimal system 225If not a programmer, the user of a mainframe program wasprobably at least a well-trained operator who could workwith the aid of a brief summary or notes provided by theprogrammer. However, with the beginnings of office automationin the 1970s and the growing use of desktop computersin office, home, and school in the 1980s, increasinglycomplex programs were being put in the hands of userswho often had only minimal computer training (see computerliteracy).While programs often came with one or more tutorialor reference manuals, designers realized that offering helpthrough the program itself would have some clear advantages.First, the user would not have to switch attention fromthe computer screen to look things up in a manual. Second,the help system could be programmed to not only provideinformation, but also to help the user find the informationneeded in a given situation. For example, related topicscould be linked together and a searchable index provided.ImplementationPrograms running under the text-based MS-DOS of the1980s tended to have only rudimentary help screens (ofteninvoked by pressing the F1 key). Generally, these were limitedto brief summaries of commands and associated keycombinations. However, with the growing use of MicrosoftWindows (and the similar Macintosh interface), a morecomplete and versatile help system was possible. Since thesesystems allowed multiple windows to be displayed on thescreen, the user could consult help information while stillseeing the program’s main screen. This allowed for trying arecommended procedure and observing the results.Windows and Macintosh help systems also featuredhighlighted links in the text that could be used to jump torelated topics (see hypertext and hypermedia). A topicword can also be typed into an index box, bringing up anymatching topics. If all else fails, the entire help file could beindexed so that any word could be used to find matchingtopics.More recent Windows programs also include wizards. Awizard is a step-by-step procedure for accomplishing a particulartask. For example, if a Microsoft Word user want tolearn how to format text into multiple columns, the help systemcan offer a wizard that takes the user through the procedureof specifying the number of columns, column size, andso on. The steps can even be applied directly to the documentwith the wizard “driving” the program accordingly.Recently, many programs have implemented their helpin the form of Web pages, stored either on the user’s computeror at the vendor’s Web site (see html). HTML has theadvantage that it is now a nearly universal format that canbe used on a variety of platforms and (if hosted on a Website) the help can be continually improved and updated.(Microsoft’s latest version of HTML Help has supplanted itsoriginal WinHelp, which is no longer supported by Vista.)A variety of shareware and commercial help authoringsystems such as RoboHelp are available to help developerscreate help in Windows or HTML format. UNIX systems,which have always included an on-line manual, now typicallyoffer HTML-based help as well.With printed documentation being increasinglyeschewed for cost-cutting reasons, users of many programstoday must depend on the help system as well as on on-linedocuments (such as PDF files) and Web-based support.Further ReadingHackos, JoAnn T., and Dawn M. Steven. Standards for Online Communication:Publishing Information for the Internet/World WideWeb/Help Systems/Corporate Intranets. New York: Wiley, 1997.Heng, Christopher. “Free Help Authoring, Manual and DocumentationWriting Tools.” Available online. URL: http://www.thefreecountry.com/programming/helpauthoring.shtml.Accessed August 6, 2007.“Microsoft HTML Help 1.4 SDK.” Available online. URL: http://msdn2.microsoft.com/en-us/library/ms670169.aspx. AccessedAugust 6, 2007.Weber, Jean Hollis. Is the Help Helpful? How to Create Online HelpThat Meets Your Users’ Needs. Whitefish Bay, Wisc.: HentzenwerkePublishing, 2004.hexadecimal systemThe base 16 or hexadecimal system is a natural way to representthe binary data stored in a computer. It is more compactthan binary because four binary digits can be replacedby a single “hex” digit.The following table gives the corresponding decimal,binary, and hex values from 0 to 15:Decimal Binary Hex0 0 01 0001 12 0010 23 0011 34 0100 45 0101 56 0110 67 0111 78 1000 89 1001 910 1010 A11 1011 B12 1100 C13 1101 D14 1110 E15 1111 FNote that decimal and hex digits are the same from 0 to9, but hex uses the letters A–F to represent the digits correspondingto decimal 10–15. The system extends to highernumbers using increasing powers of 16, just as decimaluses powers of 10: For example, hex FF represents binary11111111 or decimal 255. Many of the apparently arbitrarynumbers encountered in programming can be better understoodif one realizes that they correspond to convenientgroupings of bits: FF is eight bits, sufficient to hold a singlecharacter (see characters and strings). In low-level programmingmemory addresses are also usually given in hex(see assembler).

226 history of computingFurther ReadingMatz, Kevin. “Introduction to Binary and Hexadecimal.” Availableonline. URL: http://www.comprenica.com/atrevida/atrtut01.html. Accessed August 7, 2007.history of computingWith the digital computer now more than 60 years old, therehas been growing interest in its history and development.Although it would take a library of books to do the subjectjustice, providing a summary of the main themes and trendsof each decade of computing will give readers of this booksome helpful context for understanding the other entries.Early HistoryIn a sense, the idea of mechanical computation emerged inprehistory when early humans discovered that they coulduse physical objects such as piles of stones, notches, ormarks as a counting aid. The ability to perform computationbeyond simple counting extends back to the ancientworld: For example, the abacus developed in ancient Chinacould still beat the best mechanical calculators as late asthe 1940s (see calculator). The mechanical calculatorbegan in the West in the 17th century, most notably withthe machines created by philosopher-scientist Blaise Pascal.Other devices such as “Napier’s bones” (ancestor of theslide rule) depended on proportional logarithmic relationships(see analog computer).While the distinction between a calculator and true computeris subtle, Charles Babbage’s work in the 1830s delineatedthe key concepts. His “analytical engine,” conceived butnever built, would have incorporated punched cards for datainput (an idea taken over from the weaving industry), a centralcalculating mechanism (the “mill”), a memory (“store”),and an output device (printer). The ability to input both programinstructions and data would enable such a device tosolve a wide variety of problems (see Babbage, Charles).Babbage’s thought represented the logical extension ofthe worldview of the industrial revolution to the problemof calculation. The computer was a “loom” that wove mathematicalpatterns. While Babbage’s advanced ideas becamelargely dormant after his death, the importance of statisticsand information management would continue to grow withthe development of the modern industrial state in Europeand the United States throughout the 19th century. Thepunch card as data store and the creation of automatic tabulationsystems would reemerge near the end of the century(see Hollerith, Herman).During the early 20th century, mechanical calculators andcard tabulation and sorting machines made up the data processingsystems for business, while researchers built specialpurposeanalog computers for exploring problems in physics,electronics, and engineering. By the late 1930s, the idea of aprogrammable digital computer emerged in the work of theoreticians(see Turing, Alan and von Neumann, John).1940sThe highly industrialized warfare of World War II requiredthe rapid production of a large volume of accurate calculationsfor such applications as aircraft design, gunnery control,and cryptography. Fortunately, the field was now ripefor the development of programmable digital computers.Many reliable components were available to the computerdesigner including switches and relays from the telephoneindustry and card readers and punches (manufactured byHollerith’s descendant, IBM), and vacuum tubes used inradio and other electronics.Early computing machines included the Mark I (seeAiken, Howard), a huge calculator driven by electricalrelays and controlled by punched paper tape. Anothermachine, the prewar Atanasoff-Berry Computer (seeAtanasoff, John) was never completed, but demonstratedthe use of electronic (vacuum tube) components, whichwere much faster than electromechanical relays. Meanwhile,a German inventor built a programmable binary computerthat combined a mechanical number storage mechanismwith telephone relays (see Zuse, Conrad). Zuse also proposedbuilding an electronic (vacuum tube) computer, butthe German government decided not to support the project.During the war, British and American code breakersbuilt a specialized electronic computer called Colossus,which read encoded transmissions from tape and brokethe code of the supposedly impregnable German Enigmamachines.The most viable general-purpose computers were developedby J. Presper Eckert and John Mauchly starting in1943 (see Eckert, J. Presper and Mauchly, John). Thefirst, ENIAC, was completed in 1946 and had been intendedto perform ballistic calculations. While its programmingfacilities were primitive (programs had to be set up via aplugboard), ENIAC could perform 5,000 arithmetic operationsper second, about a thousand times faster than theJohn Mauchly and Presper Eckert, Jr., shown with a portion of theirENIAC computer. The ENIAC is often considered to be the firstgeneral-purpose electronic digital computer. (Hulton Archive /Getty Images)

history of computing 227electromechanical Mark I. ENIAC had about 19,000 vacuumtubes and consumed as much power as perhaps a thousandmodern desktop PCs.1950sThe 1950s saw the establishment of a small but viable commercialcomputer industry in the United States and parts ofEurope. Eckert and Mauchly formed a company to designand market the UNIVAC, based partly on work on the experimentalEDVAC. This new generation of computers wouldincorporate the key concept of the stored program: Ratherthan the program being set up by wiring or simply readsequentially from tape or cards, the program instructionswould be stored in memory just like any other data. Besidesallowing a computer to fetch instructions at electronic ratherthan mechanical speeds, storing programs in memory meantthat one part of a program could refer to another part duringoperation, allowing for such mechanisms as branching,looping, the running of subroutines, and even the ability ofa program to modify its own instructions.The UNIVAC became a hit with the public when it wasused to correctly predict the outcome of the 1952 presidentialelection. Government offices and large corporationsbegan to look toward the computer as a way to solve theirincreasingly complex data processing needs. Forty UNI-VACs were eventually built and sold to such customers asthe U.S. Census Bureau, the U.S. Army and Air Force, andinsurance companies. Sperry (having bought the Mauchly-Eckert company), Bendix, and other companies had somesuccess in selling computers (often for specialized applications),but it was IBM that eventually captured the broadbusiness market for mainframe computers.The IBM 701 (marketed to the government and defenseindustry) and 702 (for the business market) incorporated severalemerging technologies including a fast electronic (tube)memory that could store 4,096 36-bit data words, a rotatingmagnetic drum that could store data that is not immediatelyneeded, and magnetic tape for backup. The IBM 650, marketedstarting in 1954, became the (relatively) inexpensiveworkhorse computer for businesses (see mainframe). TheIBM 704, introduced in 1955, incorporated magnetic corememory and also featured floating-point calculations.1960sThe 1960s saw the advent of a “solid state” computer designfeaturing transistors in place of vacuum tubes and the useof ferrite magnetic core memory (introduced commerciallyin 1955). These innovations made computers both morecompact (although they were still large by modern standards),more reliable, and less expensive to operate (dueto lower power consumption.) The IBM 1401 was a typicalexample of this new technology: It was compact, relativelysimple to operate, and came with a fast printer that made iteasier to generate data.There was a natural tendency to increase the capacityof computers by adding more transistors, but the handwiringof thousands of individual transistors was difficultand expensive. As the decade progressed, however, the conceptof the integrated circuit began to be implemented incomputing. The first step in that direction was to attach anumber of transistors and other components to a ceramicsubstrate, creating modules that could be handled andwired more easily during the assembly process.IBM applied this technology to create what wouldbecome one of the most versatile and successful lines inthe history of computing, the IBM System/360 computer.This was actually a series of 14 models that offered successivelygreater memory capacity and processing speedwhile maintaining compatibility so that programs developedon a smaller, cheaper model would also run on themore expensive machines. Compatibility was ensured bydevising a single 360 instruction set that was implementedat the machine level by microcode stored in ROM (read-onlymemory) and optimized for each model. By 1970 IBM hadsold more than 18,000 360 systems worldwide.By the mid-1960s, however, a new market segment hadcome into being: the minicomputer. Pioneered by DigitalEquipment Corporation (DEC) with its PDP line, the minicomputerwas made possible by rugged, compact solid-state(and increasingly integrated) circuits. Architecturally, themini usually had a shorter data word length than the mainframe,and used indirect addressing (see addressing) forflexibility in accessing memory. Minis were practical for usesin offices and research labs that could not afford (or house)a mainframe (see minicomputer). They were also a boonto the emerging use of computers in automating manufacturing,data collection, and other activities, because a minicould fit into a rack with other equipment (see also embeddedsystems). In addition to DEC, Control Data Corporation(CDC) produced both minis and large high-performancemachines (the Cyber series), the first truly commerciallyviable supercomputers (see supercomputer).In programming, the main innovation of the 1960s wasthe promulgation of the first widely-used, high-level programminglanguages, COBOL (for business) and FORTRAN(for scientific and engineering calculations), the result ofresearch in the late 1950s. While some progress had beenmade earlier in the decade in using symbolic names forquantities and memory locations (see assembler), the newhigher-level languages made it easier for professionals outsidethe computer field to learn to program and made theprograms themselves more readable, and thus easier tomaintain. The invention of the compiler (a program thatcould read other programs and translate them into lowlevelmachine instructions) was yet another fruit of thestored program concept.1970sThe 1970s saw minis becoming more powerful and versatile.The DEC VAX (“Virtual Address Extension”) series allowedlarger amounts of memory to be addressed and increasedflexibility. Meanwhile, at the high end, Seymour Cray leftCDC to form Cray Research, a company that would producethe world’s fastest supercomputer, the compact, freoncooledCray-1. In the mainframe mainstream, IBM’s 370series maintained that company’s dominant market share inbusiness computing.

228 history of computingThe most striking innovation of the decade, however,was the microcomputer. The microcomputer (now oftencalled the “computer chip”) combined three basic ideas: anintegrated circuit so compact that it could be laid on a singlesilicon chip, the design of that circuit to perform the essentialaddressing and arithmetic functions required for a computer,and the use of microcode to embody the fundamentalinstructions. Intel’s 4004 introduced in late 1971 was originallydesigned to sell to a calculator company. When thatdeal fell through, Intel started distributing the microprocessorsin developer’s kits to encourage innovators to designcomputers around them. Soon Intel’s upgraded 8008 and8080 microprocessors were available, along with offeringsby Rockwell, Texas Instruments, and other companies.Word of the microprocessor spread through the electronichobbyist community, being given a boost by theJanuary 1975 issue of Popular Electronics that featured theAltair computer kit, available from an Albuquerque companycalled MITS for about $400. Designed around the Intel8080, the Altair featured an expansion bus (an idea borrowedfrom minis).The Altair was hard to build and had very limited memory,but it was soon joined by companies that designedand marketed ready-to-use microcomputer systems, whichsoon became known as personal computers (PCs). By 1980,entries in the field included Apple (Apple II), Commodore(Pet), and Radio Shack (TRS-80). These computers sharedcertain common features: a microprocessor, memory in theform of plug-in chips, read-only memory chips containinga rudimentary operating system and a version of the BASIClanguage, and an expansion bus to which users could connectperipherals such as disk drives or printers.The spread of microcomputing was considerably aidedby the emergence of a technical culture where hobbyistsIntegrated circuit (IC) chips for memory and control were makingfor increasingly powerful, compact, and reliable computer components.The microprocessor supplied the remaining ingredient neededfor a true desktop personal computer.and early adopters wrote and shared software, snatchedup a variety of specialized magazines, talked computers inuser groups, and evangelized for the cause of widespreadpersonal computing.Meanwhile, programming and the art of softwaredevelopment did not stand still. Innovations of the 1970sincluded the philosophy of structured programming (featuringwell-defined control structures and methods forpassing data to and from subroutines and procedures). Newlanguages such as Pascal and C, building on the earlierAlgol, supported structured programming design to varyingdegrees (see structured programming). Programmers oncollege campuses also had access to UNIX, a powerful operatingsystem containing a relatively simple kernel, a shellfor interaction with users, and a growing variety of utilityprograms that could be connected together to solve dataprocessing problems (see unix). It was in this environmentthat the government-funded ARPANET developed protocolsfor communicating between computers and allowingremote operation of programs. Along with this came e-mail,the sharing of information in newsgroups (Usenet), and agrowing web of links between networks that would eventuallybecome the Internet (see internet).1980sIn the 1980s, the personal computer came of age. IBM brokefrom its methodical corporate culture and allowed a designteam to come up with a PC that featured an open, expandablearchitecture. Other companies such as Compaq legallycreated compatible systems (called “clones”), and “PC-compatible”machines became the industry standard. Under theleadership of Bill Gates, Microsoft gained control of theoperating system market and also became the dominantcompetitor in applications software (particularly office softwaresuites).Although unable to gain market share comparable to thePC and its clones, Apple’s innovative Macintosh, introducedin 1984, adapted research from the Xerox PARC laboratoryin user interface design. At a time when PC compatibleswere still using Microsoft’s text-based MS-DOS, the Macsported a graphical user interface featuring icons, menus,and buttons, controlled by a mouse (see user interface).Microsoft responded by developing the broadly similarWindows operating environment, which started out slowlybut had become competitive with Apple’s by the end of thedecade.The 1980s also saw great growth in networking. Universitycomputers running UNIX were increasingly linkedthrough what was becoming the Internet, while office computersincreasingly used local area networks (LANs) suchas those based on Novell’s Netware system. Meanwhile, PCswere also being equipped with modems, enabling users todial up a growing number of on-line services ranging fromgiants such as CompuServe to a diversity of individuallyrun bulletin board systems (see bulletin board systems).In the programming field a new paradigm, object-orientedprogramming (OOP) was offered by languages suchas smalltalk and C++, a variant of the popular C language.The new style of programming focused on programs as

Hollerith, Herman 229embodying relationships between objects that are responsiblefor both private data and a public interface representedby methods, or capabilities offered to users of the object.Both structured and object-oriented methods attempted tokeep up with the growing complexity of large software systemsthat might incorporate millions of lines of code. Thefederal government adopted the Ada language with its abilityto precisely manage program structure and data operations.(See object-oriented programming and ada.)1990sBy the 1990s, the PC was a mature technology dominatedby Microsoft’s Windows operating system. UNIX, too, hadmatured and become the system of choice for university computingand the worldwide Internet. Although the potential ofthe Internet for education and commerce was beginning tobe explored, at the beginning of the decade the network wasfar from friendly for the average consumer user.This changed when Tim Berners-Lee, a researcher atGeneva’s CERN physics lab, adapted hypertext (a way tolink documents together) with the Internet protocol toimplement the World Wide Web. By 1994, Web browsingsoftware that could display graphics and play sounds wasavailable for Windows-based and other computers (seeWorld Wide Web and Web browser). The remainder ofthe decade became a frenzied rush to identify and exploitbusiness plans based on e-commerce, the buying and sellingof goods and services on-line (see e-commerce). Meanwhile,educators demanded Internet access for schools.In the office, the Intranet (a LAN based on the InternetTCP/IP protocol) began to supplant earlier networkingschemes. Belatedly recognizing the threat and potentialposed by the Internet, Bill Gates plunged Microsoft intothe Web server market, included the free Internet Explorerbrowser with Windows, and vowed that all Microsoft programswould work seamlessly with the Internet.Moore’s Law, the dictum that computer power roughlydoubles every 18 months, continued to hold true as PCswent from clock rates of a few tens of MHz to more than 1GHz. RAM and hard disk capacity kept pace, while low-costcolor printers, scanners, digital cameras, and video systemsmade it easier than ever to bring rich media content intothe PC and the on-line world.Beyond 2000The new decade began with great hopes, particularly for theWeb and multimedia “dot-coms,” but their stocks, inflatedby unsustainable expectations, took a significant dip in2000–2001. By the middle of the decade the computingindustry had largely recovered and in many ways was strongerthan ever. On the Web, new software approaches (seeAjax, application service provider, and service-orientedarchitecture) are changing the way services andeven applications are delivered. The integration of searchengines, mapping, local content, and user participation (seeblogging, user-created content, and social networking)is changing the relationship between companies andtheir customers.In hardware, Moore’s law is now expressed not throughfaster single processors, but using processors with two, four,or more processing “cores,” challenging software designers(see multiprocessing). Mobile computing is one of thestrongest areas of growth (see pda and smartphone), withdevices combining voice phone, text messaging, e-mail, andWeb browsing.)The industry continues to face formidable challengesranging from mitigating environmental impact (see greenpc) to the shifting of manufacturing and even softwaredevelopment to rapidly growing countries such as Indiaand China (see globalism and the computer industry.)Thus far, each decade has brought new technologies andmethods to the fore, and few observers doubt that this willbe true in the future.Note: for a more detailed chronology of significantevents in computing, see Appendix 1: “Chronology of Computing.”For more on emerging technologies, see trendsand emerging technologies.Further ReadingAllan, Roy A. A History of the Personal Computer: The People andthe Technology. London, Ont.: Allan Publishing, 2001.Campbell-Kelly, Martin. From Airline Reservations to Sonic theHedgehog: A History of the Software Industry. Cambridge,Mass.: MIT Press, 2004.Ceruzzi, Paul E. A History of Modern Computing. 2nd ed. Cambridge,Mass.: MIT Press, 2003.Chandler, Alfred D., Jr. Inventing the Electronic Century: The EpicStory of the Consumer Electronics and Computer Industries,with a New Preface. Cambridge, Mass.: Harvard UniversityPress, 2005.Computer History Museum. Available online. URL: http://www.computerhistory.org/. Accessed June 10, 2007.Ifrah, Georges. The Universal History of Computing: From the Abacusto the Quantum Computer. New York: Wiley, 2002.NetHistory. Available online. URL: http://www.nethistory.info/index.html. Accessed August 7, 2007.Hollerith, Herman(1860–1929)AmericanInventorHerman Hollerith invented the automatic tabulating machine,a device that could read the data on punched cards and displayrunning totals. His invention would become the basisfor the data tabulating and processing industry. Hollerithwas born in Buffalo, New York, and graduated from theColumbia School of Mines. After graduation, he went towork for the U.S. Census as a statistician. Among other taskshe compiled vital statistics for Dr. John Shaw Billings, whosuggested to Hollerith that using punched cards and somesort of tabulator would help the Census Department keep upwith the growing volume of demographic statistics.Hollerith studied the problem and decided that he couldbuild a suitable machine. He went to MIT, where he taughtmechanical engineering while working on the machine,which was partly inspired by an earlier device that hadused a piano-type roll rather than punched cards as input.

230 home officeFacing vigorous competition and in declining health,Hollerith sold his patent rights to the company that eventuallyevolved into IBM, the company that would cometo dominate the market for tabulators, calculators, andother office machines. The punched card, often called theHollerith card, would become a natural choice for computerdesigners and would remain the principal means ofdata and program input for mainframe computers untilthe 1970s.Further ReadingAustrian, G. D. Herman Hollerith: Forgotten Giant of InformationProcessing. New York: Columbia University Press, 1982.Kistermann, F. W. “The Invention and Development of the HollerithPunched Card.” Annals of the History of Computing, 13,245–259.Russo, Mark. “Herman Hollerith: The World’s First StatisticalEngineer.” Available online. URL: http://www.history.rochester.edu/steam/hollerith. Accessed August 7, 2007.The Hollerith tabulator and sorter box, invented by Herman Hollerithand used in the 1890 U.S. census. It “read” cards by passingthem through electrical contacts. (Hulton Archive / GettyImages)The peripatetic Hollerith soon got a job with the U.S. PatentOffice, partly to learn the procedures he would need to followto patent his tabulator. He applied for several patents,including one for the punched-card tabulator. He tested thedevice with vital statistics in Baltimore, New York, and thestate of New Jersey.Hollerith’s mature system included a punch device thata clerk could use to record variable data in many categorieson the same card (a stack of cards could also be prepunchedwith constant data, such as the number of the census district).The cards were then fed into a device something likea small printing press. The top part of the press had anarray of spring-loaded pins that connected to tiny pots ofmercury (an electrical conductor) in the bottom. The pinswere electrified. Where a pin encountered a punched holein the card, it penetrated through to the mercury, allowingcurrent to flow. The current created a magnetic field thatmoved the corresponding counter dial forward one position.The dials could be read after a batch of cards was finished,giving totals for each category, such as an ethnicityor occupation. The dials could also be connected to countmultiple conditions (for example, the total number of foreign-borncitizens who worked in the clothing trade).Aided by Hollerith’s machines, a census unit was ableto process 7,000 records a day for the 1890 census, aboutten times the rate in the 1880 count. Starting around 1900,Hollerith brought out improved models of his machinesthat included such features as an automatic (rather thanhand-fed) card input mechanism, automatic sorters, andtabulators that boasted a much higher speed and capacity.Hollerith machines soon found their way into governmentagencies involved with vital statistics, agricultural statistics,and other data-intensive matters, as well as insurancecompanies and other businesses.home officeThe widespread use of the personal computer and associatedperipherals such as printers has made it more practicalfor many people to do at least part of their work fromtheir homes. In addition to traditional freelance occupationssuch as writing and editing, many other businessesincluding consulting, design, and sales can now be conductedfrom a home office. Computer hardware and softwaremakers began to target a distinctive market niche thatis sometimes referred to as SOHO (Small Office / HomeOffice), thus including both actual home offices and smallcommercial offices.As a market, the SOHO has somewhat different requirementsthan the large offices traditionally served by majorcomputer vendors:• Relatively modest PCs as compared to heavy-duty fileservers or workstations• Peripherals shared by two or more PCs (although theplummeting price of printers made it common to provideeach PC with its own printer)• The need for a small “footprint”—that is, minimizingthe space taken up by the equipment. Multifunctionperipherals (typically incorporating printer, scanner,copier, and perhaps a fax machine) are a popular solutionto this requirement.• A simple local network (see local area network)with shared Internet access• Low-end or midrange software (such as MicrosoftWorks or Office Small Business edition as opposed tothe full-blown Office suite)• Application for collaboration and productivity deliveredvia the Web (such as Google Apps) may also bean attractive alternative.• Available installation and support (since many homeusers lack technical hardware or system administrationskills)

Hopper, Grace Murray 231Although the home or small office remains a significantmarket segment, specific targeting to the segment hasbecome more difficult. With falling PC prices and increasingcapabilities, there is little difference today between amid-level “consumer” computer system and the kinds ofsystems previously marketed for home office use.Further ReadingAttard, Janet. The Home Office and Small Business Answer Book.2nd ed. New York: Owl Books, 2000.Ivens, Kathy. Home Networking for Dummies. 4th ed. Hoboken,N.J.: Wiley, 2007.Orloff, Erica, and Kathy Levinson. The 60-Second Commute: AGuide to Your 24/7 Home Office Life. Upper Saddle River, N.J.:Prentice Hall, 2003.Slack, S. E. CNET Do-It-Yourself Digital Home Office Projects. Berkeley,Calif.: McGraw-Hill Osborne Media, 2007.Small Business Computing. Available online. URL: http://www.smallbusinesscomputing.com/. Accessed August 7, 2007.SOHO Computing. Available online. URL: http://www.sohocomputing.info/. Accessed August 7, 2007.Hopper, Grace Murray(1906–1992)AmericanComputer ScientistGrace Brewster Murray Hopper was an innovator in thedevelopment of high-level computer languages in the 1950sand 1960s. She is best known for her role in the developmentof COBOL, which became the premier language forbusiness data processing.Hopper was born in New York City. She graduated withhonors with a B.A. in mathematics and physics from VassarCollege in 1928, and went on to receive her M.A. and Ph.D.in mathematics at Yale University. She taught at Vassar from1931 to 1943, when she joined the U.S. Naval Reserve atthe height of World War II. As a lieutenant (J.G.), she wasassigned to the Bureau of Ordnance, where she worked inthe Computation Project at Harvard under pioneer computerdesigner Howard Aiken (see Aiken, Howard). Shebecame one of the first “coders” (that is, programmers) forthe Mark I. After the war, Hopper worked for a few yearsin Harvard’s newly established Computation Laboratory. In1949, however, she became senior mathematician at theEckert-Mauchly Corporation, the world’s first commercialcomputer company, where she helped with program designfor the famous UNIVAC. She stayed with what became theUNIVAC division under Remington Rand (later SperryRand) until 1971.While working with UNIVAC, Hopper’s main focus wason the development of programming languages that couldallow people to use symbolic names and descriptive statementsinstead of binary codes or the more cryptic forms ofassembly language (see assembler). In 1952, she developedA-0, the first compiler (that is, a program that could translatelanguage statements to the corresponding low-levelmachine instructions). She then developed A-2 (a compilerthat could handle mathematical expressions), and then in1957 she developed Flow-Matic. This was the first compilerGrace Murray Hopper created the first computer program compilerand was instrumental in the design and adoption of COBOL.When she retired, she was the first woman admiral in U.S. Navyhistory. (Unisys Corporation)that worked with English-like statements and was designedfor a business data processing environment.In 1959, Hopper joined with five other computer scientiststo plan a conference that would eventually result in thedevelopment of specifications for a “Common Business Language.”Her earlier work with Flow-Matic and her designinput played a key role in the development of what wouldbecome the COBOL language.Hopper retained her Navy commission and even afterher retirement in 1966 she was recalled to active duty towork on the Navy’s data processing needs. She finallyretired in 1986 with the rank of rear admiral. Hopper spokewidely about data processing issues, especially the need forstandards in computer language and architecture, the lackof which she said cost the government billions of dollars inwasted resources. Admiral Hopper died on January 1, 1992,in Arlington, Virginia.Hopper received numerous awards and honorary degrees,including the National Medal of Technology. (The navynamed a suitably high-tech Aegis destroyer after her in1996.) The Association for Computing Machines (ACM)created the Grace Murray Hopper Award to honor distinguishedyoung computer professionals. Hopper has becomea role model for many girls and young women consideringcareers in computing.

232 HTML, DHTML, and XHTMLFurther Reading“Grace Brewster Murray Hopper” [biography]. St. Andrews University[Scotland] School of Mathematics and Statistics.Available online. URL: http://www-history.mcs.st-andrews.ac.uk/Biographies/Hopper.html. Accessed August 7, 2007.Grace Hopper Celebration of Women in Computing. Availableonline. URL: http://gracehopper.org. Accessed August 7, 2007.Marx, Christy. Grace Hopper: The First Woman to Program the FirstComputer in the United States. New York: Rosen PublishingGroup, 2003.Williams, Kathleen Broome. Grace Hopper: Admiral of the CyberSea. Annapolis, Md.: Naval Institute Press, 2004.HTML, DHTML, and XHTMLIn developing the World Wide Web, Tim Berners-Lee (seeBerners-Lee, Tim) had to provide several basic facilities.One was a protocol, HTTP, for requesting documents overthe network (see world wide web). Another was a systemof links between documents (see hypertext and hypermedia).The third was a way to embed instructions in thepages so that the Web browser could properly display thetext and graphics. Berners-Lee created HTML (HypertextMarkup Language) for this purpose. It is based on the moreelaborate SGML (Standard Generalized Markup Language).The basic “statement” in HTML is the tag. Tags aredelimited by angle brackets (). Tags that affect a documentor section of a document come in pairs, with the secondmember of the pair preceded by a slash. For example,the tagsindicate the beginning and end of an HTML document,while and delimit text that should berendered in boldface.Besides specifying such things as headings, font, fontsize, and typestyles, HTML includes tags for Web-relatedfunctions. One of the most useful is the A, or “anchor”tag. As with some other HTML tags, the A tag is used withattributes that further specify what it so be done. The A tagis usually used with the or Hypertext Referenceattribute, which specifies a document that is to be linked tothe current document so that the user can click on a highlightto go there. For example:Glossary of Computer Termsspecifies a link to a particular page at a particular site.The link will appear in the browser as the highlighted textGlossary of Computer Terms. If clicked, the browser willload the HTML page titled Glossary.Implementation and ExtensionsInserting HTML tags by hand is a tedious and error-proneprocess (for example, it’s easy to omit a bracket or a slashor add “illegal” spaces within tags). Fortunately, there arenow many HTML editor programs that let users insert theappropriate elements much in the way word processorsmake it easy to specify fonts and formatting. (Indeed, programssuch as Microsoft Word allow users to convert andsave documents in HTML format.)HTML has been extended in a number of ways. First,new features have been added to later versions of the lan-An HTML hyperlink embedded in a Web page. The anchor link gives the address (URL) of the linked page, as well as specifying the text thatwill appear in the link, which will be rendered by the Web browser in a special color or font.

hypertext and hypermedia 233guage, including better support for frames, columns, tables,and other formats. Browser developers have also adopteda system that allows document authors to define generalstyles to ensure consistent document appearance (see cascadingstyle sheets). Style sheets can inherit styles fromother style sheets, allowing an organization to create generalstyle sheets that can then be refined to create specializedstyles for particular types of documents. The latestversion of HTML (as of 2007) is 4.01, with 5.0 still in draft.Dynamic HTML (DHTML) is a set of techniques thatallow otherwise fixed (“static”) HTML pages to be changedas users are viewing them. A scripting language (see, forexample, JavaScript) is used to change the specifications(usually via the style sheet). The programming interfaceto the Web page is the document object model (see dom).DHTML can be used, for example, to create drop-downmenus or “rollover” buttons that change as the mouse navigatesover them. Even simple games have been written inDHTML to run in Web browsers. DHTML should be distinguishedfrom other dynamic techniques such as server-sidescripting (see Perl and php), which changes the page beforeit is presented to the user, and asynchronous techniquesthat can change a part of a page without reloading it (seeAjax).XHTML is essentially a rewriting of HTML according tothe syntax of the Extensible HyperText Markup Language(see xml). Because of the stricter syntax rules for XML,XHTML cannot use many of the earlier free-form structuresof HTML. However, because XML has become so prevalenta means for connecting Web pages to data sources, there aremany xmL tools that XHTML authors can use for parsingand syntax checking. As of 2007, XHTML 1.1 is the prevailingstandard, but a draft 2.0 version represents a more thoroughbreak from the elements of the original HTML.Further ReadingFreeman, Eric, and Elisabeth Freeman. Head First HTML with CSSand XHTML. Sebastapol, Calif.: O’Reilly Media, 2005.Goodman, Danny. Dynamic HTML: The Definitive Reference. 3rded. Sebastapol, Calif.: O’Reilly Media, 2006.Lloyd, Ian. Build Your Own Website the Right Way Using HTML &CSS. Lancaster, Calif.: SitePoint, 2006.Musicano, Chuck, and Bill Kennedy. HTML & XHTML: The DefinitiveGuide. 6th ed. Sebastapol, Calif.: O’Reilly Media, 2006.Olsson, Tommy. “Bulletproof HTML: 37 Steps to Perfect Markup.”Sitepoint. Available online. URL: http://www.sitepoint.com/article/html-37-steps-perfect-markup. Accessed August 7, 2007.Tittel, Ed, and Mary Burmeister. HTML 4 For Dummies. 5th ed.Hoboken, N.J.: Wiley, 2005.hypertext and hypermediaMost computer users today are familiar with the conceptof hypertext, even if they don’t often use the term itself.Each time a Web user clicks on a link on a Web page, heor she is using hypertext. Most on-line help systems alsouse hypertext to take the reader from one topic to another,related topic. The term hypermedia acknowledges modernsystems’ use of many kinds of resources other than plaintext, including still images, videos, and sound recordings.In a traditional document, the reader is generallyassumed to proceed sequentially from the beginning to theend. (Although there may well be footnotes or cross-referenceswithin the document, these are generally experiencedas temporary divergences from the primary, sequential narrative.)Generally speaking, each reader might be expectedto acquire roughly the same set of facts from the document.In a hypertext document, however, the links betweentopics create multiple potential paths for readers. To theextent the author has provided links between all relatedtopics, the reader is free to pursue his or her particularinterests rather than being bound by a sequential structureimposed by the author. For example, in a document thatdiscusses various organisms in an ecology and the effects ofclimate and vegetation, one reader might choose to exploreone organism in depth, following links from it to otherresources devoted to that organism (including outside Webpages, images, videos, and so on). Another reader might beinterested specifically in the effects of rainfall on the ecologyas a whole and follow a completely different set of linksto sites having climatological data.History and DevelopmentIn 1945, a time when the very first digital computers werecoming on-line, Vannevar Bush, a pioneer designer of analogcomputers, proposed a mechanism he called the Memex(see Bush, Vannevar). This system would link portions ofdocuments to allow retrieval of related information. Theproposal was impracticable in terms of the very limitedcapacity of computers of the time. By the 1960s, when computershad become more powerful (and the minicomputerwas beginning to be a feasible purchase for libraries andschools), another visionary, Theodore Nelson, coined theterms hypertext and hypermedia. He suggested that networking(a technology then in its infancy) could allow forwhat would eventually amount to a worldwide database ofinterconnected information. Nelson developed his specificationsfor a system he called Xanadu, but he was unable tocreate a working version of the system until the late 1990s.However, in 1968 Douglas Engelbart (also known as theinventor of the computer mouse) demonstrated a more limitedbut workable hypertext system called NLS/Augment.During the 1970s and 1980s, a variety of hypertext systemswere created for various platforms, including Guideand Toolbook for MS-DOS and Windows PCs. Perhapsthe most influential system was Hypercard, developed forApple’s Macintosh. While Hypercard did not have a completeset of facilities for creating hypertext, the flexible,programmable, linkable “cards” could be used to implementhypertext documents. Many encyclopedias and otherreference products on CD-ROM began to implement someform of hypertext links.The true explosion of hypertext came with the developmentand growth of the World Wide Web throughout the1990s. Hypertext on the Web is implemented through theuse of HTTP (HyperText Transport Protocol) over the Internet’sTCP/IP protocol and by coding documents in HTML(Hypertext Markup Language). (See html, Internet, tcp/ip, and World Wide Web.)

234 hypertext and hypermediaImplementationA hypertext document consists of nodes. A node can be apart of a document that conveys a logical “chunk” of information,such as the text that would be under a particularheading in a traditional document. In some systems nodescan be grouped together as a composite—for example, thesecond-level headings under a first-level heading might beconsidered nodes making up a single composite.The text contains links. A link specifies an anchor orspecific location to which it points. The user normallydoesn’t see the anchor, but rather the marker, which issome form of highlighting (such as a different color) thatindicates that an area is a link that can be clicked on.(In systems such as the Web, link markers need not betextual. Small pictures are often used as visual link markers.)Web browsers and other hypertext programs oftensupplement the use of links with various navigation aids.These can include buttons for traversing back or forwardthrough a list of recently visited links, a history list fromwhich previous links can be selected, and bookmarks thatallow the user to save and descriptively label importantlinks for easier future access.Hypertext is becoming the dominant paradigm for presentingtechnical or other reference information. With lessstructuredtext, hypertext links are usually considered to besupplemental to the traditional structure. The term hypermediarefers to the linking of nontextual material—images,videos, sound files, even Java applets and other programs.(Since both hypertext and hypermedia are now so ubiquitous,the terms themselves seem to be used less frequentlyexcept in an academic context.)Hypertext perhaps achieves its fullest power when itis used for collaborative expression and research. Withoutbeing able to easily link to what is being discussed, blogswould just be static diaries (see blogs and blogging).Wikis, too, depend on linking not only to reference existing,related entries, but to “grow” the tree of knowledgewith “stubs” being put in to encourage other contributors toflesh out related topics (see wikis and Wikipedia). Despitesuggestions to the contrary, hypertext seems to be problematicwith regard to fiction, unless a work is constructed asan explicit hypertext. If hypertext literature becomes popular,it will require that both authors and readers radicallychange their role and expectations with regard to the text.Further ReadingBromme, Rainer, and Elmar Stahl. Writing Hypertext and Learning.Kidlington, Oxford, U.K.: Elsevier Science, 2002.Bush, Vannevar. “As We May Think.” Atlantic Monthly 176, 101–108. Available online. URL: http://www.theatlantic.com/doc/194507/bush.Landow, George P. Hypertext 3.0: Critical Theory and New Mediain an Era of Globalization. 3rd ed. Baltimore: Johns HopkinsUniversity Press, 2006.McCann, Jerome. Radiant Textuality: Literature after the WorldWide Web. New York: Palgrave Macmillan, 2001.Nelson, Theodore. Computer Lib/Dream Machines. Rev. ed. Chicago:Hugo’s Books, 1987.Snyder, I. Hypertext: the Electronic Labyrinth. New York: New YorkUniversity Press, 1997.

IIBMInternational Business Machines is familiarly known asIBM (which is its NYSE symbol) or the nickname “BigBlue.” Arguably it is the world’s oldest information technologycompany, with its roots in card tabulation andother business machines in the late 19th century (seeHollerith, Hermann and punched cards and papertape). Under president Thomas J. Watson Sr., IBM developedwhat would become known as the “IBM card” andmachinery to manage the huge amounts of data requiredby the U.S. Social Security system starting in the mid-1930s. However, IBM would later be criticized for providingthe same technology to Nazi Germany, where it wouldbe used to help round up Jews for the Holocaust. On theother hand, IBM calculating machines were a very necessarypart of the Allied war effort, including the developmentof the atomic bomb.In the 1950s, cold war–related defense work gave IBMaccess to new technologies, including the multiuser, realtimearchitecture needed for the SAGE air defense computer(see government funding of computer research.)Despite UNIVAC’s head start, IBM dominated the commercialcomputer industry from the mid-1950s at least untilthe 1970s (see mainframe). The keystone product was theIBM/360 and later IBM/370 mainframe systems. IBM didnot sell just hardware: It provided complete solutions inthe form of hardware, operating systems, other software,and peripherals. Because of its dominance, it was hard forsmall innovators to gain traction, and many people in theuniversity hacker culture felt about IBM as many of theirdescendants feel about Microsoft today. (IBM’s dress codewith its dark suits reassured business managers but addedto the company’s conformist image.)RetrenchmentIBM went on to set the standard for the most common typeof personal computer in the 1980s (see ibm pc). However,the decade would also bring a gradual decline of IBM’sdominant role. On the desktop, IBM quickly outpaced Apple(despite the latter’s innovation—see Macintosh). However,it became legally possible and profitable to build “clone”PCs that could run the same software as the IBM PC, andoften faster and at lower cost. In the 1990s the growinguse of networks of increasingly powerful desktop machineswould erode the mainframe market. Finally, in 2004 IBMsold its PC business (including the well-regarded Thinkpadseries of laptops) to Lenovo, a Chinese company.Today IBM remains a major seller of computer serversparticularly targeted to Internet businesses. The companyhas also achieved success through designing chipsfor videogame units (see game consoles). However,the company’s overall focus is mainly on business consulting,software (including database and collaborativeproducts), management services, and the exploitation ofits vast trove of patents. IBM has also enthusiasticallyembraced open software and contributed a considerableamount of code to the programming community, such asthe Eclipse program development system (see Linux andopen source).IBM remains the largest computer-related company(after HP). In 2007 the company earned $7 billion on revenueof $98.8 billion.235

236 IBM PCFurther ReadingBashe, Charles J., et al. IBM’s Early Computers. Cambridge, Mass.:MIT Press, 1985.Birth of the IBM PC (IBM Archives). Available online. URL: http://www-03.ibm.com/ibm/history/exhibits/pc25/pc25_birth.html. Accessed September 23, 2007.Black, Edwin. IBM and the Holocaust: The Strategic Alliance betweenNazi Germany and America’s Most Powerful Corporation. NewYork: Three Rivers Press, 2001.Garr, Doug. IBM Redux: Lou Gerstner & the Business Turnaround ofthe Decade. New York: HarperBusiness, 1999.IBM Corporation. Available online. URL: http://www.ibm.com.Accessed September 23, 2007.Pugh, Emerson W. Memories that Shaped an Industry: DecisionsLeading to IBM System/360. Cambridge, Mass.: MIT Press,2000.Pugh, Emerson W., Lyle R. Johnson, and John H. Palmer. IBM’s 360and Early 370 Systems. Cambridge, Mass.: MIT Press, 1991.Soltis, Frank G. Fortress Rochester: The Inside Story of the IBMSeries. Loveland, Colo.: 29th Street Press, 2001.IBM PCBy 1981, a small but vigorous personal computer (PC)industry was offering complete desktop computer systems.Apple’s Apple II offered color graphics and expandabilitythrough an “open architecture”—slots into which cardsdesigned by third-party vendors could be plugged. Whilethe Apple II had its own DOS (disk operating system) asdid Radio Shack’s TRS-80, most microcomputers sold in thebusiness market used CP/M, an operating system developedby Gary Kildall and his company Digital Research.Meanwhile, IBM, the world’s largest computer company(see ibm), had quietly created a special team headedby Phillip (“Don”) Estridge and tasked with designing apersonal computer. Unlike the case with the company’smainframe development, the team was given considerablefreedom in choosing architecture and components—butthey were told they would have to have a machine ready forthe market in one year.Because of the short time frame, the team chose thirdpartycomponents already well established in the market,including the monitor, floppy disk drive, and a printer.Unlike Apple and most other companies, IBM created twoseparate video display systems, one monochrome (MDA)for sharp text for business applications and the threecolorCGA system for the game and education markets (seegraphics card).The IBM team also adopted standards from the emergingmicrocomputer industry instead of trying to use existingmainframe standards. For example, they used the ASCIIcode to represent characters, not the EBCDIC code usedon IBM mainframes. They also chose the Intel 8086 and8088 microprocessors, which had an instruction set similarto that of the Intel 8080 used in many CP/M systems(see microprocessor). This would make it easy for softwaredevelopers to create IBM PC versions of their softwarequickly so that the new machine would have a repertoire ofbusiness software.One might have expected that IBM would also adopt aversion of CP/M as the PC’s operating system, taking advantageof the closest thing to an existing industry standard.However, CP/M was relatively expensive, and negotiationswith Digital Research stumbled, leaving an opening for amuch smaller company, Microsoft, to sell a DOS based onsoftware it had licensed from Seattle Computer Products.While IBM did offer CP/M and another operating systembased on the UC San Diego Pascal development system,Microsoft DOS, which became known as PC-DOS (and laterMS-DOS), was cheapest and effectively became the defaultoffering (see ms-dos).When IBM officially announced its PC in April 1981,Apple took out full-page ads “welcoming” the new competitorto what it considered to already be a mature industry.But by the end of 1983, a million IBM PCs had beensold, dwarfing Apple and other brands. From then on, whileApple would go on to announce its distinctive Macintosh in1984, the IBM machine would set the industry standard. Tomost people, “PC” would mean “IBM PC.”Open Standards and ExpansionAs more businesses bought IBM PCs, the company steadilyexpanded the machine’s capabilities to meet the demandsof the business environment. The next model, the PC-XT,introduced in 1982, included a hard disk drive and moresystem memory. As software became more demanding, theneed for a faster and more capable processor also becameapparent. In 1984, IBM responded with the PC-AT, whichused the Intel 80286 processor, combining the faster processorwith a wider (16-bit) and faster data bus (see bus).However, IBM would not have the market to itself. Aconsequence of the use of an open, expandable architectureand “off the shelf” processor and other components is thatother companies could market PCs that were compatiblewith IBM’s (that is, they could run the same operating systemand applications software). Although competitors couldnot legally make a simple copy of the read-only memory(ROM) BIOS, the code that enabled the components to communicate,they could reverse-engineer a functional equivalent.The first major competitor in what became known asthe “PC Clone” market was Compaq, which also offered animproved video display and a transportable model. Zenith,Tandy (Radio Shack), and HP also offered “name-brand” PCclones.In 1987, IBM tried to establish a proprietary standard byintroducing the PS/2 line, which featured a 3.5-inch floppydrive (standard PC compatibles used 5.25-inch drives), anew high-resolution graphics standard (VGA), a new systembus (MCA or Microchannel Architecture), and a newoperating system (OS/2). Despite some technical advantages,the PS/2 achieved only modest success. Since thecard slots were incompatible with the previous standard,existing expansion products could not be used. Microsoftsoon came out with a new operating environment, Windows,which while inferior in multitasking capabilities toOS/2 was easier to use (see user interface and MicrosoftWindows).By the 1990s, it was clear that IBM no longer controlledthe standards for PCs. (Indeed, IBM soon abandoned thePS/2 MCA architecture and returned to the earlier stan-

identity in the online world 237dard, which competitors had never left.) Instead, the industryincrementally built upon what had become known asthe ISA (Industry Standard Architecture), supplementingit with a new kind of expansion card connector called PCI.Currently, IBM is in the second tier in PC sales behindindustry leaders Dell and Compaq, having a market sharecomparable to Hewlett-Packard and Gateway. IBM also didrelatively well in the laptop computer sector with its Thinkpadseries, before selling it to Lenovo.Today’s industry standards are effectively determinedby two companies: the chip-maker Intel and the softwaregiant Microsoft. Indeed, “standard” PCs are now oftencalled “Wintel” machines. The direct-order giant Dell andits competitors HP and Lenovo dominate the “commodityPC” market. However, by creating a standard that was flexibleenough for two decades of PC development, IBM madea lasting contribution to computing comparable to its innovationsin the mainframe arena.Further ReadingDell, Deborah A,. and J. Jerry Purdy. Thinkpad: a Different Shade ofBlue. Indianapolis, Ind.: Sams, 1999.Dell, Michael. Direct from Dell: Strategies that Revolutionized anIndustry. New York: HarperBusiness, 2000.Gilster, Ron. PC Hardware: a Beginner’s Guide. New York: McGraw-Hill, 2001.Hoskins, Jim, and Bill Wilson. Exploring IBM Personal Computers.10th ed. Gulf Breeze, Fla.: Maximum Press, 1999.Ling, Zhigun, and Martha Avery. The Lenovo Affair: The Growth ofChina’s Computer Giant and Its Takeover of IBM-PC. New York:Wiley, 2006.identity in the online worldThere are two aspects of identity in cyberspace, both ofwhich are intriguing but problematic: Outer identity is thename or other descriptors that are identified by other peopleas belonging to a particular person, and inner identity isa person’s sense of who or what he or she “really is.”Users of online systems such as chat rooms or gameshave the ability to use a variety of names (pseudonyms)or to be effectively anonymous (see anonymity and theInternet). In games, the identity used by a player is representedby a virtual representation called an avatar. Otherplayers (through their own avatars) will encounter the avatarand identify it by physical appearance, behavior, andwhat it tells about itself (the “back story”).While opportunities to do this emerged in the 1970s withpaper-and-dice role-playing games such as the very popularDungeons and Dragons, there are significant differencesbetween online identity and these earlier games. Peopleplayed “D&D” in person, so it was relatively easy to maintaina distinction between a character a person was “running” andthe person himself or herself. Also, these role-playing sessionswere fixed in time and place: After slaying the dragon,the players went home. Indeed even the term “role-playing”made the comfortable assumption that the activity was a pretend,make-believe identity assumed by the player.Virtual game worlds began in the 1980s with text-basedMUDS (multi-user dungeons) and similar online environments.Today game worlds are graphically immersive andpersistent. Although there are games focused on the traditionalbattles and quests, others such as Second Life are bestdescribed not as games at all but literal second or alternativelives that persons can participate in for hours a day. Inthese worlds an avatar can own property and make commitments,even a virtual form of marriage. In many cases ingamegoods and money can actually be exchanged for “realworld” money. And crucially, unlike the D&D encounter,in these virtual worlds the “real person” behind an avatarneed never be revealed.Constructing IdentitiesThe online world invites people to construct and try outidentities. Because of the vital role they play in people’ssense of self and their social interactions, sexual or genderidentity is a particularly important issue. The onlineworld has some clear advantages for persons who are experimentingwith different identities (such as transgender). Aman, for example, can create a female avatar that reallylooks female. Further, people can act out sexual encounterswithout the possible physical consequences of violence ordisease. On the other hand, people can still be hurt psychologically,and online relationships can take on added risksand challenges by eventually becoming physical ones.There are also venues where there can be “hybrid” identities.In a site such as MySpace, a person can construct thekind of “face” he or she wants to present to the world andinteract with the pages of other people. Here the onlineidentity is often tied with a physical one (potentially creatingvulnerability) but need not be (creating the potential fordeception).Young people in particular will have to deal with theopportunities and challenges of multiple virtual identities.On the one hand, young people are very adaptable, especiallyto new technologies. On the other hand, youth andparticularly adolescence has always been a time of innerconflicts and a search for lasting identity (see young peopleand computing).The deeper philosophical and psychological implicationsof cyberspace are intriguing. According to some modernpsychological theories (such as Marvin Minsky’s “society ofmind”), the mind does not consist of a single ego perhaps inconflict with unconscious forces, but rather, many separate“agents” that interact as they seek various goals. From thatpoint of view the online world expands that model intosocial space and may lead to a world in which each physicalperson may have many virtual persons associated with it.Online identities are becoming a fertile area of researchin psychology and sociology. Pioneering work has beendone by psychologist Sherry Turkle, who has explored differingmale and female styles of relationship to technology,how technology affects children, and other issues.The social and legal implications of online identity areequally challenging. Can an avatar be sued? Can one avatarcommit a criminal act (perhaps even rape) against another?Might an avatar have privacy rights and the right of publicity?The legal system has hardly begun to consider suchquestions, and they are becoming more urgent as everything

238 identity theftfrom meetings to concerts takes place in virtual worlds. It ispossible that eventually online worlds will be allowed tocreate their own internal legal systems, perhaps subject to“metarules” about how they are to be enforced within thecontext of physical jurisdictions (see cyberlaw).Further ReadingCooper, Robbie. Alter Ego: Avatars and Their Creators. London:Chris Boot, 2007.Schroeder, Ralph, and Ann-Sofie Axelsson, eds. Avatars at Workand Play: Collaboration and Interaction in Shared Virtual Environments.New York: Springer, 2007.“Sexual Identity Online.” MYCyclopedia of New Media. Availableonline. URL: http://wiki.media-culture.org.au/index.php/Sexual_Identity_Online. Accessed September 23, 2007.Thomas, Angela. Youth Online: Identity and Literacy in the DigitalAge. New York: Peter Lang, 2007.Turkle, Sherry. Life on the Screen: Identity in the Age of the Internet.New York: Simon & Schuster, 1995.———. The Second Self: Computers and the Human Spirit. TwentiethAnniversary ed. Cambridge, Mass.: MIT Press, 2005.identity theftIdentity theft is essentially the impersonation of someonein order to gain use of their resources or, occasionally, toescape the consequences of previous criminal behavior.The most common motive for identity theft is to gain accessto a person’s financial resources, such as credit cards orchecking accounts, or to obtain credit or services. (Sometimesa distinction is made between identity theft, wherethe victim’s identity is assumed and effectively becomesthe perpetrator’s identity, and identity fraud, where informationis only used long enough to complete particulartransactions.)Identity thieves must first obtain the necessary informationto pose as their victim. This can be done by physicallyobtaining such items as checks, receipts, credit offers, andso on from the trash or mail. Information such as name,address, account numbers, and the ultimate prize, theSocial Security number, can then be used, for example, toapply for credit in the victim’s name, or buy goods and havethem shipped to the perpetrator’s address.People can minimize the risk of physical identity theftby securing their mail and shredding sensitive documents.However, the fastest-growing venue for identity theft isonline. The online world presents additional opportunitiesto the criminals, the necessity of new precautions, and difficultchallenges for law enforcement.Digital information useful for identity theft can beobtained in a variety of ways. It can be physically stolen inthe form of laptops or portable storage devices or obtainedelectronically by breaking into and compromising computersystems (see computer crime and security). Programscan exploit operating-system or software flaws to travelfrom one networked PC to another and e-mail informationback to the perpetrator (see computer virus). Finally,users can be coerced, enticed, or otherwise tricked intoproviding the information (such as passwords) themselves,via authentic-looking institutional Web sites (see phishingand spoofing).Incidence and PreventionAccording to various surveys, the incidence of identity theftincreased substantially between 2001 and 2003. There areconflicting views of recent trends. Data for 2006 from JavelinStrategy and Research suggests a decrease (10.1 millionU.S. adult victims in 2003 and 8.9 million in 2006).However, data from the Federal Trade Commission records246,035 actual complaints of identity theft in 2006, makingit by far the number one item on its list of consumerfraud complaints. (Of these, 25 percent reflected credit cardfraud, and phone/utilities fraud and bank fraud each represented16 percent.)To give some further perspective, according to the InternetCrime Complaint Center (a joint program of the FBIand the National White Collar Crime Center), identity theftamounted to only 1.6 percent of reported cyber crimes.(Credit card or check fraud without confirmed identitytheft added up to 9.7 percent.) Nevertheless, however measured,it is clear that identity theft remains a very seriousproblem.Until recent years, response to identity theft complaintsby law enforcement tended to be ineffectual and frustratingto victims. This was probably due to a combination ofcircumstances, including many police officers being unfamiliarwith the nature of the crime or technology involved,unsure about how to proceed, and not even certain theyhad jurisdiction. This situation has improved considerably,however, with national organizations, greater interagencycooperation (including between federal, state, and localagencies), and strong and explicit laws against identity theftand fraud. (The Identity Theft and Assumption DeterrenceAct of 2003 now makes possession of “any means of identification”to “knowingly transfer, possess, or use withoutlawful authority” a federal crime.)The main goal for consumers, however, should be prevention.Steps that can greatly reduce the chance of becominga victim of online identity theft include:• Keep security software (antivirus, antispam, antispyware)up to date.• Do not click on links in e-mail that purports to befrom a financial institution, government agency,online merchant or auction service. Use the browser’saddress box to go directly to the relevant site.• Do not post addresses, account numbers, or SocialSecurity numbers online, including chat rooms orsocial networking sites. Teach children likewise, andconsider installing software that can block the postingof such information.• Make sure that the financial institutions and merchantsthat one uses have acceptable privacy policiesand policies for dealing with “data breaches” andother loss of sensitive information.• If you suspect you have been victimized, go to a sitesuch as the Identity Theft Resource Center or thePrivacy Rights Clearinghouse to learn how to stopfurther losses and reestablish credit and accounts.

information design 239Further ReadingCullen, Terry. The Wall Street Journal Complete Identity Theft Guidebook:How to Protect Yourself from the Most Pervasive Crime inAmerica. New York: Three Rivers Press, 2007.“How Many Identity Theft Victims Are There? What Is the Impacton Victims?” Privacy Rights Clearinghouse. Available online.URL: http://www.privacyrights.org/ar/idtheftsurveys.htm.Accessed September 23, 2007.Identity Theft Resource Center. Available online. URL: http://www.idtheftcenter.org/. Accessed September 23, 2007.“Identity Theft Tops FTC Complaints for 2006.” Consumeraffairs.com, February 8, 2007. Available online. URL: http://www.consumeraffairs.com/news04/2007/02/ftc_top_10.html.Accessed September 23, 2007.Internet Crime Complaint Center. Available online. URL: http://www.ic3.gov/. Accessed September 23, 2007.Privacy Rights Clearinghouse. Available online. URL: http://www.privacyrights.org/. Accessed September 23, 2007.image processingImage processing is a general term for the manipulationof a digitized image to produce an enhanced or more convenientversion. Some of the earliest applications were inthe military (aerial and, later, satellite reconnaissance) andin the space program. The military and space programshad a great need for extracting as much useful informationas possible from images that were often gathered underextreme or marginal conditions. They also needed to makecameras and other hardware components simultaneouslymore compact and more efficient, and generally had thefunds to pay for such specialized developments.Once developed, higher-quality image processing systemsfound their way into other applications such as domesticsurveillance and medical imaging. The development ofcameras that could directly turn light into digitized images(see photography, digital) made image processing seamlessby avoiding the necessity of scanning images from traditionalfilm.Image processing applications can be divided intothree general categories: enhancement, interpretation, andmaintenance.EnchancementEnhancement includes bringing out objects of interest (suchas enemy vehicles or a particular rock formation on Mars)from the surrounding background by enhancing contrastor applying appropriate filters to block out the background.More sophisticated filters can also be used to compensatefor defects in the original image, such as “red-eye,” blur,and loss of focus. Today’s image processing programs, suchas the popular Adobe Photoshop, make relatively sophisticatedimage manipulation techniques available to interestedamateurs as well as professionals. More sophisticated imageenhancement techniques include the creation of 3D imagesbased upon the differences calculated from a number ofphotos shot from slightly different angles.A considerable amount of image enhancement takesplace even before the photo is taken. Today’s versatile cameras(see photography, digital) include a variety of modesthat are preset for different scenarios such as indoor portraitor low light. After the picture is taken, photo managementprograms (often bundled with the camera or even includedin the operating system) not only help organize photos, butalso provide simple ways to crop or enhance them.InterpretationInterpretation refers to manipulation designed to helphuman observers obtain more and better informationfrom the image. For example, “false color” can be used toheighten otherwise imperceptible color differences in theoriginal image, or to translate nonvisual information (suchas heat or radio emission levels) into visual terms.Artificial intelligence algorithms can also be employedto automatically analyze images for features of interest (seepattern recognition and computer vision). In fieldssuch as military reconnaissance this might allow a highvolume of imagery to be prescreened, with images meetingcertain criteria “flagged” for the attention of humaninterpreters.MaintenanceMaintenance includes archiving of images, often with theaid of compression to reduce the amount of storage spacerequired (see data compression). It can also include therestoration of images that may have been degraded (as fromchemical decomposition of stored film.) This can be doneeither by creating a reversible mathematical model of thedegradation process (thus, for example, restoring colorsthat have changed through oxidation or other processes)or by creating a model of how the image was formed in thefirst place and comparing its output to the existing image.Further ReadingGIMP, the GNU Image Manipulation Program. Available online.URL: http://www.gimp.org/. Accessed August 8, 2007.Gonzalez, Rafael, and Richard E. Woods. Digital Image Processing.3rd ed. Upper Saddle River, N.J.: Prentice Hall, 2007.Hanbury, Allan. “A Short Introduction to Digital Image Processing.”Available online. URL: http://www.prip.tuwien.ac.at/~hanbury/intro_ip/. Accessed August 8, 2007.MathWorks Image Processing. Available online. URL: http://www.mathworks.com/applications/imageprocessing/. AccessedAugust 8, 2007.Seul, Michael, Lawrence O’Gorman, and Michael J. Sammon.Image Analysis: Description, Examples, and Code. New York:Cambridge University Press, 2000.Ward, Al. PhotoShop for Right-Brainers: Photo Manipulation. Alameda,Calif.: SYBEX, 2004.information designInformation design is concerned with arranging and presentinginformation in ways that enable viewers to use itefficiently and with the greatest benefit. This discipline canbe said to have begun in the 19th century with the developmentof diagrams and maps that present the relationshipbetween two or more variables. These included John Snow’smap of London showing the locations of cholera outbreaksin the 1850s, and a striking 1861 diagram by Joseph Minardthat related the geographical progress of Napoléon’s 1812

240 information retrievalinvasion of Russia with the diminishing size of the Frenchforces. These early examples coincided with a time whenindustrial society was becoming increasingly complex andpopulous, and both government and business needed newways to visualize statistics. Other products to which informationdesign contributes became important in the followingcentury: traffic and transit signs, product warninglabels, and product manuals, to name a few.Some of the basic considerations for information designinclude:• effectiveness at presenting relevant information• selection and arrangement of information• balance of attractiveness and clarity• proper use of the medium (size, materials, etc.)Of course the designer has additional constraints, such asthe purpose of the design (advertising, product documentation,report, etc.), policies of the client, any applicable regulations(such as for warning labels), and so on.From Physical to DigitalMoving from the world of print to the Web brings newresources and challenges to the information designer. Webdesign has many advantages over print—powerful layouttools and perhaps templates, the availability of animationor other effects, the ability to adapt to different audiences,and, above all, interactivity. However, each of these featuresbrings additional choices—not only font and text size,but background, use of images, whether to include animation(such as Flash), and how to design clear and easy-touseforms and other interactive features. Further, designsmay have to adapt to a variety of platforms (large desktopscreens, laptops, PDAs, and mobile devices) and providefor users who have visual impairments or other disabilities(for more, see Web page design). For information displaysdesigned to provide “at a glance” summaries and alertsabout problems, see digital dashboard.Although these concerns may seem far afield from theclassic principles of graphic design, they actually representtechnological extensions of them. It is easy to get lost in theparticulars of designing, for example, Web pages showingstatistical charts, without having thought about whetherthe charts themselves show information clearly and accuratelyin the scales and proportions used.Further ReadingDigital Web Magazine. Available online. URL: http://www.digitalweb.com/.Accessed September 23, 2007.Few, Stephen. Information Dashboard Design: The Effective VisualCommunication of Data. Sebastapol, Calif.: O’Reilly Media,2006.Information Design Journal. John Herndon, Va.: Benjamins PublishingCompany, 1979. Free sample available online. URL:http://www.benjamins.com/cgi-bin/t_bookview.cgi?bookid=IDJDD%2012%3A1. Accessed September 23, 2007.Lipton, Ronnie. The Practical Guide to Information Design. NewYork: Wiley, 2007.Lõwgren, Jonas, and Erik Stolterman. Thoughtful InteractionDesign: A Design Perspective on Information Technology. 2nded. Cambridge, Mass.: MIT Press, 2007.Tufte, Edward R. Envisioning Information. Cheshire, Conn.: GraphicsPress, 1990.———. The Visual Display of Quantitative Information. 2nd ed.Cheshire, Conn.: Graphics Press, 2001.information retrievalWhile much attention is paid by system designers to therepresentation, storage and manipulation of information inthe computer, the ultimate value of information processingsoftware is determined by how well it provides for the effectiveretrieval of that information. The quality of retrieval isdependent on several factors: hardware, data organization,search algorithms, and user interface.At the hardware level, retrieval can be affected by theinherent seek time of the device upon which the data isstored (such as a hard disk), the speed of the central processor,and the use of temporary memory to store data that islikely to be requested (see cache). Generally, the larger thedatabase and the amount of data that must be retrieved tosatisfy a request, the greater is the relative importance ofhardware and related system considerations.Data organization includes the size of data records andthe use of indexes on one or more fields. An index is a separatefile that contains field values (usually sorted alphabetically)and the numbers of the corresponding records. Withindexing, a fast binary search can be used to match theuser’s request to a particular field value and then the appropriaterecord can be read (see hashing).There is a tradeoff between storage space and ease ofretrieval. If all data records are the same length, randomaccess can be used; that is, the location of any record can becalculated essentially by multiplying the record’s sequencenumber by the fixed record length. However, having a fixedrecord size means that records with shorter data fields mustbe “padded,” wasting disk space. Given the low cost of diskstorage today, space is generally less of a consideration.The search algorithms used by the program can alsohave a major impact on retrieval speed (see sorting andsearching). As noted, if a binary search can be done againsta sorted list of fields or records, the desired record can befound in only a few comparisons. At the opposite extreme,if a program has to move sequentially through a wholedatabase to find a matching record, the average number ofcomparisons needed will be half the number of records inthe file. (Compare looking up something in a book’s indexto reading through the book until you find it.)Real-world searching is considerably more complex,since search requests can often specify conditions suchas “find e-commerce but not amazon.com” (see Booleanoperators). Searches can also use wildcards to find a wordstem that might have several different possible endings,proximity requirements (find a given word within so manywords of another), and other criteria. Providing a robust setof search options enables skilled searchers to more preciselyfocus their searches, bringing the number of results downto a more manageable level. The drawback is that complexsearch languages result in more processing (often severalintermediate result sets must be built and internally com-

information theory 241the question into the structured queries most likely to elicitdocuments containing the answer. Ask Jeeves (retired as of2006) and similar search services have thus far been onlymodestly successful with this approach.On a large scale, systematic information retrieval andanalysis (see data mining) has become increasingly sophisticated,with applications ranging from e-commerce andscientific data analysis to counterterrorism. Artificial intelligencetechniques (see pattern recognition) play animportant role in cutting-edge systems.Finally, encoding more information about content andstructure within the document itself can provide moreaccurate and useful retrieval. The use of XML and worktoward a “semantic Web” offers hope in that direction (seeBerners-Lee, Tim; semantic web; and xml).A number of criteria can be used by Web search engines to determinethe likely relevance of search results. Perhaps the most importanttool, however, is feedback from the user.pared to one another). There is also more likelihood thatsearchers will either make syntax errors in their requests orcreate requests that do not have the intended effect.While database systems can control the organizationof data, the pathways for retrieval and the command setor interface, the World Wide Web is a different matter.It amounts to the world’s largest database—or perhapsa “metabase” that includes not only text pages but fileresources and links to many traditional database systems.While the flexibility of linkage is one of the Web’s strengths,it makes the construction of search engines difficult. Withmillions of new pages being created each week, the “webcrawler”software that automatically traverses links andrecords and indexes site information is hard pressed tocapture more than a diminishing fraction of the availablecontent. Even so, the number of “hits” is often unwieldy(see search engine).A number of strategies can be used to provide morefocused search results. The title or full text of a given pagecan be checked for synonyms or other ideas often associatedwith the keyword or phrase used in the search. Themore such matches are found, the higher the degree ofrelevance assigned to the document. Results can then bepresented in declining order of relevance score. The usercan also be asked to indicate a result document that he orshe believes to be particularly relevant. The contents of thisdocument can then be compared to the other result documentsto find the most similar ones, which are presented aslikely to be of interest to the researcher.Information retrieval from either stand-alone databasesor the Web can also be improved by making it unnecessaryfor users to employ structured query languages (see sql)or even carefully selected keywords. Users can simply typein their request in the form of a question, using ordinarylanguage: For example, “What country in Europe has thelargest population?” The search engine can then translateFurther ReadingBell, Suzanne S. Librarian’s Guide to Online Searching. Westport,Conn.: Libraries Unlimited, 2006.Chakrabarti, Soumen. Mining the Web: Discovering Knowledge fromHypertext Data. San Francisco: Morgan Kaufmann, 2002.Grossman, David A., and Ophir Frieder. Information Retrieval:Algorithms and Heuristics. 2nd ed. Norwell, Mass.: Springer,2004.“Information Retrieval Research.” Search Tools Consulting. Availableonline. URL: http://www.searchtools.com/info/inforetrieval.html.Accessed August 8, 2007.Meadow, Charles T., et al. Text Information Retrieval Systems. 3rded. Burlington, Mass.: Academic Press, 2007.information theoryInformation theory is the study of the fundamental characteristicsof information and its transmission and reception.As a discipline, information theory took its impetus fromthe ideas of Claude Shannon (see Shannon, Claude).In his seminal paper “A Mathematical Theory of Communication”published in the Bell System Technical Journalin 1948, Shannon analyzed the redundancy inherent in anyform of communication other than a series of purely randomnumbers. Because of this redundancy, the amount ofinformation (expressed in binary bits) needed to convey amessage will be less than the number in the original message.It is because of redundancy that data compressionalgorithms can be applied to text, graphics, and other typesof files to be stored on disk or transmitted over a network(see data compression).Shannon also analyzed the unpredictability or uncertaintyof information as it is received—that is, the number ofpossibilities for the next bit or character. This is related to thenumber of possible symbols, but since all symbols are usuallynot equally likely, it is actually a sum of probabilities. Shannonused the physics term entropy to refer to this measure. Itis important because it makes it possible to analyze the probabilityof error (caused by such things as “line noise”) in acommunications circuit. Shannon’s basic formula is:C = Blog 2 (1 + P / N)where the channel capacity C is in bits per second, B is thebandwidth, P the signal power, and N the Gaussian noisepower.

242 information warfareShannon found that if as long as the actual data transmissionrate is less than the channel capacity C, an errorcorrectingcode can be devised to ensure that any desiredaccuracy rate is achieved (see error correction). A relatedformula can also be used to find the lowest transmissionpower needed given a specified amount of noise.The influence of Shannon and his disciples on computinghas been pervasive. Information theory provides thefundamental understanding needed for applications in datacompression, signal analysis, data communication, andcryptography—as well as problems in other fields such asthe analysis of genetic mutation or variation.Further ReadingCover, Thomas, and Joy A. Thomas. Elements of Information Theory.2nd ed. Hoboken, N.J.: Wiley, 2006.Gray, R. M. Entropy and Information Theory. New York: Springer,1990. Available online. URL: http://ee.stanford.edu/~gray/it.pdf. Accessed August 8, 2007.Hankerson, Darrel, Greg A. Harris, Jr., and Peter D. Johnson. Introductionto Information Theory and Data Compression. 2nd ed.Boca Raton, Fla.: CRC Press/Chapman & Hall, 2003.IEEE Information Theory Society. Available online. URL: http://www.itsoc.org/. Accessed August 8, 2007.Shannon, Claude. “A Mathematical Theory of Communication.”Bell System Technical Journal 27 (July, October 1948): 379–423, 523–656. Available online. URL: http://plan9.bell-labs.com/cm/ms/what/shannonday/shannon1948.pdf. AccessedAugust 8, 2007.information warfareInformation warfare has many aspects and can be foughton many levels. On the battlefield, it can involve collectingtactical or strategic intelligence and protecting one’s ownchannels of communication. Conversely, it can involve disruptingthe enemy’s means of communication, blocking theenemy’s intelligence gathering, spreading disinformation,and trying to disrupt their decision process. Beyond thebattlefield, media (including the Internet) can be used forpropaganda purposes.All of these objectives today involve the use of digitalinformation and communications systems. Examples include:• analysis of enemy communications using both automatictools and human analysts• cryptography and signal analysis• protection of computer and network infrastructure• attacks and disruptions on enemy information infrastructure,both military and civilian (such as denialof-serviceattacks on Web sites)• use of Web sites to spread disinformation or propagandaHistory and DevelopmentInformation warfare is as old as warfare itself, with suchthings as ruses designed to trick or confuse enemy sentriesor lighting many fires to convince the enemy that one’sarmy was much larger than in reality. Wiretapping andspoof messages began with the telegraph in the mid-19thcentury, and eavesdropping and other tricks with radiowere used in World War I. These arts had greatly increasedin scale and sophistication by World War II—an entire fakearmy corps was “created” to deceive the Germans prior tothe D-day invasion.Information warfare involving computers has been usedin recent conflicts. The active phase of the U.S. attack in thefirst Gulf War in 1991 began with systematic destructionand disruption of Iraqi information and command-and-controlassets through targeted attacks. As a result, the stilllargely intact Iraqi military was left blind as to the comingflank attack by U.S. forces.In 2007 a series of coordinated attacks by unknownparties paralyzed much of Estonia’s Web-based governmentand business structures following a dispute with Russia.To many observers this represents a model for “strategic”information warfare that might be used in future conflicts.(Note that the techniques used in information warfare bythe national military and the kinds of cyber attacks thatmight be favored by terrorists overlap. For the latter, seecyberterrorism.)Further ReadingArmistead, E. Leigh. Information Warfare: Separating Hype fromReality. Washington, D.C.: Potomac Books, 2007.Greenmeier, Larry. “Estonian ‘Cyber Riot’ Was Planned, but MastermindStill a Mystery.” InformationWeek, August 3, 2007.Available online. URL: http://www.informationweek.com/showArticle.jhtml?articleID=201202784. Accessed September23, 2007.Johnson, L. Scott. “Toward a Functional Model of InformationWarfare.” Available online. URL: http://bss.sfsu.edu/fischer/IR%20360/Readings/Information%20War.htm. Accessed September23, 2007.Libicki, Martin C. Conquest in Cyberspace: National Security andInformation Warfare. New York: Cambridge University Press,2007.Rattray, Gregory J. Strategic Warfare in Cyberspace. Cambridge,Mass.: MIT Press, 2001.Waltz, Edward. Information Warfare: Principles and Operations.Boston: Artech House, 1998.Input/Output (I/O)While the heart of a computer is its central processing unitor CPU (the part that actually “computes”), a computermust also have a “circulatory system” through which datamoves between the CPU, the main memory, input devices(such as a keyboard or mouse), output devices (such as aprinter), and mass storage devices (such as a hard or floppydisk drive). Input/Output or I/O processing is the generalterm for the management of this data flow (see also bus,parallel port, serial port, and usb).I/O processing can be categorized according to how arequest for data is initiated, what component controls theprocess, and how the data flows between devices. In mostearly computers the CPU was responsible for all I/O activities(see cpu). Under program control, the CPU initiated adata transfer, checked the status of the device (or area ofmemory) that would be sending or receiving the data, and

Input/Output 243monitored the flow of data until it was complete. While thisarrangement simplified computer architecture and reducedthe cost of memory units or peripheral devices (at a timeSteps in processing an interrupt request (IRQ) in a PC. (1) Thedevice requesting attention signals the Interrupt Controller, whichin turn sends a special signal to the CPU. (2) The CPU savesits state (including internal data and the address of the currentinstruction) to a stack. (3) The CPU gets the interrupt number andother information from the Interrupt Controller, then looks up aset of instructions for processing that particular interrupt. (4) TheCPU executes the interrupt processing code, which generally linksto BIOS code for handling a device such as the keyboard. (5) TheCPU reloads its state information from the stack and resumes theinterrupted processing.when computer hardware was hand-built and relativelycostly), it also meant that the CPU could perform no otherprocessing until I/O was complete.In most modern computers, responsibility for I/O haslargely been removed from the CPU, freeing it to concentrateon computation. There are several ways to implementsuch architecture. One method that has been used onmicrocomputers since their earliest day is interrupt-drivenI/O. This means that the CPU has separate circuits onwhich a device requesting I/O service can “post” a request.The CPU periodically checks the circuits for an interruptrequest (IRQ). If one is found, it can send a query to eachdevice on a list until the correct one is found (the latteris called polling). Alternatively, the overhead involved inpolling can be eliminated by having the IRQ include eithera device identification number or a memory address thatcontains an interrupt service routine (this is called vectoredinterrupts). While interrupts alone do not free the CPU ofthe need to manage the I/O, they do remove the overhead ofhaving to frequently check all devices for I/O.The actual I/O process can also be moved out of theCPU through the use of direct memory access (DMA). Herea separate control device takes over control of the systemfrom the CPU when I/O is requested. It then transfers datadirectly between a device (such as a hard disk drive) anda buffer in main memory. Although the CPU is idle duringthis process, the transfer is accomplished much morequickly because the full capacity of the bus can be used tomove data rather than having to be shared with the flow ofprogram instructions in the CPU.A more sophisticated I/O control device is called a channel.A channel controller can operate completely independentlyof the CPU without requiring that the CPU becomeidle during a transfer. Channels can also act as a sort of specializedCPU or coprocessor, running program instructionsto monitor the data transfer. There are also channels capableof monitoring and controlling several devices simultaneously(this is called multiplexing). The use of channels inmainframes such as the IBM 360 and its descendants is onereason why mainframes still perform a workhorse role inhigh-volume data processing.In microcomputers the trend has also been towardoffloading I/O from the CPU and the main bus to separatecontrollers or channels. For example, the AGP (acceleratedgraphics port) found on most modern PCs acts as achannel between main memory and the graphics controllers(see graphics card). This means that as a programgenerates graphics data it can be automatically transferredfrom memory to the graphics controllers without any loadon the CPU, and over a bus that is faster than the mainsystem bus.Further ReadingBuchanan, William. Applied PC Interfacing, Graphics and Interrupts.Reading, Mass.: Addison-Wesley, 1999.Karbo, Michael B. “About the PC I/O System.” Available online.URL: http://www.karbosguide.com/hardware/module5a1a.htm. Accessed August 8, 2007.White, Ron, and Timothy Downs. How Computers Work. 8th ed.Indianapolis: Que, 2005.

244 installation of softwareinstallation of softwareWhile not often covered in computer science or softwareengineering courses, the process of getting a program towork on a given computer is often nontrivial. In the earlydays of PCs, installation generally involved simply copyingthe main program file and any needed settings files to a diskdirectory and possibly setting up the appropriate driver forthe user’s printer. (A cryptic user interface sometimes madethe latter procedure a frequent occasion for technical supportcalls.) Users generally did not have to make manychoices about what components to install or where to putthem. On the other hand, installation programs sometimesmade changes to a user’s system without notification or theability to “back out.”The ascension of Microsoft Windows to dominance asa PC operating system improved the installation process inseveral ways. Since the operating system and device driverswritten by hardware vendors took over responsibility forinstalling and configuring printers and other devices, usersgenerally didn’t have to worry about configuring programsto work with specific hardware. Particularly with Windows95 and later versions, a standard “installation kit” allowssoftware developers to provide a familiar, step-by-stepinstallation procedure to guide users. Generally, installationconsists of an introductory screen, legal agreement, and theopportunity to choose a hard drive folder for the program.A moving “progress bar” then shows the files being copiedfrom the installation CD to the hard drive. A “readme” filegiving important considerations for using the program isusually provided. Increasingly, software registration is doneby launching the user’s Web browser and directing it to thevendor’s Web site where a form is presented.The installation of drivers accompanying new hardwaresuch as a printer or scanner has been simplified even morethrough the “Plug and Play” feature in modern versions ofWindows. This allows the system to automatically detectthe presence of a new device and either install the driverautomatically or prompt the user to insert a disk or CD (seeplug and play).Installation becomes a much more complicated matterwhen an enterprise has to install from tens to hundredsor thousands of copies of a program on employees’ PCs.While small businesses may simply buy consumer-packagedsoftware and install one copy on each PC, large businessesgenerally obtain a site license allowing a certainnumber of installations (or in some cases, unlimited on-siteinstallations). Organizations must monitor the number ofinstallations of a particular program package to ensure thatlicensing agreements are not violated while trying to useavailable software assets as efficiently as possible. (This issometimes called software asset management or SAM.)An automated installation script can be used to installa copy of the same software on each PC on the company’snetwork—or a utility can be used to copy an exact harddisk image, including fully configured operating systemand applications, to each PC. Alternatively, it is possibleto buy networked versions of some programs. In this casethe application actually runs on a server and is accessedfrom (but not copied to) each user’s PC. This technique hasalso been adopted to provide consumers with an alternativeto stand-alone installation (see application serviceprovider).Installation is only the first part of the story, of course.Most significant programs will experience a steady flowof minor version updates as well as security patches. Forindividual users, setting the program to update automatically(if possible) or periodically checking for updates maybe sufficient. For organizations, the task of making sure allthe deployed copies of the software are up to date can benontrivial, although tools such as Microsoft System Centercan help. (Many Linux distributions such as Ubuntu canautomatically retrieve all updates for installed packages.)Linux and UNIX systems have also evolved more sophisticatedinstallation systems in order to keep up with today’smore complex applications and distributions. One commonsolution used by Red Hat and other Linux vendors is a“package” system where the user selects programs and featuresand the system identifies the components (packages)that must be installed to enable them.Further ReadingBrowne, Christopher. “Linux System Configuration Tools.” Availableonline. URL: http://linuxfinances.info/info/linuxsysconfig.html. Accessed August 8, 2007.Chappell, David. Introducing Microsoft System Center. Availableonline. URL: http://download.microsoft.com/download/7/A/1/7A1C88D7-B91A-4114-AF8D-852B481D5E F7/Introducing%20System%20Center.doc. Accessed August 8, 2007.Habib, Irfan. “New Approaches to Linux Package Management.”Linux.com November 10, 2005. Available online. URL: http://www.linux.com/feature/49405. Accessed August 8, 2007.Honeycutt, Jerry. Microsoft Windows Desktop Deployment ResourceKit. Redmond, Wash.: Microsoft Press, 2003.Mehler, Kerrie, Cameron Fuller, and John Joyner. Microsoft SystemCenter Operations Manager 2007 Unleashed. Indianapolis:Sams, 2007.Wilson, Phil. The Definitive Guide to Windows Installer. Berkeley,Calif.: Apress, 2004.Intel CorporationIntel Corporation (NASDAQ symbol: INTC) is the world’slargest manufacturer of semiconductors or “computerchips.” The company was founded in 1968 as IntegratedElectronics Corporation by Robert Noyce and GordonMoore (see chip and Moore, Gordon).Until the early 1980s Intel made most of its revenuefrom manufacturing SRAM memory chips (see memory).When the Japanese had made significant inroads into thesemiconductor market, Intel turned to microprocessors,which it had introduced in 1971 and which formed thebasis for the development of the desktop or personal computer(see microprocessor and personal computer).During the 1980s, Intel 8086/8088 processors and theirsuccessors (286, 386, 486) and the associated chipsets werebeing used in the dominant “Wintel” (Microsoft Windowsplus Intel) PC architecture. By the middle of the 1990s,Intel dominated the microprocessor market with its Pentiumseries chips, overcoming a mathematical flaw in someof the latter.

intellectual property and computing 245CompetitionAround 2000, Intel’s dominance began to be challenged.The power of modern processors allowed for the developmentof lower-cost commodity PCs, and when Intel continuedits progression toward increased power, competitors,particularly AMD (see Advanced Micro Devices), wereable to gain greater market share with its less expensiveCPUs.In higher power chips (particularly dual- and multi-corechips with more than one processor), Intel seems to havethe edge in the middle of the first decade of the new century,although AMD is coming on strong. Meanwhile Inteland Apple in 2006 made a deal to replace the PowerPC chipin the Macintosh with Intel chips.Intel has struggled with corporate reorganization andlower sales of chipsets and motherboards (even while continuingwith strong sales of its dual-core and quad-coreprocessors). After a decline of 42 percent from 2005 to2006, Intel’s net income increased to about $7 billion in2007. However, its workforce has continued to declinefrom 102,500 in mid-2006 to 86,300 in 2007. However,Intel is expecting to produce more quad-core processors,new laptop components (including flash memory insteadof hard drives), and other innovations in a very competitivemarket.Further ReadingColeman, Bob, and Logan Shrine. Losing Faith: How the Grove SurvivorsLed the Decline of Intel’s Corporate Culture. 2007.Colwell, Robert P. The Pentium Chronicles: The People, Passion, andPolitics Behind Intel’s Landmark Chips. Hoboken, N.J.: Wiley,2006.Grove, Andrew S. Only the Paranoid Survive: How to Exploit theCrisis Points That Challenge Every Company. New York: Dell,1996.Intel Corporation. Available online. URL: http://www.intel.com.Accessed September 23, 2007.intellectual property and computingIntellectual property can be defined as the rights the creatorof an original work (such as an invention or a book)has to control its reproduction or use. Developers of newcomputer hardware, software, and media content must beable to realize a return on their time and effort. This returnis threatened by the ease with which programs and data ondisks can be illicitly copied and redistributed. Several legalmechanisms can be used to deter such behavior.Legal Protection MechanismsIntellectual property represented by the design of new hardwarecan be protected through the patent system. A patentgives the inventor the exclusive right to sell or license theinvention for 20 years after the date of filing. The basicrequirements for a device to be patentable are that it representsan actual physical device or process and that it besufficiently original and useful. A mere idea for a device,a mathematical formula, or a law of nature is not patentablein itself. In computing, a patent can be given for anactual physical device that meets the originality and usefulnessrequirements. Software that works with that device tocontrol a physical process can be part of the patent, but analgorithm is not patentable by itself.In practice, however, the situation is much murkierand more problematic. Patents are viewed as a key strategicresource (and financial asset) by companies such asIBM (which holds 40,000 patents and earns $1 billion ayear by licensing them), and in the decade between 1995and 2005 the annual number of patent applications filedrose 73 percent to 409,532. This has led to a considerablebacklog in the Patent Office, and critics suggest that manypatents are granted without being properly examined,such as for the existence of “prior art” (previous uses ofsimilar technology).Large companies often complain that so-called patenttrollers obtain patents that may be relevant enough to causeinfringement or invalidate a later patent, and then threatenthe company with litigation if they are not paid. (Smallpatent holders in turn complain that large companies sometimesignore or underpay them because they assume thatthe patent holder cannot afford litigation.) Many companies,including eBay, Research in Motion (maker of theBlackberry PDA), and Microsoft have been embroiled inpatent suits.Major computer companies such as Google, IBM, andApple are supporting the Patent Reform Act of 2007. Thelaw would tighten the standards for getting a patent andmake it easier to challenge the patent later.As of mid-2008 the bill remained stalled in the Senate.Meanwhile, a federal court had overturned new patent regulationsthat sought to streamline the application processby reducing the amount of supporting materials submitted.Because of these restrictions, most software is protectedby copyright rather than by patent. A computer program isconsidered to be a written work akin to a book. (After all,a computer program can be thought of as a special type ofnarrative description of a process. When compiled into executablecode and run on a suitable computer, a program hasthe ability to physically carry out the process it describes.)Like other written works, a program has to be sufficientlyoriginal. Once copyrighted, protection lasts for thelife of the author (programmer) plus 70 years. (Works madefor hire are covered for 95 years from first publication or120 years from creation.) Given the pace of change in computing,such terms are close to “forever.” While not strictlynecessary, registration of the work with the U.S. CopyrightOffice and the inclusion of a copyright statement serve aseffective legal notice and prevent infringers from claimingthat they did not know the work was copyrighted.Content (that is, text or multimedia materials) presentedin a computer medium can be copyrighted in the same wayas its traditional printed counterpart. However, in 1996 theU.S. Supreme Court declared that a program’s user interfaceas such could not be copyrighted (see Lotus DevelopmentCorp. v. Borland International, U.S. 94-2003).Computer programs have also received protectionas trade secrets. Under the Uniform Trade Secrets Act, asadopted in many states, a program can be considered atrade secret if gaining economic value from it depends upon

246 internationalization and localizationit not being generally known to competitors, and that “reasonableeffort” is undertaken to maintain its secrecy. Thefamiliar confidentiality and non-disclosure agreementssigned by many employees of technical firms are used toenforce such secrecy.First Amendment IssuesIn a few cases the government itself has sought to limitaccess to software, citing national security. In the 1996 caseof Bernstein v. U.S., however, the courts ultimately ruledthat computer program code was a form of writing protectedby the First Amendment, so government agenciesseeking to prevent the spread of strong encryption softwarecould not prevent its publication.However, First Amendment arguments have been lesseffective in challenging private software protection mechanisms.In 2001 a U.S. District judge ruled that PrincetonUniversity computer scientist Edward Felten and his colleagueshad no legal basis to challenge provisions of theDigital Millennium Copyright Act (DMCA). The scientistshad claimed that a letter from the Recording Industry Associationof America (RIAA) had cast a “chilling effect” ontheir research into DVD-protection software by threateningthem with legal action if they published academic papersabout copy protection software used by online music services.The RIAA had withdrawn its letter, and the courtsruled there was no longer anything to sue about. Critics ofthe decision claim that it still leaves the academics in a sortof legal limbo since there is no guarantee that they wouldnot be sued if they published something.In another widely watched case the U.S. Court ofAppeals in New York affirmed a ruling that Eric Corley,editor of the hacker magazine 2600 could not publish thecode for DeCSS, a program that would allow users to readencrypted DVD disks, bypassing publisher’s restrictions.The Court said that the DMCA did not infringe upon FirstAmendment rights. This decision would appear to conflictwith Bernstein, although the latter has to do with governmentcensorship, not copyright. The Supreme Court islikely to hear one or more computer-related copyright casesin the years to come.Fair Use and Copy ProtectionAlthough the purchase of software may look like a simpletransfer of ownership, most software is accompanied by alicense that actually grants only the right to use the programunder certain conditions. For example, users are typicallynot allowed to make copies of the program and runthe program on more than one computer (unless the licenseis specifically for multiple uses). However, as part of “fairuse” users are allowed to make an archival or backup copyto guard against damage to the physical media.Until the 1990s, it was typical for many programs (particularlygames) to be physically protected against copying(see copy protection). Talented hackers or “softwarepirates” are usually able to defeat such measures, and“bootleg” copies of programs outnumber legitimate copiesin some Asian markets, for example (see software piracyand counterfeiting). Copy protection and/or encryptionis also typically used for some multimedia products such asDVD movies.Challenges of New MediaBy the mid-2000 decade, the biggest intellectual propertybattles were not about esoteric program codes but ratherrevolved around how to satisfy the ordinary home consumer’sappetite for music and video while preserving producers’revenues. Increasingly, music and even video is beingdownloaded rather than being bought in commercial packagingat the local store.In the Sony v. Universal case (1984) the Supreme Courtruled that manufacturers of devices such as VCRs werenot liable for their misuse if there were “substantial noninfringinguses”—such as someone making a copy of legallypossessed media for their own use. However, in 2005 theSupreme Court ruled that Grokster, a decentralized filesharingservice, could be held liable for the distribution ofillegally copied media if it “actively induced” such copying.By 2006 media industry lobbyists (particularly theRecording Industry Institute of America, or RIAA) werepromoting a number of bills in Congress that would furtherrestrict consumers’ rights to use media. Such measuresmight include requiring that devices be able to detect“flagged” media and refuse to copy it (see digital rightsmanagement), as well as adding stricter provisions to theDigital Millennium Copyright Act (DMCA). These measuresare opposed by cyber-libertarian groups such as theElectronic Frontier Foundation and consumer groups suchas the Home Recording Rights Coalition.Further ReadingChabrow, Eric. “The U.S. Patent System in Crisis.” Information-Week, February 20, 2006. Available online. URL: http://www.informationweek.com/story/showArticle.jhtml?articleID=180204145. Accessed August 12, 2007.Electronic Frontier Foundation. “Unintended Consequences: SevenYears under the DMCA.” April 2006. Available online. URL:http://www.eff.org/IP/DMCA/unintended_consequences.php.Accessed August 8, 2007.Gilbert, Jill. The Entrepreneur’s Guide to Patents, Copyrights, Trademarks,Trade Secrets & Licensing. New York: Berkley Books,2004.Home Recording Rights Coalition. Available online. URL: http://www.hrrc.org/. Accessed August 8, 2007.“Intellectual Property Law News.” FindLaw. Available online.URL: http://news.findlaw.com/legalnews/scitech/ip/. AccessedAugust 8, 2007.Klemens, Ben. Math You Can’t Use: Patents, Copyright, and Software.Washington, D.C.: Brookings Institution, 2006.LaPlante, Alice. “Media Distribution Rights: Here Come the Judges(and Congress).” InformationWeek, June 29, 2006. Availableonline. URL: http://www.informationweek.com/story/show-Article.jhtml?articleID=189700173. Accessed August 8, 2007.Wilson, Lee. Fair Use, Free Use, and Use by Permission: How to HandleCopyrights in All Media. New York: Allworth Press, 2005.internationalization and localizationInternationalization and localization are ways to adaptcomputer software (often created in the United States orEurope) to other languages and cultures. The abbreviations

Internet 247I18n and L10n are sometimes used for internationalizationand localization, respectively (the numbers in each wordrefer to the number of letters in the alphabet between theletters). The two processes are complementary.Internationalization involves designing programs sothey will be as easy as possible to adapt to a variety of culturalsettings. For example, the Unicode character set ispreferred because it can accommodate most of the world’salphabets and many other characters. Program code canalso be modularized such that date, time, and other formatsfor different countries can be loaded in and used as desired.Localization involves changing a number of aspectsof a software product (including user interface elementsand online help) to reflect the language and culture of theintended market. Some of this is fairly straightforward: formatsfor numbers, currency, date, and time; text collationand sorting order; and use of the keyboard (including specialkeys). To the extent the program has been appropriatelygeneralized (internationalized), it becomes easier to localizeit for each setting.Other aspects of localization can be subtler. Icons, forexample, may have to be changed because their supposedly“universal” meaning would not translate well into the localculture. Documentation may have to change wording toavoid conveying ideas that may be confusing or even offensive.Even more substantial localization may be required ifthe target environment (such as the education system) issubstantially different from that in the country where thesoftware was written. Generally this cannot be done automatically:the program must be reviewed by someone whois knowledgeable about the target language or culture.Further ReadingEsselink, Bert. A Practical Guide to Localization. Philadelphia: JohnBenjamins Publisher, 2000.Internationalization (I18n) Activity. World Wide Web Consortium.Available online. URL: http://www.w3.org/International/.Accessed September 23, 2007.Smith-Ferrier, Guy. .NET Internationalization: The Developer’sGuide to Building Global Windows and Web Applications. UpperSaddle River, N.J.: Addison-Wesley, 2007.InternetThe Internet is the worldwide network of all computers (ornetworks of computers) that communicate using a particularprotocol for routing data from one computer to another(see tcp/ip). As long as the programs they run follow therules of the protocol, the computers can be connected bya variety of physical means including ordinary and specialphone lines, cable, fiber optics, and even wireless or satellitetransmission.History and DevelopmentThe Internet’s origins can be traced to a project sponsoredby the U.S. Defense Department. Its purpose was to finda way to connect key military computers (such as thosecontrolling air defense radar and interceptor systems). Sucha system would require a great deal of redundancy, routingcommunications around installations that had beendestroyed by enemy nuclear weapons. The solution wasto break data up into individually addressed packets thatcould be dispatched by routing software that could findwhatever route to the destination was viable or most efficient.At the destination, packets would be reassembledinto messages or data files.By the early 1970s, a number of research institutionsincluding the pioneer networking firm Bolt Beranek andNewman (BBN), Stanford Research Institute (SRI), CarnegieMellon University, and the University of California at Berkeleywere connected to the government-funded and administeredARPANET (named for the Defense Department’sAdvanced Research Projects Agency). Gradually, as use ofthe ARPANET’s protocol spread, gateways were created toconnect it to other networks such as the National ScienceFoundation’s NSFnet. The growth of the network was alsospurred by the creation of useful applications includinge-mail and Usenet, a sort of bulletin-board service (see theApplications section below).Meanwhile, a completely different world of online networkingarose during the 1980s in the form of local bulletinboards, often connected using a store-and-forward systemcalled FidoNet, and proprietary online services such asCompuServe and America On-line. At first there were fewconnections between these networks and the ARPANET,which had evolved into a general-purpose network for theacademic community under the rubric of NSFnet. (It waspossible to send e-mail between some networks using specialgateways, but a number of different kinds of addresssyntax had to be used.)In the 1990s, the NSFnet was essentially privatized,passing from government administration to a corporationthat assigned domain names (see domain name system).However, the impetus that brought the Internet into thedaily consciousness of more and more people was the developmentof the World Wide Web by Tim Berners-Lee at theEuropean particle research laboratory CERN (see Berners-Lee, Tim and world wide web). With a standard way todisplay and link text (and the addition of graphics and multimediaby the mid-1990s), the Web is the Internet as far asmost users are concerned (see Web browser). What hadbeen a network for academics and adventurous professionalsbecame a mainstream medium by the end of the decade(see also e-commerce).ApplicationsA number of applications are (or have been) important contributorsto the utility and popularity of the Internet.• E-mail was one of the earliest applications on theancestral ARPANET and remains the single most popularInternet application. Standard e-mail using SMTP(Simple Mail Transport Protocol) has been implementedfor virtually every platform and operating system.In most cases once a user has entered a person’se-mail address into the “address book,” e-mail can besent with a few clicks of the mouse. While failure ofthe outgoing or destination mail server can still block

248 Internettransmission of a message, e-mail today has a highdegree of reliability (see e-mail).• Netnews (also called Usenet, for UNIX User Network)is in effect the world’s largest computer bulletinboard. It began in 1979, when Duke Universityand the University of North Carolina set up a simplemechanism for “posting” text files that could be readby other users. Today there are tens of thousands oftopical “newsgroups” and millions of messages (calledarticles). Although still impressive in its quantity ofcontent, many Web users now rely more on discussionforums based on Web pages (see netnews andnewsgroups).• Ftp (File Transport Protocol) enables the transfer ofone or more files between any two machines connectedto the Internet. This method of file transferhas been largely supplanted by the use of downloadlinks on Web pages, except for high-volume applications(where an ftp server is often operated “behindthe scenes” of a Web link). FTP is also used by Webdevelopers to upload files to a Web site (see filetransfer protocols).• Telnet is another fundamental service that broughtthe Internet much of its early utility. Telnet allows auser at one computer to log into another machine andrun a program there. This provided an early means forusers at PCs or workstations to, for example, accessthe Library of Congress catalog online. However, ifprogram and file permissions are not set properly onthe “host” system, telnet can cause security vulnerabilities.The telnet user is also vulnerable to havingIDs and passwords stolen, since these are transmittedas clear (unencrypted) text. As a result, some onlinesites that once supported telnet access now limitaccess to Web-based forms. (Another alternative is touse a program called “secure shell” or ssh, or to use atelnet client that supports encryption.)• gopher was developed at the University of Minnesotaand named for its mascot. Gopher is a system of serversthat organize documents or other files througha hierarchy of menus that can be browsed by theremote user. Gopher became very popular in the late1980s, only to be almost completely supplanted bythe more versatile World Wide Web.• WAIS (Wide Area Information Service) is a gatewaythat allows databases to be searched over the Internet.WAIS provided a relatively easy way to bringlarge data resources online. It, too, has largely beenreplaced by Web-based database services.• The World Wide Web as mentioned above, is nowthe main means for displaying and transferring informationof all kinds over the Internet. Its flexibility,relative ease of use, and ubiquity (with Web browsersavailable for virtually all platforms) has caused it tosubsume most earlier services. The utility of the Webhas been further enhanced by the development ofmany search engines that vary in thoroughness andsophistication (see World Wide Web and searchengine).• Streaming Media protocols allow for a flow of videoand/or audio content to users. Player applications forWindows and other operating systems, and growinguse of high-speed consumer Internet connections (seebroadband) have made it possible to present “live”TV and radio shows over the Internet.• E-commerce, having boomed in the late 1990s andcrashed in the early 2000s, continued to grow andproliferate later in the decade, finding new marketsand applications and spreading into the developingworld (see e-commerce).• Blogs and other forms of online writing have becomeprevalent among people ranging from elementaryschool students to corporate CEOs (see blogs andblogging).• Social networking sites such as MySpace and Facebookare also very popular, particularly among youngpeople (see social networking).• Wikis have become an important way to share andbuild on knowledge bases (see wikis and Wikipedia).• The integration of the Internet with traditional channelsof communications is proceeding rapidly (seepodcasting, Internet radio, and VoIP).Even as it begins to level off in the United States, worldwideInternet usage continues to grow rapidly. Asia now hasmore than twice as many users as North America, althoughthe latter still has more than five times the penetration(percentage of population).In the United States more than half of Internet usershave high-speed Internet connections (see broadband), andthe trend in other developed countries is similar. Broadbandis both required by and contributes to the appetite ofWeb users for music, streaming video, and other rich mediacontent (see streaming and music and video distribution,online).Now in its fourth decade, the Internet is not withoutdaunting challenges. A major one is security—see computercrime and security, computer virus, cyberterrorism,and information warfare. Users also wantprotection from privacy abusers and online predators (seeprivacy in the digital age, identity theft, phishingand spoofing, and cyberstalking and harassment).For other issues and challenges involving the Internet,see censorship and the Internet, Internet architectureand governance, Internet access policy, anddigital divide.In the longer term what we call the Internet today islikely to become so ubiquitous that people will no longerthink of it as a separate system or entity. Household appliances,cars, cell phones, televisions, and virtually everyother device used in daily life will communicate with otherdevices and with control systems using Internet protocols.

Internet applications programming 249In effect, people may eventually live “inside” a World WideWeb.Further ReadingHafner, Katie, and Matthew Lyon. Where Wizards Stay Up Late: TheOrigins of the Internet. New York: Simon & Schuster, 1996.Internet Society. Available online. URL: http://www.isoc.org.Accessed August 8, 2007.Internet World Stats. Available online. URL: http://www.internetworldstats.com/stats.htm. Accessed August 8, 2007.Okin, J. R. The Internet Revolution: The Not-for-Dummies Guide tothe History, Technology, and Use of the Internet. Winter Harbor,Me.: Ironbound Press, 2005.Segaller, Stephen. Nerds 2.0.1: A Brief History of the Internet. NewYork: TV Books, 1998.Zakon, Robert H. “Hobbes’ Internet Timeline v8.2.” Availableonline. URL: http://www.zakon.org/robert/internet/timeline/.Accessed August 8, 2007.Internet applications programmingThe growth of the Internet and its centrality in business,education, and other fields has led many programmersto specialize in Internet-related applications. These caninclude the following:• low-level infrastructure (networking [wired and wireless],routing, encryption support, and so on)• Web servers and related software• e-commerce infrastructure (see e-commerce)• interfacing with databases• data analysis and extraction (see data mining)• support for searching (see search engine)• autonomous software to navigate the net (see softwareagent)• Internet-based communications (see texting andinstant messaging and VoIP)• systems to deliver text and media (see streaming,podcasting, rss)• support for collaborative use of the Internet (seeblogs and blogging, social networking, andwikis and Wikipedia)• security software (firewalls, intrusion analysis, etc.)Internet applications programmers use a variety of languagesand other programming tools (often in combination)to implement these applications. Some of the mostcommon are:• C++ is generally used for fundamental applications,particularly those that must work at the system leveland for which speed and efficiency are prerequisites.Examples would include Web servers and browsersand some browser plug-ins (see C++).• Java has largely supplanted C++ as a general-purposelanguage for programming small applications(“applets”) that are hosted by Web sites and run onthe user’s browser. With a syntax that differs in only afew respects from C++, Java can also be used to writestandalone applications (see Java).• HTML is not really a full-fledged programming language,but it defines the layout and formatting of Webpages, as well as providing for hyperlinks and theembedding of applications. In many cases, HTML nolonger has to be coded directly but can be generatedfrom word processor-like page design programs (seedntml, html, and xhtml).• Extensible markup language (see xml) has becomethe preferred format for structuring a variety of databoth for automatic processing (see semantic Web)and for feeding dynamic Web pages (see Ajax).• Scripting languages are an important tool for Internetand Web development. CGI (Common GatewayInterface) is a facility that allows scripts to controlthe interaction between HTML forms on a Web pageand other programs such as databases (see cgi).CGI scripts are written in scripting languages (seeJavaScript, Perl, php, Python, and scripting languages).Use of CGI is being gradually supplantedby applets written in Java as well as other scriptinglanguages such as JavaScript and VBScript.• Active Server Pages (ASP) is a facility that uses WindowsActiveX components to process scripts createdin Visual Basic, which in turn create HTML pages “onthe fly” and send them to the user’s Web browser.• microsoft’s recent .NET initiative represents anattempt to integrate Internet connectivity and distributedoperation into the programming framework forall major languages.• Similar technologies are available for other platformssuch as Linux (see Ajax and document objectmodel)TrendsExperienced programmers will continue to be needed forcreating and extending the infrastructure for the Internetand Web and for providing increasingly powerful and easyto-usetools for developing Web sites. However, the widevariety of tools now available means that people with lessexperience will be able to design and implement attractiveand effective Web pages, plugging in functionality suchas online shopping, conferencing, and site-specific searchengines. If web development follows the same course astraditional programming, predictions that specialized programmerswill no longer be needed will prove premature.At the same time, generalist web developers will be able todo more.Further ReadingAndersson, Eve, Philip Greenspun, and Andrew Grumet. SoftwareEngineering for Internet Applications. Cambridge, Mass.: MITPress, 2006.Connolly, Randy. Core Internet Application Development with ASP.NET 2.0. Upper Saddle River, N.J.: Prentice Hall, 2007.

250 Internet censorshipDunaev, Sergei. Advanced Internet Programming: Technologies &Applications. Hingham, Mass.: Charles River Media, 2001.HTML/Web Programming Resources. Available online. URL: http://www.sandhills.cc.nc.us/html.html. Accessed August 8, 2007.Moore, Dana, Raymond Budd, and Edward Benson. ProfessionalRich Internet Applications: AJAX and Beyond. Indianapolis:Wrox, 2007.Web Programming Resources. Available online. URL: http://www.webreference.com/programming/. Accessed August 8, 2007.Internet censorship See censorship and theInternet.Internet cafés and “hot spots”Internet cafés (also called cyber cafés) are public placeswhere computers are connected to the Internet and availablefor use for a fee by the hour or minute. Many Internetcafés also sell coffee and food. Combining the social ambienceof a traditional coffee shop and the attraction of theInternet, many Internet cafés acquire a regular clientelefrom students to adults.These venues appeared first in the mid-1990s and spreadrapidly as their popularity grew. While the most commonactivities at most Internet cafés are to check e-mail, sendtext messages, or browse the Web, some locations specializein gaming (see online games), providing more powerfulmachines running games over a local network. Suchgaming centers have been particularly popular in Asia.Internet cafés have grown most rapidly in countries thatare becoming more urban and industrial but where manypeople cannot yet afford their own computers. The moststriking example is China, which had 113,000 Internet cafésin as of 2007. In keeping with its strict policies, however,the Chinese government closely monitors activity at Internetcafés (see censorship and the Internet).Hot SpotsThe number of dedicated Internet cafés in the UnitedStates and many other highly developed countries has beendeclining in recent years. This is largely due to the growingnumber of people who connect to the Internet through theirown laptops and other mobile devices (see pda and smartphone).Thus many locations, including coffee chains suchas Starbucks, do not provide machines, but simply offerwireless Internet access (see Wireless and mobile computing).Areas where one can make such a wireless connectionare called “hot spots.” Today virtually all majorhotels and airports provide hot spots; there is normally afee for access as with Internet cafés. (The fee is collected byrouting all access through a portal.) However, a number ofvenues offer free Wifi access.Users of Internet cafés or hot spots should be awarethat they are sharing an ad hoc network with strangers andmay be exposed to malicious software. Passwords or othersensitive data may be “sniffed” using special software. Itis therefore generally a good idea not to conduct financialtransactions or otherwise send sensitive information whenconnected to such venues, unless one has provided forencryption or can access a virtual private network. Additionally,users connecting their own machines to a hot spotshould have up-to-date firewall and antivirus software.Further ReadingBradley, Tony, and Becky Waring. “Complete Guide to Wi-Fi Security.”Available online. URL: http://www.jiwire.com/wi-fisecurity-traveler-hotspot-1.htm.Accessed September 9, 2007.Café Touch. Available online. URL: http://www.cafetouch.com/.Accessed September 9, 2007.Cyber cafés [directory]. Available online. URL: http://www.cybercafes.com/. Accessed September 9, 2007.Internet Café Guide. Available online. URL: http://www.internet-cafe-guide.com/. Accessed September 9, 2007.Wi-Fi Hotspot Finder. Available online. URL: http://www.jiwire.com/search-hotspot-locations.htm. Accessed September 9,2007.Internet cafes are particularly common in countries such as China,where Internet access is still relatively rare in homes. In many casessuch facilities have given way to simple “hot spots,” where userscan wirelessly connect their own laptops or PDAs. (Qin Ying/Panorama/The Image Works)Internet organization and governanceThe Internet is remarkable as a modern institution in that,while the technology was developed with considerable governmentfunding, the Net as we know it today is remarkablyfree of externally imposed authority or regulation. This isin sharp contrast with earlier communications technologiessuch as the telegraph and telephone, which were generallytightly regulated or even run by a government departmentsuch as the Post Office. In part this was due to the complexityof the technology and the fact that many political leadershad little familiarity with it and its implications. (Also, thespeed of growth has been overwhelming in recent years,considering that the World Wide Web in its modern formwas scarcely a decade and a half old as of 2008.)Institutions of Self-GovernanceWhile the Internet is not rigidly controlled, the need forinteroperability and orderly advances in technology hasled to the emergence of several organizations that provide

Internet service provider 251standards and guidance. The most important of these isthe World Wide Web Consortium (W3C). Other technicalorganizations include the Internet Engineering Task Force(IETF) and the Internet Corporation for Assigned Namesand Numbers (ICANN), the latter of which administers thedomain system (seen domain name system). The domainregistries in turn are run by many different institutions andagencies.Growing Role of Governments?Many of the key innovators of the Internet have looselyshared a somewhat anarchic or libertarian viewpoint, andreinforced it with the claim that the decentralized architectureof the Internet itself resists imposition of rules fromoutside. (Thus the saying, “the Internet sees censorship as afailure and routes around it.”)However, recently some writers such as Lawrence Lessigof Stanford Law School have called for a reappraisal.Lessig argues that the Internet is far from ungovernableand that indeed such an important institution must be regulated.The question is how to regulate it wisely, shapingits architecture to support freedom, democracy, and otherdesirable values.In 2003 and 2005, the United Nations brought togethermany government representatives who raised many issuesabout what they saw as inadequacies of the privately runInternet (for example, in the assigning of domain names)and a perceived bias toward American interests. TheUnited Nations has established an Information and CommunicationTechnologies (ICT) Task Force to carry onthese meetings, which will be called the Internet GovernanceForum (IGF). Other international institutions suchas the International Telecommunications Union (ITU)have sometimes come into conflict with the Internet’s selfgoverningbodies.Within the United States there continues to be strongresistance to imposing new regulations on the Internet, inpart because of fear of constricting one of the most importantand fastest growing sectors of the economy.The conflict between the Internet’s self-governingculture and the needs and desires of political institutionswill no doubt continue. Sometimes the conflict canbe very sharp, as with China’s blocking of Internet contentthat it finds objectionable (see censorship and theInternet). Other issues are perhaps deeper, such as thequestion of how to enforce criminal laws or economicregulations that were designed for a world made of brickand steel.Further ReadingGoldsmith, Jack, and Tim Wu. Who Controls the Internet? Illusionsof a Borderless World. New York: Oxford University Press,2006.Internet Governance Project. Available online. URL: http://www.internetgovernance.org/. Accessed September 23, 2007.Lessig, Lawrence. Code Version 2.0. New York: Basic Books, 2006.MacLean, Don, ed. Internet Governance: A Grand Collaboration.New York: United Nations ICT Task Force, 2004.World Wide Web Consortium. Available online. URL: http://www.w3.org/. Accessed September 23, 2007.Internet radioInternet radio is the provision of radio broadcast contentover the Internet (see streaming). Basically, the digitizedsound files of the broadcasts can be accessed and playedusing widely available software such as Windows MediaPlayer or RealPlayer. Internet radio began in the mid-1990s,and today an increasing number of broadcast stations areoffering their programming in this form, allowing them toreach audiences far beyond the reach of their signal. Somestations stream live (during the actual broadcast), whileothers make programs available for download. (For automaticdownloading of broadcasts, see podcasting). Thereare also “radio stations” that provide their content only viathe Internet. Internet radio should not be confused withsatellite or cable radio, which carry conventional radio signalsin real time.For the user, Internet radio expands the selection ofstations available from a few dozen over the air to hundredsor thousands. Potentially this allows for the supportof specialized stations that have been struggling for audiencesin traditional markets—examples might be stationsbroadcasting jazz or alternative music, political advocacy,or programming in less widely spoken languages.Of course there still remains the question of how commercialInternet radio can support itself. Many on-air stationssimply include their advertising in the Internet stream(although this can be sometimes ineffective if the ad referssolely to a local business). Some stations sell subscriptionsor charge a fee for each program.Regular radio stations must pay royalties to performerswhose music is played on the air. Until recently, such feeshave been minimal (or even ignored) for Internet radio. Amajor issue arose in 2007 when the U.S. Copyright RoyaltyBoard approved a steep increase in the royalties for musicon Internet radio. Many smaller Internet radio stations haveprotested that the increased fees would put them out ofbusiness as well as hurting many independent performerswho depend on this medium to get their work heard.However, a number of stations have been able to negotiatereductions or caps on these fees on an ad hoc basis.Further ReadingHeberlein, L. A. The Rough Guide to Internet Radio. London: RoughGuides, 2002.Hoeg, Wolfgang, and Thomas Lauterbach, eds. Digital AudioBroadcasting: Principles and Applications of Digital Radio. 2nded. New York: Wiley, 2003.Internet Radio Guide. Available online. URL: http://www.windowsmedia.com/Mediaguide/Radio. Accessed September23, 2007.Lee, Eric. How Internet Radio Can Change the World: An Activist’sHandbook. Lincoln, Nebr.: iUniverse, 2004.Web Radio [directory]. Available online. URL: http://www.radio-directory.com/. Accessed September 23, 2007.Internet service provider (ISP)An Internet service provider is any organization that providesaccess to the Internet. While nonprofit organizationssuch as universities and government agencies can be

252 interpreterconsidered to be ISPs, the term is generally applied to acommercial, fee-based service.Typically, a user is given an account that is accessed bylogging in through the operating system’s Internet connectionfacility by supplying a user ID and password. Once connected,the user can run Web browsers, e-mail clients, andother programs that are designed to work with an Internetconnection. Most ISPs now charge flat monthly fees rangingfrom $20 or so for dial-up access to around $40–$60for high-speed cable or DSL connections (see broadband).Some services such as America Online and CompuServeinclude ISP service as part of a package that also includessuch features as software libraries, discussion forums, andinstant messaging. Online services tend to be more expensivethan “no frills” ISP services.Most personal ISP accounts include a small allotment ofserver space that users can use to host their personal Webpages. There are generally extra charges for larger allotmentsof space, for sites that generate high traffic, and forcommercial sites. Business-oriented ISPs typically providea more generous starting allotment along with more extensivetechnical support and more reliable and higher-capacityservers that are managed 24 hours a day.The rapid growth in Internet use in the mid-1990sencouraged many would-be entrepreneurs to start ISPs. However,with so many providers entering the field and with theprice for basic Internet connections falling, it soon becameapparent that the survival prospects for “generic” ISPs wouldbe poor. People entering the business today strive to provideadded-value services such as superior Web page hostingfacilities, hosting blogs or wikis, or to focus on specializedservices for particularly industries (such as real estate).Today’s ISPs also face a variety of legal challenges,including customer privacy vs. the war on terrorism (seeprivacy in the digital age), responsibility for copyrightinfringement (see intellectual property and computing),and possible liability for online defamation, harassment,or worse (see cyberstalking and harassment.)Many earlier versions of the BASIC programming languagewere implemented as interpreters. Since an interpreteronly has to hold one program statement at a time inmemory, it could run on early microcomputers that had onlya few tens of thousands of bytes of system memory. However,interpreters run programs considerably more slowlythan a compiled program would run. One reason is that aninterpreter “throws away” each source code statement afterit interprets it. This means that if a statement runs repeatedly(see loop), it must be re-interpreted each time it runs.A compiler, on the other hand, would create only one setof machine code instructions for the loop and then moveon. Also, because a compiler keeps the entire program inmemory, it can analyze the relationship between multiplestatements and recognize ways to rearrange or substitutethem for greater efficiency.Interpretation can also be used to bridge differencesin hardware platforms. For example, in the UCSD Pascalsystem developed in the 1970s, an interpreter first translatesthe Pascal source code into a standardized “P-code”(pseudocode) for a generic processor called a P-machine. ToFurther ReadingBerkowitz, Howard C. Building Service Provider Networks. NewYork: Wiley, 2002.“Everything You Wanted to Know About Internet Service Providers.”Available online. URL: http://www.ispconsumerguide.com/. Accessed February 6, 2008.“ISP Liability.” BitLaw. Available online. URL: http://www.bitlaw.com/internet/isp.html. Accessed August 8, 2007.Nguyen, John V. Designing ISP Architectures. Upper Saddle River,N.J.: Prentice Hall, 2002.interpreterAn interpreter is a program that analyzes (parses) programmingcommands or statements in a high-level language (seeprogramming languages), creates equivalent executableinstructions in machine code (see assembler) and executesthem. An interpreter differs from a compiler in that the latterconverts the entire program to an executable file ratherthan processing and executing it a statement at a time (seecompiler).An interpreter scans a program code or command statement todetermine what each token (word or symbol) represents. Keywordssuch as PRINT are looked up in a dispatch table that containsinstructions for dealing with that function. Variables arelooked up in a symbol table that gives their current value. Valuesand operators make up expressions that are interpreted to yieldtheir final value. In this case the final value of 15 is given as datato the PRINT routine, which is executed to put the number 15 onthe screen.

iRobot Corporation 253run the program on a particular actual machine, a secondinterpreter translates the P-code into specific executablemachine instructions for that machine. Today Java uses asimilar idea. A Java programming system translates sourcecode into an intermediate “bytecode,” which is interpretedby a Java Virtual Machine, usually running with a Webbrowser.In practice, with today’s high-speed computers andgraphical operating environments, interpretative and compilationfunctions are often seamlessly integrated into aprogramming environment where code is checked for syntaxas it is entered, incrementally compiled (such that onlychanged code is recompiled), and the programmer receivesthe same kind of rapid feedback that was the hallmark ofthe early BASIC interpreters (see programming environment).Purely interpretive systems survive mainly in theform of text command processors for operating systems(see shell).Further ReadingCraig, Ian. The Interpretation of Object-Oriented Programming Languages.2nd ed. New York: Springer, 2002.Mack, Ronald. Writing Compilers and Interpreters: An AppliedApproach Using C++. 2nd ed. New York: Wiley, 2006.Watt, David, and Deryck Brown. Programming Language Processorsin Java: Compilers and Interpreters. Upper Saddle River, N.J.:Prentice Hall, 2000.iRobot CorporationiRobot is an innovative company based in Burlington, Massachusetts,that makes robots for home use (the Roombarobotic vacuum cleaner and its floor-washing cousinScooba) to military robots such as various PackBot modelsdesigned for reconnaissance, bomb disposal, and other dangeroustasks.iRobot was founded by robotics pioneer Rodney Brooksof MIT’s Artificial Intelligence Lab (see Brooks, Rodney)and two former MIT students, Helen Greiner and ColinAngle. The company was founded in 1991 and incorporatedin 2000. Its first product was My Real Baby, a realistic (andcomplicated) animated doll that proved to be too expensivefor the toy market. Roomba, on the other hand, wasreleased in 2002 and has met with considerable success—2million units had been sold by May 2006. Besides Scooba,Roomba has been joined by Dirt Dog (a workshop cleanerand picker-upper) and Verro, a pool cleaner. iRobot has alsoproduced an educational/hobby robot called iRobot Create.iRobot has done considerable work for the military,based on work in the 1990s with robots that crawled orrolled on tanklike tracks and were equipped with graspingdevices and other attachments. The PackBot series comesin models adaptable to a variety of military tasks, and hasbeen used in Iraq and Afghanistan.In 2007 iRobot released a redesigned, more durableversion of Roomba. Meanwhile cofounder Colin Angle hassaid that the company is looking at many exciting futureapplications, including industrial cleaning, mining, and oilexploration. In the home, Roomba may be joined by outdoorrobots that can mow the lawn and trim the hedges.iRobot is a midsized company whose revenue has grownfrom $54.3 million in 2003 to $227 million in 2007, with agross profit of $82.6 million and 423 employees.Further ReadingHenderson, Harry. Modern Robotics: Building Versatile Machines.New York: Chelsea House, 2006.iRobot. Available online. URL: http://www.irobot.com. AccessedSeptember 23, 2007.Lombardi, Candace. “iRobot’s Angle on the Future: More Profit.”CNET News, August 23, 2007. Available online. URL:http://www.news.com/iRobots-Angle-on-the-future-Moreprofit/2008-11394_3-6204031.html.Accessed September 24,2007.Pereira, Joseph. “Natural Intelligence: Helen Greiner ThinksRobots Are Ready to Become Part of the Household.” WallStreet Journal Classroom Edition, October 2002. Availableonline. URL: http://www.wsjclassroomedition.com/archive/02oct/COVR_ROBOT.htm. Accessed September 24, 2007.Roush, Wade. “Will Home Robots Ever Clean Up?” TechnologyReview, March 3, 2006. Available online. URL: http://www.technologyreview.com/article/16542/. Accessed September24, 2007.

JJavaJava is a computer language similar in structure to C++.Although Java is a general-purpose programming language,it is most often used for creating applications to run on theInternet, such as Web servers. A special type of Java programcalled an applet can be linked into Web pages and runon the user’s Web browser (see applet).As an object-oriented language, Java uses classes thatprovide commonly needed functions including the creationof user interface objects such as windows and buttons (seeclass and object-oriented programming). A variety ofsets of classes (“class frameworks”) are available, such asthe AWT (Abstract Windowing Toolkit).are built. The AWT (Abstract Windowing Toolkit) is a set ofclasses that provide a graphical user interface.The program then declares a new class called Hello-World and specifies that it is built on (extends) the appletclass.Program StructureA Java program begins by importing or defining classes andusing them to create the objects needed for the program’sfunctions. Code statements then create the desired output orinteraction from the objects, such as drawing a picture or puttingtext in a window. Here is a simple Java applet program:import java.applet.Applet;import java.awt.Graphics;public class HelloWorld extends Applet {public void paint(Graphics g) {g.drawString(“Hello world!”, 50, 25);}}The first two lines import (bring in) standard classes.The applet class is the foundation on which applet programsAfter an embedded Java program (called an applet) is compiled, itsexecutable file (Javacode) is stored on the Web server, together withthe HTML file for the Web page to which the program is linked.254

Java 255Next is a declaration for a method (procedure for doingsomething) called paint. This method uses a graphics objectg that includes various capabilities for drawing things onthe screen. Finally, the program uses the graphic object’spredefined drawstring method to draw a string of text.To develop this program, the programmer compiles itwith the Java compiler. He or she then creates an HTMLpage that includes a tag that specifies that this code is to berun when the link is activated (see html).Development of JavaJava was created by James Gosling (1955– ). It began as anin-house project at Sun Microsystems to design a languagethat could be used to program “smart” consumer devicessuch as an interactive television. When this project wasabandoned, Gosling, Bill Joy, and other developers realizedthat the language could be adapted to the rapidly growingInternet. Developers of Web pages needed an easier way tocreate programs that could run when the page was accessedby a user. By implementing user controls on Web pages, thedesigners could give Web users the ability to interact onlinein much the same way they interact with objects on thescreen on a Macintosh or Windows PC.AdvantagesJava has largely fulfilled this promise for Web developers.C++ programmers have an easy learning curve to Java,since the two languages have very similar syntax and asimilar use of classes and other object-oriented features. Onthe other hand, programmers who don’t know C++ benefitfrom Java being more streamlined than C++. For example,Java avoids the necessity to use pointers (see pointers andindirection) and uses classes as the consistent buildingblock of program structure. Software powerhouses such asMicrosoft (until recently) and IBM have joined Sun in promotingJava.Another much-touted feature of Java is its platformindependence. The language itself is separate from the variousoperating system platforms. For each platform, a JavaVirtual Machine (JVM) is created, which interprets or compilesthe code generated by the Java compiler so it can runon that platform.For security, Java applets run within a “sandbox” orrestricted environment so the user is protected from maliciousJava programs. (For example, programs are notallowed to access the user’s disk or to connect the user’smachine to another Web site.) Web browsers can also be setto disable the running of Java applets.A Mature TechnologySun Java comes in two basic “flavors”: the Java 2 StandardEdition (J2SE) for Microsoft Windows, Sun (Solaris), andLinux, and the Enterprise Editions (J2EE), which includesfeatures needed in large, complex environments. Microsoftdeveloped its own dialect of Java for Windows, buteffectively abandoned it as a result of legal action by Sun.(Companies are allowed to develop Java implementationsfor various platforms, so long as they pass Sun’s strict validationprocess.)To run the Java applet, the user loads the linked page in the Webbrowser. The applet may then run automatically, or it may be connectedto a particular link or a control such as a button. Onceactivated, the applet is downloaded by the Web browser, which thenruns its Javacode using a module called a Java Virtual Machine(JVM). There is a separate JVM for each type of computer system.Java has paid particular attention to building reusablesoftware components. “JavaBeans” package a number ofrelated objects (classes) into a unit that can be accessedthrough a standard set of methods and automatically queriedfor information about their contents.Today powerful and well-documented Java programminginterfaces are available for working with Web services.While client-side Java applets run in the Web browser, JavaServer Pages (JSPs) embed code in an HTML page. The codeis compiled into a server-side application or “servlet.” XMLprocessing and database access is provided through the JavaAPI for XML (JAX).Java has largely fulfilled its promise of bringing mainstreamobject-oriented programming to a wide variety ofplatforms. The language is now often taught as a first languageinstead of C or C++. However, the idea of a singledominant language seems to be no longer applicable in therapidly evolving world of software development.

256 JavaScriptIn 2006 Sun Microsystems announced that it wouldmake Java’s source code freely available (see open source).In part this may be an attempt to maintain Java’s positionamong programmers, some of whom have shifted theirattention from Java to Microsoft’s own offshoot of C++ (seec#). However, Java’s greatest challenge seems to be in theWeb programming area, where it faces increasing competitionfrom more agile languages (see, for example, Ruby) aswell as a variety of scripting languages that may be easier tolearn and quicker to use for many applications.Further ReadingArnold, Ken, James Golsing, and David Holmes. The Java ProgrammingLanguage. 4th ed. Upper Saddle River, N.J.: PrenticeHall, 2005.Burd, Barry. Beginning Programming with Java for Dummies. 2nd ed.Hoboken, NJ: Wiley, 2005.Gosling, James. “Is Java Getting Better with Age?” [interview].Cnet News. Available online. URL: http://news.com.com/2008-7345_3-6022062.html. Accessed April 10, 2007.Krill, Paul. “Java Facing Pressure from Dynamic Languages.” Info-World, March 25, 2006. Available online. URL: http://www.infoworld.com/article/06/03/25/76803_HNjavapressure_1.html. Accessed April 10, 2007.McGovern, James, et al. Java Web Services Architecture. San Francisco:Morgan Kaufmann, 2003.Schildt, Herbert. Swing: A Beginner’s Guide. New York: McGraw-Hill, 2007.JavaScriptJavaScript is one of several popular languages that canenable Web pages to interact with users more quickly andefficiently (see vbscript, php, and scripting languages).The language first appeared in the mid-1990s’ Netscape 2browser under the name LiveScript. Technically, JavaScriptis the Sun Microsystems trademark for its implementationof a standard called ECMAScript. Despite the name, Java-Script is not directly related to the Java programming language.In its early years JavaScript was perhaps a victim of itsown success. Having a relatively easy-to-use scripting languageprovided an easier way to add features such as 3Dbuttons and pop-up windows to formerly humdrum Webforms. However, as with an earlier generation’s fondnessfor multiple fonts, early JavaScript programmers were oftenprone to add unnecessary and confusing clutter to Webpages. Besides sometimes annoying users, early JavaScriptalso suffered from significant differences in how it wasimplemented by the major browsers. As a result, Netscapeusers were sometimes stymied by JavaScript written forMicrosoft Internet Explorer, and vice versa. Finally, browserflaws have sometimes allowed JavaScript to be used to compromisesecurity such as by installing malware-infested“browser helpers.” As a result, many security experts beganto recommend that users disable JavaScript execution intheir browsers.Using JavaScriptJavaScript syntax and language constructs are similar tothose of C, with the addition of basic object-oriented features(see object-oriented programming). The languageitself has no capabilities for manipulating the environment(such as input/output). Instead, JavaScript calls upon an“engine” written for each host environment (normally aWeb browser). The engine implements features designed tocontrol how a Web page interacts with the user, such as thedisplay of windows and controls such as menus, buttons, ortoolbars. JavaScript can also be used to validate a Web formin the browser before it is submitted to the server. In general,“browser side” JavaScript processing reduces the loadon Web servers while allowing pages to respond quickly,such as by changing graphics as the user’s mouse pointerpasses over parts of the page.The principal interface between JavaScript and HTMLpages is the Document Object Model (see html and documentobject model). A World Wide Web Consortium (W3C)standard defines the DOM functions, and most browsers nowconsistently support Levels 1 and 2 of these standards. However,there are many Web users who cannot run standardJavaScript, such as users with visual disabilities (see disabledpersons and computing), users of some mobile browsers(such as for PDAs or smart phones), or users who have simplydisabled JavaScript for security reasons. Therefore, whenJavaScript is used for essential page functions (such as formprocessing), the developer should provide an alternative wayfor the user to perform the relevant task. (In the case of disabledusers, this may be a legal requirement.)Traditionally, JavaScript code has been embeddeddirectly in the containing HTML page, using tags like thefollowing:JavaScript Examplevar Name = prompt (“Enter yourname”,“”);alert(Name);When a JavaScript-enabled browser encounters thiscode, a text box will prompt the user for a name, which isstored in the variable Name and then displayed in an alertbox.In modern Web design to XHTML standards, however,just as formatting information is kept in a separate document(see cascading style sheets) JavaScript code is alsomaintained in a separate file and simply linked to withinthe HTML page:JavaScript can do much more than just display informationor process forms. JavaScript can access a variety

Jobs, Steven Paul 257of Web services (such as databases and search engines)and create custom pages in response to user actions (seealso Ajax). JavaScript can also be embedded in applicationsother than Web browsers: for example, the Adobe Acrobatand Reader and even operating-system scripting (such asMicrosoft’s JScript and JScript.NET). Although attention inrecent years seems to have shifted more to languages suchas PHP, JavaScript remains a widely used and powerful Webdesign tool.Further ReadingFlanagan, David. JavaScript: The Definitive Guide. 5th ed. Sebastapol,Calif.: O’Reilly, 2006.Heilmann, Christian. Beginning JavaScript with DOM Scripting andAjax. Berkeley, Calif.: APress, 2005.JavaScript at Webdeveloper.com. Available online. URL: http://www.webdeveloper.com/javascript/. Accessed September 24,2007.JavaScript.com: The Definitive JavaScript Resource. Availableonline. URL: http://www.javascript.com/. Accessed September24, 2007.Wilton, Paul, and Jeremy McPeak. Beginning JavaScript. 3rd ed.Indianapolis: Wiley, 2007.job control languageIn the early days of computing, data processing generallyhad to be done in batches. By modern standards the memorycapacity of the computer was very limited (see mainframe).Typically, programs had to be loaded one at a time frompunch cards or tape. The data to be processed by each programalso had to be made available by being mounted on atape drive or inserted as a stack of cards into the card reader(see punched cards and paper tape). After the programran, its output would consist of more data cards or tape,which might in turn be used as input for the next program.For example, a series of programs might be used toread employee time cards and calculate the payments dueafter various items of withholding. That data might in turnbe input into a program to print the payroll checks andanother program to print a summary report.In order for all this to work, the computer’s operatingsystem must be told which files (on which devices) are tobe used by the program, the memory partition in whichthe program is to be run, the device to which output willbe written or saved, and so on. This is done by giving thecomputer instructions in job control language (JCL). (Inthe punch card days, the JCL cards were put at the top ofthe deck before the cards with the instructions for the programitself.)For a simple example, we will use some elements of IBMMVS JCL. In this version of job control language the generalform for all statements is//name operation operands commentwhere name is a label that can be used to reference thestatement from elsewhere, operation indicates one of a setof defined JCL language commands, operand is a series ofvalues to be passed to the system, and comment is optionalexplanatory text.The three basic types of statement found in most jobcontrol languages are JOB, EXEC, and DD. The JOB statementidentifies the job and the user running it and sets upsome parameters to specify the handling of the job.//JOB,CLASSPROJ1,GROUP=J999996,USER=P999995,//PASSWORD=?This statement passes information to the system thatidentifies the job name, group as assigned by the facility,and user ID. The PASSWORD parameter is given a questionmark to indicate that it will be prompted for at the terminal.Other parameters can be used to specify such matters as theamount of computer time to be allocated to the job and theway in which any error messages will be displayed.The EXEC statement identifies the program to be run.Some systems can also have a library of stored JCL proceduresthat can also be specified in the EXEC statement.This means that frequently run jobs can be run withouthaving to specify all the details each time. An exampleEXEC statement is://Datasort EXEC BINSORT,BUFFER=256KHere the statement is labeled Datasort so it can be referencedfrom another part of the program. The procedure tobe executed is named BINSORT, and it is passed a parametercalled BUFFER with a value of 256K (presumably this is theamount of memory to be used to hold data to be sorted).One or more DD (Data Definition) statements are usedto specify sets (sources) of data to be used by the program.This includes a specification of the type (such as disk ortape) and format of the data. It also includes instructionsspecifying what is to happen to the data set. For example,the data set might be old (existing) or newly created by theprogram. It may also be temporary (possibly to be passedon to the next program) or permanent (“cataloged”).Since interactive, multitasking operating systems suchas Windows and UNIX are now the norm in most computing,JCL is used less frequently today. However, it is stillneeded in large computer installations running operatingsystems such as IBM MVS (see mainframe) and for somebatch processing of scientific or statistical programs (suchas in FORTRAN or SAS).Further ReadingBrown, Gary Deward. System 390 Job Control Language. 4th ed.New York: John Wiley, 1998.Malaga, Ernie, and Ted Holt. Complete CL: The Definitive ControlLanguage Programming Guide. 3rd ed. Carlsbad, Calif.: MidrangeComputing, 1999.Jobs, Steven Paul(1955– )AmericanEntrepreneurSteve Jobs was cofounder of Apple Computer and shapedthe development and marketing of its distinctive Macintoshpersonal computer (see Apple Corporation). Jobs showed

258 Jobs, Steven Paulan enthusiastic interest in electronics starting in his highschool years and gained experience through summer workat Hewlett-Packard, one of the dominant companies of theearly Silicon Valley. In 1974, he began to work for pioneervideo game designer Nolan Bushnell at Atari. He alsobecame a key member of the Homebrew Computer Club, agroup of hobbyists who designed their own microcomputersystems using early microprocessors.Meanwhile, Jobs’s friend Steve Wozniak had developedplans for a complete microcomputer system that could bebuilt using a single-board design and relatively simple circuits(see Wozniak, Steven). In it Jobs saw the potentialfor a standardized, commercially viable microcomputersystem. They formed a company called Apple Computer(named apparently for the vanished orchards of Silicon Valley)and built a prototype they called the Apple I. Althoughthey could only afford to build a few dozen of the machines,they made a favorable impression on the computer enthusiastcommunity. By 1977, they were marketing a more completeand refined version, the Apple II.Unlike kits that could be assembled only by experiencedhobbyists, the Apple II was ready to use “out of thebox.” It included a cassette tape recorder for storing programs.When connected to a monitor or an ordinary TV,the machine could create color graphics that were dazzlingcompared to the monochrome text displays of most computers.Users could buy additional memory (the first modelcame with only 4K of RAM) as well as cards that coulddrive devices such as printers or add other capabilities.The ability to run a program called VisiCalc (see spreadsheet)propelled the Apple II into the business world, andabout 2 million of the machines were eventually sold. In1982, when Time magazine featured the personal computeras its “man of the year,” Jobs’s picture appeared on thecover. As he relentlessly pushed Apple forward, supporterspointed to Jobs’s charismatic leadership, while detractorssaid that he could be ruthless when anyone disagreed withhis vision of the company’s future.However, 1982 also brought industry giant IBM into themarket. Its 16-bit computer was more powerful than theApple II, and IBM’s existing access to corporate purchasingdepartments resulted in the IBM PC and its “clones” quicklydominating the business market (see ibm pc).Jobs responded to this competition by designing a PCwith a radically different user interface, based largely onwork during the 1970s and the Xerox PARC laboratory.The first version, called the Lisa, featured a mouse-drivengraphical user interface that was much easier to use thanthe typed-in commands required by the Microsoft/IBMDOS. While the Lisa’s price tag of $10,000 kept it out of themainstream market, its successor, the Macintosh, attractedmillions of users, particularly in schools, although the IBMPC and its progeny continued to dominate the businessmarket (see Macintosh). Meanwhile, Jobs had recruitedJohn Sculley, former CEO of PepsiCo, to serve as Apple’sCEO.After a growing divergence with Sculley over managementstyle and Apple’s future priorities, Jobs left thecompany in 1985. Using the money from selling his Applestock, Jobs bought a controlling interests in Pixar, a graphicsstudio that had been spun off from LucasFilm. He alsofounded a company called NextStep. The company focusedon high-end graphics workstations that used a sophisticatedobject-oriented operating system. However, while itssoftware (particularly its development tools) was innovative,the company was unable to sell enough of its hardwareand closed that part of the business in 1993.In 1997, Jobs returned as CEO of Apple. By then thecompany was struggling to maintain market share for itsMacintosh line in a world that was firmly in the “Wintel”(Windows on Intel-based processors) camp. He had somesuccess in revitalizing Apple’s consumer product line withthe iMac, a colorful, slim version of the Macintosh. He alsofocused on development of the new Mac OS X, a blending ofthe power of UNIX with the ease-of-use of the traditionalMacintosh interface.Beyond the MacAt the beginning of the new century, Jobs and Apple madebold moves beyond the company’s traditional strengths.The Power PC chip in the Mac was phased out in favor ofIntel chips, the same hardware that runs Microsoft Windowsmachines. (Indeed, the Mac was also given a utilitythat allowed it to run Windows.) This potentially openedthe Mac to a much wider range of software.The biggest move, however, was into media, first withpowerful video-authoring software for home users as wellas professionals, then with the tiny iPod that redefined theportable media player (see music and video players, digital).At the same time, Apple entered the digital musicbusiness in a big way with the iTunes store (see music andvideo distribution, online). In 2007 Apple charged intothe mobile communications market (see smartphone) withthe innovative if expensive iPhone. So far the market hasresponded positively to Jobs’s initiatives, with Apple stockincreasing in value more than 10 times between 2003 and2006.While Jobs is brash and unconventional (reflecting hiscountercultural roots), critics have accused him of egotismand of having an overly aggressive (and abrasive) managerialstyle. Jobs has also been the subject of lingeringinvestigations into his receiving discounted Apple stockoptions, failing to report the resulting taxable income, andcorrespondingly overstating Apple’s earnings. In December2006 Apple’s internal investigation cleared Jobs ofresponsibility for these issues, and the options were neverexercised. Whatever the future brings, Steve Jobs has anassured place in the history of entrepreneurship and innovationin computing.Further Reading“Bill Gates and Steve Jobs” [on-stage interview]. All Things Digital,May 30, 2007. Available online. URL: http://d5.allthingsd.com/20070530/d5-gates-jobs-interview/. Accessed August 11,2007.Jobs, Steve. “Steve Jobs: Oral History” [interview]. April 20, 1995.Available online. URL: http://www.cwheroes.org/archives/histories/jobs.pdf. Accessed August 11, 2007.

journalism and computers 259Markoff, John. What the Dormouse Said: How the Sixties CountercultureShaped the Personal Computer Industry. New York:Penguin, 2005.Young, Jeffrey S., and William L. Simon. iCon: Steve Jobs, the GreatestSecond Act in the History of Business. Hoboken, N.J.: Wiley,2005.journalism and computersThe pervasive use of computers and the Internet haschanged the practice of journalism in many ways. Thisentry will focus on the general impact of technology on thecreation and dissemination of news content. For discussionof software used in the production of publications, seedesktop publishing, and word processing. For the rolethat journalism plays in the computer industry, see journalismand the computer industry.Research and NewsgatheringThe gathering of on-scene information at newsworthyevents began to change in the 1980s, when notebook-sizedportable computers became available. Instead of having to“file” stories with the newspaper by telegraph or phone, thereporter could write the piece and send it to the newspaper’scomputer using a phone connection (see modem) orlater, Internet-based e-mail.The ability of reporters (particularly investigative reporters)to do in-depth research has been greatly enhancedby the Internet. Traditionally, reporters looking for backgroundmaterial for an assignment could consult printedreference works, their publications’ archives of printed articles(the “morgue”), and various public records, usually inpaper form. This process was necessarily slow, and it wasdifficult to widen research to include a greater variety ofsources while still remaining timely.Today most publications produce and store their materialelectronically and make it available online. Reportersthus have virtually instant access to articles written by theircolleagues around the world. Instead of having to rely on afew press releases, position papers, or wire stories, reporterscan search the Internet to delve more deeply into theunderlying source material, such as original documents orstatistics. An increasing number of public records are alsoavailable online.Changing Standards and New ChallengesAfter being submitted electronically, reporters’ stories canbe edited, revised as necessary, and submitted to the computer-controlledtypesetting systems that have now becomestandard in most publications. Besides saving productioncosts, computer-based newspaper production also makes iteasier to make last-minute changes as well as to create specialeditions that include regional news.However, at the same time the greater use of informationtechnology has made print journalists more productive, ithas also contributed to trends that continue to challengethe viability of print journalism itself. The nature of theInternet poses new challenges to reporter-researchers. Theaccuracy of traditionally published books or articles isbacked implicitly by the reputation of the publisher as wellas that of the author. By offering a wide variety of materialsproduced outside the mainstream publishing process,often by unknown authors, the Internet can provide a muchgreater diversity of viewpoints (see also wikis and Wikipedig).The downside is that the reporter-researcher haslittle assurance of the veracity or accuracy of facts givenon unknown Web sites. This creates a greater burden offact checking in responsible journalism or, alternatively, arelaxation of the traditional standards. (The most famousexample of the latter is Matt Drudge, a self-made Internetbasedjournalist who sometimes dramatically “scooped” hismore plodding colleagues but did not adhere to the oldjournalistic standard of finding two independent sourcesfor each key fact.)The use of the Internet as both a research tool and amedium of publication is also bound up with the everacceleratingpace of the “news cycle,” or the time it takesfor a story to be disseminated and responded to. Broadcastjournalism with the advent of 24-hour news networks suchas CNN has steadily increased the pace of the broadcastnews cycle. Many newspapers and magazines have foundhaving Web sites to be a competitive necessity. The Internetpotentially combines the immediacy of broadcast journalismwith the ability to use text to convey information indepth. The organization of Web pages (see hypertext andhypermedia) avoids the physical limitations of the printedmedium.In addition to Web sites that mirror and expand thecontents of printed newspapers, a number of distinctiveInternet-only sites emerged in the mid to late 1990s. Examplesinclude salon.com, an “online newsmagazine” thatalso includes regular featured columnists and discussionforums. However, the downturn in the Internet-based economyin 2002 made the original idea of having free accesssupported by advertising less viable. Such sites are now tryingto convert to a subscription-based model similar to thatof print-based publications, but it is unclear whether theywill be able to attract enough paying subscribers.New Alternatives and New QuestionsThe Internet is rapidly changing not only how journalism isproduced, but how it is delivered—and indeed, the role andfuture of the profession itself. Broadcast journalism, alreadygreatly changed by the advent of cable TV networks in the1990s, has now found itself needing to deliver programsthrough new channels (see podcasting, Internet radio,and music and video distribution, online). With “broadcasts”available any time at user request, the news cycle hasessentially vanished into a 24/7 reality where wave uponwave of stories is constantly flowing and changing.The more profound change, though, is in who gets topractice and define journalism. Everyone it seems has somethingto say online (see blogs and blogging). Bloggerswho cover current events (especially politics) at their bestrepresent the latest incarnation of “citizen journalism” (seepolitical activism and the Internet). However, issues ofobjectivity (and the line between activist and journalist) havebeen raised, as has the question of what legal protections

260 journalism and the computer industryfor journalists should apply to bloggers and online newsreporters.In addition to blogs, photo and video sharing sites(see, for example, YouTube) now widely distribute material,often quite controversial, that might once have beenignored by mainstream media. For their part, many mainstreamjournalists now also maintain blogs through whichreaders can respond to stories of the day.At the same time, in an era when a stream of bothimages and the printed word is on tap 24 hours a day, printjournalism faces a shrinking market and the need to justifyitself to consumers. The industry has responded since the1970s by an increasing number of mergers of metropolitandaily newspapers as well as the merging of newspapers intobroader-based media companies. Many people have grownup with the daily routine of a newspaper at the breakfasttable, and there is still a cachet for prestigious publicationssuch as the New York Times and the Wall Street Journal.Futurists have predicted that newspapers might eventuallybe delivered to “electronic book” devices, perhaps througha wireless connection (see e-books and digital libraries).This might combine the immediacy of the Internet with thephysical convenience and portability of a newspaper.Further ReadingCornfield, Michael. “Buzz, Blogs, and Beyond: The Internet andthe National Discourse in the Fall of 2004.” Pew Center forInternet & American Life. Available online. URL: http://www.pewinternet.org/ppt/BUZZ_BLOGS__BEYOND_Final05-16-05.pdf. Accessed August 11, 2007.Daily KOS. Available online. URL: http://www.dailykos.com.Accessed August 11, 2007.Gillmor, Dan. We the Media: Grassroots Journalism by the People, forthe People. Sebastapol, Calif.: O’Reilly, 2004.Meyer, Philip. The Vanishing Newspaper: Saving Journalism in theInformation Age. Columbia, Mo.: University of Missouri Press,2004.Pew Center for Civic Journalism. Available online. URL: http://www.pewcenter.org. Accessed August 11, 2007.Quinn, Stephen, and Vincent Filak, eds. Convergent Journalism: AnIntroduction—Writing and Producing across Media. Burlington,Mass.: Focal Press, 2005.Salon.com. Available online. URL: http://www.salon.com. AccessedAugust 1, 2007.Slate.com. Available online. URL: http://www.slate.com. AccessedAugust 1, 2007.Wulfemeyer, K. Tim. Online Newswriting. Ames, Iowa: BlackwellPublishing, 2006.journalism and the computer industryDevelopments in the computer industry and user communityhave been chronicled by a great variety of printed andon-line publications. As computer science began to emergeas a discipline in the late 1950s and 1960s, academicallyoriented groups such as the Association for ComputingMachinery (ACM) and Institute for Electrical and ElectronicsEngineers (IEEE) began to issue both general and special-interestjournals. Meanwhile, the computer industrydeveloped both computer science-oriented publications(such as the IBM Systems Journal) and independent industryperiodicals such as Datamation.The development of microcomputer systems in themid- to late-1970s was accompanied by a proliferation ofvaried and often feisty publications. Byte magazine, whichcoined the term PC in 1976, became a respected trade publicationthat introduced new technologies while showcasingwhat programmers could do with the early systems. Theweekly newspaper InfoWorld provided more immediate anddetailed coverage of industry developments, and was joinedby similar publications such as Information Week and Computerworld.Meanwhile, technically savvy programmers anddo-it-yourself engineers turned to such publications as theexotically named Dr. Dobbs’ Journal of Computer Calisthenicsand Orthodontia (eventually shortened to Dr. Dobbs’ Journal).Many groups of people who owned particular systems(see user groups) also published their own newsletterswith technical tips.The success of the IBM PC family of computers establisheda broad-based consumer computing market. Itwas accompanied by the success of PC Magazine, whichaddresses a wide spectrum of both general consumersand “power users.” As the revenue for the PC industrygrew in the 1990s, the trade publications grew fatter withadvertising. The popularity of the Internet and particularlythe World Wide Web in the latter part of the decadeprovided niches for a spate of new publications includingInternet World and Yahoo! Internet Life. At the same time,many traditional publications began to offer expandedcontent via Web sites. For example, Ziff Davis, publisherof PC Magazine and other computer magazines createdZDNet, which offered a large amount of content from themagazines plus expanded news and extensive sharewareand utility libraries.Like earlier technological developments, the PC andthe Internet have also spawned cultural expressions. Theculture growing around the Internet and a generation ofyoung programmers, artists, and writers saw expression inanother genre of publications, ranging from small, eclecticprinted or Web “zines” to the slick Wired magazine.From Print to OnlineMany of the pressures on mainstream journalism also applyto computer industry journalism. As computer hardwarebecame a commodity with lower profit margins, and withthe shift to e-commerce and online activity, many printmagazines have folded or at least shrunk. In 1998 the venerableByte became an online-only publication, a path finallyfollowed by InfoWorld in 2007.Online sites such as ZDNET and CNET now carryin-depth news and product reviews. Slashdot (“New forNerds”) is particularly popular among programmers. Aswith mainstream journalism, blogs also play an importantpart in professional and industry journalism in the computingfield.Further ReadingCNET. Available online. ULR: http://www.cnet.com. AccessedAugust 11, 2007.“Computer Industry: Trade Magazines.” Yahoo.com. Availableonline. URL: http://dir.yahoo.com/Business_and_Economy/

Joy, Bill 261Business_to_Business/Computers/Industry_Information/Trade_Magazines/. Accessed August 11, 2007.“Tag: Computer Industry” [blogs]. Available online. URL: http://it.wordpress.com/tag/computer-industry. Accessed August11, 2007.“Top 100 Computer and Software Magazines.” Available online.URL: http://netvalley.com/top100mag.html. Accessed August11, 2007.ZDNET. Available online. URL: http://www.zdnet.com. AccessedAugust 11, 2007.Joy, Bill(1955– )AmericanSoftware Engineer, EntrepreneurBill Joy developed many of the key utilities used by usersand programmers on UNIX systems (see unix). He thenbecame one of the industry’s leading entrepreneurs andlater, a critic of some aspects of computer technology.As a graduate student in computer science and electricalengineering at the University of California at Berkeley inthe 1970s, Joy worked with UNIX designer Ken Thompson(1943– ) to add features such as virtual memory (paging)and TCP/IP networking support to the operating system(the latter work was sponsored by DARPA, the DefenseAdvanced Research Projects Agency). These developmenteventually led to the distribution of a distinctive version ofUNIX called Berkeley Software Distribution (BSD), whichrivaled the original version developed at AT&T’s Bell Laboratories.The BSD system also popularized features such asthe C shell (a command processor) and the text editors “ex”and “vi.” (See shell.)As opposed to the tightly controlled AT&T version,BSD UNIX development relied upon what would becomeknown as the open-source model of software development(see open-source movement). This encouraged programmersat many installations to create new utilities for theoperating system, which would then be reviewed and integratedby Joy and his colleagues. BSD UNIX gained industryacceptance and was adopted by the Digital EquipmentCorporation (DEC), makers of the popular VAX series ofminicomputers.In 1982, Joy left UC Berkeley and co-founded Sun Microsystems,a company that became a leader in the manufactureof high-performance UNIX-based workstations forscientists, engineers, and other demanding users. Evenwhile becoming a corporate leader, he continued to refineUNIX operating system facilities, developing the NetworkFile System (NFS), which was then licensed for use not onlyon UNIX systems but on VMS, PC-DOS, and Macintoshsystems. Joy’s versatility also extended to hardware design,where he helped create the Sun SPARC reduced instructionset (RISC) microprocessor that gave Sun workstations muchof their power.In the early 1990s, Joy turned to the growing world ofInternet applications and embraced Java, a programminglanguage created by James Gosling (see Java). He developedspecifications, processor instruction sets, and marketingplans. Java became a very successful platform forbuilding applications to run on Web servers and browsersand to support the needs of e-commerce. As Sun’s chiefscientist since 1998, Joy has led the development of Jini,a facility that would allow not just PCs but many other“Java-enabled” devices such as appliances and cell phonesto communicate with one another.Recently, however, Joy has expressed serious misgivingsabout the future impact of artificial intelligence and relateddevelopments on the future of humanity. Joy remains proudof the achievements of a field to which he has contributedmuch. However, while rejecting the violent approachof extremists such as Unabomber Theodore Kaczynski,Joy points to the potentially devastating unforeseen consequencesof the rapidly developing capabilities of computers.Unlike his colleague Ray Kurzweil’s optimistic viewsabout the coexistence of humans and sentient machines,Joy points to the history of biological evolution and suggeststhat superior artificial life forms will displace humansBill Joy made key contributions to the Berkeley Software Distribution(BSD) version of UNIX, including developing its NetworkFile System (NFS). As a cofounder of Sun Microsystems, Joy thenhelped develop innovative workstations and promoted Java asa major language for developing Web applications. (Bill Joy,Kleiner Perkins Caulfield & Byers)

262 Joy, Billwho will be unable to compete with them. He believes thatgiven the ability to reproduce themselves, intelligent robotsor even “nanobots” (see nanotechnology) might soon beuncontrollable.Joy also expresses misgivings about biotechnology andgenetic engineering, seen by many as the dominant scientificand technical advance of the early 21st century. Hehas proposed that governments develop institutions andmechanisms to control the development of such dangeroustechnologies, drawing on the model of the agencies thathave more or less successfully controlled the developmentof nuclear energy and the proliferation of nuclear weaponsfor the past 50 years. (For contrasting views see Kurzweil,Ray and singularity, technological.)In 2003 Joy left Sun and became a venture capitalist,specializing in technologies and projects to combat whathe sees as serious global dangers, such as pandemic diseaseand the possibility of bioterrorism.Joy received the ACM Grace Murray Hopper Award forhis contributions to BSD UNIX before the age of 30. In1993, he was given the Lifetime Achievement Award of theUSENIX Association, “For profound intellectual achievementand unparalleled services to the UNIX community.”Further ReadingBrown, John Seely and Paul Duguid. “A Response to Bill Joy andthe Doom-and-Gloom Technofuturists.” Available online. URL:http://www.aaas.org/spp/rd/ch4.pdf. Accessed August 12, 2007.Joy, Bill. “Why the Future Doesn’t Need Us.” Wired, 8.04, April2000. Available online. URL: http://www.wired.com/wired/archive/8.04/joy.html. Accessed August 12, 2007.Joy, Bill, et al. The Java Language Specification. 3rd ed. Upper SaddleRiver, N.J.: Prentice Hall, 2005. Available online. URL: http://java.sun.com/docs/books/jls/download/langspec-3.0.pdf.Accessed August 12, 2007.O’Reilly, Tim. “A Conversation with Bill Joy.” O’Reilly Network, February12, 2001. Available online. URL: http://www.openp2p.com/pub/a/p2p/2001/02/13/joy.html. Accessed August 12, 2007.

KKay, Alan(1940– )AmericanComputer ScientistAlan Kay developed a variety of innovative concepts thatchanged the way people use computers. Because he devisedways to have computers accommodate users’ perceptionsand needs, Kay is thought by many to be the person mostresponsible for putting the “personal” in personal computers.Kay also made important contributions to objectorientedprogramming, changing the way programmersorganized data and procedures in their work.Kay’s father developed prostheses (artificial limbs) andhis mother was an artist and musician. These varied perspectivescontributed to Kay’s interest in interaction withand perception of the environment. In the late 1960s, whilecompleting work for his Ph.D. at the University of Utah,Kay developed his first innovations in both areas. He helpedIvan Sutherland with the development of a program calledSketchpad that enabled users to define and control onscreenobjects, while also working on the development of Simula, alanguage that helped introduce new programming concepts(see Simula and object-oriented programming). Indeed,Kay coined the term object-oriented in the late 1960s. Heviewed programs as consisting of objects that containedappropriate data that could be manipulated in response to“messages” sent from other objects. Rather than being rigid,top-down procedural structures, such programs were morelike teams of cooperating workers. Kay also worked onparallel programming, where programs carried out severaltasks simultaneously (see concurrent programming). Helikened this structure to musical polyphony, where severalmelodies are sounded simultaneously.Kay participated in the Defense Advanced ResearchProjects Agency (DARPA)—funded research that was leadingto the development of the Internet. One of these DARPAprojects was FLEX, an attempt to build a computer thatcould be used by nonprogrammers through interacting withonscreen controls. While the bulky technology of the late1960s made such machines impracticable, FLEX incorporatedsome ideas that would be used in later PCs, includingmultiple onscreen windows.During the 1970s, Kay worked at the innovative XeroxPalo Alto Research Center (PARC). Kay designed a laptopcomputer called the Dynabook, which featured high-resolutiongraphics and a graphical user interface. While theDynabook was only a prototype, similar ideas would beused in the Alto, a desktop personal computer that couldbe controlled with a new pointing device, the mouse (seeEngelbart, Douglas). A combination of high price andXerox’s less than aggressive marketing kept the machinefrom being successful commercially, but Steven Jobs (seeJobs, Steven) would later use its interface concepts todesign what would become the Macintosh.On the programming side Kay developed Smalltalk, alanguage that was built from the ground up to be trulyobject-oriented (see Smalltalk). Kay’s work showed thatthere was a natural fit between object-oriented programmingand an object-oriented user interface. For example, abutton in a screen window could be represented by a buttonobject in the program, and clicking on the screen button263

264 kernelcould send a message to the button program object, whichwould be programmed to respond in specific ways.After leaving Xerox PARC in 1983, Kay briefly servedas chief scientist at Atari and then moved to Apple, wherehe worked on Macintosh and other advanced projects. In1996, Kay became a Disney Fellow and Vice President ofResearch and Development at Walt Disney Imagineering.In 2001 Kay founded Viewpoints Research Institute, a nonprofitorganization devoted to developing advanced learningenvironments for children. One such project is Squeak,a streamlined but powerful version of Smalltalk that Kaystarted developing in 1995. Another, eToys, is a multiplatform,media-rich, environment that can be used for educationor “just” play. Behind it all is Kay’s continuing effortto do no less than reinvent programming and peoples’ relationshipto computer environments.Kay’s numerous honors include the ACM Turing Award(2003) for contributions to object-oriented programmingand the Kyoto Prize (2004).Further ReadingAlter, Allan E. “Alan Kay: The PC Must Be Revamped—Now.” CIOInsight. Available online. URL: http://www.cioinsight.com/article2/0,1540,2089567,00.asp. Accessed August 1, 2007.Gasch, Scott. “Alan Kay.” Available online. URL: http://ei.cs.vt.edu/~history/GASCH.KAY.HTML. Accessed August 12, 2007.Kay, Alan. “The Early History of Smalltalk.” In Thomas J. Bergin,Jr., and Richard G. Gibson, Jr., eds. History of ProgrammingLanguages II. New York: ACM; Reading, Mass.: Addison-Wesley,1996.Shasha, Dennis, and Cathy Lazere, eds. Out of their Minds: TheLives and Discoveries of 15 Great Computer Scientists. NewYork: Copernicus, 1995.Viewpoints Research Institute. Available online. URL: http://www.vpri.org/. Accessed August 12, 2007.kernelThe idea behind an operating system kernel is that thereis a relatively small core set of “primitive” functions thatare necessary for the operation of system services (see alsooperating system). These functions can be provided in asingle component that can be adapted and updated as desirable.The fundamental services include:• Process control—scheduling how the processes (programsor threads of execution within programs) sharethe CPU, switching execution between processes, creatingnew processes, and terminating existing ones(see multitasking).• Interprocess communication—sending “messages”between processes enabling them to share data orcoordinate their data processing.• memory management—allocating and freeing upmemory as requested by processes as well as implementingvirtual memory, where physical storage istreated as an extension of main (RAM) memory. (Seememory management.)The kernel is an intermediary between users and programs and thehardware system. It provides the functions necessary for allocatingand controlling processes and system resources.• File system services—creating, opening, reading from,writing to, closing, and deleting files. This includes maintaininga structure (such as a list of nodes) that specifiesthe relationship between directories and files. (See file.)In addition to these most basic services, some operatingsystems may have larger kernels that include securityfunctions (such as maintaining different classes of userswith different privileges), low-level support for peripheraldevices, and networking (such as TCP/IP).The decision about what functions to include in the kerneland which to provide through device drivers or systemextensions is an important part of the design of operatingsystems. Many early systems responded to the very limitedsupply of RAM by designing a “microkernel” that could fitentirely in a small amount of memory reserved permanentlyfor it. Today, with memory a relatively cheap resource, kernelstend to be larger and include functions that are pageddynamically into and out of memory.In the UNIX world (and particularly with Linux) thekernel is constantly being improved through informal collaborativeefforts. Many Linux enthusiasts regularly installnew versions of the kernel in order to stay on the “leadingedge,” while more conservative users can opt for waitinguntil the next stable version of the kernel is released.Further ReadingBovet, Daniel, and Marco Cesati. Understanding the Linux Kernel.3rd ed. Sebastapol, Calif.: O’Reilly, 2005.Love, Robert. Linux Kernel Development. 2nd ed. Indianapolis:Novell Press, 2005.Torvalds, Linus. “LinuxWorld: The Story of the Linux Kernel.”linuxtoday. Available online. URL: http://www.linuxtoday.com/developer/1999032500910PS. Accessed August 12, 2007.

Kleinrock, Leonard 265keyboardAlthough most of today’s personal computers feature apoint-and-click graphical interface (see user interfaceand mouse) the keyboard remains the main means forentering text and other data into computer applications.The modern computer keyboard traces its ancestry to thetypewriter, and the layout of its alphabetic and punctuationkeys remains that devised by typewriter pioneer ChristopherLatham Sholes in the late 1860s.The principal difference in operation is that while atypewriter needs only to transfer the impression of a keythrough a ribbon onto a piece of paper, the computer keyboardmust generate an electrical signal that uniquely identifieseach key. This technology dates back to the 1920swith the adoption of the teletypewriter (often known bythe brand name Teletype), which allowed operators to typetext at a keyboard and send it over telephone lines to beprinted. The transmissions used the Baudot character code,which used five binary (off or on) positions to encode lettersand characters. This gave way to the ASCII code in the1960s (see characters and strings) at about the timethat remote time-sharing services allowed users to interactwith computers through a Teletype connection.The modern personal computer keyboard was standardizedin the mid-1980s when IBM released the PC AT. Thisexpanded keyboard now has 101 or 102 keys. It supplementsthe standard typewriter keys with cursor-control (arrow)keys, scroll control keys (such as Page Up and Page Down),a dozen function keys that can be assigned to commandsby software, and a separate calculator-style keyboard fornumeric data entry. During the 1990s, Microsoft introduceda few extra keys for Windows-specific functions.The advent of laptop (or notebook) computers requiredsome compromises. The keys are generally smaller, althoughon the better units they are still far enough apart to allowfor comfortable touch-typing. Laptops often combine thefunction keys and cursor control keys with the regular keys,using a special “Fn” key to shift between them.In recent years, there has been some interest in adoptingan alternative key layout devised by August Dvorak inthe 1950s. The theory behind this layout was that arrangingthe keyboard so the most commonly used keys weredirectly under the fingers would be more efficient than theSholes layout, which legend claims was devised primarilyto slow down typists to a speed that early typewriters couldhandle without jamming. However, researchers have generallybeen unable to find a significant improvement in eitherperformance or ergonomics between use of the standardand Dvorak layouts, and the latter has not caught on commercially.Concern with repetitive strain injury (RSI) has led toexperiments in designing a keyboard more suited to thehuman wrist and hand (see ergonomics of computing).Some designs such as the Microsoft Natural Keyboarddivide the layout into left and right banks of keys and anglethem toward one another to reduce strain on the wrists. Anextreme form of the design actually breaks the keyboardinto two pieces. Such extreme designs have not found wideacceptance.The Microsoft Natural Multimedia Keyboard features access tofunctions needed by today’s computer users along with an ergonomiclayout designed to help reduce typing stress. (MicrosoftCorporation)It is possible that the further development of voice recognitionsoftware might allow spoken dictation to supplantthe keyboard for data entry. Currently, however, such technologyis limited in speed and accuracy (see speech recognitionand synthesis).With the increasingly popular mobile devices (see pdaand smartphone), keyboards are sometimes dispensed withentirely. For light data entry (such as for e-mail and textmessaging), a small version of the standard keyboard canbe used. (In such cases users can type with their thumbs.)With touch-sensitive screens on mobile devices, a “virtualkeyboard” can be displayed on the screen; however, thelack of tactile feedback means this data-entry method takessome getting used to. One can also obtain a keyboard thatcan wirelessly connect to such a device to allow for moreextensive data entry (see Bluetooth.)Further Reading“Computer Keyboard Design.” Cornell University ErgonomicsWeb. Available online. URL: http://ergo.human.cornell.edu/ahtutorials/ckd.htm. Accessed August 12, 2007.Lundmark, Torbjorn. Qwirky Qwerty: The Story of the Keyboard @Your Fingertips. Sydney, Australia: New South Wales UniversityPress, 2002.Kleinrock, Leonard(1934– )AmericanEngineer, Computer ScientistEvery day billions of e-mails, text messages, and media filesare sent over the worldwide Internet. The infrastructurethat allows the efficient transmission of this vast data trafficis largely based on the system of packet-switching and routinginvented by Leonard Kleinrock.Kleinrock was born in 1934 and grew up in New YorkCity. When he was only six years old Kleinrock built a crystalradio, the first of many electronics projects, built fromcannibalized old radios and other equipment. Kleinrock

266 knowledge representationattended the Bronx High School of Science, home of manyof the nation’s top future engineers. However, when it cametime for college, the family had no money to pay for hishigher education, so he attended night courses at the CityCollege of New York while working as an electronics technicianand later as an engineer. Kleinrock graduated first inhis class in 1957 and earned a fully paid fellowship to theMassachusetts Institute of Technology.At MIT Kleinrock became interested in finding ways forcomputers and their users to communicate with each other.The idea of computer networking was in its infancy, but hesubmitted a proposal in 1959 for Ph.D. research in networkdesign.In 1961 Kleinrock published his first paper, “InformationFlow in Large Communication Nets.” Existing telephonesystems did what was called “circuit switching”: Toestablish a conversation, the caller’s line is connected to thereceiver’s, forming a circuit that existed for the durationof the call. This also meant that the circuit would not beavailable to anyone else, and that if something was wrongwith the connection there was no way to route around theproblem.Kleinrock’s basic idea was to set up data connectionsthat would be shared among many users as needed. Insteadof the whole call (or data transmission) being assigned to aparticular circuit, it would be broken up into packets thatcould be sent along whatever circuit was the most direct.If there was a problem, the packet could be resent on analternative route. This form of “packet switching” providedgreat flexibility as well as more efficient use of the availablecircuits. Kleinrock further elaborated his ideas in hisdissertation, for which he was awarded his Ph.D. in 1963.The following year MIT published his book CommunicationsNets, the first full treatment of the subject.Kleinrock joined the faculty at the University of California,Los Angeles. In 1968 the Defense Department’sAdvanced Research Projects Agency (ARPA) asked him todesign a packet-switched network that would be known asARPANET. The computers on the network would be connectedusing special devices called Interface Message Processors(IMPs). The overall project was under the guidanceand supervision of one of Kleinrock’s MIT office mates,Lawrence Roberts.On October 29, 1969, Kleinrock and his assistants sentthe first data packets between UCLA and Stanford overphone lines. Their message, the word “login,” was hardly asdramatic as Alexander Graham Bell’s “Watson, come here,I need you!” Nevertheless, a form of communication hadbeen created that in a few decades would change the worldas much as the telephone had done a century earlier.The idea of computer networking did not catch on immediately,however. Besides requiring a new way of thinkingabout the use of computers, many computer administratorswere concerned that their computers might be swampedwith users from other institutions, or that they might ultimatelylose control over the use of their machines. Kleinrockworked tirelessly to convince institutions to join thenascent network. By the end of 1969 there were just fourARPANET “nodes”: UCLA, the Stanford Research Institute,UC Santa Barbara, and the University of Utah. By the followingsummer, there were ten.During the 1970s Kleinrock trained many of theresearchers who would advance the technology of networking.While Kleinrock’s first network was not the Internet weknow today, it was an essential step in its development. Insuccessfully establishing communication using the packetswitchedARPANET, Kleinrock showed that such a networkwas practicable.By the early 1990s Kleinrock was looking toward a futurewhere most network connections were wireless and accessiblethrough a variety of computerlike devices such as handheld“palmtop” computers, cell phones, and others not yetimagined. In such a network the intelligence or capability isdistributed throughout, with devices communicating seamlesslyso the user no longer need be concerned about whatparticular gadget he or she is using. By the middle of the followingdecade, much of this vision had become reality.Although his name is not well known to the generalpublic, Kleinrock has won considerable recognition withinthe technical community. This includes Sweden’s L. M.Ericsson Prize (1982), the Marconi Award (1986), and theNational Academy of Engineering Charles Stark DraperPrize (2001).Further ReadingHafner, Katie, and Matthew Lyon. Where Wizards Stay Up Late: TheOrigins of the Internet. New York: Simon and Schuster, 1996.Kleinrock, Leonard. “Information Flow in Large CommunicationNets.” Available online. URL: http://www.lk.cs.ucla.edu/LK/Bib/REPORT/PhD/proposal.html. Accessed May 3, 2007.“Leonard Kleinrock’s Home Page.” Available online. URL: http://www.lk.cs.ucla.edu/. Accessed May 3, 2007.knowledge representationThe earliest concern of computer science was the representationof “raw” data such as numbers in programs (see datatypes). Such data can be used in calculations, and actionstaken based on tests of data values, using branching (IF) orlooping structures.However, facts are more than data. A fact is an assertion,for example about a relationship, as in “Joe is a son ofMike,” often expressed in a form such as son (Joe, Mike).Implications can also be defined as proceeding from facts,such asson (Joe, Mike) implies father (Mike, Joe) orson (Joe, Mike) and son (Mike, Phil) impliesgrandson (Joe, Phil)While it can be expressed in a variety of different formsof notation, this predicate calculus forms the basis formany automated reasoning systems that can operate on a“knowledge base” of assertions, prove the validity of a givenassertion, and even generate new conclusions based uponexisting knowledge (see also expert systems).An alternative form of knowledge representation usedin artificial intelligence programs is based on the idea offrames. A frame is a structure that lists various character-

Knuth, Donald 267istics or relationships that apply to a given individual orclass. For example, the individual “cat” might have a framethat includes characteristics such as “warm-blooded” and“bears live young.” In turn, these characteristics are alsoassigned to the class “mammal” such that any individualhaving those characteristics belongs to that class. A programcan then follow the linkages and conclude that a cat isa mammal. Linkages can also be diagrammed as a “semanticnetwork” in a structure called a directed graph, with thelines between nodes labeled to show relationships.Knowledge representation systems have different considerationsdepending on their intended purpose. A KR systemin an academic research setting might be intended todemonstrate completeness: that is, it can generate all possibleconclusions from the facts given. However, expert systemsdesigned for practical use usually do not attempt to generateall possible conclusions (which might be computationallyimpracticable) but to generate useful conclusions thatare likely to serve the needs of the knowledge consumer.It is also important to note that epistemology (the theoryof knowledge) plays an important role in understandingand evaluating KR systems. As an example, the assertion“Mary believes she is 600 years old” might be a fact (Maryis observed to hold such a belief), but the contents of thebelief are presumably not factual. The context of this beliefmight also be different if Mary is an adult as opposed tobeing a five-year-old child. Similarly, ontological (state ofbeing) considerations can also complicate the evaluation ofassertions. For example, should a fire be treated as an objectin itself, a process, or an attribute of a burning object?Knowledge representation thus intertwines philosophy andcomputer science.The booming interest in extracting new patterns fromdata (see data mining) and the effort to encode moreknowledge into Web documents (see ontologies and datamodels, semantic Web, and xml) all involve applicationsof knowledge representation.Perhaps the most ambitious knowledge representationproject (and the longest-lasting one) has been Cyc (short forEncyclopedia). Headed by AI researcher Douglas Lenat, theobject of Cyc is to create a massive network representingthe relationships and characteristics of millions of objectsand concepts found in peoples’ daily lives and work. Ideallya wide variety of programs (both specialized and generalpurpose) will be able to use this knowledge base (seeexpert system). Projects such as Cyc and the Web OntologyLanguage (Owl) also offer the possibility of a muchmore intelligent Web search (see search engine) as well assystems that can automatically summarize news stories andother material.Further ReadingBrachman, Ronald, and Hector Levesque. Knowledge Representationand Reasoning. San Francisco: Morgan Kaufmann, 2004.Cycorp. Available online. URL: http://www.cyc.com/. AccessedAugust 12, 2007.Davis, Randall, Howard Shrobe, and Peter Szolovits. “What Is aKnowledge Representation?” AI Magazine 14 (1993): 17–33.Available online. URL: http://groups.csail.mit.edu/medg/ftp/psz/k-rep.html. Accessed August 12, 2007.Lacy, Lee W. Owl: Representing Information Using the Web OntologyLanguage. Victoria, B.C., Canada: Trafford, 2005.Makahfi, Pejman. “Introduction to Knowledge Modeling.” Availableonline. URL: http://www.makhfi.com/KCM_intro.htm.Accessed August 12, 2007.Knuth, Donald(1938– )AmericanComputer ScientistDonald Knuth has contributed to many aspects of computerscience, but his most lasting contribution is his monumentalwork, The Art of Computer Programming, which is still inprogress.Born in Milwaukee on January 10, 1938, Knuth’s initialbackground was in mathematics. He received his master’sdegree at the Case Institute of Technology in 1960and his Ph. D. from the California Institute of Technology(Caltech) in 1963. As a member of the Caltech mathematicsfaculty Knuth became involved with programming andsoftware engineering, serving both as a consultant to theBurroughs Corporation and as editor of the Associationfor Computing Machinery (ACM) publication ProgrammingLanguages. In 1968, Knuth confirmed his change of careerdirection by becoming professor of computer science atStanford University.In 1971, Knuth published the first volume of The Artof Computer Programming and received the ACM GraceMurray Hopper Award. His broad contributions to thefield as well as specific work in the analysis of algorithmsand computer languages garnered him the ACM TuringAward, the most prestigious honor in the field. Knuthalso did important work in areas such as LR (left-to-right,rightmost) parsing, a context-free parsing approach usedin many program language interpreters and compilers(see parsing).However, Knuth then turned away from writing for anextended period. His primary interest became the developmentof a sophisticated software system for computer-generatedtypography. He developed both the TeX documentpreparation system and METAFONT, a system for typefacedesign that was completed during the 1980s. TeX found asolid niche in the preparation of scientific papers, particularlyin the fields of mathematics, physics, and computerscience where it can accommodate specialized symbols andnotation.Knuth did return to The Art of Computer Programmingand by the late 1990s he had completed two more of aprojected seven volumes. With his broad interests and contributionsand “big picture” approach to the evaluation ofprogramming languages, algorithms, and software engineeringmethodologies, Knuth can fairly be described asone of the “Renaissance persons” of the computer sciencefield. His numerous awards include the ACM Turing Award(1974), IEEE Computer Pioneer Award (1982), AmericanMathematical Society’s Steele Prize (1986), and the IEEE’sJohn von Neumann Medal (1995).

268 Kurzweil, RayFurther ReadingFrenkel, Karen A. “Donald E. Knuth: Scholar with a Passion forthe Particular.” Profiles in Computing, Communications of theACM, vol. 30, no. 10, October 1987.———. The Art of Computer Programming. 3rd ed. vols. 1–3. Reading,Mass.: Addison-Wesley, 1998.Knuth, Donald E. Literate Programming. Stanford, Calif.: Centerfor the Study of Language and Information, 1992.———. Things a Computer Scientist Rarely Talks About. Stanford,Calif.: CSLI Publications, 2001.Slater, Robert. Portraits in Silicon. Cambridge, Mass.: MIT Press,1987.Kurzweil, Ray(1948– )AmericanInventor, FuturistRay Kurzweil began his career as an inspired inventor whobrought words to the blind and new kinds of sounds tomusicians. Drawing upon his experience with the rapidProlific inventor and futurist Ray Kurzweil believes thattechnology will soon take an exponential leap called “thesingularity.” (Melanie Stetson Freeman / The Christian ScienceMonitor / Getty Images)progress of technology, Kurzweil then wrote a series ofbooks that predicted a coming breakthrough into a worldshared by advanced intelligent machines and enhancedhuman beings.Kurzweil was born on February 12, 1948, in Queens,New York, to an extremely talented family. Kurzweil’sfather, Fredric, was a concert pianist and conductor. Kurzweil’smother, Hanna, was an artist, and one of his uncleswas an inventor. By the time he was 12, Kurzweil wasbuilding and programming his own computer. He wrote astatistical program that was so good that IBM distributedit as well as a music-composing program. The latter earnedhim first prize in the 1964 International Science Fair anda meeting with President Lyndon B. Johnson in the WhiteHouse. Kurzweil even appeared on the television show I’veGot a Secret.In 1967 Kurzweil enrolled in the Massachusetts Instituteof Technology, majoring in computer science and literature.By the time he received his B.S. in 1970, Kurzweil had metsome of the most influential thinkers in artificial intelligenceresearch, including Marvin Minsky, whom he lookedto as a mentor (see Minsky, Marvin). Kurzweil had becomefascinated with the use of AI to aid and expand humanpotential. In particular, he focused on pattern recognition,or the ability to classify or recognize patterns such as theletters of the alphabet on a page of text.Early character-recognition technology had been limitedbecause it could only match very precise shapes, making itimpractical for reading most printed material. Kurzweil,however, used his knowledge of expert systems and otherAI principles to develop a program that could use generalrules and relationships to “learn” to recognize just aboutany kind of text (see ocr). This program, called Omnifont,would be combined with the flatbed scanner (which Kurzweilinvented in 1975) to create a system that could scantext and convert the images into the corresponding charactercodes, suitable for use with programs such as wordprocessors.A chance conversation with a blind fellow passenger ona plane convinced Kurzweil that he could build a machinethat could scan text and read it out loud. Kurzweil wouldcombine his scanning technology with a speech synthesizer(see speech recognition and synthesis). Kurzweil had tocreate an expert system with hundreds of rules for properlyvoicing the words in the text.In 1976 Kurzweil was able to announce the KurzweilReading Machine (KRM). Soon after the machine’s debut,Kurzweil struck up a friendship with the legendary blindpop musician Stevie Wonder. They shared an interest inmusical instruments and music synthesis. Existing analogsynthesizers were very versatile, but their output sounded“thin” and artificial compared to the rich overtones in thesound of a piano or guitar. Kurzweil was able to create amuch more realistic synthesizer sound using digital ratherthan analog technology.The first Kurzweil synthesizer, the K250, was released in1983. His machine was the result of considerable researchin digitally capturing and representing the qualities of notesfrom particular instruments, including the “attack,” or ini-

Kurzweil, Ray 269tial building of sound, the “decay,” or decline in the sound,the sustain, and the release (when the note is ended.) Theresulting sound was so accurate that professional orchestraconductors and musicians could not distinguish the synthesizedsound from that of the real instruments.Throughout the 1980s and 1990s Kurzweil applied hisboundless inventiveness to a number of other challenges,including speech recognition. The reverse of voice synthesis,speech recognition involves the identification of phonemes(and thus words) in speech that has been convertedinto computer sound files. Kurzweil sees a number of powerfultechnologies being built from voice recognition andsynthesis, including telephones that automatically translatespeech and devices that can translate spoken words into textin real time for deaf people. He also believes that the abilityto control computers by voice command, which is currentlyrather rudimentary, should also be greatly improved.Technological Apocalypse?During the 1990s, though, much of Kurzweil’s interestturned from inventing the future to considering its likelycourse. His 1990 book The Age of Intelligent Machinesoffered a popular account of how AI research would changemany human activities. In 1999 Kurzweil published TheAge of Spiritual Machines. It made the provocative claimthat, by the middle of the 21st century, machine intelligencewould surpass that of humans. Kurzweil revisitedthe topic in his latest book, The Singularity Is Near (2005).The title seems to consciously echo the apocalyptic languageof a prophet predicting the last judgment or thecoming of a messiah. The word “singularity” is intendedto describe the effects of relentless, ever-increasing technologicalprogress that eventually reaches a sort of “criticalmass” and changes the world beyond all recognition(see singularity, technological).As he depicts life in 2009, 2019, 2029, and finally 2099,Kurzweil portrays a world in which sophisticated AI personalitiesbecome virtually indistinguishable from humansand can serve people as assistants, advisers, and even lovers.Meanwhile, neural implants will remove the obstaclesof handicaps such as blindness, deafness, or lack of mobility(see neural interface). Other implants will greatlyenhance human memory, allow for the instant downloadof knowledge, and function as “natural” extensions to thebrain. (For critics of such “strong AI” claims see Dreyfus,Hubert and Weizenabum, Joseph.)Kurzweil continues to engage in provocative projects.Under the slogan “live long enough to live forever,” he isresearching and marketing various supplements intendedto promote longevity, and he reportedly monitors his owndiet and bodily functions carefully.Whatever the future brings, Ray Kurzweil has becomeone of America’s most honored inventors. Among otherawards, he has been elected to the Computer Industry Hallof Fame (1982) and the National Inventors Hall of Fame(2002). He has received the ACM Grace Murray HopperAward (1978), Inventor of the Year Award (1988), the LouisBraille Award (1991), the National Medal of Technology(1999), and the MIT Lemelson Prize (2001).Further ReadingHenderson, Harry. Artificial Intelligence: Mirrors for the Mind. NewYork: Chelsea House, 2007.Joy, Bill. “Why the Future Doesn’t Need Us.” Wired Magazine 8(April 2000). Available online. URL: http://www.wirednews.com/wired/archive/8.04/joy.html. Accessed May 5, 2007.Kurzweil, Raymond. The Age of Spiritual Machines: When ComputersExceed Human Intelligence. New York: Putnam, 1999.———. The Singularity Is Near. New York: Viking, 2005.KurzweilAI.net. Available online. URL: http://www.kurzweilai.net/. Accessed May 5, 2007.Kurzweil Technologies. Available online. URL: http://www.kurzweiltech.com/ktiflash.html. Accessed May 5, 2007.Richards, Jay, ed. Are We Spiritual Machines?: Ray Kurzweil vs. theCritics of Strong AI. Seattle, Wash.: Discovery Institute, 2001.

LLAN See local area network.language translation softwareAnyone who has learned a new language has also gainedan appreciation for how difficult it is to translate from onelanguage to another while preserving the intent, meaning,and context of the original. Not surprisingly, developingsoftware to perform this task, often called “machinetranslation” (MT), has also proven to be difficult. (For amore general discussion of how languages can be representedor studied using a computer, see linguistics andcomputing.)Rules-Based ApproachesThere are several approaches that can be taken to automaticlanguage translation. A rules-based system parses the originaltext to construct an intermediate representation. Theprogram then “transfers” the represented structure to anequivalent structure in the target language, drawing uponextensive lexicons (dictionaries) containing such thingsas phrase structures, word structures (morphology), andsemantics (meanings). Developing this extensive knowledgebase and the rules for manipulating it is the mostchallenging part of developing rules-based language translationsystems. (For more on the general process of computer“understanding” of language, see natural languageprocessing.)Generally a translation produced by a rules-based systemwill be intelligible to a speaker of the target language,who will be able to understand the broad meaning of theoriginal text. However, it is likely to sound “awkward” andmiss certain nuances.A simplified approach is based on a dictionary of wordsor phrases and their meanings. Each source word or phraseis simply looked up and converted to its equivalent in thetarget language. Because it does not deal with grammaticalstructure or context, this method is not very satisfactoryexcept perhaps for translating simple lists or catalogues.Statistical ApproachesThe other main approach to automatic translation relieson statistical analysis of a large body of text (corpus) thatis already translated into two languages. For example, theBayes theorem (see Bayesian analysis) can be used to estimatethe probability that string A in French (for example,“c’est un chien”) will occur in the English version as stringA’ “it’s a dog.”). Depending on the application, the sameapproach can be applied word for word, phrase for phrase,or sentence for sentence. Statistical approaches have hadgood success (particularly if the corpus is both representativeand sufficiently extensive). However, since it is basedon probability, there is always a chance that a segment oftext will be given the most likely translation rather than themeaning intended by the writer.Evaluation and ApplicationsThere are a number of features in real human languagesand usage that are challenging for translation software todeal with. Words can be ambiguous due to multiple mean-270

Lanier, Jaron 271ings, and phrases can be syntactically ambiguous. (Afamous example is, “Time flies like an arrow; fruit flies likea banana.”) Rules-based translation software can attemptto include rules for determining which word or sentencemeaning is intended, while statistically based programs cantry to determine the probability that a given word or phrasein a given context has a certain meaning. Idioms or wordsthat are not in the program’s dictionary can also cause problems.(For example, Babel Fish translates “He already hadtwo strikes against him” literally, losing the nuance basedon the baseball reference.)There are a variety of translation software packages inuse today. The oldest is SYSTRAN, which was developedduring the cold war of the 1960s to translate Russian scientificand technical documents, and later has been used bythe European Union to work with documents in the union’svarious languages. Today SYSTRAN is the engine behindsuch popular Web sites from AltaVista (Babel Fish) andGoogle Language Tools. These services can translate text orwhole Web pages (with varying degrees of success).Simple handheld translation devices with phrases commonlyneeded by travelers are also available. More sophisticateddevices (see speech recognition and synthesis)that can facilitate two-way conversations are also beingdeveloped for applications such as military interrogationand civil affairs.Further ReadingBabel Fish (AltaVista). Available online. URL: http://babelfish.altavista.com/. Accessed September 25, 2007.Hutchins, W. John. “Compendium of Translation Software.” June2007. Available online. URL: http://www.hutchinsweb.me.uk/Compendium.htm. Accessed September 25, 2007.Hutchins, W. John and Harold L. Somers. Introduction to MachineTranslation. Burlington, Mass.: Academic Press, 1992.Trujillo, Arturo. Translation Engines: Techniques for Machine Translation.New York: Springer, 1999.Lanier, Jaron(1960– )AmericanComputer Scientist, InventorJaron Lanier pioneered the technology of virtual reality thatis gradually having an impact on areas as diverse as entertainment,education, and even medicine.Lanier was born on May 3, 1960, in New York City,although the family would soon move to Las Cruces, NewMexico. Lanier’s father was a cubist painter and sciencewriter and his mother a concert pianist (she died when theboy was nine years old). Living in a remote area, the precociousLanier learned to play a large variety of exotic musicalinstruments and created his own science projects.Lanier dropped out of high school, but fortunately sympatheticofficials at New Mexico State University let himtake classes there when he was only 14 years old. Laniereven received a grant from the National Science Foundationto let him pursue his research projects. Although fascinatedby computers (and their possibilities as an aid to musicand other expressive arts), Lanier had a sporadic academiccareer, taking him to Bard College, where he dropped out oftheir computer music program.However, by the mid-1980s Lanier had gotten back intocomputing by creating sound effects and music for Atarivideo games and writing a commercially successful gameof his own called Moondust. He developed a reputation as arising star in the new world of game design.Lanier then began to experiment with ways to immersethe player more fully in the game experience. Using moneyfrom game royalties, he joined with a number of experimentersand built a workshop in his house. One of thesecolleagues was Tom Zimmermann, who had designed a“data glove” that could send commands to a computer basedon hand and finger positions.As the 1980s progressed, investors became increasinglyinterested in the new technology, and Lanier was able toexpand his operation considerably, working on projects forNASA, Apple Computers, Pacific Bell, Matsushita, and othercompanies.Lanier then coined the term “virtual reality” todescribe the experience created by this emerging technology.A user wearing a special helmet has a computergeneratedscene projected such that the user appears to be“within” the world created by the software. The world isan interactive one: Using gloves and body sensors, whenthe user walks in a particular direction the world shiftsjust as it would when walking in the “real” world. Thegloves appear as the user’s “hands” in the virtual world,and objects in that world can be grasped and manipulatedmuch like real objects. In effect, the user has been transportedto a different world created by the VR software(see virtual reality).Virtual reality technology had existed in some form longbefore Lanier; it perhaps traces its roots back to the firstmechanical flight simulators built during World War II.However, existing systems such as those used by NASA andthe Air Force were extremely expensive, requiring powerfulmainframe computers. They also lacked flexibility—eachsystem was built for one particular purpose, and the technologywas not readily transferable to new applications.Lanier’s essential achievement was to use the new, inexpensivecomputer technology of the 1980s to build versatilesoftware and hardware that could be used to create an infinitevariety of virtual worlds.Unfortunately the hippylike Lanier (self-described asa “Rastafarian hobbit” because of his dreadlocks) did notmesh well with the big business world into which his initialsuccess had catapulted him. Lanier had to juggle numeroussimultaneous projects as well as becoming embroiled indisputes over his patents for VR technology. In 1992 Lanierlost control of his patents to a group of French investorswhose loans to VPL Research had not been paid, and hewas forced out of the company he had founded.During the 1990s Lanier founded several new companiesto develop various types of VR applications. Theseinclude the Sausalito, California, software companyDomain Simulations and the San Carlos, California, companyNew Leaf Systems, which specialized in medical

272 laptop computerapplications for VR technology. Another company, NewYork-based Original Ventures, focuses on VR-based entertainmentsystems.From 1997 to 2001, Lanier was chief scientist ofAdvanced Network and Services, a developer of the Internet2(advanced high-speed networking) project, as well asserving as lead scientist of the National Tele-ImmersionInitiative, a coalition of universities developing applicationsfor Internet2. From 2001 to 2004 Lanier was also a visitingscientist at Silicon Graphics, Inc., doing fundamentalresearch on tele-immersion and telepresence. Since 2004Lanier has been a fellow at the International Computer ScienceInstitute at UC Berkeley and since 2006, an interdisciplinaryscholar-in-residence at Berkeley.Futurist and Technology PunditLanier’s humanistic and artistic background is reflectedin the stance he has taken in recent years toward the technologyhe helped create. He has a column called “Jaron’sWorld” in Discover magazine and regularly contributesto other publications such as Edge. In his writings Lanierhas criticized the tendency to see the Internet as somesort of collective intelligence, warning that the individualmight be in danger of being overwhelmed (see flashmob). Lanier has also coined the term “cybernetic totalism”to refer to the tendency to put the constructs of thecomputer world ahead of the full dimensionality of humanexperience.Besides writing and lecturing on virtual reality, Lanier isactive as both a musician and an artist. In 1994 he releasedhis CD Instruments of Change. Lanier’s paintings and drawingshave also been exhibited in a number of galleries.Further ReadingCave, Damien. “Artificial Stupidity: Virtual Reality PioneerJaron Lanier Says Computers Are Too Dumb to Take Overthe World.” Salon.com, Oct. 4, 2000. Available online. URL:http://archive.salon.com/tech/feature/2000/10/04/lanier/index.html. Accessed February 6, 2008.“Homepage of Jaron Lanier.” Available online. URL: http://www.jaronlanier.com/. Accessed September 25, 2007.Lanier, Jaron. “The Hazards of the New Online Collectivism.”Edge. Available online. URL: http://www.edge.org/3rd_culture/lanier06/lanier06_index.html. Accessed September25, 2007.———. “One Half of a Manifesto.” Available online. URL: www.edge.org/3rd_culture/lanier/lanier_index.html. Accessed September25, 2007.Steffen, Alan. “What Keeps Jaron Lanier Awake at Night: ArtificialIntelligence, Cybernetic Totalism, and the Lack of CommonSense.” Whole Earth (Spring 2003): 24–29. Available online.URL: http://www.wholeearthmag.com/ArticleBin/111-5.pdf.Accessed September 25, 2007.laptop computerA laptop is a portable computer that contains all components(keyboard, display, motherboard, drives, etc.) in asingle (usually hinged) case. In general, a laptop can performthe same tasks as a desktop computer, though not necessarilyas quickly. (Laptops that have the full power andA traditional laptop computer with a clamshell case. Laptops arenow differentiated into lighter, more compact “notebooks” andsomewhat larger and heavier “desktop replacement” units. Meanwhile,smaller hand held devices can replace laptops for somefunctions.capacity of a desktop are sometimes called “desktop replacements,”while smaller, lighter, but less powerful machinesare called “notebooks.” For even smaller or lighter computers,see pda and tablet pc.)Typical ComponentsA typical laptop computer in 2007 has the following components:• a processor such as Intel Core 2 duo or a version (suchas Pentium M) optimized for wireless and lower-powerconsumption• one or two gigabytes (GB) of system memory• hard drive (80 to 160 GB capacity)• combo CD/DVD optical drive with read-and-writecapabilities• LCD flat panel display (widescreen format) from 14inches to 17 inches• graphics card or integrated graphics• wireless networking• keyboard with touch pad and/or pointing stick (tosimulate the mouse)• six- or nine-cell lithium ion or lithium polymer batteryModern laptops are well supplied with USB and network(Ethernet) ports. Many include readers for memory cards(such as SD cards). Additional capabilities can be providedby means of PC cards or Express cards. Most laptops runthe same operating systems (such as Windows Vista or MacOS X) as their desktop counterparts.While portable and convenient, laptops do have somedisadvantages compared to desktops: They cost more for agiven level of performance; they are more difficult to repair;and they are more attractive to thieves.

legal software 273Development and TrendsThe idea of small, portable personal computers goes backto the Dynabook concept developed at Xerox PARC in the1970s (see also Kay, Alan). The first “portable” computerswere often more aptly described as “luggable,” having morethe form factor of a suitcase than that of today’s laptops.Nevertheless, the first commercially successful portablecomputers, the Osborne 1 (1981) and the Compaq Portable(1983), began to show the feasibility of portable computing.(At the other end of the size spectrum, the successfulRadio Shack TRS-80 Model 100 established the utility ofthe notebook-sized computer.) In the 1980s true laptopsfrom companies such as Zenith and Toshiba with the familiarclamshell design emerged, running PC-compatible MS-DOS and, later, Windows applications. (Apple entered themarket with the Macintosh Portable in 1989, followed bythe PowerBook series, introduced in 1991.)Most improvements in laptops in the 1990s and beyondhave been incremental (more storage, sharper displays,more efficient batteries, and so on). Wireless (see Bluetoothand wireless and mobile computing) connectivityis now standard. Laptop development has bifurcatedsomewhat, with higher-end machines rivaling desktops formedia, gaming, and other applications, while notebooksoften become lighter, sometimes forgoing optical and evenhard drives in favor of network connectivity and flash memorystorage. Specially “ruggedized” laptops are used by themilitary on battlefields and in other harsh environments.Meanwhile, PDAs and smart phones capable of e-mail, Webbrowsing, and light data entry offer an alternative to laptopsfor people who are on the road frequently.Further ReadingGookin, Dan. Laptops for Dummies. 2nd ed. Hoboken, N.J.: Wiley,2006.Laptop Magazine. Available online. URL: http://www.laptopmag.com/index.htm. Accessed September 26, 2007.Laptops [resources and reviews]. Available online. URL: http://reviews.cnet.com/laptops.html. Accessed September 26, 2007.Miller, Michael. Your First Notebook PC. Indianapolis: Que, 2008.Sandler, Corey. Upgrading & Fixing Laptops for Dummies. Indianapolis:Wiley, 2006.Wilson, James E. Vintage Laptop Computers: First Decade, 1980–89.Denver, Colo.: Outskirts Press, 2006.law enforcement and computersBesides his superb reasoning skills, perhaps Sherlock Holmes’smost important asset was his extensive collection ofnotes that provided a cross-referenced index to London’scriminal underworld. Today computer applications havegiven law enforcers investigative, forensic, communication,tactical, and management tools that Holmes and his rivalsin the old Scotland Yard could not have imagined.For the officer on the street, the ability to obtain autolicense, stolen vehicle, or outstanding warrant information innear real-time provides a much better picture of the potentialrisk in making stops or arrests. Other “tactical” technologyincludes new devices for homing in on gunshots and thegrowing use of remote-controlled robots for bomb disposaland hostage negotiations (see robotics). A more controversialarea is the use of CCTV (closed-circuit TV) surveillancecameras in public places, advocated as a crime deterrent butraising concerns about privacy and intrusive social control.If a criminal case is opened, a variety of software applicationscome into play. These include case managementprograms for keeping track of evidence and witness interviews.Evidence must be properly logged at all times tomaintain a legally defensible chain of custody against accusationsof tampering.The investigation of a crime involves many computerizedforensic aids. Besides automated matching offingerprints and, increasingly other physical data (see biometrics),records can also be searched to detect patternssuch as crimes with related modus operandi (MOs). Theability to access information from other jurisdictions andto interface federal, state, and local agencies is also veryimportant, particularly for cases involving organized crime,interstate fugitives, and terrorism.Since data stored on computers is an increasingly prevalentform of evidence, law enforcement specialists must alsoemploy tools to recover data that may have been partiallyerased or encrypted by suspects (see computer forensics).Computers can be more active instruments of crime (seecomputer crime and security). Such traditional tools aswiretapping must be adapted to new forms of communicationsuch as e-mail while addressing concerns about civilliberties and privacy (see privacy in the digital age).High-level planning for law enforcement budgets andpriorities requires access to detailed crime statistics. At thenational level, the Justice Department’s Bureau of JusticeStatistics is a definitive information source. Law enforcers,like other professionals, increasingly use Web sites,chat areas, and e-mail lists to discuss computer-related lawenforcement issues with colleagues.Law enforcement agencies also use the same “bread andbutter” software needed by any substantial organization,including word processing, spreadsheet, payroll, and otheraccounting programs.Further ReadingBoba, Rachel. Crime Analysis and Crime Mapping. Thousand Oaks,Calif.: Sage Publications, 2005.Chu, James. Law Enforcement Information Technology: A Managerial,Operational, and Practitioner Guide. Grand Rapids, Mich.:CRC Press, 2001.Foster, Raymond E. Police Technology. Upper Saddle River, N.J.:Prentice Hall, 2004.Goold, Benjamin J. CCTV and Policing: Public Area Surveillance andPolice Practices in Britain. New York: Oxford University Press,2004.Gottschalk, Petter. Knowledge Management Systems in Law Enforcement:Technologies and Techniques. Hershey, Pa.: Idea GroupPublishing, 2006.Pattvina, April, ed. Information Technology and the Criminal JusticeSystem. Thousand Oaks, Calif.: Sage Publications, 2004.legal softwareModern law offices rely heavily on software to managecases and records, to perform legal research, and to prepare

274 Lessig, Lawrencepleadings and other documents. Many of these functionscan be included in a legal software suite such as AmicusAttorney. Some typical law office management modulesinclude the following:• client file, which provides links to all events, tasks,time and billing, and so on involving each client• general contact file with contact information for otherpeople the office deals with regularly (such as courtclerks)• calendar for managing appointments, meetings, anddeadlines• time tracking and billing• document management (often interfaces with suitessuch as Microsoft Office)Research ToolsLegal research is easier (but in some ways more complex)than in the days of going through dusty files in the localcourthouse or poring through a law library. The most usedonline database for legal research is LexisNexis, which containstwo parts: Lexis (focusing on legal documents) andNexis (for business research). Some of the most importantLexis content is:• text of all U.S. statutes and laws• U.S. published case opinions• public records including property records, liens, andlicenses• laws and opinions for many non-U.S. jurisdictions• articles from law journalsA free service called LexisOne provides a subset ofU.S. legal decisions. Lexis also has a File & Serve servicethat allows for documents to be filed with courts or servedupon participating firms. Nexis complements Lexis formany investigations because it offers news articles, particularlythose relating to business activities. Other commerciallegal information services include Westlaw andLoislaw. A free compilation of legal information that canprovide an alternative for researching laws and cases isprovided by the Legal Information Institute at CornellUniversity.Finding citations or news is only part of the task ofthe legal researcher. The organization and managementof all the data needed for any legal specialty is challenging.Printed reference books are cumbersome and canbe quickly outdated. Recently a number of legal writershave been using wikis (see wikis and Wikipedia) as atool for collaboration in creating online legal references.For example, the Internet Law Treatise sponsored by theElectronic Frontier Foundation covers a variety of legalissues relating to the use of the Internet. The Legal InformationInstitute at Cornell Law School is collaboratingwith experts to create a complete legal dictionary andencyclopedia in wiki form.Further ReadingBernstein, Paul. “Winning Software for Winning Cases.” Trial, 37(November 1, 2001): 82 ff.Delaney, Stephanie. Electronic Legal Research: An IntegratedApproach. Albany, N.Y.: Delmar (Thomson), 2002.Internet Law Treatise (Electronic Frontier Foundation.) Availableonline. URL: http://ilt.eff.org/index.php/Table_of_Contents.Accessed September 26, 2007.Law Office Computing Magazine. Available online. URL: http://www.lawofficecomputing.com. Accessed September 26, 2007.LexisNexis. Available online. URL: http://www.lexisnexis.com.Accessed September 26, 2007.Payne Consulting. Microsoft Word 2002 for Law Firms. Roseville,Calif.: Prima Publishing, 2001.Wex (Legal Information Institute at Cornell Law School). Availableonline. URL: http://www.law.cornell.edu/wex/index.php/Main_Page. Accessed September 26, 2007.Lessig, Lawrence(1961– )AmericanLaw Professor and WriterLaw professor Lawrence Lessig is a pioneer in developinglegal theories that deal with some of the most difficultissues emerging in the online world (see, for example,intellectual property and computing).Lessig was born on June 3, 1961, in Rapid City, SouthDakota, but grew up in Williamsport, Pennsylvania. As astudent at Yale Law School in the 1970s, Lessig, though previouslypresident of Pennsylvania’s Teenage Republicans,became interested in liberal values following the Watergatescandal and his exposure to authoritarian communistregimes during a summer trip to Eastern Europe.After graduating from Yale, Lessig clerked for U.S.Supreme Court Justice Antonin Scalia, an articulate conservativewith whom he could debate a variety of issues.When he began to teach law himself at the University ofChicago in 1991, he also began to incorporate issues arisingin cyberspace in his lectures. In one article Lessig criticizedthe Communications Decency Act for forcing sitesto block access to adult pornography in order to protectchildren. Eventually the Supreme Court agreed and overturnedthe law.In the late 1990s Lessig served as a special master to theSupreme Court in the Microsoft antitrust case. This timeLessig sided with the government, agreeing that Microsofthad used its near monopoly in operating systems to bundleits own Web browser to the detriment of rival Netscape.The Creative CommonsIn recent years Lessig has undertaken to promote a morecomprehensive set of legal principles aimed at protectingprivacy, expression, and other fundamental rights in cyberspace.Many of the early and more radical Internet advocatessaw the new medium as a libertarian or anarchist“free zone” that needed to be protected from any governmentinterference. Lessig, however, has argued in his booksCode and Other Laws of Cyberspace (2000) and Code Version2.0 (2006) that the online world needs a combination

libraries and computing 275of technical architecture, private initiative, and reasonableregulation.In his book Free Culture (2004) Lessig celebrates the creativityand freedom of expression of the Internet but warnsthat the Net may soon be “locked down” by the power ofthe corporate media. Lessig is therefore a strong supporterof “net neutrality,” the proposed policy that would prohibitInternet service providers from charging different rates fordifferent content providers or types of content (see netneutrality). Without this policy, advocates believe thatlarge corporations will gradually squeeze smaller, independentvoices off the Web by making it harder for them toaccess users. In effect, what had been a shared “commons”would become property bounded by fences, much as commonpastures were once turned into private farms.According to Lessig, another obstacle to a vigorousonline creative culture is the present copyright system.Under this system there is a presumption that permissionis required for most usage of a work. This makes it difficultfor creators to confidently use all the tools for working withexisting content to create new expressions (see mashups).To protect free expression, Lessig founded an organizationcalled Creative Commons in 2001, which has developeda new kind of license. Under this license the creatorcan specify what users can do with the work—copy it, createderivative works, and so on. Thus far Creative Commonslicenses have mainly been applied to online works such asimages shared on photo-sharing sites. Because applying fora Creative Commons license includes providing descriptors(metadata) about the work, people looking for material tobe used in their own work can easily determine what theyare allowed to do with a given work.In 1997 Lessig left his professorship at the Universityof Chicago Law School to become a professor at HarvardLaw School (1997–2000), and then Stanford (2000– ).Lessig has been a guest lecturer at many universities andother institutions around the world. He also serves as aboard member for many important cyberspace institutions,including the Electronic Frontier Foundation and CreativeCommons.In early 2008 Lessig announced that he would take ona challenge perhaps even more daunting than preservingInternet freedom—the battle against what he sees as pervasivecorruption in the political system. He has proposed thecreation of a grassroots movement that would encourageall incumbents and candidates to pledge to stop acceptingcontributions from lobbyists, to stop putting special interest“pork” in legislation, and to conduct publicly financedcampaigns.Lessig has received a number of academic awards as wellat the Editor’s Choice award from Linux Journal (2002), wasnamed one of Fifty Top Innovators by Scientific American(2002), and received the Free Software Foundation Award(2003).Further ReadingCreative Commons. Available online. URL: http://creativecommons.org/. Accessed September 26, 2007.Lessig, Lawrence. Code: Version 2.0 New York: Basic Books, 2006.———. Free Culture: The Nature and Future of Creativity. New York:Penguin Books, 2004.Lessig blog. Available online. URL: http://www.lessig.org/.Accessed September 26, 2007.O’Brien, Chris. “Stanford Law Prof Wants Society to Clean UpIts Act.” San Jose Mercury News, September 9, 2007. Availableonline. URL: http://www.mercurynews.com/business/ci_6843973. Accessed September 26, 2007.libraries and computingThe library is the institution traditionally charged with thecollection and distribution of humanity’s collective heritageof written information. It is thus not surprising that thedevelopment of modern information technology has meantthat libraries have had to undergo pervasive changes intheir practices and responsibilities.One of the earliest applications for automation in librarieswas cataloging. By the 1960s, the ever-increasing volumeof books and serials (periodicals) published each year wasplacing a growing burden on the manual cataloging system.Under this system, catalogers at large libraries (and particularlythe Library of Congress) prepared a catalog record foreach new publication. These records were distributed by theLibrary of Congress in the form of catalog card proof slips.These, as well as compiled card images from other libraries,could be used by each library to prepare catalog records forits own holdings.As mid-size computers became more affordable, it becamepracticable for at least large library systems to put their catalogrecords on-line. In 1968, the MARC (Machine ReadableCataloging) standard was first promulgated. A MARC recorduses specific, numbered fields to describe the elements ofa book, such as its catalog card number, main entry, title,imprint, collation (pagination), and subject headings.At first, MARC records were distributed mainly on magnetictape in place of card slips. However, by the late 1970slarge on-line cataloging systems such as OCLC (On-lineCollege Library Center) and RLIN (Research Library InformationNetwork) were enabling libraries to search for anddownload cataloging information in real time, and in turnupload their own original catalog records to the shareddatabase. This greatly reduced redundant cataloging effort.If a library receives a new book, a library assistant cansearch for a preexisting catalog record. The record can thenbe easily modified for local use, such as by adding a callnumber and holdings information. The problem of authorities(standardized entries for names) is also made moremanageable by being able to check entries on-line.By the 1980s, the next logical step was under way: Thecard catalog began to be replaced by a wholly electroniccatalog, enabling library patrons to search the catalog ata terminal. Besides saving money, the on-line catalog alsooffers researchers many more ways to search for materials:for example, they can use keywords and not rely only ontitles and subject headings.Along with cataloging, libraries began to automate theircirculation and acquisitions systems as well. As these systemsbecome integrated, libraries can both monitor thedemand (finding materials that are in heavy use and need

276 library, programadditional copies) and speed up the supply, by integratingthe acquisitions system with ordering systems maintainedby book distributors.However, while most librarians consider the computer tobe a boon to their profession, there are criticisms and furtherchallenges. Nicholson Baker, for example, has decriedthe abandonment of information in card catalogs that wasnot carried over into electronic form. Baker has also criticizedthe replacement of bound archives of periodicals withmicrofilm, which is often of poor quality and prone to deterioration.The storage of publications on computer mediahas also met with concerns that the physical durabilityof the media has not been sufficiently investigated, andthat in a rapidly changing technological world data formatscan become obsolete, no longer supported, and potentiallyunreadable (see also backup and archive systems).The growth of the World Wide Web has also presentedlibraries with both opportunities and challenges. Catalogersand reference librarians are struggling to find new waysto categorize and retrieve the always-changing and ephemeralcontent of Web pages. Meanwhile, librarians have facednot only funding and training issues in providing expandedpublic Web access in libraries, but have also had to dealwith demands that Web content be filtered to protect childrenfrom objectionable content. (The American LibraryAssociation opposes such filtering as a form of censorship.)Besides being a source of Internet connectivity for studentsand people who cannot afford their own computer,today’s libraries provide a wide variety of media products,including audio CDs, audio and video tapes, and DVDs.Increasingly, though, modern librarians are moving awayfrom the idea of a library as a repository of resources andare placing greater emphasis on providing guidance andstarting points for users who are seeking to navigate theoften-overwhelming Web. Although they face many challenges,libraries seem to be succeeding in the task of reinventingthemselves.Further ReadingAmerican Library Association. Office for Information TechnologyPolicy. Available online. URL: http://www.ala.org/oitp.Accessed August 13, 2007.Baker, Nicholson. Double Fold: Libraries and the Assault on Paper.New York: Vintage Books, 2002.Burke, John J. Neal-Schuman Library Technology Companion: ABasic Guide for Library Staff. 2nd ed. New York: Neal SchumanPublications, 2006.Hanson, Kathlene, and H. Frank Cervone. Using Interactive Technologiesin Libraries (LITA Guide). New York: Neal SchumanPublishers, 2007.Library and Information Technology Association. Available online.URL: http://www.lita.org/ala/lita/litahome.cfm. AccessedAugust 13, 2007.library, programProgramming is a labor-intensive activity, especially whenthe time required to test, debug, and verify the operationof the program code is included. It is not surprising, then,that even the earliest programmers sought ways to reusethe code for commonly needed operations such as dataTo use a program library, the programmer includes the appropriateheader file in the source code. After the source code is compiled, thelinker links it to the compiled object code file corresponding to theheader file, creating a single executable file.input, sorting, calculation, and formatting rather thanwriting it from scratch. If a well-organized collection orlibrary of program routines is available, developers ofnew applications can concentrate on the aspects particularto the current problem and use the library code forroutine operations.In the mainframe world, the use of program librarieswas also mandated by the limited amount of main memoryavailable. A data processing task was often accomplished byretrieving a series of card decks or tapes from the libraryand mounting them in turn. Intermediate results could bepassed between programs under the control of a specialscript (see job control language).Some programming languages, notably C and its descendantsC++ and Java, are designed to provide a small core ofessential features (such as control structures, data types,and operators). Other functions, such as math routines, dataI/O (input/output), and formatting are provided in libraryfiles that are invoked by programs that need particular features.There are several advantages to this approach. The

Licklider, Joseph Carl Robnett 277Licklider, Joseph Carl Robnett(1915–1990)AmericanComputer Scientist, PsychologistDynamic linking is an alternative approach to library use. The programis compiled with a reference to the library, but it is not linkedto the library code until the program is actually running. Since severaldifferent running programs can link to the same dynamic linklibrary (DLL), memory is saved.core language is kept simple because it doesn’t have to dealwith issues such as the actual storage of data in memorythat are dependent on the particular architecture of eachtype of machine. To “port” the language to a new machine,specialists in its architecture can implement the standardlibrary functions. In addition to the standard librariesincluded with the compiler, programmers are also free tocreate additional libraries to support particular applicationssuch as graphics.With a traditional library the library routines invokedin the source code are included in the final executable file.With most modern operating systems, however, many programsare active in memory at the same time (see multitasking).Storing the same commonly used routines(such as standard I/O) with each program wastes memory.Therefore, operating systems such as Microsoft Windowsuse dynamic linking. This means that instead of compilingthe library code into the program to create the executablefile, the program links to the library at execution time.If another program is using the library, the new programlinks to the same copy in memory rather than having tostore another copy. (Dynamically linked libraries [DLLs]include special code to keep track of the invocation of thelibrary functions by each separate program.)Further ReadingJosuttis, Nicolai M. The C++ Standard Library: A Tutorial and Reference.Upper Saddle River, N.J.: Addison-Wesley, 1999.Loosemore, Sandra, et al. GNU C Library Application Fundamentals.Boston: GNU Press, 2004.———. et al. GNU C Library System & Network Applications. Boston:GNU Press, 2004.Lundh, Fredrik. Python Standard Library. Sebastapol, Calif.:O’Reilly, 2001.Most of the early computer pioneers came from backgroundsin mathematics or engineering. This naturally ledthem to focus on the computer as a tool for computation andinformation processing. Joseph Licklider, however, broughtan extensive background in psychology to the problem ofdesigning interactive computer systems that could providebetter communication and access to information for users.Licklider was born on March 11, 1915, in St. Louis, Missouri.During the 1930s, he attended Washington Universityin St. Louis, earning B.A. degrees in psychology, mathematics,and physics. He then concentrated on psychology forhis graduate studies, earning an M.A. at Washington Universityand then receiving his Ph.D. from the University ofRochester in 1942.While at Rochester, Licklider participated in a studygroup led by Norbert Wiener, pioneer in the new field ofcybernetics, in the late 1940s. This brought him into contactwith emerging computer technology and its excitingprospects for the future. In turn, Licklider’s psychologybackground allowed him a perspective quite different fromthe mathematical and engineering background shared bymost early computer pioneers.Cybernetics emphasized the computer as a system thatcould interact in complex ways with the environment. Licklideradded an interest in human-computer interaction andcommunication. He began to see the computer as a sort of“amplifier” for the human mind. He believed that humansand computers could work together to solve problems thatneither could successfully tackle alone. The human couldsupply imagination and intuition, while the computer providedcomputational “muscle.” Ultimately, according to thetitle of his influential paper, it might be possible to achievea true “Man-Computer Symbiosis.”During the 1950s, Licklider taught psychology at theMassachusetts Institute of Technology, hoping eventually toestablish a full-fledged psychology department that wouldelevate the concern for what engineers call “human factors.”From 1957 to 1962 he also served in the private sector as avice president for engineering psychology at Bolt Beranekand Newman, the company that would become famous forpioneering networking technology.In 1962, the federal Advanced Research Projects Agency(ARPA) appointed Licklider to head a new office focusingon leading-edge development in computer science. Licklidersoon brought together research groups that includedin their leadership three of the leading pioneers in artificialintelligence: John McCarthy, Marvin Minsky, and AllenNewell (see artificial intelligence; McCarthy, John;and Minsky, Marvin). By promoting university access togovernment funding, Licklider also fueled the growth ofcomputer science graduate programs at major universitiessuch as Carnegie Mellon University, University of Californiaat Berkeley, Stanford University, and the MassachusettsInstitute of Technology.

278 linguistics and computingIn his research activities, Licklider focused his effortsnot so much on AI as on the development of interactivecomputer systems that could promote his vision of humancomputersymbiosis. This included time-sharing systems,where many users could share a large computer system,and networks that would allow users on different computersto communicate with one another. He believed that thecooperative efforts of researchers and programmers coulddevelop complex programs more quickly than teams limitedto a single agency or corporation (see also open-sourcemovement).Licklider’s efforts to focus ARPA’s resources on networkingand human-computer interaction would providethe resources and training that would, in the late 1960s,begin the development of what would become the Internet.Licklider spent the last two decades of his career teachingat MIT. Before his death in 1990, he presciently predictedthat by 2000 people around the world would be linked in aglobal computer network.Further Reading“Internet Pioneers: J. C. R. Licklider.” Available online. URL: http://www.ibiblio.org/pioneers/licklider.html. Accessed August 13,2007.Licklider, J. C. R. “Man-Computer Symbiosis.” IRE Transactions onHuman Factors in Electronics, vol. HFE-1, March 4–11, 1960.Available online. URL: http://www.memex.org/licklider.pdf.Accessed August 13, 2007.Licklider, J. C. R., and Robert W. Taylor. “The Computer as aCommunication Device.” Science and Technology, April, 1968.Available online. URL: http://gatekeeper.dec.com/pub/DEC/SRC/publications/taylor/licklider-taylor.pdf. Accessed August13, 2007.Waldrop, M. Mitchell. The Dream Machine: J. C. Licklider and theRevolution That Made Computing Personal. New York: Viking,2001.linguistics and computingThe study of human language and advances in computerscience have been closely intertwined. The field of computationallinguistics uses computer systems to investigate thestructure of natural language. In turn, the area of naturallanguage processing involves the creation of software thatcan apply linguistic principles to process written or spokenhuman language (see natural language processing,language translation software, and speech recognitionand synthesis).As simple low-level instruction codes began to evolveinto complex high-level programming language, languagedesigners had to struggle to give precise, complete, andunambiguous definitions for the language’s structure. Thisis essential for language users to be confident that theirprograms will yield the desired results. It is also importantthat developers trying to implement a language on differenthardware platforms and operating systems have rigorouslanguage specifications so the compiler on the new systemwill produce programs equivalent to those on the systemwhere the language was first developed.When computer scientists turned to linguistics for helpin defining programming languages, they found the workof Noam Chomsky, perhaps the 20th century’s preeminentlinguist, to be particularly helpful. Chomsky developed aconcept of formal language in which grammar could bespecified as a series of rules built up a level at a time.For example, at the lowest level, there is an alphabet fromwhich recognized words are generated. Next there are rulesfor generating phrases (such as a noun phrase consisting ofa noun with optional adjectives and a verb phrase consistingof a verb with optional adverbs). In turn, phrases can becombined to form sentences.Because grammatical structures are created by applyingrules to strings of symbols (words), the result is called agenerative grammar. Chomsky sought to apply this conceptof a “transformational generative grammar” as a universalstructure applicable to all human languages. Meanwhile,computer scientists could use formal grammar rules todefine the valid statements in programming languages (seealso Backus-Naur form). This in turn allows a compilerparser to break down high-level language statements andconvert them into low-level instruction codes that can actuallybe executed by the CPU (see assembler and parsing).As new languages and more powerful hardware gavecomputers increased power to deal with complex systems,computer scientists (and artificial intelligence researchers inparticular) applied themselves to the problem of computerprocessing of human languages. Success in this field mightlead not only to computer systems that humans could communicatewith far more naturally, but also to automatic machinetranslation that could, for example, allow an English speakerand a Chinese speaker to communicate via e-mail.However, developers of natural language systems faceformidable challenges. Most fundamentally, while computersprocess symbols using a restrictive, deterministic procedurethat Chomsky classifies as finite state (see finite statemachine), human languages must be understood usingthe more complex transformational grammar. The languageprocessing system must therefore have rules that cancope with the often ambiguous structure of actual humanspeech. (For example, does the word fly in a given sentencemean an insect, a baseball batted high in the air, or perhapsa zippered opening in one’s trousers?)One way to limit the problem is to deal with a restrictedrealm of discourse. For example, a natural language “frontend” to a database might assume that all input nouns referto entities that exist in the database, such as employees,positions, salaries, and so on. It then becomes a matter oftranslating a query such as “How many employees in thehuman resources department make more than $50,000 ayear” into something like:find quantity (employee.department = “humanresources”) and (employee.salary > 50,000)Understanding unrestricted text such as that foundin newspaper stories is much more complex, since fewerassumptions can be made about the subject of the discourse.Here the AI concept of frames can prove useful. A frame isa sort of script that describes the elements of life’s commonevents or transactions. For example, suppose a newsstory begins “Joe X was arrested yesterday for the murder

Linux 279of Sarah Y. He was arraigned today and bail was denied.” Asystem reading the story might see “arrested” and see that itlinks to an internal frame called “crime.” The crime framemight have slots for “accused person,” “charge,” “victim,”and “custodial status.” The system could then interpret thestory as indicating that Joe is the accused person, murder isthe charge, Sarah is the victim. For the custodial status thesystem might look to another frame called “arraignment”that includes the rule that if bail is allowed and paid, theperson’s status is “released until trial” while if the bail iseither not allowed or not paid, the status is “in custody.”Computational linguistics and natural language processingare likely to be of increasing interest in years tocome. With the World Wide Web bringing the world’s languagesinto more pervasive contact, the ability to translateor automatically summarize Web pages and e-mail willbe very marketable. It is also likely that advanced, secretresearch in the field is also being carried out by organizationssuch as the National Security Agency (NSA), whichmonitor worldwide communications.Further ReadingHausser, Roland. Foundations of Computational Linguistics: Human-Computer Communication in Natural Language. 2nd ed. NewYork: Springer, 2001.Lawler, John. Using Computers in Linguistics: A Practical Guide.New York: Routledge, 1998.“Linguistics, Natural Language, and Computational LinguisticsMeta-Index.” Stanford University Natural Language Processing.Available online. URL: http://www-nlp.stanford.edu/links/linguistics.html. Accessed August 13, 2007.Mitkov, Ruslan. The Oxford Handbook of Computational Linguistics.New York: Oxford University Press, 2005.LinuxLinux is an increasingly popular alternative to proprietaryoperating systems. Its development sprang from two sources.First was the creation of open-source versions of UNIX utilities(see unix) by maverick programmer Richard Stallmanas part of the GNU (“Gnu’s not UNIX”) project during the1980s. Although these tools were useful, the kernel, or basicset of operating system functions, was still missing (see kernel).Starting in 1991, another creative programmer, LinusTorvalds, began to release open-source versions of the UNIXkernel (see Torvalds, Linus). The combination of the kerneland utilities became known as Linux (a combinationof Linus and UNIX), though Stallman and his supportersbelieve that GNU/Linux is a more accurate name.Development and DistributionsAs an open-source product, Linux is continually beingdeveloped by a community of thousands of loosely organizedprogrammers. (The further development of the kernelitself is more closely supervised by Torvalds and a systemof review that he set up.) New versions of the Linux kernelare released frequently, including support (drivers) for newdevices and refinements in other features.A distribution or “distro” is a package consisting of aLinux kernel, standard utilities, and a variety of other softwaresuch as office and graphics programs, Web-relatedThe basic components of a Linux system. A distribution, or “distro,”combines the latest version of the common kernel with a windowmanager, selected software, and, perhaps, custom features.programs, and so on. Some distributions such as Novell andRed Hat are geared toward business use and provide feebasedsupport and consulting (Red Hat spun off Fedora as afree user-supported distribution). One of the most populardistributions as of the mid-2000s is Ubuntu. Named foran African word meaning “humanity toward others” andfunded by millionaire Mark Shuttleworth, Ubuntu combinesa business-oriented component (through CanonicalLtd.) and a large and enthusiastic community of desktopusers from all walks of life.Using LinuxLinux is very versatile and probably runs on more kindsof devices than any other operating system. These includesupercomputer clusters, Web and file servers, desktops(including PCs designed for Windows and Macs), laptops,PDAs, and even a few smart phones. The Linux programmerhas many programming languages and environmentsto choose from, including C++, Java, Perl, PHP, and Ruby.Thousands of open-source programs have been written foror ported to Linux, including OpenOffice.org (a suite comparableto Microsoft Office), databases (such as MySQL),and Apache, the most popular Web server.Although Linux rapidly gained a significant share in serverapplications, early versions of Linux for ordinary desktop

280 LISPA Linux system running Open Office, a full-featured (and free) office software suite (Sun Microsystems)users were criticized as being hard to install and to configurefor various types of hardware. However, current versionsof Linux have an installation experience that is comparableto that of Windows, and such details as disk partitioningand setting up networks can often be handled automatically.(There can still be problems with some devices such as wirelesscards for laptops, but even there things have improvedconsiderably.) A Linux distribution such as Ubuntu is now aviable alternative to Windows unless one has to use certainprograms (such as PhotoShop or many games) that do nothave Linux versions. However, such options as dual-booting,emulation, or virtual machines offer the ability to use bothLinux and Windows on the same machine.Further ReadingHill, Benjamin Mako, et al. The Official Ubuntu Book. 3rd ed. UpperSaddle River, N.J.: Prentice Hall, 2008.Linux.com. Available online. URL: http://www.linux.com/.Accessed September 26, 2007.Linux Journal. Available online. URL: http://www.linuxjournal.com/. Accessed September 26, 2007.Matthew, Neil, and Richard Stones. Beginning Linux Programming.4th ed. Indianapolis: Wrox, 2007.Red Hat. Available online. URL: http://www.redhat.com/. AccessedSeptember 26, 2007.Sery, Pal G. Ubuntu Linux for Dummies. Hoboken, N.J.: Wiley,2007.Siever, Ellen, et al. Linux in a Nutshell. 5th ed. Sebastapol, Calif.:O’Reilly, 2005.Sobell, Mark G. A Practical Guide to Red Hat Linux: Fedora Core andRed Hat Enterprise Linux. 3rd ed. Upper Saddle River, N.J.:Prentice Hall, 2006.Ubuntu. Available online. URL: http://www.ubuntulinux.org/.Accessed September 26, 2007.LISPAs interest in AI (see artificial intelligence) developedin the early 1950s, researchers soon became frustrated bythe low-level computer languages of the day, which emphasizedcomputation and other manipulation of numbersrather than the processing of symbolic data.

LISP 281At the 1956 Dartmouth Summer Research Project onArtificial Intelligence, a gathering that brought together thekey early pioneers in the field, John McCarthy presented hisconcepts for a different kind of computer language. Sucha language, he believed, should be able to deal with mathematicalfunctions in their own terms—by manipulatingsymbols, not just calculating numbers.Together with Marvin Minsky, McCarthy began toimplement a language called LISP (for “list processor”). (SeeMcCarthy, John and Minsky, Marvin.) As the name suggests,the language uses lists to store data (see list processing)and features many functions for manipulatinglist elements. List can consist of single elements (called“atoms”) as in(A B C D)but lists can also include other lists, as in(A (B C) D)Each list item is stored as a “node” containing both a pointerto its data value and a pointer to the next item in the linkedlist. The LISP system typically includes housekeeping functionssuch as “garbage collection,” where the memory fromdiscarded list items is returned to the free memory pool forlater allocation.LISP programs look forbidding at first sight because theytend to have many nested parentheses. However, expressionsand functions are actually constructed in a much simplerway than in most other languages. Without the needfor complicated parsing, the LISP interpreter (called “eval”because it evaluates its input) looks at the stream of dataand first asks whether the next item is a constant (such as anumber, quoted symbol, string, quoted list, or keyword). Ifso, its value is returned. Otherwise, the interpreter checksto see if the item is a defined variable and, if so, returns itsvalue. Finally, the interpreter checks to see if there is a list.If so, the list is considered to be a function call followed byits arguments. The function is called, given the data, andthe result is returned.The following table shows some items in a list programand how the interpreter will evaluate them:Examples of Lisp ItemsType of Item Example Evaluationinteger 24 24float 5.5 5.5ratio 3/4 0.75keyword defun defines functionquoted integer ’24 24quoted list ’(3 1 4 1 5) (3 1 4 1 5)boolean nil falsefunction call +2 4 6variable a its valuequoted variable ’a aLanguages such as Algol, Pascal or C emphasize statementsand procedures. LISP, on the other hand, was thefirst functional language (see functional languages).The heart of a LISP program is functions that are evaluatedtogether with their arguments. LISP includes many builtin,or primitive functions. Besides the usual mathematicaloperations, there are primitives for basic list-processingfunctions. For example, the list function creates a list fromits arguments: (list 1 2 3) returns the list (1 2 3), while thecons function inserts an atom into the beginning of a list,and the append function tacks it onto the end. Programmersdefine their own functions using the defun keyword.LISP has two other features that make it a powerfuland flexible language for manipulating symbols and data.LISP allows for recursive functions (see recursion). Forexample, the following function raises a variable x to thepower y:(defun power (x y)(if (= y 0) 1(* x (power x (1– y)))))Here the if expression checks to see whether y is 0. Ifnot, the second expression invokes the function (power)itself, which performs the same test. The result is that thefunction keeps calling itself, storing temporary values, untily gets down to 0. It then “winds itself back up,” multiplyingx by itself y times.But perhaps the most interesting feature of LISP is thatit makes no distinction between programs (functions) anddata. Since a function call and its arguments themselvesconstitute a list, a function can be fed as data to other functions.This makes it easy to write programs that modifytheir own operation.Language DevelopmentLISP quickly caught on with artificial intelligence researchers,and the version called LISP 1.5 was considered robustenough for writing large-scale applications. While “mainstream”computer scientists often used Algol and its descendantsas a universal language for expressing algorithms,LISP became the lingua franca for AI people.However, a number of dialects such as Mac-LISP divergedas versions were written to support new hardware or werepromoted by companies such as LMI and Symbolics. Whileresearchers liked the interactive nature of interpreted LISP(where functions could be defined and immediately tried outat the keyboard), practical applications required compilationinto machine language to achieve adequate speed.A widely used LISP variant is Scheme, developed byMIT researchers in the mid-1970s. Scheme simplifies LISPsyntax (while still preserving the spirit), and at the sametime generalizes further by allowing functions to have allthe capabilities of data entities. That is, functions can bepassed as parameters to other functions, returned as values,and assigned to variables and lists.By the 1980s, personal computers became powerfulenough to run LISP, and the proliferation of LISP variantsrunning on different platforms led to a standardization movementthat resulted in Common LISP in 1984. Common LISPcombines the features of many existing dialects, includes

282 list processinga rich variety of data types, and also makes greater allowancefor the imperative, sequential programming approach oflanguages such as C. It thus accommodates varying styles ofprogramming. It is widely available today in both commercialand shareware versions.Seymour Papert created a LISP-like language calledLogo, which has been used to teach sophisticated computerscience ideas to young students (see logo).Further ReadingDybvig, R. Kent. The SCHEME Programming Language. 3rd ed.Cambridge, Mass.: MIT Press, 2003.“Lisp Information and Resources.” Available online. URL: http://www.lispmachine.net/. Accessed August 13, 2007.Queinnec, Christian. Lisp in Small Pieces. New York: CambridgeUniversity Press, 1996.Seibel, Peter. Practical Common Lisp. Berkeley, Calif.: Apress, 2005.list processingA list is a series of data items that can be accessed sequentiallyby following links from one item to the next. Listscan be very useful for ordering or sorting data items and forstoring them on a stack or queue.There are two general approaches to constructing lists.In a data list used with procedural programming languagessuch as C, each list item consists of a structure consistingof a data member and a pointer. The pointer, called “next,”contains the address of the next item. A program can easily“step through” a list by starting with the first item, processingits data, then using the pointer to move to the nextitem, continuing until some condition is met or the end ofthe list is reached.A singly linked list. Each node (item) includes a value and apointer to the next node. Inserting a new node is simply a matter ofadjusting the pointer of an existing node to point to the new node,with the new node’s pointer in turn pointing to the next item (or theend of the list). A node is removed by disconnecting its pointer.A doubly linked list. Each node has two pointers, one to the nextitem and one to the prior (preceding) item. While doubly linkedlists use more memory, they can be processed more quickly becausethey can be traversed in either direction.In LISP-type languages, however, a more general structureis used, since essentially all data is part of a list. Hereeach item is a node that can contains a pointer to any validobject and a pointer to the next node. One advantage of thisscheme is that since fixed-length data fields are not used,the list can be “hooked up” to objects of varying sizes andtypes. This can also use memory more efficiently, though atthe cost of additional processing being needed to periodicallyreclaim memory (“garbage collection”).Besides traversing (stepping through) a list by followingits “next” pointer, the basic list-processing operationsare insertion and deletion. It is easy to insert a new elementinto a list: You first move to the item after which the newitem is to be inserted. Next, you connect that item’s “next”pointer (link) to the new item. You then connect the newitem’s next link to the item that originally followed theinsertion point. Deleting an item is even simpler: You “snipout” the item by connecting the item that originally linkedto it to the item that was originally after it.Sometimes lists are set up so that each item has twopointers: one to the next item and one to the previous one.Such doubly linked lists can be traversed in either direction,making retrieval faster in some situations, though at the costof storing the extra pointers. Lists are also used to implementsome specialized data structures (see stack and queue).ApplicationsLists are generally used to provide convenient access to relativelysmall amounts of data where flexibility is required.Unlike an array, a list need use only as much memory as itneeds to accommodate the current number of items (includingtheir associated pointers). A LISP-style node list can beeven more flexible in that items with varying sizes andtypes of data can be included in the same list. Lists are thusa more flexible way to implement such things as look-uptables. (See also array.)Further ReadingCovington, Michael A. “Some Recursive List Processing Algorithmsin Lisp.” Available online. URL: http://www.ai.uga.

local area network 283edu/mc/LispNotes/RecursiveListProcessingAlgorithmsIn-Lisp.pdf. Accessed August 13, 2007.“Linked List Basics [In C/C++]” Available online. URL: http://cslibrary.stanford.edu/103/LinkedListBasics.pdf. AccessedAugust 13, 2007.Seibel, Peter. “They Called It LISP for a Reason: List Processing.”Available online. URL: http://www.gigamonkeys.com/book/they-called-it-lisp-for-a-reason-list-processing.html. AccessedAugust 13, 2007.local area network (LAN)Starting in the 1980s, many organizations sought to connecttheir employees’ desktop computers so they could sharecentral databases, share or back up files, communicate viae-mail, and collaborate on projects. A system that linkscomputers within a single office or home, or a larger areasuch as a building or campus, is called a local area network(LAN). (Larger networks linking branches of an organizationthroughout the country or world are called wide areanetworks, or WANs. See network.)A Token Ring network connects the machines in a “chain” aroundwhich messages called tokens travel. Any PC can “grab” a passingtoken and attach data and the address of another PC to it. Each PCin turn watches for tokens that are addressed to it.The Star network configuration uses a central hub to which eachPC is attached. To extend the network (such as into other offices),the hubs can be connected to one another so they function asswitches. When a token arrives that is addressed to one of its PCs,the hub will route it to the appropriate machine.Hardware ArchitectureThere are two basic ways to connect computers in a LAN.The first, called Ethernet, was developed by a project at theXerox Palo Alto Research Center (PARC) led by Robert Metcalfe.Ethernet uses a single cable line called a bus to whichall participating computers are connected. Each data packetis received by all computers, but processed only by the oneit is addressed to. Before sending a packet, a computer firstchecks to make sure the line is free. Sometimes, due to thetime delay before a packet is received by all computers,another computer may think the line is free and start transmitting.The resulting collision is resolved by having bothcomputers stop and wait varying times before resending.Because connecting all computers to a single bus line isimpractical in larger installations, Ethernet networks arefrequently extended to multiple offices by connecting a busin each office to a switch, creating a subnetwork or segment(this is sometimes called a star topology). The switches arethen connected to a main bus. Packets are first routed tothe switch for the segment containing the destination computer.The switch then dispatches the packet to the destinationcomputer. Another advantage of this switched Ethernetsystem is that more-expensive, high-bandwidth cable canbe used to connect the switches to move the packets morequickly over greater distances, while less-expensive cablingcan be used to connect each computer to its local switch.An alternative way to arrange a LAN is called tokenring. Instead of the computers being connect to a bus thatends in a terminator, they are connected in a circle wherethe last computer is connected to the first. Interference isprevented by using a special packet called the token. Likethe use of a “talking stick” in a tribal council, only thecomputer holding the token can transmit at a given time.After transmitting, the computer puts the token back intocirculation so it can be grabbed by the next computer thatwants to send data.LAN SoftwareNaturally there must be software to manage the transmissionand reception of data packets. The structure of a packet(sometimes called a frame) has been standardized with apreamble, source and destination addresses, the data itself,

284 Logoa checksum, and two special layers that interface with thediffering ways that Ethernet and token ring networks physicallyhandle the packets.The low-level processing of data packets must also beinterfaced with the overall operating system so that, forexample, a user on a desktop PC can “see” folders and fileson the file server and whole files can be transferred betweenserver and desktop PC. From the 1980s to the mid-1990sthe most common LAN operating system for DOS and laterWindows-based PCs was Novell Netware, while Macintoshusers used AppleTalk. Later versions of Windows (notablyWindows NT) then incorporated their own networkingsupport, and Netware use declined somewhat.The tremendous popularity of the Internet (particularlythe Web) starting in the mid-1990s propelled the Internetprotocol (see tcp/ip) into the forefront of networking.Today’s business and home computers use essentially thesame tools to connect to the global Internet and to oneanother. (The term Intranet, once used to distinguish localTCP/IP networks from the Internet, is now pretty muchobsolete.)Meanwhile, the technologies used to implement thisuniversal networking have proliferated. While the Internetis most commonly delivered to homes and businessesvia wires (see cable modem and dsl), wireless networkinghas replaced cable for many local networks, including mosthome networks (see Wireless and mobile computing),with the hub of the network being an inexpensive routerand wireless access point.Further ReadingBriere, Danny, Pat Hurley, and Edward Ferris. Wireless Home Networkingfor Dummies. Hoboken, N.J.: Wiley Publishing, 2006.Komar, Brian. Sams Teach Yourself TCP/IP Networking in 21 Days.2nd ed. Indianapolis: Sams, 2002.Lowe, Doug. Networking for Dummies. Hoboken, N.J.: Wiley Publishing,2007.Spurgeon, Charles. Ethernet: The Definite Guide. Sebastapol, Calif.:O’Reilly Media, 2000.Tittel, Ed, Earl Follis, and James E. Gaskin. Networking with Net-Ware for Dummies. 4th ed. Foster City, Calif.: IDG Books,1998.LogoLogo is a derivative of LISP (see lisp) that preserves much ofthat language’s list processing and symbolic manipulationpower while offering simpler syntax, easier interactivity,and graphics capabilities likely to appeal to young people.Logo has often been used as a first computer language forstudents in elementary and junior high school grades. AsHarold Abelson noted in his Apple Logo primer in 1982,“Logo is the name for a philosophy of education and a continuallyevolving family of programming languages that aidin its realization.”Logo was developed starting in 1967 by educator SeymourPapert and his colleagues at Bolt, Beranek and Newman,Inc. Papert, a mathematician and AI pioneer, hadbecame interested in devising an education-oriented computerlanguage after working with developmental psychologistJean Piaget. Papert focused particularly on Piaget’semphasis on “constructivism”—the idea that people learnmainly by fitting new concepts into an existing frameworkbuilt from the experience of daily life. Papert came tobelieve that abstract computer languages such as FORTRANor even BASIC were hard for children to assimilate becausetheir algebraic formulas and syntax had little in commonwith daily activities such as walking, playing, drawing, ormaking things.For example, most computer languages implementgraphics using statements that specify screen points usingCartesian coordinates (X, Y). A square, for example, mightbe drawn by statements such as:PLOT 100, 100LINETO 150, 100LINETO 150, 150LINETO 100, 150LINETO 100, 100While familiarity with the coordinate system eventuallyallows one to visualize this operation, it is far from intuitive.Papert, however, includes a “turtle” in his Logo language.The turtle was originally an actual robot that couldbe programmed to move around; in most systems today it isrepresented by a cursor on the screen. As the turtle moves,it uses a “pen” to leave a “trail” that draws the graphic.With turtle commands, a square can be drawn by:FD 50 (that is, forward 50)RT 90 (turn right 90 degrees)FD 50RT 90FD 50RT 90FD 50RT 90Here, the student programmer can easily visualize walkingand turning until he or she arrives back at the startingpoint. In keeping with Piaget’s theories, the learning is congruentwith the physical world and daily activities.Logo includes control structures similar to those inother languages, so the above program can be rewritten assimply:REPEAT 4 [FD 50 RT 90]Logo is much more than a set of simple drawing commands,however. Students can also be encouraged to use thelist-processing commands to create everything from computer-generatedpoetry to adventure games. Unlike LISP’sobscurely named commands such as car and cdr, Logo’s listcommands are readily understandable. For example, firstreturns the first item in a list, while butfirst returns all ofthe list except the first item.Logo procedures are introduced by the to keyword,implying that the programmer is “teaching the computer”how to do something. For example, a procedure to draw asquare with a variable size and starting position might looklike this:

loop 285to square :X :Y :Sizesetxy :X :Yrepeat 4 [fd :Size rt 90]endLogo has been steadily enhanced over the years, andincludes not only a full set of math functions, but also manyversions include special sound, graphics, and multimedia functionsfor Windows or Macintosh systems. By the mid-1980s,Logo had been combined with the popular LEGO buildingtoy to create LEGO Logo. This popular kit enables students tobuild and control a variety of robots and other gadgets.By the 1990s, Logo had to some extent become a casualtyto the pressure on educators to provide “real world”programming skills using languages such as C++ or Java.However, Logo using educators have continued to flourishin parts of Europe, Japan, and Latin America. Logo has alsobeen energized by the development of two recent versions.MicroWorlds Logo took advantage of the Macintosh interfaceto provide a full-featured multimedia environment,and it was later adapted for Windows systems. Anotherversion, StarLogo, emphasizes parallel processing concepts,and is able to control thousands of separate turtles that canbe programmed to simulate behaviors such as bird flocks ortraffic flows. As Brian Harvey’s books show, Logo’s accessible,interactive nature continues to make it a good choicefor teaching computer science to adults as well.Further ReadingHarvey, Brian. Computer Science Logo Style. Vols. 1–3, 2nd ed.Cambridge, Mass.: MIT Press, 1997.LCSI Microworlds. Available online. URL: http://www.microworlds.com/. Accessed August 13, 2007.Logo Foundation (MIT). Available online. URL: http://el.media.mit.edu/Logo-foundation/. Accessed August 13, 2007.Papert, Seymour. Mindstorms: Children, Computers, and PowerfulIdeas. New York: Basic Books, 1993.“StarLogo on the Web.” MIT Dept. of Education. Available online.URL: http://education.mit.edu/starlogo/. Accessed August 13,2007.“Welcome to MSWLogo.” Available online. URL: http://www.softronix.com/logo.html. Accessed August 13, 2007.This loop first checks to see whether the end of the inputfile (opened earlier) has been reached. If not, it reads andprocesses a record (using procedures defined elsewhere).The “Wend” marks the end of the statements controlled bythe loop. When the end of the file is reached, the test fails(returns false) and control skips to the statement followingWend. See the accompanying flowchart for a visual depictionof the operation of this loop.A variant form of while loop performs the test afterexecuting the enclosed instructions. For example:DoPrint “Enter a number: “Input NumberPrint “You entered: “;NumberWhile (Number 0)Print “I’m Done!”This loop will display each number the user enters, thentest it for zero. After a zero is encountered, control will skipto the final print statement.Note that because this second form of while loop doesnot perform the test until it has performed the specifiedactions at least once, it would not be appropriate for thefirst example. In that case, the loop would attempt to get arecord before discovering it had reached the end of the file,and an error would result.The for loop is useful when an action is to be repeatedfor each of a limited series of cases. For example, this loopwould print out the ASCII characters corresponding to thecodes from 32 through 65:For CharVal = 32 to 65 Step 1Print Char$(CharVal)loopIf computers were merely fast sequential calculators, theywould still be of some use. However, much of the power ofthe computer comes from its ability to carry out repetitivetasks without supervision. The loop is the programminglanguage structure that controls such activities. Virtuallyevery language has some form of loop construct, with variationsin syntax ranging from the relatively English-likeCOBOL and Pascal to the more cryptic C. We will useBASIC for our examples, since its syntax is easy to read.The standard while loop performs the specified actionsas long as the specified condition is true. For example:While NOT EOF (Input_File)Read_RecordProcess_RecordWendPrint “Done!”Flowchart for a loop that reads and processes records until itreaches the end of the file. Programmers must make sure that theend condition of a loop is properly defined, or the loop may runendlessly, “hanging” the program.

286 LuaNext CharValHere Char$ is a function that output the character correspondingto the supplied ASCII character code. The stepclause specifies the interval over which the variable withinthe loop is to be incremented. Here it’s not strictly necessary,since it defaults to 1.Loops of all sorts can be “nested” so that an inner loopexecutes completely for each step of the outer loop. Forexample:For Vertical = 0 to 767For Horizontal = 0 to 1023Print_Pixel (Vertical, Horizontal)Next HorizontalNext VerticalHere the program will move across each line of thescreen, printing the contents of each pixel. Each time theinner loop finishes, the outer loop increments, moving thescanning down to the next line. Indention is used to makethe relation between the outer and inner loops clear.In programming loops it’s important to frame the testconditions correctly so that they terminate appropriately.An “endless loop” can cause a program to “hang” indefinitely.However, some programs do code an endless outerloop to indicate the program is to run indefinitely unlessclosed by the operating system. For example, the loopWhile (1)’ Instructions go hereWendwill execute indefinitely, since the value one is equivalentto “true.”Since many programs spend most of their time repeatedlyexecuting loops, programmers seeking to improvethe performance of their code pay especial attention to thecode within the body of a loop. Any code such as a variableassignment, conversion, or calculation that needs to bedone only once should be moved outside the loop.Further Reading“Control Flow.” Wikipedia. Available online. URL: http://en.wikipedia.org/wiki/Control_flow. Accessed August 13,2007.Sebesta, Robert W. Concepts of Programming Languages. 8th ed.Boston: Addison-Wesley, 2007.LuaLua is a scripting language created by three programmers atthe Pontifical University of Rio de Janeiro, Brazil. (The wordLua is Portuguese for “Moon”). The language has begun toattract some attention, particularly among game and Webprogrammers.Lua has simple syntax and can support both traditional(imperative) programming and functional programming(see functional languages). Many of the features such asinheritance and name spaces that are built into most objectorientedlanguages are not part of Lua, but can be createdthrough the language’s extension methods (see object-orientedprogramming).A simple function in Lua looks like this:function factorial(n)if n = 0 thenreturn 1endreturn n * factorial(n - 1)endNote the lack of required semicolons.Besides a simple assortment of built-in types, Lua usestables to create complex, user-defined types. Tables includepairs of values and keys. The key can either be a number(creating the equivalent of an array in other languages), ora string. For example, the following table consists of threevalues indexed by strings:coin = { quarter = 25, dime = 10, nickel = 5,penny = 1 }printer (coin[“dime”]) -- prints 10By including functions and the data they use into atable, classes similar to those used in object-oriented languagescan also be created.Implementation and UseLua programs are compiled to an intermediate form (bytecode)that runs on a Lua virtual machine for each platform.Lua is intended to work closely with C programs, transferringdata via a stack.Because of its compact runtime packages, Lua is oftenincluded in applications to provide an interface for editingor extending the application. This is particularly true ofgames such as World of Warcraft.Further ReadingIerusalimschy, Roberto. Programming in Lua. 2nd ed. Rio deJaneiro, Brazil: Lua.org, 2006.Jung, Kurt, and Aaron Brown. Beginning Lua Programming. Indianapolis:Wiley, 2007.Lua.org. Available online. URL: http://www.lua.org. Accessed September26, 2007.

MMacintoshSince its inception in 1984, Apple’s Macintosh line of personalcomputers has offered a distinctive, innovative alternativeto the more mainstream IBM-compatible PCs. When theMacintosh came out, it was billed as the computer “for therest of us.” Unlike the text-based, command-driven DOSbasedIBM PC and its “clones,” the “Mac” offered an interfacethat consisted of menus, folders, and icons that couldbe manipulated by clicking and dragging (see user interfaceand mouse). The system came out of the box with apaint/draw program and a word processor that could showdocuments using the actual font sizes and styles that wouldappear in printed text. This “WYSIWYG” (What You See IsWhat You Get) feature quickly made the Mac the machineof choice for desktop publishers and graphic artists. TheMac also met with some success in the educational market,where the way had been paved by the earlier Apple II.However, there were factors would limit the Macto a minority market share. The first models ran slowly.Although its Motorola 68000 processor was comparable tothe Intel 80286 used by the IBM XT and AT series, the needto draw extensive graphics placed a heavier burden on theMac’s CPU.Marketing decisions also proved to be problematic. TheIBM PC had an “open architecture.” Clone makers were ableto legally produce machines that were functionally equivalent,and Microsoft was able to license to clone manufacturersessentially the same DOS operating system that IBMused. This created a robust market as manufacturers competedwith added features or lower prices.Apple, on the other hand, jealously guarded the Apple’shardware and the ROM (read only memory) that held thekey operating system code. Apple made only a brief andhalf-hearted attempt to license the Mac OS to third partiesin 1995, and by then it was probably too late. Apple CEOSteve Jobs (see Jobs, Steve) kept prices relatively high, bettingthat the Mac’s unique operating system and interfacewould entice people to buy the more expensive machine.But something of a vicious circle set in. Since the Macused a unique operating system, developing new applications(or porting existing ones) to the Mac was expensive.And since the Mac market represented only a small fractionof the PC-compatible market, developers were reluctant tocreate such software. Some flagship products such as AldusPageMaker and Adobe Photoshop did cater to the Mac’sgraphic strengths. In general, however, the PC-compatibleowner had a far wider range of software to choose from,and businesses were traditionally more comfortable withIBM equipment, even if IBM didn’t make it.Microsoft helped develop some successful Mac software,including versions of its Word and Office programs. ButMicrosoft CEO Bill Gates responded to the Mac’s interfaceadvantages over MS-DOS by developing a new operatingenvironment, Windows. Apple sued, claiming that Microsofthad gone beyond the license it had negotiated withApple for use of elements of the Mac interface. By the early1990s, however, Apple had lost the lawsuit. While the earlyversions of Windows were clumsy and met with little success,version 3.0 and, later, Windows 95 succeeded in providinga user experience that was increasingly close to thatachieved by the Mac.287

288 macroMacDailyNews. Available online. URL: http://www.macdailynews.com/. Accessed August 14, 2007.Mac Observer. Available online. URL: http://www.macobserver.com/. Accessed August 14, 2007.Macworld: The Mac Experts. Available online. URL: http://www.macworld.com/. Accessed August 14, 2007.Pogue, David, and Adam Goldstein. Switching to the Mac: The MissingManual, Tiger Edition. Sebastapol, Calif.: O’Reilly Media,2005.A Power Mac G5 with a 30-inch Apple Cinema HD display. (AppleComputer)Apple kept trying to innovate and carve out a largermarket share, designing both Power Macs that used thePowerPC RISC (reduced instruction set) microprocessorand PowerBook laptops. Toward the end of the 1990s, Appletried to address the low end of the market with the iMac, acolorful, sleek machine packed with features such as homevideo editing, and achieved modest success in attractingnew customers.New Insides, New Directions?In 2000 Apple began to revamp what was becoming a somewhataging architecture. First came the replacement of theoperating system with a UNIX variant (see unix) whileretaining the user interface (see os x). In 2006 Apple beganto transition the Mac’s processor from the Motorola/IBMPower PC to the Intel chips that power Windows-compatiblePCs. The use of a widely available chip (and provisionfor Windows via the “Boot Camp” utility) may make theMac cheaper and more attractive to mainstream PC users.Meanwhile the Macintosh OS X operating system continuedto evolve from the “Tiger” edition to “Leopard,” released inFall 2007.While the Mac continues to be a niche market, saleshave been strong, increasing steadily each year. However,in recent years the Mac has been overshadowed somewhatas an Apple icon, supplanted by the iPod and in 2007 by theiPhone.Further ReadingLevy, Steven. Insanely Great: The Life and Times of Macintosh, theComputer that Changed Everything. New York: Penguin, 2000.Litt, Samual A., et al. Mac OS X Bible, Tiger Edition. Indianapolis:Wiley, 2005.macroFor both programmers and ordinary users, the ability to“package” a group of instructions so that it can be invokedwith a single command can save a lot of effort. The termmacro is used for such instruction packages in a variety ofcontexts.In the early days, programmers had to work with lowlevelmachine instructions (see assembler). Developerssoon realized that a program could be used to write otherprograms. This program, called a macro assembler, lets theprogrammer write a group of instructions such as:COMPARE macroLOAD %1 ‘ load first data itemSTOREX ‘ store in register XLOAD %2 ‘ load second data itemSTOREY ‘ store in register YCMPXY ‘ compare X and Y registersendmNow, if the programmer wants to compare the contentsof two memory locations (say COUNTER and LIMIT), he orshe can write simply:COMPARE COUNT LIMITThe assembler replaces COMPARE with the sequence ofinstructions above, substituting COUNT and LIMIT for %1and %2.Macros are also used in some higher-level languages,notably C. A module called the macro processor performsthe required substitutions into the source code before thecode is parsed and compiled. For example, a C programmermight include this macro in a program file:#define IS_LOWERCASE(x) (( (x)>=‘a’) && ((x) =‘a’) && ((Letter)

Maes, Pattie 289ing coding. However, a given procedure appears in the codeonly once, although it may be called upon from many differentparts of the program. A macro, on the other hand, is not“called.” Each time it is mentioned, the macro is replaced bythe corresponding instructions. Thus macros increase thesize of the source code.Many programmers today prefer using functions withthe appropriate code rather than macros. Using functionssaves space, since each function’s code need only appearonce. Although there is some processing overhead at runtimein calling the function, the function approach alsoensures that the data sent to the function will be checked tomake sure it is of the proper type. The macro, on the otherhand, usually leaves it up to the programmer to make surethe data type being used is appropriate.Application MacrosThe term macro is also used with applications software.Here it can mean a series of commands (such as cursor positioningor text formatting) that are recorded and assignedto a certain key combination. For example, a word processoruser might define a macro called Letter and record thekeystrokes and/or mouse movements needed to open a newdocument, insert a letterhead from a file, update the date,insert a salutation, and position the cursor to continue writingthe letter. The recorded keystrokes might be assigned tothe key combination Control + L.More elaborate macros can be written to automate complextasks in spreadsheets and word processors. Microsoftprovides an entire language, Visual Basic for Applications(VBA), for writing macros for its Office products.Further ReadingGonzalez, Juan Pablo, et al. Office VBA Macros You Can Use Today:Over 100 Amazing Ways to Automate Word, Excel, PowerPoint,Outlook and Access. Uniontown, Ohio: Holy Macro! Books,2005.Jelen, Bill. VBA and Macros for Microsoft Office Excel 2007. Indianapolis:Que, 2007.Kochan, Stephen. Programming in C. 3rd ed. Indianapolis: Sams,2004.“Preprocessor Directives.” Available online. URL: http://www.cplusplus.com/doc/tutorial/preprocessor.html. AccessedAugust 14, 2007.Maes, Pattie(1961– )Belgian/AmericanComputer ScientistPattie Maes is a pioneer in the creation of software agents,intelligent programs that work with people to help themfind what they need online, whether it is relevant newsstories, a vacation itinerary, or a good place for a romanticdinner for two in San Francisco.Born June 1, 1961, in Brussels, Belgium, Maes was interestedin science (particularly biology) from an early age.She received bachelor’s (1983) and doctoral (1987) degreesin computer science and artificial intelligence from the Universityof Brussels.In 1989 Maes moved from Belgium to the MassachusettsInstitute of Technology, where she joined the ArtificialIntelligence Lab. There she worked with an innovativeresearcher who had created swarms of simple but intriguinginsectlike robots (see Brooks, Rodney). Two years laterMaes became an associate professor at the MIT Media Lab,famed for innovations in how people interact with computertechnology (see MIT Media Lab). There she foundedthe Software Agents Group to promote the development of anew kind of computer program.These programs (see software agent) have considerableautonomy and intelligence. Like a human travel or realestate agent, an agent program must have detailed knowledgeof the appropriate area of expertise; the ability to askthe client questions about preferences, priorities, and constraints;and the ability to find the best deals and negotiatewith service providers.Maes’s goal has been to create software agents who thinkand act much like their human counterparts. To carry outa task using an agent, the user does not have to specifyexactly how it is to be done. Rather, the user describes thetask, and the software engages in a dialog with the user toobtain the necessary guidance.A software travel agent would know—or ask about—such things as how much the user wants to spend andwhether he or she prefers sites involving nature, history, oradventure. It would also ask about and take into considerationconstraints of budget, travel time, comfort, and so on.The software agent would then use its database and proceduresto put together an itinerary based on the user’s needsand desires. It would not only know where to find the bestfares and rates, it would also know how to negotiate withhotels and other services. Indeed, it might negotiate withtheir software agents.In 1995 Maes cofounded Firefly Networks, a companythat attempted to create commercial applications for softwareagent technology. Although the company was boughtby Microsoft in 1998, one of its ideas—“collaborative filtering”—canbe experienced by visitors to sites such as Amazon.com.Users in effect are given an agent whose job it is toprovide recommendations for books and other media. Therecommendations are based upon observing not only whatitems the user has already purchased, but also what elsehas been bought by people who bought those same items.More advanced agents can also tap into feedback resourcessuch as user book reviews on Amazon or auction feedbackon eBay (see social networking).A listing of Maes’s current research projects at MIT conveysmany aspects of and possible applications for softwareagents. These include the combining of agents with interactivevirtual reality, using agent technology to create charactersfor interactive storytelling, the use of agents to matchpeople with the news and other information they are mostlikely to be interested in, an agent that could be sent into anonline market to buy or sell goods, and even a “Yenta” agentthat would introduce people who are most likely to make agood match.

290 mainframeMaes has participated in many high-profile conferencessuch as AAAI (American Association for Artificial Intelligence)and ACM Siggraph, and her work has been featuredin numerous magazine articles. She was one of 16 modern“visionaries” chosen to speak at the 50th anniversary of theACM. She has also been repeatedly named by Upside magazineas one of the 100 most influential people for developmentof the Internet and e-commerce. Time Digital featuredher in a cover story and selected her as a member of its“cyber elite.” Newsweek put her on its list of 100 Americansto be watched for in the year 2000. That same year the MassachusettsInteractive Media Council gave her its LifetimeAchievement Award.Further ReadingD’inverno, Mark, and Michael Luck, eds. Understanding Agent Systems.2nd. ed. New York: Springer Verlag, 2003.Maes, Pattie. “Intelligence Augmentation: A Talk with PattieMaes.” Available online. URL: http://www.edge.org/3rd_culture/maes./ Accessed May 5, 2007.Software Agents group at MIT Media Lab. http://agents.mit.edu.Accessed May 5, 2007.mainframeIn the era of vacuum tube technology, all computers werelarge, room-filling machines. By the 1960s, the use of transistors(and later, integrated circuits), enabled the productionof smaller (roughly, refrigerator-sized) systems (seeminicomputer). By the late 1970s, desktop computers werebeing designed around newly available computer chips (seemicroprocessor). Although they, too, now use integratedcircuits and microprocessors, the largest scale machines arestill called mainframes.The first commercial computer, the UNIVAC I (see Eckert,J. Presper and Mauchly, John) entered service in1951. These machines consisted of a number of large cabinets.The cabinet that held the main processor and mainmemory was originally referred to as the “mainframe”before the name was given to the whole class of machines.Although the UNIVAC (eventually taken over by SperryCorp.) was quite successful, by the 1960s the quintessentialmainframes were those built by IBM, which controlledabout two-thirds of the market. The IBM 360 (and in the1970s, the 370) offered a range of upwardly compatible systemsand peripherals, providing an integrated solution forlarge businesses.Traditionally, mainframes were affordable mainly bylarge businesses and government agencies. Their mainapplication was large-scale data processing, such as thecensus, Social Security, large company payrolls, and otherapplications that required the processing of large amountsof data, which were stored on punched cards or transferredto magnetic tape. Programmers typically punched theirCOBOL or other commands onto decks of punched cardsthat were submitted together with processing instructions(see job control language) to operators who mountedthe required data tapes or cards and then submitted theprogram cards to the computer.By the late 1960s, however, time-sharing systems allowedlarge computers to be partitioned into separate areas so thatthey can be used by several persons at the same time. Thepunched cards began to be replaced by Teletypes or videoterminals at which programs or other commands could beentered and their results displayed or printed. At aboutthe same time, smaller computers were being developed byDigital Equipment Corporation (DEC) with its PDP series(see minicomputer).With increasingly powerful minicomputers and later,desktop computers, the distinction between mainframe,minicomputer, and microcomputer became much less pronounced.To the extent it remains, the distinction today ismore about the bandwidth or amount of data that can beprocessed in a given time than about raw processor performance.Powerful desktop computers combined into networkshave taken over many of the tasks formerly assignedto the largest mainframe computers. With a network, evena large database can be stored on dedicated computers (seefile server) and integrated with software running on theindividual desktops.Nevertheless, mainframes such as the IBM System/390are still used for applications that involve processing largenumbers of transactions in near real-time. Indeed, manyof the largest e-commerce organizations have a mainframeat the heart of their site. The reason is that while the rawprocessing power of high-end desktop systems today rivalsthat of many mainframes, the latter also have high-capacitychannels for moving large amounts of data into and out ofthe processor.Early desktop PCs relied upon their single processor tohandle most of the burden of input/output (I/O). AlthoughPCs now have I/O channels with separate processors (seebus), mainframes still have a much higher data throughput.The mainframe can also be easier to maintain than anetwork, since software upgrades and data backups canbe handled from a central location. On the other hand, aThe IBM System/360 was the most successful mainframe in computerhistory. It was actually a “family” of upwardly compatiblemachines. (IBM Corporate Archives)

management information system 291system depending on a single mainframe also has a singlepoint of vulnerability, while a network with multiple mirroredfile servers can work around the failure of an individualserver.Further ReadingButler, Janet G. Mainframe to Client-Server Migration: StrategicPlanning Issues and Techniques. Charleston, S.C.: ComputerTechnology Research Corporation, 1996.Ebbers, Mike, Wayne O’Brien, and Bill Ogden. Introduction to theNew Mainframe: z/OS Basics. Raleigh, N.C.: IBM Publications,2007. Available online. URL: ftp://www.redbooks.ibm.com/redbooks/SG246366/zosbasics_textbook.pdf. AccessedAugust 14, 2007.“Mainframe Programming: Some Useful Resources for Practitionersof the Craft.” Available online. URL: http://www.oberoi-net.com/mainfrme.html. Accessed August 14, 2007.Prasad, N. S. IBM Mainframes: Architecture and Design. 2nd ed.New York: McGraw-Hill, 1994.Pugh, Emerson W., Lyle R. Johnson, and John H. Palmer. IBM’s 360and Early 370 Systems. Cambridge, Mass.: MIT Press, 1991.management information systemThe first large-scale use of computers in business in the late1950s and 1960s focused on fundamental data processing.Companies saw computers primarily as a way to automatesuch functions as payroll, inventory, orders, and accountspayable, hoping to keep up with the growing volume of datain the expanding economy while saving labor costs associatedwith manual methods. The separate data files and programsused for basic business functions were generally notwell integrated and could not be easily used to obtain crucialinformation about the performance of the business.By the 1970s, the growing capabilities of computersencouraged executives to look for ways that their informationsystems could be used to competitive advantage.Clearly, one possibility was that reporting and analysissoftware could be used to help them make faster and betterdecisions, such as about what products or markets toemphasize. To achieve this, however, the “data processingdepartment” had to be transformed into a “managementinformation system” (MIS) that could allow analysisof business operations at a variety of levels.The MIS PyramidIf one thinks of the information infrastructure of an enterpriseas being shaped like a pyramid, the bottom of thepyramid consists of the transactions themselves, whereproducts and services are delivered, and the supportingpoint of sale, inventory, and distribution systems that keeptrack of the flow of product.The next layer up begins the process of integration andoperational control. For example, previously separate salesand inventory system (perhaps updated through a dailybatch process) now become part of an integrated systemwhere a sale is immediately reflected in reduced inventory,and the inventory system is in turn interfaced with theorder system so more of a product is ordered when it goesout of stock.The activities involved in managing an enterprise’s informationinfrastructure can be drawn as a pyramid. The raw material oftransactions at the bottom are stored in databases. Moving up thepyramid, these data sources are integrated and refined to providebetter information about business operations as well as material foroperational analysis and strategic planning.The next layer can be called the operational analysislayer. Here such functions as sales, inventory, and orderingaren’t simply connected; they are part of the same systemof databases. This means that both simple and complexqueries and analysis can be run against a database containingevery type of transaction that the business engages in.In addition to routine reports such as sales by region orproduct line, market researchers or strategic planners canreceive the data they need to answer questions such as:• What products are staying on the shelf the longest?• What is the ratio between profitability and shelf spacefor particular items?• What is the relationship between price reductions,sales, and profits for a certain category of items?The goal of this layer is to help managers identify thevariables that affect the performance of their store or otherbusiness division and to determine how to optimize thatperformance (see also digital dashboard).The very top level can be called the strategic planninglayer. Here top-level executives are interested in the overalldirection of the business: determining which divisions of acompany should receive the greatest long-term investment,and which perhaps should be phased out. For example:• Which kind of sales are growing the fastest: in-store,mail-order catalog, or Internet on-line store?• How is our market share trending compared to variousclasses of competitors?

292 map information and navigation systems• How are sales trending with regard to various types(demographics) of customers?Software SupportThere are many considerations to choosing appropriatesoftware to support the users who are trying to answerquestions at the various levels of management. At minimum,to create a true management information system, theinformation from daily transactions must be made accessibleto a variety of query or analysis programs.In the past three decades many established businesseshave had to go through a painful process of converting avariety of separate databases and “legacy software” (oftenwritten in COBOL in the 1960s or 1970s) into a modernrelational database such as Oracle or Microsoft Access.Sometimes a company has decided that the cost of rewritingsoftware and converting data is simply too high, andinstead, opts for a patchwork of utility programs to convertdata from one program to another.The growth of networking in the 1980s and Web-basedintranets in the 1990s required that the old model of a large,centralized data repository accessed directly by only a fewusers be replaced by a less centralized model, sometimesgoing as far as using a distributed database system wheredata “objects” can reside throughout the network yet beaccessed quickly by any user (see database managementsystem). An alternative is the data repository that includesqueries and other tools (see data warehouse).Future of MISWith the prominence of the Internet and e-commerce today,MIS has had to cope with an even more complex and fastmovingworld. On the one hand, widespread e-commerceenables the capturing of more detailed data about transactionsand consumer behavior in general. New tools for analyzinglarge repositories of data (see data mining) make itpossible to continually derive new insights from the recentpast. It is thus clear that information is not just a tool butalso a corporate asset in itself. On the other hand, fiercecompetition and often shrinking profit margins in e-commercehave placed increasing pressure on MIS departmentsto find the greatest competitive advantage in the shortestpossible time.The importance of MIS has also been reflected in itsplace in the corporate hierarchy. The top-level executivepost of Chief Information Officer (CIO) has perhaps notyet achieved parity with the Chief Financial Officer (CFO),but healthy budgets for MIS even in constrained economictimes testify to its continuing importance.Further ReadingKroenke, David. Using MIS. Upper Saddle River, N.J.: PrenticeHall, 2005.Laudon, Kenneth C., and Jane P. Laudon. Management InformationSystems: Managing the Digital Firm. 10th ed. Upper SaddleRiver, N.J.: Prentice Hall, 2006.“MIS Resources.” Available online. URL: http://www3.uakron.edu/management/index.html. Accessed August 14, 2007.Turban, Efraim, et al. Information Technology for Management. 6thed. New York: Wiley, 2007map information and navigation systemsA variety of online services use the integration of mapsand databases to provide detailed information ranging fromweather forecasts to traffic conditions to local shopping andrestaurants. Increasingly, these services can be customizedto the user’s needs. Further, when combined with globalpositioning system (GPS) devices, the map display can befocused on the user’s current location, providing navigationand/or “points of interest” information. (For mappingsystems primarily designed for scientific or other analyticaluse, see geographical information systems.)MapquestMapQuest has its roots in the Cartographic Services Divisionof R. R. Donnelley, a leading maker of printed maps.The company first went online in 1996, was renamed Map-Quest in 1999, and was acquired by America Online (AOL)in 2000.The basic services offered by MapQuest are street mapsof a user-specified location, and driving routes betweenan origin and a destination. In recent years the servicehas been elaborated to allow users to customize routes, toobtain location-related “Yellow Pages” service from AOL,and to receive maps and driving directions on PDAs andmobile phones.Google Maps and Google EarthArriving on the Web in 2005 was Google Maps, a moresophisticated and versatile mapping service. There are fourtypes of map view: street map, actual satellite or aerial photo,street map overlaid on photo, and street-level photo views(in selected cities.) Besides specifying a particular locationfor the map, users can enter queries such as “pizza in Berkeley”to highlight locations where the pies are available.A related application is Google Earth, which was basedon a product acquired by Google in 2004. Google Earth isavailable for PCs running Windows, Mac OS, and Linux,and shows detailed imagery of most terrain at 15-metersresolution or smaller, with considerably more detailed imageryof some cities. Views have also been enhanced to providea better 3D visualization of features such as the GrandCanyon or Mount Everest, as well as a significant number ofmajor buildings. In 2007 Google added sky views as well assurface views of the Moon and Mars.Like other Google services, Google Maps and GoogleEarth offer extensive interfaces that can be used to linkmaps and imagery with data from other programs. Forexample, Wikipedia articles that include coordinate tagswill now be automatically linked to the correspondingcontent from Google Earth. (For more on the creation ofnew applications through combining existing services, seemashups.)Because mapping services (particularly Google) havefeatured relatively high-resolution aerial and even streetlevelphotographic views, some government agencies aroundthe world have complained that the service is providingtoo much detail of military or other sensitive installations.(This is also a potential terrorism concern.) Also, privacy

marketing of software 293advocates are concerned that actual images of identifiablepersons show up in the street-level imagery.Google has responded to security concerns by blurringthe imagery of some U.S. locations, presumably at governmentrequest. They have also argued that pictures of peoplewho are in public places months or years earlier are not areal privacy concern.Mobile Navigation SystemsMobile navigation systems can provide maps, driving directions,and sometimes additional information such as trafficconditions and advisories. The system can be either builtinto the dashboard (as with many higher-end vehicles) oravailable as a mounted unit such as those from Garmin,Tom Tom, and Magellan (see cars and computing).Mobile navigation systems link the user’s current location(obtained through the GPS system) to the unit’s storeddatabase of maps and other information, such as localpoints of interest. (Some units have backup dead-reckoningsystems based on the car’s motion, for use when GPSsignals are lost or distorted because of buildings or otherobstacles.)An alternative to in-car systems is the smartphone orPDA equipped with GPS and navigation software. Thesehave the advantage of also being useful for pedestrians orhikers.Users should look for navigation systems that have featuressuch as:• large, clear, readable display• overhead display and display from driver’s point ofview• uncluttered user interface to avoid distracting thedriver• voice announcements of driving directions and otherinformation• comprehensive maps and database including the abilityto load supplemental coverage for other areasAn important and sometimes overlooked issue withmobile navigation systems is the need to design the displayand user interface so as to minimize distraction. A combinationof large displays without unnecessary complexityand the use of spoken driving directions can help. A morecontroversial approach is to disable many functions of thesystem (such as entering new destinations) while the car isin motion.Further ReadingCar GPS (Navigation) Reviews. CNET. Available online. URL:http://reviews.cnet.com/4566-3430_7-0.html. Accessed September30, 2007.Crowder, David A. Google Earth for Dummies. Hoboken, N.J.:Wiley, 2007.Google Maps. Available online. URL: http://maps.google.com.Accessed September 29, 2007.Hofmann-Wellenhof, Bernhard, Klaus Legat, and Manfred Wieser.Navigation: Principles of Positioning and Guidance. New York:Springer, 2003.“Introduction to In-Car Navigation.” Crutchfield Advisor. Availableonline. URL: http://www.crutchfieldadvisor.com/ISEOrgbtcspd/learningcenter/car/navigation.html.Accessed September30, 2007.Mapquest. Available online. URL: http://www.mapquest.com/.Accessed September 29, 2007.Purvis, Michael, Jeffrey Sambells, and Cameron Turner. BeginningGoogle Maps Applications with PHP and Ajax: From Novice toProfessional. Berkeley, Calif.: APress, 2006.marketing of softwareThe way software has been produced and marketed haschanged considerably in the past five decades. In the nascentcomputer industry of the 1950s, commercial software wasdeveloped and marketed by the manufacturers of computersystems—firms such as Univac (later Sperry-Univac), Burroughs,and of course, IBM (see mainframe). However, aseparate (third-party) software industry emerged as earlyas 1955 with the founding of Computer Usage Corporation(CUC) by two former IBM employees. Nevertheless, the primarycompetition was between hardware manufacturers,with software seen as part of the overall package.By the early 1960s, larger software companies emergedsuch as Computer Science Corporation (CSC) and ElectronicData Systems (EDS), which became an empire underthe energetic, albeit often controversial leadership of H.Ross Perot, as well as the European giant SAP. These companiesspecialized in providing customized software solutionsfor users who could not meet their needs with thesoftware library offered by the maker of their computer system(see also business applications of computers).By the 1970s, however, vendor-supplied and contractedcustom software alternatives were being increasinglyaccompanied by “off the shelf” software packages. By 1976,100 software products from 64 software companies hadreached the $1 million mark in sales.The 1980s saw the emergence of a completely new sector:desktop computer (PC) users. Traditionally, softwarehad been marketed to programmers or managers, but nowindividual users or office managers could buy and installword processing programs, spreadsheets, database, andother programs. At the same time, a market for software foruse in the home and schools, particularly education, personalcreativity, and game programs required new methodsof marketing. For the first time ads for software began toappear on TV and in general-interest magazines.While large businesses still required custom-made software,most small to medium businesses looked for powerfuland integrated office software solutions (see applicationsuite, office automation, and Gates, William). By themid-1990s, Microsoft’s Office suite had dominated thismarket, although that dominance began to be threatened tosome extent by software written in Java or hosted on Linuxsystems (see also open source movement).The growth in the Internet (see e-commerce) has alsooffered new venues for the marketing and distributionof software. Sites such as ZDNet and CNet have to someextent displaced computer magazines as sources for productreviews. These sites also offer extensive libraries of “try

294 mashupsbefore you buy” software (see shareware), some of whichis trial versions of full-blown commercial products. Thelocal “mom and pop” PC software store has largely vanished,with software now marketed mainly by chain storessuch as Electronics Boutique or CompUSA, and increasingly,through Web-based stores, often established by thechains, as well as the giant on-line bookstore Amazon.com.Another trend impacting the traditional package modelof software delivery is the hosting and serving of applicationsonline (see application service provider) using asubscription model. Google has offered a free suite of officeand communications applications online, including componentsthat can be used off-line. This and other emergingofferings may portend further splitting of the softwaremarket into high-end or specialized applications on the onehand, and added-value or premium versions of free softwareon the other.Further ReadingCampbell-Kelly, Martin. From Airline Reservations to Sonic theHedgehog: A History of the Software Industry. Cambridge,Mass.: MIT Press, 2004.Computer History Museum. Software Industry SIG. “Preservingthe History of the Software Industry.” Available online. URL:http://www.softwarehistory.org/. Accessed August 14, 2007.Cusumano, Michael. The Business of Software: What Every Manager,Programmer, and Entrepreneur Must Know to Thrive andSurvive in Good Times and Bad. New York: Free Press, 2004.Hasted, Edward. Software that Sells: A Practical Guide to Developingand Marketing Your Software Project. Indianapolis: Wiley,2005.Plunkett, Jack W. Plunkett’s InfoTech Industry Almanac. Houston,Tex.: Plunkett Research, 2007.mashupsToday the creative world has blurred the boundaries thatonce separated works of art. Songs are sampled and remixedfrom earlier songs. Star Wars fans create new chapters inthe saga by remixing existing footage and adding their ownnew footage and effects. The fluidity and ease of manipulationof all digital data, regardless of its original source, hasmade it easier than ever before to reuse, repurpose, or reinventcontent. It is not surprising, then, that software itselfcan be mixed and matched to create new applications calledmashups.Mashups are new applications created by puttingtogether data or features from existing applications, such asmaps and databases. Many Web applications are designedto make their services available to other programs (see service-orientedarchitecture and Web 2.0). This can bedone at the programming level by providing an applicationprogramming interface (see api), or even through simplerfacilities that can be used easily by nonprogrammers.A number of major Web sites and applications provideresources for mashups, including Google (particularlyGoogle Maps), Amazon, eBay, Flickr, YouTube (image andvideo sharing), the “social bookmarking” site del.iciou.us,and many others. Some of these services (and third parties)have provided mashup editors to simplify the process ofcreating mashups.As a simple example, suppose one wants to create a mapdisplay showing rentals in San Francisco by neighborhood,color coded by rent range. Google Maps can generate mapsfor any area and plot points on them, given coordinates in astandard tag. Craigslist has rental ads including addresses.To create a mashup, a “screenscraper” can be used to extractaddresses and rents from the ads, and the colored pointscan then be plotted on a map of the city via Google.While the most common types of mashups are createdby and for ordinary users, mashup techniques can alsobe used in business applications. For example, data fromseveral sources (such as Web feeds [see rss]) or variousdatabases can be brought together and provided with aneasy-to-use interface (see digital dashboard).Mashups can also be considered to be an aspect of theemerging new information economy. Developers may befinding it in their interest to provide APIs and services suitablefor mashups because, in turn, the mashups increasethe use of the original program. By providing these services,developers are also contributing to a “digital commons”that benefits all.Further ReadingFeiler, Jesse. How to Do Everything with Web 2.0 Mashups.Emeryville, Calif.: McGraw Hill-Osborne, 2007.Google Mashup Editor. Available online. URL: http://code.google.com/gme/. Accessed October 1, 2007.“How to Create a Mashup.” Mashup Awards. Available online.URL: http://mashupawards.com/create/. Accessed October 1,2007.Lewis, Andre, et al. Beginning Google Maps Applications with Railsand Ajax: From Novice to Professional. Berkeley, Calif.: Apress,2007.Microsoft Popfly. Available online. URL: http://www.popfly.com/.Accessed October 1, 2007.QEDWiki (IBM). Available online. URL: http://services.alphaworks.ibm.com/qedwiki/.Accessed October 1, 2007.Yahoo! Pipes. Available online. URL: http://pipes.yahoo.com/pipes/. Accessed October 1, 2007.Yee, Raymond. Pro Web 2.0 Mashups: Remixing Data and Web Services.Berkeley, Calif.: Apress, 2008.mathematics of computingThe roots of modern computer science lie in an interest inrapid computation. Simple mechanical calculators (see calculator)may date back to ancient times; however, it is thework of mathematicians Blaise Pascal (1623–1662) and GottfriedLeibniz (1646–1716) that gave rise to the first practicalmechanical calculators. By the mid-19th century, CharlesBabbage (1791–1871) had conceptualized and designedmechanical computers that included the essential features(programs, processor, memory, input/output) of the moderndigital computer (see Babbage, Charles). His motivationwas the need for rapid, accurate calculation of statisticaltables made necessary by the manufacturing economy of theIndustrial Revolution. By the end of the century, the volumeof such data had increased to the point where mechanicalcalculators and tabulators (see Hollerith, Herman) hadbecome the only practical way to keep up.

mathematics software 295Mathematically, a computer can be seen as a way to rapidlyand automatically execute procedures that have beenproven to lead to reliable solutions to a problem (see algorithm).Once computers came on the scene, mathematicalprinciples for verifying or proving algorithms wouldacquire new practical importance.By the early 20th century, however, mathematicianswere beginning to examine the problem of determiningwhat propositions were provable, and in 1931 Kurt Godelpublished a proof that any mathematical system necessarilyallowed for the formation of propositions that could notbe proven using the axioms of that system. An analogousquestion was determining what problems were computable.Working independently, two researchers (see Church,Alonzo and Turing, Alan) formulated models that couldbe used to test for computability. Turing’s model, in particular,provided a theoretical construct (the Turing Machine)that could, using combinations of a few simple operations,calculate anything that was computable.By the 1940s, electromechanical (relays) or electronic(tube) switching elements made it possible to build practicalhigh-speed computers. Computer circuit designerscould draw upon the advances in symbolic logic in the 19thcentury (see Boolean operators). Boolean logic, with itstrue/false values, would prove ideal for operating computersconstructed from on/off switched elements.The mathematical tools of the previous 150 yearscould now be used to design systems that could not onlycalculate but also manipulate symbols and achieve resultsin higher mathematics (see the next entry, mathematicssoftware).Mathematics and Modern ComputersA variety of mathematical disciplines bear upon the designand use of modern computers. Simple or complex algebrausing variables in formulas is at the heart of many programsranging from financial software to flight simulators.Indeed, one of the most enduring scientific and engineeringlanguages takes its name from the process of translatingformulas into computer instructions (see fortran).Geometry, particularly the analytical geometry basedupon the coordinate system devised by Rene Descartes(1596–1650) is fundamental to computer graphics displays,where the screen is divided into X (vertical) and Y(horizontal) axes. Modern graphics systems have added 3Ddepiction and sophisticated algorithms to allow the rapiddisplay of complex objects. Beyond graphics, the Cartesianinsight that converted geometry into algebra makes avariety of geometrical problems accessible to computation,including the finding of optimum paths for circuit design.Design of computer and network architectures also involvesthe related field of topology. The fascinating field of fractalgeometry has found use in computer graphics and data storagetechniques (see fractals in computing).Aspects of number theory, often considered the mostabstract branch of mathematics, have found surprising relevancein computer applications. These include randomization(random number generation) and the factoring of largenumbers, which is crucial for cryptography.Mathematics also bears on computer networking withregard to communications theory (see bandwidth andShannon, Claude) and techniques for error correction.The Computer’s Contribution toMathematicsMathematics as a discipline is thus essential to its youngersibling, computer science. In turn, however, computer scienceand technology have enriched the pursuit of mathematicaltruth in surprising ways. As early as 1956, aprogram called Logic Theorist, written by Herbert Simon(1916–2001) and Allen Newell (1927–1992) demonstratedhow a program (that is, a collection of algorithms) couldprove mathematical propositions given axioms and rules.While these early programs worked on a somewhat hitor-missbasis, later theorem-solving programs producedsolutions different from the standard ones known to mathematicians,and sometimes more elegant. Thus the computer,which began as an aid to calculation, became an aidto symbol manipulation and to some extent an independentcreative source.Further Reading“Computers & Math News.” ScienceDaily. Available online.URL: http://www.sciencedaily.com/news/computers_math/.Accessed August 14, 2007.Henderson, Harry. Modern Mathematics: Powerful Patterns inNature and Society. New York: Chelsea House, 2007.Maxfield, Clive, and Alan Brown. The Definitive Guide to HowComputers Do Math. New York: Wiley-Interscience, 2005.McCullough, Robert. Mathematics for Computer Technology. 3rded. Engelwood, Colo.: Morton Publishing, 2006.Took, D. James, and Norma Henderson. Using Information Technologyin Mathematics Education. New York: Haworth Press,2001.Vince, John. Mathematics for Computer Graphics. 2nd ed. NewYork: Springer, 2005.mathematics softwareAs explained in the preceding article, computer sciencelooked to mathematics to create and verify its algorithms.In turn, computer software has greatly aided many levelsof mathematical work, ranging from simple calculations tomanipulation of symbols and abstract forms.At the simplest level, computers overlap the functionsof simple electronic calculators. Indeed, operating systemssuch as Microsoft Windows and UNIX systems includecalculator utilities that can be used to solve problemsrequiring a basic four function or more elaborate scientificcalculator.The true power of the computer became more evident toordinary users when spreadsheet software was introducedcommercially in 1979 with VisiCalc (see spreadsheet).Spreadsheets make it easy to maintain and update summariesand other reports generated by formulas. Later versionsof spreadsheet programs such as Lotus 1-2-3 and MicrosoftExcel have the ability to create a wide variety of plots andcharts to show relationships between variables in visualterms.

296 Mauchly, John WilliamMoving from simple formulas to the manipulation of symbolicquantities (as in algebra), the Association for ComputingMachinery (ACM) classification system describes severalbroad areas of computer-aided mathematics. These includenumerical analysis (techniques for solving, linear, non-linear,and differential equations), discrete mathematics (combinatorialand graph theory), and probability and statistics.There are two general approaches to mathematicalsoftware. One is the creation of libraries of routines orprocedures that address particular kinds of problems. Aprogrammer who is creating software that must deal withparticular mathematical problems can link these routinesto the program, call the procedures with appropriate variablesor data, and return the results to the main programfor further processing (see procedures and functions).The language FORTRAN is still widely used for developingmathematics libraries, and there is a legacy of tens of thousandsof routines available. Modern systems have the abilityto link these procedures to programs written in more recentlanguages such as C.The advantage of using program libraries is that theydon’t require learning new programming techniques. Eachroutine can be treated as a “black box.” However, it is oftendesirable to work with traditional mathematical notation(what one might see on a blackboard in a calculus class,rather than typed into computer code). A stand-alone softwarepackage such as Mathcad, Matlab, or Mathematicacan automatically simplify or solve algebraic expressions orperform hundreds of traditional mathematical procedures.For statistical analysis, programs such as SPSS can apply allof the standard statistical tests to data and provide a largevariety of graphics.Further ReadingField, Andy. Discovering Statistics Using SPSS. 2nd ed. ThousandOaks, Calif.: SAGE Publications, 2005.Griffith, Arthur. SPSS for Dummies. Hoboken, N.J.: Wiley, 2007.Netlib Repository of Mathematical Software, Papers, and Databases.Available online. URL: http://www.netlib.org/. AccessedAugust 14, 2007.Press, William H., et al. Numerical Recipes. 3rd ed. New York:Cambridge University Press, 2007.Ruskeepaa, Heikki. Mathematica Navigator: Mathematics, Statistics,and Graphics. Burlington, Mass.: Elsevier AcademicPress, 2004.Wellin, Paul, Richard Gaylord, and Samuel Kamin. An Introductionto Programming with Mathematica. New York: CambridgeUniversity Press, 2005.Wolfram, Stephen. The Mathematica Book. 5th ed. Champaign, Ill.:Wolfram Media, 2003.Wolfram Mathematica Home Page. Available online. URL: http://www.wolfram.com/. Accessed August 14, 2007.Mauchly, John William(1907–1980)AmericanInventor, Computer ScientistJohn Mauchly was codesigner of the earliest full-scale digitalcomputer, ENIAC, and its first commercial successor,Univac (see also Eckert, J. Presper). His and Eckert’s workwent a long way toward establishing the viability of thecomputer industry in the early 1950s.Mauchly was born on August 30, 1907, in Cincinnati,Ohio. He attended the McKinley Technical High School inWashington, D.C., and then began his college studies atJohns Hopkins University, eventually changing his majorfrom engineering to physics. The spectral analysis problemshe tackled for his Ph.D. (awarded in 1932) and inpostgraduate work required a large amount of painstakingcalculation. So, too, did his later interest in weather prediction,which led him to design a mechanical computerfor harmonic analysis of weather data (see analog computer).He also learned about binary switching circuits(“flip-flops”) and experimented with building electroniccounters, which used vacuum tubes and were much fasterthan counters using electromagnetic relays.Mauchly taught physics at Ursinus College in Philadelphiafrom 1933 to 1941. On the eve of World War II, however,he went to the University of Pennsylvania’s MooreSchool of Engineering and took a course in military applicationsof electronics. He then joined the staff and beganworking on contracts to prepare artillery firing tables forthe military. Realizing how intensive the calculationswould be, in 1942 he wrote a memo proposing that anelectronic calculator be built to tackle the problem. Theproposal was rejected at first, but by 1943 table calculationby mechanical methods was falling even further behind.Herman Goldstine, who had been assigned by the AberdeenProving Ground to break the bottleneck, approved the calculatorproject.With Mauchly providing theoretical design work andJ. Presper Eckert heading the engineering effort, the ElectronicNumerical Integrator and Computer, better known asENIAC, was completed too late to influence the outcome ofthe war. However, when the machine was demonstrated inFebruary, 1946, it showed that a programmable electroniccomputer was not only about a thousand times faster thanan electromechanical calculator, it could be used as a general-purposeproblem-solver that could do much more thanexisting calculators.Mauchly and Eckert left the Moore School after a disputeabout who owned the patent for the computer work.They jointly founded what became known as the Eckert-Mauchly Computer Corporation, betting on Mauchly’s confidencethat there was sufficient demand for computers notonly for scientific or military use, but for business applicationsas well. By 1950, however, they were struggling to selland build their improved computer, Univac, while fulfillingexisting government contracts for a scaled-down versioncalled BINAC. In 1950, they sold their company to RemingtonRand, while continuing to work on Univac. In 1952,Univac stunned the world by correctly predicting the presidentialelection results on election night long before most ofthe votes had come in.Early on, Mauchly saw the need for a better way to writecomputer programs. Univac and other early computers hadbeen programmed through a mixture of rewiring, setting ofswitches, and entering numbers into registers. This made

McCarthy, John 297programming difficult, tedious, and error-prone. Mauchlywanted a way that variables could be represented symbolically:for example, Total rather than a register number suchas 101. Under Mauchly’s supervision William Schmitt wrotewhat became known as Brief Code. It allowed two-lettercombinations to stand for both variables and operationssuch as multiplication or exponentiation. A special programread these instructions and converted them to thenecessary register and machine operation commands (seeinterpreter). While primitive compared to later languages(see assembler and programming languages), Brief Coderepresented an important leap forward in making computersmore usable.Mauchly stayed with Remington Rand and its successorSperry Rand until 1959, but then left over a dispute aboutthe marketing of the Univac. He continued his career as aconsultant and lecturer. Mauchly and Eckert also becameembroiled in a patent dispute arising from their originalwork with ENIAC. Accused of infringing Sperry Rand’sENIAC patents, Honeywell claimed that the ENIAC patentwas invalid, with another computer pioneer, John Atanasoff,claiming that Mauchly and Eckert had obtained crucialideas after visiting his laboratory in 1940 (see Atanasoff,John Vincent).In 1973, Judge Earl Richard Larson ruled in favor ofAtanasoff and Honeywell. However, many historians ofthe field give Mauchly and Eckert the lion’s share of thecredit because it was they who had built full-scale, practicalmachines.Mauchly played a key role in founding the Associationfor Computing Machinery (ACM), one of the field’s premierprofessional organizations. He served as its first vice presidentand second president. He received many tokens of recognitionfrom his peers, including the Howard Potts Medalof the Franklin Institute. In turn, the ACM established anEckert-Mauchly award for excellence in computer design.John Mauchly died on January 8, 1980.Further Reading“John W. Mauchly and the Development of the ENIAC Computer:An Exhibition in the Department of Special Collections, VanPelt Library, University of Pennsylvania.” Available online.URL: http://www.library.upenn.edu/exhibits/rbm/mauchly/jwmintro.html. Accessed August 14, 2007.McCartney, Scott. ENIAC: The Triumphs and Tragedies of the World’sFirst Computer. New York: Berkeley Books, 1999.Stern, N. “John William Mauchly: 1907–1980,” Annals of the Historyof Computing (April 1980): 100–103.McCarthy, John(1927– )AmericanComputer Scientist, AI PioneerStarting in the 1950s, John McCarthy played a key role inthe development of artificial intelligence as a discipline, aswell as developing LISP, the most popular language in AIresearch.John McCarthy was born on September 4, 1927, in Boston,Massachusetts. He completed his B.S. in mathematicsat the California Institute of Technology, then earned hisPh.D. at Princeton University in 1951. During the 1950s, heheld teaching posts at Stanford University, Dartmouth College,and the Massachusetts Institute of Technology.Although he seemed destined for a prominent careerin pure mathematics, he encountered computers whileworking during the summer of 1955 at an IBM laboratory.He was intrigued with the potential of the machines forhigher-level reasoning and intelligent behavior (see artificialintelligence). The following year he put togethera conference that brought together people who wouldbecome key AI researchers, including Marvin Minsky (seeMinsky, Marvin). He proposed that “the study is to proceedon the basis of the conjecture that every aspect oflearning or any other feature of intelligence can in principlebe so precisely described that a machine can be madeto simulate it. An attempt will be made to find how tomake machines use language, form abstractions and concepts,solve kinds of problems now reserved for humans,and improve themselves.”Mathematics had well-developed symbolic systemsfor expressing its ideas. McCarthy decided that ifAI researchers were to meet their ambitious goals, theywould need a programming language that was equallycapable of expressing and manipulating symbols. Startingin 1958, he developed LISP, a language based on liststhat could flexibly represent data of many kinds and evenallowed programs to be fed as data to other programs(see lisp). LISP would be used in the coming decades tocode most AI research projects, and McCarthy continuedto play an important role in refining the language, whilemoving to Stanford in 1962, where he would spend therest of his career.McCarthy also contributed to the development ofAlgol, a language that would in turn greatly influencemodern procedural languages such as C. He also helpeddevelop new ways for people to use computers. Consultingwith Bolt, Beranek and Newman (the companythat would later build the beginnings of the Internet),he helped design time-sharing, a system that allowedmany users to share the same computer, bringing downthe cost of computing and making it accessible to morepeople. He also sought to make computers more interactive,designing a system called THOR, which used videodisplay terminals. Indeed, he pointed the way to the personalcomputer in a 1972 paper on “The Home InformationTerminal.”In 1971, McCarthy received the prestigious A. M. Turingaward from the Association for Computing Machinery. Inthe 1970s and 1980s, he taught at Stanford and remained aprominent spokesperson for AI, arguing against critics suchas philosopher Hubert Dreyfus (see Dreyfus, Hubert),who claimed that machines could never achieve true intelligence.In 2000 McCarthy retired from Stanford, where heremains a Professor Emeritus. In 2003 McCarthy receivedthe Benjamin Franklin Medal in Computer and CognitiveScience.

298 measurement units used in computingFurther Reading“John McCarthy’s Home Page.” Available online. URL: http://wwwformal.stanford.edu/jmc/.Accessed August 14, 2007.McCarthy, John. “The Home Information Terminal.” Man andComputer: Proceedings of the International Conference, Bordeaux,France, 1970. Basel: S. Karger, 1972, 48–57.———. “Philosophical and Scientific Presuppositions of LogicalAI,” in McCarthy, H. J. and Vladimir Lifschitz, eds., FormalizingCommon Sense: Papers by John McCarthy. Norwood, N.J.:Ablex, 1990.McCorduck, Pamela. Machines Who Think. 2nd ed. Natick, Mass.:A. K. Peters, 2004.measurement units used in computingNewcomers to the computing world often have difficultymastering the variety of ways in which computer capacityand performance are measured. A good first step is to lookat the most common metric prefixes that indicate the magnitudeof various units (see table).Common Metric Prefixes Used inComputingPrefixkilomegagigateramillimicronanopicoMagnitude10 3 (1 thousand)10 6 (1 million)10 9 (1 billion)10 12 (1 trillion)10 -3 (1 thousandth)10 -6 (1 millionth)10 -9 (1 billionth)10 -12 (1 trillionth)Strictly speaking, most computer measurements are basedon the binary system, using powers of two. Thus kiloactually means 2 10 , which is actually 1,024, and mega isactually 2 20 , or 1,048,576. However, this distinction isgenerally not important for gaining a sense of the magnitudesinvolved. In 1998, the International ElectrotechnicalCommission promulgated a new set of prefixes forthese base two computer-related magnitudes, such thatfor example, mebi- is supposed to be used instead ofmega-. There is little evidence thus far that this scheme isbeing widely adopted.We will now consider some of the main areas in whichcomputer capacity or performance is measured.Storage CapacityThe smallest unit of information, and thus of data storage,is a bit (binary digit). A bit can be either 1 or 0 and isphysically represented in different ways according to thememory or storage device being used. On most computersthe most-used storage unit is the byte, which contains eightbits. Since this represents eight binary digits, or 2 8 , a bytecan hold values from 0 to 255 (decimal). The following tablegives some typical units of storage.Unitbitbyte (8 bits)kilobytemegabytegigabyteterabyteData Storage UnitsTypical UseProcessor data handling capacity. Mostprocessors today can handle 32 or 64 bits ata time.Holds an ASCII character value or a smallnumber, 0–255.Used to measure RAM (random accessmemory) and floppy disk capacity forearly PCs.RAM capacity in older PCs; hard drivecapacity in older PCs.Memory and drive capacity in modern PCs.Large modern hard drives; drive arrays (seeraid).GraphicsPrinted output is generally measured in dots per inch (dpi).Screen images and images used in digital photography aremeasured in pixels or megapixels. However, the amount ofdata needed to specify (and thus store) a pixel in an imagedepends on the number of colors and other information tobe stored. (See graphics formats.)Processor SpeedProcessor speed is measured in millions of cycles per second(megahertz or MHz). The earliest microprocessors hadspeeds measured in 1–2 MHz or so. PCs of the 1980s rangedfrom about 8 to 50 MHz. In the 1990s, speeds ramped up tothe hundreds of MHz, and in today’s systems PC speeds areoften measured in gigahertz (GHz).Calculation SpeedThe speed at which a computer can perform calculationsdepends on more than raw processor speed. For example,a processor that can store or fetch 32-bit numbers can performmany calculations faster than one with only a 16-bitcapacity even if the two processors have the same clockspeed in cycles per second.Calculation speed is often measured in “flops” or floating-pointoperations per second (see numeric data), or formodern processors, megaflops. While this measurement isoften touted in product literature, savvy users look to morereliable benchmarks that re-create actual conditions of use,including calculation-intensive, data transfer intensive, orgraphics-intensive operations.Data Communications and NetworkingThe speed at which data can be transferred over a modemor network connection is measured in bits per second(BPS). A related term, baud, was used (somewhat inaccurately)with the earlier modems (see bandwidth andmodem).

medical applications of computers 299DeviceTypical Data Transfer Speeds inBits Per Second (BPS)approximate SpeedEthernet(10 base) 10 MbpsFast Ethernet100 MbpsGigabit Ethernet1 GbpsV.90 dial-up modem 56 KbpsISDN phone line64 KbpsDSL (ADSL)1–24 MbpsCable modem (DOCSIS)10–160 MbpsBluetooth 2.0 (see bluetooth) 3 Mbps802.11b wireless (see wireless 11 Mbpscomputing)802.11g wireless (see wireless 54 Mbpscomputing)802.11n wireless 540 MbpsFurther ReadingHow Many? A Dictionary of Units of Measurement. Available online.URL: http://www.unc.edu/~rowlett/units/. Accessed August 14,2007.Online [unit] Conversion. Available online. URL: http://www.onlineconversion.com/. Accessed August 14, 2007.SG Bits/Bytes Conversion Calculator. Available online. URL:http://www.speedguide.net/conversion.php. Accessed August14, 2007.media center, homeIn recent years many families have acquired a plethora ofmedia and devices to play it—CD and DVD players, radios,and of course TVs. Meanwhile, the family has likely alsoacquired one or more PCs, which are also capable of playingdigital audio and video from various sources. The mediacenter is a way of integrating all of these media into onecentrally located device, the PC, and ideally being able toserve it on demand anywhere in the home.Modern PCs already have optical drives (see cd-romand dvd-rom). TV signals can be received using a TV tunercard or, for digital cable signals, a “cable card.” (High-definitionTV or HDTV is becoming increasingly popular.)There are also tuners for AM/FM radio. Of course audioand video files can also be received directly over the Internet(see Internet radio; music and video distribution,online; and streaming).Media Storage and DistributionOnce media is received, it can be stored on one or more harddrives (see also DVR). The media can also be distributed toremote speaker units via the wired (or more often wireless)network. Remote controls are usually provided to allow thesystem to be controlled from anywhere in the building.Of course software is needed to integrate these devicesand functions. Microsoft provides the Windows Media Centerfor Vista and the Windows XP Media Center Edition.(There is also third-party software for Windows.) Linuxsystems can run programs such as MythTV (free) or thecommercial SageTV. For the Macintosh, a project calledCenterStage was under development as of 2008.Prebuilt media centers with the PC and all the necessaryinputs and outputs are also available. They are often sold aspart of home theater systems.Further ReadingBallew, Joli. How to Do Everything with Windows Vista Media Center.Emeryville, Calif.: McGraw-Hill/Osborne, 2007.Knoppmyth (Knoppix and MythTV Linux media center). Availableonline. URL: http://www.knoppmythwiki.org/?id=KnoppmythWiki. Accessed October 1, 2007.Layton, Julia. “How Media-Center PCs Work.” Available online.URL: http://computer.howstuffworks.com/media-center-pc.htm. Accessed October 1, 2007.Smith, Stewart, and Michael Still. Practical MythTV: Building a PVRand Media Center PC. Berkeley, Calif.: Apress, 2007.Windows Media Center (Vista). Available online. URL: http://www.microsoft.com/windows/products/windowsvista/features/details/mediacenter.mspx. Accessed October 1, 2007.medical applications of computersSince health care delivery is a business (indeed, one of thelargest sectors of the economy), any hospital, health plan, orindependent medical practice involves much the same softwareas any other large business. This includes accountsreceivable and payable, payroll, and supplies inventory.Both general and customized industry software can be usedfor these functions; however, this article focuses on applicationsspecific to medicine.Medical Information SystemsThe management of information specifically related to medicalcare is sometimes called medical informatics. The typeof information gathered depends on many factors includingthe type of institution, ranging from a small doctor’s officeto a large clinic to a full hospital and the nature and scopeof the treatment provided. However, one can make somegeneralizations.For outpatients, the required information includesan extensive medical record for each patient, includingrecords of medical tests and their results, prescriptions andtheir status, and so on. For hospital patients, there are alsoadmissions records, an extensive list of itemized charges,and records that must be maintained for public health orother governmental purposes. Hospitals increasingly usecustomized, integrated hospital information systems (HIS)that integrate billing, medical records, and pharmacy.Additional record keeping needs arise from the mechanismsused to pay for health care. Each health paymentsystem, whether government-run (such as Medicare or theVeterans’ Administration) or a private health maintenanceorganization (HMO), has extensive rules and proceduresabout how each surgery, treatment, test, or medication canbe submitted for payment. The software must be able touse recognized classifications systems such as the DSM-IV(Diagnostic and Statistical Manual of Mental Disorders).

300 medical applications of computersClinical Information ManagementThe modern hospital generates extensive real-time dataabout the condition of patients, particularly those in criticalor intensive care or undergoing surgery. Many hospitalshave bedside or operating room terminals where physiciansor nurses can review summaries of data such as vital statistics(blood pressure, heart function, and so on). Data canalso be entered or reviewed using handheld computers (seeportable computers). The ultimate goal of such systemsis to provide as much useful information as possible withoutoverwhelming medical personnel with data entry andrelated tasks that might detract from patient care.In 2001, a new group, the Patient Safety Institute, wasformed in an attempt to create a nationwide standardizedformat for electronic patient records. This would make itpossible for emergency personnel to download a patient’srecord into a handheld computer and access potentially lifesavinginformation such as medications and allergies.There has also been some progress in medical decisionsupport systems. Going beyond data summarization, suchsystems can analyze changes or trends in medical dataand highlight those of clinical significance. Such systemscan also aid in the compilation of medical charts or possiblycompile portions of the chart automatically for laterreview.Diagnostic and Treatment SystemsThe diagnosis and treatment of many conditions has beenprofoundly enhanced by the use of computer-assisted medicalinstruments. At the beginning of the last century theuse of X-rays revolutionized the imaging of the anatomyof living things. X-rays, however, were limited in detailand depth of imaging. Techniques of tomography, involvingsynchronized movement of the X-ray tube and film, werethen developed to create a sharp focus deeper within thetarget structure. The development of computerized tomography(CT or CAT) scanning in the 1970s used a differentand more effective approach: A beam of X rays is sweptthrough the target area while computerized radiation detectorsprecisely calculate the absorption of radiation, and thusthe density of the tissue or other structure at each point.This results in a highly detailed image that can be viewedas a series of layers or combined into a three-dimensionalholographic display.Another widely used imaging technique is positronemission tomography (PET) scanning, which tracks theradiation emission from a short-lived radioisotope injectedinto the patient. It is particularly helpful for studying theflow of blood or gas and other physiological or metabolicchanges. Magnetic resonance imaging (MRI) uses theabsorption and re-emission of radio waves in a strong magneticfield to identify the characteristic signature of thehydrogen nucleus (i.e. a proton) in water within the body,and thus delineate the surrounding structures.Besides controlling the scanning process (especially inCAT scanning), the computer is essential for the creationand manipulation of the resulting images. A typical imageprocessing (IP) system is actually an array of many individualprocessors that perform calculations and comparisonson parts of the image to enhance contrast and extract informationthat can lead to a more precise depiction of the areaof interest. The resulting images (consisting of an array ofpixels and associated information) can be further enhancedin a variety of ways using video processing software. Othersoftware using pattern recognition techniques can be programmedto look for tumors or other anomalous structures(see image processing).TrendsMedical informatics is likely to be a strong growth areain coming decades. As the population ages, demand formedical care will increase. At the same time, there will begrowing pressure to control costs. Although technology isexpensive, there is a general belief that information canbe leveraged to provide more cost-effective treatment andmanagement of health care delivery.Medical systems are likely to become more integrated.There have been proposals to create permanent, extensiveelectronic medical records that patients might even “wear” inthe form of a small implanted chip. However, concern aboutthe consequences of violation of privacy and misuse of medicalinformation (such as by employers or insurers) raises significantchallenges (see also privacy in the digital age).There are many exciting possibilities for computerassistedmedical treatment. It may eventually be possible toprovide all the detail of a CAT scan or MRI while a medicalprocedure is being performed. At any rate, surgeons willbe able to see ever more clearly what they are doing, androbot-controlled surgical instruments (such as lasers) arealready operating with a precision that cannot be matchedby human hands. Such instrumentation also allows for thepossibility that skilled surgeons might be able to operatethrough telepresence, bringing lifesaving surgery to remoteareas (see telepresence).Information technology (and the World Wide Web inparticular) is also giving patients more data and choicesThis NASA project is developing a “smart” probe that could provideinstant analysis of breast tumors to guide surgeons in their work.Such instruments could make surgery more accurate and effective,as well as reducing unnecessary operations. (NASA photo)

memory 301about prospective drugs and treatments. (See personalhealth information management.)Further ReadingChen, Hsinchun, et al., eds. Medical Informatics: Knowledge Managementand Data Mining in Biomedicine. New York: Springer,2005.LinuxMedNews [open-source medical software]. Available online.URL: http://www.linuxmednews.com/. Accessed August 14,2007.Medical Software (Yahoo! Directory). Available online. URL:http://dir.yahoo.com/Business_and_Economy/Business_to_Business/Health_Care/Software/Me dical/. Accessed August14, 2007.Shortliffe, Edward H., and James J. Cimino, eds. Biomedical Informatics:Computer Applications in Health Care and Biomedicine.New York: Springer, 2006.Sullivan, Frank, and Jeremy Wyatt. ABC of Health Informatics. Malden,Mass.: Blackwell, 2006.Wooton, Richard. Introduction to Telemedicine. 2nd ed. London:Royal Society of Medicine Press, 2006.memoryGenerally speaking, memory is a facility for temporarilystoring program instructions or data during the courseof processing. In modern computers the main memory israndom access memory (RAM) consisting of silicon chips.Today’s personal computers typically have from between64MB (megabytes) and 512MB of main memory.Development of the TechnologyIn early calculators “memory” was stored as the positionsof various dials. Charles Babbage conceived of a “store” ofsuch dials that could hold constants or other values neededduring processing by his Analytical Engine (see Babbage,Charles).A number of forms of memory were used in early electronicdigital computers. For example, a circuit with aninherent delay could be used to store a series of pulses thatcould be “refreshed” every fraction of a second to maintainthe data values. The Univac I, for example, used a mercurydelay line memory. Researchers also experimented withcathode ray tubes (CRTs) to store data patterns.The most practical early form of memory was the ferritecore, which consisted of an array of tiny donut-shaped magnets,crisscrossed by electrical lines so that any elementcan be addressed by row and column number. By convertingdata into appropriate voltage levels, the magnetic stateof the individual elements can be switched on and off torepresent 1 or 0. In turn, a current can be passed throughany element to read its current state—although the elementmust then be remagnetized. Ferrite cores were relativelyfast but expensive, and “core” became programmers’ shorthandfor the amount of precious memory available.By the 1960s, the use of transistors and integrated circuitsmade electronic solid-state memory systems possible. Sincethen, the MOSFET (Metal Oxide Semiconductor Field EffectTransistor) using CMOS (Complementary Metal Oxide) fabricationhas been the dominant way to implement DRAM(dynamic random access memory). Here “dynamic” meansthat the memory must be “refreshed” by applying currentafter data is read in each cycle, and “random access” meansthat any desired memory location can be accessed directlyrather than requiring locations to be read sequentially.Static RAM is used in some computer components wheremaximum memory speed is desirable. Static memory is fasterbecause it does not need to be refreshed after each readingcycle. However, it is also considerably more expensive.Memory performance is also dependent on how quicklylocations in the memory can be addressed. The earliestforms of DRAM required that the row and column of thedesired memory location be sent in separate cycles. EDO(Extended Data Out) and more recent technologies allowthe row to be requested one time, and then just the columngiven for adjacent or nearby locations. Timing and pipeliningtechniques can also be used to start a new request whilethe previous one is still being processed.For SDRAM (synchronous DRAM), memory speed islimited by the inherent response time of the memory chip,but also by the number of clock cycles per second initiatedby the data bus (see bus). Double data rate (DDR) SDRAMis able to use both the “rising” and “falling” part of theclock cycle to transfer data, doubling throughput. It is beingsuperseded by DDR2, which achieves another doublingbecause it can run the data-transfer bus at twice the systemclock speed. However, this does increase latency (the timeneeded to begin an access). On the horizon is DDR3, whichcan run the bus at four times clock speed—yet anotherdoubling. Possible future memory technologies include“spintronics,” or the use of the quantum state or “spin” ofelectrons to hold data. The speed, compactness, and reliabilityof this technology could exceed current devices by afactor of hundreds to thousands.As memory gets faster, it continues to get cheaper (atleast for all but the latest technology). At the same time,memory demands continue to increase. Today’s PCs generallycome with 1 GB (billion bytes) of RAM, and 2 GB ormore is often recommended, particularly for memory-hungryoperating systems such as Microsoft Windows Vista andapplications such as Adobe PhotoShop and video editing.Another popular kind of memory is “flash” (nonvolatile)memory that does not require power to maintain itscontents. This kind of memory is used in a wide variety ofdevices, including digital cameras, PDAs, and media players(see also flash drive).In actual systems, a small amount of faster memory (seecache) is used to hold the data that is most likely to beimmediately needed. A proper balance between primaryand secondary cache and main memory in the system chipsetmakes it less necessary to use the fastest, most expensiveform of main memory.Many computers also have ROM (Read-Only Memory) orPROM (Programmable Read-Only Memory). This memoryholds permanent system settings and data (see bios) that areneeded during the startup process (see boot sequence).Further ReadingJacob, Bruce, Spencer Ng, and David Wang. Memory Systems:Cache, DRAM, Disk. San Francisco: Morgan Kaufmann, 2007.

302 memory managementTom’s Hardware: Motherboards and RAM. Available online. URL:http://www.tomshardware.com/motherboard/index.html.Accessed August 15, 2007.“Ultimate Memory Guide.” Available online. URL: http://www.kingston.com/tools/umg/default.asp. Accessed August 15,2007.memory managementWhatever memory chips or other devices are installed in acomputer, the operating system and application programsmust have a way to allocate, use, and eventually releaseportions of memory. The goal of memory management is touse available memory most efficiently. This can be difficultin modern operating environments where dozens of programsmay be competing for memory resources.Early computers were generally able to run only oneprogram at a time. These machines didn’t have a true operatingsystem, just a small loader program that loaded theapplication program, which essentially took over controlof the machine and accessed and manipulated the memory.Later systems offered the ability to break main memory intoseveral fixed partitions. While this allowed more than oneprogram to run at the same time, it wasn’t very flexible.Virtual MemoryFrom the very start, computer designers knew that mainmemory (RAM) is fast but relatively expensive, while secondaryforms of storage (such as hard disks) are slowerbut relatively cheap. Virtual memory is a way to treat suchauxiliary devices (usually hard drives) as though theywere part of main memory. The operating system allocatessome storage space (often called a swapfile) on the disk.When programs allocate more memory than is availablein RAM, some of the space on the disk is used instead.Because RAM and disk are treated as part of the sameaddress space (see addressing), the application requestingmemory doesn’t “know” that it is not getting “real”memory. Accessing the disk is much slower than accessingmain memory, so programs using this secondary memorywill run more slowly.Virtual memory has been a practical solution since the1960s, and it has been used extensively on PCs runningoperating systems such as Microsoft Windows. However,with prices of RAM falling drastically in the new century,there is likely to be enough main memory on the latest systemsavailable to run most popular applications.Memory AllocationMost programs request memory as needed rather than afixed amount being allocated as part of program compilation.(After all, it would be inefficient for a program to tryto guess how much memory it would need, and possiblytie up memory that could be used more efficiently by otherprograms.) The operating system is therefore faced with thetask of matching the available memory with the amountsbeing requested as programs run.One simple algorithm for memory allocation is calledfirst fit. When a program requests memory, the operatingsystem looks down its list of available memory blocks andallocates memory from the first one that’s large enough tofulfill the request. (If there is memory left over in the blockafter allocation, it becomes a new block that is added to thelist of free memory blocks.)As a result of repeated allocations using this method, thememory space tends to become fragmented into many leftoversmall blocks of memory. As with fragmentation of fileson a disk, memory fragmentation slows down access, sincethe hardware (see memory) must issue repeated instructionsto “jump” to different parts of the memory space.Using alternative memory allocation algorithms canreduce fragmentation. For example, the operating systemcan look through the entire list (see heap) and find thesmallest block that is still large enough to fulfill the allocationrequest. This best fit algorithm can be efficient. Whileit still creates fragments from the small leftover pieces, thefragments usually don’t amount to a significant portion ofthe overall memory.The operating system can also enforce standard blocksizes, keeping a “stockpile” of free blocks of each permittedsize. When a request comes in, it is rounded to the nearestamount that can be made from a combination of thestandard sizes (much like making change). This approach,sometimes called the buddy system, means that programsmay receive somewhat more or less memory than they want,but this is usually not a problem.Recycling MemoryIn a multitasking operating system, programs should releasememory when it is no longer needed. In some programmingenvironments memory is released automatically when adata object is no longer valid (see variable), while in othercases memory may need to be explicitly freed by calling theappropriate function.Recycling is the process of recovering these freed-upmemory blocks so they are available for reallocation. Toreduce fragmentation, some operating systems analyze thefree memory list and combine adjacent blocks into a single,larger block (this is called coalescence). Operating systemsthat use fixed memory block sizes can do this more quicklybecause they can use constants to calculate where blocksbegin and end.Many more sophisticated algorithms can be used toimprove the speed or efficiency of memory management. Forexample, the operating system may be able to receive information(explicit or implicit) that helps it determine whetherthe requested memory needs to be accessed extremelyquickly. In turn, the memory management system may bedesigned to take advantage of particular processor architecture.Combining these sources of knowledge, the memorymanager might decide that a particular requested memoryblock be allocated from special high speed memory (seecache).While RAM is now cheap and available in relativelylarge quantities even on desktop PCs, the never-endingrace between hardware resources and the demands of everlarger database and other applications guarantees thatmemory management will remain a concern of operat-

microprocessor 303ing system designers. In particular, distributed databasesystems where data objects can reside on many differentmachines in the network require sophisticated algorithmsthat take not only memory speed but also network loadand speed into consideration.Further ReadingBlunden, Bill. Memory Management: Algorithms and Implementationsin C/C++. Plano, Tex.: Wordware Publishing, 2002.Jones, Richard, and Rafael D. Lins. Garbage Collection: Algorithmsfor Automatic Dynamic Memory Management. New York:Wiley, 1996.“The Memory Management Reference Beginner’s Guide: Overview.”Available online. URL: http://www.memorymanagement.org/articles/begin.html. Accessed August 15, 2007.message passingIn the early days of computing, a single program usuallyexecuted sequentially, with interruptions for calls to variousprocedures or functions that would perform data processingtasks and then return control to the main program(see procedures and functions). However, by the 1970sUNIX and other operating systems had introduced thecapability of running several programs at the same time(see multitasking). Additionally, it became common tocreate a large program that would manage data and smallerprograms that could link users to that service (see clientservercomputing). Further, programs themselves beganto be organized in a new way (see object-oriented programming).A program now consisted of a number of entities(objects) representing data and methods (things thatcan be done with the data).Thus, both at the operating system and application levelit became necessary to have various objects communicatewith one another. For example, a client program requestsa service from the server. The server performs the requiredservice and reports its completion. The mechanism bywhich information can be sent from one program to another(or between objects in a program) is called message passing.In one message-passing scheme, two objects (such as clientand server) agree on a standard memory location calleda port. Each program checks the port regularly to see if amessage (containing instructions, data, or an address wheredata can be found) is pending. In turn, outgoing messagescan be left at the port.The client-server idea can be found within operatingsystems as well. For example, there can be a componentdevoted to providing file-related services, such as openingor reading a file (see file). An application that wants toopen a file leaves an appropriate message to the operatingsystem. The operating system has a message dispatcher thatexamines incoming messages and routes them to the correctcomponent (the file system manager in this case).Within an object-oriented program, an object is sent amessage by invoking one of its methods (Smalltalk and otherlanguages) or member functions (C++ or Java). For example,suppose there’s an object call Speaker that represents thesystem’s internal speaker. As part of a user alert procedure,there might be a call toSpeaker.Beep (500)which might be defined to mean “sound a beep for 500 milliseconds.”There are a number of issues involved in setting upmessage-passing systems. For example, it is convenient formany programs or objects to use the same port or otherfacility for leaving and retrieving messages, but that meansthe operating system must spend additional time routingor dispatching the messages. On the other hand, if twoobjects create a bound port, no others can use it, so each canassume that any message left there is from the other object.During the 1992–1994 period, a standard called MPI(Message Passing Interface) was established by a groupof more than 40 industry organizations. It has since beensuperseded by MPI-2.Further ReadingGropp, William, Ewing Lusk, and Rajeev Thakur. Using MPI: PortableParallel Programming With the Message-Passing Interface.2nd ed. Cambridge, Mass.: MIT Press, 1999.“The Message Passing Interface (MPI) Standard.” Available online.URL: http://www-unix.mcs.anl.gov/mpi/. Accessed February6, 2000.Petzold, Charles. Programming Windows: the Definitive Guide to theWin32 API. 5th ed. Redmond, Wash.: Microsoft Press, 1998.Quinn, Michael J. Parallel Programming in C with MPI and OpenMP.New York: McGraw-Hill Education, 2003.microprocessorA microprocessor is an integrated circuit chip that containsall of the essential components for the central processingunit (CPU) of a microcomputer system such as a personalcomputer.Schematic of a simple microprocessor. The control unit is responsiblefor fetching and decoding instructions, as well as fetching orwriting data to memory. The Arithmetic Logic Unit (ALU) does theactual computing (including arithmetic and logical comparisons).The registers hold data being currently used by the ALU, while thecache contains instructions that have been pre-fetched because theyare likely to be needed soon.

304 microprocessorMicroprocessor development began in the 1960s whena new company called Intel was given a contract to developchips for programmable calculators for a Japanese firm.Marcian E. “Ted” Hoff headed the project. He decided thatrather than hard-wiring most of the calculator logic into thechips, he would create a general-purpose chip that couldread instructions and data, perform basic arithmetic andlogical functions, and transfer data between memory andinternal locations called registers.The resulting microprocessor, when combined with someRAM (random access memory), some preprogrammed ROM(Read Only Memory), and an input/output (I/O) chip constituteda tiny but complete CPU, soon dubbed “a computeron a chip.” This first microprocessor, the Intel 4004, hadonly a few thousand transistors, could handle data only 4bits at a time, and ran at 740 KHz (about one three-thousandththe speed of the latest Pentium IV chips).Intel gradually refined the chip, giving it the logic circuitsto enable it to perform additional instructions, moreinternal stack and register space, and 8 KB of space to storeprograms. The 8008 could handle 8 bits of data at a time,while the 8080 became the first microprocessor that wascapable of serving as the CPU for a practical microcomputersystem. Its descendants, the 8088 and 8086 (16-bit) poweredindustry-standard IBM-compatible PCs. Meanwhile,other companies such as Motorola (68000), Zilog (Z-80),and MOS Technology (6502) powered competing PCs fromApple, Atari, Commodore, and others.With the dominance of the IBM PC and its clones (seeibm pc), the Intel 80 × 86 series in turn dominated themicroprocessor market. (The x refers to successive digits, asin 80286, 80386, and 80486.) At the next level this nomenclaturewas replaced by the Pentium series, which is up tothe Pentium 4 as of 2002.The MITS Altair (1975) was the first microcomputer availablecommercially. It was generally purchased in kit form. While theAltair did not have much processing capacity, it aroused great interestand inspired other computer builders such as Apple’s Steve Wozniakand Steve Jobs. (Christopher Fitzgerald / The ImageWorks)According to a famous dictum called Moore’s Law, thedensity (number of transistors per cubic area) and speed (interms of clock rate) of microprocessors has roughly doubledevery 18 months to two years. Intel expects to be makingmicroprocessors with 1 billion transistors by 2007.Microprocessor and MicrocomputerA microcomputer is a system consisting of a microprocessorand a number of auxiliary chips. The microprocessorchip serves as the central processing unit (CPU). It containsa clock that regulates the flow of data and instructions(each instruction takes a certain number of clock cycles toexecute). There is also an index register that keeps track ofthe instruction being executed. A small number of locationscalled registers within the CPU allow for storing or retrievingthe data being used by instructions much more quicklythan retrieval from main memory (RAM).Typically, the instruction register advances to the nextinstruction. The instruction is fetched, decoded, and sent tothe CPU’s ALU (arithmetic logic unit) for processing. Dataneeded to be processed by the instruction are either fetchedfrom a register or, through an address register, fetched fromRAM. (Some processors store one operand for an arithmeticoperation in a special register called the accumulator.)Floating-point operations (those involving numbersthat can include decimal points) require special registersthat can keep track of the decimal position. Until the mid-1990s, many systems used a separate microprocessor calleda coprocessor to handle floating point operations. However,later chips such as the Pentium series integrate floatingpoint operations into the main chip.In order to function as the heart of a microcomputer,the CPU must communicate with a variety of other devicesby interacting with special controller chips. For example,there is a bus interface chip (see bus) that decodes memoryaddresses and routes requests to the appropriate devices onthe motherboard. When data is requested from memory, amemory controller must physically fetch the data from RAM(see memory). There is also a cache controller that interfaceswith one or two levels of high-speed cache memory (seecache). The algorithms implemented in the cache controlleraim to have the next instructions and the most-likely neededdata already in the cache when the CPU requests them.Other devices such as disk drives, modems, printers,and video cards are all connected to the CPU through input/output (I/O) interfaces that connect to the system bus. Mostof the devices connected to the bus have their own microprocessors.Software (see device driver) translates highlevelprogramming instructions (such as to open a file) tothe appropriate device commands.The CPU and many other devices also contain ROM (readonly memory) chips that have permanent basic instructionsstored on them (see bios). This enables the CPU and otherdevices to perform the necessary actions to enter into communicationwhen the system starts up (see boot sequence).New Features EmergeImprovements in microprocessors during the 1980sincluded wider data paths and the ability to address a larger

Microsoft Corporation 305amount of memory. For example, the Intel 80386 was thefirst 32-bit processor for PCs and could address 4 GB ofmemory. (Earlier processors such as the 80286 had to dividememory into segments or use paging to swap memory inand out of a smaller space to make it look like a larger one.)Over the years microprocessors tended to add more built-incache memory, enabling them to have more instructions ordata ready for immediate use.Another way to get more performance out of a microprocessoris to increase the speed with which instructionscan be executed. One technique, called pipelining, breaksthe processor into a series of segments, each of which canexecute a particular operation. Instead of waiting until aninstruction has been completely executed and then turningto the next one, a pipelined microprocessor moves theinstruction from segment to segment as its operations areexecuted, with following instructions moving into thevacated segments. As a result, two or more instructions canbe undergoing execution at the same time.In addition to pipelining, the Pentium series and otherrecent chips can have instructions executing simultaneouslyusing different arithmetic logic units (ALUs) or floating-pointunits (FPUs).Another way to improve instruction processing is to usea simpler set of instructions. First introduced during the1980s for minicomputers and high-end workstations (suchas the Sun SPARC series), reduced instruction set computer(RISC) chips have smaller, more uniform instructions thatcan be more easily pipelined, as well as many registers forholding the results of the intermediate processing. Duringthe 1990s, RISC concepts were also adopted in PC processordesigns such as the 80486 and Pentium (see reducedinstruction set computer).The latest major development has been the multicoremicroprocessor, which has two, four, or more separate processingunits. The Intel Core Duo and Core 2 Duo chipsand similar processors from AMD are now included in mostnew PCs.The equivalent of a supercomputer on a chip is on theway. Cisco’s 192-core Metro chip powers its most capablenetwork routers, while Nvidia’s GeForce 8800 graphics processorsports 128 cores. In addition to these specializedprocessors, in early 2007 Intel demonstrated a prototype80-core processor that could form the basis of a new generationof general-purpose processors.Another significant multicore processor architecture isthe Cell chip, developed by Sony, IBM, and Toshiba. Thischip includes a multithreaded (able to run multiple streamsof code) controller processor plus numerous architecturalfeatures that maximize efficiency and throughput. The firstappearance of this 2 “teraflop” (trillion calculations per second)chip was not on a scientific computer, but rather theSony Play Station 3—see game console.Multicore processors create new challenges for programmerswho have to create code that will apportion programtasks efficiently among the cores (see multiprocessing).In the new century, it is unclear when physical limitationswill eventually slow down the tremendous rate ofincrease in microprocessor power. As the chips get denserand smaller, more heat is generated with less surfacethrough which it can be removed. At still greater densities,quantum effects may also begin to be a problem. On theother hand, new technologies might take the elements ofthe processor down to a still smaller level (see molecularcomputing and nanotechnology).While the stand-alone desktop, laptop, or handheldcomputer is the most visible manifestation of the microprocessingrevolution, there are hundreds of “invisible”microprocessors in use for every visible computer. Todaymicroprocessors help monitor and control everything fromhome appliances to cars to medical devices (see embeddedsystems).Further ReadingKim, Ryan. “New Era of Game Devices Arrives: Sony and NintendoMeet the Challenge of Microsoft Xbox.” San FranciscoChronicle, November 13, 2006, p. F1, F6.Markoff, John. “Intel Prototype May Herald a New Age of Processing.”New York Times, February 12, 2007.Sperling, Ed. “Special Report: Inside the New Multicore Processors.”Electronic News, April 13, 2007. Available online.URL: http://www.edn.com/article/CA6434384.html. AccessedAugust 15, 2007.Stokes, John. Inside the Machine: An Illustrated Introduction toMicroprocessors and Computer Architecture. San Francisco: NoStarch Press, 2006.Tom’s Hardware. “CPU.” Available online. URL: http://www.tomshardware.com/cpu/.Accessed August 15, 2007.Microsoft CorporationMicrosoft Corporation (NASDAQ symbol: MSFT) is theworld’s largest computer software company, with almost80,000 employees worldwide and annual revenue exceeding$51 billion.Microsoft was founded in the mid-1970s by Bill Gates(see Gates, William) in order to sell his version of theBASIC programming language for early microcomputerssuch as the Altair 8800. The BASIC software was moderatelysuccessful, but it would be an operating system called MS-DOS (or PC-DOS) that would catapult Microsoft to industryleadership, thanks to an agreement with IBM, which introducedwhat would become the industry standard personalcomputer in 1982 (see ibm pc).In the mid-1980s Microsoft partnered with IBM todevelop OS/2, which was intended to be a more powerfulmultitasking operating system to replace DOS. However,Microsoft’s real interest was in the development ofWindows (see Microsoft Windows), which first becamesuccessful with version 3.0 in 1990. Meanwhile, Microsoftleveraged its experience with Windows to release MicrosoftOffice, which soon displaced WordPerfect, the previousmarket leader.Shifting Strategies and Legal IssuesMany observers have noted that Microsoft was slow in appreciatingthe importance of networking and particularly theWorld Wide Web in the mid-1990s. Novell was the marketleader in networking at the time, and Netscape’s graphical

306 Microsoft .NETbrowser had brought millions of users to the Web. Bill Gateshimself announced that the company would embark on a“net-centered” strategy, and this was reflected in the developmentof Windows NT, software for enterprise network andWeb servers, and the Internet Explorer browser, which dominatedthe desktop by the end of the decade.The continuing dominance of Microsoft operating systemsand office applications on the desktop provided thecash flow that gave the company the resources to catchup and then dominate almost any market it chose. However,this same dominance raised legal issues that wouldbe litigated through the late 1990s and beyond. Microsoftwas accused of using its knowledge of unpublishedWindows internal code to give products such as MicrosoftOffice an advantage over competitors. A more prominentaccusation was that Microsoft’s “bundling” of productssuch as Internet Explorer with Windows amounted to anunfair advantage over competitors such as Netscape, sinceExplorer would appear to be “free” to consumers. A seriesof civil actions under the name United States v. Microsoftresulted in a 2001 settlement with the U.S. Departmentof Justice that required Microsoft to share all informationabout its Windows API (see applications programminginterface) with competitors for at least five years. Thisresult was controversial, with defenders of Microsoft arguingthat the company had done no more than competeeffectively by using the results of its own previous work,while opponents argued that Microsoft’s coercive monopolypower had scarcely been dented by the settlement. In2008 the software giant continued to struggle with legalpressures. A European Union court has upheld previousrulings that the company had engaged in monopolistic andanticompetitive practices.Legal controversies aside, by the mid-2000s Microsoftwas facing some serious challenges, particularly from thepopularity of free and open-source software (see opensourcemovement). This is particularly true of the Webserver market, where the combination of the Apache Webserver and Linux has gained a major market share. Meanwhile,on the desktop, Windows Vista (released in January2007) did not sell as well as predicted during its firstsix months. The Apple Macintosh is maintaining its smallbut significant market share, and even Linux distributionssuch as Ubuntu are beginning to appear as an option onnew PCs. Microsoft’s flagship Office suite is facing competitionfrom products such as Open Office and particularlythe Web-based Google Apps. (In 2007 Microsoft beganto roll out Office Live Workspace, offering extensionsof Office applications rather than a complete suite.) Inother areas, the Microsoft Network (MSN) online servicehas struggled, while the company has done better withits Xbox gaming console as well as the best-selling gameHalo.Despite some stumbling and many controversies, Microsoft’svast resources and many ongoing research projects(with a $6 billion annual budget) make it likely the companywill continue to adapt and sometimes innovate, remaining astrong competitor for many years to come. For example, thecompany is now putting more resources into Web searchtechnology, an area that has been dominated by Google, aswell as eyeing applications as diverse as home media serversand social networking. Microsoft has also sought to expandits Internet presence by acquiring Yahoo!, the extensive butaging Web portal. (However, the first acquisition attemptwas rebuffed, and future plans remain uncertain as of mid-2008).Further ReadingBank, David. Breaking Windows: How Bill Gates Fumbled the Futureof Microsoft. New York: Free Press, 2001.Blakely, Rhys. “Microsoft’s Chief Executive Has Seen the Future—and the Future is Advertising: Steve Ballmer’s Plans for theComputer Software Giant Include Taking on Yahoo! andGoogle in Their Own Internet Territory.” Times Online (U.K.).Available online. URL: http://business.timesonline.co.uk/tol/business/industry_sectors/technology/article2570485.ece.Accessed October 2, 2007.Microsoft Corporation. Available online. URL: http://www.microsoft.com. Accessed October 2, 2007.Microsoft Timeline. Available online. URL: http://www.thocp.net/companies/microsoft/microsoft_company.htm. AccessedOctober 2, 2007.Microsoft Watch (eWeek). Available online. URL: http://www.microsoft-watch.com/. Accessed October 2, 2007.Page, William H., and John E. Lopatka. The Microsoft Case: Antitrust,High Technology, and Consumer Welfare. Chicago: Universityof Chicago Press, 2007.Slater, Robert. Microsoft Rebooted: How Bill Gates and Steve BallmerReinvented Their Company. New York: Portfolio, 2004.Wallace, James, and Jim Erickson. Hard Drive: Bill Gates and theMaking of the Microsoft Empire. New York: Wiley, 1992.Microsoft .NETMicrosoft .NET is a programming platform (see class andobject-oriented programming) that is intended to providea clear and consistent way for applications written ina variety of languages such as C++, C#, and Visual Basicto access Windows functions and to interact with otherprograms and services on the same machine or over theInternet..NET consists of the following main parts:• Base Class Library of data types and common functions(such as file manipulation and graphics) that isavailable to all .NET languages• Common Language Runtime, which provides thecode that applications need to run within the operatingsystem, manage memory, and so forth (“Commonlanguage” means it can be used for any .NET programminglanguage.)• ASP .NET, a class framework for building dynamicWeb applications and services (the latest version ofASP—see active server pages)• ADO .NET, a class framework that allows programsto access databases and data servicesThe latest version (as of 2008) is .NET Framework 3.5and is built into Windows Vista and Windows Server 2008.New components include:

Microsoft Windows 307• Windows Presentation Foundation, providing a userinterface based on 3D graphics, with objects describedusing Microsoft’s XAML markup language (see xml)• Windows Communication Foundation, providingways for .NET programs to communicate locally orover the network• Windows Workflow Foundation, for structuring andautomating tasks and transactions• Windows CardSpace, for managing digital identitiesin transactionsPlatformsIn the relationship between language and runtime libraries,Microsoft .NET, particularly when used with the C# language(see c#), is similar to the use of Java and its librariesas in the Java Enterprise Edition (EE). For Windows, .NEThas the advantage of being built specifically for that operatingsystem; however, Java has the advantage of running onall major platforms, including not only Windows, but alsoMac OS X and Linux, as well as being an open-source platform.(However, the open-source Mono project has developeda partial implementation of .NET for non-Windows aswell as Windows platforms.)Further ReadingBoehm, Anne. Murach’s ADO .NET 2.0 Database Programming withVB 2005. Fresno, Calif.: Murrach, 2007.Chappell, David. Understanding .NET. 2nd ed. Upper Saddle River,N.J.: Addison-Wesley Professional, 2006.MacDonald, Matthew. Beginning ASP.NET 3.5 in VB 2008: FromNovice to Professional. Berkeley, Calif.: APress, 2007..NET Framework Developer Center. Available online. URL: http://msdn2.microsoft.com/en-us/netframework/default.aspx.Accessed October 2, 2007.Troelsen, Andrew. Pro C# with .NET 3.0, Special Edition. Berkeley,Calif.: Apress, 2007.Walther, Stephen. ASP .NET Unleashed. Indianapolis: Sams, 2006.Microsoft WindowsOften simply called Windows, Microsoft Windows refers toa family of operating systems now used on the majority ofpersonal computers. Windows PCs run Intel or Intel-compatiblemicroprocessors and use IBM-compatible hardwarearchitecture.History and DevelopmentBy 1984, the IBM PC and its first “clones” from other manufacturersdominated the market for personal computers,quickly overtaking the previously successful Apple II andvarious machines running the CP/M operating system.Through a combination of initiative and luck, MicrosoftCEO Bill Gates had licensed what became its MS-DOS operatingsystem to IBM, while retaining the rights to license italso to the clone manufacturers (see also Gates, William).However, 1984 also brought Apple back into contentionwith the Macintosh. Using a graphical user interface(GUI) largely based on research done at Xerox’s Palo AltoResearch Center (PARC) in the 1970s, the Macintosh wasstrikingly more attractive and user-friendly than the alltext,command-line driven MS-DOS. As third parties beganto offer GUI alternative to DOS, Microsoft rushed to completeits own GUI, called Windows. Although it was actuallyannounced well before the coming of the Macintosh,Windows 1.0 was not released until 1985. Its poor fonts,graphics, and window operation made it compare unfavorablyto the Macintosh. Through the rest of the 1980s,Microsoft struggled to improve Windows. The acceptanceof Windows was aided by several large software manufacturerssuch as Aldus (PageMaker) writing software for thenew operating system as well as Microsoft’s designing orporting its own software such as the Excel spreadsheet.Windows 3.0, released in 1990, was considerablyimproved and began to attract significant numbers of usersaway from MS-DOS—based programs. Microsoft was alsogreatly aided by its ability to leverage its operating systemdominance to make it economically imperative for PC manufacturersto “bundle” Windows with new PCs.About the same time, Microsoft had been working withIBM on a system called OS/2. Unlike Windows, which wasactually a program running “on top of” MS-DOS, OS/2was a true operating system that had sophisticated capabilitiessuch as multitasking, multithreading, and memoryprotection. Microsoft eventually broke off its relationshipwith IBM, abandoned OS/2, but incorporated some of thesame features into a new version of Windows called NT(New Technology), first released in 1993. NT, which progressedthrough several versions, was targeted at the highendserver market, while the consumer version of Windowscontinued to evolve incrementally as Windows 95 and Windows98 (released in those respective years). These versionsincluded improved support for networking (including TCP/IP, the Internet standard) and a feature called “plug andplay” that allowed automatic installation of drivers for newhardware.Toward the end of the century, Microsoft began tomerge the consumer and server versions of Windows. Windows2000 incorporated some NT features and providedsomewhat greater security and stability for consumers.With Windows XP, released in 2001, the separate consumerand NT versions of Windows disappeared entirely, to bereplaced by home and “professional” versions of XP.Introduced in early 2007, Microsoft Windows Vistaincludes a number of new features, including a 3D userinterface (“Aero”), easier and more robust networking, builtinmultimedia capabilities (such as photo management andDVD authoring), improved file navigation, and desktopsearch. Perhaps the most important, if problematic, featureis enhanced security, including User Account Control,which halts suspect programs and requests permission forthem to continue. Although this makes it harder for malwareto get a foothold, many users find the constant “nags”to be annoying. (As of 2008 adoption of Vista has beenslower than expected, with many users opting to remainwith Windows XP.)The next version of Windows, with the working nameWindows 7, should be released around 2010. Its focus

308 Microsoft WindowsIntroduced in 2007, Microsoft Windows Vista features bettersecurity, a 3D look, new search facilities, and multimediafeatures. (Microsoft Corporation)appears to be a combination of “back to basics” (a responseto the sluggish performance of Vista) and more seamlessuser access to data and media from a variety of sources.User’s PerspectiveFrom the user’s point of view, Windows is a way to controland view what is going on with the computer. The userinterface consists of a standard set of objects (windows,menus, buttons, sliders, and so on) that behave in generallyconsistent ways. This consistency, while not absolute,reduces the learning curve for mastering a new application.Programs can be run by double-clicking on their icon onthe underlying screen (called the desktop), or by means ofa set of menus.Windows users generally manage their files througha component called Windows Explorer or My Computer.Explorer presents a treelike view of folders on the disk.Each folder can contain either files or more folders, whichin turn can contain files, perhaps nested several layers deep.Folders and files can be moved from place to place simplyby clicking on them with the mouse, moving the mousepointer to the destination window or folder, and releasingthe button (this operation is called dragging). Anotheruseful feature is called a context menu. Accessed by clickingwith the right-hand mouse button, the menu bringsup a list of operations that can be done with the currentlyselected object. For example, a file can be renamed, deleted,or sent to a particular destination.Windows includes a number of features designed tomake it easier for users to control their PC. Most settingscan be specified through windows called dialog boxes,which include buttons, check boxes, or other controls. Mostprograms also use Windows’s Help facility to present helppages using a standard format where related topics can beclicked. Most programs are installed or uninstalled usinga standard “wizard” (step-by-step procedure), and wizardsare also used by many programs to help beginners carry outmore complex tasks (see help systems).MultitaskingFrom the programmer’s point of view, Windows is a multitasked,event-driven environment (see multitasking).Programmers must take multitasking into account in recognizingthat certain activities (such as I/O) and resources(such as memory) may vary with the overall load on thesystem. Responsible programs allocate no more memorythan they need, and release memory as soon as it is nolonger needed. If the pool of free memory becomes too low,Windows starts swapping the least recently used segmentsof memory to the hard drive. This scheme, called virtualmemory, allows a PC to run more and larger programs thanwould otherwise be possible, but since accessing the harddrive takes considerably longer than accessing RAM, thesystem as a whole starts slowing down.Windows also has a rather small amount of memoryreserved for its GDI (Graphics Device Interface), a systemused for displaying graphical interface objects such as icons.If this resource pool (which has been made somewhat moreflexible in later versions of Windows) runs out, the systemcan grind to a halt.Programming PerspectiveProgrammers moving to Windows from more traditionalsystems (such as MS-DOS) must also deal with a new paradigmcalled event-driven programming. Most traditionalprograms are driven by an explicit line of execution throughthe code—do this, make this decision, and depending on it,do that—and so on. Windows programs, however, typicallydisplay a variety of menus, buttons, check boxes, and otheruser controls. They then wait for the user to do something.The user thus has considerable freedom to move about inthe program, performing tasks in different orders.A Windows program, therefore, is driven by events. Anevent is generally some form of user interaction such asclicking on a menu or button, moving a slider, or typinginto a text box. The event is conveyed by a message (seemessage passing) that Windows dispatches to the affectedobject. For example, if the user presses down (clicks) the leftmouse button while the mouse pointer is over a window, aWM_BUTTONDOWN message is sent to that window.Each of these interface objects (collectively called controls)has a message-handling procedure that identifiesthe message. The object must then have appropriate programcode that responds to each possible type of event. Forexample, if the user clicks on the File menu and then clickson Open, the code will display a standard dialog box thatallows for selecting the file to be opened.Fortunately for the programmer, Windows providesdevelopers with a large collection of types of windows, dialogboxes, and controls that can be displayed using a functioncall. For example, this code (after some preliminarydeclarations), displays a type of window called a list box:HWND MyWindow;hMyWindow = CreateWindow(“LISTBOX”,“Available Services”,WS_CHILD|WS_VISIBLE,0,0,100,200hwndParent,NULL,hINst,NULL);

Microsoft Windows 309Here the various parameters passed to the CreateWindowfunction specify the type of window, window title,characteristics, and location. The function returns a “windowhandle,” which is a pointer that holds the window’saddress and allows it to be accessed later.Most Windows programming environments, includingC++ and particularly, Visual Basic, now let program designersavoid having to specify code such as the above to createwindows and other objects. Instead, the programmer canclick and drag various objects onto a design screen to establishthe interface that will be seen by the program’s user.The programmer can then use Properties settings to specifymany characteristics of the screen objects without havingto explicitly program them.Microsoft and third-party developers also provide readymadeprogramming code in dynamic link libraries (DLLs).These resources (see library, program) can be called byany application, which can then use any object or functiondefined in the library. Windows also provides a facilitycalled OLE (Object Linking and Embedding). This lets anapplication such as a word processor “host” another applicationsuch as a spreadsheet. Thus, the Microsoft Word, forexample, can embed a Microsoft Excel spreadsheet into adocument, and the spreadsheet can be worked with usingall the usual Excel commands. In other words, OLE letsapplications make their features, controls, and functionalityaccessible to other applications. Indeed, collections ofcontrols are often packaged as OCX (OLE controls) andsold to developers.Despite all this available help, Windows presents a steeplearning curve for many programmers. There are hundredsof functions for handling interface objects, drawing graphics,managing files, controlling devices, and other tasks.With the growing use of object-oriented programming languages(see object-oriented programming and C++) inthe late 1980s and 1990s, Microsoft devised the MicrosoftFoundation Classes (MFC). This framework defines all ofthe interface objects and other entities (such as data structures)as C++ classes.Using MFC, a programmer, instead of calling a functionto create a window, creates an object of a particularWindow class. To customize a window, the programmercan use inheritance to derive a new window class.The various functions for controlling windows are thendefined as member functions of the window class. Thisuse of object-oriented, class-based design organizes muchof the great hodgepodge of Windows functions into alogical hierarchy of objects and makes it easier to masterand to use.For example, using the traditional Windows API (seeapplications programming interface) one puts a textstring into a list box using this code:LRESULT LRes;LRes = SendMessage(hMyListBox,LB_ADDSTRING,0,“Network Services”);(LRes is a number that will hold a code that says whetherthe item was successfully added)Using MFC, this code can be rewritten as:CListBox * pListBox;int nRes;nRes = pListBox->AddString (“Network Services”);Here a pointer is declared to an object of the ListBoxclass, and a member function of that class, AddString, isthen called. While this code may not look simpler, it uses aconsistent object-oriented approach.The new common framework for Windows programmingis called .NET. Closely integrated with the latestversions of Windows (XP SP2 and Vista), the class frameworkhas been revamped and expanded. .NET provides acommon language runtime (CLR) for access from differentlanguages such as C++, C#, and Visual Basic .NET. (SeeMicrosoft .NET.)TrendsBy just about any standard Microsoft Windows has achievedremarkable success, capturing and largely holding thelion’s share of the PC operating system market. However,Windows has been persistently criticized on grounds ofreliability and security. Perhaps feeling the pressure fromusers and potential regulators, Microsoft has placed greateremphasis on security in recent years; Windows Vista integratessecurity much more tightly into the structure of thesystem. However, as long as Windows is the most widelyused operating system, it will continue to be the biggest targetfor creators of viruses and other malware.Microsoft has included powerful facilities that allowWindows applications to be controlled by other applicationsor remotely (see scripting languages). Unfortunately,these facilities have proven to be quite vulnerable to computerviruses that can use them to damage systems connectedto the Internet. There seems to be a never-ending racebetween developers of program “patches” designed to plugsecurity holes and inventive, albeit malicious virus writers.Windows continues to face a variety of challenges. Theability to deliver applications directly through Web browserson any platform may make it less compelling for a user withsimple computing needs to pay the premium for a WindowsbasedPC. (For example, Google now delivers basic wordprocessing, spreadsheet, email, and other applications—seeapplication service provider.) Linux, too, may be graduallygaining a greater share on the desktop. Versions suchas the popular and frequently updated Ubuntu now installabout as easily as Windows, provide a similar user interface,and include a variety of software, including Open Office (seeLinux and open-source movement).While Windows still remains the dominant PC operatingsystem with tens of thousands of applications and atleast several hundred million users around the world, it islikely that the PC operating systems of 2020 will be as differentfrom today’s Windows as the latter is from the MS-DOS of the early 1980s.Further ReadingBellis, Mary. “The Unusual History of Microsoft Windows.” About.com. Available online. URL: http://inventors.about.com/od/mstartinventions/a/Windows.htm. Accessed August 15, 2007.

310 middlewareBott, Ed, Carl Siechert, and Craig Stinson. Microsoft Windows VistaInside Out. Redmond, Wash.: Microsoft Press, 2007.Minasi, Mark, and Byron Hynes. Administering Windows VistaSecurity: The Big Surprises. Indianapolis: Wiley/SYBEX, 2007.Simpson, Alan. Alan Simpson’s Windows XP Bible. 2nd ed. Indianapolis:Wiley, 2005.———. Alan Simpson’s Windows Vista Bible. Indianapolis: Wiley,2007.Smith, Ben, and Brian Komar. Microsoft Windows Security ResourceKit. 2nd ed. Redmond, Wash.: Microsoft Press, 2005.“Windows Products and Technologies History.” Microsoft. Availableonline. URL: http://www.microsoft.com/windows/WinHistoryIntro.mspx. Accessed August 15, 2007.middlewareOften two applications that were originally created for differentpurposes must later be linked together in order toaccomplish a new purpose. For example, a company sellingscientific instruments may have a large database of productspecifications, perhaps written in COBOL some years ago.The company has now started selling its products on theInternet, using its Web server and e-commerce applications(see e-commerce). Prospective customers of the Web siteneed to be able to access detailed information about theproducts. Unfortunately, the Web software (perhaps writtenin Java) has no easy way to get information from the company’sold product database. Rather than trying to convert theold database to a more modern format (which might taketoo long or be prohibitively expensive), the company maychoose to create a middleware application that can mediatebetween the old and new applications.There are a variety of types of middleware applications.The simplest and most general type of facility is the RPC(Remote Procedure Call), which allows a program runningon a client computer to execute a program running on theserver. DCE (Distributed Computing Environment) is amore robust and secure implementation of the RPC conceptthat provides file-related other operating system services aswell as executing remote programs.More elaborate architectures are used to link complexapplications such as databases where a program running onone computer on the network must get data from a server.For example, an Object Request Broker (ORB) is used in aCORBA (Common Object Request Broker Architecture) systemto take a data request generated by a user and find serverson the network that are capable of fulfilling the request(see coRBA).Middleware is often inserted into a program to allowfor better monitoring or control of distributed processing.For example a TP (transaction processing) monitor is amiddleware program that keeps track of a transaction thatmay have to go through several stages (such as point of saleentry, credit card processing, and inventory update). TheTP monitor can report whether any stage of the transactionprocessing failed (see transaction processing).Middleware can also be put in charge of load balancing.This means distributing transactions so that they are evenlyapportioned among the servers on the network, in order toavoid creating delays or bottlenecks.While use of middleware may not be as “clean” a solutionas designing an integrated system from the bottom up, theeconomic realities of a fast-changing information environment(particularly with regard to deployment on the Web)often makes middleware an adequate second-best choice.Further ReadingBritton, Chris, and Peter Bye. IT Architectures and Middleware:Strategies for Building Large, Integrated Systems. 2nd ed. UpperSaddle River, N.J.: Addison-Wesley Professional, 2004.Myerson, Judith M. The Complete Book of Middleware. Boca Raton,Fla.: CRC Press, 2002.Puder, Arno, Kay Römer, and Frank Pilhofer. Distributed SystemsArchitecture: A Middleware Approach. San Francisco: MorganKaufman, 2006.“What Is Middleware?” ObjectWeb. Available online. URL: http://middleware.objectweb.org/. Accessed August 15, 2007.military applications of computersWar has always been one of the most complex of humanenterprises. Even leaving actual combat aside, the U.S. militaryand defense establishment constitute a huge employer,research and training agency, and transportation network.Managing all these activities require sophisticated database,inventory, tracking, and communications systems. Whenthousands of private defense contractors of varying sizesare considered as part of the system, the complexity andscope of the enterprise become even larger.Specifically, military information technology applicationscan be divided into the following broad areas: logistics,training, operations, and battle management.LogisticsIt is often said that colonels worry about tactics while generalspreoccupy themselves largely with logistics. Logisticsis the management of the warehousing, distribution, andtransportation systems that supply military establishmentsand forces in the field with the equipment and fuel theyneed to train and to fight. Logistics within the United Statesis analogous to similar problems for very large corporations.The same bar codes, point of use terminals, and othertracking, inventory, and distribution systems that Amazon.com uses to get books quickly to customers while avoidingexcessive inventory are, in principle, applicable to modernizingmilitary logistic systems.An added dimension emerges when logistical supportmust be supplied to forces operating in remote countries,possibly in the face of efforts by an enemy to disrupt supply.Such considerations as efficient loading procedures toaccommodate limited air transport capacity, prioritizationof shipping to provide the most urgently needed items, andtransportation security can all come into play. (The militaryhas pioneered the use of retinal scanners and other systemsfor controlling access to sensitive areas. See biometrics.)The need for mobility and compactness makes laptopsand even palmtops the form factors of choice. Military or“milspec” versions of computer hardware are generally builtwith more rugged components and greater resistance toheat, moisture, or dust.

military applications of computers 311TrainingThe use of automated systems to provide training goes backat least as far as the World War II era Link trainer, whichused automatic controls and hydraulics to place traineepilots inside a moveable cockpit that could respond to theircontrol inputs. Today computer simulations with sophisticatedgraphics and control systems can provide highly realisticdepictions of flying a helicopter or jet fighter or drivinga battle tank. The military has even adapted commercialflight simulators for training purposes. Simulations canalso cover Special Forces operations and tactical decisionmaking. Indeed, many real-time simulations (RTS) sold aspopular commercial games and avidly played by young peoplealready contain enough realistic detail to be adoptedby the military as is. For example, the game Rainbow Six,based on operations in Tom Clancy novels, simulates tacticalcounterterrorism operations. In turn, the U.S. Army hasused a simulation game called Full Spectrum Warrior togive young gamers a taste of the military life.OperationsAircraft, ships, and land vehicles used by the military havebeen fitted with a variety of computerized systems. The“glass cockpit” in aircraft is replacing the increasinglyunmanageable maze of dials and switches with informationdisplays that can keep the pilot focused on the most crucialinformation while making other information readily available.Traditional keyboards and joystick-type controllerscan be replaced by touch screens and even by systems thatcan understand a variety of voice commands (see speechrecognition and synthesis). Similar control interfacescan be used in tanks or ships.Robotics offers a variety of intriguing possibilities forextending the reach of military forces while minimizingcasualties. Remote-control robots can be used to clearminefields, disarm roadside bombs, or perform reconnaissance.(The Predator armed reconnaissance drone was firstused successfully in anti-terrorist operations in Afghanistanin 2002.) Armed robots could assault enemy strong pointswithout risking soldiers. The development of autonomousrobots that can plan their own missions, select targets, andmake other decisions is a longer-term prospect that dependson the application of artificial intelligence in the extremelychallenging and chaotic battlefield environment.Battle ManagementBattle management is the ability to gather, synthesize, andpresent crucial information about the environment aroundthe military unit and enable military personnel to makerapid, accurate decisions about threats and the best way toneutralize them.The earliest example, the SAGE (Strategic Air GroundEnvironment) computer system, resulted from a massivedevelopment effort in the 1950s that strained the capacityof early vacuum tube-based computers to its limit. Thepurpose of SAGE was to provide an integrated tracking anddisplay system that could give the Strategic Air Command(SAC) complete real-time information about any Sovietnuclear bomber strikes in progress against the continentalUnited States Descendents of this system were able to trackballistic missiles.The Aegis system first deployed aboard selected navyships in the 1970s is a good example of a tactical battlemanagement system on a somewhat smaller scale. Aegis isa computerized system that can integrate information fromsophisticated shipboard radar and sonar arrays as well asreceiving and merging data from other ships and reconnaissanceassets (such as helicopters). The captain of anAegis cruiser or destroyer therefore has a real-time pictureshowing the locations, headings, and speeds of friendly andenemy ships, aircraft, and missiles. The system can alsoautomatically distribute the available munitions to mosteffectively engage the most threatening targets.Ultimately, the military hopes to give each unit in thefield and even individual soldiers a battle management displaythat would pinpoint enemy vehicles and other activity.Unpiloted drone aircraft such as the Predator can loiter overthe battlefield and feed video and other data into the battlemanagement system.While the ability to transmit and process large amountsof information can lead to strategic or tactical advantage, italso demands increased attention to security. If an enemycan jam the information processing system, its advantagescould be lost at a crucial moment. Worse, if an enemy can“spoof” the system or introduce deceptive data, the military’sinformation system could become a weapon in theenemy’s hands (see computer crime, encryption, informationwarfare and security).Beyond the BattlefieldToday’s military faces the challenge of diverse types of conflict(including counterinsurgency and peacekeeping), theneed to interact with cultures that may be unfamiliar tomost soldiers, and the need to deal with the psychologicalas well as physical casualties of war. A number of innovativeapplications of simulation and information technologyare being developed.In 2006 the U.S. military began to use a game called“Tactical Iraqi” in which soldiers must learn not only conversationalphrases, but the difference between appropriateand culturally insensitive gestures and actions.Another simulation, created at the University of SouthernCalifornia, uses VR technology (see virtual reality)to place soldiers suffering from posttraumatic stress disorder(PTSD) back into the combat environment under controlledconditions. The goal is to gradually desensitize theperson to the traumatic sights, sounds, and events.On the information and intelligence front, the need totranslate and interpret massive amounts of material in manylanguages in near real time has led the Defense AdvancedResearch Projects Agency (DARPA) to begin to develop asystem that would use separate “engines” for translation,interpretation, and summarization.Further ReadingEvans, Nicholas D. Military Gadgets: How Advanced TechnologyIs Transforming Today’s Battlefield. Upper Saddle River, N.J.:Prentice Hall, 2004.

312 minicomputer“How Military Robots Work.” HowStuffWorks. Available online.URL: http://science.howstuffworks.com/military-robot.htm.Accessed August 15, 2007.Jardin, Xeni. “VR Goggles Heal Scars of War.” Wired, August 22,2005. Available online. URL: http://www.wired.com/science/discoveries/news/2005/08/68575. Accessed August 15, 2007.Roland, Alex, and Philip Shiman. Strategic Computing: DARPA andthe Quest for Machine Intelligence, 1983–1993. Cambridge,Mass.: MIT Press, 2002.Strachan, Ian W. Jane’s Simulation and Training Systems, 2005–2006.Alexandria, Va.: Jane’s Information Group, 2005.Vargas, Jose Antonio. “Virtual Reality Prepares Soldiers for RealWar.” Washington Post, February 14, 2006, p. A01.Vizard, Frank, and Phil Scott. 21st Century Soldier: The Weaponry,Gear, and Technology of the Military in the New Century. NewYork: Popular Science/Time Inc., 2002.Minicomputers such as this DEC PDP-8 brought computing powerto many academic and scientific institutions for the first time. Theyalso encouraged a culture of cooperative software developmentthat led to such innovations as the UNIX operating system. (PaulPierce Computer Collection)minicomputerThe earliest general-purpose electronic digital computerswere necessarily large, room-size devices. In the 1960s,however, the replacement of tubes with transistors (andgradually, integrated circuits) gave designers the choice ofeither keeping computers large and packing more processingand memory capacity into them, or making smallercomputers that still had considerable power. The latteroption led to the minicomputer as contrasted with the largermainframe (see mainframe).Compared to mainframes, minicomputers often handleddata in smaller “chunks” (such as 16 bits as compared to 32or 64) and had a smaller memory capacity. Minicomputersalso tended to have more limited input/output (I/O) capacity.However, while large businesses still needed mainframes tohandle their large databases and volume of transactions, theminicomputer offered a relatively low cost (tens of thousandsof dollars rather than hundreds of thousands), computingfacility for scientific laboratories, university computing centers,industrial control, and various specialized needs.The pioneering and most successful minicomputer companywas the Digital Equipment Corporation (DEC). In1960, DEC introduced its PDP-1, which was followed in1965 by the quite successful PDP-8, which sold for only$18,000. By the early 1970s, DEC had been joined by competitorssuch as Data General and the availability of integratedmemory circuits (RAM) and microprocessors packedmore speed and capacity into each succeeding model.The minicomputer had several important effects on thedevelopment of computer science and the “computer culture”as a whole (see hackers and hacking). Minicomputersgave university students direct, interactive access tocomputers through time-sharing, Teletype terminals, or CRTdisplay terminals. Because minicomputers usually lackedthe extensive (and expensive) software packages that camewith mainframes, university users developed and eagerlyswapped software such as program editors and debuggers.This cooperative effort achieved its most striking result inthe development of the UNIX operating system.The reader has probably noticed that this article refersto minicomputers in the past tense. The minicomputerdidn’t really disappear, but rather was transmogrified. Bythe late 1980s and certainly the 1990s, the personal desktopcomputer had taken advantage of more powerful microprocessorsand ever more densely packed memory chips tocreate workstations that rivaled or exceeded the power ofestablished minicomputers. Eventually, the minicomputeras a category virtually disappeared, its functions taken overby machines such as the powerful graphics workstationsdeveloped by companies such as Sun Microsystems and SiliconGraphics and today’s forests of Web and file servers.Further ReadingFottral, Jerry. Mastering the AS/400: A Practical Hands-On Guide.Loveland, Colo.: 29th Street Press, 2000.Hoskins, Jim, and Roger Dimmick. Exploring IBM eServer Series.11th ed. Gulf Breeze, Fla.: Maximum Press, 2003.PDP-1 Computer Exhibit. Computer History Museum. Availableonline. URL: http://www.computerhistory.org/pdp-1/.Accessed August 15, 2007.Rifkin, Glenn, and George Harrar. The Ultimate Entrepreneur: TheStory of Ken Olsen and Digital Equipment Corporation. Chicago:Contemporary Books, 1988.

MIT Media Lab 313Schein, Edgar H. DEC Is Dead, Long Live DEC: The Lasting Legacyof Digital Equipment Corporation. San Francisco: Berrett-Koehler,2004.Minsky, Marvin Lee(1927– )AmericanComputer ScientistStarting in the 1950s, Marvin Minsky played a key role inthe establishment of artificial intelligence (AI) as adiscipline. Combining cognitive psychology and computerscience, Minsky developed ways to make computers functionin “brain-like” ways (see neural network) and thendeveloped provocative insights about how the human brainmight be organized.Marvin Minsky was born in New York City on August 9,1927. His father was a medical doctor, and Marvin provedto be a brilliant science student at the Bronx High School ofScience and the Phillips Academy. Although he majored inmathematics at Harvard, he also showed a strong interestin biology and psychology. In 1954, he received his Ph.D. inmathematics at Princeton. In 1956, he was a key participantin the seminal Dartmouth conference that established thegoals of the new discipline of artificial intelligence.One of the most important of those goals was to explorethe relationship between thinking in the human brain andthe operation of computers. Earlier in the century, researchinto the electrical activities of neurons (the brain’s information-processingcells) had led to speculation that thebrain functioned something like an intricate telephoneswitchboard, carrying information through millions of tinyconnections. During the 1940s, researchers had begun toexperiment with creating electronic circuits that mimickedthe activity of neurons.In 1957, Fran Rosenblatt built a device called a perceptron.It consisted of a network of electronic nodes thatcan transmit and respond to signals that function muchlike nerve stimuli in the brain (see neural network). Forexample, a perceptron could “recognize” shapes by selectivelyreinforcing the stimuli from light hitting an arrayof photocells. In 1969, Minsky and Seymour Papert coauthoreda very influential book on the significance andlimitations of perceptron research. Their work not onlyspurred research into neural networks and their possiblepractical applications, but also proved a strong impetus forthe new field of cognitive psychology, bridging the study ofhuman mental processes and the insights of computer science(see cognitive science).Meanwhile, Minsky had joined with John McCarthy (seeMcCarthy, John) to found the Artificial Intelligence Laboratoryat the Massachusetts Institute of Technology (MIT).In moving from basic perception to the higher order waysin which humans learn, Minsky developed the concept offrames. Frames are a way to categorize knowledge about theworld, such as how to plan a trip. Frames can be brokeninto subframes. For example, the trip-planning frame mighthave subframes about air transportation, hotel reservations,and packing. Minsky’s frames concept became a key to theconstruction of expert systems that today allow computers toadvise on such topics as drilling for oil or medical diagnosis(see expert systems and knowledge representation). Inthe 1970s, Minsky and his colleagues at MIT designed roboticsystems to test the ability to use frames to accomplish simplertasks, such as navigating around the furniture in a room.Minsky believed that the results of research into simulatingcognitive behavior had fruitful implications forhuman psychology. In 1986, Minsky published The Societyof Mind. This book suggests that the human mind is not asingle entity (as classical psychology suggests) or a systemwith a small number of often-warring subentities (as psychoanalysisasserted). It is more useful, Minsky suggests,to think of the mind as consisting of a multitude of independentagents that deal with different parts of the task ofliving and interact with one another in complex ways. Whatwe call mind or consciousness, or a sense of self is, therefore,what emerges from this ongoing interaction.Minsky continues his exploration of human psychologyand cognition with his latest book, The Emotion Machine.He has suggested that emotions are actually just alternativeways of thinking and accessing mental resources. In effect,the mind solves problems by looking among its “scripts”for those that seem applicable to the current situation, andthen reflecting on them and revising as necessary.Minsky continues his research at MIT. He has receivednumerous awards, including the ACM Turing Award (1969)and the International Joint Conference on Artificial IntelligenceResearch Excellence Award (1991).Further ReadingHenderson, Harry. Artificial Intelligence: Mirrors for the Mind. NewYork: Chelsea House, 2007.Marvin Minsky’s Home Page. Available online. URL: http://web.media.mit.edu/~minsky/. Accessed April 10, 2007.Minsky, Marvin. The Emotion Machine: Commonsense Thinking,Artificial Intelligence, and the Future of the Human Mind. NewYork: Simon & Schuster, 2006.———. The Society of Mind. New York: Simon & Schuster, 1988.MIT Media LabWhile often associated with innovations in computer interfacesand use of new technology, the Media Lab at the MassachusettsInstitute of Technology (MIT) is actually a partof the School of Architecture and Planning. This originis perhaps reflected in the organization’s multidisciplinaryresearch, including not only computer science and technologybut cognitive science, learning, art, and design.The lab was founded in 1985 by Nicholas Negroponteand former MIT President Jerome Wiesner (see Negroponte,Nicholas). As of 2006 the lab’s directorship wasassumed by Frank Moss. The lab is funded mainly by corporatedonations, though some projects receive governmentfunding or are done in partnership with other schools orother parts of MIT. There is some ongoing tension betweenthe specific needs and desires of corporate sponsors and thelab’s research interests, and over the disposition of intellectualproperty created by projects.

314 Mitnick, Kevin D.———. “The Media Lab’s New Pilot.” Technology Review. Availableonline. URL: http://www.technologyreview.com/article/16851/. Accessed October 2, 2007.Maeda, John. Maeda @ Media. New York: Universe Publications,2001.The Media Lab: Inventing a Better Future. Available online. URL:http://www.media.mit.edu/. Accessed October 2, 2007.Negroponte, Nicholas. Being Digital. New York: Vintage Books,1996.Mitnick, Kevin D.(1963– )AmericanComputer Cracker/Hacker, ConsultantThe MIT Media Lab has devised a variety of new ways for peopleto use computers. This is an innovative laptop sketchbook that createsanimations directly from drawings. (Sam Ogden / PhotoResearchers, Inc.)Emphases and ProjectsThe focus of most of the lab’s diverse projects is on findinginnovative and productive new ways for people to usecomputers and related technology. Recently there has beenan emphasis on more practical applications such as aiding“disabled, disadvantaged, [and] disenfranchised” peoplein becoming pioneers in using technology that everyonemay use someday. The “One Laptop per Child” project todevelop inexpensive computers for developing countries isalso a part of this effort.As of 2007 there were 27 separate research groups at thelab, including the following:• Object-Based Media—objects that can “understand”and describe their environment• Personal Robots—robots that interact with peoplesocially (see Breazeal, Cynthia)• Computing Culture—relationships among art, technology,and culture• molecular Machines—logical and mechanical devicesusing molecular-scale parts• Software Agents—programs that can serve as assistantsfor human activities• Ambient Intelligence—interfaces that are “pervasive,intuitive, and intelligent” (see Maes, Pattie)• Society of Mind—applying models of human cognitiveprocessing to machines (see Minsky, Marvin)• Affective Computing—developing computers that canrecognize and respond intelligently to human emotionFurther ReadingBourzac, Katherine. “Media Lab Courts Corporate Funding.”Technology Review, February 21, 2006. Available online.URL: http://www.technologyreview.com/Biztech/16383/?a=f.Accessed October 2, 2007.Once notorious for breaking into computers and stealinginformation, Kevin Mitnick later became a consultant andauthor on computer security.Mitnick was born October 6, 1963, in Van Nuys, California.With little parental supervision and few otherfriends, Mitnick became involved with “phone phreaks,”people who had learned to manipulate the long-distancephone system. However, Mitnick soon turned his attentionto breaking into computer systems. Mitnick first got introuble in high school for breaking into the school district’scomputer system. He also allegedly broke into the NorthAmerican Air Defense Command computer, though fortunatelywithout starting a nuclear war as in the movie WarGames. Despite being caught stealing Bell System technicalmanuals and put on probation, Mitnick continued breakinginto computers. In 1989 he received a one-year prisonsentence for breaking into computers at MCI and DigitalEquipment Corporation. After getting out he violated hisprobation by stealing more Bell documents, and a warrantwas issued for his arrest.Mitnick then went underground, eluding authoritiesfor two years and using a variety of fake identities. However,when Mitnick broke into the computer of physicistand computer security expert Tsutomu Shimomura andstole a large number of documents and programs, andlater taunted him on the phone, Shimomura resolved totrack down the intruder. Shimomura and several otherexperts set up a tracking program at The Well (a computerconferencing system where Mitnick had stashed the stolenmaterial). Mitnick attempted to disguise his location byrouting calls through a phone company switching officein Raleigh, North Carolina, but when Shimomura figuredout that Mitnick was calling from Raleigh, he and a Sprintphone technician drove around Raleigh scanning for thecalls from Mitnick’s cellular modem, tracking him to hisapartment building. They then called federal agents, whoarrested Mitnick.Mitnick became a cause célèbre in the hacker community.The controversy was heightened by two books writtenabout the case, one by Shimomura and New York Timesjournalist John Markhoff and the other by Jonathan Littman,who argued that the charges against Mitnick wereoverinflated and government prosecutors overzealous.

modem 315Author and Security ExpertAfter serving a total of five years in prison (four and a halfbefore he was actually tried), Mitnick was released in January2000 on condition that he not use any form of computernetwork. (Mitnick appealed this restriction and it was laterlifted.) Meanwhile, Mitnick then wrote two books describingboth technical and psychological or “social engineering”methods used by hackers, and giving advice on howcomputer owners can protect themselves. Mitnick currentlyowns his own computer security company.Further ReadingGoodell, Jeff. The Cyberthief and the Samurai: The True Story ofKevin Mitnick—and the Man Who Hunted Him Down. NewYork: Dell, 1996.Littman, Jonathan. The Fugitive Game: Online with Kevin Mitnick.Boston: Little, Brown, 1996.Mitnick, Kevin D. The Art of Deception: Controlling the Human Elementof Security. Indianapolis: Wiley, 2002.———. The Art of Intrusion: The Real Stories behind the Exploits ofHackers, Intruders & Deceivers. Indianapolis: Wiley, 2005.Shimomura, Tsutomo, and John Markoff. Takedown: The Pursuitand Capture of Kevin Mitnick, America’s Most Wanted ComputerOutlaw—by the Man Who Did It. New York: Hyperion,1996.modeling languagesMost significant modern software projects are not simplyprograms, however large, but complex systems of programsor modules. Such systems have to be designed and fullydescribed before they can be coded. Traditional methodsmay be adequate for simple programs (see flowchart andpseudocode), but they do not capture many aspects ofdesign and behavior. When used for software projects andinformation systems, modeling languages allow for componentsand their relationships to be described and diagrammedsystematically.UMLUnified Modeling Language, or UML, is the most widelyused modeling language for software projects. UMLdescribes software in three ways: the functions of the systemas seen by the user; the system’s objects, attributes, andrelationships (see class and object-oriented programming);and how the system behaves, as seen by how objectsinteract and how their state changes. A variety of diagramscan be used to summarize this information:• activity—describes processes and data flow, as in businesstransactions• class—shows classes and data types and their relationships• communication—the messages (data) exchangedbetween classes• components—the major parts of the system• composite structure—the internal structure of a classor component• deployment—where the system is executed, includinghardware and software servers• interaction overview—a way to show the overall flowof control• object—objects and relationships at a particular pointin time• package—organization of elements of the model intopackages, showing dependencies• sequence—how messages are organized chronologically• state machine—the possible states an object or interactioncan have, and how each type of input changesthe state (see finite-state machine)• timing—how the state of an object changes over timeas it responds to events• use case—actors and actions (such as a customermaking a purchase)Some critics believe that UML can be overused, leadingto large, complex descriptions and numerous diagramsthat can be almost as hard to work with as the code itself.Further, the UML itself has to be maintained, being revisedand expanded as the design and code change. Integratingmodeling functions into programming environments andproviding a seamless path from model to specification tocode is a possible alternative, though hard to realize inpractice.Further ReadingChonoles, Michael Jesse, and James A. Schardt. UML 2 for Dummies.New York: Wiley, 2003.“Introduction to the Diagrams of UML 2.0.” Agile Modeling. Availableonline. URL: http://www.agilemodeling.com/essays/umlDiagrams.htm. Accessed October 3, 2007.Miles, Russ, and Kim Hamilton. Learning UML 2.0. Sebastapol,Calif.: O’Reilly, 2006.UML Forum. Available online. URL: http://www.uml-forum.com/.Accessed October 3, 2007.UML Resource Page. (Object Management Group). Availableonline. URL: http://www.uml.org/. Accessed October 3, 2007.modemAs computers proliferated and users experienced an increasingneed to exchange data and communicate, it becamelogical to tap into the telephone system, a communicationstechnology that already linked millions of places aroundthe world.The problem is that the conventional telephone is ananalog rather than digital device. It converts sound (such asspeech) into continuously varying electrical signals. Computers,on the other hand, use discrete pulses of on/off(binary) data. However, it proved relatively easy to builda device that could “modulate” the data pulses, imposingthem on a sort of carrier wave and thus convertingthem into electrical signals that could travel along telephonelines. At the other end of the line a corresponding

316 molecular computingdevice could “demodulate” that telephone signal, convertingit back into data pulses. This “modulator-demodulator”device is known as a modem for short.A modem contains both the modulator and demodulatorcircuit, with a connection to a cable and a phone jack onone side and a connection to the computer on the other. Thecomputer connection can be provided by connecting to astandard port on the outside of the PC (see serial port) orby mounting the modem on a card that slides into the PC’sinternal bus (see bus) and connects to the outside phoneline through a jack. The modem must also have a componentthat generates the dialing pulses needed to establish aphone connection.The first modems for PCs appeared in the early 1980sand were very slow by modern standards, transmittingdata at 300 bps (bits per second). However, speed steadilyimproved, reaching 1,200, 2,400, 9,600 and so on up to56,000, which is about the maximum practical speed forthis technology over ordinary phone lines.Phone lines are far from hermetically sealed, and randomfluctuations called “line noise” can sometimes be misinterpretedby the modem as part of the data signal, leadingto errors. However, modern modems include sophisticatederror-correcting protocols (see error correction)and can automatically negotiate with each other to reducedata transmission speed over noisy lines. Data compressiontechniques also make it possible to have an effectivelygreater transmission speed by packing more informationinto less data. In the 1990s, there were some problemscaused by competing standards, but today most modemsmeet the International Telecommunications Union (ITU)v.90 standard for 56 kbps transmission. The modem is nowa reliable, stable commodity included as standard equipmentin most new PCs.Modems have met with increasing competition as ameans to connect homes to the Internet. Data can be transmittedover video cable or special phone lines (such asDSL or ADSL) at 20–30 times faster than for a modem onan ordinary phone line (see broadband). However, besidesbeing two to three more times expensive than typical dialupservices, broadband technologies tend to be concentratedin urban areas. Nevertheless, the versatile modemis becoming a secondary means of data communication formost users.laws and processes to solve problems (see analog computer).One of the most intriguing approaches is basedupon chemistry and biology rather than electronics.Consider that all living things possess a detailed “databasesystem” of coded information, namely, the DNAsequences that define their genetic code. DNA consists ofstrands composed of four bases: adenine (A), cytosine (C),guanine (G), and thymine (T). There are a variety of waysin which biologists can “sequence” a strand of DNA, that is,determine the order of bases in it. It is also relatively easy tomake many copies of a given chain by using the polymerasechain reaction (PCR) technique.This stockpile of coded DNA strands can be used to solvecombinatorial problems. This type of problem becomesexponentially harder to solve through “brute force” computationas the number of elements increases. An exampleis the famous “Traveling Salesman Problem.” Here the goalis to determine a route that visits all of a list of cities whilevisiting each city only once.As Leonard Edelman pointed out in his 1994 article inScience, a DNA-based approach to the traveling salesmanproblem begins by assigning two sets of four bases to eachcity. Next, a similar DNA combination is assigned to eachavailable direct route between two cities, using half (fourbases) of the sequence assigned to the respective cities.That is, if one city is coded TCGTAGCT and another cityis coded GCATTAAG, then a route from the first city to thesecond would be coded TCGTTAAG.When binding one DNA strand to another, T alwaysbinds with A, and C always binds with G. Therefore a “complement”can be defined that will bind with a given DNAstring. For example, the complement of TCGTAGCT wouldbe AGCATCGA.Next, the strands representing the complements for thecities are mixed with the ones representing routes. If a citycomplement runs into a route containing that city, theybind together. The other end (representing the other end ofthe route) might then encounter another route strand, thusextending the route to a third city and so on, until there arestrands representing potentially complete routes to all theFurther ReadingBanks, Michael A. The Modem Reference: The Complete Guide toPC Communications. 4th ed. Medford, N.J.: CyberAge Books,2000.Brain, Marshall. “How Modems Work.” Available online. URL:http://www.howstuffworks.com/modem.htm. Accessed August15, 2007.Glossbrenner, Alfred, and Emily Glossbrenner. The CompleteModem Handbook. New York: MIS Press, 1995.molecular computingWhile the electronic digital computer is by far the mostprevalent type of calculating device in use today, it is alsopossible to build computational devices that exploit naturalMolecular computing takes advantage of the properties of moleculessuch as DNA to create what is in effect a massive array ofparallel processors. In this example, DNA strands can be coded torepresent cities and possible routes between them so that they willchemically solve the Traveling Salesman Problem.

monitor 317cities. After the mixing and combining is completed, separationand sequencing techniques can be used to find theshortest strand that includes all the cities. This representsthe solution to the problem.The attractiveness of molecular computing lies in itsbeing “massively parallel” (see multiprocessing). Althoughmolecular operations are individually much slower thanelectronics, DNA strands can be replicated and assembledin great numbers, potentially allowing them to go throughquintillions (10 18 ) of combinations at the same time. In1996, Dan Boneh designed an approach using DNA combinationsthat could be used to break the Data EncryptionStandard (DES) encryption scheme by testing huge numbersof keys simultaneously.In 2002 researchers at the Weizmann Institute of Sciencein Rehovot, Israel, announced that they had constructeda DNA computer that could perform 330 teraflops(trillions of operations per second). Two years later Weizmannresearchers described their new DNA computer,which could be used to diagnose and treat cancer on thecellular level.Although this application suggests the potential powerin molecular computing, the approach has significantdrawbacks. There are many ways that damage can occurto DNA strands during combination and processing, leadingto errors. Even for the combinatorial problems that aremolecular computing’s strong suit, conventional electroniccomputers using large arrays of parallel processors are ableto offer comparable power and a much easier interface.However, molecular computing illustrates the rich way inwhich information and information processing are embeddedin nature and the potential for harnessing it for practicalapplications.Further ReadingAmos, Martyn. Genesis Machines: The New Science of Biocomputing.New York: Overlook, 2008.———. Theoretical and Experimental DNA Computation. New York:Springer, 2005.———, ed. Cellular Computing. New York: Oxford UniversityPress, 2004.Calude, Christian, and Gheorghe Păun. Computing with Cells andAtoms: An Introduction to Quantum, DNA and Membrane Computing.New York: Routledge, 2001.Păun, Gheorghe, Grzegorz Rozenberg, and Arto Salomaa. DNAComputing: New Computing Paradigms. New York: Springer,1998.Ryu, Will. “DNA Computing: A Primer.” Ars Technica. Availableonline. URL: http://arstechnica.com/reviews/2q00/dna/dna-1.html. Accessed August 15, 2007.monitorAs designers strove to make computers more interactiveand user-friendly, the advantages of the cathode ray tube(CRT) already used in television became clear. Not onlycould text be displayed without wasting time and resourceson printing but the individually addressable dots (pixels)could be used to create graphics. While such displays wereused occasionally in defense and research systems in the1950s, the first widespread use of CRT video monitors camewith the new generation of smaller computers developedin the 1960s (see minicomputer). Since such computerswere often used for scientific, engineering, industrial control,and other real-time applications, the combination ofvideo display and keyboard (i.e., a Video Display Terminal,or VDT) was a much more practical way for users to overseethe activities of such systems. (This oversight function alsoled to the term monitor.)A monitor can be thought of as a television set thatreceives a converted digital signal rather than regular TVprogramming. To send an image to the screen, the PC firstassembles it in a memory area called a video buffer (modernvideo cards can store up to 64 MB of complex graphicsdata. See computer graphics). Ultimately, the graphics arestored as an array of memory locations that represent thecolors of the individual screen dots, or pixels. The videocard then sends this data through a digital to analog converter(DAC), which converts the data to a series of voltagelevels that are fed to the monitor.The monitor has electron “guns” that are aimedaccording to these voltages. (A monochrome monitor hasA standard computer monitor works much like an ordinary color TV set. The difference is that the signal is derived not from a broadcast program,but from the contents of video memory as processed and converted by the computer’s graphics card.

318 Moore, Gordon E.only one gun, while a color monitor, like a color TV, hasseparate guns for red, blue, and green. The electrons fromthe guns pass through a lattice called a shadow mask,which keeps the beams properly separated and aligned.Each pixel location on the inner surface of the CRT iscoated with phosphors, one that responds to each of thethree colors.The intensity of the beam hitting each color determinesthe brightness of the color, and the mixture of the red, blue,and green color levels determines the final color of thepixel. (Today’s graphics systems can generate more than16.7 million different colors, although the human eye cannotmake such fine distinctions.)The beam sweeps along a row of pixels and then turnsoff momentarily as it is refocused and set to the nextrow. The process of scanning the whole screen in thisway is repeated 60 times a second, too fast to be noticedby the human eye. Less expensive monitors were sometimesdesigned to skip over alternate lines on each passso that each line is refreshed only 30 times a second. Thisinterlaced display can have noticeable flicker, and fallingprices have resulted in virtually all current monitorsbeing noninterlaced.Another factor influencing the quality of a CRT monitoris the size of the screen area devoted to each pixel. Thespacing in the shadow mask that defines the pixel areas iscalled the dot pitch. A smaller dot pitch allows for a sharperimage.During the 1980s, emerging video standards offeredincreasing screen resolution and number of colors, startingwith the first IBM PC color displays at 320 × 200 pixels, 4colors up to video graphics array (VGA) displays at 1024 ×768 pixels and at least 256 colors. The latter is consideredthe minimum standard today, with some displays going ashigh as 1600 × 1200 with millions of colors.Meanwhile, the CRT monitor became a commodity itemwith steadily falling prices. A 19-inch color monitor nowcosts only a few hundred dollars. Ergonomically, it is importantfor the combination of display size and resolution to beset to avoid eyestrain. There has been some concern aboutusers receiving potentially damaging nonionizing radiationfrom CRT displays, but studies have generally been unableto confirm such effects. Modern monitors are generallydesigned to minimize this radiation.CRT displays are too bulky and power-hungry for laptopor handheld devices, which generally use liquid crystaldisplays (LCDs). In recent years large LCD displays suitablefor desktop systems have also declined in price, and arerapidly becoming the display of choice even for regular PCs(see flat-panel display).Further ReadingCarmack, Carmen, and Jeff Tyson. “How Computer MonitorsWork.” Available online. URL: http://www.howstuffworks.com/monitor.htm. Accessed August 15, 2007.Goldwasser, Samuel M. “Notes on the Troubleshooting and Repairof Computer and Video Monitors.” Available online. URL:http://www.repairfaq.org/sam/monfaq.htm. Accessed August15, 2007.Moore, Gordon E.(1929– )AmericanEntrepreneurThe microprocessor chip is the heart of the modern computer,and Gordon Moore deserves much of the credit forputting it there. His insight into the computer chip’s potentialand his business acumen and leadership would lead to theearly success and market dominance of Intel Corporation.Moore was born on January 3, 1929, in the small coastaltown of Pescadero, California, south of San Francisco. Hisfather was the local sheriff and his mother ran the generalstore. Young Moore was a good science student, and heattended the University of California, Berkeley, receivinga B.S. in chemistry in 1950. He then went to the CaliforniaInstitute of Technology (Caltech), earning a dual Ph.D. inchemistry and physics in 1954. Moore thus had a soundbackground in materials science that would help preparehim to evaluate the emerging research in transistors andsemiconductor devices that would begin to transform electronicsin the later 1950s.After spending two years doing military research atJohns Hopkins University, Moore returned to the WestCoast to work for Shockley Semiconductor Labs in PaloAlto. However, Shockley, who would later share in a NobelPrize for the invention of the transistor, alienated many ofhis top staff, including Moore, and they decided to starttheir own company, Fairchild Semiconductor, in 1958.Moore became manager of Fairchild’s engineeringdepartment and, the following year, director of research.He worked closely with Robert Noyce, who was developinga revolutionary process for placing the equivalent of manytransistors and other components onto a small chip.Moore and Noyce saw the potential of this integratedcircuittechnology for making electronic devices includingclocks, calculators, and especially computers vastly smalleryet more powerful. In 1965 he formulated what becamewidely known in the industry as Moore’s law. This predictionsuggested that the number of transistors that could beput in a single chip would double about every year (laterit would be changed to 18 months or two years). Remarkably,Moore’s law would still hold true into the 21st century,although as transistors get ever closer together, the laws ofphysics begin to impose limits on current technology.Moore, Noyce, and Andrew Grove found that they couldnot get along well with the upper management in Fairchild’sparent company, and decided to start their own company,Intel Corporation, in 1968, using $245,000 plus $2.5million from venture capitalist Arthur Rock (see GroveAndrew and Intel Corporation). They made the developmentand application of microchip technology the centerpieceof their business plan. Their first products wereRAM (random access memory) chips (see chip).Seeking business, Intel received a proposal from Busicom,a Japanese firm, for 12 custom chips for a new calculator.Moore and Grove were not sure they were ready toundertake such a large project, but then Ted Hoff, one oftheir first employees, suggested that they could build a chip

motherboard 319that had a general-purpose central processing unit (CPU)that could be programmed with whatever instructions wereneeded for each application. With the support of Moore andother Intel leaders, the project got the go-ahead. The resultwas the microprocessor, and it would revolutionize not onlycomputers, but just about every sort of electronic device(see microprocessor).Under the leadership of Moore, Grove, and Noyce, the1980s would see Intel established as the leader in microprocessors,starting when IBM chose Intel microprocessorsfor its hugely successful IBM PC. IBM’s competitors, suchas Compaq, Hewlett-Packard, and later Dell, would also useIntel microprocessors for most of their PCs.In his retirement, Moore enjoyed fishing at his summerhome in Hawaii while being active as a philanthropist.Moore gave a record-setting $600 million donation toCaltech in 2001, and in 2003 Moore and his wife, Betty, setup a $5 billion foundation focusing on environmental andsocial initiatives. Moore has also had a long-time interest inSETI, or the search for extraterrestrial intelligence.Moore has been awarded the prestigious National Medalof Technology (1990), the IEEE Founders Medal, the W.W. McDonnell Award, as well as the Presidential Medal ofFreedom (2002). In 2003 Moore was elected a fellow of theAmerican Association for the Advancement of Science.Further ReadingBurgelman, Robert, and Andrew S. Grove. Strategy Is Destiny. NewYork: Simon & Schuster, 2001.“Calibrating Gordon Moore.” Caltech News 36 (2002). Availableonline. URL: http://pr.caltech.edu/periodicals/CaltechNews/articles/v36/moore.html. Accessed May 5, 2007.“Laying Down the Law.” Technology Review 104 (May 2001): 65.Available online. URL: http://www.technologyreview.com/Infotech/12403/. Accessed October 3, 2007.Mann, Charles. “The End of Moore’s Law?” Technology Review 103(May 2000): 42. Available online. URL: http://www.technologyreview.com/Infotech/12090/.Accessed October 3, 2007.motherboardLarge computers generally had separate large cabinets tohold the central processing unit (CPU) and memory (seemainframe). Personal computers, built in an era of integratedelectronics, use a single large circuit board to serveas the base into which chips and expansion boards areplugged. This base is called the motherboard.The motherboard has a special slot for the CPU (seemicroprocessor). Data lines (see bus) connect the CPU toRAM (see memory) and various device controllers. Besidescompactness, use of a motherboard minimizes the use ofpossibly fragile cable connections. It also provides expansioncapability. Assuming its pins are compatible with theslot and it is operationally compatible, a PC user can plug amore powerful processor into the slot on the motherboard,upgrading performance. Memory expansion is also providedusing a row of memory sockets. Memory, originallyinserted as rows of separate chips plugged into individualsockets, is now provided in single modules called DIMMsthat can be easily slid into place.Schematic of a PC motherboard. Note the sockets into which additionalRAM memory chips (DIMM) modules can be inserted, aswell as the slots for ISA and PCI standard expansion cards.The motherboard also generally includes about six general-purposeexpansion slots. These follow two differentstandards, ISA (industry standard architecture) and PCI(peripheral component interconnect) with PCI now predominating(see bus). These slots allow users to mix andmatch such accessories as graphics (video) cards, disk controllers,and network cards. Additionally, the motherboardincludes a chip that stores permanent configuration settingsand startup code (see bios), a battery, a system clock,and a power supply.The most important factors in choosing a motherboardare the type and speeds of processor it can accommodate,the bus speed, the BIOS, system chipset, memory and deviceexpansion capacity, and whether certain features (suchas video) are integrated into the motherboard or providedthrough plug-in cards. Generally, users must work withinthe parameters of their system’s motherboard, althoughknowledgeable people who like to tinker can buy a motherboardand build a system “from scratch” or keep their currentperipheral components and upgrade the motherboard.Further ReadingPalmer, Charlie. How to Build Your Own PC: Save a Buck and Learna Lot. West St. Paul, Minn.: HCM Publishing, 2005.Rosenthal, Morris. Build Your Own PC. 4th ed. Emeryville, Calif.:McGraw-Hill/Osborne, 2004.Soderstrom, Thomas. “Beginner’s Guide to Motherboard Selection.”Tom’s Hardware. Available online. URL: http://www.tomshardware.com/2006/07/26/beginners_guide_to_motherboard_selection/. Accessed August 15, 2007.Wilson, Tracy V. “How Motherboards Work.” Available online. URL:http://www.howstuffworks.com/motherboard.htm. AccessedAugust 15, 2007.

320 Motorola CorporationMotorola CorporationMotorola Corporation (NYSE symbol: MOT) is a venerableAmerican manufacturer of communications and otherelectronic equipment, including computers and cell phones.The company was founded in 1928 by Paul and JosephGalvin as Galvin Manufacturing Corporation. The nameMotorola arose in the early 1930s when the company beganmanufacturing car radios (“motor” as in car plus “ola” as inVictrola), and the company’s name was officially changed toMotorola Corporation in 1947. Many of the company’s subsequentproducts would relate to radio, such as police carradios, walkie-talkies, and cordless phones. Motorola introducedthe first “brick” cell phone in 1983. Today Motorolais best known for stylish cell phones with names such asRAZR and KRZR.Motorola also played an important role in building theglobal satellite communications network through the IridiumCompany in the late 1990s. However, the companyfiled for bankruptcy when it could not attract enough telecommunicationscompanies to use its services.MicroprocessorsThough the market came to be dominated by Intel (seeIntel Corporation), Motorola was an important manufacturerof microprocessors in the 1980s and 1990s. Motorola’s68000 series micrprocessors and later PowerPC series(developed jointly with IBM) were used in several computersystems of the early 1980s, including the CommodoreAmiga and the Atari ST, as well as workstation terminals(Sun) and UNIX systems. The greatest consumer impact,however, would be its use in the Apple Macintosh, startingin 1984.The later Power PC (PPC) series, launched in 1993, is aRISC processor (reduced instruction set, see risc). This lineof processors would be used in the Power Mac and otherMacintosh systems until Apple adopted Intel chips in 2006.Motorola’s fortunes declined in the early to mid 2000s.In 2001 Motorola spun off its defense-related business toGeneral Dynamics. It spun off its computer chip manufacturingdivision in 2004 as Freescale Semiconductors, andin 2007 Motorola sold its embedded communications chipunit to Emerson Electric. Motorola has said it would focuson its core communications business.Despite strong demand for its cell phones and othermobile devices, in 2006 Motorola earned 42.9 billion inrevenue, but its profits were down 48 percent from the previousyear. This was attributed to strong price competition.In 2007 the company said it would cut 3,500 of its 66,000employees.Further ReadingMotorola Web site. Available online. URL: http://www.motorola.com/. Accessed October 3, 2007.Pande, Meter S., Robert P. Neumann, and Roland R. Cavanagh.The Six Sigma Way: How GE, Motorola, and Other Top CompaniesAre Honing Their Performance. New York: McGraw-Hill,2000.Petrakis, Harry Mark. The Founder’s Touch: The Life of Paul Galvinof Motorola. 3rd ed. Chicago: Motorola University Press,1991.Schoenborn, Guenter. Entering Emerging Markets: Motorola’s Blueprintfor Going Global. Rev. ed. New York: Springer, 2006.Wray, William C., Joseph D. Greenfield, and Ross T. Bannatyne.Using Microprocessors and Microcomputers: The Motorola Family.4th ed. Upper Saddle River, N.J.: Prentice Hall, 1998.mouseTraditionally, computers were controlled by typing in commandsat the keyboard. However, as far back as the mid-1960s researchers had begun to experiment with providingusers with more natural ways to interact with the machine.In 1965, Douglas Engelbart at the Stanford Research Institute(SRI) devised a small box that moved over the desk onwheels and was connected to the computer by a cable. Asthe user moved the box around, it sent signals representingits motion. These signals in turn were used to draw apointer on the screen. Engelbart found that this system wasless taxing on users than alternative such as light pens orjoysticks (see Engelbart, Douglas).This device, dubbed a “mouse,” remained largely a laboratorynovelty. In the 1970s, however, Xerox designed amouse-driven graphical user interface for its Alto system,which saw only limited use. In 1984, however, Apple intro-This Microsoft wireless optical mouse eliminates moving parts andwires for smooth, accurate, reliable performance. (MicrosoftCorporation)

MS-DOS 321duced the mouse to millions of users of its Macintosh. Bythe early 1990s, millions more users were switching theirIBM-compatible PCs from text commands (see ms-dos)to the mouse-driven Windows interface. (See MicrosoftWindows.) Today a desktop PC without a mouse would beas unthinkable as one without a keyboard.Meanwhile, the mouse became smaller and sleeker.Instead of wheels, the contemporary mouse uses a rollingball that turns two adjacent rollers inside the mouse. Amouse pad with a special surface is generally used to provideuniform traction. A newer type of mouse uses opticalsensors instead of rollers to sense its changing position, anddoes not require a mouse pad. Some mice are also cordless,using infrared or wireless data connections.Since mice are generally impracticable for laptop use(see portable computers), designers have offered a varietyof alternatives. These include a trackball (a rolling ball builtinto the keyboard), a touch-sensitive finger pad, or a smallstub that can be moved like a joystick by the fingertip.Most mice now have at least two buttons. Generally, theleft button is used for selecting objects, opening menus, orlaunching programs. The right button is used to bring up amenu of actions that can be done with the selected object.Activating a button is called clicking. It is the operating systemthat assigns significance to clicking or double-clicking (clickingtwice in rapid succession) or dragging (holding a buttondown while moving the pointer). Some mice have a third buttonand/or a small wheel that can be used to scroll the display,but only certain software recognizes these functions.Further ReadingBrain, Marshall, and Carmen Carmack. “How Computer MiceWork.” Available online. URL: http://computer.howstuffworks.com/mouse.htm. Accessed August 15, 2007.Pang, Alex Soojung-Kim. “The Making of the Mouse.” AmericanHeritage. Available online. URL: http://www.americanheritage.com/articles/magazine/it/2002/3/2002_3_48.shtml. AccessedAugust 15, 2007.MS-DOSThe MS-DOS operating system became standard for personalcomputers built by IBM and its imitators (see IBMPC) during the 1980s. Today it has been virtually displacedby various versions of Microsoft Windows (see MicrosoftWindows). However, MS-DOS is important as an expressionof both the limitations of the first generation of personalcomputers and the remarkable patience and ingenuityof its developers and users.DevelopmentBy the end of the 1970s, there were a number of rudimentaryoperating systems for personal computers that useda variety of microprocessors. Generally, their capabilitieswere limited to loading and running programs and providingbasic file organization and access.The most sophisticated early PC operating systemwas CP/M, developed by Gary Kildall’s Digital Researchfor machines based on the Intel 8008 microprocessor. CP/M offered more advanced capabilities such as the abilityto use not only floppy but also hard disks, and includedimproved commands for listing file directories. CP/M evenoffered rudimentary programming tools, such as an editorand assembler, as well as an expandable architecture thatallowed programmers to write utilities that could be ineffect added to the operating system (see assembler).In one of computer history’s greatest missed opportunities,Kildall and IBM failed to come to an agreement in1980 for creating a version of CP/M for the IBM PC, whichwas being developed using the new 16-bit 8086 processor.IBM turned instead to Bill Gates and Microsoft, whohad achieved something of a reputation for their widelyused BASIC language package for personal computers (seeGates, William). Gates agreed to provide IBM with anoperating system, and did so by buying a program calledQDOS (“quick and dirty operating system”), which hadbeen developed by Tim Paterson of Seattle Computer Products.This program was released for the IBM PC as PC-DOSin 1981. However, Microsoft did not sell IBM an exclusivelicense, so when “clone” makers proved able to legally buildIBM-compatible machines, Microsoft could sell them ageneric version called MS-DOS. As the PC market boomed,this provided Microsoft with a large revenue stream, andthe company never looked back.FeaturesMS-DOS offered a rather “clean” design that separates theoperating system into three parts. There is a hardwareindependentI/O system (stored as the file MSDOS.SYS),which processes requests from programs for access to diskfiles or to other devices such as the screen. The routinesneeded to actually communicate with the devices are storedin a separate file, IO.SYS, which is written by each computermanufacturer. (As users from the early 1980s remember,“PC-compatible” machines often had proprietary variationsin areas such as video.) Finally, the command processor(COmmAND.COM) displays the once familiar C:\> promptand waits for the user to type commands. For example,the DIR command followed by a path specification such asC:\TEMP lists the contents of that directory. Programs, too,can be run by typing their names at the prompt.The MS-DOS file system, which remained largelyunchanged until the most recent versions of Windows, usesa FAT (file allocation table) to indicate the disk allocationunits or “clusters” assigned to each file. Starting with MS-DOS 2.0 in 1983, a hierarchical scheme of directories andsubdirectories was introduced, allowing for better organizationof the larger amount of space on hard disks.One interesting feature of MS-DOS is the ability to loada program into memory and keep it available even whileother programs are in use. This “terminate and stay resident”(TSR) function was soon used by enterprising developersto provide utilities such as notepads, calendars orshortcuts (see macro) that users could activate throughspecial key combinations.Users, however, had to struggle to keep enough memoryfree for their applications, resident programs, and devicedrivers. A combination of CPU addressing limitations andthe high price of memory meant that early IBM PCs had

322 multimediaa maximum of 640 kB of memory to hold the operatingsystem and application programs. A trick called “expandedmemory” was developed to allow data to be swapped backand forth between the 640 kB of usable memory and the1–2 MB of additional memory that became available in thelater 1980s.By the early 1990s, MS-DOS (then up to version 6.0) wasoffering an alternative command processor (called DOS-SHELL) that included some mouse operations, better supportfor larger amounts of memory, and the ability to switchbetween different application programs. However, by thattime Windows 3.0 was proving increasingly successful, andby 1995 most new PCs were being shipped with Windows.Many new users scarcely used MS-DOS at all. Finally, withthe advent of Windows NT, 2000, and XP, the MS-DOS programcode that still lurked within the process of runningWindows disappeared entirely.Further Reading“Information and Help with Microsoft DOS.” Available online.URL: http://www.computerhope.com/msdos.htm. AccessedAugust 15, 2007.Paterson, Tim. “An Inside Look at MS-DOS.” Byte, vol. 8, no.6, June 1983, 250–252. Available online. URL: http://www.patersontech.com/Dos/Byte/InsideDos.htm. Accessed February6, 2008.multimediaThe earliest computers produced only numeric output ortext (which itself actually consists of numbers—see charactersand strings). During the 1960s, CRT graphics (seemonitor) came into limited use, mainly on computers usedfor scientific and engineering applications (see minicomputer).However, most business computer users continuedto receive only textual output. A notable exception in the1970s was PLATO, a system of networked educational computerterminals that combined text, graphics, and sound. Itis this combination that became known as multimedia.While much less powerful than mainframes or minicomputers,the hobbyist and early commercial PCs (seegraphics card) of the late 1970s generally did have thecapability of producing simple monochrome or color graphicson a monitor or TV screen. The Apple Macintosh, firstreleased in 1984, was a considerable leap forward: Its userinterface was inherently graphical, with even text beingrendered as graphic bitmaps (see Macintosh).The arrival of the PC greatly encouraged the developmentof entertainment software (see computer games) aswell as educational programs. As PCs became more powerfuland gained hard drives and, by the late 1980s, CD-ROMdrives (see CD-Rom), it became practical to put extensivemultimedia content on systems in the home and school.One popular application has been encyclopedias, where thetext from the printed version can be enhanced with graphicssuch as photographs, maps, and charts. Besides beingmore compelling and easier to use than the printed version,multimedia encyclopedias can be updated easily throughannual upgrades, as well as allowing for linking to Websites that can further amplify or update the content.Encyclopedias and other educational programs alsobenefited from the use of links that the user can click withthe mouse, bringing up additional or related information orillustrations (see hypertext and hypermedia). Bill Atkinson’sHypercard, released for the Macintosh in 1987, provideda multimedia “construction set” that could be usedby nonprogrammers to create simple hyperlinked presentations,educational programs, and even games. Hypertextand linking are the “glue” that binds multimedia into anintegrated experience.Multimedia business presentations are now routinelycreated using software such as Microsoft PowerPoint, thenprojected at meetings. While simple presentations can emulatethe traditional “slide show,” one-upmanship inevitablyleads to more elaborate animations.Multimedia and Daily LifeDVD-ROM drives, with about six times the storage capacityof CDs, now make it practical to include video or evenfeature-length movies as part of a PC multimedia package.Meanwhile, the video capabilities of PCs continue to grow,with many PCs as of 2008 having 256 MB or more of videomemory. Combined with processors running at up to 2.5GHz, this allows computer-generated graphics to rival thequality of live video.However, the most important trend is probably thedelivery of online multimedia content (see Internet,online services, and World Wide Web). The widespreadmarketing of the Mosaic and Netscape browsers (see Webbrowser) in the mid-1990s changed the Internet from anarcane, text-driven experience to a multimedia platform.The ability to deliver a continuous “feed” of video and audio(see music and video distribution, online and streaming)allows content such as TV news reports to be carriedwith full video and radio broadcasts carried “live” withgood fidelity. Newspapers and broadcast outlets are increasinglyinvesting in online versions of their content, viewinga Web presence as a business necessity. As more Internetusers gain access to high-speed cable and DSL services (seebroadband), multimedia is becoming as pervasive a part ofthe computing experience as television is in daily life.Many facets of that daily life are likely to be affectedby multimedia technology in coming years. The ability todeliver real-time, high-quality multimedia content, as wellas the use of cameras (see videoconferencing and Webcam) has made “virtual” meetings not only possible butalso routine in some corporate settings. When applied tolectures, this technology can facilitate “distance learning”where teachers work with students without them occupyingthe same room (see distance education and educationand computers). Video “chat” services and immersive,pervasive online games have become important social outletsfor many people, with the experience becoming evermore realistic (see online games and virtual reality).Already, the concept of multimedia is becoming lessdistinctive precisely because it is so pervasive. Today’s Webusers expect to see images, video, and sound, whether aspart of a news story or an educational presentation, andmultimedia is appearing on all sorts of new platforms (see

multiprocessing 323music and video players, digital; smartphones; and digitalconvergence). Further, equipped with digital camerasand camcorders (even cell-phone cameras), togetherwith easy-to-use editing software, more and more peopleare becoming not just consumers of multimedia, but creatorsas well (see user-created content and YouTube).Further ReadingCoorough, Calleen, and James E. Shuman. Multimedia for the Web:Creating Digital Excitement. Boston: Thomson Course Technology,2005.Lauer, David, and Stephen Pentak. Design Basics: Multimedia Edition.6th ed. Belmont, Calif.: Wadsworth Publishing, 2006.MIT Media Lab. Available online. URL: http://www.media.mit.edu.Accessed August 15, 2007.“Multimedia and Authoring Resources on the Internet.” NorthwesternUniversity Library. Available online. URL: http://www.library.northwestern.edu/dms/multimedia.html.Accessed August 15, 2007.Packer, Randall, and Ken Jordan. Multimedia: From Wagner to VirtualReality. Expanded ed. New York: Norton, 2002.Vaughan, Tay. Multimedia: Making It Work. 7th ed. New York:McGraw-Hill/Osborne Media, 2006.multiprocessingOne way to increase the power of a computer is to use morethan one processing unit. In early computers (see mainframe)a single processor handled both program executionand input/output (I/O) operations. In the late 1950s,however, machines such as the IBM 709 introduced theconcept of channels, or separate processing units for I/Ooperations. In such systems the central processor sends aset of I/O commands (such as to read a file into memory) tothe channel, which has its own processor for carrying outthe operation.True multiprocessing, however, involves the use of morethan one central processing unit (CPU). One successfuldesign, Control Data Corporation’s CDC 6600 (1964), containedboth multiple arithmetic/logic units (the part of theCPU that does calculations) and multiple controllers for I/Oand memory access control. IBM soon added multiprocessingcapability to its 360 line of mainframes.Multiprocessing can be either asymmetric or symmetric.Asymmetric multiprocessing essentially maintains a singlemain flow of execution with certain tasks being “handedover” by the CPU to auxiliary processors. (For example,the Intel 80386 processor could be purchased with an additionalfloating-point processor, allowing such calculationsto be performed using more efficient hardware. When thePentium line was developed, floating-point was integratedinto the main CPU).Symmetric multiprocessing (SMP) has multiple, fullfledgedCPUs, each capable of the full range of operations.The processors share the same memory space, whichrequires that each processor that accesses a given memorylocation be able to retrieve the same value. This coherenceof memory is threatened if one processor is in the midstof a memory access while another is trying to write datato that same memory location. This is usually handled bya “locking” mechanism (see concurrent programming)that prevents two processors from simultaneously accessingthe same location.A subtler problem occurs with the use by processors ofseparate internal memory for storing data that is likely tobe needed (see cache). Suppose CPU “A” reads some datafrom memory and stores it in its cache. A moment later,CPU “B” writes to that memory location, changing the data.At this point the data in “A’s” cache no longer matches thatin the actual memory. One way to deal with this problemis called bus snooping. Each CPU includes a controller thatmonitors the data line (see bus) for memory locations beingused by other CPUs. When it sees an address that refers toan area of memory currently being stored in the cache, thecontroller updates the memory from the cache. This writeoperation sends a signal that lets other CPUs know that anycached data they have for that location is no longer valid.This means the other CPUs will go back to memory andreread the current data.Alternatively, all CPUs can be given a single sharedcache. While less complicated, this approach limits thenumber of CPUs to the maximum data-handling capacityof the bus.Larger-scale multiprocessing systems consist of latticelikearrays of hundreds or even thousands of CPUs,which are referred to as nodes. Indeed, small clusters ofCPUs using the architecture given above can be connectedtogether to form larger arrays. Each cluster can have itsown shared memory cache. Because accessing memory ata remote node takes considerably longer than accessingThis example shows what can happen if processes do not properlymanage a shared memory resource. At (1) processor A retrieves3 from the memory location. At (2) processor B copies 7 from itscache to that same memory location. Finally, at (3) processor Aadds the 3 it had retrieved to a 2 in its register, storing 5 back in alocation where processor B probably expects there to still be a 7.

324 multitasking“local” memory within the cluster, maintaining coherencethrough bus monitoring is impracticable. Instead, memoryis usually organized into data objects that are distributedoptimally to reduce the necessity for remote access, andthe objects are shared by CPUs requesting them through adirectory system.MultiprogrammingIn order for a program to take advantage of the ability to runon multiple CPUs, the operating system must have facilitiesto support multiprocessing, and the program must be structuredso its various tasks are most efficiently distributedamong the CPUs. These separate tasks are generally calledthreads. A single program can have many threads, eachexecuting separately, perhaps on a different CPU, althoughthat is not required.The operating system can use a number of approachesto scheduling the execution of processes or threads. It cansimply assign the next idle (available) CPU to the thread.It can also give some threads higher priority for access toCPUs, or let a thread continue to “own” its CPU until it hasbeen idle for some specified time.The use of threads is particularly natural for applicationswhere a number of activities must be carried onsimultaneously. For example, a scientific or process controlapplication may have a separate thread reading the databeing returned from each instrument, another thread monitoringfor alarm conditions, and other threads generatinggraphical output.Threads also allow the user to continue interacting witha program while the program is busy carrying out earlierrequests. For example, the user of a Web browser can continueto use menus or navigation buttons while the browseris still loading graphics needed for the currently displayedWeb page. A search program can also launch separatethreads to send requests to multiple search engines or toload multiple pages.Support for multiprogramming and threads can now befound in versions of most popular programming languages,and some languages such as Java are explicitly designed toaccommodate it.Multiprogramming often uses groups or clusters of separatemachines linked by a network. Running software onsuch systems involves the use of communications protocolssuch as the MPI (message-passing interface). This programminginterface has been widely deployed on many platformsfor use with languages such as C/C++ and Fortran.Another popular programming interface is OpenMP, whichfeatures the allocation of execution threads and the distributionof work among them.A Multiprocessed WorldThe demand for software that can efficiently use multipleprocessors is likely for some time to outstrip the supply ofprogrammers who can “think in parallel.” One reason isthat today most new PCs have two processing “cores,” withfour-core systems available and more to come (see microprocessor).This means that many mainstream applicationswill eventually need to be rewritten for the newhardware environment. Another factor is that as the priceper processor continues to decline and high-end multiprocessingmachines are reaching 1 “petaflop” (1 quadrillionoperations per second), many supercomputer applicationswill also need to be rewritten.Meeting this demand not only takes training, it alsotakes appropriate languages and other tools. In recentyears, therefore, the Defense Advanced Research ProjectsAgency (DARPA) has funded research in “High ProductivityComputer Systems” by such companies as Cray, Sun,and IBM. New languages built “from the ground up” formultiprocessing include Sun’s Fortress, Cray’s Chapel, andIBM’s new project, code-named X10. Ultimately, systemsfor developing multiprocessing software should take mostof the architectural details off the hands of the programmer,allowing performance to smoothly “scale up” with theincreasing number of processors.Further ReadingAnthes, Gary. “Languages for Supercomputing Get ‘Suped’ Up.”Computerworld, March 12, 2007. Available online. URL:http://www.computerworld.com/action/article.do?command=viewArticleBasic&articleId=283477. Accessed April 5, 2007.Culler, David E., and Jaswinder Pal Singh. Parallel Computer Architecture:A Hardware/Software Approach. San Francisco: MorganKaufmann, 1999.Dongara, Jack, et al., eds. Sourcebook of Parallel Computing. SanFrancisco: Morgan Kaufmann, 2003.Feldman, Michael. “Our Manycore Future.” HPC Wire. Availableonline. URL: http://www.hpcwire.com/hpc/1295541.html.Accessed April 5, 2007.Merritt, Rick. “Where Are the Programmers? Enrollment WanesJust as Computer Scientists Grapple with Problem of Parallelism.”EE Times, March 12, 2007. Available online. URL:http://www.eetimes.com/showArticle.jhtml?articleID=197801653. Accessed April 5, 2007.Quinn, Michael J. Parallel Programming in C with MPI and OpenMP.New York: McGraw-Hill, 2003.multitaskingUsers of modern operating systems such as Microsoft Windowsare familiar with multitasking, or running severalprograms at the same time. For example, a user might bewriting a document in a word processor, pause to check thee-mail program for incoming messages, type a page addressinto a Web browser, then return to writing. Meanwhile, theoperating system may be running a number of other programstucked unobtrusively into the background, such as avirus checker, task scheduler, or system resource monitor.Each running program “takes turns” using the PC’s centralprocessor. In early versions of Windows, multitaskingwas cooperative, with each program expected to periodicallyyield the processor to Windows so it could be assigned to thenext program in the queue. One weakness of this approachis that if a program crashes, the CPU might be “locked up”and the system would have to be rebooted. However, WindowsNT, 2000, and XP (as well as operating systems suchas UNIX) use preemptive multitasking. The operating systemassigns a “slice” of processing (CPU) time to a programand then switches it to the next program regardless of what

music, computer 325program’s priority would ordinarily entitle it to a greatershare of the CPU.Multitasking should be distinguished from two severalsimilar-sounding terms. Multitasking refers to entirely separateprograms taking turns executing on a single CPU.Multithreading, on the other hand, refers to separate piecesof code within a program executing simultaneously butsharing the program’s common memory space. Finally, multiprocessingor parallel processing refers to the use of morethan one CPU in a system, with each program or threadhaving its own CPU (see multiprocessing).Further ReadingSilberschatz, Abraham, Peter Baer Galvin, and Greg Gagne. OperatingSystem Concepts. 7th ed. New York: Wiley, 2004.Tanenbaum, Andrew S., and Albert S. Woodhull. Operating SystemsDesign and Implementation. 3rd ed. Upper Saddle River,N.J.: Prentice Hall, 2006.Windows users can bring up a window listing all processes or tasksrunning on the system, and shut down any task that has stoppedresponding to input.might be happening to the previous program. Thus, if a program“crashes,” the CPU will still be switched to the nextprogram, and the user can maintain control of the systemand shut down the offending program.Systems with preemptive multitasking often give programsor tasks different levels of priority that determinehow big a slice of CPU time they will get. For example, the“active” program (in Windows, the one whose window hasbeen selected for interaction by the user) will be given preferenceover a background program such as a print spooler.Also, the operating system can more intelligently assignCPU time according to what a given program is doing.Thus, if a program is waiting for user input, it may be givenonly an occasional slice of CPU time so it can check to seewhether input has been received. (The user, after all, ismillions of times slower than the CPU.) When some input(such as a menu selection) is ready for processing, the programcan be given higher priority.Priority can be expressed in two different ways. Oneway is to move a program up in the list of running tasks (seequeue). This ensures it gets a turn before any lower-prioritytask. The other way is to have turns of varying length, withthe higher-priority program getting a longer turn.Even operating systems with preemptive multitaskingcan provide facilities that programs can use to communicatetheir own sense of their priority. In UNIX systems,this is referred to as “niceness.” A “nice” program givesthe operating system permission to interrupt lengthy calculationsso other programs can have a turn, even if themusic, computerComputers have had a variety of effects on the performance,rendering, and composition of music. At the same time,the sound capabilities of standard personal computers haveimproved greatly, and music and other sounds have becomean integral part of games and educational software (seemultimedia).After the invention of the vacuum tube, a number of electronicinstruments were devised. The best known is the theremin,invented by Lev Termin, a Russian physicist, in 1919.The instrument consists of a vacuum tube connected to twoantennas. The player varies the pitch and volume of its eeriesound by moving his or her hands near the antennas.Some composers became fascinated by electronic music,both for its sense of modernity and its promise of breakingthe bonds of traditional form and instrumentation. In 1953,German composer Karlheinz Stockhausen (1928–2007)founded an Electronic Music Studio in Cologne and createdelectronic works.Meanwhile, inventors experimented with electronic synthesizerssuch as the RCA MKI and MKII, which used vacuumtubes and could be programmed with punched papertape. The advent of solid-state circuitry in the 1960s madesynthesizers far more reliable and compact. The Moog synthesizerin particular became a staple of leading-edge rockand avant-garde music. It was now time for the computer tocatch up to the potential of electronic sound.In the 1970s, digital music synthesizers with keyboardsand microprocessor-controlled sound generation becameavailable to adventurous (and fairly well-to-do) musicians.Ray Kurzweil’s digital music synthesis system, introducedin 1984, achieved a new level of sonic realism by usingprogramming stored in read-only memory (ROM) to emulatesubtle characteristics such as attack and timbre, realisticallyre-creating the sounds of many types of orchestralinstruments.Computer music synthesis enabled composers to experimentwith algorithmic composition. That is, they could useprograms to create new works by combining randomizationwith the permutation of patterns (serialism). Compositions

326 music and video distribution, onlinehave also been based on applying mathematical structures(such as fractals) and the concepts being discovered bycomputer scientists, including adaptive structures such asneural nets and genetic algorithms.Like most avant-garde music, computer music compositionremained largely unknown to most people. However,the technology of music synthesis was to become democraticallyavailable to everyday musicians as well. As thepersonal computer began to bring increasingly powerfulmicroprocessors to consumers, it became practicable toin effect add a music synthesizer to the PC. The musicalinstrument digital interface, MIDI, provides a protocol forconnecting traditional musical instruments such as pianosand guitars to a personal computer. MIDI specifies the pitch,volume, attack (how a note increases to maximum volume),and decay (how it dies away). The musician then uses theinstrument as an input device, with the notes played beingrecorded as MIDI data. Different tracks can then be edited(such as to transpose to a different key), and combinedin various ways to create complete compositions. BecauseMIDI stores instructions, not actual digitized sound, it is aquite compact way to store music. MIDI brought the synthesizerwithin reach of just about any serious musician—andmany amateurs.PC sound cards can play sound in two ways. Wave TableSynthesis uses a table of stored digital samples of notesplayed by various instruments, and algorithmically manipulatesthem to reproduce the MIDI-encoded music. FM Synthesisattempts to create waves that replicate the intendedsounds, based on a model of what happens in a given instrument.It is less faithful to the original sound, since it doesnot capture the detailed “texture” of a digital sample.Today’s PCs have sound cards that can handle bothplayback of audio CDs and rendering of digitized and synthesizedsounds. The cards have the capacity to supportmany simultaneous voices (polyphony) as well as renderingspeech faithfully. While early PCs tended to have onlytiny internal speakers, most PCs today come with speakers(often including subwoofers and even multiple speakers for“surround sound”) comparable to midrange home stereosystems.Of course great hardware would not be very useful withoutsoftware that can help even beginning composers turntheir ideas into sound. One example is GarageBand for theMacintosh, which makes it easy to make compositions fromsampled and sequenced loops together with music playedusing sampled and synthesized instrument sounds and aMIDI keyboard. (Sony ACID Pro offers similar features forMicrosoft Windows users.)Further ReadingBurns, Kristine H. “History of Electronic and Computer MusicIncluding Automatic Instruments and Composition Machines.”Available online. URL: http://eamusic.dartmouth.edu/~wowem/electronmedia/music/eamhistory.html. Accessed August 15,2007.Freebyte Music Zone. Available online. URL: http://www.freebyte.com/music/. Accessed August 15, 2007.Manning, Peter. Electronic and Computer Music. New York: OxfordUniversity Press, 2004.Nelson, Mark. Getting Started in Computer Music. Boston: ThomsonCourse Technology, 2005.White, Paul. Basic MIDI. London: Sanctuary, 2004.Williams, Ryan. Windows XP Digital Music for Dummies. Hoboken,N.J.: Wiley, 2004.music and video distribution, onlineSince most audio and much video is now recorded in digitalformat, the Internet and media-player software for a varietyof platforms are an attractive way to sell or otherwise distributethe products of musicians and moviemakers.For a time, online file swapping (see file-sharing andp2p networks), particularly Napster, seemed to be massivelyeroding the market for online commercial musicsales. Legal action against file-sharing services and (startingin 2003) their users has curtailed this erosion somewhat,with a considerable number of former file-sharers switchingto buying paid downloads. As a result, several major onlinemusic stores have become successful. The most commonmodel sells songs for about a dollar each—sometimes morefor higher quality audio or files that do not have copy protection(see digital rights management).Apple’s iTunes Music store debuted in 2003 and soonbecame the market leader. The combination of the iTunesstore, the iTunes media player software (available for bothMacintosh and PC), and the very popular iPod (see musicand video players, digital) has been very successful. Asof 2007 iTunes still had the largest selection of music available(about 6 million songs), and had sold more than 3billion songs. The service also sells videos (television episodes,music videos, short films, and feature-length movies)at varying prices.Rhapsody, a service that predates iTunes, offers a subscriptionmodel: The user has unlimited streaming accessto the music as long as the monthly fee is paid as well as thepay-per-track option.Alternative ModelsThere are also alternatives to the big, label-controlledmusic services. A number of services now bring togetherindependent musicians and their audience. There are alsosome innovative pricing models. Arnie Street, for example,starts out with uploaded music being available free, butthen gradually raises the price (up to 98 cents) as morepeople download it. The service also offers user participation(keyword tagging by users) and social-networking features.Another service, eListeningPost, lets musicians postmusic that people can download as a preview (playable alimited number of times) or buy using PayPal. The servicealso helps musicians build their fan base by collecting e-mail addresses.VideoVideo-sharing sites are very popular (see YouTube). TVnetworks are now providing selected episodes of popularshows online for free, hoping to entice more regularviewers. However, only 7 percent of users surveyed by thePew Internet & American Life Project in 2007 said they

music and video players, digital 327had paid for any online video content. This may graduallychange, particularly as more users move from basicbroadband connections to enhanced, higher-speed ones(see broadband). Already video sales through iTunes andAmazon’s new Unbox (and smaller services) are expectedby Forrester Research to generate $279 million in revenuefor 2007. However, some analysts believe that the businessmodel for selling video will soon shift to something morelike that of premium cable channels, with streaming videoavailable by subscription.Further ReadingArnie Street. Available online. URL: http://amiestreet.com/.Accessed October 3, 2007.Bove, Tony, and Cheryl Rhodes. iPod & iTunes for Dummies. 5thed. Hoboken, N.J.: Wiley, 2007.eListeningPost. Available online. URL: http://elisteningpost.com/.Accessed October 3, 2007.iTunes. Available online. URL: http://www.apple.com/itunes/store.Accessed October 3, 2007.Madden, Mary. “Artists, Musicians, and the Internet.” Pew Internet& American Life Project, December 5, 2004. Availableonline. URL: http://www.pewinternet.org/pdfs/PIP_Artists.Musicians_Report.pdf. Accessed October 3, 2007.———. “Online Video.” Pew Internet & American Life Project,July 25, 2007. Available online. URL: http://www.pewinternet.org/pdfs/PIP_Online_Video_2007.pdf.Accessed October3, 2007Madden, Mary, and Lee Rainie. “Music and Video DownloadingMoves beyond P2P.” Pew Internet & American Life Project,March 2005. Available online. URL: http://www.pewinternet.org/pdfs/PIP_Filesharing_March05.pdf. Accessed October 3,2007.Muchmore, Michael. “New Ways to Get Music.” ExtremeTech.,December 10, 2006. Available online. URL: http://www.extremetech.com/article2/0,1697,2070636,00.asp. AccessedOctober 3, 2007.Rhapsody. Available online. URL: http://www.rhapsody.com/home.html. Accessed October 3, 2007.• creates a music library that can be searched or reorganized• can create playlists and queues and can play backsongs in order, shuffled (randomized), or according toother preferences• can obtain additional information about media(tracks, albums, and so on) onlinePortable PlayersFirst unveiled in 2001, the Apple iPod is the best-sellingexample of a portable media player (often called a “digitalaudio player”). Its compact, stylish design and simple userinterface quickly caught on, even though the first model wasonly compatible with the Macintosh and it used Apple’s AACformat rather than MP3. Later iPods added capacity, largerscreens, and features (such as being able to play video), whileApple also offered the inexpensive iPod Shuffle. A competitoris the Microsoft Zune player and music store, which, however,as of mid-2007 had made little headway against marketleader Apple. A third well-reviewed choice is the CreativeLabs Zen series. A variety of other portable players are available.Higher capacity units use tiny hard drives (up to 160 GBcapacity or so), while smaller capacity models use flash memory(2–32 GB) instead. A variety of other handheld devicescan play music and video (see PDA and smartphone).With the ubiquitous use of iPods and other players,particularly by young people, some health and safety concernshave been raised. If played too loudly for long periodsof time through headphones or earbuds, the devices maycause hearing damage. Drivers and pedestrians may also bemusic and video players, digitalOne characteristic of the rapidly evolving digital worldis the ability to play a variety of media (music, photos,video) on many devices, ranging from desktop PCs to smartphones and, of course, iPods and MP3 players (see digitalconvergence). The ability to organize and play mediarequires suitable software and hardware.On desktop and laptop PCs, media-playing software isavailable for all operating systems. Examples include WindowsMedia Player, Apple iTunes, and RealPlayer (whichalso has a Linux version). This software typically includesthese features:• plays most types of media files (see graphics formatsand sound file formats)• plays content on CD/DVD, files on the hard drive, orcontent being received directly from the Internet (seeCD-Rom and DVD-ROM; music and video distribution,online; and streaming)• controls are modeled on those found on DVD players,with customizable appearanceThe Apple iPod is the most popular portable digital media player,featuring a simple, effective interface and the ability to play musicand show video. (Apple Corporation)

328 music and video players, digitalat greater risk if the music they are listening to cuts off thesound of approaching vehicles.Further ReadingJohnson, Brian. Zune for Dummies. Hoboken, N.J.: Wiley, 2007.Kelby, Scott. The iPod Book: Doing Cool Stuff with the iPod and theiTunes Store. 3rd. ed. Berkeley, Calif.: Peachpit Press, 2006.MP3 Players (CNet Reviews). Available online. URL: http://reviews.cnet.com/Music/2001-6450_7-0.html. Accessed October 3,2007.“MP3 Players: The Basics and History.” Available online. URL:http://www.mp3playerlimelight.com/. Accessed October 3,2007.Rathbone, Andy. MP3 for Dummies. New York: Hungry Minds,2001.

NnanotechnologyOrdinary refining and manufacturing involve the use ofgrinding, cutting, heating, application of chemicals, and otherprocesses that affect large numbers of atoms or molecules atonce. These processes are necessarily imprecise: Some atomsor molecules will end up unprocessed or somehow out ofalignment. The resulting material will thus fall short of itsmaximum theoretical strength or other characteristics.In a talk given in 1959, physicist Richard Feynman suggestedthat it might be possible to manipulate atoms individually,spacing them precisely. As Feynman also pointedout, the implications for computer technology are potentiallyvery impressive. A current commercial DIMM memorymodule about the size of a person’s little finger holdsabout 250 megabytes (MB) worth of data. Feynman calculatedthat if 100 precisely arranged atoms were used foreach bit of information, the contents of all the books thathave ever been written (about 10 15 bits) could be stored ina cube about 1/200 of an inch wide, just about the smallestobject the unaided human eye can see. Further, althoughthe density of computer logic circuits in microprocessors ismillions of times greater than it was with the computers of1959, computers built at the atomic scale would be billionsof times smaller still. Indeed, they would be the smallest (ordensest) computers possible short of one that used quantumstates within the atoms themselves to store information(see quantum computing). “Nanocomputers” could alsoefficiently dissipate heat energy, overcoming a key problemwith today’s increasingly dense microprocessors.Feynman offered some possible methods of manufacture,and discussed some of the obstacles that would have to beovercome to do engineering at a molecular or atomic scale.These include lubrication, the effects of heat, and electricalresistance. He invited adventurous high school students todevelop science projects to explore this new technology.The idea of atomic-level engineering lay largely dormantfor about two decades. Starting with a 1981 paper, however,K. Eric Drexler began to flesh out proposed structures andmethods for a branch of engineering he termed nanotechnology.(The “nano” refers to a nanometer, or one billionthof a meter.) Research in nanotechnology today focuseson two broad areas: assembly and replication. Assemblyis the problem of building tools (called assemblers) thatcan deposit and position individual atoms. Since such toolswould almost certainly be prohibitively expensive to manufactureindividually, research has focused on the idea ofmaking tools that can reproduce themselves. This area ofresearch began with John von Neumann’s 1940s concept ofself-replicating computers (see von Neumann, John). If anassembler can assemble other assemblers from the available“feedstock” of atoms, then obtaining the number of assemblersnecessary to manufacture the intended product wouldbe no problem. (As science fiction writers have pointed out,the ultimate problem would be making sure the self-reproducingassemblers do not get out of control and start turningeverything around them, potentially the whole Earth,into more of themselves.)Computing ApplicationsScience fiction aside, there are several potential applicationsof nanotechnology in the manufacture of computercomponents. One is the possible use of carbon nanotubes in329

330 natural language processingplace of copper wires as conductors in computer chips. Aschips continue to shrink, the connectors have also had toget smaller, but this in turn increases electrical resistanceand reduces efficiency. Nanotubes, however, are not onlysuperb electrical conductors, they are also far thinner thantheir copper counterparts. Intel Corporation has conductedpromising tests of nanotube conductors, but it will likely bea number of years before they can be manufactured on anindustrial scale.An obstacle to manufacturing carbon nanotubes is thateach newly made batch is a mixture of “metallic” (conducting)and semiconducting tubes of different diameters.Manufacturing, however, requires tubes that meet strictrequirements. Fortunately researchers at NorthwesternUniversity in 2006 developed a way to sort the tubes byadding substances that changed their density according toboth their diameter and their electrical conductivity.Another alternative is “nanowires.” One design consistsof a germanium core surrounded by a thin layer of crystallinesilicon. Nanowires are easier to manufacture thannanotubes, but their performance and other characteristicsmay make them less useful for general-purpose computingdevices.The ultimate goal is to make the actual transistors incomputer chips out of nanotubes instead of silicon. Animportant step in this direction was achieved in 2006 byIBM researchers who created a complete electronic circuitusing a single carbon nanotube molecule.Further ReadingBooker, Richard D. and Earl Boysen. Nanotechnology for Dummies.Hoboken, N.J.: Wiley, 2005.Bullis, Kevin. “Nanotube Computing Breakthrough: A Method forSorting Nanotubes by Electronic Properties Could Help MakeWidespread Nanotube-Based Electronics a Reality.” TechnologyReview, October 30, 2006. Available online. URL: http://www.technologyreview.com/Nanotech/17672/. Accessed August 16,2007.———. “Nanowire Transistors Faster than Silicon.” TechnologyReview, June 20, 2006. Available online. URL: http://www.technologyreview.com/Nanotech/17008/. Accessed August16, 2007.Edwards, Steven A. The Nanotech Pioneers: Where Are They TakingUs? New York: Wiley, 2006.Kanellos, Michael. “Intel Eyes Nanotubes for Future Chip Designs.”CNET News, November 10, 2006. Available online. URL: http://news.com.com/2100-1008_3-6134437.html. Accessed August16, 2007.Korkin, Anatoli, et al., eds. Nanotechnology for Electronic Materialsand Devices. New York: Springer, 2007.Nanotech Web. Available online. URL: http://nanotechweb.org/.Accessed August 16, 2007.natural language processingSince at least the days of Hal 9000 and early Star Trek, thecomputer of the future was supposed to be able to understandwhat people wanted, when expressed in ordinary languageand not programming code. Computer scientists havebeen working on this capability, called natural languageprocessing (NLP), for decades.NLP is a multidisciplinary field that draws from linguisticsand computer science, particularly artificial intelligence(see also linguistics and computing and speech recognitionand synthesis). In terms of linguistics, a programmust be able to deal with words that have multiple meanings(“wind up the clock” and “the wind is cold today”) aswell as grammatical ambiguities (in the phrase “little girl’sschool” is it the school that is little, the girls, or both?). Ofcourse each language has its own forms of ambiguity.Programs can use several strategies for dealing withthese problems, including using statistical models to predictthe likely meaning of a given phrase based on a “corpus” ofexisting text in that language (see language translationsoftware).As formidable as the task of extracting the correct (literal)meaning from text can be, it is really only the first levelof natural language processing. If a program is to successfullysummarize or draw conclusions about a news reportfrom North Korea, for example, it would also have to havea knowledge base of facts about that country and/or a set of“frames” (see Minsky, Marvin) about how to interpret varioussituations such as threat, bluff, or compromise.)ApplicationsThere are a variety of emerging applications for NLP, includingthe following:• voice-controlled computer interfaces (such as in aircraftcockpits)• programs that can assist with planning or other tasks(see software agents)• more-realistic interactions with computer-controlledgame characters• robots that interact with humans in various settingssuch as hospitals• automatic analysis or summarization of news storiesand other text• intelligence and surveillance applications (analysis ofcommunication, etc.)• data mining, creating consumer profiles, and other e-commerce applications• search-engine improvements, such as in determiningrelevancyFurther ReadingJackson, Peter, and Isabelle Moulinier. Natural Language Processingfor Online Applications: Text Retrieval, Extraction and Categorization.2nd ed. Philadelphia: John Benjamins, 2007.Kao, Anne, and Steve R. Poteet, eds. Natural Language Processingand Text Mining. New York: Springer, 2007.Manning, Christopher D., and Hinrich Schütze. Foundations ofStatistical Natural Language Processing. Cambridge, Mass.:MIT Press, 1999. Available online. URL: http://www-nlp.stanford.edu/fsnlp/. Accessed October 4, 2007.Natural Language Toolkit. Available online. URL: http://nltk.sourceforge.net/index.php/Main_Page. Accessed October 4,2007.

netiquette 331Resources for Text, Speech and Language Processing. Availableonline. URL: http://www.cs.technion.ac.il/~gabr/resources/resources.html. Accessed October 4, 2007.Negroponte, Nicholas(1944– )AmericanComputer ScientistAs founder and longtime director of the MIT Media Lab,Nicholas Negroponte has overseen and contributed to someof the most creative developments in human-computerinteraction and interface design.Born in 1943, the son of a Greek shipping magnate,Negroponte grew up in New York City. He attended theMassachusetts Institute of Technology (MIT), earning hismaster’s degree in architecture in 1966 and joining thefaculty. The following year Negroponte founded the MITArchitecture Machine Group, which focused on developingnew ways for people to interact with computers. In 1985,Negroponte and Jerome Wiesner founded the MIT MediaLab, which has become world famous as a center of researchinto new media and innovative computer interfaces (seemit Media Lab).Negroponte made a different contribution to the newcomputer culture in 1992 when he became a key investor inWired Magazine, where he also contributed a column until1998. Many of the ideas in these columns were reworkedinto Negroponte’s 1995 book Being Digital. This book waswidely influential in its predictions of a coming world whereinformation and entertainment would become a pervasiveweb and people would interact actively with the new media(see digital convergence and ubiquitous computing).Negroponte’s slogan is “move bits, not atoms,” meaning thatthe new economy will be focused more on information andmedia than physical production. Some critics, however,have argued that Negroponte’s work was filled with a naiveutopianism that did not consider the potential difficultiesand social consequences of the new technology.As Negroponte observed how venture capitalists werepursuing the digital revolution of the 1990s, he began toseek similar funding for the Media Lab. This was controversial,since the lab had a strong academic culture, with itsreluctance to become too involved with corporate agendas.In 2000 Negroponte stepped down as director of the MediaLab, gradually becoming less involved in the ongoing reorganizationof the institution. In 2006 he also relinquishedhis post as chairman, though he has retained his post asprofessor at MIT.One Laptop per ChildIn recent years Negroponte has focused his efforts ondesigning and distributing low-cost laptop PCs to millionsof children in developing nations. (The project is called“One Laptop per Child.”) In 2005 at the World Summit onthe Information Society held in Tunis, Negroponte unveileda $100 laptop called the Children’s Machine. However, inthe next few years commitments from participating nationshave been slower than anticipated. Undaunted, Negropontein 2007 announced a new way to distribute the machines—make them such an attractive buy that consumers in developedcountries would be willing to pay a few hundreddollars for two of them—one for the consumer and one togo to a student in a developing country.Negroponte also continues to be active as an investoror board member in technology startups as well as being aboard member of Motorola and a member of the editorialboard of the Wall Street Journal.Further ReadingHamm, Steve. “Give a Laptop and Get One.” BusinessWeek, September24, 2007. Available online. URL: http://www.businessweek.com/technology/content/sep2007/tc20070923_960941.htm. Accessed October 4, 2007.Negroponte, Nicholas. Being Digital. New York: Vintage Books,1996.———. “Creating a Culture of Ideas.” Technology Review, February2003. Available online. URL: http://www.technologyreview.com/Biztech/13074/. Accessed October 4, 2007.Nicholas Negroponte (home page). Available online. URL: http://web.media.mit.edu/~nicholas/. Accessed October 4, 2007.Pogue, David. “Laptop with a Mission Widens Its Audience.” NewYork Times, October 4, 2007. Available online. URL: http://www.nytimes.com/2007/10/04/technology/circuits/04pogue.html. Accessed October 5, 2007.netiquetteAs each new means of communication and social interactionis introduced, social customs and etiquette evolve inresponse. For example, it took time before the practice ofsaying “hello” and identifying oneself became the universalway to initiate a phone conversation.By the 1980s, a system of topical news postings (seenetnews and newsgroups) carried on the Internet wasbecoming widely used in universities, the computer industry,and scientific institutions. Many new users did notunderstand the system, and posted messages that wereoff topic. Others used their postings as to insult or attack(“flame”) other users, particularly in newsgroups discussingperennially controversial topics such as abortion. Whena significant number of postings in a newsgroup are devotedto flaming and counter-flaming, many users who had soughtcivilized, intelligent discussion leave in protest.In 1984, Chuq von Rospach wrote a document entitled“A Primer on How to Work with the Usenet Community.” Itand later guides to net etiquette or “netiquette” offered usefulguidelines to new users and to more experienced userswho wanted to facilitate civil discourse. These suggestionsinclude:• Learn about the purpose of a newsgroup before youpost to it. If a group is moderated, understand themoderator’s guidelines so your postings won’t berejected.• Before posting, follow some discussions to see whatsort of language, tone, and attitude seems to be appropriatefor this group.

332 Net Neutrality• Do not post bulky graphics or other attachmentsunless the group is designed for them.• Avoid “ad hominem” (to the person) attacks whendiscussing disagreements.• Do not post in ALL CAPS, which is interpreted as“shouting.”• Check your postings for proper spelling and grammar.On the other hand, avoid “flaming” other usersfor their spelling or grammar errors.• When replying to an existing message, includeenough of the original message to provide context foryour reply, but no more.• If you know the answer to a question or problemraised by another user, send it to that user by e-mail.That way the newsgroup doesn’t get cluttered up withdozens of versions of the same information.In 1994, a firm of immigration attorneys enraged muchof the online community by posting messages offering theirservices in each of the thousands of different newsgroups.“Spam” was born. Technically savvy users responded bycreating “cancelbots” or programs that attempt to detectand automatically delete postings containing spam. Today,spam is mainly conveyed by e-mail, with mail servers andclient programs offering various options for blocking it(see spam).Netiquette in the 21st CenturyIn the new century, newsgroups and traditional conferencingsystems have diminished in importance, but e-mailis more pervasive than ever, and a variety of new onlinemedia have emerged (see, for example, blogs and blogging).Many of the tried-and-true rules for newsgroup postingsapply as well to other media, but there are also newconsiderations.As many politicians and business executives havelearned to their dismay, e-mail must be assumed to beessentially as permanent as a handwritten letter. Similarly,blogs, postings to sites such as MySpace (see social networking),and other online content can be copied, linkedto, archived, or otherwise persist for many years. Today’sintemperate remarks may emerge years later when a prospectiveemployer “googles” a job candidate.Blogs are meant to link and be linked to, so issues ofproperly crediting material and respecting copyright canbe important. This can also apply to contributions to content-sharingsites and to articles for wikis (see wikis andWikipedia); Wikipedia has evolved a rather comprehensiveset of standards whereby readers can “flag” content that isproblematic.Further ReadingHousley, Sharon. “Blog and RSS Feed Etiquette.” Available online.URL: http://www.small-business-software.net/blog-etiquette.htm. Accessed August 16, 2007.Kallos, Judith. Because Netiquette Matters! Your ComprehensiveGuide to E-mail Etiquette and Proper Technology Use. Philadelphia:Xlibris 2004.McKay, Dawn Rosenberg. “Email Etiquette.” Available online.URL: http://careerplanning.about.com/od/communication/a/email_etiquette.htm. Accessed August 16, 2007.Netiquette Home Page. Available online. URL: http://www.albion.com/netiquette/. Accessed August 16, 2007.Strawbridge, Matthew. Netiquette: Internet Etiquette in the Age ofthe Blog. Cambridge, U.K.: Software Reference Ltd., 2006.Von Rospach, Chuq. “A Primer on How to Work with the UsenetCommunity.” Available online. URL: http://faqs.cs.uu.nl/nadir/usenet/primer/part1.html.Accessed August 16, 2007.Net NeutralityIn recent years there has been growing concern that Internetusers may eventually be treated differently by service providersdepending on the kind of data they download or thekind of application programs they use online. Advocates ofnetwork (or net) neutrality (see for example Cerf, Vincent)want legislation that would bar cable, DSL, or other providers(see broadband and Internet service provider) frommaking such distinctions, such as by charging content providershigher fees for high volumes of data or even blockingcertain applications. Advocates of net neutrality believe that,since there are rather limited choices for broadband Internetservice, discrimination on the basis of Web content couldlead to a loss of freedom for consumers and providers alike.Critics of the net neutrality proposal tend to discountsuch concerns. One analogy they use is traditional mail.Users can choose different types of shipping service, buthaving overnight service available does not mean that packagescannot be delivered using cheaper means. Likewise,they believe that the market can provide “tiers” of Internetservice without disenfranchising any providers or users.Increasing concern about the issue began in 2005 whenthe Federal Communications Commission announcedthat broadband (cable and DSL) Internet would be treatedunder the less stringent Title I information service underthe Communications Act of 1934, rather than being treatedunder Title II as a “common carrier” like traditional phoneservice. At the same time, the agency issued policy guidelinesthat promoted free access, consumer choice, and competition.However these guidelines have no legal force.In June 2007 the Federal Trade Commission (FTC) moreor less sided with the critics of net neutrality by urgingregulators to be careful about imposing rules that wouldprevent providers from innovating in offering premium services.Meanwhile two proposed net neutrality bills failed topass Congress in 2006. However, in July 2008 the FCC in a3-2 decision ordered Comcast, the largest U.S. cable serviceprovider, to stop degrading service to users who used filesharingprotocols.It should be noted that a number of rules restrictingcertain kinds of Internet access already exist. Major serviceproviders have agreements called “peering arrangements”that specify how certain kinds of transmissions will behandled. Many service providers also block certain dataports to reduce the spread of spam by insecure systems ortry to restrict the use of peer-to-peer (P2P) systems (seefile-sharing and p2p networks).

netnews and newsgroups 333In the long run a balance will likely be struck betweenproviders’ need to control traffic to maintain efficiency andquality of service (QoS) and the rights of users to exchangeinformation and resources freely.Further Reading“Crackdown: Comcast Blocks Peer-to-Peer Web Traffic.” Portfolio.com,October 19, 2007. Available online. URL: http://www.portfolio.com/views/blogs/daily-brief/2007/10/19/crackdown-comcast-blocks-peer-to-peer-web-traffic.Accessed October 21, 2007Gilroy, Angela A. Net Neutrality: Background and Issues. CongressionalResearch Service, May 16, 2006. Available online.URL: http://fas.org/sgp/crs/misc/RS22444.pdf. AccessedOctober 25, 2007.Leonard, Thomas M., and Randolph J. May, eds. Net Neutrality orNet Neutering: Should Broadband Internet Services Be Regulated?New York: Springer, 2006.“Network Neutrality in the United States.” Wikipedia. Availableonline. URL: http://en.wikipedia.org/wiki/Network_neutrality_in_the_US. Accessed October 21, 2007.Nuechterlein, Jonathan E., and Philip J. Weiser. Digital Crossroads:American Telecommunications Policy in the Internet Age. Cambridge,Mass.: MIT Press, 2007.netnews and newsgroupsOriginally called Usenet and originating in the UNIX usercommunity in the late 1970s, netnews is distributed todayover the Internet in the form of thousands of newsgroupsdevoted to just about every imaginable topic.DevelopmentBy the late 1970s, researchers at many major universitieswere using the UNIX operating system (see UNIX). In 1979,a suite of utilities called UUCP was distributed with thewidely used UNIX Version 7. These utilities could be usedto transfer files between UNIX computers that were linkedby some form of telephone or network connection.Two Duke University graduate students, Tom Truscottand Jim Ellis, decided to set up a way in which users on differentcomputers could share a collection of files containingtext messages on various topics. They wrote a simple set ofshell scripts that could be used for distributing and viewingthese message files. The first version of the news networklinked computers at Duke and at the University of NorthCarolina. Soon these programs were revised and rewrittenin the C language and distributed to other UNIX users asthe “A” release of the News software.During the 1980s, the news system was expanded andfeatures such as moderated newsgroups were added. As theInternet and its TCP/IP protocol (see tcp/ip) became amore widespread standard for connecting computers, a versionof News using the NNTP (Network News TransmissionProtocol) over the Internet was released in 1986. Netnewsis a mature system today, with news reading software availablefor virtually every type of computer.Structure and FeaturesNetnews postings are simply text files that begin with a setof standard headers, similar to those used in e-mail. (Likee-mail, news postings can have binary graphics or programfiles attached, using a standard called MIME, for MultipurposeInternet Mail Extensions.)The files are stored on news servers—machines thathave the spare capacity to handle the hundreds of gigabytesof messages now posted each week. The files are stored ina typical hierarchical UNIX fashion, grouped into approximately75,000 different newsgroups.As shown in the following table, the newsgroups are brokendown into 10 major categories. The names of individualgroups begin with the major category and then specify subdivisions.For example, the newsgroup comp.sys.ibm.pcdeals with IBM PC-compatible personal computers, whilecomp.os.linux deals with the Linux operating system.Categoryaltbizcomphumanitiesmisc.newsrecscisoctalkMAIN DIVISIONS OFNETNEWS NEWSGROUPSCoverageAn alternative system with its own completeselection of topics.Business-related discussion, products, etc.Computer hardware, software and operatingsystems.Arts and literature, philosophy, etc.Various topics that don’t fit in anothercategory.Announcements and information relating tothe news system itself.Sports, games, and hobbies.The sciences.Social and cultural issues.Current controversies and debates.Distribution and ReadingThe servers are linked into a branching distribution system.Messages being posted by users are forwarded to the nearestmajor regional “node” site, which in turn distributesthem to other major nodes. In turn, when messages arriveat a major node from another region, they are distributedto all the smaller sites that share the newsfeed. Due to thevolume of groups and messages, many sites now choose toreceive only a subset of the total newsfeed. Sites also determinewhen messages will expire (and thus be removed fromthe site).There are dozens of different news reading programsthat can be used to view the available newsgroups andpostings. On UNIX systems, programs such as elm and tinare popular, while other newsreaders cater to Windows,Macintosh, and other systems. Major Web browsers such asNetscape and Internet Explorer offer simplified news readingfeatures. To use these news readers, the user accessesa newsfeed at an address provided by the Internet ServiceProvider (ISP). There are also services that let users simplynavigate through the news system by following the linkson a Web page. The former service called DejaNews, now

334 networkGoogle Groups, is the best-known and most complete suchsite.Further ReadingGoogle Groups. Available online. URL: http://groups.google.com.Accessed August 16, 2007.Hauben, Michael, and Ronda Hauben. Netizens: On the History andImpact of Usenet and the Internet. Los Alamitos, Calif.: IEEEComputer Society Press, 1997.Lueg, Christopher, and Danyel Fisher, eds. From Usenet to CoWebs:Interacting with Social Information Spaces. London: Springer,2003.Pfaffenberger, Bryan. The USENET Book: Finding, Using, and SurvivingNewsgroups on the Internet. Reading, Mass.: Addison-Wesley, 1995.Spencer, Henry, and David Lawrence. Managing Usenet. Sebastopol,Calif.: O’Reilly, 1998.networkIn the 1940s, the main objective in developing the first digitalcomputers was to speed up the process of calculation. Inthe 1950s, the machines began to be used for more generaldata-processing tasks by governments and business. By the1960s, computers were in use in most major academic, government,and business organizations. The desire for usersto share data and to communicate both within and outsidetheir organization led to efforts to link computers togetherinto networks.Computer manufacturers began to develop proprietarynetworking software to link their computers, but they werelimited to a particular kind of computer, such as a DEC PDPminicomputer, or an IBM mainframe. However, the U.S.Defense Department, seeing the need for a robust, decentralizednetwork that could maintain links between theircomputers under wartime conditions, funded the developmentof a protocol that, given appropriate hardware tobridge the gap, could link these disparate networks (seeInternet, local area network).Network ArchitectureToday’s networks are usually defined by open (that is, nonproprietary)specifications. According to the OSI (open systemsinterconnection) model, a network can be consideredto be a series of seven layers laid one atop another (see datacommunication).The physical layer is at the bottom. It specifies the physicalconnections between the computers, which can be anythingfrom ordinary phone lines to cable, fiber optic, orwireless. This layer specifies the required electrical characteristics(such as voltage changes and durations that constitutethe physical signal that is recognized as either a 1 or 0in the “bit stream.”The next layer, called the data link layer, specifies howdata will be grouped into chunks of bits (frames or packets)and how transmission errors will be dealt with (see errorcorrection).The network layer groups the data frames as parts of aproperly formed data packet and routes that packet fromthe sending node to the specified destination node. A varietyof routing algorithms can be used to determine the mostefficient route given current traffic or line conditions.The transport layer views the packets as part of a completetransmission of an object (such as a Web page) andensures that all the packets belonging to that object aresorted into their original sequence at the destination. Thisis necessary because packets belonging to the same messagemay be sent via different routes in keeping with trafficor line conditions.The session layer provides application programs communicatingover the network with the ability to initiate,terminate, or restart an interrupted data transfer.The presentation layer ensures that data formats areconsistent so that all applications know what to expect.This layer can also provide special services (see encryptionand data compression).Finally, the application layer gives applications highlevelcommands for performing tasks over the network,such as file transfer protocol (ftp).Most modern operating systems support this model.The Internet protocol (see TCP/ip) has become the linguafranca for most networking, so modern versions of MicrosoftWindows and the Macintosh Operating System as wellas all versions of UNIX provide the services that applicationsneed to make and manage TCP/IP connections.Networks that link computers remotely (such as overphone lines) are sometimes called wide area networks, orWANs. Networks that link computers within an office,home, or campus, usually using cables, are called localarea networks (LANs). See local area network for moredetails about LAN architecture and software.TrendsIt has become the norm for desktop and portable computersto have access to the Internet. A computer from whichone cannot send or receive e-mail or view Web pages almostgives the perception of being crippled, because so manyapplications now assume that they can access the network.For example, the latest antivirus programs regularly checktheir manufacturer’s Web site and download the latest virusdefinitions and software patches. Recent versions of Windows,too, include a built-in update facility that can obtainsecurity patches and newer versions of device drivers.The flip side of the power of networking to keep everyPC (and its user) up to date is the vulnerability to bothintrusion attempts and viruses (see computer crime andsecurity). Virtually all networks include a layer of softwarewhose job it is to attempt to block intrusions and protectsensitive information (see firewall).Besides attending to security, network administratorsand engineers must continually monitor the trafficon the network, looking for bottlenecks, such as an oftenrequesteddatabase being stored on a file server with a relativelyslow hard drive. Besides upgrading key hardware,another approach to relieve congestion is to adopt a distributeddatabase (see database management system)that stores “data objects” throughout the network and candynamically relocate them to improve access.

neural interfaces 335The growing appetite for data-rich applications such ashigh-fidelity audio and video (see streaming and multimedia)tends to put a strain on the capacity of most networks.In response, institutional users look to optical fiber andother high capacity connections (see bandwidth), whilehome users are rapidly switch in from dial-up service onregular phone lines (see modem) to DSL phone lines andcable.While existing network architectures have workedremarkably well, they were designed for only a small fractionof today’s traffic. There have been a number of initiativesand proposals for higher capacity networks andfor integrating new features (such as security and e-mailsender verification). For a review of these developments, seeInternet architecture and governance.Further ReadingDerfler, Frank J., Jr., and Les Freed. How Networks Work. 7th ed.Indianapolis: Que, 2004.Donahue, Gary. Network Warrior. Sebastapol, Calif.: O’ReillyMedia, 2007.Komar, Brian. Sams Teach Yourself TCP/IP Networking in 21 Days.2nd ed. Indianapolis: Sams, 2002.Kozierok, Charles. “The TCP/IP Guide.” Available online. URL:http://www.tcpipguide.com/free/index.htm. Accessed August16, 2007.Tanenbaum, Andrew S. Computer Networks. 4th ed. Upper SaddleRiver, N.J.: Prentice Hall, 2002.networked storageWith huge databases, e-commerce and other Web servers,and even home media centers, more data needs to be servedover networks than ever before. There are two commonways to provide storage for databases and other resourceson a network.A network attached storage (NAS) unit can be thought ofas a dedicated data storage unit that is available to all usersof a network. Unlike a traditional dedicated file storage unit(see file server), a NAS unit typically has an operatingsystem and software designed specifically (and only) forproviding data storage services. The actual storage is usuallyprovided by an array of hard drives (see raid). Fileson the NAS are accessed through protocols such as SMB(server message block), common on Windows networks,and NFS (network file system), used on many UNIX andsome Linux networks. In recent years smaller, lower-costNAS devices have become available for smaller networks,including home networks, where they can store music,video, and other files (see also media center PC).Storage Area Network (SAN)Although it sounds similar, a storage area network (SAN)does not function as its own file server. Rather, it attachesstorage modules such as hard drives or tape libraries to anexisting server so that it appears to the server’s operatingsystem as though it were locally attached. Typically theprotocol used to attach the storage is SCSI (see SCSI), butthe physical connection is fiber or high-speed Ethernet. Theemphasis for SAN applications is the need for fast access todata, such as in large online databases, e-mail servers, andhigh-volume file servers. SANs offer great flexibility, sincestorage can be expanded without changing the networkstructure, and a replacement server can quickly be attachedto the storage in case of hardware failure.Further ReadingBird, David. “Storage Basics: Storage Area Networks.” Availableonline. URL: http://www.enterprisestorageforum.com/sans/features/article.php/981191. Accessed October 5, 2007.NAS. Network World. Available online. URL: http://www.networkworld.com/topics/nas.html. Accessed October 5,2007.Network Attached Storage Reviews and Price Comparisons. PCMagazine. Available online. URL: http://www.pcmag.com/category2/0,1738,677853,00.asp. Accessed October 5, 2007.Poelker, Christopher, and Alex Nikitin. Storage Area Networks forDummies. New York: Wiley, 2003.Preston, W. Curtis. Using SANs and NAS. Sebastapol, Calif.:O’Reilly, 2002.Tate, Jon, Fabiano Lucchese, and Richard Moore. Introductionto Storage Area Networks. 4th ed. IBM Redbooks. Availableonline. URL: http://www.redbooks.ibm.com/redbooks/pdfs/sg245470.pdf. Accessed October 5, 2007.neural interfacesIn the kind of science fiction sometimes called “cyberpunk,”people are able to “jack in” or connect their brains directly tocomputer networks. Because of this direct input into the brain(or perhaps the optic and other sensory nerves), a personwho is jacked in experiences the virtual world as fully real,and can (depending on the world’s rules) manipulate it withhis or her mind. This kind of all-immersive virtual reality isstill science fiction, but today people are beginning to controlcomputers and artificial limbs directly with their minds.NeuroprostheticsNeuroprosthetics is the creation of artificial limbs or sensoryorgans that are directly connected to the nervous system.The first (and most widely used) example is the cochlearimplant, which can restore hearing by taking sound signalsfrom a microphone and converting them to electricalimpulses that directly stimulate auditory nerves within thecochlea, a part of the inner ear. Similarly, experimental retinalimplants that stimulate optic nerves are beginning tooffer crude but useful vision to certain blind patients.Research in connecting the brain to artificial arms orlegs is still in its early stages, but scientists using microelectrodearrays have been able to record signals from thebrain’s neurons and correlate them to different types ofmotor movements. In a series of experiments at Duke University,researchers first trained a monkey to operate a joystickto move a shape in a video game. They then recordedand analyzed the signals produced by the monkey’s brainwhile playing the game, and correlated them with themotor movements in the joystick. Next, they replicatedthese movements with a robotic arm as the monkey movedthe joystick. Finally, they were able to train the monkey tomove the robotic arm without using the joystick at all, simplyby “thinking” about the movements.

336 neural networkwebmd.com/stroke/news/20040415/Brain-Implants. AccessedOctober 5, 2007.Cooper, Huw, and Louise Craddock, eds. Cochlear Implants: APractical Guide. 2nd ed. Hoboken, N.J.: Wiley, 2006.Eisenberg, Anne. “What’s Next: Don’t Point, Just Think: The BrainWave as Joystick.” New York Times, March 28, 2002. Availableonline. URL: http://query.nytimes.com/gst/fullpage.html?res=9C01E7D8103BF93BA15750C0A96 49C8B63. AccessedOctober 5, 2007.Graham-Rowe, Duncan. “World’s First Brain Prosthesis Revealed.”New Scientist, March 12, 2003. Available online. URL: http://www.newscientist.com/article/dn3488.html. Accessed October5, 2007.He, Bin, ed. Neural Engineering. New York: Kluwer Academic,2005.“New Prosthetic Devices Will Convert Brain Signals into Action.”Science Daily, October 4, 2007. Available online. URL: http://www.sciencedaily.com/releases/2007/10/071003130747.htm.Accessed October 5, 2007.Experimental neural interfaces link nerve impulses to a computer,allowing users to control computers (and even remote robots) literallyby thinking.Human subject are now performing similar feats. Thenext step is to build robotic limbs that can be controlledby the person thinking in a certain way. Ideally, a personshould be able to think about clenching a hand or tappingan index finger and have the prosthetic hand replicate thosemovements. One obvious application for this technology isto enable quadriplegics who have little or no motion capabilityto control wheelchairs or other devices mentally.Future Brain ImplantsAs more is learned about the detailed functioning of neuronalnetworks inside the brain, “cognitive prosthetics” maybecome feasible. One example might be computer memorymodules that might act as a surrogate or extension ofhuman memory, perhaps helping compensate for loss ofmemory due to age or disease. (Early experiments on interfacingto the hippocampus, a part of the brain important forforming memories, have been underway since 2003.)Other possibilities might include processors that couldgive a person the ability to think about a mathematicalproblem and “see” the answer, or to search databases or theWeb simply by visualizing or thinking about the informationdesired.Further Reading“Brain Implants Move at the Speed of Thought.” WebMD MedicalNews, April 15, 2004. Available online. URL: http://www.neural networkWhen digital computers first appeared in the late 1940s, thepopular press often referred to them as “electronic brains.”However, computers and living brains operate very differently.The human brain contains about 100 billion neurons,and each neuron can form connections to as manyas a thousand neighboring ones. Neurons respond to electronicsignals that jump across a gap (called a synapse)and into electrodelike dendrons. The incoming signals formcombinations that in turn determine whether the neuronbecomes “excited” and in turn emits a signal through itsaxon. Clumps of neurons, therefore, act as networks that ineffect sum up incoming signals and develop a response tothem. That is, they “learn.”In a conventionally operated computer, the “neurons”(memory locations) are not inherently connected, and thecentral processing unit (CPU) uses arbitrary, interchangeablememory locations for storing data. Algorithms writtenby a programmer and implemented in instructions executedby the CPU impose cognition, to the extent one can speakof it in computers. In the brain, however, cognition seemsto be something that emerges from the cooperating activitiesand connections of the neurons in response to sensestimuli, and possibly the creation of agentlike entities, asdescribed in Marvin Minsky’s book The Society of Mind.Alan Turing and John von Neumann (see Turing, Alanand von Neumann, John) had established the universalityof the computer. That is, any calculation or logical operationthat can be performed at all can be performed by anappropriate computer program. This means that the “brain”model of a network of interconnected neurons can also beimplemented in a computer. During the 1940s, Warren S.McCulloch and Walter Pitts developed an electronic “neuron”in the form of a binary (on/off) switch that could belinked into networks and used to perform logical functions.During 1950s, Marvin Minsky, working at the MIT ArtificialIntelligence Laboratory (see Minsky, Marvin) furtherdeveloped these concepts, and Frank Rosenblatt developeda classic form of neural network called a Perceptron. Thisconsists of a network of processing elements (that is, func-

nonprocedural languages 337tions), each of which are presented with weighted inputs(called vectors) from which it calculates an output valueof either true (1) or false (0). The designer of the systemknows what the correct output should be. If a given element(or node) produces the correct output, no changes aremade. If it produces the wrong output, however, the weightsgiven for each input are changed by some increment, plusa further adjustment or “bias” factor. This adjustment isrepeated for all units as necessary until the output is correct.In other words, each neuron is constantly adaptingthe way it evaluates its inputs and thus its output, and thatoutput is in turn being fed into the evaluation process ofthe neighboring neurons. (In practice, a neural network canhave several layers of processing units, with one layer providinginputs to the next.)For example, suppose a neural network is being trainedto recognize objects based on the light being received froman array of sensors. The sensor readings are interpreted bya number of “neurons,” which should output 1 if part of thedesired object exists at the location scanned by its sensor.At first there will be many false readings—points at whichpart of the object is not recognized, or is falsely recognized.However, after many cycles of adjustment this “supervisedlearning” process results in a neural network that has ahigh probability of being able to identify all objects of agiven general form. What is significant here is that a generalizedability has been achieved, and it has emerged withoutany specific programming being required!In a computer neural network the “neurons” or nodes are “trained”to detect a pattern by being reinforced when they successfully registerit.Neural networks have been making their way into commercialapplications. They can be used to help robots recognizethe key components of their environment (see roboticsand computer vision), for interpreting spoken language(see speech recognition and synthesis), and for problemsin classification and statistical analysis (see data mining).In general, the neural network approach is most useful forapplications where there is no clear algorithmic approachpossible—in other words, applications that deal with theoften “fuzzy” realities of daily life (see fuzzy logic).Further ReadingBishop, Christopher M. Neural Networks for Pattern Recognition.New York: Oxford University Press, 1995.Haykin, Simon. Neural Networks: A Comprehensive Foundation. 2nded. Upper Saddle River, N.J.: Prentice Hall, 1998.McNellis, Paul D. Neural Networks in Finance: Gaining PredictiveEdge in the Market. Burlington, Mass.: Elsevier AcademicPress, 2005.“Neural Networks & Connectionist Systems.” Association for theAdvancement of Artificial Intelligence. Available online. URL:http://www.aaai.org/AITopics/html/neural.html. AccessedAugust 16, 2007.nonprocedural languagesMost computer languages are designed to facilitate theprogrammer declaring suitable variables and other datastructures, then encoding one or more procedures formanipulating the data to achieve the desired result (seedata types and procedures and functions). A furtherrefinement is to join data and data manipulation proceduresinto objects (see object-oriented programming).However, since the earliest days of computing, programmersand language designers have tried to create higherlevel,more abstract ways to specify what a program shoulddo. Such higher-level specifications are, after all, easier forpeople to understand. And if the computer can do the jobof translating a high-level specification such as “Find allthe customers who haven’t bought anything in 30 days andsend them this e-mail message” into the appropriate proceduralsteps, people will be able to spend less time codingand debugging the program.It is actually best to think of a continuum that has atone end highly detailed procedures (see assembler) and atthe other end an English-like syntax like that given above.Already in an early language like FORTRAN the emphasisis moving away from the details of how you multiply numbersand store the result to simply specifying the operationmuch like the way a mathematician would write it on ablackboard. such as T = I + M. COBOL can render suchspecifications even more readable, albeit verbose: ADD I TOM GIVING T, for example. However, these languages arestill essentially procedural.Some languages are less procedural in that they hidemost of the details (or subprocedures) involved in carryingout the desired operation. For example, in modern databaselanguages such as SQL what would be a procedure (or a setof procedures) in some languages is treated as a query at ahigh level (see SQL). For example:

338 numeric dataselect customer where (today - customer.lastpurchasedate) > 30Programming packages such as Mathematica are alsononprocedural in that they allow for problems to be statedusing the same symbolic notation that mathematiciansemploy, and many standard procedures for solving or transformingequations are then carried out automatically.Other examples of relatively nonprocedural languagesinclude logic-programming languages (see Prolog andexpert systems) and languages where the desired resultsare built up from defining functions rather than through aseries of procedural steps (see lisp and functional languages).Further ReadingAbraham, Paul W., et al. Functional, Concurrent and Logic ProgrammingLanguages. Vol. 4 of Handbook of Programming Languages,edited by Peter H. Salus. Indianapolis: MacmillanTechnical Publishing, 1998.Gilmore, Stephen, ed. Trends in Functional Programming. Portland,Ore.: Intellect, 2005.Truitt, Thomas D., Stuart B. Mindlin, and Tarralyn A. Truitt. AnIntroduction to Nonprocedural Languages: Using NPL. NewYork: McGraw-Hill, 1983.numeric dataText characters and strings can be stored rather simply incomputer memory, such as by devoting 8 bits (one byte) or16 bits to each character. The storage of numbers is morecomplex because there are both different formats and differentsizes of numbers recognized by most programminglanguages.Integers (whole numbers) have the simplest representation,but there are two important considerations: the totalnumber of bits available and whether one bit is used to holdthe sign.Since all numbers are stored as binary digits, an unsignedinteger has a range from 0 to 2 bits where “bits” is the totalnumber of bits available. Thus if there are 16 bits available,the maximum value for an integer is 65535. If negativenumbers are to be handled, a signed integer must be used(in most languages such as C, C++, and Java, an integer issigned unless unsigned is specified). Since one bit is usedto hold the sign and each bit doubles the maximum size, itfollows that a signed integer can have only half the rangeabove or below zero. Thus, a 16-bit signed integer can rangefrom -32,768 to 32,767.One complication is that the available sizes of integersdepend on whether the computer system’s native data sizeis 16, 32, or 64 bits. In most cases the native size is 32 bits,so the declaration “int” in a C program on such a machineimplies a signed 32-bit integer that can range from - 2 31 or-2,147,483,647 to 2 31 -1, or 2,147,483,647. However, if one isusing large numbers in a program, it is important to checkthat the chosen type is large enough. The long specifier isoften used to indicate an integer twice the normal size, or64 bits in this case.Floating Point NumbersNumbers with a fractional (decimal) part are usually storedin a format called floating point. The “floating” means thatthe location of the decimal point can be moved as necessaryto fit the number within the specified digit range. A floatingpoint number is actually stored in four separate parts. Firstcomes the sign, indicating whether the number is negativeor positive. Next comes the mantissa, which contains theactual digits of the number, both before and after the decimalpoint. The radix is the “base” for the number systemused. Finally, the exponent determines where the decimalpoint will be placed.For example, the base 10 number 247.35 could be representedas 24735 × 10 -2 . The -2 moves the decimal pointat the end two places to the left. However, floating-pointnumbers are normalized to a form in which there is just onedigit to the left of the decimal point. Thus, 247.35 wouldactually be written 2.4735 × 10 2 . This system is also knownas scientific notation.As noted earlier, actual data storage in modern computersis always in binary, but the same principle applies.According to IEEE Standard 754, 32-bit floating-point numbersuse 1 bit for the sign, 8 bits for the exponent, and 23bits for the mantissa (also called the significand, since itexpressed the digits that are significant—that is, guaranteednot to be “lost” through overflow or underflow in processing).The double precision float, declared as a “double”in C programs, uses 1, 11, and 52 bits respectively.Programmers who use relatively small numbers (such ascurrency amounts) generally don’t need to worry about lossof precision. However, if two numbers being multiplied arelarge enough, even though both numbers fit within the 32-bit size, their product may well generate more digits thancan be held within the 23 bits available for the mantissa.This means that some precision will be lost. This can beavoided to some extent by using the “double” size.Since floating-point calculations use more processorcycles (see microprocessor) than integer calculations,processor designers have paid particular attention toimproving floating-point performance. Indeed, processorsare often rated in terms of “megaflops” (millions of floatingpointoperations per second) or even “gigaflops” (billions offlops).Further Reading“IEEE Standard for Floating Point Arithmetic.” Available online.URL: http://www.psc.edu/general/software/packages/ieee/ieee.html. Accessed August 16, 2007.“Numeric Data Types and Expression Evaluation [in C].” Availableonline. URL: http://www.psc.edu/general/software/packages/ieee/ieee.html. Accessed August 16, 2007.Sebesta, Robert W. Concepts of Programming Languages. 8th ed.Boston: Addison-Wesley, 2007.“Type Conversion and Conversion Operators in C#.” Availableonline. URL: http://www.psc.edu/general/software/packages/ieee/ieee.html. Accessed August 16, 2007.“xmL Schema Numeric Data Types.” Available online. URL: http://www.psc.edu/general/software/packages/ieee/ieee.html.Accessed August 16, 2007.

Oobject-oriented programming (OOP)During the last two decades the way in which programmersview the data structures and functions that make up programshas significantly changed. In simplified form the earliestapproach to programming was roughly the following:• Determine what results (or output) the user needs.• Choose or devise an algorithm (procedure) for gettingthat result.• Declare the variables needed to hold the input data.• Get the data from the file or user input.• Assign the data to the variables.• Execute the algorithm using those variables.• Output the result.While this type of approach often works well for small“quick and dirty” programs, it becomes problematic as thecomplexity of the program increases. In real-world applicationsdata structures (such as for a customer record orinventory file) are accessed and updated by many differentroutines, such as billing, inventory, auditing, summaryreport generation, and so on. It is easy for a programmerworking on one part of the program to make a change in adata field specification (such as changing its size or underlyingdata type) without other programmers finding out.Suddenly, other parts of the program that relied on theoriginal definitions start to “break,” giving errors, or worse,silently produce incorrect results.During the 1970s, computer scientists advocated a varietyof reforms in programming practices (see structuredprogramming) in an attempt to make code both more readableand safer from unwanted side effects. For example, the“goto” or arbitrary jump from one part of the program toanother was discouraged in favor of strictly controlled iterativestructures (see loop). Also encouraged was the declarationof local variables that could not be changed fromoutside the procedure in which they were defined.Development of Object-Oriented LanguagesHowever, a more radical programming paradigm was alsoin the making. In existing languages, there is no inherentconnection between data and the procedures that operateupon that data. For example, the employee record may bedeclared somewhere near the beginning of the program,while procedures to update fields in the record, copy therecord, print the record, and so on may well be found manypages deeper into the program.A new approach, object-oriented programming is basedon the fact that in daily life we interact with thousandsof objects. An object, such as a ball, has properties (suchas size and color) and capabilities (such as bouncing). Ininteracting with an object, we use its capabilities. It is muchmore natural to think of an object as a whole than to haveits properties and capabilities jumbled together with thoseof other objects.Simula 67, developed in the late 1960s, was the firstobject-oriented language (see Simula). It was followed inthe 1970s by Smalltalk, a language developed at the Xerox339

340 object-oriented programmingPARC laboratory, home of innovative research in graphicaluser interfaces. Smalltalk, like Windows today, treats eachwindow, menu, and other control on the screen as an object(see Smalltalk). Finally, during the 1980s C++ came intoprominence, adding the essential features of object-orientedprogramming to the already very popular C language.Today most popular mainstream languages, including C++,Java, and Visual Basic, are object-oriented (see C++ andJava). Many specialized database languages are also objectoriented.Elements of Object-Oriented ProgrammingThe various object-oriented languages differ somewhat incapabilities, and of course in syntax. However, being objectorientedgenerally implies that the language has the followingfeatures.Classes and ObjectsAn object is defined using a template called a class. A classcontains both the data needed to characterize the objectand the procedures (sometimes called methods or memberfunctions) needed to work with the object (see class).Thus, there could be a class for circles to be drawn on agraphics display. The class might include as its data the ×and y coordinates for the center of the circle, the size of theradius, whether the circle is filled, the color to be used forfilling, and so on. (See C++ for more examples.)When the program needs to use an object of the class,it declares it in the same way it would an ordinary built-indata type such as an integer. Languages such as C++ providefor a special function called a constructor that can beused to define the processing needed when a new object iscreated—for example, memory allocation and setting initialvalues for variables.To access data or functions within a class, the nameof an object of that class is used, followed by a variable orfunction. Thus, if there’s a class called circle, a programmight specify the following:MyCircle Circle; // Declare an object of theCircle classMyCircle.X = 100; // X coordinate on screenMyCircle.Y = 50; // Y coordinate on screenMyCircle.Radius = 25; // Radius in pixelsMyCircle.Filled = True; // A Boolean constantequal to 1MyCircle.FillColor = Blue; // a previouslydefined color constantOnce these specifications have been made, the circlecan be drawn by calling upon its “draw” method or memberfunction:MyCircle.Draw;The designer of a class can choose to restrict access tocertain data items or functions, using a keyword such asprivate or protected. For example, instead of having thepart of the program that uses the class directly set the xand y coordinates, it could keep those variables private andIn the object-oriented C++ programming language data within aclass can be restricted in several ways. Private data can be accessedonly from within the class itself, or from another class declared tobe a “friend” of the containing class. Protected data has these formsof access, plus it can also be accessed from any class derived fromthe containing class. Finally, Public data or functions (methods)can be accessed from anywhere in the program, and provides theinterface by which the class is used.instead provide a method called SetPos. The class mightthen take the coordinates specified by the user and adjustthem to fit the screen dimensions. The Draw method wouldthen use the adjusted internal coordinates rather than thosesupplied originally by the user.InheritanceMany objects are more elaborate or specialized variations ofmore basic objects. For example, in Microsoft Windows thevarious kinds of dialog boxes are specialized versions of thegeneral Window class. Therefore, the specialized versionis created by declaring it to be derived from a “base class.”Put another way, the specialized class inherits the basicdata and functions available in the base (parent) class. Theprogrammer can then add new data or functions or modifythe inherited ones to create the necessary behavior for thespecialized class.Languages such as C++ allow for a class to be derivedfrom more than one base class. This is called multipleinheritance. For example, a Message Window class mightinherit its overall structure from the Window class andits text-display capabilities from the Message class. However,it can sometimes be difficult to keep the relationshipsbetween multiple classes clear. The Java language takes thealternative approach of being limited to only single inheritanceof classes, but allowing interfaces (specifications ofhow a class interacts with the program) to be multiplyinherited.Polymorphism and OverloadingDifferent kinds of objects often have analogous methods.For example, suppose there is a series of classes that representvarious polygons: square, triangle, hexagon, and

office automation 341so forth. Each class has a method called “perimeter” thatreturns the total distance around the edges of the object. Ifeach of these classes is derived from a base polygon class,each class inherits the base class’s perimeter method andadapts it for its own use. Thus, a square might calculateits perimeter simply by multiplying the length of a side byfour, while the rectangle would have to add up differentsizedpairs of sides, and so on.Similarly, the same operator in a language can have differentmeanings depending on what data types it is beingapplied to. The plus (+) operator, for example, is defined inmost languages so that various types of integers or floatingpointvalues can be added (see numeric data).Object-oriented languages such as C++ allow operatorsto be given additional definitions so they can handleadditional data types, including classes defined by theuser. For example, what might adding the string “object”and the string “oriented” yield? The most sensible answeris a new string that contains both of the original strings:“object oriented.” If one defines a String class, then onecan also define the + operator as a member function of thatclass, such that when something like String1 + String2 isencountered, the expression will be evaluated as the combination(concatenation) of the two strings. The + operatoris said to have been overloaded for use with the Stringclass.EncapsulationThe ability to keep the detailed workings of a class privatepromotes program reliability (see encapsulation).Software developers can create well-organized libraries ofclasses that other programmers can use simply by referringto the interface specifications (see library, program).Encapsulation also makes programs more readable. Onceone understands the capabilities of the objects, it is relativelyeasy to understand the overall operation of theprogram without getting bogged down in details. Objectorientedprogramming takes the encapsulation achievedthrough the earlier structured programming movement andmakes it more integral to the language structure.TrendsObject-oriented programming was initially decried as a fadby some critics. The initial learning curve for traditionallytrained programmers and the overhead that made earlyimplementations of languages such as Smalltalk run slowlyinhibited acceptance of the new paradigm at first. However,the introduction of C++ by Bjarne Stroustrup provided afairly easy path for C programmers into the object-orientedworld. For example, the class was syntactically similar tothe familiar struct.The movement toward object-oriented programming anddesign was also spurred by the more or less coincidentalpopularity of graphical user interfaces such as MicrosoftWindows. Since these systems are built upon event-drivenprogramming using a variety of coexisting objects, theobject-oriented class approach fit such operating systemsmuch more naturally. Thus, during the late 1980s and 1990s,many Windows programmers began to use the MicrosoftFoundation Classes (MFC) as their way to structure theiraccess to the operating system. Similarly, popular languagesfor Web development (see for example Java and C#) arethoroughly object-oriented, and even most scripting languagesalso contain object-oriented features.An object-based approach also fits more naturally intoenvironments where programs and data may be running onmany interconnected computers (see network and multiprocessing).Treating the client and server programs asinteracting objects thus makes sense, as does treating databasesas collections of data objects (see database managementsystem). The object-oriented approach can also beapplied at a higher level of abstraction in designing systems(see design patterns and modeling languages).Further ReadingHamilton, J. P. Object-Oriented Programming with Visual Basic.NET. Sebastapol, Calif.: O’Reilly Media, 2002.Josuttis, Nicolai. Object-Oriented Programming in C++. New York:Wiley, 2002.“Lesson: Object-Oriented Programming Concepts.” The JavaTutorials. Available online. URL: http://www.psc.edu/general/software/packages/ieee/ieee.html. Accessed August 16, 2007.Lutes, Kyle, Alka Harriger, and Jack Purdum. An Information SystemsApproach to Object-Oriented Programming Using MicrosoftVisual C# .NET. Boston: Course Technology, 2005.Prata, Stephen. C++ Primer Plus. 5th ed. Indianapolis: Sams, 2004.Weisfeld, Matt. “The Evolution of Object-Oriented Languages.”Available online. URL: http://www.developer.com/design/article.php/3493761. Accessed August 16, 2007.office automationThe transition from manual to mechanical to electronicprocessing of information in the office spanned most ofthe 20th century. In the previous century, the typewriterallowed for the mechanical production of letters and otherdocuments by skilled workers, accommodating (and perhapsencouraging) a growing amount of paperwork. Atthe turn of the century the card tabulator (see Hollerith,Herman and punched cards and paper tape) began themechanization of information processing.During the first half of the 20th century, mechanical orelectro-mechanical calculators made by such companies asBurroughs came into more widespread use by bookkeepersand clerks (see calculator). Meanwhile, one company,International Business Machines (IBM) came to dominatethe area of card sorting and tabulating equipment.When digital computers first came into commercialuse in the 1950s, they were too large and expensive to beused in ordinary offices. Bookkeepers and other workersdid not deal with computers directly, but were supportedby data processing departments or outside servicebureaus for what became known as electronic data processing,or EDP.By the 1970s, the advent of the microprocessor madedesk-size information processing systems possible (seemicroprocessor). The first widespread application was thededicated word processing system, of which the most successfulversion was developed by An Wang. These systems

342 Omidyar, Pierreprovided for typing and printing documents and storingthem in a file system (see word processing).During the 1980s, the general-purpose desktop computer(see personal computer) became powerful enoughto supplant the dedicated word-processing system. Besidesproviding word-processing functions through ever moreversatile versions of programs such as WordPerfect. Word-Star, and Microsoft Word, the PC could also run programsto support bookkeeping, accounting, mailing list, and otherfunctions (see database management system and spreadsheet).Gradually, many of these separate programs weremerged into office suites such as Microsoft Office (see applicationsuite). Using a suite meant that information couldbe easily transferred between word-processing documents,spreadsheets, and database files, facilitating the generationof many kinds of reports and presentations.Later in the 1980s, two new aspects of office automationbegan to emerge: communication and collaboration. Theuse of special hardware and software to connect PCs withinan office or throughout the organization (see network andlocal area network) made new applications possible. E-mail began to replace printed memos or phone calls as thepreferred way for workers and management to communicate.Programs such as Lotus Notes and Microsoft Outlookadded features such as the ability of workers to share a commoncalendar of tasks, while scheduling software offeredmore elaborate ways to keep track of large, detailed teamprojects (see project management software).Today a variety of tools are available for facilitating collaboration.Most word-processing software now offers a featurecalled revision marking, which lets various editors andreviewers comment on or make revisions to a document.The author can then merge the revisions into a new draft.“Whiteboard” programs let several users on the networkwork simultaneously on the same virtual screen, drawingdiagrams or making outlines.TrendsEven as desk space was being cleared for the first office PCs,pundits began to claim that the “paperless office” was athand. Actually, the first stages of automation contributedto an increase in the use of paper. On the one hand, wordprocessors and other programs made it easier to generatedocuments and keep them up to date. On the other hand,the documents were all printed on paper—in part becausethe ability to share them electronically was nonexistent orrudimentary, and in part because many workers, particularlysenior executives, still preferred to work with paper.The growth of networking made it possible for morepeople to distribute documents electronically, while higherresolutionvideo displays made it easier to view pages onthe screen. During the 1990s, the inexpensive documentscanner (see scanner) made it practicable to scan incomingpaper documents into text files (see optical characterrecognition). While the office is not yet paperless, thetide of paper may now be receding at last.The ubiquity of the Internet and the use of the HTMLformat for documents (see html and lan) characterize thelatest phase in the evolution of office automation. Many corporateprocedure manuals and other resources are now beingstored on company Web sites where they can be updated easilyand consulted with the aid of search engines. Databasesto which workers need shared access are also being hostedthrough Web sites. HTML and XML are emerging as commonformats for exchanging documents between systems,along with Adobe’s Portable Document Format (PDF), whichoffers a faithful reproduction of the printed page.Changes in how the Internet is being used for communicationand collaboration are also having an impacton the office. In particular, blogs are being used as a wayfor key people to keep coworkers updated (see blogs andblogging), and wikis can be an effective way for building acommon knowledge base for both employees and customers(see wikis and Wikipedia).Many workers can now access the full resources of theoffice through laptop computers and Internet connections.Workers on the go can also use handheld or palm computerssuch as the PalmPilot (see pda) to access e-mail,calendar, and other information. The growing use of videoconferencingover the Internet using inexpensive camerasand broadband connections is also promoting the “virtualmeeting” (see video conferencing).Further ReadingBrown, M. Katherine, Brenda Huettner, and Char James-Tanny.Managing Virtual Teams: Getting the Most from Wikis, Blogs,and Other Collaborative Tools. Plano, Tex.: Wordware Publishing,2007.Greenbaum, Joan. Windows on the Workplace: Technology, Jobs, andthe Organization of Office Work. New York: Monthly ReviewPress, 2004.Mobile Office Technology. Available online. URL: http://mobileoffice.about.com/. Accessed August 16, 2007.Obringer, Lee Ann. “How Virtual Offices Work.” Available online.URL: http://communication.howstuffworks.com/virtual-office.htm. Accessed August 16, 2007.Sellen, Abigail J., and Richard H. R. Harper. The Myth of the PaperlessOffice. Cambridge, Mass.: MIT Press, 2002.Scoble, Robert, and Shel Israel. Naked Conversations: How BlogsAre Changing the Way Businesses Talk with Customers. Hoboken,N.J.: Wiley, 2006.Wibbels, Andy. Blogwild!: A Guide for Small Business Blogging. NewYork: Penguin Group, 2006.Omidyar, Pierre(1967– )French-Iranian/AmericanEntrepreneur, InventorOne of the most remarkable stories of the development of e-commerce has been the online auction pioneered by PierreOmidyar and the hugely successful eBay auction site hefounded (see online auctions.)Omidyar was born on June 27, 1967, in Paris. His familyis of Iranian descent. While working in his high schoollibrary Omidyar encountered his first computer and soonwrote a program to catalog books. Omidyar enrolled atTufts University to study computer science. However, afterthree years he became bored with classes and went to work

Omidyar, Pierre 343Pierre Omidyar founded eBay, the world leader in onlineauctions. (Acey Harper / Time Life Pictures / Getty Images)as a programmer. Omidyar helped develop a drawing programfor the new Apple Macintosh, but after a year returnedto finish his degree, which he received in 1988. He thenwent to work for Claris, a subsidiary of Apple. There hedeveloped MacDraw, a very popular application for theMacintosh.By 1991 Omidyar had become interested in an emergingapplication, “pen computing,” which uses a special penand tablet to allow computer users to enter text in ordinaryhandwriting, which would be recognized and convertedto text by special software. Omidyar and three partnersformed a company called Ink Development to work on pencomputing technology. However, the market for such softwarewas slow to develop. The partners changed their companyname to eShop and their focus to e-commerce, theselling of goods and services online. But e-commerce wouldnot become big until the mid-1990s when the graphicalbrowser made the Web attractive and easy to use. MeanwhileOmidyar also did some graphics programming for themovie effects company General Magic.Omidyar retained his interest in e-commerce, with aparticular focus on finding new markets in which buyersand sellers could meet. Online auctions offered one suchmechanism, and Omidyar created a site called AuctionWeb.AuctionWeb was based on a simple idea: Let a user put upsomething for bid, and have the software keep track of thebids from other users until the ending time is reached, withthe highest bid being the winner.At first Omidyar made AuctionWeb free for both buyersand sellers, but as the site exploded in popularity hebegan to charge sellers a small fee to cover his Internetservice costs. As the months passed, thousands of dollars insmall checks began to pour in. Using $1 million he receivedfrom Microsoft for the sale of his former company eShop,Omidyar decided to expand his auction site into a full-timebusiness.Thanks to the Web, it was now possible to run an auctionwithout cataloger, auctioneer, or hotel room. The jobof describing the item could be given to the seller, and ofcourse digital photos or scanned images could be used toshow the item to potential bidders. The buyer would paythe seller directly, and the seller would be responsible forshipping the item.Because overhead costs are essentially limited to maintainingthe Web site and developing the software, the companycould charge sellers about 2 percent instead of the10–15 percent demanded by traditional auction houses.Buyers would pay no fees at all. And because the cost forselling is so low, sellers could sell items costing as little asa few dollars, while regular auction houses generally avoidlots worth less than $50–$100.With the aid of business partner and experienced Webprogrammer Jeff Skoll, Omidyar revamped and expandedthe site, renaming it eBay (combining the “e” in electronicwith the San Francisco Bay near which they lived). Unlikethe typical Web business that promised investors profitsometime in the indefinite future, eBay made money fromthe first quarter and just kept making more.Through their relationship with a venture capital firm,Benchmark, Omidyar and Skoll gained not only $5 millionfor expansion but the services of Meg Whitman, an experiencedexecutive who had compiled an impressive trackrecord with firms such as FTD (the flower delivery service),the toy company Hasbro, Procter & Gamble, and Disney.eBay’s growth continued: by the end of 1997 about 150,000auctions were being held each day.In 1998 they decided to take the company public. By thetime the first trading day ended, Omidyar’s stock was worth$750 million, and Whitman and the other key players hadalso done very well.One possible weakness in the eBay model was that itrelied heavily on trust by the seller and especially the buyer.What if a buyer won an item only to receive something thatwas not as described or, worse, never received anything atall? But while this happened in a small number of cases,Omidyar through his attention to building communitiesfor commerce had devised an interesting mechanism called“feedback.” Both sellers and buyers were encouraged to postbrief evaluations of each transaction, categorized as positive,neutral, or negative. A significant number of negativefeedbacks served as a warning signal, so both sellers andbuyers had an incentive to fulfill their part of the bargain.The system was not perfect, but the continued patronage ofseveral million users suggested that it worked. (An escrowsystem was also made available for use with more expensiveitems.)As the new century dawned, Omidyar became less personallyinvolved with eBay. In 1998 he had stepped down asCEO, the post going to Whitman. In 2004 Omidyar and hiswife, Pam, turned their attention to the Omidyar Network, a

344 online advertisingnew structure that replaces the traditional foundation witha decentralized approach combining nonprofit and for-profitinitiatives focusing on empowering individuals and communities.Omidyar has also been investing in microfinancing(the making of small loans directly to poor entrepreneurs indeveloping countries).Further ReadingCohen, Adam. “Coffee with Pierre: Creating a Web CommunityMade Him Singularly Rich.” Time, December 27, 1999, p. 78ff.———. The Perfect Store: Inside eBay. New York: Little, Brown &Company, 2002.Ericksen, Gregory K. Net Entrepreneurs Only: 10 Entrepreneurs Tellthe Stories of Their Success. New York: Wiley, 2000.Pierre’s Web (blog). http://pierre.typepad.com/. Accessed May 6,2007.Sachs, Adam. “The Millionaire No One Knows.” Gentlemens’ Quarterly,May 2000, p. 235.online advertisingIn the late 1990s “banner ads” started to appear on Websites, and other forms of advertising soon followed. Companiesrushed into the online world, either with the belief thatit had unlimited potential for finding new customers, or outof fear that the competition would get there first. Unfortunatelyit was hard to measure the actual effectiveness ofads, and Web sites (such as for publications) that lookedto third-party advertising as a source of income found theoutlook bleak in the wake of the bursting of the “dot-combubble” of the early 2000 decade.Only a few years later, however, advertisers using newbusiness models and targeting techniques have made onlineadvertising not only a viable business, but a rapidly growingone. (According to the Interactive Advertsing Bureau,Internet advertising revenue in the United States in 2007was $21.2 billion, up 26 percent from 2005.)The effects of the online advertising revolution are ripplingoutward, impacting traditional advertising mediasuch as newspapers (in particular see craigslist), magazines,and even television.Platforms and Types of AdsThere are many different applications that can be accompaniedby different types of advertising. These include e-mails(free e-mail services usually include an ad in every message),newspapers and other publications (often with ads related tothe subject of an accompanying article), and even blogs (seeblogs and blogging). Indeed, the most popular blogs canactually make a reasonable income from advertising.Types of ads include the following:• Banner ads are contained in rectangles, often at the topof the Web page. (Sometimes they can mimic dialogboxes from the operating system.) They still accountfor about half of all online advertising, and can appearon sites of all types.• Pop-up or pop-under ads appear above or beneath thecurrent window, respectively.• Floating ads appear over the main page content, oftenmoving across the screen.• Interstitial ads are displayed before the requestedcontent (such as an article or video) is shown. Theyrun for a specified period of time, although they cansometimes be closed by the viewer.Many ads are animated; some even contain video clips.There are also ads formatted for mobile devices, includingtext messages sent to cell phones.Economics of Online AdvertisingA company or organization can of course advertise its ownproducts or services on its Web site. Alternatively, a sitecan arrange with an online advertiser to carry ads for otherpeoples’ goods or services, in exchange for a fee. The advertiserin turn gets paid by the company whose ads are beingrun. The payment can be calculated in a variety of ways:CPM (cost per thousand people who see the ad), the numberof sales leads, or the number of people who actually buysomething.As the first luster of the Web began to wear off, corporateadvertising departments increasingly wanted bettermeasurements of the exposure their ads were receiving, andwanted ads that were better targeted to people more likelyto “click through” to the advertiser’s site. Since it involvespeople who are already looking for specific things, Websearch is an effective and profitable activity to be linked tocontextually related ads. Google in particular has been verysuccessful in auctioning or selling the opportunity to haveone’s ad appear in the results of a search request containinga specific keyword (see Google).Another way that Google and other large search enginesor portals can make money from advertisers is through“affiliate marketing”; Google’s version is called Ad Sense.Participating Web sites are indexed, and the resulting keywordsare matched with ads awaiting placement. The sitecarrying the ad generally gets a per-click payment. However,the problem of “click fraud” has also arisen: Scammerscan set up an affiliate site and then use special software togenerate the clicks, while making them come from a varietyof sources. Despite these problems, in 2006 about 40 percentof revenue from online advertising was attributed tosearch-related ads.While search engine usage perhaps provides the mostdirect indication of consumer interests, considerable attentionhas also been focused on developing systems that cantrack where a given individual goes on a large e-commercesite (see cookies), and look for clues about likely futurepurchases (see data mining).Maintaining User InterestThe dark side of online advertising is found in programsthat are surreptitiously installed on users’ PCs and thendownload and display advertising from shady Web operations(see spyware and adware). While many users nowregularly run programs to block such malware, even legitimateonline advertising can irritate users, particularly

online frauds and scams 345when ads are too prominent, float over (and block) text, orlurk behind the browser window. Modern Web browsershave ad-blocking features that work with varying degreesof effectiveness. As with TV, online advertisers increasinglyhave to cope with impatient users who do not have to lookat ads unless they actually want to.Advertisers can employ several strategies to keep userswilling to look at ads. One is to make the ad unobtrusiveand brief, and on the way to something the user reallywants to see. In 2007 YouTube began such advertising.Another is to provide free versions of software or servicesthat, in exchange for being free, require the user to put upwith some screen real estate being devoted to ads. Finally,as with TV, advertising can be woven into the content itself,such as in online computer games.A sensitive area is the attempt to balance advertisers’desire to know as much as possible about consumers’ interestsand buying habits with the same consumers’ concern aboutprotecting their privacy (see privacy in the digital age).Further Reading“Click Fraud: The Dark Side of Online Advertising.” BusinessWeek, October 2, 2006. Available online. URL: http://www.businessweek.com/magazine/content/06_40/b4003001.htm.Accessed October 5, 2007.Davis, Harold. Google Advertising Tools: Cashing In with AdSense,AdWords, and the Google APIs. Sebastapol, Calif.: O’Reilly,2006.Interactive Advertising Bureau. Available online. URL: http://www.iab.net/. Accessed October 5, 2007.Plummer, Joe, et al. The Online Advertising Playbook: Proven Strategiesand Tested Tactics from the Advertising Research Foundation.Hoboken, N.J.: Wiley, 2007.Scott, David Meerman. The New Rules of Marketing & PR: How toUse News Releases, Blogs, Podcasting, Viral Marketing & OnlineMedia to Reach Buyers Directly. Hoboken, N.J.: Wiley, 2007.Search Engine Marketing Professional Organization (SEMPO).Available online. URL: http://www.sempo.org. AccessedOctober 5, 2007.Sloan, Paul. “The Quest for the Perfect Online Ad: Web AdvertisersAre Moving beyond Search, Using Powerful Science toFigure Out What You Want.” Business 2.0 [Magazine]. Availableonline. URL: http://money.cnn.com/magazines/business2/business2_archive/2007/03/01/8401043/index.htm.Accessed October 5, 2007.online frauds and scamsIn the old days con men and scammers went to where therewere a lot of people with loose cash and where anonymitywas the order of the day—perhaps a carnival or fair. Todayin all too many cases the Internet fills this bill. With millionsof inexperienced new users coming online in recentyears, the opportunities for frauds and scams are significant,as is the problem of fighting such crime. In 2007 theInternet Crime Complaint Center (a partnership betweenthe FBI and the National White Collar Crime Center) loggedits one-millionth complaint. Of the 461,096 cases referredto law enforcement agencies, the estimated dollar loss is$647.1 million, with a median loss of $270 per complaint.Many online frauds represent adaptations of traditionalcriminal practices to the online world. E-mail (see spam)carries offers for dubious cures for mostly imagined sexualills, or for prescription drugs at too-good-to-be-true prices,or for “genuine replica Rolex watches.” Internet auctionsites also offer a venue for selling fakes and counterfeits ofvarious sorts. The primary protections for the consumer areknowledge about the goods in question and taking advantageof community resources such as feedback provided byother buyers (see also auctions, online and eBay).Entire fake businesses can appear online, complete withprofessional-quality Web sites. If a prospective purchaserhas never heard of the company, checking with the BetterBusiness Bureau, or looking for a certification such asTrust-E, is a good idea. (Scammers can also impersonatelegitimate businesses in order to get personal informationfrom customers—see phishing and spoofing.)Investments are another fertile area for online scammers.These include “pump and dump” schemes where chatroomor blog postings are used to “talk up” some obscurestock and then cash in when investors start buying it andraising the price. Pyramid schemes and multilevel-marketing(MLM) programs where money from new participantsis used to pay back earlier investors also appear from timeto time.A common theme of victimization seems to be that manyWeb users seem to suspend their usual skepticism and cautionwhen they go online. This is perhaps due to the relativeunfamiliarity of the online world and the lack of experiencein evaluating products, investments, or services.A variety of other frauds and scams appear online or viae-mail with some frequency:• the “419” or “Nigerian money letter” that promises arich cut for helping facilitate a money transfer for adistressed official• fraudulent charitable solicitations, particularly aftersuch disasters as the Asian tsunami or HurricaneKatrina• adoption and marriage scams• educational fraud, such as worthless degrees offeredby unaccredited institutions• dubious employment schemes or “home businesses”involving preparing mailings or medical billing• services that offer to “repair” bad credit ratings• tax-avoidance schemes, often based on nonexistentlegal claims or loopholesFighting Online FraudBecause perpetrators are hard to track down (see anonymityand the Internet), and because of the ability to endlesslycreate new Web sites and e-mails, it is hard to controlthis form of crime (see computer crime and security).However, considerable resources are now being brought tobear, with significant success. Depending on the type offraud, federal agencies such as the Securities and ExchangeCommission (SEC), Federal Trade Commission (FTC), andthe Food and Drug Administration (FDA) will investigate,

346 online gamblingand agencies such as the FBI will pursue perpetrators. Everystate also has an office of consumer protection or consumeraffairs, and local district attorneys may become involvedwhen perpetrators are operating in their area or victimizingresidents.Private agencies also play an important role. Besides theBetter Business Bureau, most industries or professions havesome form of certification of products or practices. Thereare also professional services that will authenticate collectiblessuch as stamps, coins, and sports cards.Government and private agencies also offer a variety ofconsumer education materials that explain common fraudsand suggest ways to shop prudently for goods or services.Further ReadingFederal Bureau of Investigation. “Internet Fraud.” Available online.URL: http://www.fbi.gov/majcases/fraud/internetschemes.htm.Accessed October 6, 2007.Henderson, Harry. Internet Predators (Library in a Book) New York:Facts On File, 2005.Internet Crime Complaint Center. Available online. URL: http://www.ic3.gov/. Accessed October 6, 2007.Securities and Exchange Commission. “Internet Fraud: How toAvoid Internet Investment Scams.” Available online. URL:http://www.sec.gov./investor/pubs/cyberfraud.htm. AccessedFebruary 7, 2008.Silver Lake Editors. Phishing, Spoofing, ID Theft, Nigerian AdvanceSchemes, Investment Frauds, False Sweethearts: How to Recognizeand Avoid Internet Era Rip-offs. Aberdeen, Wash.: SilverLake Publishing, 2006.online gamblingDespite its illegality in the United States, Internet-basedgambling has been very popular—by 2004 more than 20million Americans had tried some form of online gambling,and in 2005 they bet about $5.9 billion.Online casinos appeared in 1995, but at first they couldonly be played “for fun,” with no actual money changinghands. That soon changed: In 1996, InterCasino appeared—it would be the first of hundreds of online casinos, sportsbookmakers, and other types of gambling. Generally theseoperations are based outside of the United States—Caribbeanislands such as Antigua and Curaçao are popular locations.Online casinos offer traditional table games such asblackjack, roulette, and craps. Generally odds and payoffsare comparable to those at traditional casinos. Assumingthe game is honest and properly programmed, the house’srevenue comes from a percentage of the amount bet—blackjackhaving the lowest house percentage and roulette thegreatest. Slot machines (which give an even higher percentageto the house) can also be simulated online.Although occasional cases of software programmed tocheat have been documented, a more common problem isfailure to pay winnings promptly, or at all. Recourse is difficult,since the casino is offshore and the activity is illegalfor U.S. players. Players can, however, consult lists of socalledrogue casinos to be avoided. Some players cheat aswell, typically by opening multiple accounts in order to getthe “signing bonus.”Online PokerOnline poker has become very popular, particularly gamessuch as Texas Hold’Em. Estimated revenues from onlinepoker in the United States were $2.4 billion in 2005.Unlike the case with casino games, online poker playersplay against each other, not the house. The house’s revenuecomes from a “rake,” or percentage, of the pot. Many sitesoffer organized tournaments, and some online players havegone on to win traditional tournaments. (The aptly namedChris Moneymaker won an online tournament, qualifyinghim to enter the 2004 World Series of Poker, which he wenton to win.)Like online casinos, online poker is illegal in the UnitedStates. Proponents argue that while any given hand is random,poker in the long run is a game of skill, not chance. Agroup called the Poker Players Alliance has been lobbyingto exempt poker from Internet gambling laws.A third type of online gambling is sports betting, whichis legal in many countries but only in Nevada in the UnitedStates. The Web has also given sports bettors a forum fordiscussing (or arguing about) teams and their prospects.Legal and Other IssuesIn 1998 the federal government charged more than 20Americans with operating gambling services in violationof the Federal Wire Act, which prohibits wagering over thephone lines used for most Internet transmissions. Most ofthe charges were subsequently dropped or plea-bargained,with only one casino operator serving 17 months in federalprison. In 2002 a federal appeals court ruled that while theWire Act applied to sports betting, it did not apply to onlinebetting on games of chance. However, subsequent legalambiguity has led major Internet services such as Googleand Yahoo! to remove online gambling advertisementsfrom their sites. Meanwhile, a suit by the Casino City gamblingportal on First Amendment grounds was dismissed,although other legal challenges were underway in 2007.In recent years antigambling activists have adoptedan indirect strategy of going after the infrastructure usedfor gambling transactions. In 2006 Congress passed theUnlawful Internet Gambling Enforcement Act, which prohibitsU.S. credit card companies and banks from transferringfunds to or from Internet gambling sites. (One of thearguments used by proponents was that terrorists might beusing online gambling sites to launder money.)Another issue raised by online gambling opponents isthat the high-speed, highly interactive (click-and-response)nature of online games of chance made it easier for peopleprone to gambling addiction to get and stay “hooked.” Particularconcern has been raised about teens who decide togamble using parents’ credit cards. However, studies suchas the British Gambling Prevalence Survey 2007 have suggestedthat the growing popularity of online gambling hasnot led to an increase in the rate of gambling addiction.On the other hand, congressional liberals such as Rep.Barney Frank (Dem.-Massachusetts) have sponsored legislationthat would legalize (and tax) Internet gambling, andprovide for programs to deal with underage and compul-

online games 347sive gambling. Opponents have charged that the legalizationmeasure is being backed by major “brick and mortar”casinos who want a piece of the online action, as well as thecredit card companies, which would also get a piece of eachtransaction. (As of 2007 neither this nor other attemptsto legalize online gambling in the United States have beenpassed.)Further ReadingDunnington, Angus. Gambling Online. Hassocks, West Sussex,U.K.: D&B Publishing, 2004.Norton, Kate. “Online Gambling Hedges Its U.S. Bets.” BusinessWeek, August 21, 2006. Available online. URL: http://www.businessweek.com/globalbiz/content/aug2006/gb20060821_544446.htm. Accessed October 9, 2007.Somach, Tom. “Gambling Gold Rush? A Congressional PushLast Year Stopped Many Americans from Playing the GamesOnline, but the Law May Be Changed.” San Francisco Chronicle,July 2, 2007, p. C1–2.Vogel, J. Philip. Internet Gambling: How to Win Big Online PlayingBingo, Poker, Slots, Lotto, Sports Betting & Much More. NewYork: Black Dog & Leventhal Publishers, 2006.Woellert, Lorraine. “A Web Gambling Fight Could Harm FreeTrade.” Business Week, August 12, 2007, p. 43. Available online.URL: http://www.businessweek.com/magazine/content/07_33/b4046041.htm. Accessed October 9, 2007.online gamesOnline games today range from elaborate war games toopen-ended fantasy worlds to virtual universes that mirror“real-world” activities, including economics, politics, andeven education.The first online games appeared in the late 1970s onPLATO, an educational network, as well as on the earlyInternet of the 1980s. These MUDs (multiuser dungeons)were generally based on pen-and-paper role-playing gamesof the time, notably Dungeons & Dragons. These games wereSecond Life is not a “game,” but a virtual world that now includesjust about every known human activity—its money is evenexchangeable for real-world cash. (Copyright 2006, LindenResearch Inc., All Rights Reserved)text based, with players typing their characters’ actionsand dialog while the changing world as seen by the playerswas similarly described. By the early 1990s, however,MUDs had spun off many variants. Many were still “hackn’ slash” dungeon games (which were also offered on AmericaOnline and other commercial services). Many of theseMUD-like games such as AOL’s Neverwinter Nights offeredsimple graphics. Meanwhile other games began to offermore sophisticated social interactions as well as the abilityof players to make their own additions to the game world,including buildings.Massively Multiplayer OnlineRole-Playing Games (MMORPGs)Today’s online games feature a “persistent world” hosted onone or more servers that grows and develops from day to dayand in which the “avatars” or representatives of thousandsof players interact with game-generated creatures or oneanother, using client software. Players can spend hundredsof hours helping their characters develop skills, increasingtheir levels through experience points gained from successfulcombat or other activities. Players (and their characters)frequently form organizations such as guilds or clans,because the tougher challenges generally require the cooperationof different types of classes of characters (fighters,healers, and magic-users).Modern mmORPGs began in the late 1990s with suchtitles as Ultima Online and EverQuest. The most popularMMORPG in the mid-2000s was World of Warcraft.From Games to Alternative WorldsHumans are social primates, and they tend to bring theirfull repertoire of behavior to any new situation. Even gamessuch as World of Warcraft or Everquest are not entirely aboutcombat and character skills: they are also about alliance,trust, betrayal, and bonding.Back in the 1980s psychologists began to write aboutthe social interactions that were emerging in MUDs andhow players perceived their virtual world (see Turkle,Sherry). However Second Life, launched by Linden Lab in2003, is not a game at all, but a complete virtual world inwhich participants, called “residents” (through their avatars)can do just about anything—play and be entertained,have relationships (including virtual sex), but also conductmore mundane businesses and meetings and even attenduniversity courses.The ability to do nearly anything also means the abilityto do things that may be offensive and even illegal. Indeed,an emerging issue is how “real world” laws apply to thesevirtual worlds. In Second Life, residents buy and sell inworldreal estate and goods, using a currency called LindenDollars (L$). These L$ and U.S. dollars can be tradedat the rate (as of early 2007) of 270 L$ to one dollar U.S.This means that residents in the virtual world can actuallyrun profitable businesses (or make investments) that can becashed out for “real” money. Further, the avatars, property,and other in-world creations developed by users remaintheir intellectual property, not that of Linden Labs.

348 online investingThe close and growing ties between virtual worlds suchas Second Life and “real” world society raises many legal andeven social issues:• Should income made in the virtual world be taxable?• If residents of a virtual world make contracts with oneanother, are they enforceable? If so, who has jurisdiction?(See cyberlaw.)• Is the virtual world itself subject to national laws,or might it eventually acquire a form of sovereignty?(Already a few nations have “virtual embassies”within Second Life.)Meanwhile, representatives of major companies rangingfrom Microsoft and Google to Second Life’s Linden Labs haveproposed making online identities and avatars “portable” sothat a person could use them in his or her online games andvirtual communities (see virtual community).Further ReadingCastronova, Edward. Synthetic Worlds: The Business and Culture ofOnline Games. Chicago: University of Chicago Press, 2006.Jennings, Scott. Massively Multiplayer Games for Dummies. Hoboken,N.J.: Wiley, 2005.Rice, Robert A., Jr. MMO Evolution. Morrisville, N.C.: Lulu.com,2006.Terdiman, Daniel. “Tech Titans Seek Virtual World Interoperability.”CNet News. October 12, 2007. Available online.URL: http://www.news.com/Tech-titans-seek-virtual-worldinteroperability/2100-1043_3-6213148.html. Accessed October13, 2007.v3image. A Beginner’s Guide to Second Life. Las Vegas, Nev.: Arche-Books, 2007.online investingAs with shoppers, investors have increasingly been attractedto the interactivity and ease of online transactions. In additionto allowing stocks to be bought or sold with just a fewclicks, online brokers (also called discount brokers) chargemuch lower transaction fees than their traditional counterparts,typically less than $10 per trade.Some online brokers, such as E*Trade, Scottrade, andTD Ameritrade, were established as Internet brokers. However,traditional brokerages such as Charles Schwab andWaterhouse have also opened online discount brokerages.In addition to fast, inexpensive trading, many onlinebrokers also offer a variety of resources and tools, includingstock quotes and charts, research reports, and screeningprograms to help investors pick the mutual funds orindividual investments that meet their objectives. For moresophisticated investors, some brokers offer simulations fortesting investment strategies and programmed trading,which will execute buy or sell orders automatically dependingon specified conditions.Online brokers can specialize, seeking customers whowant to make frequent trades but do not need other support,or investors who are interested in obtaining IPOs (initialpublic offerings) of up-and-coming companies. Somebrokers may emphasize mutual funds and cater to retirementaccounts, while others might offer government or corporatebonds, foreign stocks, “penny stocks,” or more exoticinvestments.The interactivity and low transaction costs in onlineinvesting may encourage people to become involved inhighly speculative penny stocks, options, day trading, foreignexchange markets, and other areas that are not suitablefor most individual investors. While there is a great dealof useful information available online, it is a good idea tobegin by discussing investment goals and potential riskswith a trusted financial adviser.TrendsSince trading fees have gone down about as far as theycan go and still allow for profitability, online brokeragesare increasingly competing by offering distinctive featuresand enhanced customer service. In the course of rapidexpansion, service has become somewhat uneven: A 2006J.D. Powers survey found that 41 percent of investors hadencountered at least one problem with accessing theiraccounts or executing a trade.Besides trying to improve reliability, online brokersare also branching out by offering financial planning andother personal services for their larger investors, and someare opening retail outlets where people can actually see abroker.Further ReadingChoosing a Broker. Yahoo! Finance. Available online. URL: http://biz.yahoo.com/edu/ed_broker.html. Accessed October 17,2007.Davidson, Alexander. The Complete Guide to Online Stock MarketInvesting. 2nd ed. Philadelphia: Kogan Page, 2007.Krantz, Matt. Investing Online for Dummies. 6th ed. Hoboken, N.J.:Wiley, 2008.Parmar, Neil. “Finding the Best Broker.” SmartMoney. July 10,2007. Available online. URL: http://www.smartmoney.com/brokers/index.cfm. Accessed October 17, 2007.online job searching and recruitingIn the old days, people found jobs by word of mouth or byreading newspaper classified ads. While word of mouth (orat least e-mail) can still be very useful for finding job leads,increasingly both employers and job seekers are turningfirst to a variety of online sites. (Indeed, as of mid-2007 onelarge site, Monster.com, claimed to have more than 73 millionresumes in its database and 42 million job seekers permonth.)There are a number of large sites that list thousandsof jobs at any given time. Examples include Monster.com,JobCentral, and CareerJournal (from The Wall Street Journal).Meanwhile, many of the “career classifieds” fromnewspapers have been replaced by postings on Craigslist,which has a number of regional sites and covers buy/sell,apartment rentals, and other types of ads as well (seecraigslist).In evaluating a job site it is important to get a feel forthe kinds of jobs offered and the target audience, such asprofessionals, recent graduates, white-collar or service-

online research 349sector jobs, and so on. Other important features to look forinclude:• powerful search or filtering capability, such as by typeof job or employer, keywords in job description, orlocality• the ability to put one’s resume online and edit orupdate it as needed.• the ability to have several versions of one’s resumetailored to different types of jobs• automatic e-mail alerts about newly added jobs thatmeet the user’s criteria• privacy protections so that contact information fromresumes is not used for marketing or other nonemploymentpurposes• lack of fees to job seekers (normally employers are theservice’s source of revenue)Job seekers can use job search engines such as CareerBuilder that will search the major job-finding sites and/oremployers’ own sites according to the user’s criteria.In addition to dedicated job-hunting sites and recruitingagencies, a less formal but rapidly growing trend isthe meeting of employers and would-be employees throughsites such as Facebook (see social networking), wherepeople often freely describe their interests. Employers inturn are increasingly searching online for informationabout applicants, which can cause a problem if the resultsinclude “indiscreet” writings or perhaps photos, perhapsdating back to high school. (On the other hand, there arealso social networks such as LinkedIn that specialize inbusiness contacts.)Finally, online job seekers should beware of fake “joboffers” that ask for information such as social security numbers(see online frauds and scams).Further ReadingCareerBuilder. Available online. URL: http://www.careerbuilder.com. Accessed October 21, 2007.Craigslist. Available online. URL: http://www.craigslist.com.Accessed October 21, 2007.Dikel, Margaret Riley, and Frances E. Roehm. Guide to Internet JobSearching 2006–2007 Edition. New York: McGraw-Hill, 2006.Job-Hunt: The Guide to Finding Employment Online. Availableonline. URL: http://www.job-hunt.org/job-search.html.Accessed October 21, 2007.Kerber, Ross. “Online Job Hunters Grapple with Misuse of PersonalData.” Boston Globe, October 1, 2007. Available online. URL:http://www.boston.com/business/globe/articles/2007/10/01/online_job_hunters_grapple_with_misuse_of_personal_data/. Accessed October 21, 2007.Monster.com. Available online. URL: http://www.monster.com.Accessed October 21, 2007.Napoli, Lisa. “New Job-Seeking Tool? It’s the Network.” Marketplace(American Public Media). October 19, 2007. Availableonline. URL: http://marketplace.publicradio.org/display/web/2007/10/19/online_job_networking. Accessed October21, 2007.USAJOBS [federal job information]. Available online. URL: http://www.usajobs.gov/. Accessed October 21, 2007.online researchThe proliferation of online databases, information services(see online services) and Web sites has made more informationaccessible to more people than ever before. At thesame time, the complexity of the online world challengesresearchers to develop a new set of skills to cope with it.It is useful to divide online offerings into three broadcategories: specialized databases, online information services,and the Web as a whole (see World Wide Web).Each of these areas requires a somewhat different approachby the online researcher.A common research task is to find and evaluate booksor articles on a given subject. Most local libraries have theircatalogs online, and the world’s largest library catalog, thatof the Library of Congress (LC), is also available in severalforms on the Web.Newspaper and magazine articles can be found in anumber of general-purpose databases such as InfoTrac.These databases can be searched in public libraries: Remoteaccess is generally restricted to the library’s cardholders.These records can consist of a bibliographic descriptiononly (that is, author, title, periodical, issue date, and soon) or can include an abstract or in many cases the fulltext of the article. In addition, most major newspapers nowoffer free access to recent articles on their Web site, witholder articles available for a nominal fee. Magazines, too,frequently offer selected articles or their complete contentsonline.Using the search facility for an online catalog or periodicaldatabase is generally simple, particularly if an author ortitle is known. For subject searching, some familiarity withLC subject headings is helpful. However, the ability of mostsystems to search for matching words in titles or subjectsmeans that the researcher can be quickly led to the correctsubject in most cases.Another way to get tables of contents, jacket copy, andreviews of books is to browse the online catalogs of majorbooksellers, particularly Amazon.com and BarnesandNoble.com.Publishers’ Web sites are another good way to getinformation about books, particularly new or forthcomingtitles.Journalists need a broad familiarity with online researchtools and use computers and online services in many facetsof their work (see journalism and computers). Researcherslooking for specialized articles in fields such as law ormedicine need more rigorous skills.Most legal research is done using databases such asLexisNexis. These databases are expensive but indispensableto practitioners. However, students and others whocan’t afford this access can still find U.S. Supreme Court,Court of Appeals, and many state court decisions online,thanks to the efforts of organizations such as the LegalInformation Institute at Cornell Law School. Because ofthe complexity of multiple jurisdictions and the need totrace chains of precedent (“shepardizing”), online legalresearch has become an increasingly important paraprofessionaltask.Medical research is similarly complex, due to thethousands of precise terms for conditions, procedures,

350 online servicesand drugs. The sheer volume of articles (MEDLINE hasmore than 11 million citations dating back to the 1960s)can make it hard to find and evaluate the most relevantmaterial.By far the most extensive information resource todayis the World Wide Web with its millions of sites and pagesof information. There are two basic approaches to findingmaterial on the Web. The first is to use a search engine bytyping in keywords or phrases (see search engine). Eventhough search engines such as Google index only a modestfraction of the available pages on the Web, a searchon a topic such as “database design” can yield from thousandsto millions of possible “hits.” Most search engines doattempt to rank results in decreasing order of matching orrelevance.An alternative approach is to browse the categorized listof topics presented by a site such as Yahoo! (www.yahoo.com) or About.com (www.about.com). The advantage ofthis approach is that the site’s researchers have selected thelinks for each topic that they believe to be the most valuable,and the number of possibilities is likely to be moremanageable (see portal).The tremendous increase in personal expression andcollaboration on the Web is opening new channels of information(see blogs and blogging, user-created content,and wikis and Wikipedia). Wikipedia, for example,has some articles that are as reliable and fully documentedas those found in a traditional encyclopedia, while othersmight be best described as “works in progress.” Theresearcher must decide whether a given article or postingis definitive or perhaps just usefully suggestive of furtherresources.Online research remains more an art than a science. Theresearcher must choose the appropriate tools—bibliographicalresources, specialized databases, information services,search engines, and portals—and evaluate and integratethe results so they are useful for a given question or project.Students and researchers now have unprecedented access toinformation, but sophisticated critical thinking skills mustbe employed. In particular, it can be difficult to evaluate thebackground or credentials of the people behind Web sitesthat are not associated with recognized media outlets orother organizations.Further ReadingDornfest, Rael, Paul Bausch, and Tara Calishain. Google Hacks:Tips and Tools for Finding and Using the World’s Information.3rd ed. Sebastapol, Calif.: O’Reilly, 2006.Hock, Randolph. The Extreme Searcher’s Internet Handbook: AGuide for the Serious Searcher. 2nd ed. Medford, N.J.: InformationToday, 2007.Internet Public Library. Available online. URL: http://www.ipl.org/. Accessed August 16, 2007.Research and Documentation Online. Available online. URL:http://www.dianahacker.com/resdoc/. Accessed August 16,2007.Schlein, Alan M. Find It Online. 4th ed. Tempe, Ariz.: Facts onDemand Press, 2004.Tomaiuolo, Nicholas, Steve Coffman, and Barbara Quint. The WebLibrary: Building a World Class Personal Library with Free WebResources. Medford, N.J.: Information Today, 2004.online servicesThe ability of PC owners to connect to remote computers(see modem) led to the proliferation of both free andcommercial online information services during the 1980s.At one end of the spectrum were bulletin board systems(BBS), many run by hobbyists on PCs connected to a fewphone lines (see bulletin board systems). They offeredusers the ability to read and post messages on various topicsas well as to download or contribute software (see alsoshareware).The growing number of connected PC owners soonoffered entrepreneurs a potential market for a commercialonline information service. One of the oldest, CompuServe,had actually been started in 1969 as a business time-sharingcomputer system. In 1979, it launched a service forhome computer users, offering e-mail and technical supportforums. By the mid-1980s, the service had added anonline chat service called CB Simulator (see chat, online)as well as news content. The service’s greatest strength,however, remained its forums, which offered technicalsupport for just about every sort of computer hardwareor software, together with download libraries containingsystem patches, drivers, utilities, templates, macros, andother add-ons.By then, however, the online service market had becomequite competitive. While CompuServe focused on computer-savvyusers, America Online (AOL), founded in1985 by Steve Case, targeted the growing legion of newPC users who needed an easy-to-navigate interface. AOLgrew steadily, reaching a million customers in 1994 (seeAmerica Online). AOL chat groups became very popular,spawning a vigorous online culture while raising controversiesabout sexual content in some chat “rooms.” A thirdservice, Prodigy, also catered to the new user.Meanwhile, the World Wide Web and the advent ofgraphical Web browsers such as Netscape and MicrosoftInternet Explorer in the mid-1990s led millions of usersto connect to the Internet (see Internet, Web browser,and World Wide Web). Internet service providers (ISPs)offered direct, no-frills access to the Web. CompuServe andAOL soon offered their users access to the Internet as well.However, accessing the Web through an online informationservice was usually more expensive, and often slower, thanusing an ISP and a Web browser directly. Additionally, freeWeb portal services such as Yahoo! began to offer extensiveinformation resources of their own.The Internet thus threatened to shrink the market forthe commercial online services. AOL fought back in the late1990s by cutting its monthly rates to make them competitivewith ISPs, flooding the mails with free disks and trialoffers, bundling introductory packages with new computersystems, and promoting added-value information servicessuch as stock quotes. In 1998, the market consolidatedwhen AOL bought CompuServe, continuing to run the latteras a subsidiary targeted at more sophisticated users.The same year AOL bought Netscape to gain access to itsbrowser technology. Finally, AOL merged with Time-Warner,hoping to leverage the latter’s huge media resources,such as by offering classic TV fare. However, the flagship

ontologies and data models 351online service continued to struggle in the 2000s, essentiallyabandoning the ISP part of its business. MeanwhileCompuServe, after peaking in the 1990s, gradually shrankto a shadow of its former self. Even mighty Microsoft hashad trouble growing its Microsoft Network (MSN), reinventingit in 1999 as a Web portal and then trying to integrateit more closely with its operating system and softwareproducts as “Windows Live” as well as providing servicessuch as instant messaging, blogging, and picture sharing.The long-term prospects for AOL and other commercialonline services are uncertain. Many of the advantagesthese services had until the late 1990s have diminished.For example, the once mutually incompatible e-mail systemsof online services have been replaced by standardInternet e-mail protocols, so there is little advantage tousing a particular service for e-mail. Users can obtaine-mail accounts from a variety of ISPs or through freeWeb-based services such as hotmail.com. Content such asnews, video, and music (see streaming) is available frommany Web sites, and most companies now offer extensiveonline technical support for their products. At thesame time, attempts to support content-rich sites througheither advertising or a subscription model have largelyfoundered. For services such as AOL, the ultimate questionis whether the parts of the service still form a sufficientlycompelling whole.Further ReadingAmerica Online. Available online. URL: http://www.aol.com.Accessed August 16, 2007.Bourne, Charles P. A History of Online Information Services, 1963–1976. Cambridge, Mass.: MIT Press, 2003.Kaufeld, John. AOL for Dummies. Hoboken, N.J.: Wiley, 2004.Microsoft Network. Available online. URL: http://www.msn.com.Accessed August 14, 2007.Swisher, Kara. There Must Be a Pony in Here Somewhere: The AOLTime Warner Debacle. New York: Three Rivers Press, 2004.ontologies and data modelsA persistent problem in artificial intelligence (see artificialintelligence) is how to provide a software systemwith a model that it can use to reason about a particularsubject or domain. A data model or ontology basically consistsof classes to which the relevant objects might belong,relationships between classes, and attributes that objects inthat class can possess. (For implementation of these ideaswithin programming languages, see classes and objectorientedprogramming.)For example, a business ontology might include classessuch as:• Entity—a business or person• Supplier—an Entity that provides wholesale goods orservices• Customer—an Entity that buys the company’s goodsor services• Contractor—an Entity that performs work for thecompany on contractIn the above list it can be seen that the last three classesall include as their parent or “superclass” the class Entity.Another way to put this is to say that the Entity class “subsumes”the last three classes. These relationships can beeasily shown in tree diagrams, with the most general or“universal” class at the top and the more specialized classesextending downward and outward. The process of definingrelated classes and specifying criteria for the inclusion ofan object in a class is called “partitioning.” (Readers familiarwith set theory will also note that the language of sets,subsets, and inclusion also works well with this scheme.)Classes can have other types of relationships. For example,a class can be defined as being “part of” a structurebuilt from several classes. For example, a Customer mightbe part of a Transaction class.Attributes are assigned to classes as appropriate. Notein the example above that when attributes such as contactinformation are defined for the Entity class, they will alsoapply to the descendant classes Supplier, Customer, andContractor.ImplementationOntologies can be used to provide guidance to a variety oftypes of programs (for example, see expert system, naturallanguage processing, and software agent). Thusif an automatic news summarizer program encounters astory that includes references to opposing lawyers and legalissues, it could apply an ontology that defines the likelyrelationship of the participants in the case.Creating useful ontologies is quite labor intensive interms of the human thinking and coding involved. However,there have been substantial efforts in recent years tocreate anthologies for many fields, particularly in biologyand genetics. The Web Ontology Language (OWL) is apopular tool for creating ontologies that can be used tomake Web content more understandable to programs (seesemantic web).Meanwhile, an ambitious and long-running projectcalled Cyc (for Encyclopedia) under the direction of DouglasLenat has been engaged in creating what amounts tovast ontologies for many of the domains included in everydayhuman life as well as specialized fields of knowledge. Alarge portion of this work has been made available as opensource.Further ReadingCYCorp. Available online. URL: http://www.cyc.com/. AccessedOctober 21, 2007.Gasevic, Dragan, Dragan Djuric, and Vladan Devedzic. ModelDriven Architecture and Ontology Development. New York:Springer, 2006.Macy, Lee W. OWL: Representing Information Using the Web OntologyLanguage. Victoria, B.C., Canada: Trafford Publishing,2005.Nigro, Hector Oscar, Sandra Gonzalez Cisaro, and Daniel Xodo,eds. Data Mining with Ontologies: Implementations, Findings,and Frameworks. Hershey, Penn.: Idea Group, 2007.Web Ontology Language (OWL), World Wide Web Consortium.Available online. URL: http://www.w3.org/2004/OWL/.Accessed October 21, 2007.

352 open-source movementopen-source movementFor a long time programmers have released programs asfreeware meaning that users did not have to buy or licensethe software. There is also “try before you buy” software(see shareware). However, while freeware sometimesincludes not only the executable program but the sourcecode (the actual program instructions), most shareware andvirtually all other commercially distributed software doesnot. As a result, users wishing to fix, modify, or extend thesoftware are generally at the mercy of the company thatowns and distributes it.In university and research computing environments,however, it has been common for programmers to freelyshare and extend utilities such as program editors. Indeed,much of the necessary software for the earliest minicomputersof the 1960s was created by clever, energetic hackers (seehackers and hacking). Because the source code (usuallyon paper tape) was freely distributed, people could easilycreate and distribute new (and presumably, improved) versions.Having source code also made it possible to “port”software to a newly released machine without having to waitfor the relatively ponderous efforts of the official developers.In particular, although the licensing of the two majorversions of the UNIX operating system were controlled byAT&T’s Bell Laboratories and the University of California’sBerkeley Software Distribution (BSD) respectively, muchUNIX software including programming languages (see Perland Python) and the Web’s most popular server, Apache,have been distributed using an open source model.The best-known open-source effort is the GNU Projectcreated by Richard Stallman (1953– ). GNU, a recursiveacronym meaning “GNU’s Not UNIX,” is a collection ofsoftware that provides much of the functionality of AT&T’sUNIX without being subject to the latter’s licensing fees andrestrictions. When creating his own open source version ofUNIX (see Linux), Linus Torvalds (see Torvalds, Linus)and his colleagues drew upon the considerable base of softwarealready created by GNU.According to Stallman and many other advocates, “opensource” software is not necessarily free. What is requiredis that users receive the full source code (or have it readilyavailable for free or at nominal charge). Users are free tomodify or expand the source code to create and distributenew versions of the software. Following a legal mechanismthat Stallman calls “copyleft,” the distributor of opensourcesoftware must allow subsequent recipients the samefreedom to revise and redistribute. However, not all softwarethat is billed as open source follows all of Stallman’srequirements, including being copylefted. Formally, opensourcesoftware is generally licensed according to variousversions of the General Public License (GPL). The latestversion, GPL3, released in 2007, has been controversial.Among other things, it more aggressively attempts to preventopen-source software from being restricted or otherwisehampered by being combined with patented softwareor proprietary hardware.Open-source software has the potential for providingdiversity and alternatives in a world where some categoriessuch as PC operating systems and office software aredominated by one or a few large companies. Indeed, sometimescompanies have converted an existing product toopen source, as is the case with Sun Microsystems and StarOffice, a suite that runs under Linux. Netscape also resortedto open source as part of an unsuccessful attempt to fightoff Microsoft for dominance of the browser market in themid to late 1990s. By making a product open source, a companymay hope to tap into the volunteer effort of many talentedprogrammers to improve or expand the program. Thecompany is still free to create proprietary software uponthe “base” of a successful open source product. Moderatelysuccessful companies such as Linux distributor Red Hathave a business plan based upon providing superior packaging,technical support, and customized solutions aroundits Linux distribution.While some critics have questioned whether viable businessmodels can be built directly upon open-source software,there is little doubt that open-source developmenthas made a substantial contribution to the infrastructureof the computer industry. Linux runs about a third of allWeb servers, and products such as the Apache Web serverand MySQL database are also in widespread use, as is theEclipse integrated development environment.Many advocates see open source as part of a larger philosophyand even a social movement (see user-createdcontent). They believe that by creating value through collaborationand sharing, open source may challenge classicaleconomics based on scarcity and competition.Further ReadingBabcock, Charles. “Open Source Software: Who Gives and WhoTakes?” InformationWeek. May 15, 2006. Available online.URL: http://www.informationweek.com/story/showArticle.jhtml?articleID=187202790. Accessed August 16, 2007.DiBona, Chris, Danese Cooper, and Mark Stone, eds. Open Sources2.0: The Continuing Evolution. Sebastapol, Calif.: O’Reilly,2005.DiBona, Chris, Sam Ockman, and Mark Stone, eds. Open Sources:Voices from the Open Source Revolution. Sebastapol, Calif.:O’Reilly, 1999.Enterprise Open Source (EOS) Directory. Available online. URL:http://www.eosdirectory.com/. Accessed August 16, 2007.LaMonica, Martin. “‘Free’ is the New ‘Cheap’ for Software Tools.”CNET News. Available online. URL: http://news.com.com/2100-7344_3-6032986.html. Accessed August 16, 2007.Ohloh Open Source Directory. Available online. URL: http://www.ohloh.net/. Accessed August 16, 2007.Rosen, Lawrence. Open Source Licensing: Software Freedom andIntellectual Property Law. Upper Saddle River, N.J.: PrenticeHall, 2004.Stallman, Richard. “Richard Stallman Sets the Free SoftwareRecord Straight” [interview with Jennifer LeClaire]. LinuxInsider. Available online. URL: http://www.linuxinsider.com/story/50122.html. Accessed August 14, 2007.Weber, Steven. The Success of Open Source. Cambridge, Mass.: HarvardUniversity Press, 2005.operating systemAn operating system is an overarching program that managesthe resources of the computer. It runs programs andprovides them with access to memory (RAM), input/outputdevices, a file system, and other services. It provides applica-

operating system 353tion programmers with a way to invoke system services, andgives users a way to control programs and organize files.DevelopmentThe earliest computers were started with a rudimentary“loader” program that could be used to configure the systemto run the main application program. Gradually, a moresophisticated way to schedule and load programs, link programstogether, and assign system resources to them wasdeveloped (see job control language and mainframe).As systems were developed that could run more thanone program at a time (see multitasking), the duties of theoperating systems became more complex. Programs had tobe assigned individual portions of memory and preventedfrom accidentally overwriting another program’s memoryarea. A technique called virtual memory was developed toenable a disk drive to be treated as an extension of themain memory, with data “swapped” to and from the diskas necessary. This enabled the computer to run more and/or larger applications. The operating system, too, becamelarger, amounting to millions of bytes worth of code.During the 1960s, time sharing became popular particularlyon new smaller machines such as the DEC PDPseries (see minicomputer), allowing multiple users to runprograms and otherwise interact with the same computer.Operating systems such as Multics and its highly successfuloffshoot UNIX developed ways to assign security levelsto files and access levels to users. The UNIX architecturefeatured a relatively small kernel that provides essentialprocess control, memory management, and file system services,while drivers performed the necessary low-level controlof devices and a shell provided user control. (See unix,kernel, device driver, and shell.)Starting in the late 1970s, the development of personalcomputers recapitulated in many ways the earlier evolutionof operating systems in the mainframe world. Earlymicrocomputers had a program loader in read-only memory(ROM) and often rudimentary facilities for entering, running,and debugging assembly language programs.During the 1980s, more complete operating systemsappeared in the form of Apple DOS, CP/M, and MS-DOS forIBM PCs. These operating systems provided such facilitiesas a file system for floppy or hard disk and a command-lineinterface for running programs or system utilities. Thesesystems could run only one program at a time (althoughexploiting a little-known feature of MS-DOS allowed additionalsmall programs to be tucked away in memory).As PC memory increased from 640 kB to multiple megabytes,operating systems became more powerful. Apple’sMacintosh operating system and Microsoft Windows couldmanage multiple tasks. Today personal computer operatingsystems are comparable in sophistication and capability tothose used on mainframes. Indeed, PCs can run UNIX variantssuch as the popular Linux.ComponentsWhile the architecture and features of operating systemsdiffer considerably, there are general functions common toalmost every system. The “core” functions include “booting”the system and initializing devices, process management(loading programs intro memory assigning them a share ofprocessing time), and allowing processes to communicatewith the operating system or one another (see kernel).Multiprogramming systems often implement not only processes(running programs) but also threads, or sections ofcode within programs that can be controlled separately.A memory management scheme is used to organize andaddress memory, handle requests to allocate memory, freeup memory no longer being used, and rearrange memory tomaximize the useful amount (see memory management).There is also a scheme for organizing data created orused by programs into files of various types (see file). Mostoperating systems today have a hierarchical file system thatallows for files to be organized into directories or foldersthat can be further subdivided if necessary. In operatingsystems such as UNIX, other devices such as the keyboardand screen (console) and printer are also treated like files,providing consistency in programming. The ability to redirectinput and output is usually provided. Thus, the outputof a program could be directed to the printer, the console,or both.In connecting devices such as disk drives to applicationprograms, there are often three levels of control. At thetop level, the programmer uses a library function to opena file, write data to the file, and close the file. The libraryitself uses the operating system’s lower-level input/output(I/O) calls to transfer blocks of data. These in turn aretranslated by a driver for the particular device into the lowlevelinstructions needed by the processor that controls thedevice. Thus, the command to write data to a file is ultimatelytranslated into commands for positioning the diskhead and writing the data bytes to disk.A typical operating system processes user commands or actionsusing an interface (such as a shell). Both user commands andrequests from application programs communicate with the operatingsystem through the application Programming Interface (API),which provides services such as file, memory, process, and networkmanagement.

354 operators and expressionsOperating systems, particularly those designed for multipleusers, must also manage and secure user accounts.The administrator (or sometimes, ultimately, the “superuser” or “root”) can assign users varying levels of access toprograms and files. The owners of files can in turn specifywhether and how the files can be read or changed by otherusers (see data security).In today’s highly networked world most operating systemsprovide basic support for networking protocols suchas TCP/IP. Applications can use this facility to establishnetwork connections and transfer data over the local orremote network (see network).The operating system’s functions are made available toprogrammers in the form of program libraries or an applicationprogramming interface (API). (See library, programand application programming interface.)The user can also interact directly with the operatingsystem. This is done through a program called a shell thataccepts and responds to user commands. Operating systemssuch as MS-DOS and early versions of UNIX acceptedonly typed-in text commands. Systems such as MicrosoftWindows and UNIX (through facilities such as XWindows)allow the user to interact with the operating system throughicons, menus, and mouse movements. Application programmerscan also provide these interface facilities through theAPI. This means that programs from different developerscan have a similar “look and feel,” easing the learning curvefor users.Issues and TrendsAs the tasks demanded of an operating system have becomemore complex, designers have debated the best overall formof architecture to use. One popular approach, typified byUNIX, is to use a relatively small kernel for the core functions.A community of programmers can then write theutilities needed to manage the system, performing taskssuch as listing file directories, editing text, or sending e-mail. New releases of the operating system then incorporatethe most useful of these utilities. The user also has a varietyof shells (and thus interfaces) available.The kernel approach makes it relatively easy to port theoperating system to a different computer platform and thendevelop versions of the utilities. (Kernels were also a necessitywhen system memory was limited and precious, butthis consideration is much less important today.)Designers of modern operating systems face a numberof continuing challenges:• security, in a world where nearly all computers arenetworked, often continuously (see computer crimeand security and firewall)• the tradeoff between powerful, attractive functionssuch as scripting and the security vulnerabilities theytend to present• the need to provide support for new applications suchas streaming audio and video (see streaming)• ease of use in installing new devices (see devicedriver and plug and play)• The continuing development of new user-interfaceconcepts, including alternative interfaces for the disabledand for special applications (see user interfaceand disabled persons and computing)• the growing use of multiprocessing and multiprogramming,requiring coordination of processors sharingmemory and communicating with one another (seemultiprocessing and concurrent programming)• distributed systems where server programs, clientprograms, and data objects can be allocated amongmany networked computers, and allocations continuallyadjusted or balanced to reflect demand on thesystem (see distributed computing)• the spread of portable, mobile, and handheld computersand computers embedded in devices such asengine control systems (see laptop computer, PDA,and embedded system). (Sometimes the choice isbetween devising a scaled-down version of an existingoperating system and designing a new OS that isoptimized for devices that may have limited memoryand storage capacity.)Further ReadingBach, Maurice J. The Design of the UNIX Operating System. EnglewoodCliffs, N.J.: Prentice Hall, 1986.Ritchie, Dennis M. “The Evolution of the UNIX Time-Sharing System.”Lecture Notes in Computer Science #79: Language Designand Programming Methodology, New York: Springer-Verlag,1980. Available online. URL: http://cm.bell-labs.com/cm/cs/who/dmr/hist.html. Accessed August 14, 2007.Silberschatz, Abraham, Peter Baer Galvin, and Greg Gagne. OperatingSystem Concepts. 7th ed. New York: Wiley, 2004.operators and expressionsAll programming languages provide operators to specifyarithmetic functions. Some of them, such as addition +,subtraction -, multiplication ×, and division ÷, are familiarfrom elementary school arithmetic (although the asteriskrather than the traditional x is used for multiplication inprogram code, to avoid confusion with the letter x). Additionaloperators found in languages such as C, C++, andJava include % (modulus, or remainder after division), ++(adds one and stores the result back into the operand), and-- (decrement; subtracts one and stores the result back intothe operand).Operands are data items such as variables, constants, orliterals (actual numbers) that are operated on by the operator.An operator is called unary if it takes just one operand(the increment operator ++ is an example). An operator thattakes two operands is considered to be binary, and this istrue of most arithmetic operations such as addition, multiplication,subtraction, and division.A combination of operands and operators constitutes anarithmetic expression that evaluates to a particular valuewhen the program runs. Thus in the C statement:Total = SubTotal + SubTotal Tax × Tax_Rate;

optical character recognition 355the value of the SubTotal Tax is multiplied by the value ofthe variable Tax_Rate, the result is added to the value ofSubTotal, and the result of the entire expression is storedin the variable Total. Compilers generally parse arithmeticexpressions by converting them from an “infix” form (as inA + B) to a “postfix” form (as in + A B), resolving them intoa simple form that is ready for conversion to machine code.Operator PrecedenceThe preceding example raises an important question. Howdoes one know that the subtotal is to be multiplied by thetax rate and then the result added to the subtotal, as opposedto adding the subtotal and tax and multiplying the result bythe tax rate? The former procedure is intuitively correct tohuman observers, but since computers lack intuition, specificrules of precedence are defined for operators. Theserules, which are similar for all computer languages, tell thecompiler that when code is generated for arithmetic operations,multiplications and divisions are carried out first(moving from left to right), and then additions and subtractionsare resolved in the same way. The rules of precedencedo become more complex when the relational, logical, andassignment operators are included. Finally, expressions canbe enclosed in parentheses to overrule precedence and forcethem to be evaluated. Thus in the expression (A + B) * C theaddition will be carried out before the multiplication.Generally speaking, the levels of precedence for mostlanguages are as follows:1. scope resolution operators (specify local v. globalversions of a variable)2. invoking a method from a class, array subscript,function call, increment or decrement3. size of (gets number of bytes in an object), addressand pointer dereference, other unary operators(such as “not” and complement); creation and deallocationfunctions; type castsA compiler or interpreter processes a program statement by applyingits operators in order of precedence. Here the multiplication isdone first, and then its result is used in the addition. The assignment(=) operator has the lowest precedence and is applied last,assigning the value of the entire expression to the variable Total.4. class member selection through a pointer5. multiplication, division, and modulus6. addition and subtraction7. left and right shift operators8. less than and greater than9. equal and not equal operators10. bitwise operators (AND, then exclusive OR, inclusiveOR)11. logical operators (AND, then OR)12. assignment statementsThe basic arithmetic operators are built into each programminglanguage, but many of the newer object-orientedlanguages such as C++ allow for programmer-defined operatorsand a process called overloading in which the sameoperator can be defined to work with several different kindsof data. Thus the + operator can be extended so that if it isgiven character strings instead of numbers, it will “add” thestrings by combining (concatenating) them.Further Reading“Operators in C and C++.” Wikipedia. Available online. URL:http://en.wikipedia.org/wiki/Operators_in_C_and_C++.Accessed August 16, 2007.Sebesta, Robert W. Concepts of Programming Languages. 8th ed.Upper Saddle River, N.J.: Addison-Wesley, 2007.Stroustrup, Bjarne C. The C++ Programming Language. 3rd ed.Reading, Mass.: Addison-Wesley, 1997. See chap. 6 “Expressionsand Statements” and chap. 11 “Operator Overloading.”“Summary of Operators.” Java Tutorials. Available online. URL:http://java.sun.com/docs/books/tutorial/java/nutsandbolts/opsummary.html. Accessed August 16, 2007.“Summary of Operators in Java.” Available online. URL: http://sunsite.ccu.edu.tw/java/tutorial/java/nutsandbolts/opsummary.html.optical character recognition (OCR)Today it is easy to optically scan text or graphics printed onpages and convert it into a graphical representation for storagein the computer (see scanner). However, a shape suchas a letter c doesn’t mean anything in particular as a graphic.Optical character recognition (OCR) is the process of identifyingthe letter or other document element that correspondsto a given part of the scanned image and converting it tothe appropriate character (see characters and strings). Ifthe process is successful, the result is a text document thatcan be manipulated in a word processor, database, or otherprogram that handles text. Raymond Kurzweil (1948– )marketed the first commercially practicable general-purposeoptical character recognition system in 1978.Once the document page has been scanned into an imageformat, there are various ways to identify the characters.One method is to use stored templates that indicate the patternof pixels that should correspond to each character. Generally,a threshold of similarity is defined so that an exactmatch is not necessary to classify a character: The templatemost similar to the character is chosen. Some systems storea set of templates for each of the fonts most commonly foundin printed text. (Recognizing cursive writing is a much morecomplex process: See handwriting recognition.)

356 optical computingA more generalized method uses structural features(such as “all t’s have a single vertical line and a shortercrossbar line”) to classify characters. To analyze a character,the different types of individual features are identified andthen compared to a set of rules to determine the charactercorresponding to that particular combination of features.Sometimes thresholds or “fuzzy logic” are used to decidethe probable identity of a character.OCR systems have improved considerably, the processalso being speeded up by today’s faster processors. Mostscanners are sold with OCR software that is perhaps 95percent accurate, with higher end systems being more accuratestill. This is certainly good enough for many purposes,although material that is to be published or used in legaldocuments should still be proofread by human beings.Further ReadingMore, Shunji, Hirobumi Nishida, and Hiromitsu Yamada, eds.Optical Character Recognition. New York: Wiley, 1999.Rice, S. V., G. Nagy and T. A. Nartker. Optical Character Recognition:An Illustrated Guide to the Frontier. Boston: Kluwer,1999.optical computingLight is the fastest thing in the universe, and the scienceand technology of optics have developed greatly since theinvention of the laser in the 1960s. It is not surprising,therefore, that computer designers have explored the possibilityof using optics rather than electronics for computationand data storage.An early idea was to use a grid of laser beams to createlogical circuits, exploiting the ability of one laser to be usedto “quench” or switch off another one. However, creating alarge number of tiny laser beams proved impracticable, asdid managing the heat created by the process. However, bythe 1980s, experimenters were interacting “microlasers” withsemiconductors, exploiting quantum effects. This broughtthe energy (and heat) problem under control while vastlyincreasing the potential density of the optical circuitry.The incredible rate at which conventional silicon-basedelectronic circuitry continued to increase in density andcapacity has limited the incentive to invest in the largescaleresearch and development that would be needed todevelop a complete optical computer with processor and acorresponding optical memory technology.Instead, current research is exploring the possibility ofcombining the best features of the optical and electronicsystem. Silicon chips have a limited surface for connectingdata inputs, while light can carry many more channels ofdata through micro-optics. It may be possible to couple amicro-optic array to the surface of the silicon chip in sucha way that the chip could have the equivalent of thousandsof connecting pins to transmit data. In March 2007 IBMunveiled a prototype hybrid chip that combines optical andsemiconductor technology to achieve eight times the datatransfer rate of conventional technologies.The value of optics is more conclusively demonstratedin data transmission and storage technology. Fiber opticcables are being used in many cases to carry large quantitiesof data with very high capacity (see fiber optics) andmay gradually supplant conventional network cable in moreapplications. The use of lasers to store and read informationis seen in CD-ROM and DVD-ROM technology, whichhas replaced the floppy disk as the ubiquitous carrier ofsoftware and handy backup medium (see cd-Rom andDVD-ROM).Further ReadingGoswami, Debabrata. “Optical Computing.” Resonance, June2003. Available online. URL: http://www.ias.ac.in/resonance/June2003/pdf/June2003p56-71.pdf. Accessed August 16, 2007.Knight, Will. “Laser Chips Could Power Petaflop Computers.”New Scientist.com. March 21, 2006. Available online. URL:http://www.newscientist.com/article.ns?id=dn8876. AccessedAugust 16, 2007.“Now, Just a Blinkin’ Picosecond!: NASA Scientists Are Workingto Solve the Need for Computer Speed Using Light Itself toAccelerate Calculations and Increase Data Bandwidth.” Science& NASA. Available online. URL: http://science.nasa.gov/headlines/y2000/ast28apr_1m.htm. Accessed August 16,2007.Saleh, Bahaa E. A., and Malvin Carl Teich. Fundamentals of Photonics.2nd ed. New York: Wiley Interscience, 2007.Oracle CorporationFounded in 1977, Oracle Corporation (NASDAQ symbol:ORCL) is a leading developer of business database software(see database management system) as well as systemsfor other enterprise operations (see customer relationshipmanagement and supply chain management). Thesefunctions are integrated through a structure called OracleInformation Architecture that can coordinate the operationsof servers and storage systems (see grid computing).Besides selling software, a major part of Oracle’s businessis providing consulting and support for fitting the softwareto the needs of corporate customers, as well as training(through Oracle University) and distributed application services(Oracle on Demand). In 2007 Oracle had $18 billionin sales, netting $4.74 billion in profit. The company hadover 73,000 employees.Since its founding, Oracle’s CEO has been the dynamicthough often controversial Larry Ellison, who recognizedthe importance of relational databases (with their ability toconnect information from many sources) as a way to meetthe growing information needs of modern business. In the1970s IBM was the dominant leader in relational databasesfor mainframe computers, but when personal computersrunning Windows became prevalent around 1990, IBM wasslow to enter the new market. Ellison and competitors suchas Sybase and Informix were able to carve out strong niches,with Oracle coming out on top by the end of the decade.(However, by the 2000s IBM’s DB2 for UNIX/Linux andWindows and Microsoft SQL Server [for Windows only]were strong competitors, with open-source products MySQLand PostgreSQL also gaining attention—see SQL.)In recent years Oracle has also expanded through acquisition,picking up other software companies, including PeopleSoft;Retek, Inc.; and Siebel Systems, for a combined totalof over $16 billion. In 2007 Oracle filed a lawsuit against its

OS X 357major competitor in business management applications (seesap), charging them with unfair practices.Further ReadingAllen, Christopher, Simon Chatwin, and Catherine A. Creary.Introduction to Relational Databases and SQL Programming.Burr Bridge, Ill.: McGraw-Hill Technology Education, 2004.Gerald, Bastin, Nigel King, and Dan Natcher. Oracle E-BusinessSuite Manufacturing & Supply Chain Management. Berkeley,Calif.: McGraw-Hill/Osborne, 2002.Oracle Corporation. Available online. URL: http://www.oracle.com/index.html. Accessed October 25, 2007.Rittman, Mark. “Oracle Information Architecture Explained.”Available online. URL: http://www.dba-oracle.com/oracle_news/2004_8_11_rittman.htm. Accessed October 25, 2007.Stackowiak, Robert, Joseph Rayman, and Rick Greenwald. OracleData Warehousing and Business Intelligence Solutions. Indianapolis:Wiley, 2007.Symonds, Matthew. Softwar: An Intimate Portrait of Larry Ellisonand Oracle. New York: Simon & Schuster, 2003.OS XJaguar, panther, tiger, and leopard—these and other namesof sleek big cats represent versions of Apple’s Macintoshoperating system, OS X (pronounced “OS 10”—see AppleCorporation and Macintosh). Unlike the previous MacOS, OS X, while broadly maintaining Apple’s user interfacestyle (see user interface), is based on a version of UNIXcalled OpenStep, developed by NeXT starting in the 1980s(see UNIX). OS X development began when Steve Jobsreturned as Apple CEO in 1997 (see Jobs, Steven Paul)and the company bought NeXT, acquiring the software. Thefirst version, OS X 10.0, or Cheetah, was released in 2001,but the system was not widely used until 10.1 (Puma) wasreleased later the same year.At the core of OS X is a free and open-source version ofUNIX called “Darwin,” with a kernel called XNU. On top ofthis Apple built a distinctive and subtly colorful user interfacecalled Aqua and a new version of the Macintosh Finderfile and program management system.Applications and DevelopmentToday OS X includes a variety of useful software packages—some free and some optional. These include iLife (digitalmedia management), iWork (productivity), and Front Row(home media center). OS X10.5 also includes Time Machine,an automatic backup system that can restore files (includingdeleted files) as well as earlier system settings.For software developers, OS X provides an integrateddevelopment environment called “Xcode,” which workswith modified open-source compilers for major programminglanguages, including C, C++, and Java. Further,because OS X is UNIX-based, many UNIX and Linux programscan be recompiled to run on it. Since mid-2005 Apple(and OS X) have been transitioning from the earlier IBM/Motorola processors to Intel processors. This transition waslargely complete by 2007, though OS X 10.5 (Leopard) stillprovides support for applications written for the PowerPC.OS X has been well received by critics, and together withits bundled software has made the Macintosh a popularplatform for users who want a seamless computing experience,particularly with regard to graphics and media.Further ReadingLeVitus, Bob. Mac OS X Leopard for Dummies. Hoboken, N.J.:Wiley, 2007.Mingis, Ken, and Michael DeAgonia. “In Depth: Apple’s LeopardLeaps to New Heights.” Computerworld, October 25, 2007.Available online. URL: http://www.computerworld.com/action/article.do?command=viewArticleBasic&articleId=9043838. Accessed October 26, 2007.Pogue, David. Mac OS X Leopard: The Missing Manual. Sebastapol,Calif.: Pogue Press/O’Reilly, 2007.Singh, Amit. “A History of Apple’s Operating Systems.” Availableonline. URL: http://www.kernelthread.com/mac/oshistory/.Accessed October 26, 2007.———. Mac OS X Internals: A Systems Approach. Upper SaddleRiver, N.J.: Addison-Wesley Professional, 2006.

PPage, Larry(1973– )AmericanEntrepreneurTogether with business partner Sergey Brin, Larry (LawrenceEdward) Page revolutionized the role of Web searchin the modern Internet economy by developing the Googlesearch engine and building an industry-leading companyaround it.Page was born in East Lansing, Michigan, into a verycomputer-oriented family (both his parents were computerscientists and his brother became a computer engineer).It was perhaps not surprising that Page received a BSE inengineering at the University of Michigan in 1995, thenentered the doctoral program in computer science at StanfordUniversity. There he met Sergey Brin (see Brin, Sergey).The two students soon developed an interest in theburgeoning Web, particularly in finding a better way tosearch for information. The result was their collaborationon a page-ranking system that prioritized search resultsbased on the popularity of sites as shown by the number oflinks to them (see also search engine). The other half ofPage and Brin’s achievement was in developing advertisingmodels that would turn users’ Web interests into revenue.Their key insight was that sellers would be eager to advertiseto people who had already shown by searching thatthey were interested in particular products or services.By the early 2000s Google dominated Web search, whichwould became a springboard to many other services, includinglocal searching, maps, and even free online office applications(see Google). In 2004 Page and Brin became richwhen Google offered its stock to the public (by 2006 Page’snet worth was estimated at $16.6 billion, just behind Brin).Google has profoundly changed the way people use theWeb, so much that “to google” has become a verb for searchingonline. However, the company’s size and dominant positionin Web search advertising has raised concerns amongsome critics that Google might be gaining too much controlover the market (see online advertising). Meanwhile in2001 Page and Brin hired Eric Schmidt to become Google’sCEO, giving Page more time to pursue other interests. oneof which is his investment in Tesla Motors, developer ofan advanced electric vehicle that can go up to 250 mileson one battery charge. Another interest of Page and Brin isspurring the private development of space travel, such asthrough Google’s Lunar X Prize, announced in September2007. It would award $20 million to the first team to landand successfully operate a lunar surface rover.Page’s impact on the Internet economy has been widelyrecognized. In 2004 he was inducted into the NationalAcademy of Engineering for his work in developing theGoogle search engine. In 2005 Time included Page in itslist of the world’s 100 most influential people, and in 2007PC World placed him at number one on a list of the mostimportant people on the Web.Further ReadingBattelle, John. The Search: How Google and Its Rivals Rewrote theRules of Business and Transformed Our Culture. New York:Portfolio, 2006.358

Papert, Seymour 359Carr, David F. “Brin, Page Show No Signs of Slowing Down.”eWeek.com. March 15, 2007. Available online. URL: http://www.eweek.com/article2/0,1895,2104091,00.asp. AccessedOctober 27, 2007.Google. Available online. URL: http://www.google.com. AccessedOctober 27, 2007.Papert, Seymour(1928– )South African/AmericanComputer ScientistSeymour Papert is an artificial intelligence pioneer andinnovative educator who has brought computer science to awider audience, especially young people.Papert was born in Pretoria, South Africa, on March 1,1928. He attended the University of Witwatersrand, earninghis bachelor’s degree in mathematics in 1949 and Ph.D.in 1952. As a student he became active in the movementagainst the racial apartheid system, which was becomingentrenched in South African society. His unwillingness toaccept the established order and his willingness to be anoutspoken activist would serve him well later when he tookon the challenge of educational reform.Papert went to Cambridge University in England andearned another Ph.D. in 1952, then did mathematicsresearch from 1954 to 1958. During this period artificialintelligence, or AI, was taking shape as researchers beganto explore the possibilities for using increasingly powerfulcomputers to create or at least simulate intelligent behavior.In particular, Papert worked closely with another AIpioneer in studying neural networks and perceptrons (seeMinsky, Marvin). These devices made electronic connectionsmuch like those between the neurons in the humanSeymour Papert has made it his life work to create computerfacilities (such as the Logo language) that reflect the psychologyof learning and enable even young students to experiment with“powerful ideas.” (Bill Pierce / Time Life Pictures / GettyImages)brain. By starting with random connections and reinforcingappropriate ones, a computer could actually learn a task(such as solving a maze) without being programmed withinstructions.Papert’s and Minsky’s research acknowledged the valueof this achievement, but in their 1969 book Perceptrons theyalso suggested that this approach had limitations, and thatresearchers needed to focus not just on the workings ofbrain connections but upon how information is actuallyperceived and organized.This focus on cognitive psychology came together withPapert’s growing interest in the process by which humanbeings assimilated mathematical and other concepts. From1958 to 1963 he worked with Jean Piaget, a Swiss psychologistand educator. Piaget had developed a theory of learningthat was quite different from that held by most educators.Traditional educational theory tended to view children asbeing incomplete adults who needed to be “filled up” withinformation.Piaget, however, observed that children did not thinklike defective adults. Rather, children at each stage of developmenthad characteristic forms of reasoning that madeperfect sense in terms of the tasks at hand. Piaget believedthat children best developed their reasoning skills by beingallowed to exercise them freely and learn from their mistakes,thus progressing naturally.In the early 1960s Papert went to the MassachusettsInstitute of Technology, where he cofounded the MIT ArtificialIntelligence Laboratory with Minsky in 1965. He alsobegan working with children and developing computer systemsbetter suited for allowing them to explore mathematicalideas.The tool that he created to enable this exploration wasthe LOGO computer language (see Logo). Logo provideda visual, graphical environment at a time when most programmingresulted in long, hard-to-read printouts. At thecenter of the Logo environment is the “turtle,” which can beeither a screen cursor or an actual little robot that can movearound on the floor, tracing patterns on paper. Young studentscan give the turtle simple instructions such as FOR-WARD 50 or RIGHT 100 and draw everything from squaresto complicated spirals. As students continued to work withthe system, they could build more complicated programs bywriting and combining simple procedures. As they work,the students are exploring and grasping key ideas such asrepetition and recursion (the ability of a program to callitself repeatedly).In creating Logo, Papert believed that he had demonstratedthat “ordinary” students could indeed understandthe principles of computer science and explore the widervistas of mathematics. But when he saw how schools weremainly using computers for rote learning, he began to speakout more about problems with the education system. Buildingon Piaget’s work, Papert called for a different approach.Papert often makes a distinction between “instructivism,”or the imparting of information to students, and “constructivism,”or a student learning by doing.Papert “retired” from MIT in 1998, but remains veryactive, as can be seen from the many Web sites that describe

360 parallel porthis work. Papert lives in Blue-Hill, Maine, where he teachesat the University of Maine. He has also established theLearning Barn, a laboratory for exploring innovative ideasin education. Papert has worked on ballot initiatives tohave states provide computers for all their students, as wellas working with teenagers in juvenile detention facilities.Today, educational centers using Logo and other ideas fromPapert can be found around the world.In December 2006, while attending a conference inHanoi, Papert was struck by a motorcycle and suffered seriousbrain injuries. As of 2008 his rehabilitation is progressingwell.Papert has received numerous awards including a Guggenheimfellowship (1980), Marconi International fellowship(1981), the Software Publishers Association LifetimeAchievement Award (1994), and the Computerworld SmithsonianAward (1997).Further ReadingAbelson, Harold, and Andrea DiSessa. Turtle Geometry: The Computeras a Medium for Exploring Mathematics. Cambridge,Mass.: MIT Press, 1981.Harvey, Brian. Computer Science Logo Style. (3 vols.) 2nd ed. Cambridge,Mass.: MIT Press, 1997.Papert, Seymour. The Children’s Machine: Rethinking School in theAge of the Computer. New York: Basic Books, 1993.———. The Connected Family: Bridging the Digital Generation Gap.Marietta, Ga.: Longstreet Press, 1996.———. Mindstorms: Children, Computers and Powerful Ideas. 2nded. New York: Basic Books, 1993.“Seymour Papert.” Available online. URL: http://www.papert.org/.Accessed May 6, 2007.parallel portThere are two basic ways to send data from a computer toa peripheral device such as a printer. A single wire can beused to carry the data one bit at a time (see serial port), ormultiple parallel wires can be used to send the bits of a dataword or byte simultaneously.Serial ports have the advantage of needing only one line(wire), but sending a byte (eight-bit word) requires waitingfor each of the eight bits to arrive in succession at the destination.With a parallel connection, however, the eight bitsof the byte are sent simultaneously, each along its own wire,so parallel ports are generally faster than serial ports. Also,since the data is transmitted simultaneously, the protocolfor marking the beginning and end of each data byte is simpler.On the other hand, parallel cables are more expensive(since they contain more wires) and are generally limitedto a length of 10 feet or so because of electrical interferencebetween the parallel wires.The original parallel interface for personal computerswas designed by Centronics, and a later version of this 36-pin connector remains popular today. Later, IBM designed a25-pin version. In addition to the wires carrying data, additionalwires are used to carry control signals.Most modern parallel ports use two more advancedinterfaces, EPP (Enhanced Parallel Port) or ECP (ExtendedCapabilities Port). Besides allowing for data transmissionup to 10 times faster than the original parallel port, theseenhanced ports allow for bi-directional (two-way) communications.This means that a printer can send signals backto the PC indicating that it is low on toner, for example.Printer control software running on the PC can thereforedisplay more information about the status of the printerand the progress of the printing job. Besides printers, theparallel interface has also been used to connect externalCD-ROM and other storage devices.Although early PCs often provided their parallel portconnectors on plug-in expansion cards, most PCs todayhave two parallel connectors built into the motherboard.In recent years the faster and more flexible Universal SerialBus (see USB) interface has increasingly replaced the parallelport for printers, scanners, digital cameras, externalstorage drives, and many other devices.Further ReadingParallel Port Central. Available online. URL: http://www.lvr.com/parport.htm. Accessed August 17, 2007.“Parallel Port Configuration.” Available online. URL: http://www.geocities.com/nozomsite/parallel.htm. Accessed August 17,2007.Tyson, Jeff. “How Parallel Ports Work.” Available online. URL:http://computer.howstuffworks.com/parallel-port.htm.Accessed August 17, 2007.parsingJust as a speaker or reader of English must be able to recognizethe significance of words, phrases, and other componentsof sentences, a computer program must be ableto “understand” the statements, commands, or other inputthat it is called upon to process.For example, an interpreter for the BASIC language mustbe able to recognize thatPRINT “End of Run”contains a previously defined command or keyword(PRINT) and that the quote marks enclose a string of charactersthat are to be interpreted literally rather than standingfor something else. Once the type of element or dataitem is recognized, then the appropriate procedure can becalled upon for processing it. (See compiler and interpreter.)Similarly, a command processor (see shell) for an operatingsystem such as UNIX will look at a line of input suchasls -l /bin/MyProgsand recognize that ls is an executable utility program. Itwill pass the rest of the command line to the ls program,which is then executed. In turn, ls must parse its commandline and recognize that -l is a particular option that controlshow the directory listing is displayed, and /bin/MyProgs isa pathname that specifies a particular directory location inthe file system.To parse its input, the language or command interpreterbegins by looking in the program language or commandstatement for tokens. (This process is called lexical analy-

parsing 361sis.) A token is normally defined as a series of one or morecharacters separated by “whitespace” (blanks, carriagereturns, and so on). A token is thus analogous to a word inEnglish.The series of tokens is then sent to the parser. The parser’sjob is to identify the significance of each token and togroup the tokens into properly formed statements. Generally,the parser first checks the tokens for keywords—wordssuch as “if” or “loop” that have a special meaning in aparticular programming language. (In the BASIC example,PRINT is a keyword: In many other languages such functionsare external rather than being part of the languageitself.) As keywords (and punctuation symbols such as thesemicolon used at the end of statements in C and Pascal)are identified, the parser uses a set of rules to determine theoverall structure of the statement. For example, a languagemight define an if statement as follows:If then else This means that when the parser encounters an “if” it willexpect to find between that word and “then” an expressionthat can be tested for being true or false (see Booleanoperators). Following “then,” it will expect to find a completestatement. If it finds the optional keyword “else,” thatword will be followed by an alternative statement. Thus inthe statementIf Total > Limit Print “Overflow” else PrintTotalThe elements would be broken down as follows:IfTotal > LimitPrint“Overflow”elsePrintTotalkeywordBoolean expressionkeywordString literal (charactersto be printed)keywordkeywordvariableWhen writing a parser, the programmer depends ona precise and exhaustive description of the possible legalconstructs in the language (see also Backus-Naur form).In turn, these rules are turned into procedures by whichthe parser can construct a representation of the relationshipsbetween the tokens. This representation is often representedas an upside-down tree, rather like the sentencediagrams used in English class.In general form, an expression, for example, can be diagrammedas consisting of one or more terms (variables,constants, or literal values) or other expressions separatedby operators.A parse tree for the statement A = B + C × D. Notice how theexpression on the right-hand side of the equals (assignment) sign iseventually parsed into the component identifiers and operators.Notice that these diagrams are often recursive. That is,the definition of an expression can include expressions.The number of levels that can be “nested” is usually limitedby the compiler if not by the definition of the language.The underlying rules must be constructed in such a waythat they are not ambiguous. That is, any given string oftokens must result in one, and only one parse tree.Once the elements have been extracted and classified,a compiler must also analyze the nonkeyword tokens tomake sure they represent valid data types, any variableshave been previously defined, and the language’s namingconventions have been followed (see compiler).Fortunately, people who are designing command processors,scripting languages, and other applications requiringparsers need not work from scratch. Tools such as YACC (agrammar definition compiler) and BISON and ANTLR (parsergenerators) are available for UNIX and other platforms.Further ReadingAho, Alfred V., et al. Compilers: Principles, Techniques, & Tools. 2nded. Boston: Pearson/Addison-Wesley, 2007.Bowen, Jonathan P., and Peter T. Breuer. “Razor: The Cutting Edgeof Parser Technology.” Oxford University Computing Laboratory.Available online. URL: http://www.jpbowen.com/pub/toulouse92.pdf. Accessed August 17, 2007.Donnelly, Charles, and Richard M. Stallman. Bison Manual: Usingthe YACC-Compatible Parser Generator. Boston, Mass.: GNUPress, 2003.

362 PascalLevine, John R., Tony Mason, and Doug Brown. lex & yacc. Sebastapol,Calif.: O’Reilly, 1995.Louden, Kenneth C. Compiler Construction: Principles and Practice.Boston: PWS Publishing, 1997.Metsker, Steven John. Building Parsers with Java. Boston: Pearson/Addison-Wesley, 2001.PascalBy the early 1960s, computer scientists had become increasinglyconcerned with finding ways to better organize orstructure programs. Indeed, one language (see Algol) hadalready been developed in part to demonstrate and encouragesound programming practices, including the proper useof control structures (see loop and structured programming).However, Algol lacked a full range of data typesand other features needed for practical programming, whilearguably being too complex and inconsistent to serve as agood teaching language.Niklaus Wirth at ETH (the Swiss Federal Institute ofTechnology) worked during the mid-1960s with a committeethat was trying to overcome the problems with Algoland make the language more practical and attractive tocomputer manufacturers and users. However, Wirth graduallybecame disillusioned with the committee’s unwieldyresults, and proceeded to develop a new language, Pascal,announcing its specifications in 1970.Pascal both streamlined Algol and extended it. Besidesproviding support for character, Boolean, and set data types,Pascal allows users to define new data types by combiningthe built-in types. This feature is particularly useful fordefining a “record” type that, for example, might combinean employee’s name and job title (characters), ID number (along integer), and salary (a floating-point number). The rigoroususe of data types also extends to the way proceduresare called and defined (see procedures and functions).Pascal attracted much interest among computer scientistsand educators by providing a well-defined languagein which algorithms could be expressed succinctly. Theacceptance of Pascal was also aided by its innovative compilerdesign. Unlike the machine-specific compilers of thetime, the Pascal compiler did not directly create machinecode. Rather, its output was “P-code,” a sort of abstractmachine language (see also pseudocode). A run-time systemwritten for each computer interprets the P-Code andexecutes the appropriate machine instructions. This meantthat Pascal compilers could be “ported” to a particularmodel of computer simply by writing a P-Code Interpreterfor that machine. This strategy would be used more thantwo decades later by the creators of a popular language forWeb applications (see Java).Structure of a Pascal ProgramThe following simple program illustrates the basic structureof a program in Pascal. (The words in bold type are keywordsused to structure the program.) The program beginswith a Type section that declares user-defined data types.These can include arrays, sets, and records (composite typesthat can include several different basic types of data). Herean array of up to 10 integers (whole numbers) is defined as atype called IntList.The Var (variable) section then declares specific variablesto be used by the program. Variables can be definedusing either the language’s built-in types (such as integer)or types previously defined in the Type section. An importantcharacteristic of Pascal is that user-defined types mustbe defined before they can be used in variable declarations,and variables in turn must be declared before they can beused in the program. Some programmers found this strictnessto be confining, but it guards against, for example, atypographical error introducing an undefined variable inplace of the one intended. Today most languages enforcethe declaration of variables before use.The word begin introduces the executable part of theprogram. The variables needed for the loop are first initializedby assigning them a value of zero. Note that in Pascal :=(colon and equals sign) is used to assign values. The outer ifstatement is used to ensure that the user does not input aninvalid number of items. The for loop then reads each inputvalue, assigns it to its place in the array, and keeps a runningtotal. That total is then used to compute the average,which is output by the writeln (write line) statement.program FindAvg (input, output);type IntList = array [1 . . 10] of integer;varInts: IntList;Items, Count, Total, Average: integer;beginAverage := 0;Total := 0;Readln (Items);If ((Items > 0) and (Items

pattern recognition 363Turbo Pascal. This compiler used direct compilation ratherthan P-Code, sacrificing portability for speed and efficiency.It included an integrated programming environment thatmade development much cheaper and easier than withexisting “bulky” and expensive compilers such as thosefrom Microsoft. Turbo became very popular and eventuallyincluded language extensions that supported objectorientedprogramming. But Pascal became best known inits role as a first language for teaching programming and forexpressing algorithms.However, by 1990 the tide had clearly turned in favorof C and C++. These languages used a more cryptic syntaxthan Pascal and lacked the latter’s rigorous data typingmechanism. Systems programmers in particular preferredC’s ability to get “close to the machine” and manipulatememory directly without being confined by type definitions.C had also received a big boost because its developerswere also among the key developers of UNIX, a very popularoperating system in campus computing environments.During the 1990s, C, C++, and Java even began to supplantPascal for computer science instruction. Nevertheless,by encouraging structured programming concepts and helpingeducate a generation of computer scientists, Pascal madea lasting impact on the computer field. Wirth continued hiswork with the development of Modula-2 and Oberon, whichwere confined mainly to the academic world. However, Pascalalso was a major influence on the development of Ada, alanguage endorsed by the U.S. federal government that combinesstructured programming with object-oriented featuresand the ability to manage extensive packages of routines(see Ada).Further ReadingFree Online Pascal and Delphi Tutorials and Documentation.Available online. URL: http://www.thefreecountry.com/documentation/onlinepascal.shtml. Accessed August 17, 2007.Free Pascal Compiler. http://www.freepascal.org/Jensen, Kathleen, Niklaus Wirth, and A. Mickel. Pascal UserManual and Report: ISO Pascal Standard. 4th ed. New York:Springer-Verlag, 1991.Koffman, Elliot B. Turbo Pascal. 5th update ed. Reading, Mass.:Addison-Wesley, 1997.Rachele, Warren. Learn Object Pascal with Delphi. Plano, Tex.:Wordware Publishing, 2000.Wirth, Niklaus. Programming in Modula-2. 3rd, corr. ed. New York:Springer-Verlag, 1985.pattern recognitionAfter many years of effort researchers have been able tocreate systems that can recognize particular human faces(see computer vision). On the other hand, any normalsix-month-old child can effortlessly recognize familiarfaces (such as parents). The fundamental task of turningraw data (whether from senses, instruments, or computerfiles) into recognizable objects or drawing inferences iscalled pattern recognition. Pattern recognition is at theheart of many areas of research and application in computing(see artificial intelligence and data mining).Despite the challenge in getting machines to do whatcomes naturally for biological organisms, the potentialpayoffs are immense.A pattern-recognition system begins with data, whetherstored or real-time (such as from a robot’s camera). The firsttask in turning potentially billions of bytes of data intomeaningful objects is to extract features from what is likelya high proportion of redundant or irrelevant data. (Withvisual images, this often involves finding edges that defineshapes.) The extracted features are then classified to determinewhat objects they might represent. This can be doneby comparing structures to templates or previously classifieddata or by applying statistical analysis to determine thelikely correlation of the new data to existing patterns (seeBayesian analysis).Pattern recognition often includes learning algorithmsas well; indeed, the field is often considered to be a subtopicof machine learning. For example, classification systemscan be refined by “training” them and reinforcing successfuldeterminations (see neural network).ApplicationsThere are numerous applications of pattern recognition,often as part of intelligent systems used in such areas as linguistics(see language translation software), communications,intelligence and surveillance, identity verification(see biometrics), and the analysis of credit card transactionpatterns for signs of fraud. Some examples are shown in thefollowing table:Data Procedures Resultsspeech phonemes, transition textruleshandwritten character classification identifiedaddresspostal addresshandwritten character classification identify amount ofcheck (ATM)depositgeneral text grammar and syntax structure andmeaninge-mail identify characteristics spam detectionBayesian filterfacial image feature templates, identified personstatisticsbiometric feature extraction and verified identity(retina, finger- template comparisonprint, etc.)Further ReadingBishop. Christopher M. Pattern Recognition and Machine Learning.New York: Springer, 2006.Duda, Richard O., Peter E. Hart, and David G. Stork. Pattern Classification.New York: Wiley, 2001.International Association of Pattern Recognition. Available online.URL: http://www.iapr.org/. Accessed November 3, 2007.Pattern Recognition. American Association for Artificial Intelligence.Available online. URL: http://www.aaai.org/AITopics/html/pattern.html. Accessed November 4, 2007.Recognition Technology and Pattern Analysis. Available online.URL: http://alumnus.caltech.edu/~dave/pattern.html. AccessedNovember 4, 2007.

364 PDATheodoridis, Sergios, and Konstantinos Koutroumbas. Pattern Recognition.3rd ed. San Diego, Calif.: Academic Press, 2006.PDA (personal digital assistant)The first stage in making computing available away fromthe office desk was the development of “portable” and thenlaptop computers in the 1980s (see laptop computer).Laptops, however, are relatively heavy and bulky, and thusnot suitable for activities such as making notes at meetingsor keeping track of appointments while on the go.The logical solution to that need was to develop a computersmall enough to carry in a pocket or purse. The firsthandheld computer to achieve widespread recognition wasApple’s Newton, which the company referred to as a “personaldigital assistant.” This term, usually abbreviated toPDA, became a generic category with the introduction ofthe Palm Pilot, which first appeared in 1996, followed bythe seemingly ubiquitous RIM Blackberry in 1999.Features and UsesModern PDAs have sharp, readable displays, even given thelimited screen size. The role of the mouse is taken by navigationbuttons, and the ability to select items on the screenby touch or using a stylus (see touchscreen). (Some PDAsinclude small keyboards that can be typed on using twofingers or thumbs.) The operating system (such as Palm OS,Windows Mobile, or even Linux) is in read-only memory,and working memory is provided, expandable through theuse of SD (Secure Digital) or Compact Flash memory cards.Wireless connectivity provides access to the Internet andfor transferring data between the PDA and a regular PC (seeBluetooth and wireless and mobile computing). A synchronizationprogram installed on the PC can be used toensure that the latest version of each file will be stored onboth devices. (This also allows larger programs on the PCto work on and update data from the PDA—see personalinformation manager.)Typical PDA applications include an appointment calendar,address book for contacts, a simple note-taking program(see handwriting recognition), and increasingly,e-mail and a special Web browser designed for small displays.Many PDAs can also use their Bluetooth connectionto place calls through suitably equipped cellphones.PDAs can also be used for specialized applications thatinvolve the need to receive or update data while driving orwalking. Examples include navigation (with the use of aGPS device), delivery services, warehouse inventory management,reading utility meters, taking orders electronicallyin restaurants, and maintaining patient records in hospitals.Besides allowing for the recording of data, PDAs canalso include task-specific references such as prescriptiondrug databases or a medical dictionary.As with many other things in computing, the boundariesof the PDA category are becoming more fluid. Whilesoftware-enhanced mobile phones evolved separately (seesmartphone), PDA increasingly functions and telephonyare being seamlessly integrated into a single device, as withPalm’s Treo and especially Apple’s 2007 introduction of theiPhone, which also introduced an innovative “multitouch”interface that can respond to natural finger gestures such asflicking, sliding, or pinching.Further ReadingAl-Ubaydli, Mohammad. The Doctor’s PDA and Smartphone Handbook:A Guide to Handheld Healthcare. London: Royal Societyof Medicine Press, 2006.Carlson, Jeff, and Agen G. N. Schmitz. Palm Organizers. 4th ed.Berkeley, Calif.: Peachpit Press, 2004.Hormby, Tom. “Early History of Palm.” Silicon User. Availableonline. URL: http://siliconuser.com/?q=node/17. AccessedNovember 4, 2007.Kao, Robert, and Dante Sarigumba. BlackBerry for Dummies. NewYork: Wiley, 2007.Palm. Available online. URL: http://www.palm.com/us/. AccessedNovember 4, 2007.PDA Reviews. Brighthand. Available online. URL: http://www.brighthand.com/. Accessed November 4, 2007.RIM (Research in Motion). Available online. URL: http://www.rim.com/. Accessed November 4, 2007.PDF (portable document format)The PDF (portable document format) created by Adobe Systemshas become a very common way to make documentsavailable in a way that preserves the appearance of theoriginal.When PDF first came out in the early 1990s it was notvery suitable for use on the Web. PDF documents couldonly be viewed using expensive proprietary software, theycould not include embedded links (and thus could not behypertext), and they were large enough to be slow for downloadingon the dial-up connections of the time.All this had changed by the end of the decade: Adobedistributes the free Adobe Reader and plug-ins for all majorplatforms and browsers.OperationThe PDF specifications are open source, so anyone canwrite software to create or read documents in the format.PDF includes three elements: a subset of the PostScript pagedescription language (see PostScript), a system for specifyingand embedding common fonts (or referring to otherfonts), and a system for “packaging” the text and graphicsdescriptions into a file in compressed form. Later versionsof the PDF specification also allow users to interact withthe document, such as by filling in fields in a form or addingannotations to the text. PDF also includes support fortags (see xml) and descriptors that can be used with programssuch as screen readers for the blind.PDF also includes support for encrypting documents sothey can only be read with a password, and for controllingwhether the document can be copied or printed, though thisdepends on the user’s software understanding and obeyingthe restrictions.Although creating and editing PDF documents originallyrequired the relatively expensive Adobe Acrobat software,there are now a number of free or low-cost editorsand other PDF utilities for Windows, Mac OS X, and Linux/UNIX platforms.

Perl 365Further ReadingAdobe Creative Team. Adobe Acrobat 8 Classroom in a Book. SanJose, Calif.: Adobe Press, 2007.Adobe Reader (free download). Available online. URL: http://www.adobe.com/products/acrobat/readstep2_allversions.html.Accessed November 4, 2007.Lowagie, Bruno. iText in Action: Creating and Manipulating PDF.New York: Manning Publications, 2007.Padova, Ted. Adobe Acrobat 8 PDF Bible. Indianapolis: Wiley, 2007.Planet PDF: The Home of the PDF Community. Available online.URL: http://www.planetpdf.com/. Accessed November 4,2007.PerlThe explosive growth of the World Wide Web has confrontedprogrammers with the need to find ways to linkdatabases and other existing resources to Web sites. Thespecifications for such linkages are found in the CommonGateway Interface (see CGI). However, the early facilitiesfor writing CGI scripts were awkward and often frustratingto use.Back in 1986, UNIX developer Larry Wall had created alanguage called Perl (Practical Extraction and Report Language).There were already ways to write scripts for simpledata processing (see scripting languages) as well as ahandy pattern-manipulation language (see awk). However,Wall wanted to provide a greater variety of functions andtechniques for finding, extracting, and formatting data. Perlattracted a following within the UNIX community. Sincemuch Web development was being done on UNIX-basedsystems by the mid- and late-1990s, it was natural thatmany webmasters and applications programmers wouldturn to Perl to write their CGI scripts.As with many UNIX scripting languages, Perl’s syntaxis broadly similar to C. However, the philosophy behindC is to provide a sparse core language with most functionalitybeing handled by standard or add-in programlibraries. Perl, on the other hand, starts with most of thefunctionality of UNIX utilities such as sed (stream editor),C shell, and awk, including the powerful regular expressionsfamiliar to UNIX users. The language also includesa “hash” data type (a collection of paired keys and values)that makes it easy for a program to maintain and checklists such as of Internet hosts and their IP addresses (seehashing).Wall made it a point to solicit and respond to feedbackfrom Perl users, often by adding features or functions.Wall’s approach has been to provide as much practical helpfor programmers as possible, rather than worrying aboutthe language being well-defined, consistent, and thus easyto learn. For example, in most languages, to make somethinghappen only if a certain condition is not true, onewrites something like this:If ! (test for valid data)Print Error-Msg;Else Process_Data;In Perl, however, one can use the “unless” clause. Itlooks like this:Unless (Test for invalid data) {Process_Data;}Syntactically, the unless clause does not provide anythingmore than using an If and Else would, and it involves learninga different structure. However, it has the practical benefitof making the program a little easier to read by keeping theemphasis on what the program expects to be doing, not onthe possible error. Similarly, Perl offers an “until” loop:Until (Condition is met) {Do something;}In C, one would have to sayWhile (Condition is not met) {Do something;}This “Swiss army knife” approach to providing languagefeatures has been criticized by some computer scientistsas encouraging undisciplined and hard-to-verify programming.However, Perl’s many aficionados see the languageas the versatile, essential toolbox for the ever-challengingworld of Web programming. As the language evolvedthrough the late 1990s, it also added a full set of object-orientedfeatures (see object-oriented programming).Sample Perl ProgramThe following very simple code illustrates a Perl programthat reads some lines of data from a file and prints themout. The first line tells UNIX to execute the Perl interpreter.The file name data.txt is assigned to the string variable$file. The file is then opened and assigned to the variableINFO. A single statement (not a loop) suffices to assign allthe lines in the file to the array @lines. The “foreach” statementis a compact form of For loop that assigns each linein the array to the string variable $line and then prints it tothe screen as HTML.#!/usr/local/bin/perl$file = ’data.txt’;open(INFO, “

366 personal computerConway, Damian. Perl Best Practices. Sebastapol, Calif.: O’Reilly,2005.Lee, James. Beginning Perl. 2nd ed. Berkeley, Calif.: Apress, 2004.Schwartz, Randall L., Tom Phoenix, and Brian D. Foy. LearningPerl. 4th ed. Sebastapol, Calif.: O’Reilly, 2005.Wall, Larry, Tom Christiansen, and Jon Orwant. ProgrammingPerl. 3rd ed. Sebastapol, Calif.: O’Reilly, 2000.personal computer (PC)The development of the “computer chip” (see microprocessor)and the increasing use of integrated circuit technologymade it possible by the mid-1970s to begin to think aboutdesigning small computers as office machines or consumerdevices that could be individually owned or used. In abouta decade the personal computer, or PC, would become wellestablished in many businesses and a growing number ofhomes. After another decade, it became almost as ubiquitousas TV sets and microwaves. Parallel developmentsin hardware, software, operating systems, and accessorydevices made this revolution possible.The first commercial “personal computer” was the MITSAltair, a microcomputer kit built around an Intel 8080microprocessor. Building the kit required considerableskill with electronics assembly, but enthusiasts (includinga young Bill Gates) were soon writing software and designingadd-on modules for the kit (see Gates, William). Avariety of publications, notably Byte magazine, as well asthe Homebrew Computer Club gave hobbyists a forum forsharing ideas.By the late 1970s, personal computing was starting tobecome accessible to the general public. The Altair enthusiastshad moved on to more powerful systems that offeredsuch amenities as floppy disk drives and an operating system(CP/M, developed by Gary Kildall). Meanwhile, lesstechnically experienced people could also begin to experimentwith personal computing, thanks to the complete,ready-to-run PCs being offered by Radio Shack (TRS-80),Commodore (Pet), and in particular, the Apple II.In order to make serious inroads into the businessworld, however, the PC needed useful, reliable software.WordStar and later WordPerfect made it possible to replaceexpensive special-purpose word processing machines (suchas those made by Wang) with the more versatile PC. One ofthe biggest spurs to business use of PCs, however, was anentirely new category of software—the spreadsheet. DanBricklin’s VisiCalc (see spreadsheet) would make the PCattractive to accountants and corporate planners.The watershed year in personal computing was 1981because it brought the computer giant IBM into the PCarena (see IBM pc). The IBM PC had a somewhat morepowerful processor and could hold more memory than theApple II, but its main advantage was that it was backedby IBM’s decades-long reputation in office machines. Businesseswere used to buying IBM products, and conversely,many corporate buyers believed that if IBM was offeringdesktop computers, then PCs must be useful businessmachines.IBM (like Apple) had adopted the idea of open architecture—theability for third companies to make plug-in cardsto add functions to the machine. Thus, the IBM PC becamethe platform for a burgeoning hardware industry. Further, itturned out that other companies could reverse-engineer theinternal code that ran the system hardware (see bios) withoutinfringing IBM’s legal rights. This meant that companiescould make “clones” or IBM-compatible machines that couldrun the same software as the genuine IBM PC. The first clonemanufacturers (such as Compaq) sometimes improved uponIBM such as by offering better graphics or faster processors.However, by the late 1980s the trend was toward companiescompeting through lower prices for roughly equivalentperformance. Facing a declining market share, IBM triedto introduce a new architecture, called microchannel, thatprovided a mainframelike bus architecture for more efficientinput/output control. However, whatever technical advantagesthe new system (called PS/2) might have, the marketvoted against it by continuing to buy the ever more powerfulclones built on the original IBM architecture.Lower prices and more attractive options led to a growingnumber of users, which in turn encouraged greaterinvestment in software development. By the mid-1980s,Lotus (headed by Mitch Kapor) dominated the spreadsheetmarket with its Lotus 1-2-3, while WordPerfect dominatedin word processing.However, Microsoft, whose MS-DOS (or PC-DOS) hadbecome the standard operating system for IBM-compatiblePCs, introduced a new operating environment with agraphical user interface (see Microsoft Windows). By themid-1990s, Windows had largely supplanted DOS. Microsoftalso committed resources and exploited its intimateknowledge of the operating system to achieve dominance inoffice software through MS Word, MS Excel (spreadsheet),and MS Access (database).At the margins Apple’s Macintosh (introduced in 1984and steadily refined) has retained a significant following,particularly in education, publishing, and graphic artsapplications (see Macintosh). Although Windows nowprovides a similar user interface, Mac enthusiasts believetheir machine is still easier to use (and more stylish), andoften see it as a badge for those who “think different.”PC TrendsWhen graphical Web browsing made the Internet widelyaccessible in the mid-1990s, the demand for PCs increasedaccordingly. The desire for e-mail, Web browsing, and helpwith children’s homework led many families to purchasetheir first PCs. By 2000, about two-thirds of Americanchildren had access to computers at home, and virtuallyall schools had at least some PCs in the classroom. Usingsophisticated manufacturing and order processing systems,companies such as Dell and Gateway sell PCs directly toconsumers and businesses, largely displacing the neighborhoodcomputer store. These efficiencies (and lower pricesfor memory, processors, and other hardware) have broughtthe cost for a basic home PC down to less than $500, whilethe capabilities available for those willing to spend $1,500or so continued to increase. PC users now expect to be ableto play CD- and DVD-based multimedia while hearing goodquality sound.

personal health information management 367A number of challenges to the growth of the PC industryhave also emerged. As more and more of the activity ofPC users began to focus on the Internet, some companiesbegan to host office applications on servers (see applicationservice provider). Some pundits began to say thatwith applications being moved to remote servers or offeredover the corporate LAN, the PC on the desk could bestripped down considerably. The “network PC” could makedo with a slower processor, less memory, and no hard drive,since all data could be stored on the server.Generally, however, the attempts to supplant the fullfeatured,general-purpose PC have made little progress.One reason is that the cost of complete PC has declined somuch that the supposed cost savings of a network PC orInternet appliance have become less significant. Further,privacy issues and the desire of people to have controlover their own data are often cited as arguments in favorof the PC.Ironically, the PC industry’s greatest challenge maycome from its very success. As more and more householdsin the United States and other developed countries havePCs, it becomes harder to maintain the sales rate. By theearly 2000s, the power of recent PCs had become so greatthat the desire to upgrade every few years may have becomeless compelling and the recent economic downturn has hitthe computer industry particularly hard. So far it looks likethe fastest-growing areas in computer hardware no longerinvolve the traditional desktop PC, but handheld (palm)computers (see PDA) and the embedding of more powerfulcomputer capabilities into other machines such as automobiles(see embedded systems).Further ReadingFreiberger, Paul, and Michael Swaine. Fire in the Valley: The Makingof the Personal Computer. New York: McGraw-Hill, 1999.Long, Larry. Personal Computing Demystified. Emeryville, Calif.:McGraw-Hill/Osborne, 2004.Polsson, Ken. “Chronology of Personal Computers.” Availableonline. URL: http://www.islandnet.com/~kpolsson/comphist/.Accessed August 17, 2007.Thompson, Robert, and Barbara Fritchman Thompson. Buildingthe Perfect PC. Sebastapol, Calif.: O’Reilly, 2006.———. Repairing and Upgrading Your PC. Sebastapol, Calif.:O’Reilly, 2006.White, Ron, and Timothy Edward Downs. How Computers Work.8th ed. Indianapolis: Que, 2005.personal health information managementHealth care is at once a complex endeavor with many players,a vast industry, and a major expense of individuals,businesses, and governments. At the center of it all standsthe prospective patient (or consumer) seeking to maintainor restore health.While the health care industry has long been a majoruser of computer technology (see medical applicationsof computers), the modern Web has brought a variety ofservices (many free) that can help health care consumerslearn more about conditions and treatments and comparehospitals, doctors, and other providers.Medical Information SitesIn today’s health care environment patients often have onlya few minutes to ask their doctor important questions abouttheir condition and possible treatments. Patients often feelthey have been left on their own when it comes to obtainingdetailed information. According to surveys by the PewInternet & American Life Project, by the end of 2005 about20 percent of Web users were reporting that the Internet“has greatly improved the way they get information abouthealth care.” Further, 7 million users had reported thatWeb sites had “played a crucial or important role in copingwith a major illness.”A variety of Web sites ranging from comprehensive andexcellent to dubious (at best) offer health-related information.In evaluating them, it is important to determine whosponsors the site and what is the source of the informationprovided. The very extensive WebMD site, for example, isreviewed for accuracy by an independent panel of experts.One of the foremost medical institutions, the Mayo Clinic,also has an authoritative site. The site OrganizedWisdom.com offers a search engine that emphasizes informationthat has been reviewed by doctors for accuracy, while eliminatinglow-quality or duplicative results.Even if information is accurate, however, users mayoften lack the necessary background or context for interpretingit correctly. Understanding the results of medicalstudies, for example, requires some knowledge of how studiesare designed, the population used, and the statisticalsignificance and applicability of the results. As a practicalmatter, therefore, patients should not make any major decisionsabout diet, medication, or treatment options withoutconsulting a medical professional. Attempts at self-diagnosiscan be particularly problematic.Support Groups and Provider RatingsOn the other hand, carefully chosen online information canbe very useful and can even improve outcomes. Patients canlearn what questions to ask their physicians, and may evenbe able to suggest relevant information of which the physicianis unaware.During treatment, patients can find emotional andpractical support online. In keeping with the trend towardonline social cooperation (see social networking anduser-created content) a number of sites are helping consumersfind or create support groups. Such groups havelong been important, particularly for patients with conditionssuch as cancer or serious chronic disease. For example,DailyStrength.org offers 500 online support groups for agreat variety of conditions. Users can create online journalsto describe their daily struggles and can send supportivemessages and “hugs.” According to a 2007 report by the PewInternet & American Life Project, about half of adults withchronic conditions use the Internet regularly and extensivelyto help them manage their treatment and life issues.Selecting a compatible medical professional is anotherarea where online sites can help prospective patients. Userratings have proven helpful on Amazon.com and other sitesfor a variety of products and services (for example, Yelp.com and the popular Angie’s List). A site called RateMDs.

368 personal information managercom has applied the same mechanism to allow patients toanonymously rate their doctors. (As with other user-providedreviews, however, one needs to be aware of the possibilitythat the reviews do not constitute a representativesample of consumer experience.) Patients can also personallyshare their experiences via a YouTube-like site calledICYou.com.Although social networking and content-sharing siteshave been most popular among the younger generation,the increasing adoption of these venues by older adultsand seniors is likely to fuel growth in online health-relatedservices in years to come, as is the continuing need to findcost-effective ways of serving growing patient populations.Further ReadingColliver, Victoria. “For These Startups, Patients Are a Virtue.”San Francisco Chronicle, October 1, 2007, p. C1. Availableonline. URL: http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/10/01/BUDKSGAF4.DTL. Accessed November 5, 2007.Cullen, Rowena. Health Information on the Internet: A Study of Providers,Quality, and Users. Westport, Conn.: Praeger, 2006.DailyStrength. Available online. URL: http://dailystrength.org/.Accessed November 5, 2007.Fox, Susannah. “E-Patients with a Disability or Chronic Disease.”Pew Internet & American Life Project, October 8, 2007.Available online. URL: http://www.pewinternet.org/pdfs/EPatients_Chronic_Conditions_2007.pdf. Accessed November6, 2007.Lewis, Deborah, et al., eds. Consumer Health Informatics: InformingConsumers and Improving Health Care. New York: Springer,2005.Madden, Mary, and Susannah Fox. “Finding Answers Onlinein Sickness and in Health.” Pew Internet & American LifeProject. Available online. URL: http://www.pewinternet.org/pdfs/PIP_Health_Decisions_2006.pdf. Accessed November6, 2007.Mayo Clinic. Available online. URL: http://www.mayoclinic.com/.Accessed November 5, 2007.Organized Wisdom. Available online. URL: http://organizedwisdom.com/. Accessed November 5, 2007.RateMDs.com. Available online. URL: http://www.ratemds.com.Accessed November 5, 2007.WebMD. Available online. URL: http://www.webmd.com/. AccessedNovember 5, 2007.personal information manager (PIM)A considerable amount of the working time of most businesspeopleis taken up not by primary business tasks butin keeping track of contacts, phone conversations, notes,meetings, deadlines, and other information needed to planor coordinate activities. Software designers have respondedto this reality by creating software to help manage personalinformation.Early PC users improvised ways of using available softwareapplications for tracking their activities. For example,a spreadsheet with text fields might be used to recordand sort contacts and their associated information suchas phone numbers or data could be organized in tables inword processor documents. However, such improvisationscan be awkward to use. Loading a full-sized word processoror spreadsheet application takes time (and until Windowsand other multitasking solutions came along, only one programcould be run at a time). Further, it is hard to integrateinformation or keep track of the “big picture” with severaldifferent kinds of information stored in different formatswith different programs.What was needed was a single application that couldintegrate the personal information and make it accessiblewithout the user having to shut down the main applicationprogram. The first successful PIM was Borland Sidekick,first released in 1984. Although MS-DOS was designed torun only a single program at a time, it had an obscure featurethat allowed additional small programs to be loadedinto memory where they could be triggered using a keycombination. Taking advantage of this feature, Sidekickallowed someone while using, for example, a word processor,to pop up a note-taking window, an address book, calendar,telephone dialer, calculator, or other features. WhenMicrosoft Windows replaced DOS, it became possible torun more than one full-fledged application at a time. PIMscould then become full-fledged applications in their ownright, and offer additional features.As e-mail became more common on local networks inthe later 1980s and via the Internet in the 1990s, PIM featuresbegan to be integrated with e-mail programs suchas Microsoft Outlook and Netscape Navigator’s communicationsfacilities. New features included the automaticcreation of journal entries from various activities and thecreation of “rules” for recognizing and routing e-mail messageswith particular senders or subjects. A variety of freewareand shareware PIMs are available for users who wantan alternative to the commercial products, and a number ofPIMs are available for Macintosh and Linux-based systems.Web-based personal information management tools canmake it particularly easy to coordinate a widely scatteredworkforce, since each user merely has to access the servingWeb site. Recently, low-cost (or even free) Web-based applicationsthat include PIM as well as productivity featureshave been introduced—for example, Google Apps.The growth of handheld (or palm) computers (see PDA)and more sophisticated cell phones has created a need toprovide PIM features for these devices (see smartphone).Since the capacity of handheld devices is limited comparedto desktop PCs, there is also a need for software to alloweasy transfer of information between portable devices anddesktop PCs. This can be done with a serial, USB, or evenwireless connection.In the future, the PIM is likely to become an integratedsystem that operates on a variety of handheld and desktopdevices and seamlessly maintains all information regardlessof how it is received. There will also be greater abilityto give voice commands (such as to dial a person or to askfor information about a contact), and to have messages readaloud (see speech recognition and synthesis). The softwareis also likely to include sophisticated “agents” that canbe instructed to carry out such tasks as prioritizing messagesor returning routine calls (see software agent).Further ReadingBoyce, Jim, Beth Sheresh, and Doug Sheresh. Microsoft Outlook2007 Inside Out. Redmond, Wash.: Microsoft Press, 2007.

phishing and spoofing 369Jones, William. Personal Information Management. Seattle: Universityof Washington Press, 2007.Lineberger, Michael. Total Workday Control: Using Microsoft Outlook.San Ramon, Calif.: New Academy Publishers, 2006.“Over 160 Free Personal Information Managers.” Available online.URL: http://www.lifehack.org/articles/lifehack/over-160-freepersonal-information-managers.html.Accessed August 17,2007.philosophical and spiritualaspects of computingWhen modern digital computing emerged in the 1940s, itevolved from two roots: engineering (particularly electricalengineering) and mathematics. The goals of the earliest computerdesigners were focused naturally enough on computing,although several early thinkers (see Bush, Vannevar;Shannon, Claude; and Turing, Alan) had already begunto think of computers as symbol-processing and knowledgeretrievingmachines, not just number crunchers.As computer scientists began to become more concernedabout the structure of data and the modeling of real-worldobjects in computer languages (see object-oriented programming),they began to wrestle with some areas longfamiliar to philosophers. As data structure involved intoknowledge representations, epistemology (the philosophicalinvestigation of the meaning and accessibility of knowledge)became more relevant, particularly in developingsystems for artificial intelligence and machine learning.Also relevant is ontology (the nature and relationship ofentities—see ontologies and data models), particularlywith regard to the modern effort to encode relationshipsbetween items of knowledge into Web pages (see semanticWeb).The Computer as Philosophical LaboratoryBeyond investigating the potential for applying philosophicalideas to knowledge engineering, many philosophershave also taken increasing notice of the possibilities thatartificial intelligence, highly complex dynamic structures(particularly the Internet), and human-computer interactionoffer for investigating long-standing and often seeminglyintractable philosophical problems.One of the knottiest problems is the nature of somethingthat people experience during every waking moment—consciousness,that awareness of being an “I” or “self” that isexperiencing both an inner world of memories and thoughtsand the outer world conveyed by the senses. One reasonwhy the problem of consciousness is so difficult to resolveis that cognitive scientists and philosophers lack the abilityto compare human consciousness with other possibleconsciousness. (Some “higher” animals may be consciousin some sense, but they cannot tell us about it.) However,as AI programs attempt to model aspects of human cognition,they can help us find similarities and possible differencesbetween the way computers and people “think.” Ofcourse philosophers take a wide variety of positions on thequestion of whether there is anything ultimately distinctiveabout what we call consciousness, and whether computersor robots might someday become truly conscious. (Forexamples of differing views see Dreyfus, Hubert; Kurzweil,Raymond; and McCarthy, John.)Finally, a number of writers have related developmentsin modern computing to ultimate philosophical or spiritualconcerns. For example, the World Wide Web can be comparedto the world-girdling “noosphere” of evolving knowledgedescribed by theologian-paleontologist Pierre Teilhardde Chardin in the mid-20th century. Thus there has beenconsiderable speculation (and perhaps hype) about a newform of collective consciousness emerging through theinteraction of people as well as increasingly intelligent programson the Net. On the other hand, the experience ofimmersive online environments (see online games andvirtual reality) revisits a question that goes back to Descartesin the 17th century—whether what we perceive asreality might actually be an illusion—and this questionresonates with the works of Western Gnostics and EasternBuddhists, not to mention Hollywood’s The Matrix.The dialog among philosophy, spiritual practice, andthe rapidly changing computer world is likely to remainfascinating.Further ReadingDavis, Erik. Techgnosis: Myth, Magic, and Mysticism in the Age ofInformation. New York: Harmony Books, 1998.Floridi, Luciano. Philosophy and Computing: An Introduction. NewYork: Routledge, 1999.———, ed. Philosophy of Computing and Information. Malden,Mass.: Blackwell, 2004.Foerst, Anne. God in the Machine: What Robots Teach Us aboutHumanity and God. New York: Dutton, 2004.Hayles, N. Katherine. How We Became Posthuman: Virtual Bodies inCybernetics, Literature, and Informatics. Chicago: Universityof Chicago Press, 1999.International Association for Computing and Philosophy. Availableonline. URL: http://www.ia-cap.org/. Accessed November6, 2007.Irwin, William. The Matrix and Philosophy. Chicago: Open Court,2002.Tetlow, Philip. The Web’s Awake: An Introduction to the Field of WebScience and the Concept of Web Life. Hoboken, N.J.: Wiley,2007.phishing and spoofingJust about anyone with an e-mail account has received messagespurporting to be from a bank, a popular e-commercesite such as Amazon or eBay, or even a government agency.Typically the message warns of a problem (such as a suspendedaccount) and urges the recipient to click on a linkin the message. If the user does so, what appears to looklike the actual site of the relevant institution is actually a“spoof,” or fake site. If the user goes on to enter informationsuch as account numbers or passwords in order to fixthe “problem,” the information actually goes to the operatorof the fake site, where it can be used for fraudulent purchasesor even impersonation (see identity theft). Thebogus site can also attempt to download viruses, spyware,keyloggers, or other forms of “malware” to the unwittinguser’s computer.

370 phishing and spoofing“Phishing” messages such as this fake IRS e-mail try to trick usersinto clicking on links to equally bogus Web sites that can steal personalinformation or infect computers with viruses.This all-too-common scenario is called “phishing,”alluding to “fishing” for unwary users with various sorts ofbait, with the f changed to ph in keeping with traditionalhacker practice. Phishing is similar to other techniques formanipulating people through deception, fear, or greed thathackers often refer to as “social engineering.” Unlike oneon-oneapproaches, however, phishing relies on the abilityto send large quantities of e-mail at virtually no cost (seespam), the availability of simple techniques for disguisingboth e-mail addresses and Web addresses (URLs), and theease with which the appearance of a Web site can be convincinglyreplicated.Although e-mail is the most common “hook” for phishing,any form of communication, including text or instantmessages, can be used. Recently sites such as MySpace havebecome targets for automated phishing expeditions thatchanged links on pages to point to fraudulent sites (seesocial networking).Defenses and CountermeasuresWary users have a number of ways to reduce their chance ofbeing “phished.” Some signs of bogus messages include:• The message is addressed generically (“dear PayPaluser”) or to the user’s e-mail address rather than theaccount name.• The text of the message contains spelling errors orpoor grammar.• The URL shown for a link in the message (perhaps viaa “tool tip”) does not match the institution’s real Webaddress.There are even interactive games such as “Anti-PhishingPhil” that users can play to test their ability to detect phishingattempts.Unfortunately, modern phishers are becoming increasinglysophisticated. Some phishing messages can be personalized,using the target’s actual name. URLs can bedisguised so that discrepancies do not appear. When indoubt, the safest thing to do is always to access the institutionby typing (not copying) its name directly in the Webbrowser rather than clicking on a link in e-mail. (In a practicecalled “pharming,” a legitimate Web site can in effectbe hijacked so that normal user accesses will be divertedto the fraudulent site. Users have no real defense againstpharming; this is a matter for security professionals at therelevant Web sites.)Fortunately there are ways in which software can helpdetect and block most phishing attempts. A good spam filteris the first line of defense and can block many phishing messagesfrom getting to the user in the first place. Anti-phishingfeatures are also increasingly included in Web browsers,or available as plug-ins. Thus “blacklists” of known phishingsites can be checked in real time and warnings given, orthe site’s address can be blocked from access by the system.Web sites can also introduce an added layer of security:Bank of America, for example, asks users to select and labelone of several images offered by the bank. The image andlabel are subsequent displayed as part of the log-in process.If the user does not see the image and the user’s label, thenthe site is presumably not the real bank site.Legislative ResponsePhishing has been one of the fastest-growing types of onlinecrime in recent years (see computer crime and securityand online frauds and scams). By mid-2007 the Anti-Phishing Working Group (an association of financial institutionsand businesses) was reporting the appearance ofmore than 30,000 new phishing sites per month (the largestnumber operating from China), though a site typically staysonline for only a few days. Phishing contributed significantlyto the $49 billion cost of identity theft in 2006 as estimatedby Javelin Research. Further, industry surveys havesuggested that phishing has aroused considerable consumerconcern, slowing down the adoption or continued use ofsome financial services (see banking and computers).In response to this growing concern, the U.S. FederalTrade Commission filed its first civil suit against a suspectedphisher in 2004. The United States and other countrieshave also arrested phishing suspects, generally undersome form of wire fraud statute. Starting in 2004, antiphishingbills have been introduced in Congress, thoughnone had passed as of 2007. However, the CAN-SPAM Actof 2003 was used in 2007 to convict a defendant accusedof sending thousands of phishing e-mails purporting to befrom America Online (AOL). Many states have also introducedanti-phishing legislation.Further ReadingAnti-Phishing Working Group. Available online. URL: http://www.antiphishing.org/. Accessed November 6, 2007.

photography, digital 371Jacobson, Markus, and Steven Myers, eds. Phishing and Countermeasures:Understanding the Increasing Problem of ElectronicIdentity Theft. Hoboken, N.J.: Wiley-Interscience, 2006.James, Lance. Phishing Exposed: Uncover Secrets from the Dark Side.Rockland, Mass.: Syngress Publishing, 2005.Lininger, Rachael, and Russell Dean Vines. Phishing: Cutting theIdentity Theft Line. Indianapolis: Wiley, 2005.PhishTank. Available online. URL: http://www.phishtank.com/.Accessed November 6, 2007.Sheng, Steve, et al. “Anti-Phishing Phil: The Design and Evaluationof a Game That Teaches People Not to Fall for Phish.”Carnegie Mellon University. Available online. URL: http://cups.cs.cmu.edu/soups/2007/proceedings/p88_sheng.pdf.Accessed November 6, 2007. (The game itself is available athttp://cups.cs.cmu.edu/antiphishing_phil/.)U.S. Federal Trade Commission. “FTC Consumer Alert: How Notto Get Hooked by a ‘Phishing’ Scam.” October 2006. Availableonline. URL: http://www.ftc.gov/bcp/edu/pubs/consumer/alerts/alt127.pdf. Accessed February 8, 2008.photography, digitalFor more than 150 years photography has depended on theuse of film made from light-sensitive chemicals. However,digital photography, first developed in the 1970s, emergedin the late 1990s as a practical, and in some ways superior,alternative to traditional photography.The basic idea behind digital photography is that light(photons) can create an electrical charge in certain materials.In 1969, engineers at Bell Labs invented a light-sensitivesemiconductor that became known as a charge-coupleddevice (CCD). The original intention of the developers wasto use an array of CCDs to make a compact black-andwhitevideo camera for the videophone, a device that didnot prove commercially viable. However, astronomers weresoon using CCD arrays to capture images too faint for thehuman eye or even for conventional film.Digital photography remained confined to such specializedapplications until the mid-1990s. By then, the growinguse of multimedia and the World Wide Web made digitalphotography an attractive alternative for getting imagesonline quickly, avoiding the need to scan traditional printsor negatives. At the same time, cheaper, more powerfulprocessors and larger capacity memory storage made goodquality digital cameras more viable as a consumer product.A digital camera uses the same type of lenses and opticalsystems as a conventional camera. Instead of fallingupon film, however, the incoming light strikes an array ofCCD “photosites.” Each photosite represents one pictureelement, or pixel, which will appear as a tiny dot in theresulting picture. (Camera resolution is typically measuredin millions of pixels, or “megapixels.”)The surface of the array contains an abundance of freeelectrons. As light strikes a photosite, it creates a chargethat draws and concentrates nearby electrons. The voltageat a photosite is thus proportional to the intensity of thelight striking it. The charge of each row of photosites istransferred to a corresponding read-out register, where it isamplified to facilitate measurement.The camera uses an analog-to-digital converter (seeanalog and digital) to convert the amplified voltages todigital numeric values. Early consumer digital cameras typicallyused 8-bit values, limiting the camera to a range ofgradated intensity from 0 to 255. However, many camerastoday use up to 12 bits, giving a range of 0 to 4096.The CCD mechanism itself measures only light intensities,not colors. To obtain color, many cameras use ared, green, or blue (RGB) filter at each photosite. (Somemanufacturers use cyan, yellow, green, and magenta filtersinstead.) Since each photosite registers only a singlecolor, interpolation algorithms must be used to estimate theactual color of each pixel by using laws of color optics andcomparing the colors and intensity of the adjacent pixels.New high-end cameras are starting to eschew interpolationin favor of using a complete, separate CCD array forDigital cameras use a charge-coupled device (CCD) to convert incoming light to varying voltages that are digitized to create pixel values.They have largely replaced traditional film cameras for most applications.

372 PHPeach of the three RGB colors and thus making and combiningthree complete exposures that directly capture thecolors. This produces the best possible color accuracy but ismore expensive.The final image data is stored using a standard file format,usually JPEG (see graphics formats). The most commonlyused storage medium is an insertable “flash” memorymodule. The major competing memory card standards areCompactFlash, SD, and Sony Memory Stick. Storage capacitiesrun to 4 GB. As with regular RAM, the cost of flashmemory has declined considerably in recent years.In determining the adequacy of the camera’s storagecapacity, the user must also consider the camera’s resolution(number of pixels) and whether images will be compressedbefore storage (see data compression). While acertain amount of compression can be achieved withoutdiscernable degradation of the image, more drastic “lossy”compression sacrifices image quality for compactness. Itshould also be noted that as image resolution (and thus filesize) increases, the time needed to process and store eachimage will also increase, limiting how rapidly successiveexposures can be made.Most digital cameras have a USB connector (see USB),making it easy to upload the stored images from the camerato a PC. Once in the PC, images can be edited or otherwisemanipulated using the basic photo editing software usuallyincluded with the camera or a full-featured professionalproduct such as Adobe Photoshop.The same trends that have brought more capabilityper dollar spent on digital cameras have been even moreevident in printers (see printer). Using resolutions of2880 dots per inch or more and special papers, digitalcamera users can make prints with a quality similar tothat produced by traditional photo developers. Computerprints are more subject to color fading over time than areconventional prints, although some printer manufacturersnow offer toner that will resist fading for 25 years ormore.Future TrendsHigh-end consumer digital cameras reached the 8–10 megapixelrange by 2008, allowing for images that can be “blownup” to 10 by 12 inches or larger while retaining image qualitycomparable to conventional photos. Professional-gradedigital cameras (“digital SLRs”) are rated at 10 megapixelsor more. The need for such cameras for professional workarises not only from the higher resolution requirementsbut also because these cameras have the very high-qualityoptics used in fine 35 mm cameras, as well as having agreater variety of available specialty lenses. (Consumer digital“superzoom” cameras, however, do offer zoom lensesroughly comparable to those for low-cost 35-mm cameras.)The quality and convenience of digital photography ensurethat digital cameras will supplant conventional cameras formost consumer and many professional applications. Manydigital cameras also have the ability to shoot short videosequences. The ubiquity of digital cameras and digital video(even in many cell phones) has had important social consequencesby facilitating transmission of pictures of disasters,political gaffes, and other events often outside the mainstreammedia (see user-created content and YouTube).Digital camcorders will also become more widely used.Their resolution is generally from about a quarter millionpixels to a million pixels—considerably lower than fordigital still cameras, but adequate and likely to improve.Digital video cameras are also rated according to lux value,indicating the minimum light level for satisfactory recording.Most digital videos store the captured image to tape(either MiniDV or Hi-8), but some newer cameras use builtinrecordable DVD disks instead (see CD-Rom and DVD-ROM). The ability to digitally edit video direct from thecamera is also an important advantage.Further ReadingBusch, David D. Digital SLR Cameras & Photography for Dummies.2nd ed. Hoboken, N.J.: Wiley, 2007.Etchells, Dave. “Finding the Right Digital Camera.” ImagingResource Newsletter. Available online. URL: http://www.imaging-resource.com /TIPS/ BUYGD/ BUYGUID.HTM.Accessed August 17, 2007.King, Julie Adair. Digital Photography for Dummies. 5th ed. Hoboken,N.J.: Wiley, 2005.Silva, Robert. “Digital Camcorder Formats.” Available online. URL:http://hometheater.about.com/od/camcorders/a/camformats_2.htm. Accessed August 17, 2007.Wilson, Tracy V., K. Nice, and G. Gurevich. “How Digital CamerasWork.” Available online. URL: http://www.howstuffworks.com/digital-camera.htm. Accessed August 17, 2007.PHPPHP is a very popular scripting language primarily usedfor creating dynamic Web pages (see Ajax and scriptinglanguages). PHP originated in 1994 as a way for Danishprogrammer Rasmus Lerdorf to replace a set of Perl scriptsused to manage his own Web page—hence the originalname “personal home page.” Lerdorf released the first versiontogether with a “form interpreter” in 1995. In 1997 thelanguage parser was rewritten by Israeli developers ZeevSuraski and Andi Gutmans, who launched PHP3 in 1998;since then the initials PHP have (recursively) stood for PHP:Hypertext Processor. In 2004 the current version, PHP5,was released. As the language has evolved, it has improvedin its support for objects (see object-oriented programming)as well as in its connectivity to MySQL and otherdatabase and Web-application coordination technologies.PHP normally runs on a Web server and processes PHPcode, which is often embedded within Web pages (seeHTML). The classic Hello World program would look likethis:The PHP processor parses only the code within the delimiters. (An alternative set of delimiters is .Besides being embedded in HTML pages, PHP canbe used interactively at the command line, where it hasreplaced older languages such as awk, Perl, or shell script-

PL/I 373ing for many users. PHP can also be linked to user-interfacelibraries (such as GTK+ for Linux/UNIX) to create applicationsthat run on the client machine rather than the server.PHP has a basic set of data types plus one called“resource” that represents data processed by special functionsthat return images, text files, database records, andso on. Additionally, PHP5 provides full support for objects,including private and protected member variables, constructorsand destructors, and other features similar tothose found in C++ and other languages.There are numerous libraries of open-source objectsand functions that enable PHP scripts to perform commonInternet tasks, including accessing database servers (such asMySQL) as well as extensions to the language to handle popularWeb formats such as Adobe Flash animation. Programmershave access to a wide range of PHP resources throughPEAR (the PHP Extension and Application Repository).The combination of sophisticated features and easyinteractive scripting has made PHP the language of choicefor many Web developers, who use it as part of the group oftechnologies called LAMP, for Linux, Apache (Web server),MySQL (database), and PHP.Further ReadingAchour, Mehdi, et al. PHP Manual. Available online. URL: http://www.php.net/manual/en/. Accessed November 7, 2007.Lerdorf, Rasmus, Kevin Tatroe, and Peter MacIntyre. ProgrammingPHP. 2nd ed. Sebastapol, Calif.: O’Reilly Media, 2006.PEAR-PHP Extension and Applications Repository. Availableonline. URL: http://pear.php.net/. Accessed November 7,2007.PHP [official Web site]. Available online. URL: http://php.net/.Accessed November 7, 2007.Zandstra, Matt. PHP Objects, Patterns, and Practice. Berkeley, Calif.:Apress, 2004.PL/IBy the early 1960s, two programming languages were inwidespread use: FORTRAN for scientific and engineeringapplications and COBOL for business computing. However,applications were becoming larger and more complex, callingfor a wider variety of capabilities. For example, scientificprogrammers needed to provide data-processing andreporting capabilities as well as computation. Business programmers,in turn, increasingly needed to work with formulasand statistics and needed floating-point and othernumber formats.Language developers thus began to look toward a general-purposelanguage that could be equally at home withwords, numbers, and data files. Meanwhile, IBM was preparingto replace its previously separate scientific and businesscomputer systems with the versatile System/360. Theyand one of their user groups, SHARE, formed a joint committeeto develop a new language for this new machine.At first the designers thought in terms of extendingFORTRAN to provide better text and data-processing capabilities,so they designated the new language FORTRANVI. However, their focus soon changed to designing acompletely new language, which was known until 1965 asNPL (New Programming Language). Because this acronymalready stood for Britain’s National Physical Laboratory, thename of the language was changed to PL/I (ProgrammingLanguage I).Language FeaturesPL/I has been described as the “Swiss army knife of languages”because it provides so many features drawn fromdisparate sources. The basic block structure and controlstructures (see loop and branching statement) wereadapted from Algol, a relatively small language that hadbeen devised by computer scientists as a model for structuredprogramming (see Algol) and is also similar to Pascal(see Pascal). Blocks can be nested, and variables declaredwithin a block can be accessed only within that block andits nested blocks, unless declared explicitly otherwise.PL/I includes a particularly rich variety of data typesand can specify even the number of digits for numeric data.A PICTURE clause similar to that in COBOL can be used tospecify exact layout. However, the language takes a morepragmatic approach than Algol or Pascal; data need notbe declared and will be given default characteristics basedon context. Input/Output (I/O) is built into the languagerather than provided in an external library, and the flexibleoptions include character, streams of characters, blocks,and records with either sequential or random access.In general, PL/I provides more control over the lowleveloperation of the machine than Algol or even successorssuch as C. For example, there is an unusual amount ofcontrol over how variables are stored, ranging from STATIC(present throughout the life of the program) to AUTO-MATIC (allocated and deallocated as the containing blockis entered and exited) to CONTROLLED, where memorymust be explicitly allocated and freed. Pointers allow memorylocations to be manipulated directly. PL/I also providedmore elaborate facilities for handling exceptions (errors)arising from hardware condition, arithmetic, file-handling,or other conditions.Example ProgramThe following program executes a DO loop and counts fromone to the number of items specified. It then outputs thetotal of the numbers and their average.COUNTEM: PROCEDURE OPTIONS (MAIN);DECLARE (ITEMS, COUNTER, SUM, AVG) FIXED;ITEMS = 10;SUM = 0;DO COUNTER = 1 TO ITEMS;SUM = SUM + COUNTER;END;AVG = SUM / ITEMS;PUT SKIP LIST (“TOTAL OF ”);PUT ITEMS;PUT (“ITEMS IS ”);PUT TOTAL;PUT SKIP LIST (“THE AVERAGE IS: ”);PUT AVG;END COUNTEM;

374 Plug and PlayImpact of the LanguageBecause of its many practical features and its availability forthe popular IBM 360 mainframes, PL/I enjoyed considerablesuccess in the late 1960s and 1970s. The language waslater ported to most major platforms and operating systems.When personal computers came along, PL/I becameavailable for IBM’s OS/2 operating system as well as forMicrosoft’s DOS and Windows, although the language neverreally caught on in those environments.Computer scientists such as structured programmingguru Edsger Dijkstra decried PL/I’s lack of a clear, welldefinedstructure. In his Turing Award Lecture in 1972,Dijkstra opined that “I absolutely fail to see how we cankeep our growing programs firmly within our intellectualgrip when by its sheer baroqueness the programming language—ourbasic tool, mind you!—already escapes ourintellectual control.” (See Dijkstra, Edsger.)On a practical level the sheer number of features inthe language meant that truly mastering it was a lengthyprocess. A language like C, on the other hand, had a muchsimpler “core” to master even though it was less versatile.PL/I also tended to retain the mainframe associations fromits birth at IBM, while C grew up in the world of minicomputersand the UNIX community and proved more suitablefor PCs. Nevertheless, PL/I provided many examples thatlanguage designers could use in attempting to design betterimplementations.Further ReadingThe Essentials of PL/I Programming Language. Piscataway, N.J.:Research and Education Association, 1993.Hughes, Joan Kirby. PL/I Structured Programming. 3rd ed. NewYork: Wiley, 1986.“PL/I Frequently Asked Questions (FAQ).” Available online. URL:http://www.faqs.org/faqs/computer-lang/pli-faq/. AccessedAugust 17, 2007.“The PL/I Language.” Available online. URL: http://home.nycap.rr.com/pflass/pli.htm. Accessed February 9, 2008.Sebesta, Robert W. Concepts of Programming Languages. 8th ed.Boston: Pearson Addison-Wesley, 2007.Plug and PlayIn early MS-DOS systems installation of new hardware suchas a printer often had to be performed manually by copyingfiles (see device driver) to the hard drive from floppiesand then making specified settings to the system configurationfiles AUTOEXEC.BAT and CONFIG.SYS. These settingsoften involved unfamiliar concepts such as interrupts(IRQs) and DMA (direct memory access) channels.When Windows came along, device manufacturers generallyprovided an installation program that takes care ofcopying the files and making the necessary changes to thesystem registry. However, there was still the problem ofensuring that one had a driver compatible with the versionof the operating system in use, and users were sometimesasked to make choices for which they were not prepared(such as choosing which port to use).By the mid-1990s, Intel was promoting a standard for theautomated detection and configuration of devices. Knownas Plug and Play (PnP), this standard was incorporated inversions of Microsoft Windows starting with Windows 95(see Microsoft Windows). The required hardware supportsoon appeared on PC motherboards and expansion cards.With Plug and Play the user simply connects a printer,scanner, or other device to the PC. Windows detects thata device has been connected and queries it for its officialname and other information. If necessary, Windows canthen prompt the user for a disk containing the appropriatedriver or even search for a driver on a Web site.The concept of Plug and Play extends beyond the Windowsworld, however. In recent years there has been interestin developing a Universal Plug and Play (UPnP) protocolby which a variety of devices could automatically configurethemselves with any of a variety of different networks.This would be particularly helpful for home users who areincreasingly setting up small networks so they can sharebroadband Internet connections, as well as the growingnumber of users who want their desktop PC to work withhandheld (palm) computers and other devices. Microsoftsupports UPnP in versions of Windows starting with MEand XP.Further ReadingBigelow, Stephen J. The Plug & Play Book. New York: McGraw Hill,1999.Shanley, Tom. Plug and Play System Architecture. Reading, Mass.:Addison-Wesley, 1995.Universal Plug and Play Forum. Available online. URL: http://www.upnp.org/. Accessed August 17, 2007.plug-inA number of applications programs include the ability forthird-party developers to write small programs that extendthe main program’s functionality. For example, thousandsof “filters” (algorithms for transforming images) have beenwritten for Adobe Photoshop. These small programs arecalled plug-ins because they are designed to connect tothe main program and provide their service whenever it isdesired or required.Perhaps the most commonly encountered plug-ins arethose available for Web browsers such as Firefox, Netscape,or Internet Explorer. Plug-ins can enable the browser to displaynew types of files (such as multimedia). Many standardprograms for particular kinds of files are now providedboth as stand-alone applications and as browser plug-ins.Examples include Adobe (PDF document format), AppleQuickTime (graphics, video, and animation), RealPlayer(streaming video and audio), and Macromedia Flash (interactiveanimation and presentation). These and many otherplug-ins are offered free for the downloading, in order toincrease the number of potential users for the formats andthus the market for the development packages.One of the most useful plug-ins found in most browsersis one that allows the browser to run Java applets (see Java).In turn, Java is often used to write other plug-ins.Beyond such traditional workhorses, a number of innovativebrowser plug-ins have appeared, particularly for the

pointers and indirection 375increasingly popular Firefox browser. For example, thereare plug-ins that enable the user to view and work withthe HTML and other elements of the page being viewed.Another popular area is plug-ins that make it easier tocapture and organize material from Web pages, going wellbeyond the standard favorites or bookmark facility.Including plug-in support for an application enables volunteeror commercial third-party developers to in effectincrease the feature set of the main application, which inturn benefits the original developer. In the broader perspective,plug-ins are a way to harness the collaborative spiritfound in open-source development, creating a communitythat is continually improving applications tools and makingthem more versatile. (The open-source Eclipse programmingenvironment is a good example.)Further ReadingAdd-Ons for Internet Explorer. Available online. URL: http://www.windowsmarketplace.com/category.aspx?bcatid=834&tabid=1/. Accessed August 17, 2007.Benjes-Small, Candice M., and Melissa L. Just. The Library andInformation Professional’s Guide to Plug-ins and Other WebBrowser Tools. New York: Neal Schuman, 2002.Clayberg, Eric, and Dan Rubel. Eclipse: Building Commercial-QualityPlug-ins. 2nd ed. Upper Saddle River, N.J.: Addison-WesleyProfessional, 2006.Drafahl, Jack, and Sue Drafahl. Plug-ins for Adobe Photoshop: AGuide for Photographers. Buffalo, N.Y.: Amherst Media, 2004.Firefox Add-ons: Common Plugins for Firefox. Available online.URL: https://addons.mozilla.org/en-US/firefox. AccessedAugust 17, 2007.Google Desktop Gadgets [plug-ins] Available online. URL: http://desktop.google.com/plugins/?hl=en. Accessed August 17,2007.Pilgrim, Mark. Greasemonkey Hacks: Tips & Tools for Remixing theWeb with Firefox. Sebastapol, Calif.: O’Reilly, 2005.podcastingPodcasting (from iPod plus broadcasting) lets users subscribeto and automatically download regularly distributedcontent (such as radio broadcasts) over the Internet. Themedia files can be stored on an Apple iPod or other mediaplayer (see music and video players, digital), personalcomputer, or other device (see smartphone). Podcastingbecame popular starting around 2004–05 and has becomewidely used by individuals and organizations.Typically, files to be podcast are put on a Web server. TheURLs for the files and other information (such as episodetitles) is provided in files called feeds, using a format suchas RSS or Atom (see Rss). The user installs client software(such as iPodder), browses the feeds (such as through anonline directory), and decides what to subscribe to. The softwarethen periodically checks the feeds, obtains the URLs ofthe latest files, and downloads them automatically. The softwarecan, if desired, then transfer the downloaded files to aportable media player, such as over a USB connection.ApplicationsThere are many sources of podcasts. News organizationscan provide regular audio or video podcasts as a supplementto regular text material. Podcasting also offers a wayfor a small news organization or independent journalist tobuild an audience using equipment as simple as a microphoneand perhaps a video camera. Podcasts also providea way for political organizations to keep in touch with supporters(and perhaps supply them with talking points). Anysource of periodically distributed audio or video can be acandidate for podcasting. These include class lectures, corporatecommunications, and even religious services.Further ReadingGeoghegan, Michael W., and Dan Hlass. Podcast Solutions: TheComplete How-To Guide to Getting Heard around the World.Berkeley, Calif.: Apress, 2005.Juice: The Cross-Platform Podcast Receiver. Available online.URL: http://juicereceiver.sourceforge.net/. Accessed November7, 2007.King, Kathleen P., and Mark Gura. Podcasting for Teachers: Using aNew Technology to Revolutionize Teaching and Learning. Charlotte,N.C.: Information Age Publishing, 2007.Mack, Steve, and Mitch Ratcliffe. Podcasting Bible. Indianapolis:Wiley, 2007.Morris, Tee, and Evo Terra. Podcasting for Dummies. Hoboken,N.J.: Wiley, 2006.Podcast Alley. Available online. URL: http://www.podcastalley.com/. Accessed November 7, 2007.Podcasting News. Available online. URL: http://www.podcastingnews.com/.Accessed November 7, 2007.pointers and indirectionThe memory in a computer is accessed by numbering the successivestorage locations (see addressing). When a programmerdeclares a variable, the compiler associates its name witha location in available memory (see variable). If the variableis used in an expression, when the expression is evaluated,the variable’s name is replaced by its current value—that is,with the contents of the memory location associated with thevariable. Thus, the expression Total + 10 is evaluated as “thecontents in the address associated with Total” plus 10.Sometimes, however, it is useful to have the generalcapability to access memory locations without assigningexplicit variables. This is done through a special type ofvariable called a pointer. The only difference between pointersand regular variables is that the value stored in a pointeris not the data to be ultimately used by the program. Rather,it is the address of that data. Here are some examples fromC, a language that famously provides support for pointers:Int MyVar;Int *MyPtr;integer// Declare a regular variable// Declare a pointer to an// (int) variableMyVar = 10; // Set the value of MyVarto 10MyPtr = &MyVar; // Store the address ofMyVar in// the pointer MyPtrIn C, an asterisk in front of a variable name indicatesthat the variable is a pointer to the type declared. In the

376 pointers and indirectionA pointer is a variable whose value is an address location. HereMyPtr holds the address 101.second line above, therefore, MyPtr is a pointer to an integervariable. This means that the address of any integer variablecan be stored in MyPtr. The last line uses the & (ampersand)to represent the address of the variable MyVar. Therefore, itstores that address in MyPtr.Examining the lines above, one sees that the variableMyVar has the value 10. The pointer variable MyPtr has thevalue of whatever machine address contains the contentsof the variable MyVar. In an expression, putting an asteriskin front of a pointer name “dereferences” the pointer. Thismeans that it returns not the address stored in the pointer,but the value stored at the address stored in the pointer (seethe diagram). Therefore if one writes:AnotherVar = * MyPtr;What is the value of AnotherVar? The answer is thecurrent value of MyVar (whose address had been stored inMyPtr)—that value, as assigned earlier, is 10.The general concept of storing the address of anothervariable in a variable is called indirection, or indirectaddressing. It was first used in assembly language to workwith index registers—special memory locations in a processorthat store memory addresses.Uses for PointersAlthough the concept may seem esoteric, pointers have anumber of uses. For example, suppose one has a buffer(perhaps storing video graphics data) and one wants tocopy it from one area to another. One could declare the bufferto be an array (see array) and then reference each element,or memory location and copy it. However, this wouldbe rather awkward. Instead, one can declare a pointer, set itto the starting address of the buffer, and then simply use aloop to increment the pointer, pointing in turn to each locationin the buffer.A similar approach applies to strings in C and relatedlanguages. A string of characters in C is declared as anarray of char. In an array, the name of the array is actuallya pointer to the first data location. It is therefore easy tomanipulate strings by getting their starting address by referencingthe name and then using one or more pointers tostep through the data locations. For example, the followingfunction copies the contents of one string into another:strcpy(char *s1,char *s2){while (*s2)*s1++ = *s2++;}The function takes two strings, s1 and s2, declared aspointers to char. It then steps (increments) them (usingthe ++ operator) so that the value in each location in s2 iscopied into the corresponding location in s1. The loop exitswhen the value at s2 is 0 (null), indicating that the end ofstring marker has been reached.Another common use for pointers is in memory allocation.Typically, a program requests memory by giving thememory allocation function a pointer and the amount ofmemory requested. The function allocates the memory andthen returns the starting address of the new memory in thepointer, so the program knows how to access that memory.Pointers are also useful for passing a “bulky” variablesuch as a data record to a procedure or function. Suppose,for example, a program needs to pass a 65,000 byte recordto a procedure for printing a report. If it passes the actualrecord, the system has to make a copy of the whole record,tying up memory. If, instead, a pointer to the record is used,only the address is passed. The procedure can then accessthe record at that address without having to make a copy.In C and some other languages it is even possible tohave a pointer that points to another pointer. A commoncase is an array of strings, such asChar Form [80] [20];representing a form that has 20 lines of 80 characters. Eachline is an array of characters and the form as a whole is thus“an array of arrays of characters.” Therefore, to dereference(get the value of) a character one would first dereferencethe line, and then the column.Problems with PointersPointers may be useful, but they are also prone to causingprogramming problems. The simplest one is failing todistinguish between a pointer and its value. For example,suppose one writes:Total = Total + MyPtr;intending to add the value of the variable pointed to byMyPtr to Total. Unfortunately, the asterisk (dereferencingoperator) has been inadvertently omitted, so what getsadded to Total is the machine address stored in MyPtr!Another problem comes when a pointer is used to allocatememory, the memory is later deallocated, but thepointer is left pointing to it.Because pointers can potentially access any location inmemory (or at least attempt to), some computer scientistsview them as more dangerous than useful. It’s true thatmost things one might want to do with a pointer can beaccomplished by alternative means. One attempt to tamepointers is found in C++, which offers the “reference” datatype. A reference is essentially a constant pointer that onceassigned to a variable always dereferences that variable and

political activism and the Internet 377cannot be pointed anywhere else. Java has gone even furtherby not including traditional pointers at all.Further ReadingJensen, Ted. “A Tutorial on Pointers and Arrays in C.” Availableonline. URL: http://home.netcom.com/~tjensen/ptr/pointers.htm. Accessed August 17, 2007.Parlante, Nick. “Pointers and Memory.” Available online. URL:http://cslibrary.stanford.edu/102/PointersAndMemory.pdf.Accessed August 17, 2007.Sebesta, Robert W. Concepts of Programming Languages. 8th ed.Boston: Pearson Addison-Wesley, 2007.Soulle, Juan. “Pointers [in C++].” Available online. URL: http://www.cplusplus.com/doc/tutorial/pointers.html. AccessedAugust 17, 2007.political activism and the InternetAlthough newspapers and particularly television remain themost popular sources used by voters to obtain informationabout candidates and issues, reports by the Pew Internet &American Life Project found that online media was usedby about a third of American voters in the 2006 midtermelections, and about 15 percent used it as their primaryinformation source. (The latter rate was about 35 percentamong young people who had access to broadband Internetconnections at home.) The researchers also found thatabout half of the online users had sought information notavailable elsewhere, while 41 percent believed that newspapersand television did not provide them with all the informationthey wanted.It is true that much of the political information usersfind online is news that originated with mainstream printor broadcast news outlets. However, a growing role is alsobeing played by blogs, issue-oriented Web sites, or sitescreated by candidates themselves, including profiles on theMySpace social networking site.A surprising number of people who look to the Internetfor political information participate actively, with about aquarter engaging in blogs or other online postings, whetherexpressing their own opinions or forwarding e-mail orreposting material. As users become more active (see usercreatedcontent), they are even becoming part of “official”debates, as in 2007 when primary candidates wereasked questions submitted as 30-second YouTube videos.Advantages and Pitfalls for CandidatesFor political candidates and campaigns, the Internet is amixed blessing. Advantages include:• can reach a large number of people at relatively lowcost• can bypass a possibly indifferent mainstream mediaand reach people directly• provides ways to organize and motivate supporters(see blogs and blogging, podcasting, and socialnetworking)• allows for easier fund-raising, including potentiallymillions of small donationsThe first major candidate to put together a campaignbased on these principles was Howard Dean, who for atime was frontrunner for the 2004 Democratic presidentialnomination. In the run-up to the 2008 race, libertarianRepublican Ron Paul, while barely registering in the polls,startled the mainstream media by raising more than $4 millionin one day from thousands of supporters organized onthe Web.However, there are pitfalls for politicians in the digitalage as well. It is hard to control or coordinate self-organizedactivists, who may adopt positions that contradict the candidate’sstated platform or engage in intemperate attacks.(In 2007 a video “mashup” by a Barack Obama supporterportraying Hillary Clinton as “big brother” in the famous1984 Apple Macintosh commercial led to denials that theObama campaign had anything to do with it.)Further, the legions of independent bloggers virtuallyguarantee that “stumbles” that might have been missed orignored by traditional media will be featured in blogs ordisplayed on YouTube for millions to ponder. (An examplewas Virginia senator George Allen, whose use of an obscureracial epithet macaca may have cost him reelection in 2006when it was captured by a video blogger.) It is unclearwhether the intense 24-hour scrutiny will force candidatesto become ever more tightly scripted in their public activitiesso as to avoid “macaca moments.”Some critics also suggest that the Internet may actuallyweaken democracy in some ways. Because of the increasingability to personalize or customize what news one seesand whom one converses with, people could end up beingsimply confirmed in their beliefs and isolated from largerdialog. Extremist groups already use Web sites not only torecruit people, but to keep followers motivated and focusedon their issues, while in effect filtering out opposing views.The creation of such isolated constituencies, able to chooseto see only the kinds of things that make them comfortable,could be bad for democracy. (This could be called a form ofself-censorship, as opposed to outwardly imposed censorship,as in China—see censorship and the Internet.) Onthe other hand, the sheer amount and variety of informationavailable may make it hard for people to cut themselvesoff in this way.Despite these misgivings, the importance of the Webfor political activism and campaigns is clear. No campaign,whether political or issue advocacy, can afford not to have aquality Web site and staff who are adept at the new media andforms of communication, expression, and social networking.Further ReadingChadwick, Andrew. Internet Politics: States, Citizens, and New CommunicationTechnologies. New York: Oxford University Press,2006.Garofoli, Joe. “Blogger Fest a Magnet for Liberal Politicos.” SanFrancisco Chronicle, July 29, 2007, p. A1. Available online.URL: http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/07/29/MNGRVR91RU1.DTL. Accessed November 8, 2007.Guynn, Jessica. “Growing Internet Role in Election.” San FranciscoChronicle, June 4, 2007, p. C-1. Available online. URL: http://sfgate.com/cgi-bin/article.cgi?f=/chronicle/archive/2007/06/04/BUGI6Q5L181. DTL. Accessed November 8, 2007.

378 popular culture and computingHogarth, Paul. “Hillary, Obama and the YouTube Election.” Beyond-Chron, March 21, 2007. Available online. URL: http://www.beyondchron.org/news/index.php?itemid=4322. Accessed November8, 2007.Jakoda, Karen A. B., ed. Crossing the River: The Coming of Age ofthe Internet in Politics and Advocacy. Philadelphia: Xlibris,2005.Nagourney, Adam. “Internet Injects Sweeping Change into U.S. Politics.”New York Times, April 2, 2006, p. 1 ff. Available online. URL:http://www.nytimes.com/2006/04/02/washington/02campaign.html?_r=1&or ef=slogin. Accessed November 8, 2007.Rainie, Lee, and John Horrigan. “Election 2006 Online.” Pew Internet& American Life Project, 2007. Available online. URL:http://www.pewinternet.org/pdfs/PIP_Politics_2006.pdf.Accessed November 8, 2007.TechPresident: Personal Democracy Forum. Available online.URL: http://www.techpresident.com/. Accessed November 8,2007.popular culture and computingComputer technology first came to public consciousnesswith the wartime ENIAC and the first commercial machinessuch as Univac in the early 1950s. The war had shown thedestructive side of new technologies (particularly atomicpower), but corporate and government leaders were soonpromoting their beneficial prospects. Just as atomic energyadvocates promised to provide power that was abundant,cheap, and clean, the computer, or “giant brain” was toutedfor its ability to solve problems that had been beyondhuman capabilities.Ominous MachinesHowever, the computer, too, had its shadow in the popularconsciousness. With their mysterious flashing lightsand white-coated programmer/priests, mainframe computerswere often seen as modern embodiments of the “madscientist” trope, as in the movie Colossus: The Forbin Project(1970), where American and Soviet supercomputersjoined forces to take over the world. Artificial intelligencealso usurped humanity in the more mystical 2001: A SpaceOdyssey (1968).On the domestic front, the mainframe computer alsobecame a symbol of misgivings about the bureaucraticstate and corporate conformity. The romantic comedy filmDesk Set, featuring Katharine Hepburn as a beleagueredcorporate librarian, at first seems to confirm these fears,only to reveal that the computer had been misunderstoodand would bring about a happier future for all. (IBM, incidentally,provided much of the technical support for thefilm.)The counterculture of the 1960s seemed much less sanguineabout the digital future. To many of the generation ofactivists starting with the Free Speech Movement in 1964,computers were the tools of the military-industrial complex,and computing facilities were sometimes picketed oreven physically attacked.However, a computer-savvy wing of the counterculturewas also rising (see hackers and hacking). Activistsbegan to see the machines as a tool for community organizationand communication, as in 1973 with CommunityMemory, the first computer bulletin board system, accessedby teletype terminals.Getting PersonalBy the late 1970s the personal computer had arrived.On the one hand, PCs would seem not to fit the mainframestereotype. After all, the desktop machines aresmall and designed to be accessible helpers in everydaylife and work. Still, they could be connected to networksand perhaps used to take over the Pentagon’s doomsdayweapons—as in the movie War Games (1983). As fearof what malicious or criminal hackers could do took amore practical turn in the 1990s, such movies as The Netand Sneakers created a higher-tech incarnation of the spythriller. Finally, the series of movies beginning with TheMatrix extrapolated from the ultrarealistic movie effectsand games of the coming century to raise the question ofwhether consensus reality could actually be a huge computersimulation.Meanwhile, the figure of the computer “geek” or “nerd”has become a staple character in movies and TV shows—clever, socially inept, but indispensable for keeping themodern world running. In some eyes, the entrepreneurialsuccess of Silicon Valley and the dot-coms placed Bill Gatesand his colleagues in the same mold as Thomas Edison andHenry Ford a century earlier.Digitization of CultureBy the turn of the new century the network that had beenportrayed as the domain of hackers and spies had becomethe all-pervasive World Wide Web. Today computers andthe Internet are not only reflected in American popular culture—theyare profoundly reshaping it. Computer games(particularly see online games) have become vast, persistentsocial worlds, as are sites like MySpace and Facebook(see social networking).With the blending of formerly distinct media (see digitalconvergence) and the fluid sharing and re-creationof images (see user-created content and mashups),the digital world now permeates mainstream culture—or,one might say, the culture itself has become digitized.Meanwhile the line between fact and fiction, creator andviewer, expert and amateur has become increasinglyblurred.Further ReadingFishwick, Marshall William. Probing Popular Culture: On and Offthe Internet. Binghamton, N.Y.: Haworth Press, 2004.Friedman, Ted. Electric Dreams: Computers in American Culture.New York: NYU Press, 2005.King, Brad, and John Borland. Dungeons and Dreamers: The Rise ofComputer Game Culture from Geek to Chic. Emeryville, Calif.:McGraw-Hill/Osborne, 2003.“Machines (and more) in Movies, Books and Music.” BerkshirePublishing Group. Available online. URL: http://www.berkshirepublishing.com/HumanComputerInteractionAndPopCulture/list.asp. Accessed August 17, 2007.Nelson, Theodore H. Computer Lib/Dream Machines: You Can andMust Understand Computers Now. Chicago: Nelson, 1974.(Expanded, reprinted by Microsoft Press, 1987).

PostScript 379Polsson, Ken. “Personal Computer References in Pop Culture.”Available online. URL: http://www.islandnet.com/~kpolsson/comppop/. Accessed August 17, 2007.portalThe legion of new World Wide Web users who went onlinein the mid-1990s could easily navigate and “surf” the Web,using browsers such as Netscape and Internet Explorer (seeWeb browser). However, the lack of a reliable starting pointand a systematic way to find information often led to frustration.Search engines such as AltaVista and Lycos (see searchengine) provided some help, but there was no single guidethat could present the most useful information at a glance.Meanwhile, in 1994, two graduate students, Jerry Yangand David Filo, had begun to circulate an organized listingof their favorite Web sites by e-mail. When the list provedvery popular, they decided they could make a business outof providing a Web site that could serve as a topical guideto the Web. The result was Yahoo!, the most successful ofwhat would come to be called Web portals (see Yahoo).Yahoo! and other portals such as MSN (Microsoft Network),Excite, American Online (AOL), and Lycos generallyprovide a listing organized by topic and subtopic. Forexample, the general topic “Computers and Internet” inYahoo! is divided into many subtopics such as communicationsand networking, hardware, software, and so on. Manytopics are further subdivided until, at the bottom, there is alist of actual Web links that can be clicked upon to take theuser directly to the relevant site.The advantage of using a portal over using a searchengine is that the links on a portal have generally beenselected for quality, relevance, and usefulness. The disadvantageis the flip side of that selectivity: The links mayreflect the tastes, agenda, or commercial interests of theportal developers and thus exclude important points ofview. When seeking to learn more about a subject, manyresearchers therefore both work “inward” from a portal and“outward” via a search engine (see online research).To gain a competitive edge and raise revenue, portalstypically include a considerable amount of advertising.Some portals also charge companies for being includedor featured in listings or displays. General-purpose portalsusually also contain such information as current news,stock prices, weather, and other timely information in anattempt to become their user’s default page. Portals (particularlyYahoo!) have also sought to become more attractive(and profitable) by including such services as travel,financial services, games, and auctions.Some portals emphasize particular approaches to information.For example, About.com goes beyond simply listinglinks to providing extensive guides to hundreds of subjectsin a sort of newsletter format. There are also portalsdesigned to serve particular constituencies, such as professionalgroups, industries, or hobby or interest groups.Companies can also create “enterprise portals” that canhelp employees keep in touch with developments and shareinformation. Such portals often serve as the Web-basedinterface to the corporate local area network (LAN).As with other information content providers, commercialportal developers have struggled to obtain enough revenueto keep up with the need to expand and compete in newareas. It is unclear whether the market will support morethan a handful of large consumer portals in the long run,but both commercial and specialized portals have becomean important part of the way most people access the Web.Further ReadingAbout.com. Available online. URL: http://www.about.com.Accessed August 17, 2007.Angel, Karen. Inside Yahoo!: Reinvention and the Road Ahead. NewYork: Wiley, 2002.“Frequently Asked Questions about Portals (FAQs).” Traffick.Available online. URL: http://www.traffick.com/article.asp?aID=9. Accessed August 17, 2007.Hock, Randolph. Yahoo! to the Max: An Extreme Searcher Guide.Medford, N.J.: Information Today, 2005.Kastel, Berthold. Enterprise Portals for the Business and IT Professional.Sarasota, Fla.: Competitive Edge International, 2003.Linwood, Jeff, and Dave Minter. Building Portals with the Java PortletAPI. Berkeley, Calif.: Apress, 2004.Sullivan, Dan. Proven Portals: Best Practices for Planning, Designing,and Developing Enterprise Portals. Upper Saddle River, N.J.:Addison-Wesley Professional, 2003.Utvich, Michael, Ken Milhous, and Yana Beylinson. 1 Hour WebSite: 120 Professional Web Templates and Skins to Let You CreateYour Own Web Sites—Fast. Hoboken, N.J.: Wiley, 2007.Yahoo! Available online. URL: http://www.yahoo.com. AccessedAugust 17, 2007.PostScriptEarly computer printers were limited to one or a fewbuilt-in fonts, either stamped on typewriter style keys ondaisy wheels, or stored as patterns in the printer’s software(with dot matrix printers). In the mid-1970s, whenXerox researchers were developing the laser printer, theyrealized they needed an actual programming language thatcould describe fonts, graphics, and other elements thatcould be printed on the more versatile new printers. PARCresearchers developed InterPress; meanwhile two of them,John Warnock and Chuck Geschke, founded their owncompany in 1982 (see Adobe Systems). They then createda more streamlined version of InterPress that they calledPostScript. The first printer to include built-in PostScriptcapability was Apple’s LaserWriter, in 1985. PostScript soonbecame the standard for a burgeoning industry (see desktoppublishing).Because PostScript is an actual programming language(for a somewhat similar language, see Forth), softwaresuch as word processors can include functions that turna text document into a PostScript document, ready forprinting. A PostScript interpreter in the printer (or even inanother application) interprets the PostScript commandsto re-create the document. The commands specify rasters(combinations of straight lines and curves), which canbe scaled and transformed to provide the specified output,including fonts, which can be enhanced by including“hints” to help the system identify key features. This processoris thus sometimes called a Raster Image Processor(RIP).

380 presentation softwareDeclineBy the late 1990s, however, PostScript was declining inuse. In part this was because of the advent of cheaper inkjetprinters, which used simpler (and cheaper) software.Further, PostScript’s role as a standard format for distributingdocuments has been largely replaced by one of Adobe’sother standards, the Portable Document Format (seePDF). However, PostScript-equipped laser printers are stillfavored for heavy-duty printing jobs, because the documentprocessing can be done in the printer instead of adding tothe burden of the main CPU.Further ReadingAdobe Systems Incorporated. PostScript Language Reference. 3rded. Reading, Mass.: Addison-Wesley, 1999. Available online.URL: http://partners.adobe.com/public/developer/en/ps/PLRM.pdf. Accessed November 8, 2007.———. PostScript Language Tutorial and Cookbook. Upper SaddleRiver, N.J.: Addison-Wesley Professional, 2007. Availableonline. URL: http://www-cdf.fnal.gov/offline/PostScript/BLUEBOOK.PDF. Accessed November 8, 2007.Weingartner, Peter. “A First Guide to PostScript.” Available online.URL: http://www.tailrecursive.org/postscript/postscript.html.Accessed November 8, 2007.presentation softwareWhether at a business meeting or a scientific conference,the use of slides or transparencies has been largely replacedby software that can create a graphic presentation. Generally,the user creates a series of virtual “slides,” which canconsist of text (such as bullet points) and charts or othergraphics. Often there are templates already structured forvarious types of presentations, so the user only needs tosupply the appropriate text or graphics. There are a varietyof options for the general visual style, as well as for transitions(such as dissolves) between slides. Another useful featureis the ability to time the presentation and provide cuesfor the speaker. Finished presentations can be shown on astandard monitor screen (if the audience is small) or outputto a screen projector.Microsoft PowerPoint is an example of presentation software. Such software uses a “slideshow” metaphor in which screens corresponding toslides can be created and arranged on a timeline for playing. Many types of special effects are also available.

printers 381Microsoft PowerPoint is the most widely used presentationprogram. It includes the ability to import Excelspreadsheets, Word documents, or other items created byMicrosoft Office suite applications. The user can switchbetween outline view (which shows the overall structure ofthe presentation) to viewing individual slides or workingwith the slides as a collection.There are a number of alternatives available includingApple’s Keynote and Open Office, which includes a presentationprogram comparable to PowerPoint. Another alternativeis to use HTML Web-authoring programs to createthe presentation in the form of a set of linked Web pages.(PowerPoint and other presentation packages can also converttheir presentations to HTML.) Although creating presentationsin HTML may be more difficult than using aproprietary package and the results may be somewhat lesspolished, the universality of HTML and the ability to runpresentations from a Web site are strong advantages of thatapproach.A number of observers have criticized the general samenessof most business presentations. Some presentationdevelopers opt to use full-fledged animation, created withproducts such as Macromedia Director.Further ReadingImpress: More Power to Your Presentations. Available online. URL:http://www.openoffice.org/product/impress.html. AccessedAugust 17, 2007.Keynote (Apple iWork). Available online. URL: http://www.apple.com/iwork/keynote/. Accessed August 17, 2007.Lowe, Doug. PowerPoint 2007 for Dummies. Hoboken, N.J.: Wiley,2007.Rutledge, Patrice-Anne, Geetesh Bajaj, and Tom Muccolo. SpecialEdition Using Microsoft Office PowerPoint 2007. Indianapolis:Que, 2006.A dot-matrix printer uses an array of pins controlled by solenoids.Each character has a pattern of pins that are pushed against a typewriter-likeribbon to form the character on the paper.printersFrom the earliest days of computing, computer users neededsome way to make a permanent record of the machine’s output.Although results of a program could be punched ontocards or saved to magnetic tape or some other medium, atsome point data has to be readable by human beings. Thisfact was recognized by the earliest computer and calculatordesigners: Charles Babbage (see Babbage, Charles)designed a printing mechanism for his never-finished computing“engine,” and Williams Burroughs patented a printingcalculator in 1888.Typewriter-Like PrintersThe large computers that first became available in the 1950s(see mainframe) used “line printers.” These devices haveone hammer for each column of the output. A rapidly movingband of type moves under the hammers. Each hammerstrikes the band when the correct character passes by.Printing is therefore done line by line, hence the name. Lineprinters were fast (600 lines per minute or more) but like themainframes they served, they were bulky and expensive.The typewriter offered another point of departure fordesigning printers. A few early computers such as theBINAC (an offshoot of ENIAC) used typewriters riggedwith magnetically controlled switches (solenoids). However,a more natural fit was with the Teletype, inventedearly in the 20th century to print telegraph messages. Sincethe Teletype is already designed to print from electricallytransmitted character codes, it was easy to rig up a circuitto translate the contents of computer data into appropriatecodes for printing. (Since the Teletype could send as well asreceive messages, it was often used as a control terminal forcomputer operators or for time-sharing computer users intothe 1970s.)The daisy-wheel printer was another typewriter-likedevice. It used a movable wheel with the letters embeddedin slim “petals” (hence the name). It was slow (about10 characters a second), noisy, and expensive, but it wasthe only affordable alternative for early personal computerusers who required “letter-quality” output.Dot-Matrix PrintersThe dot-matrix printer, which came into common usein the 1980s, uses a different principle of operation thantypewriter-style printers. Unlike the latter, the dot-matrixprinter does not form solid characters. Instead, it uses an

382 printersarray of magnetically controlled pins (9 pins at first, but 24on later models). Each character is formed by pressing theappropriate pins into a ribbon that pushes into the paper,leaving a pattern of tiny dots.Besides being relatively inexpensive, dot-matrix printersare versatile in that a great variety of character stylesor fonts can be printed (see font), either by loading differentsets of bitmaps. Likewise, graphic images can also beprinted. However, because the characters are made of tinydots, they don’t have the crisp, solid look of printed type.Laser and Ink-jet PrintersThe majority of printers used today use laser or ink-jet technology.Both combine the versatility of dot-matrix with theletter quality of typewriter-style printers. Xerox introducedthe first laser printer in the 1970s, although the technologywas too expensive for most users at first.The laser printer converts data from the computer intosignals that direct the laser beam to hit precise, tiny areasof a revolving drum. The drum is covered with a charged(usually negative) film. The areas hit by the laser, however,A laser printer uses a mirror-controlled laser beam to strike smallspots on a rotating drum (called an OPC or Organic PhotoconductingCartridge) that had been given an electrical charge (usuallypositive) by a corona wire. The spots where the light beam hit aregiven an opposite charge (usually negative). The drum is thencoated with a powdery toner that is charged opposite to the placeswhere the light hit, so the toner clings to the drum to form the patternsof the characters or graphics. A piece of paper is then givena strong negative charge so it can pull the toner off the drum as itpasses under it. Finally, heated rollers called fusers bind the tonerto the paper to form the final image.gain the opposite charge. As the drum continues to revolve,toner (a black powder) is dispensed. Because the toner isgiven a charge opposite to the places where the laser hit, thetoner sticks to those places. Meanwhile, the paper is drawninto the drum. Because the paper is given the same chargeas that produced by the laser beam (but stronger), the toneris pulled from the dots on the drum to the correspondingparts of the paper, forming the characters or graphics. Aheating system then fuses the toner to the paper to makethe image permanent. Meanwhile, the drum is dischargedand the printer is ready for the next sheet of paper.Color laser printers are also available, although they arestill relatively expensive. They work by using four revolutionsof the drum for each sheet of paper, depositing appropriateamounts of black, magenta, cyan, and yellow toner.Laser printers fell in price throughout the 1990s (to$500 or so), but were soon rivaled by a different technology,the ink-jet printer.The ink-jet printer has a print head that contains an inkcartridge for each primary printing color. Each cartridgehas 50 nozzles, each thinner than a human hair. To print,the appropriate nozzles of the appropriate colors are subjectedto electric current, which goes through a tiny resistorin the nozzle. An intense heat results for a few microseconds,long enough to create a tiny bubble that in turn forcesa droplet of ink onto the page.Ink-jet printers are generally slower than lasers, althoughfast enough for most purposes. Although the ink-jet is likethe dot-matrix in producing tiny dots, the dots are muchfiner. With output at up to 2,880 dots per inch, the resultingcharacters are virtually indistinguishable from typeprinting.Using high resolution and special papers, ink-jetprinters can now also produce photo prints comparable tothose created by traditional processes.An interesting offshoot of ink-jet printing technologycan be found in the development by HP of skin patches thatcan deliver controlled doses of drugs using tiny, virtuallypainless needles. The tiny droplets of drugs are transportedin much the same way as ink goes from cartridge reservoirto page.TrendsBy the end of the 1990s, the ink-jet printer was decliningsteeply in price, and today quite capable units canbe purchased for as little as $30 or so. Because of theirgreater speed, however, lasers are still used for higher-volumeprinting operations. “Multifunction” units combiningprinter, scanner, copier, and fax functions are also popularand cost less than a printer alone did only a few years ago.Advocates of office automation have long predicted the“paperless office,” but so far computers and their printershave churned out more paper, not less. However, there aresome trends that might eventually reverse this course. Developmentof practical “electronic books” (page-size displaysthat can hold thousands of pages of text) may reduce theneed for printed output (see e-books and digital libraries).Another possible replacement for printing is “electronicink,” a sheet of paper with charged ink held in suspension.The text or graphics on the page can be changed electroni-

privacy in the digital age 383cally, so it can be reused indefinitely. Finally, the ability toaccess data anywhere on handheld or laptop computers mayalso reduce the need to make printouts.Further ReadingHarris, Tom. “How Laser Printers Work.” Available online. URL:http://home.howstuffworks.com/laser-printer.htm. AccessedAugust 17, 2007.“Printer Buying Guide” (Cnet Reviews). Available online. URL:http://reviews.cnet.com/4520-7604_7-1016838-1.html.Accessed August 17, 2007.“Printers: The Essential Buying Guide.” PC Magazine. Availableonline. URL: http://www.pcmag.com/article2/0,1895,1766,00.asp. Accessed August 17, 2007.Tyson, Jeff. “How Inkjet Printers Work.” Available online. URL:http://www.howstuffworks.com/inkjet-printer.htm. AccessedAugust 17, 2007.privacy in the digital ageQuoted in Fred H. Cate’s Privacy in the Information Age,legal scholar Alan F. Westin has defined privacy as “theclaim of individuals, groups, or institutions to determinefor themselves when, how, and to what extent informationabout themselves is communicated to others.”Since the mid-19th century, advances in communicationstechnology have raised new problems for people seekingto protect privacy rights. During the Civil War telegraphlines were tapped by both sides. In 1928, the U.S. SupremeCourt in Olmstead v. U.S. refused to extend Fourth Amendmentprivacy protections to prevent federal agents from tappingphone lines without a warrant. Almost 50 years later,the court would revisit the issue in Katz v. U.S. and rulethat telephone users did have an “expectation of privacy.”The decision also acknowledged the need to adapt legalprinciples to the realities of new technology.In the second half of the 20th century the growing useof computers would raise two basic kinds of privacy problems:surveillance and misuse of data.Surveillance and EncryptionSince much sensitive personal and business informationis now transmitted between or stored on computers, suchinformation is subject to new forms of surveillance or interception.Keystrokes can be captured using surreptitiouslyinstalled software and e-mails can be intercepted from serversor a user’s hard drive. Many employers now routinelymonitor employees’ computer activity at work, includingtheir use of the World Wide Web. When this practice ischallenged, courts have generally sided with the employer,accepting the argument that the computers at work exist forbusiness purposes, not private communications, and thusdo not carry much of an expectation of privacy. Employers,however, have been encouraged to spell out their employeemonitoring or surveillance policies explicitly. Outside theworkplace, some protection is offered by the ElectronicCommunications Privacy Act (ECPA), passed in 1986.Shadowy accounts about a secret system called Echelonhave suggested that the National Security Agency has inplace a massive system that can intercept worldwide communicationsranging from e-mail to cell phone conversations.Apparently, rooms full of supercomputers can siftthrough this torrent of communication, looking for keywords that might indicate a threat to the United States or itsallies. (Much communication is in “clear” text; the ability ofthe government to crack strong encryption is unclear.)Technology can be used to penetrate privacy, but it canalso be used to safeguard it (see encryption). Public keyencryption programs such as Pretty Good Privacy (PGP)can encode text so that it cannot be read without a veryhard-to-crackkey. The U.S. government, whose agenciesenjoyed powerful surveillance capabilities, initially foughtto suppress the use of encryption, but a combination ofunfavorable court decisions and the ability to spread softwareacross the Internet has pretty much decided the battlein favor of encryption users.In the aftermath of the terrorist attacks of September11, 2001, the federal government pressed for expanded surveillancepowers, some of which were granted in the USAPATRIOT Act of 2001. (The Foreign Intelligence SurveillanceAct [FISA] regulates wiretapping of U.S. persons toobtain foreign intelligence information, requiring that awarrant be obtained from a secret court. In 2008 after revelationsthat the administration was engaging in warrantlessdomestic surveillance outside of FISA, Congress passedan amendment that required FISA permission to wiretapAmericans living abroad.) Computerized surveillance andidentification systems (see biometrics) are also likely to beexpanded in airports in other public places as part of the“War on Terrorism.”Information PrivacyMany privacy concerns arise not from the activities of spyor police agencies, but from the potential for the misuse ofthe many types of personal information now collected bybusinesses or government agencies. As far back as 1972, theAdvisory Committee on Automated Personal Data Systemsrecommended the following standards to the secretary ofthe Department of Health, Education, and Welfare:1. There must be no personal data record-keeping systemswhose very existence is secret.2. There must be a way for an individual to find outwhat information about him/her is on record andhow it is used.3. There must be a way for an individual to correct oramend a record of identifiable information abouthim/her.4. There must be a way for an individual to preventinformation about him/her that was obtained forone purpose from being used or made available forother purposes without his/her consent.5. Any organization creating, maintaining, using, ordisseminating records of identifiable personal datamust guarantee the reliability of the data for theirintended use and must take precautions to preventmisuse of the data.The Federal Privacy Act of 1974 generally implementedthese principles with regard to data maintained by federal

384 procedures and functionsagencies. Later, federal laws have attempted to address particulartypes of information, including school records, medicalrecords, and video rentals.However, much of the information collected from peopleresults from commercial transactions or other interactionswith businesses, particularly via the Internet. Althoughencrypted processing systems have reduced the chance thata credit card number submitted to a store will be stolen, socalledidentity thieves may be able to obtain credit reportsunder false pretenses or collect enough information abouta person from various databases (including Social Securitynumbers). With that information, the thief can take outcredit cards in the person’s name and run up huge bills (seeidentity theft and phishing and spoofing). While thedirect financial liability from identity theft is capped, thepsychological impact and the effort required for victims torehabilitate their credit standing can be considerable. In afew cases the same techniques have been used by stalkers,sometimes with tragic consequences.The ability of Web sites to track where a visitor clicksby means of small files called “cookies” has also disturbedmany people (see cookies). As with the recording ofpurchase information by supermarkets and other stores,businesses justify the practice as allowing for targetedmarketing that can provide consumers with informationlikely to be of interest to them. (Many e-mail addresses arealso gathered to be sold for use for unsolicited e-mail—seespam.) An even more intrusive technique involves the surreptitiousinstallation of software on the user’s computerfor purposes of displaying advertising content or gatheringinformation. In turn, programmers have distributed freeutilities for identifying and removing such “adware” or“spyware.”While such consumer tracking is not as dangerous asidentity theft, it feels like an invasion of privacy to manypeople as well as a source of insecurity, particularly becausethere are as yet few regulations governing such practices.However, in response to such concerns many businesseshave put “privacy statements” on their Web sites, explainingwhat information about visitors will be collected andhow it may be used. Businesses that meet standards for disclosureof their privacy practices can also display the seal ofapproval of organizations such as TRUSTe.Many privacy advocates, however, believe that self-regulationis not sufficient to truly protect consumer privacy.They support strong new regulations, including “optin”provisions that would require businesses to receiveexplicit permission from the consumer before collectinginformation.Privacy and Pervasive ComputingBeyond the Web and e-commerce, new challenges to privacyare emerging (see ubiquitous computing). In themovie Minority Report, stores instantly mine data aboutapproaching consumers and project personalized holographicads in front of their eyes. While that technologyis happily not here yet, many of the component piecesare (see data mining and RFID). Add global positioning(GPS) tracking to the mix, and another important partof privacy is threatened: “locational privacy.” Certainlyone can envisage situations where knowing not only whosomeone is but where they are can increase vulnerabilityto abuse.In response to these pervasive threats to privacy, manyadvocates continue to push for regulation of data gatheringand ways to hold people legally responsible for misuse ofpersonal information. However, some writers such as sciencefiction writer and futurist David Brin argue that thebattle for privacy is already lost, but the battle for transparencyand mutual accountability may still be won—if thewatched can watch the watchers.Further ReadingBrin, David. The Transparent Society. Reading, Mass.: Addison-Wesley, 1998.Cate, Fred H. Privacy in the Information Age. Washington, D.C.:Brookings Institution, 1997.Electronic Frontier Foundation. Available online. URL: http://www.eff.org. Accessed August 17, 2007.Electronic Privacy Information Center. Available online. URL:http://www.epic.org. Accessed August 17, 2007.Henderson, Harry. Privacy in the Information Age (Library in aBook). 2nd ed. New York: Facts On File, 2006.Hunter, Richard. World without Secrets: Business, Crime and Privacyin the Age of Ubiquitous Computing. New York: Wiley2002.Monmonier, Mark. Spying with Maps: Surveillance Technologies andthe Future of Privacy. Chicago: University of Chicago Press,2002.Solove, Daniel. The Digital Person: Technology and Privacy in theInformation Age. Rev. ed. New York: NYU Press, 2006.procedures and functionsFrom the earliest days of programming, programmers andlanguage designers realized that it would be very useful toorganize programs so that each task to be performed by theprogram had its own discrete section of code. After all, a programwill often have to perform the same task, such as sortingor printing data, at several different points in its processing.Instead of writing out the necessary code instructions eachtime they are needed, why not write the instructions just onceand have a mechanism by which they can be called upon asneeded? Such callable program sections have been known asprocedures, subroutines, or subprograms.The simplest sort of subroutine is found in assembly languagesand early versions of BASIC or FORTRAN. In BASIC,for example, a GOSUB statement contains a line number.When the statement is encountered, execution “jumps” tothe statement with that line number, and continues fromthere until a statement such as RETURN is encountered.For example:10 TOTAL = 1020 GOSUB 4030 END40 PRINT “The total is: ”;50 PRINT TOTAL60 RETURN

programming as a profession 385Here execution jumps from line 20 to line 40. After lines40–60 are executed, the program returns to line 30, whereit ends.Procedures with ParametersThe simple subroutine mechanism has some disadvantages,however. The subroutine gets the information it needs fromthe main part of the program implicitly through the globalvariables that have been defined (see variable). If it needsto return information, it does it by changing the value of oneor more of these global variables. The problem is that manydifferent subroutines may be relying upon the same variablesand at the same time changing them, leading to unpredictableresults. Modern programming practice thereforegenerally avoids using global variables as much as possible.Most high-level languages today (including Pascal, C/C++, Java, and modern versions of BASIC) define subprogramsas procedures that pass information through specifiedparameters. For example, a procedure in Pascal mightbe defined as:Procedure PrintChar (CharNum : integer);This procedure has one parameter, an integer that specifiesthe number of the character to be printed (see charactersand strings).The main program can call the procedure by giving itsname and an appropriate character number. For example:PrintChar (32);The code within the procedure does not work with theparameter CharNum directly. Rather, it receives a copy that itcan use. Thus, the procedure might include the statements:Writeln (‘Character number: ’, CharNum );Writeln (chr (CharNum));The program will print the character number and thenprint the character itself on the next line (for characternumber 32 this will actually be a blank).This typical way of using parameters is called passing byvalue. However, it is possible to pass a parameter to a procedureand have the parameter itself used rather than workingwith a copy. This is called “passing by reference.” Pascal usesthe var keyword for this purpose, while C passes a pointer tothe variable (see pointers and indirection), and C++ andJava prefix the variable name with an ampersand (&). Forexample, suppose one has a C function defined as follows:int ByTwo (int * Val){Val = Val * 2;}In the following statements in the calling program:Int Value, NewValue;Value = 10;NewValue = By Two (Value);NewValue would be set to 20 because the actual variableValue has been multiplied by two inside the ByTwo function.FunctionsA function is a procedure that returns its results as a valuein place of the function name in the calling statement. Forexample, a function in C to raise a specified number to aspecified power might be defined like this:int Power (int base, int exp)(C and related languages don’t use a keyword like Pascal’sprocedure or function because in C all procedures arefunctions.)This definition says that the Power function takes twointeger parameters, base and exp, and returns an integervalue.Suppose somewhere in the program there are the followingstatements:Int Base = 8;Int Dimensions = 3;Size = Power (Base, Dimensions);The variable Size will receive the value of Power (8, 3) or 512.Although the syntax for using procedures or functionsvaries by language, there are some principles that are generallyapplicable. The type of data expected by a procedureshould be carefully defined (see data types). Modern compilersgenerally catch mismatches between the type of datain the calling statement and what is defined in the proceduredeclaration. Procedures should also be checked forunwanted “side effects,” which they can minimize by notusing global variables.Procedures and functions relating to a particular taskare often grouped into separate files (sometimes called unitsor modules) where they can be compiled and linked into aprogram that needs to use them (see library, program).Object-oriented languages such as C++ think of proceduresin a somewhat different way from the examplesshown here. While a traditional program sees proceduresas blocks of code to be invoked for various purposes, anobject-oriented program sees procedures as “methods” orcapabilities of the program’s various objects (see objectorientedprogramming).Further Reading“Introduction to Python: Functions.” Available online. URL: http://www.penzilla.net/tutorials/python/functions/. Accessed August17, 2007.Kernighan, Brian W., and Dennis M. Ritchie. The C ProgrammingLanguage. 2nd ed. Englewood Cliffs, N.J.: Prentice Hall, 1988.“Procedures and Functions” [in VBScript]. Available online. URL:http://www.functionx.com/vbscript/Lesson06.htm. AccessedAugust 17, 2007.Sebesta, Robert W. Concepts of Programming Languages. 8th ed.Boston: Pearson Addison Wesley, 2007.“Subroutines” [in Perl]. Available online. URL: http://www.comp.leeds.ac.uk/Perl/subroutines.html. Accessed August 17, 2007.programming as a professionAll computer applications depend upon the ability to directthe machine to perform instructions such as fetching orstoring data, making logical comparisons, or performing

386 programming as a professioncalculations. Although practical electronic computers firstbegan to be built in the 1940s, it took considerable time forprogramming to emerge as a distinct profession. The firstprogrammers were the computer designers themselves, followedby people (often women) recruited from clerical personswho were good at mathematics. With machines likeENIAC, programming was more like setting up a complicatedpiece of factory machinery than like writing. Switchesor plugboards had to be set, and numeric instruction codespunched on cards to instruct the machine to move eachpiece of data from one location to another or to perform anarithmetic or logical operation.Two factors led to greater recognition for the art or craftof programming. First, as more computers were built andput to work for various purposes, more programmers wereneeded, as well as more attention to their training and management.Second, as programs became larger and more complex,a number of high-level languages such as COBOL andFORTRAN came into use (see programming languages).Besides making it easier to write programs, having just afew languages in widespread use made skills more readilytransferable from one computer installation to another. Andas with any profession, programming developed bodies ofknowledge and practice.At the same time, advances in language developmentwould raise a recurrent question: Are professional programmersreally necessary? Since FORTRAN looked a lot likeordinary mathematical notation, couldn’t scientists andengineers just write the programs they need without hiringspecialists for the job? Similarly, some enthusiasts ledmanagers to think that with COBOL accountants (or evenmanagers) could write their own business programs.Sometimes part-time or “amateur” programming didprove to be practicable, particularly for scientists who foundthat writing a quick FORTRAN routine to solve a problemwas easier than trying to explain the problem to a professionalprogrammer. However, the professional programmer’sjob was never really in danger. Businesspeople wereless inclined to try to learn COBOL and entrust somethinglike the company’s payroll processing to ad hoc efforts. Inaddition, the programs that controlled the operation of thecomputer itself, which became known as operating systems,required both arcane knowledge and the ability to design,verify, test, and debug increasingly complex systems (seesoftware engineering).Development of PracticeIn response to this growing complexity, computer scientistsapproached the improvement of programming practice onseveral levels. New languages developed in the 1960s and1970s featured well-defined control structures, data types,and procedure calls (see Algol, Pascal, C, data types,loop, and structured programming.) The managementof programming teams and the factors affecting productivitywere examined by pioneers such as Frederick Brooks,author of The Mythical Man-Month, and IBM sponsoredworkshops and study groups.While many mainframe business programmers continuedto write and maintain programs written in the olderlanguages (such as COBOL), starting in the 1970s a newgeneration of systems and applications programmers usedC and worked in a different environment—campus minicomputersrunning UNIX. Unlike the hierarchical, systematicapproach of the “mainframe culture,” the minicomputerprogrammers tended toward a decentralized but cooperativeapproach (see open-source movement and hackersand hacking).When the personal computer revolution began to arriveat the end of the 1970s, much of the evolution of programmingculture would be recapitulated. Since early microcomputersystems had very limited memory, programmerswho wanted to get useful work out of machines such as theApple II had to work mainly in assembly language or writequick and dirty programs in a limited dialect of BASIC. Thehobbyists and early adopters often knew little about theacademic world of computer science and software engineering,but they were good at wringing the most out of eachclock cycle and byte of memory.As personal computers gained in power and capabilitythrough the 1980s, programmers were able to use higherlevellanguages such as C. Applications such as word processors,spreadsheets, and graphics programs became morecomplex, and programmers had to work in larger teams liketheir mainframe counterparts.At the same time, the sharp demarcation between programmerand user became less distinct with the personalcomputer. Many users who were not professional programmersused applications software that included programmablefeatures, such as spreadsheets and simple data bases (seemacro and scripting language). New languages such asVisual Basic let even relatively inexperienced programmersplug in user interfaces and other components and createuseful programs (see programming environment).Each sector of programming seems to go through acycle of improvisation and innovation followed by standardizationand professionalization. Just as the earlyENIAC programmers evolved into the organized hierarchyof corporate programming departments, the individualsand small groups who wrote the first personal computersoftware evolved into large teams using sophisticated softwareto track to the modules, versions, and developmentsteps of major programming projects. Similarly, when theexplosion of the World Wide Web starting in the mid-1990sbrought a new demand for people who could code HTML,CGI, and Java, much of the most interesting work was doneby individuals and small companies. But if history repeatsitself, the Internet applications field will undergo the sameprocess of professionalization, with increasingly elaboratestandards and expectations (see certification of computerprofessionals).Throughout the history of programming, visionarieshave announced that the time was coming when most ifnot all programming could be automated. All a person willhave to do is give a reasonably coherent description of thedesired results and the required program will be coded bysome form of artificial intelligence (see expert systems,genetic algorithms, and neural network). But whileusers have now been given the ability to do many things

programming environment 387that formerly required programming, it seems there is stilla demand for programmers who can move the bar anotherstep higher. The profession continues to evolve without anysigns of impending extinction.Further ReadingBrooks, Frederick. The Mythical Man-Month, Anniversary Edition:Essays on Software Engineering. Reading, Mass.: Addison-Wesley,1995.Ceruzzi, Paul. A History of Modern Computing. Cambridge, Mass.:MIT Press, 1998.Henderson, Harry. Career Opportunities in Computers and Cyberspace.2nd ed. New York: Facts On File, 2004.Kohanski, Daniel. Moths in the Machine: The Power and Perils ofProgramming. New York: St. Martin’s Press, 2000.Ullmann, Ellen. Close to the Machine: Technophilia and its Discontents.San Francisco: City Lights Books, 1997.programming environmentThe first programmers used pencil and paper to sketch outa series of commands, or punched them directly on cardsfor input into the machine. But as more computer resourcesbecame available, it was a natural thought that programscould be used to help programmers create other programs.The availability of Teletype or early CRT terminals on timesharingsystems by the 1960s encouraged programmers towrite simple text editing programs that could be used tocreate the computer language source code file, which in turnwould be fed to the compiler to be turned into an executableprogram (see terminal and text editor). The assemblersand BASIC language implementations on the first personalcomputers also included simple editing facilities.More powerful programming editors soon evolved, particularlyin academic settings. One of the best known isEMACS, an editor that contains its own LISP-like languagethat can be used to write macros to automatically generateprogram elements (see LISP and macro). With the manyother utilities available in the UNIX operating system, programmerscould now be said to have a programming environment—aset of tools that can be used to write, compile,run, debug, and analyze programs.More tightly integrated programming environmentsalso appeared. The UCSD “p-system” brought together aprogram editor, compiler, and other tools for developingPascal programs. While this system was somewhat cumbersome,in the mid-1980s Borland International released (andsteadily improved) Turbo Pascal. This product offered whatbecame known as an “integrated development interface”or IDE. Using a single system of menus and windows, theAs the name suggests, Microsoft Visual Basic provides a visual programming environment in which the controls that make up a program’s userinterface can be placed on a form. Various properties (characteristics) of the controls can then be set, and program code is then written andattached to govern how the objects will behave.

388 programming languagesprogrammer could edit, compile, run, and debug programswithout leaving the main window.The release of Visual Basic by Microsoft a few yearslater brought a full graphical user interface (GUI). VisualBasic not only ran in Windows, it also gave programmersthe ability to design programs by arranging user interfaceelements (such as menus and dialog boxes) on the screenand then attaching code and setting properties to controlthe behavior of each interface object. This approach wassoon extended by Microsoft to development environmentsfor C and C++ (and later, Java) while Borland releasedDelphi, a visual Pascal development system. Today visualprogramming environments are available for most languages.Indeed, many programming environments canhost many different languages and target environments.Examples include Microsoft’s Visual Studio .NET and theopen-source Eclipse, which can be extended to new languagesvia plug-ins.Modern programming environments help the programmerin a number of ways. While the program is being written,the editor can highlight syntax errors as soon as they’remade. Whether arising during editing or after compilation,an error message can be clicked to bring up an explanation,and an extensive online help system can provide informationabout language keywords, built-in functions, datatypes, or other matters. The debugger lets the programmertrace the flow of execution or examine the value of variablesat various points in the program.Most large programs today actually consists of dozensor even hundreds of separate files, including header files,source code files for different modules, and resources suchas icons or graphics. The process of tracking the connections(or dependencies) between all these files, which usedto require a list called a makefile can now be handled automatically,and relationships between classes in object-orientedprograms can be shown visually.Researchers are working on a variety of imaginativeapproaches for future programming environments. Forexample, an interactive graphical display (see virtualreality) might be used to allow the programmer to ineffect walk through and interact with various representationsof the program.Further ReadingBurd, Barry. Eclipse for Dummies. Hoboken, N.J.: Wiley, 2004.Hladni, Ivan. Inside Delphi 2006. Plano, Tex.: Wordware Publishing,2006.Kernighan, Brian W., and Rob Pike. The UNIX Programming Environment.Englewood Cliffs, N.J.: Prentice Hall, 1984.Parsons, Andrew, and Nick Randolph. Professional Visual Studio2005. Indianapolis: Wiley, 2006.programming languagesThere are many ways to represent instructions to be carriedout by a computer. With early machines like ENIAC,programs consisted of a series of detailed machine instructions.The exact movement of data between the processor’sinternal storage (registers) and internal memory had to bespecified, along with the appropriate arithmetic operations.The evolution of a few major programming languages through fivedecades. There are actually hundreds of different programming languagesthat have seen at least some use in the past 50 years.This lowest level, least abstract form of programming languagesis hardest for humans to understand and use.The first step toward a more symbolic form of programmingis to use easy-to-remember names for instructions(such as ADD or CMP for “compare”) as well asto provide labels for storage locations (variables) andsubroutines (see procedures and functions). The fileof symbolic instructions (called source code) is read bya program called an assembler (see assembler), whichgenerates the low-level instructions and actual memoryaddresses to be used by the program. Because of its abilityto closely specify machine operations, assembly languageis still used for low-level hardware control or whenefficiency is at a premium.Most languages in use today are higher-level. Themainstream of programming languages consists of languagesthat are procedural in nature. That is, they specifya main set of instructions that are executed in sequence,although the program can branch off (see branchingstatements) or repeat a series of statements until a conditionis satisfied (see loop). A program can also calla set of instructions defined elsewhere in the program.Constant or variable data is declared to be of a certaintype such as integer or character (see data types) beforeit is used. There are also rules that determine what partsof a program can access what data (see variable). Forexamples of procedural languages, see Algol, BASIC, C,COBOL, FORTRAN, and Pascal.A variant of procedural languages is the object-orientedlanguage (see object-oriented programming). Such languages(see C++, Java, and Smalltalk) still use sequentialexecution and procedures, but the procedures are “packaged”together with relevant data into objects. In order todisplay a picture, for example, the program will call upona particular object (created from a class of such objects) toexecute its display function with certain parameters such aslocation and dimensions.

project management software 389Nonprocedural LanguagesAlthough the bulk of today’s software is written using procedurallanguages, there are some important languages constructedusing quite different paradigms. LISP, for example,is a powerful language used in artificial intelligence applications.LISP is written by putting together layers of functionsthat carry out the desired processing (see nonprocedurallanguages, LISP, and functional languages). There arealso “logic programming” languages, of which Prolog isbest known (see Prolog). Here a chain of logical steps isconstructed such that the program can traverse it to findthe solution of a problem.Context and Change inProgramming LanguagesBecause of the amount of effort it takes to truly mastera major programming language, most programmersare fluent in only a few languages and developers tendto standardize on one or two languages. The store oftried-and-true code and lore built up by the programmingcommunity tends to make it disadvantageous to radicallychange languages. Thus, FORTRAN and COBOL,although more than 40 years old, are still in considerableuse today. C, which is about 30 years old, has been graduallysupplanted by C++ and Java, but the latter languagesrepresent an object-oriented evolution of C, intentionallydesigned to make it easy for programmers to make thetransition. (Smalltalk, which was designed as a “pure”object-oriented language, never achieved widespread usein commercial development.)Similarly, when programmers had to cope with parallelprocessing (programs that can have several threads of executiongoing at the same time), they have tended to favor “parallelized”versions of familiar languages rather than whollynew ones (see concurrent programming and parallelprocessing).While the basic elements of computer languages tendto persist in the same recognizable forms, the way programmersexperience their use of languages has changedconsiderably through the use of modern visual integrateddevelopment environments (see programming environment).A variety of languages have also been designed fortasks such as data management, interfacing Web pages, andsystem administration (see scripting languages, awk,Perl, PHP, and Python).Further ReadingBergin, Thomas J., and Richard G. Gibson, eds. History of ProgrammingLanguages-II. Reading, Mass.: Addison-Wesley/ACMPress, 1996.Sebesta, Robert W. Concepts of Programming Languages. 8th ed.Boston: Pearson Addison-Wesley, 2007.project management softwareWhether a project involves only a few people in the samedepartment or thousands of people and several years, thereis a variety of software to help managers plan and monitorthe status of their projects.At the simplest level, PIM software (see personalinformation manager) can be used by an individual tomonitor simple personal projects. Such software generallyincludes the ability to record the description, priority, duedate, and reminder date for a task.Project management software is generally used toplan larger projects involving many persons or teams. Acomplex project must first be broken down into tasks.(Large projects often have subprojects as an intermediateentity.) Next, dependencies must be taken into account.For example, the user testing program for a softwareproduct can’t begin until a usable preliminary (“alpha”or “beta”) version of the program is available. The various“resources” assigned to a subproject or task mustalso be tracked, including personnel and number of hoursassigned and budget allocations. In tracking personnelassigned to a project, their availability (who is on vacationand who is assigned to what location) must also beconsidered.Once the scheduling and priorities are arranged, theinevitable divergences between what was planned and whatis actually happening must be monitored. Good projectmanagement software provides many tools for the purpose.Available charts and reports often include:• Gantt charts that use bars to show the duration andpercentage of completion of the various overlappingsubprojects or tasks.• PERT (Program Evaluation and Review Technique)charts that show each subproject or task as a rectangular“node” with information about the task. Theconnections between nodes show the relationships(dependencies) between the items. PERT charts areusually used at the beginning stages of planning.• Analysis tools that show critical paths and bottlenecks(places where one or more tasks falling behindmight threaten large portions of the project). Generally,the more preceding items a task is dependent on,the more likely that task is to fall behind.• Tools for estimating the probability for completionof a given task based on the probabilities of tasks itis dependent on, as well as other factors such as thelikelihood of certain resources becoming available.• A system of alerts or “stoplights” that show slowdowns,potential problems, or areas where work hasstopped completely. These can be set to be triggeredwhen various specified conditions occur.• Integration between project management and budgetreporting so tasks and the project as a whole can bemonitored in relation to budget constraints.• Integration between the project management softwareand individual schedules kept in PIM software such asMicrosoft Outlook or in handheld computers (PDAs)such as the PalmPilot.• Integration between project management and softwarefor scheduling meetings.

390 PrologGiven the scope and pace of today’s business, scientific, andother projects, project management software is often a vitaltool. However, using too elaborate a project tracking systemfor a relatively small and well-defined project may diverttime and energy away from the work itself. Fortunately, awide variety of project management programs are available,ranging from full-fledged products such as MicrosoftProject or Primavera Project Planner to simpler sharewareor free products.Further ReadingMarmel, Elaine. Microsoft Office Project 2007 Bible. Indianapolis:Wiley, 2007.Muir, Nancy C. Microsoft Office Project 2007 for Dummies. Hoboken,N.J.: Wiley, 2007.Open Workbench: Open-Source Project Scheduling for Windows.Available online. URL: http://www.openworkbench.org/.Accessed August 17, 2007.“Project Management Software.” Wikipedia. Available online.URL: http://en.wikipedia.org/wiki/Project_management_software. Accessed August 17, 2007.PrologSince the 1950s, researchers have been intrigued by thepossibility of automating reasoning behavior, such as logicalinference (see artificial intelligence). A number ofdemonstration programs have been written to prove theoremsstarting from axioms or assumptions. In 1972, Frenchresearcher Alain Colmerauer and Robert Kowalski at EdinburghUniversity created a logic programming languagecalled Prolog (for Programmation en Logique) as a way ofmaking automated reasoning and knowledge representationmore generally available.A conventional procedural program begins by definingvarious data items, followed by a set of procedures formanipulating the data to achieve the desired result. A Prologprogram, on the other hand, begins with a set of facts(axioms) that are assumed to be true. (This is sometimescalled declarative programming.)For example, the fact that Joe is the father of Bill wouldbe written:Father (Joe, Bill).The programmer then defines logical rules that apply tothe facts. For example:father (X, Y) :- parent (X, Y), is male (X)grandfather (X, Y) :- father (X, Z), parent(Z, Y)Here the first assertion says that a person X is the fatherof Y if he is the parent of Y and is male. The second assertionsays that X is Y’s grandfather if he is the father of aperson Z who in turn is a parent of Y.When a program runs, it processes queries, or assertionswhose truth is to be proven. Using a process calledunification, the Prolog system looks for facts or rules thatapply to the query and attempts to create a logical chainleading to proving the query is true. If the chain breaks(because no matching fact or rule can be found), the system“backtracks” by looking for another matching fact or rulefrom which to attempt another chain.Prolog aroused considerable interest among artificialintelligence researchers who were hoping to create a powerfulalternative to conventional programming languages forautomating reasoning. This interest was further spurredby the Japanese Fifth Generation Computer Program of the1980s, which sought to create logical supercomputers andmade Prolog its language of choice. Although some suchmachines were built, the idea never really caught on. However,Borland International (makers of the highly successfulTurbo Pascal) released a Turbo Prolog that made thelanguage more accessible to students using PCs, although itused some nonstandard language extensions.Despite its commercial success being limited, Prologhas been used in a number of areas of artificial intelligenceresearch. Its rules-based structure is naturally suitedfor expert systems, knowledge bases, and natural languageprocessing (see expert systems and knowledge representation).It can also be used as a prototyping languagefor designing systems that would then be recoded in conventionallanguages for speed and efficiency.Further ReadingBratck, Ivan. Prolog Programming for Artificial Intelligence. 3rd ed.Reading, Mass.: Addison-Wesley, 2000.Clocksin, W. F., and C. S. Mellish. Programming in Prolog: Usingthe ISO Standard. 5th ed. New York: Springer, 2003.Fisher, J. R. “Prolog: Tutorial.” Available online. URL: http://www.csupomona.edu/~jrfisher/www/prolog_tutorial/contents.html. Accessed August 17, 2007.Sterling, Leon, and Ehud Shapiro. The Art of Prolog: Advanced ProgrammingTechniques. 2nd ed. Cambridge, Mass.: MIT Press,1994.SWI-Prolog [free Prolog for Windows, Linux, and Mac OS]. Availableonline. URL: http://www.swi-prolog.org/. AccessedAugust 17, 2007.pseudocodeBecause humans generally think on a higher (or moreabstract) level than that provided by even relatively highlevelprogramming languages such as BASIC or Pascal, itis sometimes suggested that programmers use some formof pseudocode to express how the program is intended towork. Pseudocode can be described as a language that ismore natural and readable than regular programming languages,but sufficiently structured to be unambiguous. Forexample, the following pseudocode describes how to calculatethe cost of wall-to-wall carpet for a room:Get room length (in feet)Get room widthMultiply length by width to get area (insquare feet)Get price of carpet per square footMultiply price/sq. foot by area to get totalcost.Pseudocode generally includes the basic control structuresused in programming languages (see branching

psychology of computing 391statements and loop) but is not concerned with smalldetails of syntax. For example, this pseudocode mightdetermine whether to charge sales tax for an online purchase:Get customer’s state of residenceIf state is “CA” thenTax = Price * .085Total = Price + TaxEnd IfOnce the pseudocode has been written and reviewed,the statements can be recoded in the programming languageof choice. For example, the preceding example mightlook like this in C:If (state == “CA”) {Tax = Price * .085;Total = Price + Tax;}The term pseudocode can also be applied to “intermediatelanguages” that provide a generic, machine-independentrepresentation of a program. For example, in the UCSD Pascalsystem the language processor generates a “p-code” thatis turned into actual machine language by an interpreterwritten for each of the different types of computer supported.Today Java takes a similar approach.Further ReadingBailey, T. E., and Kris Lundgaard. Program Design with Pseudocode.3rd ed. Pacific Grove, Calif.: Brooks/Cole, 1989.Daviduck, Brent. “Introduction to Programming in C++: Algorithms,Flowcharts and Pseudocode.” Available online. URL:http://www.allclearonline.com/applications/DocumentLibraryManager/upload/program_intro.pdf. Accessed August17, 2007.Gilberg, Richard F,. and Behrouz A. Forouzan. Data Structures: aPseudocode Approach with C++. 2nd ed. Boston: Course Technology,2004.Neapolitan, Richard E. Foundations of Algorithms Using C++Pseudocode. 2nd ed. Sudbury, Mass.: Jones and Bartlett, 1998.psychology of computingComputing is a complex, pervasive, and increasingly vitalhuman activity. It is not surprising that human psychologycan play an important role in many aspects of computeruse.Since the 1960s psychology (in particular see cognitivescience) has contributed to the structuring of interactionbetween computer systems and users (see user interface).It is important to note the significant differences betweenhow computers and humans perceive and process information:computers are extremely fast in processing in a highlystructured setting (e.g., a program). The human brain, onthe other hand, while thousands of times slower, is thusfar greatly superior in coping with loosely structured datathrough pattern recognition, the making of analogies, andgeneralization. A number of researchers (see, for example,Licklider, J. C. R.) have promoted the idea of creating ahuman-computer synergy where the structure of the systemtakes advantage of both the machine’s computationaland data-retrieval abilities and the human user’s ability towork with the larger picture. Such research is continuing asautonomous software (see software agent) and is beginningto interact with Web users.Psychology of CyberspaceThe Internet and its perception as a shared cyberspace addsnew dimensions to the psychology of computing. In fact,the emphasis here is not on computation per se but on therepresentation of ideas and images, communication, socialinteraction, and identity. In particular, pioneering work(see Turkle, Sherry) has illuminated ways in which onlineinteractions affect identity and sense of self—even encouragingthe assumption of multiple identities (see identityin the online world and online games). Indeed, virtualworlds such as Second Life offer new ways to study the formationof communities and social interactions.On the positive side, it has been argued that cyberspacehas encouraged people (particularly adolescents) to experimentwith new identities in a relatively safe environment,but lack of inhibition and experience can lead to riskybehavior such as involvement with sexual predators. Thevery fact that many people (particularly the young) mayspend several hours a day or more immersed in the onlineworld has also led to concerns; some psychologists haveeven suggested that “Internet addiction disorder” (IAD) beincluded as an official mental disorder similar to compulsivegambling. However, as of 2007, the American MedicalAssociation has not recommended that IAD be classifiedas a mental disorder, and the American Society of AddictionMedicine has resisted such a status. Generally, excessiveor inappropriate use of the Internet has been seen as asymptom of more traditional diagnoses such as obsessionor compulsion.Further ReadingCard, Stuart K., Thomas P. Moran, and Allen Newell, eds. The Psychologyof Human-Computer Interaction. Grand Rapids, Mich.:CRC, 1986.Joinson, Adam N. Understanding the Psychology of Internet Behaviour:Virtual Worlds, Real Lives. New York: Palgrave Macmillan,2003.Suler, John. “Computer and Cyberspace Addiction.” InternationalJournal of Applied Psychoanalytic Studies 1 (2004): 359–382.Available online. URL: http://www-usr.rider.edu/~suler/psycyber/cybaddict.html. Accessed November 8, 2007.———. “The Psychology of Cyberspace.” Available online. URL:http://www-usr.rider.edu/~suler/psycyber/psycyber.html.Accessed November 8, 2007.Turkle, Sherry. Life on the Screen: Identity in the Age of the Internet.New York: Touchstone, 1995.———. The Second Self: Computers and the Human Spirit. Twentiethanniversary ed. Cambridge, Mass.: MIT Press, 2005.Wallace, Patricia. The Psychology of the Internet. New York: CambridgeUniversity Press, 1999.Weinberg, Gerald. The Psychology of Computer Programming. Silveranniversary ed. New York: Dorset House, 1998.Whitty, Monica T., and Adrian N. Carr. Cyberspace Romance: ThePsychology of Online Relationships. New York: Palgrave Macmillan,2006.

392 punched cards and paper tapepunched cards and paper tapeIn 1804, the French inventor Joseph-Marie Jacquardinvented an automatic weaving loom that used a chain ofpunched cards to control the pattern in the fabric. A generationlater, a British inventor (see Babbage, Charles)decided that punched cards would be a suitable medium forinputting data into his proposed mechanical computer, theAnalytical Engine.Although Babbage’s machine was never built, by 1890an American inventor was using an electromechanical tabulatingmachine to process census data punched into cards(see Hollerith, Herman). Card tabulating machines wereimproved and marketed by International Business Machines(IBM) throughout the first part of the 20th century. IBMwould also create the 80-column standard punched cardthat would become familiar to a generation of programmers.Later machines included features such as mechanicalsorting, enhanced arithmetic functions, and the ability togroup cards by a particular criterion and print subtotals,counts, or other information about each group. Althoughthese machines were not computers, they did introduce theidea of automated data processing.During the 1930s, a number of companies introducedpunch card tabulators that could work with alphanumericdata (that is, letters as well as numbers). With theseexpanded capabilities, punch card systems could be usedto keep track of military recruits, taxpayers, or customers(such as insurance policy holders). IBM emphasizedthe new machines’ features by calling them “accountingmachines” instead of tabulators.While tabulators and calculators using punched cardsgave a taste of the power of automated data processing,they had a very limited programming ability. For example,they could not make more than very simple comparisons ordecisions, and could not repeat steps under program control(looping). The desire to create a general-purpose dataprocessing system led in the 1940s to the development ofthe electronic computer.When the first computers were developed, it was naturalto turn to the existing punched cards and their machineryfor a medium for inputting data and program instructionsinto the new machines. Because computers contained workingmemory, the program could be stored in its entiretyduring processing, enabling looping, subroutines, and otherways to control processing. Because the amount of availablememory or “core” was severely limited, not much datacould be stored inside the computer. However, complicatedprocessing could be broken into a series of steps where aprogram was loaded and run, the input data cards read andprocessed, and the intermediate results punched onto a setof output cards. The card could then be input to anotherprogram to carry out the next phase.By the 1970s, however, faster and easier to use mediasuch as magnetic tape and disk drives were being employedfor program and data storage. Instead of having to use akeypunch machine to create each program statement, programmerscould type their commands at a terminal, usinga text editor (see programming environment). Even thegovernment began to phase out punched cards. Today some“legacy” punch card systems are maintained, and thereis sometimes a need to read and convert archival data inpunch card form.Ironically, this workhorse of early data processingwould surface again in the U.S. presidential election of2000, when problems with the interpretation of partlypunched “chads” on ballot punch cards would lead togreat controversy.Further ReadingCardamation Company. Available online. URL: http://www.cardamation.com/.Accessed August 17, 2007.Dyson, George. “The Undead: The Little Secret That Haunts CorporateAmerica: A Technology That Won’t Go Away.” Wired7.03 (March 1999): 141–145, 170–172. Available online. URL:http://www.wired.com/wired/archive/7.03/punchcards.html.Accessed August 17, 2007.Philips, N. V. “Everything About Punch Cards.” Available online. URL:http://www.museumwaalsdorp.nl/computer/en/punchcards.html. Accessed August 17, 2007.Province, Charles M. “IBM Punch Cards in the Army.” Availableonline. URL: http://www.geocities.com/pattonhq/ibm.html.Accessed February 9, 2008.PythonCreated by Guido van Rossum and first released in 1990,Python is a relatively simple but powerful scripting language(see scripting languages and Perl). The namecomes from the well-known British comedy group MontyPython.Python is particularly useful for system administrators,webmasters, and other people who have to link variousfiles, data source, or programs to perform their daily tasks.The language currently has a small but growing (and quiteenthusiastic) following.Python dispenses with much of the traditional syntaxused in the C family of languages. For example, the followinglittle program converts a Fahrenheit temperature to itsCelsius equivalent:temp = input(“Farenheit temperature:”)print (temp-32.0) *5.0/9.0Without the semicolons and braces found in C andrelated languages, Python looks rather like BASIC. Alsonote that the type of input data doesn’t have to be declared.The runtime mechanism will assume it’s numeric from theexpression found in the print statement. Python programsthus tend to be shorter and simpler than C, Java, or evenPerl programs. The simple syntax and lack of data typingdoes not mean that Python is not a “serious” language,however. Python contains full facilities for object-orientedprogramming, for example.Python programs can be written quickly and easily bytrying commands out interactively and then converted thescript to bytecode, a machine-independent representationthat can be run on an interpreter designed for each machineenvironment. Alternatively, there are translation programsthat can convert a Python script to a C source file that canthen be compiled for top speed.

Python 393Perl is still a popular scripting language for UNIX andWeb-related applications. Perl contains a powerful builtinregular expression and pattern-matching mechanism, aswell as many other built-in functions likely to be useful forpractical scripting. Python, on the other hand, is a moregeneralized and more cleanly structured language that islikely to be suited for a wider variety of applications, andit is more readily extensible to larger and more complexapplications.Further ReadingLutz, Mark. Learning Python. 3rd. ed. Sebastapol, Calif.: O’Reilly,2007.———. Programming Python. 3rd ed. Sebastapol, Calif.: O’Reilly,2006.Python Programming Language—Official Web site. Available online.URL: http://www.python.org/. Accessed August 17, 2007.Zelle, John M. Python Programming: An Introduction to ComputerScience. Wilsonville, Ore.: Franklin, Beedle & Associates,2004.

Qquality assurance, softwareModern software programs are large and complex, and containmany interrelated modules. If a program is not thoroughlytested before it goes into service, it may containerrors that can result in serious consequences (see risks ofcomputing).In the early days of computing, programmers generallytested their code informally and nonsystematically. Theassumption was that after the program was given to the usersany problems that arose could be fixed through “patches”or replacement versions containing bug fixes. Today, however,it is increasingly recognized that assuring the qualityand reliability of software requires a systematic, comprehensiveprocess that begins when software requirements are firstspecified and continues after the program has been released.Any program is designed to meet the needs of a specifictype of users for specific applications. Therefore, thefirst step must be to make sure that users are able to communicatetheir requirements and that the software engineersunderstand the users’ needs and concerns. Detailedwritten specifications, flowcharts, and other depictions ofthe program can be reviewed by user representatives (seeflowchart and case). The specifications can be furtherexplored by creating a prototype or demonstration of theprogram’s features (see presentation software). Since aprototype can be dynamic and let users have simulatedinteractions with the program, it may reveal usability problemsthat would be hard to spot from charts or documentation.The result of this initial verification process shouldbe that the users agree that the program will do what theyneed and that they will be comfortable using it.In moving from design to implementation (writing theactual code), the developers must first choose an appropriateapproach (see algorithm) and data representation.Choosing an algorithm that is known to be sound is preferable,but if an algorithm must be modified (or a new onedeveloped), developers may be able to take advantage ofmathematical techniques that will suggest, if not totallyprove, the algorithm’s accuracy and reliability.As the programmers write the code, they should try touse best practices (see software engineering). Doing soensures that the code will be readable and organized insuch a way that the source of a problem area can be identifiedeasily, and any “fix” that must be made will be lesslikely to have unforeseen side effects.Developers can also include special code that will facilitatetesting. This code can include assertions—statements that testspecified conditions (such as variable values) at key points inthe program, displaying appropriate messages if the valuesare not within the proper range. Large, complex programscan also include diagnostic modules that give the developers asort of virtual console that they can use to monitor conditionswhile the program is running, or “drill into” particular areasfor closer inspection (see bugs and debugging).Although a certain amount of testing and debugging canand should be done while the code is being written, moreextensive and systematic testing is usually performed aftera preliminary version of the program has been completed.(This is sometimes called an alpha version.) There are twobasic approaches to designing the tests. “White box” tests usethe developer’s knowledge of the code to design test data thatwill test all of the program’s structural features (see proce-394

quantum computing 395dures and functions, branching statements, and loop).The testers may be aided by mathematical analysis that identifies“partitions” or ranges within the data that should resultin a particular execution path being taken through the program.“Fault coverage” tests can also be designed to testfor various specific types of errors (such as input/output,numeric overflow, loss of precision, and so on).A shortcoming of white box tests is that because thetester knows how the program works, he or she may unconsciouslyselect mainly “reasonable” data or situations. (Ithas been observed that users are under no such compulsion!)One way to compensate for this bias is to also perform“black box” tests. These tests assume no knowledge ofthe inner workings of the program. They approach the programfrom the outside, submitting data (or otherwise interactingwith the program) either through the user interfaceor using an automated process that simulates user input.The tester tries to generate as wide a variety of input dataas possible, often by using randomization techniques. Theresult is that the ability of the program to deal with “unreasonable”data will also be tested, and unforeseen situationsmay arise and have to be dealt with.Once this cycle of testing and fixing problems is finished,the program will probably be given to a selectedgroup of users who will operate it under field conditions—that is, in the same sort of environment the program will beused once it is sold or deployed. This process is sometimescalled beta testing. (Game companies have traditionallyrelied upon the willingness of gamers to test a new game inexchange for getting to play it sooner.)The priority (and thus the resources) devoted to testingwill vary according to many factors, including• the complexity of the program (and thus the likelihoodof problems)• the presence of strong competitors who could takeadvantage of significant problems with the program• the potential financial impact or legal exposure frombugs or problems• the ability to “amortize” the costs of developing testingtools and procedures over a number of years asnew versions of the program are developedThe Holy Grail for quality assurance would be to developpowerful artificially intelligent automatic testing programsthat could analyze a program and develop and execute avariety of thorough tests. However, such a program woulditself be very complex, difficult and expensive to develop,and subject to its own bugs. Nevertheless, a number oforganizations (notably, IBM) have devoted considerableattention to the problem.Further ReadingGinac, Frank P. Customer-Oriented Software Quality Assurance.Upper Saddle River, N.J.: Prentice Hall PTR, 1997.Godbole, Nina S. Software Quality Assurance: Principles and Practice.Pangbourne, U.K.: Alpha Science International, 2004.Schulmeyer, G. Gordon, ed. Handbook of Software Quality Assurance.4th ed. Boston: Artech House, 2007.Software QA and Testing Resource Center. Available online. URL:http://www.softwareqatest.com/. Accessed August 17, 2007.quantum computingThe fundamental basis of electronic digital computing is theability to store a binary value (1 or 0) using an electromagneticproperty such as electrical charge or magnetic field.However, during the first half of the 20th century,physicists discovered the laws of quantum mechanics thatapply to the behavior of subatomic particles. An electronor photon, for example, can be said to be in any one of several“quantum states” depending on such characteristics asspin. In 1981, physicist Richard Feynman came up with theprovocative idea that if quantum properties could be “read”and set, a computer could use an electron, photon, or otherparticle to store not just a single 1 or 0, but a number of valuessimultaneously. The simplest case, storing two values atonce, is called a “qubit” (short for “quantum bit”). In 1985,David Deutsch at Oxford University fleshed out Feynman’sideas by creating an actual design for a “quantum computer,”including an algorithm to be run on it.At the time of Feynman’s proposal, the techniques formanipulating individual atoms or even particles had notyet been developed (see nanotechnology), so a practicalquantum computer could not be built. However, duringthe 1990s considerable progress was made, spurred in partby the suggestion of Bell Labs researcher Peter Shor, whooutlined a quantum algorithm that might be used for rapidfactoring of extremely large integers. Since the security ofmodern public key cryptography (see encryption) dependson the difficulty of such factoring, a working quantum computerwould be of great interest to spy agencies.The reason for the tremendous potential power of quantumcomputing is that if each qubit can store two valuessimultaneously, a register with three qubits could storeeight values, and in general, for n qubits one can operate on2 n values simultaneously. This means that a single quantumprocessor might be the equivalent of a huge number ofseparate processors (see multiprocessing). Clearly manyproblems that have been considered not practical to solve(see computability and complexity) might be tackledwith quantum computers.However, the practical problems involved in designingand assembling a quantum computer are expected to be veryformidable. Although scientists during the 1990s achievedthe ability to arrange individual atoms, the precise placementof atoms and even individual particles such as photonswould be difficult. Furthermore, as more of these componentsare assembled in very close proximity, it becomesmore likely that they will interfere with one another, causing“decoherence,” where the superimposed values “break down”to a single 1 or 0, thus causing loss of information. However,some researchers are hopeful that standard mathematicaltechniques (see error correction) could be used to keepthis problem in check. For example, redundant componentscould be used so that even if one decoheres, the others couldbe used to regenerate the information.Another approach is to use a large number of quantumcomponents to represent each qubit. In 1998, Neil Gershenfeldand Isaac L. Chuang reported successful experimentsusing a liquid with nuclear magnetic resonance(NMR) technology. Here each atom in a molecule (for

396 queueIn an empty queue, the head and tail pointers point to the firstcell in memory. To add a value, it is placed at the cell pointed toby the head pointer, and the tail pointer is moved up one cell. If anitem is removed, the head and tail pointers are moved down oneplace. (Note that items must be added at the tail and removed atthe head.)example, chloroform), would represent one qubit, anda large number of molecules would be used, for redundancy.Since each “observation” (that is, setting or readingdata) affects only a few of the many molecules foreach qubit, the stability of the information in the systemis not compromised. However, this approach is limited bythe number of atoms in the chosen molecule—perhaps to30 or 40 qubits.There are many potential applications for quantumcomputing. While the technology could be used to crackconventional cryptographic keys, researchers have suggestedthat it could also be used to generate unbreakablekeys that depend on the “entanglement” of observersand what they observe. The sheer computational powerof a quantum computer might make it possible to developmuch better computer models of complex phenomenasuch as weather, climate, the economy—or of quantumbehavior itself.Further ReadingBurda, Ioan. Introduction to Quantum Computation. Boca Raton,Fla.: Universal Publishers, 2005.Kaye, Phillip, Raymond LaFlamme, and Michele Mosca. An Introductionto Quantum Computing. New York: Oxford UniversityPress, 2007.Quantum Computer News. Science Daily. Available online.URL: http://www.sciencedaily.com/news/computers_math/quantum_computers/. Accessed August 17, 2007.West, Jacob. The Quantum Computer. Available online. URL: http://www.cs.caltech.edu/~westside/quantum-intro.html. AccessedAugust 17, 2007.queueA queue is basically a “line” of items arranged according topriority, much like the customers waiting to check out in asupermarket. Many computer applications involve receiving,tracking, and processing requests. For example, an operatingsystem running on a computer with a single processor mustkeep track of which application should next receive the processor’sattention. A print spooler holds documents waiting tobe printed. A web or file server must keep track of requests forWeb pages, files, or other services. Queues provide an orderlyway to process such requests. Queues can also be used toefficiently store data in memory until it can be processed by arelatively slow device such as a printer (see buffering).As a data structure, a queue is a type of list (see listprocessing). New items are inserted at one end andremoved (deleted) from the other end. This contrasts witha stack, where all insertions and deletions are made at thesame end (see stack). Just as the next person served at thesupermarket is the one at the head of the line, the end of aqueue from which items are removed is called the head orfront. And just as new people arriving at the supermarketline join the end of the line, the part of the queue wherenew items are added is called the tail or rear. Since the firstitem in line is the first to be removed, a queue is called aFIFO (first in, first out) structure.To create a queue, a program first allocates a block ofmemory. It then sets up to pointers (see pointers and indirection).One pointer stores the address of the item at thehead of the queue; the other has the address of the item atthe tail. When the queue starts out, it is empty. This meansthat both the head and tail pointer start out pointing to thesame location.A circular queue works in the same way as a “straight” queue,except that when the last cell in the allotted memory block isreached, the pointer or data “wraps around” to the first cell.

queue 397To add an item, the tail pointer is moved back one locationand the item is stored there. To remove an item, thehead pointer is simply moved back one location. (The datathat had been pointed to by the head pointer can be eitherretrieved or discarded, depending on the application.)In actuality it’s not quite so simple. As items are addedto the queue, the tail pointer keeps moving back in memorywith the head pointer trailing behind as items are deleted. Ifthe queue is sufficiently active (many items are being addedand removed), the queue will end up “crawling” throughmemory somewhat like a worm until all the memory isconsumed.In a real line at the supermarket, as a customer leavesthe checkout stand, each of the persons in line movesup one space. In a computer queue this could be accomplishedby moving each item up one location wheneveran item is removed at the head. However, having to moveall the data items each time one is changed would be veryinefficient. Instead, one could allow the head of the queueto move only up to some specified location. At that point,the head is moved back to the beginning of the memoryblock, and thus the space that had been vacated by thetail as it moved up is reutilized. In effect this wraps thememory around into a circle, so this is called a circularqueue.Further ReadingBrookshear, J. Glenn. Computer Science: An Overview. 6th ed. Reading,Mass.: Addison-Wesley, 2000.Skiena, Steven S. “Priority Queues.” Available online. URL: http://www2.toki.or.id/book/AlgDesignManual/BOOK/BOOK3/NODE130.HTM. Accessed August 17, 2007.Suh, Eric. “The Queue Data Structure.” Available online. URL:http://www.cprogramming.com/tutorial/computersciencetheory/queue.html. Accessed August 17, 2007.

RRAID (redundant array of inexpensive disks)Computer storage is relatively cheap today (see hard disk),but having continued access to data in the event of hardwarefailure is essential to any enterprise. RAID, or redundantarray of inexpensive disks, is a way to turn plentifulstorage into higher reliability and/or speed of access. RAIDworks by turning a group of drives into a single logicalStriping spreads data across several disk drives so that a singlehead movement on each drive can fetch a large amount of data.Mirroring duplicates each sector of data on a second disk drive,ensuring that if one drive fails the data can still be retrieved. Combinationsof both techniques are often used, trading space for reliability(or vice versa).unit; the operating system need not deal with this internalorganization, but simply reads or writes data as usual.To improve reliability, data can be mirrored, or copied totwo or more disks. While the data obviously takes up morespace, the advantage is that the data remains intact andrecoverable if any one drive fails. Further reliability can beachieved by storing redundant data (such as parity bits orHamming codes), to diagnose and fix some disk problems(see error correction and fault tolerance).To achieve greater speed of data access, data can be“striped,” where a file is broken into pieces, with each piecestored on a sector on a different drive. Thus instead of thehead of a single drive having to jump around to multiplesectors to read the data, the heads on all the drives cansimultaneously read many parts of the file, which are thenassembled into the proper order.Levels and CompromisesBy combining mirroring, error correction, and/or striping,different “levels” of RAID can be implemented to suit differentneeds. There are various trade-offs: Striping can increaseaccess speed, but uses more storage space and, by increasingthe number of disks, also increases the chance that one willfail. Implementing error correction can make failure recoverable,but slows data access down because data has to beread from more than one location and compared.The most commonly used RAID levels are:• RAID 0—striping data across disks, higher speed butno error correction; failure of any disk can make dataunrecoverable398

eal-time processing 399• RAID 1—mirroring (data stored on at least two disks),data intact as long as one disk is still operating• RAID 3 and 4—striping plus a dedicated disk for parity(error checking)• RAID 5—striping with distributed parity; data can berestored automatically after a failed disk is replaced• RAID 6—like RAID 5 but with parity distributed sothat data remains intact unless more than two drivesfailIn actuality, RAID configurations can be very complex,where different levels can be “layered” above one another,with each treating the next as a virtual drive, until onegets down to the actual hardware. Although RAID is oftenimplemented using a physical (hardware) controller, operatingsystems can also create a virtual RAID structure insoftware, interposed between the logical drive as seen bythe read/write routines and the physical drives.Although RAID is most commonly used with largeshared storage units (see file server and networkedstorage), with the drastic decline in hard drive prices,simple RAID configurations (such as two mirrored drives)are also appearing in higher-end desktop PCs.Further ReadingLeider, Joel. “How to Select a RAID Disk Array.” Enterprise StorageForum. Available online. URL: http://www.enterprisestorageforum.com/hardware/features/article.php/726491.AccessedNovember 8, 2007.“Redundant Array of Inexpensive Disks (RAID).” PC Guide. Availableonline. URL: http://pcguide.com./ref/hdd/perf/raid/index.htm. Accessed November 8, 2007.random number generationComputer applications such as simulations, games, andgraphics applications often need the ability to generate oneor more random numbers (see simulation and computergames). Random numbers can be defined as numbers thatshow no consistent pattern, with each number in the seriesneither affected in any way by the preceding number, norpredictable from it.One way to get random digits is to simply start with anarbitrary number with a specified number of digits, perhaps10. This first number is called the seed. Multiply the seed bya constant number of the same length, and take that numberof digits off the right end of the product. The result becomesthe new seed. Multiply it by the original constant to generatea new product, and repeat as often as desired. The result isa series of digits that appear randomly distributed as thoughgenerated by throwing a die or spinning a wheel. This typeof algorithm is called a congruential generator.The quality of a random number generator is proportionalto its period, or the number of numbers it can producebefore a repeating pattern sets in. The period for acongruential generator is approximately 2 32 , quite adequatefor many applications. However, for applications such asvery large-scale simulations, different algorithms (calledshift-register and lagged-Fibonacci) can be used, althoughthese also have some drawbacks. Combining two differenttypes of generators produces the best results. The widelyused McGill Random Number Generator Super-Duper combinesa congruential and a shift-register algorithm.Generating a random number series from a single seedwill work fine with most simulations that rely upon generatingrandom events under the control of probabilities(Monte Carlo simulations). However, although the sequenceof numbers generated from a given seed is randomly distributed,it is always the same series of numbers for the sameseed. Thus, a computer poker game that simply used a givenseed would always generate the same hands for each player.What is needed is a large collection of potential seeds fromwhich one can be more or less randomly chosen. If thereare enough possible seeds, the odds of ever getting the sameseries of numbers become vanishingly small.One way to do this is to read the time (and perhaps date)from the computer’s system clock and generate a seed basedon that value. Since the clock value is in milliseconds, thereare millions of possible values to choose from. Anothercommon technique is to use the interval between the user’skeystrokes (in milliseconds). Although they are not perfect,these techniques are quite adequate for games.So-called true random number generators extract randomnumbers from physical phenomena such as a radioactivesource (the HotBits service at Fourmilab in Switzerland)or even atmospheric noise as detected by a radio receiver.For the ultimate in random numbers, researchers havelooked to quantum processes that are inherently random.In 2007 researchers at an institute in Zagreb, Croatia, beganto offer the Quantum Random Bit Generator Service, whichis keyed to unpredictable emissions of photons in a semiconductor.The output of most random number services canbe interfaced with MATLAB and other popular mathematicalsoftware packages.Further ReadingGentle, James E. Random Number Generation and Monte CarloMethods. 2nd ed. New York: Springer, 2004.HotBits: Genuine Random Numbers, Generated by RadioactiveDecay. Available online. URL: http://www.fourmilab.ch/hotbits/. Accessed August 18, 2007.“Introduction to Randomness and Random Numbers.” Availableonline. URL: http://www.random.org. Accessed August 18,2007.real-time processingThere are many computer applications (such as air trafficcontrol or industrial process control) that require that thesystem respond almost immediately to its inputs.In designing a real-time system there are always twoquestions to answer: Will it respond quickly enough mostof the time? How much variation in response time can wetolerate? A system that responds to real-time environmentalconditions (such as the amount of traction or torque actingon a car’s wheels) needs to have a sampling rate and a rateof processing the sampled data that’s fast enough so thatthe system can correct a dangerous condition in time. Theresponsiveness required of course varies with the situation

400 recursionand with the potential consequences of failure. An air trafficcontrol system may be able to take a few seconds betweenprocessing radar samples, but it better get it right in time.Systems like this where real-time response is absolutelycrucial are sometimes called “hard real-time systems.”Other systems are less critical. A streaming audio systemhas to keep its buffer full so it can play in real time,but if it stutters once in a while, no one’s life is in danger.(And since download rates over the Internet can vary formany reasons it’s not realistic to expect too perfect a levelof performance.) A slower “soft real-time system” like abank’s ATM system should be able to respond in tens of seconds,but if it doesn’t, the consequences are mainly potentialloss of customers and revenue. A fairly wide variation inresponse time may be acceptable as long waits don’t occuroften enough to drive away too many customers.To put together the system, the engineer must look atthe inherent speed of the sampling device (such as radar,camera, or simply the keyboard buffer). The speed of theprocessor(s) and the time it takes to move data to and frommemory are also important. The structure, strengths, andweaknesses of the host operating system can also be a factor.Some operating systems (including some versions ofUNIX) feature a guaranteed maximum response time forvarious operating system services. This can be used to helpcalculate the “worst case scenario”—that combination ofinputs and the existing state of the system that should resultin the slowest response.Another approach available in most operating systems isto assign priority to parts of the processing so that the mostcritical situations are guaranteed to receive the attention ofthe system. However, things must be carefully tuned so thateven lower priority tasks are accomplished in an acceptablelength of time.The design of the data structure or database used tohold information about the process being monitored is alsoimportant. In most databases the age of the data is not thatimportant. For a payroll system, for example, it might besufficient to run a program once in a while to weed outpeople who are no longer employees. For a nuclear powerplant, if data is getting too old such that it’s not keepingup with current condition, some sort of alarm or evenautomatic shutdown might be in order. With a system thathas softer constraints (such as an automatic stock tradingsystem), it may be enough to be able to get most trades donewithin a specified time and to gather data about the performanceof the system so the operators can decide whether itneeds improvement.Real-time systems are increasingly important becauseof the importance of the activities (such as air traffic controland power grids) entrusted to them, and because oftheir pervasive application in everything from cars to cellphones to medical monitors (see embedded system andmedical applications of computers). The systems alsotend to be increasingly complex because of the increasinginterconnection of systems. For example, many real-timesystems have to interact with the Internet, with communicationsservices, and with ever more sophisticated multimediadisplay systems. Further, many real-time systems mustuse multiple processors (see multiprocessing), which canincrease the robustness and reliability of the system butalso the complexity of its architecture, and thus the difficultyin determining and ensuring reliability.Further ReadingButtazzo, Giorgio C. Hard Real-Time Computing Systems: PredictableScheduling Algorithms and Applications. 2nd ed. NewYork: Springer, 2005.Cheng, Albert M. K. Real-Time Systems: Scheduling, Analysis, andVerification. Hoboken, N.J.: Wiley, 2002.Resources for Real-Time Computing. TechRepublic. Availableonline. URL: http://search.techrepublic.com.com/search/real-time+computing.html. Accessed August 19, 2007.recursionEven beginning programmers are familiar with the ideathat a series of program statements can be executed repeatedlyas long as (or until) some condition is met (see loop).For example, consider this simple function in Pascal. Itcalculates the factorial of an integer, which is equal to theproduct of all the integers from 1 to the number. Thus factorial5, or 5! = 1 * 2 * 3 * 4 * 5 = 120.Function Factorial (n: integer) : integerBegini: integer;For i = 1 to n doFactorial := Factorial * i;End.If the main program has the line:Writelin (Factorial (5));then the 5 is sent to the function, where the loop simplymultiplies the numbers from 1 to 5 and returns 120.However, it is also possible to have a function call itselfrepeatedly until a specified condition is met. This is calledIn recursion, a procedure calls itself until some defined conditionis met. In this example of a Factorial procedure, F(1) is defined toreturn 1. Once it does, the returned value is plugged into its caller,which then returns the value of 1 * 2 to its caller, and so on.

educed instruction set computer 401recursion, and it allows for some compact but powerfulcoding. A recursive version of the Factorial function in Pascalmight look like this:function Factorial (n:integer) :integerbeginif (n = 1) thenFactorial := 1elseFactorial := Factorial (n - 1) * n;end;Why does this work? An alternative way to define a factorialis to say that the factorial of a number is that numbertimes the factorial of one less than the number. Thus, thefactorial of 5 is equal to 5 * 4! or 5 * 4 * 3 * 2 * 1. But in turnthe factorial of 4 would be equal to 4 * (3 * 2 * 1), and so ondown to the factorial of 1, which is simply 1. Thus, in generalterms the factorial of n is equal to n * factorial (n - 1).What happens if this function is called by the programstatement:Writeln (“Factorial of 5 is ”); Factorial (5)First, the Factorial function is called with the value 5assigned to n. The If statement checks and sees that n isnot 1, so it calls factorial (i.e., itself) with the value of n - 1,or 4. This new instance of the factorial function gets the4, sees that it is not 1, and calls factorial again with n - 1,which is now 4 - 1 or 3. This continues until n is 2, at whichpoint factorial 1 is called. But this time n is 1, so it returnsthe value of 1 rather than calling itself yet again.Now the returned value of 1 replaces the call to Factorial(n - 1) in the preceding instance of Factorial (where nhad been 2). That 1 is therefore multiplied by 2, and 1 *2 = 2 is returned to the preceding instance, where n hadbeen 3. Now that 2 gets multiplied by 3 and returned to theinstance where n had been 4. This continues until we’reback at the first call to factorial 5, where the value of 4 * 3 *2 * 1 now gets multiplied by that 5, giving 120, or factorial5. (See the accompanying diagram for help in visualizingthis process.)A Recursive Sorting AlgorithmIn the preceding example recursion does no more than asimple loop could, but many problems lend themselves morenaturally to a recursive formulation. For example, supposeyou have an algorithm to merge (combine) two lists of integersthat have been sorted into ascending values. The proceduresimply takes the smaller of the two numbers at the frontof the two lists until one list runs out of numbers (any numbersin the remaining list can then simply be included).Using an English-like syntax, one can write a recursiveprocedure to sort a list of numbers by calling itself repeatedly,then using the Merge procedure:Procedure SortBeginIf the list has only one item, returnElseSort the first half of the listSort the second half of the listMerge the two sorted listsEnd IfEnd (Sort)Sort will call itself until one of the lists has only oneitem (which by definition is “sorted”), and the Merge procedurewill build the sorted list.To implement recursion, the run-time system for thelanguage must use an area of memory (see stack) to temporarilystore the values associated with each instance of afunction as it calls itself. Depending on the implementation,there may be a limit on how many levels of recursion areallowed, or on the size of the stack. (However, the plentifulsupply of available memory on most systems today makesthis less of an issue.)The first generation of high-level computer languages(such as FORTRAN and COBOL) did not allow recursion.However, the second generation of procedural languagesstarting around 1960 with Algol, as well as successors suchas Pascal and C do allow recursion. The LISP language(see LISP and functional languages) uses recursivedefinitions extensively, and recursion turns out to be veryuseful for processing the grammars for artificial and naturallanguages (see parsing). Recursion can also be usedto generate interesting forms of graphics (see fractals incomputing).Further ReadingHillis, W. Daniel. The Pattern in the Stone: The Simple Ideas thatMake Computers Work. New York: Basic Books, 1998.McHugh, John. “The Animation of Recursion.” Available online.URL: http://www.animatedrecursion.com/home. AccessedAugust 19, 2007.Roberts, E. S. Thinking Recursively. New York: Wiley, 1986.reduced instruction set computer (RISC)All things being equal, the trend in computer design isto continually add new features. There are several reasonswhy this is the case with computer processors:• to create a “family” of upwardly compatible computers(see compatability and portability)• to make a new machine more competitive with existingsystems, or to give it a competitive advantage• to make it easier to write compilers for popular languages• to allow for more operations to be done with one(or a few) instructions rather than requiring manyinstructionsThere are certainly exceptions to the trend toward complexity.The minicomputer, for example, represented insome ways a simplification of the exiting mainframe design.It didn’t have as many ways of working with memory (seeaddressing) and lacked the multiple input/output “channels”and their separate processors. But once minicomputerswere introduced and achieved success, the same

402 regular expressioncompetitive and other pressures led their designers to startadding complexity.One way processor designers coped with the demandfor more complicated instructions was to give the main processora microprocessor with its own set of simple instructions.When the main processor received one of the complexinstructions, it would be executed by being broken downinto simpler instructions or “microcode” to be executed bythe sub-processor.This approach gave processor designers greater flexibility.It also made things easier for compiler designers,because the compiler could translate higher-level languagestatements into fewer, more complex instructions, leavingit to the hardware with its micro engine to break themdown into the ultimate machine operations. However, italso meant that the processor had to decode and executemore instructions in every processor cycle, making it lessefficient and slower and losing some of the benefits of thefaster processors that were becoming available.In 1975, John Cocke and his colleagues at IBM decidedto build a new minicomputer architecture from the groundup. Instead of using complex instructions and decodingthem with a micro engine, they would use only simpleinstructions that could be executed one per cycle. The clock(and thus the cycle time) would be much faster than forexisting machines, and the processor would use pipeliningso it could decode the next instruction while still executingthe previous one. Similarly, in many cases the next itemof data needed could be fetched at the same time the datafrom the previous step was being written (stored). Thisapproach became known as reduced instruction set computing(RISC), because the number of instructions had beenreduced compared to exiting systems, which then becameknown as complex instruction set computing (CISC).Since the RISC system had only simple instructions,compilers could no longer use many complicated but handyinstructions. The compiler would have to take over the jobof the micro engine and break all statements down intothe basic instructions. It became important that the compilerbe able to generate the optimal set of instructions byanalyzing how data would have to be moved around inthe machine’s registers and memory. In other words, RISChardware gained higher performance through simplificationat the hardware level but at the cost of making compilersmore complicated. Fortunately, both hardware and softwaredesigners were able to meet the challenge and in the processlearn how to get the most out of new technology.RISC would also play a part in the design of the microprocessorsthat began to power personal computers. Forexample, the DEC Alpha, a “pure” RISC chip introducedin 1992, provided a level of power that made it suitable forhigh-performance workstations. Another successful RISCbaseddevelopment has been the SPARC (Scalable ProcessorARChitecture) developed by Sun Microsystems for servers,computer clusters, and workstations.Perhaps the most interesting development, however, hasbeen the gradual application of RISC principles to mainstreamprocessors such as the Intel 80×86 series used inmost personal computers today. Increasingly, the recentPentium series chips, while supporting their legacy of CISCinstructions, are processing them using an inner architecturethat uses RISC principles and takes advantage of pipelining,as well as using more registers and a larger datacache. However, the sheer increase in clock cycle speed andperformance in the newer chips has made the old tradeoffbetween complicated and simple instructions less relevant.Further ReadingDandamudi, Sivarama P. Guide to RISC Processors for Programmersand Engineers: Introduction to Assembly Language Programmingfor Pentium and RISC Processors. New York: Springer, 2005.Knuth, Donald E. MMIX—A RISC Computer for the New Millennium.Vol. 1, fascicle 1 of Art of Computer Programming. UpperSaddle River, N.J.: Addison-Wesley Professional, 2005.regular expressionMany users of UNIX and the old MS-DOS are familiar withthe ability to use “wildcards” to find filenames that matchspecified patterns. For example, suppose a user wants to listall of the TIF graphics files in a particular directory. Sincethese files have the extension .tif, a UNIX ls command or aDOS dir command, when given the pattern *.tif, will matchand list all the TIF files. (One does have to be aware ofwhether the operating system in question is case-sensitive.UNIX is, while MS-DOS is not.)The specification *.tif tells the command “match all fileswhose names consist of one or more characters and that endwith a period followed by the letters tif.” It is one of manypossible regular expressions. (See the accompanying tablefor more examples.) The asterisk here is a “metacharacter.”This means that it is not treated as a literal character, but asa pattern that will be matched in a specified way.Most operating systems that have command processors(see shell) allow for some form of regular expressions, butdon’t necessarily implement all of the metacharacters. UNIXprovides the most extensive use for regular expressions (seeUNIX). UNIX has an operating system facility called globthat expands regular expressions (that is, substitutes forthem whatever matches) and passes them on to the manyUNIX tools or utilities designed to work with regular expressions.These tools include editors such as ex and vi, thecharacter translation utility (tr), the “stream editor” (sed),and the string-searching tool grep. For example, sed can beused to remove all blank lines from a file by specifyingsed ‘s/^$/d’ list.txtThis command finds all lines with no characters (^$) inthe file list.txt and deletes them from the output. Even moreextensive use of pattern-matching with regular expressionsis found in many scripting languages (see scripting languages,awk, and Perl).It is true that most of today’s computer users don’t enteroperating system commands in text form but instead usemenus and manipulate icons (see user interface andMicrosoft Windows). If such a user wants to change oneword to another throughout a word processing document,he or she is likely to open the Edit menu, select Find,

esearch laboratories in computing 403MetacharacterMETACHARACTERS IN REGULAR EXPRESSIONSMeaning. (period) Matches any single character in that position? Matches zero or one of any character* Matches zero or more of the preceding character (thus * matches any number of characters)+ Matches one or more of the preceding character (thus 9+ matches 9, 99, 999, etc.)[ ] Matches any of the characters enclosed by the brackets– Specifies a range of characters. Placing the range in brackets will match any character within therange. For example, [0–9] matches any digit, [A–Z] matches any uppercase character, and [A–Za–z]matches any alphabetic character.\ “Quotes” the following character. If it is a metacharacter, the following character will be treated as anordinary character. Thus \? matches an actual question mark.^Matches the beginning of a line$ Matches the end of a lineand type the “before” and “after” words into a dialog box.However, even in such cases if the user has some familiaritywith regular expressions, more sophisticated substitutionscan be accomplished. In Microsoft Word, for example,a variety of wildcards (i.e., metacharacters) can be usedfor operations that would be hard to accomplish throughmouse selections.Further ReadingFriedl, Jeffrey. Mastering Regular Expressions. 3rd ed. Sebastapol,Calif.: O’Reilly, 2006.Regular Expressions Tutorial, Tools & Languages, Examples,Books & Reference. Available online. URL: http://www.regular-expressions.info/. Accessed August 19, 2007.Stubblebine, Tony. Regular Expression Pocket Reference: RegularExpressions for Perl, Ruby, PHP, Python, C, Java and .NET.Sebastapol, Calif.: O’Reilly, 2007.Watt, Andrew. Beginning Regular Expressions. Indianapolis: Wiley,2005.research laboratories in computingThe value of creating and maintaining environments forlong-term research in computer science and engineeringhas long been recognized by academic institutions, industryorganizations, and corporations.Academic Research InstitutionsArtificial intelligence and robotics have been the focus ofmany academic computer science research facilities (seeartificial intelligence and robotics). They are examplesof areas that show great potential but that demanda substantial investment in long-term research. There aremany research organizations in the AI field, but a few standout as particularly important examples.The Massachusetts Institute of Technology (MIT) ArtificialIntelligence Lab has a wide-ranging program but hasemphasized robotics and related fields such as computervision and language processing.The MIT Media Lab has become well known for workwith new media technologies and the digital and graphicalrepresentation of data. However, in recent years it hasexpanded its focus to the broader area of human-machineinteraction and the pervasive presence of intelligent devicesin the home and larger environment.The Stanford Artificial Intelligence Laboratory (SAIL)played an important role in the development of the LISPlanguage (see LISP) and other AI research. Today Stanford’simportant role in AI is continued by its Robotics Laboratoryand the Knowledge Systems Laboratory. Carnegie MellonUniversity also has a number of influential AI labs andresearch projects.On the international scene Japan has had strong researchprograms in academic and industrial AI, such as the NeuralComputing Center at Keio University and the Knowledge-Based Systems Laboratory at Shizuoka University. There area number of important AI research groups in the UnitedKingdom, such as at Cambridge, Oxford, King’s College,and the University of Edinburgh (where the logic languageProlog was developed).Some of the most interesting research sometimesemerges from outside the main concerns of an institution.The World Wide Web, for example, was developed by TimBerners-Lee (see Berners-Lee, Tim) while he was workingwith the coordination of scientific computing at CERN, thegiant European particle physics laboratory.Corporate Research InstitutionsThe challenging nature of computer applications and thecompetitiveness of the industry have also led a number ofmajor companies to underwrite permanent research institutions.Much corporate-funded research has gone into developingthe basic infrastructure of computing rather than tothe more esoteric topics pursued by academic departments.However, corporations have also funded “pure” researchthat may have little short-term application but can ultimatelylead to new technologies.The concept of the industrial laboratory is often attributedto Thomas Edison, whose famous Menlo Park, NewJersey, facility (founded in 1876) put experimentation anddevelopment of new inventions on a systematic, continuousbasis. Instead of an invention forming the basis for a company,Edison saw invention itself as the core business.

404 reverse engineeringA similar approach motivated the founding of Bell Laboratories.Bell Labs would play a direct role in making moderndigital electronics possible when three of its researchers,John Bardeen, Walter H. Brattain, and William B. Shockleyinvented the transistor in 1947.On the software side, Bell supported the work of ClaudeShannon, whose fundamental theorems of informationtransmission would become a key to the design of the computernetworks (see Shannon, Claude). The developmentof the UNIX operating system at Bell in the early 1970s (seeRitchie, Dennis and UNIX) would provide much of theinfrastructure that would be used for computing at universitiesand other research institutions and ultimately in thedevelopment of the Internet. Similarly, Ritchie and Thompsonalso developed C, the language that together with itsoffshoots C++ and Java would become the most widely usedgeneral-purpose programming languages for the rest of thecentury and beyond.IBM built its first research lab in 1945, beginning anetwork that would eventually include facilities in Switzerland,Israel, Japan, China, and India. IBM research has generallyfocused on core hardware and software technologies,including the development of the first hard drive in 1956and the development of the FORTRAN language by JohnBackus in 1957 (see foRTRAN). Other IBM innovationshave included online commerce (the SABRE airline reservationsystem), the relational database, and the first prototypeRISC (reduced instruction set computer).Xerox is best known for its photocopiers and printers,but in the late 1960s the company decided to try to diversifyits products by recasting itself as developer of a comprehensive“architecture of information” in the office. During the1970s, its Palo Alto Research Center (PARC) invented muchof the technology (such as the mouse, graphical user interface,and notebook computer) that would become familiarto consumers a decade later in the Macintosh and MicrosoftWindows.In 1991, Microsoft, then a medium-sized company,established its Microsoft Research division, which hassince grown to include four laboratories in Redmond,Washington, the San Francisco Bay Area, Cambridge,England, and Beijing. The labs maintain close ties withuniversities, and their research areas have included datamining and analysis, geographic information systems(Terraserver), natural language processing, and computerconferencing and collaboration.The role of government agencies in funding computer-relatedresearch should not be overlooked (seegovernment funding of computer research). TheInternet evolved from a project funded by the Departmentof Defense’s ARPA (Advanced Research ProjectsAgency) in 1968 (see Internet). The network architectureand hardware in turn were developed by a contractor,Bolt, Beranek and Newman (BBN). In the late 1970s,the Defense Department would issue contracts for developmentof the Ada computer language. Other projectsfunded by Defense and other government agencies can befound in areas such as robotics, autonomous vehicles, andmapping systems.Coordinating ResearchTwo large professional organizations for computer scientistsand engineers, the Association for Computing Machinery(ACM) and the Computer Society of the Institute ofElectrical and Electronics Engineers (IEEE), serve as clearinghousesand disseminators of research. The ComputingResearch Association (CRA) brings together more than 200North American university computer science departments,government-funded research institutions, and corporateresearch laboratories. Its goal is to improve the opportunitiesfor and quality of research and education in the computerfield. (For contact information for these and otherselected computer-related organizations, see Appendix IV.)Other Types of ResearchThe social impact of computing technology is also the subjectof considerable ongoing research. Topics include consumerbehavior, the use of media, and sociological analysisof online communities. A particularly useful effort is theextensive surveys and overviews produced by the Pew Centerfor the Internet and American Life project. The computerhardware, software, and e-commerce sectors are ofcourse also the subject of research by economists, expertsin organizational behavior, investment analysts, and so on.Further ReadingComputing Research Association. Available online. URL: http://www.cra.org/. Accessed August 19, 2007.Open Directory Project. Computer Science Research Institutes.Available online. URL: http://www.dmoz.org/Computers/Computer_Science/Research_Institutes/. Accessed August19, 2007.Pew Internet & American Life Project. Available online. URL:http://www.dmoz.org /Computers/Computer_ Science/Research_Institutes/. Accessed August 19, 2007.TRN’s Research Directory: A Worldwide Listing of TechnologyResearch Laboratories. Available online. URL: http://www.trnmag.com/Directory/directory.html. Accessed August 19, 2007.reverse engineeringBack in the days of mechanical clocks, curious kids wouldsometimes take a clock apart to try to figure out how itworked. A few were even able to reassemble the clock correctly—theseyoungsters were likely to become engineers!With software, reverse engineering is the process of “takingapart” software and analyzing its operation without havingaccess to the program code itself. Among other possibilities,reverse engineering may allow one to:• provide equivalent functions without violating copyrightlaws• emulate one operating system within another (seeemulation)• determine a file format so other programs can use itas well (interoperability)• document the operation of a program whose documentationis lost or no longer available• determine whether a competing product violates one’spatents or copyrights

RFID 405TechniquesReverse engineering can be thought of as running the developmentprocess backwards (see software development).Instead of starting with the specification of the system andwriting code, one starts with the operating program andconstructs a detailed description of its organization. Severalgeneral techniques can be used:• disassembly (turning the machine-level code intosomewhat higher-level code with symbolic labels, etc.)(see assembler)• decompilation (which attempts to turn machine codeinto a higher-level language such as C) (see compiler)• systematically supplying data of various types andanalyzing the program’s response (this is especiallyused when analyzing communications protocols)Perhaps the most significant example of reverse engineeringoccurred in the early 1980s when competitorsreverse engineered the built-in code (see BIOS) that controlledthe low-level functions of the original IBM PC, thusenabling the manufacture of legal “clones” by such companiesas Compaq. This was done by creating a “clean room”staffed with engineers who had no involvement with IBMand were not privy to any of the internal secrets of the BIOS.Reverse engineering has been widely used to provideopen-source implementations of formerly proprietary technologies.Examples include Samba (Windows SMB filesharing), Open Office (similar to Microsoft Office), Mono(Windows .NET API), and especially Windows emulatorsfor Linux such as Wine.Generally, under the Digital Millennium Copyright Actof 1998, courts have been sympathetic to reverse engineeringthat enables users to exercise what would be considered“fair use” under copyright laws or to provide morewidespread compatibility with other products. However,reverse engineering may be illegal when the intent is tobypass software “locks” (see copy protection) in order tomake illegal copies, or when the machine code is copied ormanipulated (such as by decompiling).There are a number of ways in which reverse engineering(or similar practices) can be applied to technology otherthan software. Perhaps the most unusual example was thesuccessful reconstruction of an ancient Greek astronomicalcalculator called the Antikythera mechanism. In general,the process of reverse engineering, by spreading knowledgeof how to access and interface systems and provide functionality,ultimately contributes to the development of newtechnology and software.Further ReadingEilam, Eldad. Reversing: Secrets of Reverse Engineering. Indianapolis:Wiley, 2005.James, Dick. “Reverse Engineering Delivers Product Knowledge,Aids Technology Spread.” Available online. URL: http://electronicdesign.com/Articles/Index.cfm?AD=1&ArticleID=11966. Accessed November 11, 2007.Musker, David C. “Reverse Engineering.” Available online. URL:http://www.jenkins-ip.com/serv/serv_6.htm. Accessed November11, 2007.Perry, Mike, and Nasko Oskov. “Introduction to Reverse EngineeringSoftware.” Available online. URL: http://www.acm.uiuc.edu/sigmil/RevEng/. Accessed November 11, 2007.Raja, Vinesh, and Kiran J. Fernandes, eds. Reverse Engineering: AnIndustrial Perspective. New York: Springer, 2008.RFID (radio frequency identification)For some years now people have become used to swipingcredit or debit cards to buy things in stores, or haveused magnetic cards to access transit systems. Increasingly,however, the information needed for identification, whetherof goods in a warehouse or customers in a store, is beingscanned wirelessly using radio frequency identification(RFID) systems.An RFID system uses a tag or card (see smart card)that is able to store and modify information in memory,together with a tiny antenna and transmitter for communicatingthe information.Passive vs. ActivePassive RFID tags have no power supply; the power inducedby the reading signal is used to transmit the response.Because this power is very small, passive tags can only beread at distances from about 4 inches (10 cm) to a few yards(meters), depending on the antenna size and type. The mainadvantage of passive tags is that the lack of a battery makesthem small, lightweight, and inexpensive, making themideal for attaching to merchandise (they have also beenembedded under the skin of pets and, in a few cases, evenpeople). Smart cards for use in transit systems and similarapplications are also passive; the system is activated by“tagging” or bringing the card near the reader.Active RFID tags have their own battery. Their advantageis that they are able to initiate communication withthe reader, and the signal they send is much stronger, morereliable, and with greater range (up to about 1,500 feet[500 m]). The stronger signal allows for communication inrougher environments (such as outdoors for tracking cattleor shipping containers).There is also a sort of hybrid called a semipassive tag. Thisalso has a battery, but only uses it for internal processing, notsending signals. The tag can gather information (such as loggingtemperature) and send it when queried by a reader.Current uses for RFID tags and cards of various typesinclude:• automatic fare payments systems for transit systems• automatic toll payments for bridges and turnpikes• automatic book checkout systems for libraries, whereit reduces repetitive strain injury (RSI) in staff andsimplifies checking shelves• student ID cards• passports (RFID has been included in new U.S. passportssince 2006)• tracking cattle, including determining the origin ofunhealthy animals

406 RFIDParts of an RFID system. Depending on whether the chip is active or passive, the reader can be inches or yards away.• identification chips placed beneath the skin of pets• experimental human RFID implants (pioneered byBritish computer scientist Kevin Warwick) and nowused by VIP customers in a few nightclubs• tracking goods from original shipment to inventory(Wal-Mart now requires its major suppliers to includeRFID labels with shipments)• scientific sensors, such as seismographic instrumentsPrivacy and Security IssuesThe benefits of RFID technology are numerous: betterinventory control (see supply chain management); moresecure passports and other forms of ID; faster, easier accessto transportation systems; and potentially, the avoidance ofA Radio Frequency ID (RFID) “chip” from 3M. RFID is findingmany applications, but has also raised privacy concerns.(3M Corporation)mishaps in hospitals, such as the wrong patient receiving adrug or procedure.However, there are privacy and security concerns thatremain to be fully resolved. The primary threat is thatunauthorized persons could illicitly obtain information ortrack people or goods, for purposes ranging from simplelarceny to identity theft. Privacy rights organizations havealso raised concerns that information about consumer purchasescould be used for unwanted marketing (or sold tothird parties), while information about a library patron’sreading habits could trigger unwarranted governmentinvestigations in the name of fighting terrorism.There is an incentive to produce RFID cards and tagsthat are resistant to unauthorized reading or tampering. Acryptographic protocol can be used such that no informationwill be sent or received unless the reader and tag “know” thecorrect keys. Another possibility is to create a device thatcan “jam” reading attempts in the device’s vicinity, perhapsprotecting a customer’s grocery cart from being scanned.Finally, RFID cards can be put inside in a sleeve of materialthat blocks the signals. However, cryptographic and othersecurity technologies raise the cost of RFID devices and maymake them impracticable for some applications.In September 2006 the National Science Foundationawarded a $1.1 million grant to the RFID Consortium forSecurity and Privacy to study potential risks and safeguardsfor the technology. That same year a group of major corporationstogether with the National Consumers Leaguereleased a draft set of standards and guidelines for bestpractices in using RFID, with broader scope than the existingEPC (electronic product code) standards.Further ReadingEPC Global. Available online. URL: http://www.epcglobalinc.org/.Accessed November 12, 2007.Feder, Barbara. “Guidelines for Radio Tags Aim to Protect BuyerPrivacy.” New York Times, May 1, 2006. Available online.URL: http://query.nytimes.com/gst/fullpage.html?res=9805EFDF113FF932A35756C0A96 09C8B63. Accessed November12, 2007.

Rheingold, Howard 407Glover, Bill, and Himanashu Bhatt. RFID Essentials. Sebastapol,Calif.: O’Reilly, 2006.Newitz, Annalee. “The RFID Hacking Underground.” Wired, May2006. Available online. URL: http://www.wired.com/wired/archive/14.05/rfid.html. Accessed November 12, 2007.“Privacy Best Practices for Deployment of RFID Technology,Interim Draft.” CDT Working Group on RFID, May 1, 2006.Available online. URL: http://www.nclnet.org/advocacy/technology/rfid_guidelines_05012006.htm.Accessed November12, 2007.Sweeney, Partick J., II. RFID for Dummies. Hoboken, N.J.: Wiley,2005.Rheingold, Howard(1947– )AmericanWriterOn his Web site, Howard Rheingold says that he “fell intothe computer realm from the typewriter dimension, thenplugged his computer into his telephone and got suckedinto the net.” A prolific writer, explorer of the interactionof human consciousness and technology, and chronicler ofvirtual communities, Rheingold has helped people from studentsto businesspersons to legislators understand the socialsignificance of the Internet and communications revolution.Born on July 17, 1947, in Phoenix, Arizona, he was latereducated at Reed College in Portland, Oregon, but lived andworked for most of his life in the San Francisco Bay Area.A child of the counterculture, his interests included theexploration of consciousness and cognitive psychology. Hisbooks in this area would include Higher Creativity (writtenwith Willis Harman, 1984), The Cognitive Connections (writtenwith Howard Levine, 1986), and Exploring the Worldof Lucid Dreaming (written with Stephen LaBerge, 1990).In 1994 he updated the Whole Earth Catalog, a remarkableresource book by Stewart Brand that had become a bible forthe movement toward a more self-sufficient and humanscalelife in the 1970s.Rheingold bought his first personal computer, mainlybecause he thought word processing would make his workas a writer easier. In 1983 he bought a modem and was soonintrigued by the thousands of PC bulletin board systemsthat were an important way to share files and ideas in thedays before the World Wide Web (see bulletin board systems).Interacting with these often tiny cyberspace villageshelped Rheingold explore his developing ideas about thenature and significance of virtual communities.In 1985 Rheingold joined The WELL (Whole Earth ’LectronicLink), a unique and remarkably persistent communitythat began as an unlikely meeting place of Deadheads(Grateful Dead fans) and computer hackers. Compared tomost bulletin boards, the WELL was more like the virtualequivalent of the cosmopolitan San Francisco Bay Area.The sum and evaluation of these experiences can befound in what is perhaps Rheingold’s most seminal book,The Virtual Community (1993; revised, 2000), which representsboth a participant’s and an observer’s tour through theonline meeting places that had begun to function as communities(see virtual community). Rheingold chronicledthe romances, feuds (“flame wars”), and growing pains thatmade The WELL seem much like a small town or perhapsan artist’s colony that just happened to be in cyberspace.In addition to The WELL, Rheingold also exploresMUDs (Multi-User Dungeons) and other elaborate onlinefantasy role-playing games, NetNews (also called Usenet)groups, chat rooms, and other forms of online interaction(see conferencing systems and netnews and newsgroups).Rheingold continues to manage the BrainstormsCommunity, a private Web-conferencing community thatallows for thoughtful discussions about a variety of topics.Rheingold saw the computer (and computer networksin particular) as a powerful tool for creating new formsof community. The original edition of his book Tools forThought (1985 and revised 2000), with its description ofthe potential of computer-mediated communications, seemsprescient today after a decade of the Web. Rheingold’s VirtualReality (1991) introduced that immersive technology.Around 1999 Rheingold started noticing the emergenceof a different kind of virtual community—a mobile, highlyflexible, and adaptive one. In his book Smart Mobs, Rheingoldgives examples of groups of teenagers coordinatingtheir activities by sending each other text messages on theircell phones (see flash mobs). Rheingold believes that thecombination of mobile and network technology may be creatinga social revolution as important as that triggered bythe PC in the 1980s and the Internet in the 1990s.In 1996 Rheingold launched Electric Minds, an innovativecompany that tried to offer virtual-community-buildingservices while attracting enough revenue from contractwork and advertising to become self-sustaining and profitablein about three years. He received financing from theventure capital firm Softbank. However, the company failed,and Rheingold came to believe that there was a fundamentalmismatch between the profit objectives of most venturecapitalists and the patience needed to cultivate and grow anew social enterprise. Rheingold then started a more modesteffort, Rheingold Associates.According to Rheingold and coauthor Lisa Kimball, someof the benefits of creating such communities include the abilityto get essential knowledge to the community in timesof emergency, to connect people who might ordinarily bedivided by geography or interests, to “amplify innovation,”and to “create a community memory” that prevents importantideas from getting lost. Rheingold continues to bothcreate and write about new virtual communities, workingthrough such efforts as the Cooperation Commons (a collaborationwith the Institute for the Future). He is also a nonresidentFellow of the Annenberg School for Communication.Rheingold’s writings have garnered a variety of awards.In 2003 Utne Reader magazine gave an Independent PressAward for a blog based on Smart Mobs. That year Rheingoldalso gave the keynote speech for the annual Webby Awardsfor Web-site design.Further ReadingCooperation Commons. Available online. URL: http://www.cooperationcommons.com/. Accessed November 12, 2007.

408 risks of computingHafner, Katie. The Well: A Story of Love, Death & Real Life in theSeminal Online Community. New York: Carol & Graf, 2001.Howard Rheingold [home page]. Available online. URL: http://www.rheingold.com. Accessed November 12, 2007.Kimball, Lisa, and Howard Rheingold. “How Online Social NetworksBenefit Organizations.” Available online. URL: http://www.rheingold.com /Associates/onlinenetworks.html.Accessed November 12, 2007.Rheingold, Howard. Smart Mobs: The Next Social Revolution. NewYork: Basic Books, 2003.———. Tools for Thought: The History and Future of Mind-ExpandingTechnology. 2nd rev. ed. Cambridge, Mass.: MIT Press,2000.———. The Virtual Community: Homesteading on the ElectronicFrontier. Revised ed. Cambridge, Mass.: MIT Press, 2000.[The first edition is also available online. URL: http://www.rheingold.com/vc/book/. Accessed November 12, 2007.]Smart Mobs Blog. Available online. URL: http://www.smartmobs.com/. Accessed November 12, 2007.The WELL Available online. URL: http://www.well.com. AccessedNovember 12, 2007.risks of computingProgrammers and managers of software development aregenerally aware of the need for software to properly dealwith erroneous data (see error handling). They knowthat any significant program will have bugs that must berooted out (see bugs and debugging). Good software engineeringpractices and a systematic approach to assuring thereliability and quality of software can minimize problemsin the finished product (see software engineering andquality assurance, software). However, serious bugs arenot always caught, and sometimes the consequences can becatastrophic. For example, in the Therac 25 computerizedX-ray cancer treatment machine, poorly thought-out commandentry routines plus a counter overflow resulted inthree patients being killed by massive X-ray overdoses. Theoverdoses ultimately occurred because the designers hadremoved a physical interlock mechanism they believed wasno longer necessary.Any computer application is part of a much larger environmentof humans and machines, where unforeseen interactionscan cause problems ranging from inconvenience toloss of privacy to potential injury or death. Seeing thesepotential pitfalls requires thinking beyond the specificationsand needs of a particular project. For many years theUsenet newsgroup comp.risks (and its collected form, RisksDigest) have chronicled what amounts to an ongoing symposiumwhere knowledgeable programmers, engineers, andothers have pointed out potential risks in new technologyand suggested ways to minimize them.Unexpected SituationsA common source of risks arises from designers of controlsystems failing to anticipate extreme or unusual environmentalconditions (or interactions between conditions).This is a particular problem for mobile robots, which unliketheir tethered industrial counterparts must share elevators,corridors, and other places with human beings. For example,a hospital robot was not designed to recognize when itwas blocking an elevator door—a situation that could haveblocked a patient being rushed into surgery. A basic principleof coping with unexpected situations is to try to designa fail-safe mode that does not make the situation worse. Forexample, an automatic door should be designed so that if itfails it can be opened manually rather than trapping peoplein a fire or other disaster.Unanticipated InteractionsThe more systems there are that can respond to externalinputs, the greater the risk that a spurious input might triggeran unexpected and dangerous response. For example,the growing number of radio-controlled (wireless) deviceshave great potential for unexpected interactions betweendifferent devices. In one case reported to the Risks Forum, aSwedish policeman’s handheld radio inadvertently activatedhis car’s airbag, which slammed the radio into him. Severalmilitary helicopters have crashed because of radio interference.Banning the use of electronic devices at certain timesand places (for example, aboard an aircraft that is taking offor landing) can help minimize interference with the mostsafety-critical systems.At the same time, regulations themselves introduce therisk that people will engage in other forms of risky behaviorin an attempt to either follow or circumvent the rule. Forexample, the Japanese bullet train system imposed a stiffpenalty for operators who failed to wear a hat. In one casean operator left the train cabin to retrieve his hat while thetrain kept running unsupervised. This minor incident actuallyconceals two additional sorts of risks—that of automatinga system so much that humans no longer pay attention,and the inability of the system to sense the lack of humansupervision.Unanticipated Use of DataThe growing number of different databases that track eventhe intimate details of individual lives has raised many privacyissues (see privacy in the digital age). Designers andmaintainers of such databases had some awareness of thethreat of unauthorized persons breaking into systems andstealing such data (see computer crime and security).However, most people were surprised and alarmed by thenew crime of identity theft, which began to surface in significantnumbers in the mid- to late-1990s (see identity theft).It turned out that while a given database (such as customerrecords, bank information, illicitly obtained DMVrecords, and so on) usually did not have enough informationto allow someone to successfully impersonate another’sidentity, it was not difficult to use several of these sourcestogether to obtain, for example, the information needed toapply for credit in another’s name. In particular, while mostpeople guarded their credit card numbers, they tended notto worry as much about Social Security numbers (SSN).However, since many institutions use the SSN to indextheir records, the number has become a key for unlockingpersonal data.Further, as more organizations put their records onlineand make them Web-accessible, the ability of hackers, privateinvestigators (legitimate or not), and “data brokerage”

Ritchie, Dennis 409services to quickly assemble a dossier of sensitive informationon any individual was greatly increased. Here we havea case where a powerful tool for productivity (the Internet)also becomes a facilitator for using the vulnerabilities inany one system to compromise others.In an increasingly networked and technologically-dependentworld, the anticipation and prevention of computerrisks has become very important. To the extent companiesmay be legally liable for the more direct forms of risk, thereis more incentive for them to devote resources to risk amelioration.However, many computer-related risks are at leastas much social as technological in nature, and are beyondthe scope of concern of any one company or organization.Social risks ultimately demand a broader social response.Technology itself can be used to help ameliorate technologicalrisks. Artificial intelligence techniques (see expertsystems and neural network) might be used improve theability of a system to adapt to unusual conditions. However,any such programming then becomes prone to bugs andrisks itself.So far, the most successful way to deal with the broadrange of computer risks has been through human collaborationas facilitated by the Internet. Through venues such asthe Risks Forum computer-mediated communications andcollaboration allows for the pooling of human intelligence inthe face of the growing complexity of human inventiveness.Further ReadingComp.risks [access via Google Groups]. Available online. URL:http://groups.google.com/group/comp.risks/topics. AccessedAugust 19, 2007.Glass, Robert L. Software Runaways: Monumental Software Disasters.Upper Saddle River, N.J.: Prentice Hall, 1997.Neumann, Peter G. Computer-Related Risks. Reading, Mass.: Addison-Wesley,1994.Peterson, Ivars. Fatal Defect: Chasing Killer Computer Bugs. NewYork: Vintage Books, 1996.Ritchie, Dennis(1941– )AmericanComputer ScientistTogether with Ken Thompson, Dennis Ritchie developedthe UNIX operating system and the C programming language—twotools that have had a tremendous impact onthe world of computing for three decades.Ritchie was born on September 9, 1941, in Bronxville,New York. He was exposed to communications technologyand electronics from an early age because his father wasdirector of the Switching Systems Engineering Laboratoryat Bell Laboratories. (Switching theory is closely akinto computer logic design.) Ritchie attended Harvard Universityand graduated with a B.S. in physics. However, bythen his interests had shifted to applied mathematics and inparticular, the mathematics of computation, which he laterdescribed as “the theory of what machines can possiblydo” (see computability and complexity). For his doctoralthesis he wrote about recursive functions (see recursion).Together with Ken Thompson, Dennis Ritchie developed the UNIXoperating system and the C programming language, two of themost important developments in the history of computing. (Photocourtesy of Lucent Technologies’ Bell Labs)This topic was proving to be important for the definition ofnew computer languages in the 1960s (see Algol).In 1967, however, Ritchie decided that he had had enoughof the academic world. Without finishing the requirementsfor his doctorate, he started work at Bell Labs, his father’semployer. Bell Labs has made a number of key contributionsto communications and information theory (see researchlaboratories in computing).By the late 1960s, computer operating systems hadbecome increasingly complex and unwieldy. As typified bythe commercially successful IBM System/360, the operatingsystem was proprietary, had many hardware-specific functionsand tradeoffs in order to support a family of upwardlycompatible computer models, and was designed with a topdownapproach.During his graduate studies, however, Ritchie hadencountered a different approach to designing an operatingsystem. A new system called Multics was being designedjointly by Bell Labs, MIT, and General Electric. Multics wasquite different from the batch-processing world of mainframes:It was intended to allow many users to share acomputer. He had also done some work with MIT’s Project

410 roboticsMac. The MIT computer students, the original “hackers” (inthe positive meaning of the term), emphasized a cooperativeapproach to designing tools for writing programs. This,too, was quite different from IBM’s highly structured andcentralized approach.Unfortunately, the Multics project itself grew increasinglyunwieldy. Bell Labs withdrew from the Multics projectin 1969. Ritchie and his colleague Ken Thompson thendecided to apply many of the same principles to creatingtheir own operating system. Bell Labs wasn’t in a mood tosupport another operating system project, but they eventuallylet Ritchie and Thompson use a DEC PDP-7 minicomputer.Although small and already obsolete, the machinedid have a graphics display and a Teletype terminal thatmade it suitable for the kind of interactive programmingthey preferred. They decided to call their system UNIX,punning on Multics by suggesting something that was simplerand better integrated.Instead of designing from the top down, Ritchie andThompson worked from the bottom up. They designed away to store data on the machine’s disk drive (see file), andgradually wrote the necessary utility programs for listing,copying, and otherwise working with the files. Thompsondid the bulk of the work on writing the operating system,but Ritchie did make key contributions such as the idea thatdevices (such as the keyboard and printer) would be treatedthe same way as other files. Later, he reconceived data connectionsas “streams” that could connect not only files anddevices but applications and data being sent using differentprotocols. The ability to flexibly assign input and output, aswell as to direct data from one program to another, wouldbecome hallmarks of UNIX.When Ritchie and Thompson successfully demonstratedUNIX, Bell Labs adopted the system for its internal use.UNIX turned out to be ideal for exploiting the capabilitiesof the new PDP-11 minicomputer. As Bell licensed UNIX tooutside users, a unique community of user-programmersbegan to contribute their own UNIX utilities (see opensourcemovement).In the early 1970s, Ritchie also collaborated with Thompsonin creating C, a streamlined version of the earlier BCPLand CPL languages. C would be a “small” language thatwas independent of any one machine but could be linkedto many kinds of hardware thanks to its ability to directlymanipulate the contents of memory. C became tremendouslysuccessful in the 1980s. Since then, C and its offshoots C++and Java became the dominant languages used for most programmingtoday.Ritchie still works at Bell Labs’s Computing SciencesResearch Center. (When AT&T spun off many of its divisions,Bell Labs became part of Lucent Technologies.)Ritchie developed an experimental operating system calledPlan 9 (named for a cult sci-fi movie). Plan 9 attempts totake the UNIX philosophy of decentralization and flexibilityeven further, and is designed especially for networkswhere computing resources are distributed.Ritchie has received numerous awards, often givenjointly to Thompson. These include the ACM Turing Award(1985), the IEEE Hamming Medal (1990), the TsutomuKanai Award (1999), and the National Medal of Technology(also 1999).Further ReadingDennis Ritchie Home Page. Available online. URL: http://www.cs.bell-labs.com/who/dmr/. Accessed August 27, 2007.Kernighan, B. W., and Dennis M. Ritchie. The C ProgrammingLanguage. Upper Saddle River, N.J., Prentice Hall, 1978. (Asecond edition was published in 1989.)Lohr, Steve. Go To. New York: Basic Books, 2001.Plan 9 from Bell Labs. 4th ed. Available online. URL: http://plan9.bell-labs.com/plan9/. Accessed August 19, 2007.Ritchie, Dennis M., and Ken Thompson. “The UNIX Time-SharingSystem.” Communications of the ACM 17, 7 (1974): 365–375.Slater, Robert. Portraits in Silicon. Cambridge, Mass.: MIT Press,1987.roboticsThe idea of the automaton—the lifelike machine that performsintricate tasks by itself—is very old. Simple automatonswere known to the ancient world. By the 18th century,royal courts were being entertained by intricate humanlikeautomatons that could play music, draw pictures, or dance.A little later came the “Turk,” a chess-playing automatonthat could beat most human players.However, things are not always what they seem. Thetrue automatons, controlled by gears and cams, could playonly whatever actions had been designed into them. Theycould not be reprogrammed and did not respond to changesin their environment. The chess-playing automaton held aconcealed human player.True robotics began in the mid-20th century and hascontinued to move between two poles: the pedestrian butuseful industrial robots and the intriguing but tentativecreations of the artificial intelligence laboratories.Industrial RobotsIn 1921, the Czech playwright Karel Capek wrote a playcalled R.U.R. or Rossum’s Universal Robots. Robot is a Czechword that has been translated as work(er), serf, or slave. In theplay the robots, which are built by factories to work in otherfactories, eventually revolt against their human masters.During the 1960s, real robots began to appear in factorysettings (see also Engelberger, Joseph). They were an outgrowthof earlier machine tools that had been programmedby cams and other mechanisms. An industrial robot is basicallya movable arm that ends in a “hand” called an endeffector. The arm and hand can be moved by some combinationof hydraulic, pneumatic, electrical, or mechanicalmeans. Typical applications include assembling parts,welding, and painting. The robot is programmed for a taskeither by giving it a detailed set of commands to move to,grasp, and manipulate objects, or by “training” the robot bymoving its arm, hand, and effectors through the requiredmotions, which are then stored in the robot’s memory. Bythe early 1970s, Unimation, Inc. had created a profitablebusiness from selling its Unimate robots to factories.The early industrial robots had very little ability torespond to variations in the environment, such as the “work

obotics 411human workers, such as in the military, law enforcement,handling of hazardous materials, and so on.An experimental NASA robot arm. (NASA photo)piece” that the robot was supposed to grasp being slightlyout of position. However, later models have more sophisticatedsensors to enable them to adjust to variations andstill accomplish the task. The more sophisticated computerprograms that control newer robots have internal representationsor “frames of reference” to keep track of both therobot’s internal parameters (angles, pressures, and so on)and external locations in the work area.Mobile Robots and Service RobotsIndustrial robots work in an extremely restricted environment,so their world representation can be quite simple.However, robots that can move about in the environmenthave also been developed. Military programs have developedautomatic guided vehicles (AGVs) with wheels ortracks, capable of navigating a battlefield and scoutingor attacking the enemy (see military applications ofcomputers). Space-going robots including the SojournerMars rover also have considerable onboard “intelligence,”although their overall tasks are programmed by remotecommands.Indeed, the extent to which mobile robots are trulyautonomous varies considerably. At one end is the “robot”that is steered and otherwise controlled by its humanoperator, such as law enforcement robots that can be sentinto dangerous hostage situations. (Another example is therobots that fight in arena combat in the popular Robot Warsshows.)Moving toward greater autonomy, we have the “servicerobots” that have begun to show up in some institutionssuch as hospitals and laboratories. These mobile robotsare often used to deliver supplies. For example, the Help-Mate robot can travel around a hospital by itself, navigatingusing an internal map. It can even take an elevator to go toanother floor.Service robots have had only modest market penetration,however. They are relatively expensive and limited infunction, and if relatively low-wage more versatile humanlabor is available, it is generally preferred. For now mobilerobots and service robots are most likely to turn up inspecialized applications in environments too dangerous forSmart RobotsRobotics has always had great fascination for artificial intelligenceresearchers (see artificial intelligence). Afterall, the ability to function convincingly in a real-world environmentwould go a long way toward demonstrating theviability of true artificial intelligence.Building a smart, more humanlike robot involves severalinterrelated challenges, all quite difficult. These includedeveloping a system for seeing and interpreting the environment(see computer vision) as well a way to represent theenvironment internally so as to be able to navigate aroundobstacles and perform tasks.One of the earliest AI robots was “Shakey,” built at theStanford Research Institute (SRI) in 1969. Shakey couldnavigate only in a rather simplified environment. However,the “Stanford Cart,” built by Hans Moravec in the late 1970scould navigate around the nearby campus without gettinginto too much trouble.An innovative line of research began in the 1990s at MIT(see Brooks, Rodney and Breazeal, Cynthia). Instead ofa “top down” approach of programming robots with explicitlogical rules, so-called behavior-based robotics works fromthe bottom up, coupling systems of sensors and actuatorsthat each have their own simple rules, from which canemerge surprisingly complex behavior. The MIT “sociablerobots” Cog and Kismet were able to explore the world andlearn to interact with people in somewhat the way a humantoddler might.Today it is possible to buy an AI robot for one’s home, inthe form of toys such as Sony’s AIBO robot dog, which canemulate various doggy behaviors such as chasing things andcommunicating by body language. Some robot toys not onlyhave an extensive repertoire of behavior and vocalizations,but also can learn to some extent (see neural network.)It is also possible to experiment with robotics at homeor school, thanks to kits such as the LEGO Logo, whichcombines a popular building set with a versatile educationalprogramming language (see Logo).Future ApplicationsA true humanoid robot with the kind of capabilities writtenabout by Isaac Asimov and other science fiction writersis not in sight yet. However, there are many interestingapplications of robots that are being explored today. Theseinclude the use of remote robots for such tasks as performingsurgery (see telepresence) and the application ofrobotics principles to the design of better prosthetic armsand legs for humans (bionics). Farther afield is the possibilityof creating artificial robotic “life” that can self-reproduce(see artificial life).Further ReadingBreazeal, Cynthia. Designing Sociable Robots. Cambridge, Mass.:MIT Press, 2004.Brooks, Rodney A. Flesh and Machines: How Robots Will Change Us.New York: Pantheon Books, 2002.

412 RPGHenderson, Harry. Modern Robotics: Building Versatile Machines.New York: Chelsea House, 2006.Humanoid Robotics Group [MIT Artificial Intelligence Laboratory].Available online. URL: http://www.ai.mit.edu/projects/humanoid-robotics-group/. Accessed August 19, 2007.Menzel, Peter, and Faith D’Alusio. Robo Sapiens: Evolution of a NewSpecies. Cambridge, Mass.: MIT Press, 2001.Nof, Shimon Y. Handbook of Industrial Robotics. 2nd ed. New York:Wiley, 1999.Pires J. Norberto. Industrial Robots Programming: Building Applicationsfor the Factories of the Future. New York: Springer, 2007.Schraft, Rolf Dieter, and Gernot Schmierer. Service Robots: Products,Scenarios, Visions. Natick, Mass.: A. K. Peters, 2000.Severin, E. Oliver. Robotic Companions: Mentorbots and Beyond.New York: McGraw-Hill, 2004.Tesler, Pearl. Universal Robots: The History and Workings of Robotics.TheTech Museum. Available online. URL: http://www.thetech.org/exhibits/online/robotics/universal/index.html.Accessed August 19, 2007.RPG (Report Program Generator)Many business computer programs written for mainframecomputers involved reading data from files, performing relativelysimple procedures, and outputting printed reports.During the 1960s, some people believed that COBOL, ageneral-purpose (but business-oriented) computer language,would be easy enough for nonprogrammers to use(see COBOL). Although this turned out not to be the case,IBM did succeed in creating RPG (Report Program Generator),a language designed to make it easier for programmers(including beginners) to generate business reports.Most COBOL programs read data, perform tests and calculations,and print the results. RPG, first released in 1964for use with the new System/360 mainframe and the smallerSystem/3, simplifies this process and eliminates most writingof program code statements.A “classic” RPG program is built around the “RPGcycle,” consisting of three stages. During the input stage,the input device(s), file type, access specifications, and datarecord structure are specified. (These specifications can bequite elaborate.) The heart of the program specifies calculationsto be performed with the various data fields, while theoutput section specifies how the results will be laid out inreport form, including such things as headers, footers, andsections.Subsequent versions of RPG added more features. RPG-IV, released in 1994, includes the ability to define subroutines,for example. IBM has also released VisualAge RPG,which allows for the creation and running of RPG programsin the Microsoft Windows environment. There arealso tools for interfacing RPG programs with various databasesystems and to use RPG for writing Web-based (CGI)programs.Further ReadingCozzi, Robert. The Modern RPG IV Language. 4th ed. Lewisville,Tex.: MC Press Online, 2006.Martin, Jim. Free-Format RPG IV: How to Bring Your RPG Programsinto the 21st Century. Lewisville, Tex.: MC Press Online, 2005.Meyers, Bryan, and Jef Sutherland. VisualAge for RPG by Example.Loveland, Colo.: Duke Press, 1998.RSS (Really Simple Syndication)Web sites such as news providers and blogs (see blogsand blogging) are constantly posting new material. Whilereaders can periodically visit a site to look for new material,an increasingly popular option is to subscribe to a “Webfeed” and receive the latest information automatically. Themost commonly used tool for Web feeds is RSS, which canstand for Really Simple Syndication, Rich Site Summary, orRDF Site Summary, depending on the format used.The data in an RSS feed can include article titles, summaries,excerpts (such as the first paragraph), or the completearticle or posting. Feeds can also include multimediasuch as graphics, video, or sound. The data (and any linkedmaterial) is formatted using standard markup elements (seeHTML and XML). The following is an excerpt of a simpleRSS feed provided by the RSS Advisory Board:Liftoff Newshttp://liftoff.msfc.nasa.gov/Liftoff to Space Exploration.en-usTue, 10 Jun 2003 04:00:00 GMTTue, 10 Jun 2003 09:41:01GMThttp://blogs.law.harvard.edu/tech/rssWeblog Editor 2.0editor@example.comwebmaster@example.comStar Cityhttp://liftoff.msfc.nasa.gov/news/2003/news-starcity.aspHow do Americans getready to work with Russians aboardthe International Space Station? Theytake a crash course in culture, languageand protocol at Russia’s <ahref=“http://howe.iki.rssi.ru/GCTC/gctc_e.htm”>Star City</a>.Tue, 03 Jun 2003 09:39:21GMThttp://liftoff.msfc.nasa.gov/2003/06/03.html#item573As part of the process of setting up a feed on the Webserver, the feed is “published” so that it can be found andread using a client program called a reader or aggrega-

Ruby 413tor (the latter can combine feeds or organize them in anewspaper-like format for convenience). RSS readers canbe stand-alone applications or be included with many modernWeb browsers and e-mail clients. Alternatively, Webbasedreaders or aggregators such as NewsGator Online canallow feeds to be read using any Web browser. Readers ofWeb pages can find RSS feeds by looking for a “subscribe”icon or the words RSS or XML. Specialized search enginessuch as Bloglines can also help users find interesting feeds.Additionally, information on the server can also be usedby software to automatically deliver the latest content (seepodcasting).History and DevelopmentForerunners of RSS go back to the mid-1990s, with RDFSite Summary first appearing in 1999 for use on Netscape’sportal. The adoption of RSS by the New York Times in 2002greatly aided the popularization of the format, as did thegrowing number of blogs that needed a way for contributorsand readers to keep in touch. Today Web browsers such asInternet Explorer, Mozilla Firefox, and Safari support RSS.File-sharing services such as BitTorrent can be combinedwith RSS to deliver content automatically to users’ harddrives. An offshoot of RSS called Atom has been less widelyadopted, but offers better compatibility with XML standardsand better management of multimedia content.Further ReadingBloglines. Available online. URL: http://www.bloglines.com/.Accessed November 19, 2007.Calishain, Tara. Information Trapping: Real-Time Research on theWeb. Berkeley, Calif.: New Riders, 2007.Finkelstein, Ellen. Syndicating Web Sites with RSS Feeds for Dummies.Hoboken, N.J.: Wiley, 2005.RSS Advisory Board. Available online. URL: http://www.rssboard.org. Accessed November 19, 2007.Sherman, Chris. “What Is RSS, and Why Should You Care?” SearchEngine Watch, August 30, 2005. Available online. URL: http://searchenginewatch.com/showPage.html?page=3530926.Accessed November 19, 2007.RTF (Rich Text Format)Rich Text Format was developed in the later 1980s by programmersat Microsoft. Its purpose is to allow for interchangeof documents between Microsoft Word and othersoftware, while preserving the original formatting.An RTF file is itself a plain text file containing the documenttext enclosed in control codes that determine the formatting.For example:{\rtf1\ansi{\fonttbl{\f0\froman\fprq2\fcharset0 Times New Roman;}\f0\pardThis is some {\b bold} text.\par}The backslash starts a control code, such as for specifyinga font or a style, such as Times New Roman and boldin the example. Curly brackets { } enclose the text to beaffected by the control code. Thus the example above wouldbe rendered in a word processor as:This is some bold text.Although RTF is an 8-bit format, special escapesequences can be used to specify 16-bit Unicode characters,such as for non-Roman alphabets.Libraries and utilities are available for reading andwriting RTF from most popular programming languages,including Perl, PHP, and Ruby.In practice, RTF created by word processors tends tocontain many control codes needed to ensure compatibilitywith older programs, making the files bulky and not practicableto edit directly. However, saving a file in RTF is agood way to ensure that a document can be used by recipientswho may have, for example, older versions of Word. (Itis quite typical for the latest default Word format to not becompatible with earlier versions.)Further ReadingBurke, Sean M. RTF Pocket Guide. Sebastapol, Calif.: O’Reilly,2003.Microsoft Corporation. Word 2007: Rich Text Format (RTF),Specification, Version 1.9. Available online. URL: http://www.microsoft.com/downloads/details.aspx?FamilyID=DD422B8D-FF06-420 7-B476-6B5396A18A2B. Accessed November 13,2007.RubyRuby is a versatile yet consistent programming languagethat has become popular in recent years, particularly forWeb development. Designed by Yukihiro Matsumoto andfirst released in 1995, Ruby has a compact syntax familiarto many users of Perl and other scripting languages (seePerl and Scripting language), avoiding, for example,the need to declare variable types. However, Ruby is alsoa thoroughgoing object-oriented language somewhat likeSmalltalk (see Smalltalk). Matsumoto has stressed thatthe design of the language is intended to stress being naturaland enjoyable for the programmer, rather than focusingon the needs of the machine.StructureIn Ruby, every data type is an object (see class, data type,and object), even those defined as primitive types in otherlanguages, such as integers and Booleans. Although one canuse the traditional procedural method of defining variablesand then working with them, they are still implicitly treatedas part of the root object called “Self.”Every function is a method that belongs to some class.Thus -5.abs invokes the absolute value method on the integer-5, returning 5. Similarly, “wireless wombat”.lengthwould return the length of the string, 15. Ruby includesmany built-in methods for working with data structuressuch as arrays and hashes, and there are many additionallibraries and applications available.There are Ruby interpreters for all major operating systems.In addition to reading and executing a program from

414 Rubya file, as with many scripting languages, Ruby can also beused interactively to test statements:% ruby eval.rbruby> puts “Hello, world.”Hello, world.nilruby> exitHere the Ruby interpreter is told to run eval.rb, a specialprogram that interactively evaluates statements and expressions.The puts command puts (outputs) the string Hello,world. The evaluator then reports that the puts methodreturned no value (nil).Although Ruby is traditionally an interpreted language,a version that will produce byte code for a virtual machine(similar to Java) is in development, and a more direct compileris certainly possible.Ruby on RailsThe most popular programming environment for Rubyis Ruby on Rails, an open-source application frameworkaimed particularly at writing programs that connect Websites to databases. The framework is based on the modelviewcontroller approach (separating data access and logicfrom the user interface) and includes “scaffolding” that canbe quickly filled in to provide data-driven Web sites withbasic functionality. Developers can also create plug-ins toextend the built-in packages.Further ReadingBaird, Kevin. Ruby by Example: Concepts and Code. San Francisco:No Starch Press, 2007.Burd, Barry. Ruby on Rails for Dummies. Hoboken, N.J.: Wiley,2007.Cooper, Peter. Beginning Ruby: From Novice to Professional. Berkeley,Calif.: Apress, 2007.“Ruby: A Programmer’s Best Friend.” Available online. URL: http://www.ruby-lang.org/en/. Accessed November 13, 2007.Slagell, Mark. “Ruby User’s Guide.” Available online. URL: http://www.mentalpointer.com/ruby/index.html. Accessed November13, 2007.Stewart, Bruce. “An Interview with the Creator of Ruby.” O’ReillyLinux devcenter, November 29, 2001. Available online. URL:http://www.linuxdevcenter.com/pub/a/linux/2001/11/29/ruby.html. Accessed November 13, 2007.Thomas, Dave. Programming Ruby: The Pragmatic Programmer’sGuide. 2nd ed. Raleigh, N.C.: Pragmatic Bookshelf, 2004.

SSAPSAP (NYSE symbol: SAP) is a German acronym for Systeme,Anwendungen, und Produkete in der Datenverarbeitung (“Systems,Applications, and Products in Data Processing”). Fiveformer IBM engineers in Germany founded the company in1972.Although unfamiliar to the American public, unlike IBMand Microsoft, SAP is the world’s largest business softwarecompany, and fourth-largest software provider in general(behind Microsoft, IBM, and Oracle). The company operatesworldwide through three geographical divisions.Applications and ProductsSAP specializes in Enterprise Resource Planning (ERP),enhancing a corporation’s ability to manage its key assetsand needs and to plan for the future. This software consistsof three tiers: the database, an application server, and theclient. Early versions of this software were designed to runon mainframes. Other major products include:• SAP NetWeaver, which integrates all other SAP modulesusing modern open-standard Web technologies(see service-oriented architecture)• Customer Relationship Manager (see crm)• Supply Chain Management (see supply chain management)• Supplier Relationship Management• Human Resource Management System• Product Lifestyle Management• Exchange Infrastructure• Enterprise Portal• SAP Knowledge WarehouseChallengesSAP has recognized for some time that while its base oflarge Fortune 500 companies has given it steady income,changing trends in business have been limiting the softwaregiant’s growth. In particular, the trend has beentoward smaller, simpler, more scalable applications thatcan be integrated with modern Web services. In September2007 SAP announced SAP Business ByDesign, a flexible setof enterprise management services that are delivered overthe Web. However, it remains to be seen how well SAP willbe able to compete with more agile companies such as Net-Suite and Salesforce.com, and whether the company will beable to upgrade its existing large company user base withoutdisaffecting it.SAP’s major competitor in the United States is Oracle(see Oracle), which has sued SAP in 2007 for unfairlydownloading and using patches and support materials fromOracle and using them to support former Oracle customers.SAP and Oracle have generally had quite different growthstrategies: SAP grows by expanding and extending its ownproducts, while Oracle has grown mainly through acquiringother companies. However, in October 2007 SAP acquiredBusiness Objects, a leader in “business intelligence” systems,for $6.8 billion. This may signal SAP’s willingness toengage in further strategic acquisitions.415

416 satellite Internet serviceFurther ReadingMcDonald, Kevin, et al. Mastering the SAP Business InformationWarehouse: Leveraging the Business Intelligence Capabilities ofSAP NetWeaver. 2nd ed. Indianapolis: Wiley, 2006.Ricadela, Aaron. “SAP’s Down-Market Gamble.” Business Week,September 19, 2007. Available online. URL: http://www.businessweek.com/technology/content/sep2007/tc20070919_181869.htm. Accessed October 5, 2007.SAP.com. Available online. URL: http://www.sap.com/usa/index.epx. Accessed October 8, 2007.“SAP History: From Start-Up Software Vendor to Global MarketLeader.” Available online. URL: http://www.sap.com/company/history.epx. Accessed October 8, 2007.Vogel, Andreas, and Jan Kimbell. mySAP for Dummies. Hoboken,N.J.: Wiley, 2004.Woods, Dan, and Jeffrey Word. SAP NetWeaver for Dummies. Hoboken,N.J.: Wiley, 2004.satellite Internet serviceAs with television, satellite Internet service can provideaccess to areas (such as remote locations, ships, or landvehicles) where wired service is not available (see broadband).Besides the satellite, the system includes a terrestrialfacility that has two connections: routers and proxy serversthat manage the flow of traffic to and from the Internet, andan “uplink” transmitter that communicates with the satellite.In addition, there may be a connection to the publictelephone network.Each user has a satellite dish and associated equipmentsimilar to those used for receiving satellite TV, though thedish is larger and existing TV dishes cannot be used. In theNorthern Hemisphere, the user must have an unobstructedview of the southern sky (most satellites orbit over theequator). The equipment is also adapted for use on shipsand recreational vehicles.The user also has a modem (either external or on a cardin the PC) to convert the satellite signals to data, and softwaresupplied by the satellite service.There are two types of systems for sending data from theuser back to the Internet. In a dial-return system, the userhas a conventional telephone dial-up modem that connectsby phone to a hub at the terrestrial facility. Downloadingis at broadband speeds (comparable to low-end DSL orcable), but uploading is at dial-up speeds. (This is not usuallya problem unless the user is uploading large files.) In atwo-way system, the user has a transmitter that sends datadirectly back to the satellite. This is usually several timesfaster than dial-up, but is more expensive.Because of the time it takes signals to travel between asatellite and the ground, all satellite Internet systems have abuilt-in delay, or latency. Satellites in geosynchronous orbit(about 22,000 miles [35,405.6 km] high) have wider coveragebut higher latency, while using lower orbits reduceslatency but requires more satellites to provide continuouscoverage. Latency can be problematic for applications suchas Internet telephony (see VOIP).Although small compared with that for cable or DSL,the satellite user base is growing, particularly in areas andcountries that lack wired infrastructure. Users who havecable or DSL available in their neighborhood would havelittle reason to obtain satellite Internet, since the initial andmonthly costs are considerably higher and download speedsare somewhat slower. Also, the need to use encrypted virtualprivate networks (VPN) to secure business data canlower effective speeds substantially. Finally, though the satellitesthemselves are very reliable, satellite service is subjectto interruption during heavy rain or snow.Further ReadingBrodkin, Jon. “Satellite Services and Telecommuting Not Alwaysa Pretty Mix.” NetworkWorld, July 24, 2007. Availableonline. URL: http://www.networkworld.com/news/2007/072407-satellites-for-telecommuting.html. Accessed November14, 2007.“How Does Satellite Internet Operate?” HowStuffWorks. Availableonline. URL: http://computer.howstuffworks.com/question606.htm. Accessed November 14, 2007.Kota, Sastri L., Kaveh Pahlavan, and Pentti Leppanen. BroadbandSatellite Communication for Internet Access. Norwell, Mass.:Kluwer Academic Publishers, 2004.Nutter, Ron. “Getting More Performance from a Satellite InternetSystem.” Network World, April 16, 2007. Available online. URL:http://www.networkworld.com/columnists/2007/041607nutter.html. Accessed November 14, 2007.scannerIn order for a computer to work with information, theinformation must be digitized—converted to data thatapplication programs can recognize and manipulate (seecharacters and strings). Computer users have thusbeen confronted with the task of converting millions ofpages of printed words or graphics into machine-readableform. Since it is expensive to re-key text (and impractical toredraw images), some way is needed to automatically convertthe varying shades or colors of the text or images into adigitized graphics image that can be stored in a file.This is what a scanner does. The scanner head containsa charge-coupled device (CCD) like that used in digital cameras(see photography, digital). The CCD contains thousandsor millions of tiny regions that can convert incominglight into a voltage level. Each of these voltage levels, whenamplified, will correspond to one pixel of the scanned image.(A color scanner uses three different diodes for each pixel,each receiving light through a red, green, or blue filter.)The operation of the head depends on the type of scanner.In the most common type, the flatbed scanner, a motormoves the head back and forth across the paper, which liesfacedown on a glass window. In a sheet-fed scanner, thehead remains stationery and the paper is fed past it by a setof rollers. Finally, there are handheld scanners, where thejob of moving the scanner head is performed by the usermoving the scanner back and forth over the page.The resolution of a scanner depends on the number ofpixels into which it can break the image. The color depthdepends on how many bits of information that it can storeper pixel (more information means more gradations of coloror gray). Resolutions of 2,400 dots per inch (dpi) or moreare now common, with up to 36 bit color depth, allowingfor about 68.7 billion colors or gradations (see color incomputing).

scheduling and prioritization 417Besides considerations of resolution and color depth, thequality of a scanned image depends on the quality of thescanner’s optics as well as on how the page or other objectreflects light. As anyone who has browsed eBay listingsknows, the quality of scans can vary considerably. Mostscanners come with software that allows for the scanner tobe controlled and adjusted from the PC, and image-editingsoftware can be used to further adjust the scanned image.Even if the input is a sheet of text, the scanner’s outputis simply a graphical image. Special software must be usedto interpret scanned images of text and identify which charactersand other features are present (see optical characterrecognition). Since such software is not 100 percentaccurate, human proofreaders may have to inspect theresulting documents.Like printers, scanners have become quite inexpensivein recent years. Quite serviceable units are available foraround $100 or so. (Popular multifunction devices ofteninclude scanner, copier, fax, and printer capabilities. Ascanner can be used as a copier or fax by sending its outputto the appropriate mechanism.)Many home users now use scanners to digitize imagesfor use in personal Web pages, online auctions, and othervenues. Since sheet-fed scanners can only process individualsheets (not books, magazines, or objects) they are now lesspopular. Handheld scanners are somewhat tedious to useand require a steady hand, so they are generally used only inspecial circumstances where a flatbed scanner is not available.For capturing images of three-dimensional objects it isoften easier to use a digital camera than a scanner.Specialized scanners are also available. For example,although many flatbed scanners have a holder for scanningfilm negatives, a dedicated film scanner (costing perhaps$500) is a better choice if one wants to scan and possiblyretouch or restore photographs. There are also high-enddrum-type scanners that can scan at resolutions of 10,000dpi or more.Further ReadingBusch, David D. Mastering Digital Scanning with Slides, Film, andTransparencies. Boston: Muska & Lipman, 2004.Chambers, Mark L. Scanners for Dummies. Hoboken, N.J.: Wiley,2004.PC Tech. Guide: Scanners. Available online. URL: http://www.pctechguide.com/55Scanners.htm. Accessed August 20, 2007.scheduling and prioritizationOften in computing, a fixed resource must be parceled outamong a number of competing users. The most obviousexample is the operating system’s scheduling the runningof programs. Most computers have a single central processor(CPU) to execute programs. However, today virtuallyall operating systems (except for certain dedicated applications—seeembedded system) are expected to have manyprograms available simultaneously. For example, a MicrosoftWindows user might have a word processor, spreadsheet,e-mail program, and Web browser all open at thesame time. Not only might all of these programs be carryingout tasks or waiting for the user’s input, but dozens of“hidden” system programs are also running in the background,providing services such as network support, virusprotection, and printing services (see multitasking).In this environment each executing program (or “process”)will be in one of three possible states. It may beactively executing (that is, its code is being run by theCPU). It may be ready to execute—that is, “wanting” toperform some activity but needing access to the CPU. Or,the program may be “blocked”—that is, not executing andunable to execute until some external condition is met.Blockage is usually caused by an input/output (I/O) operation.An example would be a program that’s waiting for datato finish loading from a file.In this sort of single-processor multiple-program system,the simplest arrangement is to have the operatingsystem dole out fixed amounts of execution time to eachprogram. Each program that indicates that it’s ready to rungets placed in a list (see queue) and given its turn. Whenthe amount of time fixed for a turn has passed, the operatingsystem saves the program’s “state” in the processor—thecontents of the registers, address pointed to by the pointerto the next instruction to be executed, and so on. Thisstored information can be considered to be a “virtual processor.”When the program’s turn comes around again, theprocessor is reloaded with the contents of the virtual processorand execution continues where it had left off.Use of PriorityThe above scheme assumes that all programs should haveequal priority. In other words, that the timely completionof one program is not more important than that of another,or that no program should be “bumped up” in the queue forsome reason. In reality, however, most operating systems dogive some programs preference over others.For example, suppose the word processor has justreceived a user’s mouse click on a menu. The next programin the queue for execution, however, is an antivirus programthat’s checking all the files on the hard drive for possibleviruses. The latter program is important, but since theuser is not waiting for it to finish, a delay in its executionwon’t cause a significant problem. The user, on the otherhand, is expecting the menu just clicked on to open almostinstantly, and will become irritated with even a short delay.Therefore, it makes sense for the operating system to givea program that’s responding to immediate user activity ahigher priority than a program that’s carrying out tasksthat don’t require user intervention.There are other times when a program must (or should)be given a higher priority. A program may be required tocomplete a task within a guaranteed time frame (for example,to dispatch emergency services personnel). The operatingsystem must therefore provide a way that the programcan request priority execution.In general, an operating system that supports real-timeapplications or that requires great attention to efficiency inusing valuable devices may need a much more sophisticatedscheduling algorithm that factors in the availability of keydevices or services and adjusts program priorities in orderto minimize bottlenecks and guarantee that the system’s

418 science fiction and computingresponse will be within required parameters. Indeed, themethod used for assigning priorities may actually be changedin response to changes in the various “loads” on the system.Sophisticated systems may also include programs that canpredict the likely future load on the system in order to adjustfor it as quickly as possible.Scheduling Multiprocessor SystemsThese general principles also apply to systems where morethan one processor is available (see multiprocessing),but there is the added complication of deciding where thescheduling program will be run. In a multiprocessing systemthat has one “master” and many “slave” processors,the scheduling program runs on the master processor. Thisarrangement is simple, but it means that when a slave processorwants to schedule a program it must wait until thescheduling program gets its next time-slice on the masterprocessor.One alternative is to allow any processor that has freetime to run the scheduling algorithm. This is harder toset up because it requires a mechanism to make sure twoprocessors do not try to run the scheduling program at thesame time, but it smoothes out the bottleneck that wouldarise from relying on a single processor.A variant of this approach is “distributed scheduling.”Here each processor runs its own scheduling program.All the schedulers share the same set of information aboutthe status and queuing of processes on the system, anda locking mechanism is used to prevent two processorsfrom changing the same information at the same time. Thisapproach is easiest to “scale up” since added processors cancome with their own scheduling programs.Two trends in recent years have changed the emphasisin scheduling algorithms. One is the continuing dropin price per unit of processing power and memory. Thismeans that maximum efficiency in using the hardwarecan often give way in favor of catering to the user’s convenienceand perceptions by giving more priority to interactionwith the user. The other development is the growinguse of systems where much of the burden of graphics andinteractivity is placed on the user’s desktop, thus simplifyingthe complexity of scheduling for the server (see client-servercomputing).Principles of scheduling and priority can be appliedin areas other than computer operating systems. Schedulinghuman activities (such as factory work) adds furthercomplications such as the dependence of one task uponthe prior performance of one or more other tasks (seeproject management software) and the “just-in-time”scheduling for minimizing the investment in materials orinventory.Further ReadingBrucker, Peter. Scheduling Algorithms. 5th ed. New York: Springer-Verlag, 2007.Leung, Joseph Y-T., ed. Handbook of Scheduling Algorithms, Models,and Performance Analysis. Boca Raton, Fla.: CRC Press,2004.Pinedo, M. Scheduling: Theory, Algorithms, and Systems. 2nd ed.Upper Saddle River, N.J.: Prentice Hall, 2001.science fiction and computingThe image of the mechanical brain or “knowledge engine”has a surprisingly long history in Western literature. As farback as Jonathan Swift’s Gulliver’s Travels (1726), we finda gigantic engine that can create books on every conceivablesubject. While this was a satirical jab at thinkers whowere ushering in a rational, mechanistic cosmos, the ideathat the cunning mechanical automatons being created forthe amusement of princes might someday think did notseem so far-fetched. This belief would be strengthened inthe coming two centuries by the triumph of the IndustrialRevolution. In Jules Verne’s Paris in the Twentieth Century(written in 1863), giant calculating machines and facsimiletransmissions were used to coordinate business activities.As early as the beginning of the 20th century, writershad been exploring what might happen if some combinationof artificial brains and robots offered the possibility of cateringto all human needs. In E. M. Forster’s “The MachineStops,” published in 1909, people no longer even have toleave their insectlike cells because even their social needsare provided through machine-mediated communicationnot unlike today’s Internet. In the 1930s and 1940s, otherwriters such as John W. Campbell and Jack Williamsonwrote stories in which a worldwide artificial intelligencebecame the end point of evolution, with humans eitherbecoming extinct or living static, pointless lives.Science fiction writers had also been considering theramifications of a related technology, robotics. The termrobot came from Karel Čapek’s R.U.R. (Rossum’s UniversalRobots). Although the robot had a human face, it couldhave inhuman motives and threaten to become Earth’s newmaster, displacing humans. Isaac Asimov offered a morebenign vision, thanks to the “laws of robotics” embeddedin his machines’ very circuitry. The first law states, “A robotshall not harm a human being or, through inaction, cause ahuman being to come to harm.” In the real world, of course,artificial intelligence had no such built-in restrictions (seeartificial intelligence).Science fiction of the “Golden Age” of the pulp magazineshad only limited impact on popular culture as a whole. Onceactual computers arrived on the scene, however, they becamethe subject for movies as well as novels. D. F. Jones’s novelColossus: The Forbin Project (1966), which became a film in1970, combined cold war anxiety with fear of artificial intelligence.Joining forces with its Soviet counterpart, Colossusfulfills its orders to prevent war by taking over and institutinga world government. Similarly, Hal in the film 2001:A Space Odyssey (based on the work of Arthur C. Clarke)puts its own instinct for self-preservation ahead of the franticcommands of the spaceship’s crew. However, the artificialcan also strive to be human, as in the 2001 movie A.I.During the 1940s and 1950s science fictional computerstended to be larger, more powerful versions of existingmainframes, sometimes aspiring to godlike status. However,in Murray Leinster’s book A Logic Named Joe (1946),a “Logic” is found in every home, complete with keyboardand television screen. All the Logics are connected to ahuge relay circuit called the Tank, and the user can obtaineverything from TV broadcasts to weather forecasts or even

scientific computing applications 419fiction called cyberpunk, where outlaws and murderous corporationsduel on the virtual frontier. Beyond the high-techchases, questions of the ultimate meaning of cyberspace andof reality itself emerge, as in the Matrix trilogy of movies, orin the ultimate transformation of consciousness in humanand machine (see singularity, technological).Perhaps the most famous science fiction movie of all is 2001: ASpace Odyssey (1968). However, the millennial year passed withouteither an AI like Hal or passenger space lines. (©ArenaPal /Topham / The Image Works)the answers to history trivia questions. Although the Logicis essentially an electronic-mechanical system, its functionalityis startlingly similar to that achieved by the Internetalmost half a century later.Writers such as William Gibson (Neuromancer) and VernorVinge (True Names) later began to explore the worldmutually experienced by computer users as a setting wherehumans could directly link their minds to computer-generatedworlds (see virtual reality). A new elite of cyberspacemasters were portrayed in a futuristic adaptationof such archetypes as the cowboy gunslinger, samurai, orninja. Unlike the morally unambiguous world of the oldwestern movies, however, the novels and movies with thenew “cyberpunk” sensibility are generally set in a jumbled,fragmented, chaotic world. That world is often dominatedby giant corporations (reflecting concerns about economicglobalism) and is generally dystopian.Meanwhile as cyberspace continues to become reality,cyberpunk has lost its distinctiveness as a genre. Gibson’slatest work (and that of other writers such as Bruce Sterlingand Vernor Vinge) is more apt to explore ways of communicatingand networking that belong to just the day aftertomorrow, if not already appearing (particularly amongyoung people) today.Cyberpunk and BeyondAs personal computers and networking began to burgeonin the 1980s, the focus began to shift from computers as“characters” to the ways in which people interact with, andare changed by, new technology.Although the term cyberspace was introduced by writerWilliam Gibson in his 1982 short story “Burning Chrome,”the word did not come into greater prominence until his1984 novel Neuromancer, where it was described as “a consensualhallucination experienced daily by billions. . . .” (Seecyberspace.) It became the arena for a new style of scienceFurther ReadingAsimov, Isaac, Patricia S. Warrick, and Martin H. Greenberg, eds.Machines That Think: The Best Science Fiction Stories aboutRobots and Computers. New York: Holt, Rinehart, and Winston,1984.Computer in Science Fiction. Available online. URL: http://www.technovelgy.com/ct/Science_List_Detail.asp?BT=Computer.Accessed November 14, 2007.Conklin, Groff, ed. Science-Fiction Thinking Machines: Robots,Androids, Computers. New York: Vanguard Press, 1954.Franklin, H. Bruce. “Computers in Fiction,” 2000. Availableonline. URL: http://andromeda.rutgers.edu/~hbf/compulit.htm. Accessed November 14, 2007.Frenkel, James, ed. True Names by Vernor Vinge and the Opening ofthe Cyberspace Frontier. New York: Tor, 2001.Gibson, William. Neuromancer. New York: Ace Books, 1984.———. Pattern Recognition. New York: G. P. Putnam’s Sons, 2003.Vinge, Vernor. Rainbow’s End. New York: Tor, 2006.Warrick, Patricia S. The Cybernetic Imagination in Science Fiction.Cambridge, Mass.: MIT Press, 1980.scientific computing applicationsFrom microbiology to plasma physics, modern sciencewould be impossible without the computer. This is notbecause the computer has replaced the scientific methodof observation, hypothesis, and experiment. Modern scientistsessentially follow the same intellectual procedures atdid Galileo, Newton, Darwin, and Einstein. Rather, understandingof the layered systems that make up the universehas now reached so complex and detailed a level that thereis too much data for an individual human mind to grasp.Further, the calculations necessary to process the data usuallycan’t be performed by unaided humans in any reasonablelength of time. This can be caused either by theinherent complexity of the calculation (see computabilityand complexity) or the sheer amount of data (as in DNAsequencing; see bioinformatics and data mining).InstrumentationSome apparatus such as particle accelerators are complicatedenough to make it expedient to control the operation bycomputer. It is simply more convenient to have instrumentssuch as spectrocopes process samples automatically undercomputer control and produce printed results.Most instruments for gathering data use electronicsto turn physical measurements into numeric representations(see analog and digital and data acquisition).The modern instrument’s built-in processor and softwareperforms preliminary processing that used to have to bedone later in the lab. This can include scaling the data toan appropriate range of values, eliminating “noise” data,and providing an appropriate time framework for interpretingthe data. Use of electronics also enables the data to be

420 scientific computing applicationstransmitted from a remote location (telemetry). See spaceexploration and computers.Data AnalysisThe analysis of data to obtain theoretical understanding ofthe processes of nature also greatly benefits from the powerof computers ranging from ordinary PCs to high-performancescientific workstations to large supercomputers. Thepossible significance of variables can be determined by statisticaltechniques (see also statistics and computing).The fundamental task in understanding any systemis to isolate the significant variables and determine howthey affect one another. In many cases this can be done bysolving differential equations, where a dependent variablechanges as a result of changes in one or more independentvariables. For example, the classical Maxwell theoryof wave behavior is a system of differential equations thatcould be used to understand, for example, how radar waveswill bounce off an object with a given shape and reflectivity.However, real-world objects have complicating factors:A given problem may include aspects of wave behavior,electromagnetic interaction, deformation of material, andso on. While the great scientists of the late 19th to mid-20thcentury could develop elegant formulas showing key relationshipsin nature, the interaction of many different phenomenaoften requires much more formidable computationthat must be applied to many individual components.It might be considered fortunate that the computer camealong at about the time that it was required for furtherscientific progress. However, another way to look at it isto note that much of the pressure that led to investment inthe development of computers came from that very needfor computational resources, albeit primarily for wartimeprojects.Simulation and VisualizationEven if scientists have a basic understanding of a system,it may be hard to determine what the overall results of theinteraction of the many particles (or other elements) in thesystem will be. This is true, for example, in the analysis ofevents taking place in nuclear reactors. Fortunately computerscan apply the laws of the system to each of manyparticles and determine the resulting actions from theiraggregate behavior (see simulation). Simulation is particularlyimportant in fields where actual experiments are notpossible because of distance or time. Thus, a hypothesisabout the formation of the universe can be tested by applyingit to a set of initial conditions believed to reflect those ator near the time of the big bang.However, even the most skilled scientists have troublerelating numbers to the shape and interaction of real-worldobjects. Computers have greatly aided in making it possibleto visualize structures and phenomena using high-resolution3D color graphics (see computer graphics). FeaturesComputer processing of photographic or scanned data can provide detailed information about our environment. In this NASA test project,aerial and satellite imagery is analyzed to yield information about the ripeness of grapes in a vineyard, as well as moisture, soil conditions,and plant disease. (NASA photo)

scripting languages 421of interest can be enhanced, and arbitrary (“false”) colorscan be used to visually show such things as temperatureor blood flow. These techniques can also be used to createinteractive models where scientists can, for example,combine molecules in new ways and have the computercalculate the likely properties of the result. Finally, computervisualization and modeling can be used both to teachscience and to give the general public some visceral grasp ofthe meaning of scientific theories and discoveries.Further ReadingHeath, Michael T. Scientific Computing: An Introductory Survey.2nd ed. New York: McGraw-Hill, 2002.Jahne, Bernd. Practical Handbook of Image Processing for ScientificApplications. 2nd ed. Boca Raton, Fla.: CRC Press, 2004.Langtangen, H. P., A. M. Bruaset, and E. Quak, eds. Advances inSoftware Tools for Scientific Computing. New York: Springer,2000.Linux Software: Scientific Applications. Available online. URL:http://linux.about.com/od/softscience/Linux_Software_Scientific_Applications.htm. Accessed August 20, 2007.Oliveira, Suely, and David E. Stewart. Writing Scientific Software: AGuide to Good Style. New York: Cambridge University Press,2006.Scientific Computing and Numerical Analysis FAQ. Available online.URL: http://www.mathcom.com/corpdir/techinfo.mdir/index.html. Accessed August 20, 2007.scripting languagesThere are several different levels at which someone cangive commands to a computer. At one end, an applicationsprogrammer writes program code that ultimately results ininstructions to the machine to carry out specified processing(see programming languages and compiler). Theresult is an application that users can control in order to gettheir work done.At the other end, the ordinary user of the applicationuses menus, icons, keystrokes, or other means to selectprogram features in order to format a document, calculatea spreadsheet, create a drawing, or perform some othertask. Today most users also control the operating system byusing a graphical user interface to, for example, copy files.However, there is an intermediate realm where text commandscan be used to work with features of the operatingsystem, to process data through various utility programs,and to create simple reports. For example, a system administratormay want to log the number of users on the systemat various times, the amount of disk capacity being used,the number of hits on various pages on a Web server, andso on. (See system administrator.) It would be expensiveand time-consuming to write and compile full-fledgedapplication programs for such tasks, particularly if changingneeds will dictate frequent changes in the processing.The use of the operating system shell and shell scripting(see shell) has traditionally been the way to deal withautomating routine tasks, especially with systems runningUNIX. However, the complexity of modern networks andin particular, the Internet, has driven administrators andprogrammers to seek languages that would combine thequick, interactive nature of shells, the structural features offull-fledged programming languages, and the convenienceof built-in facilities for pattern-matching, text processing,data extraction, and other tasks. The result has been thedevelopment of a number of popular scripting languages(see awk, Perl, and Python).Working with Scripting LanguagesAlthough the various scripting languages differ in syntaxand features, they are all intended to be used in a similarway. Unlike languages such as C++, scripting languages areinterpreted, not compiled (see interpreter). Typically, ascript consists of a number of lines of text in a file. Whenthe file is invoked (such as by someone typing the nameof the language followed by the name of the script file atthe command prompt), the script language processor parseseach statement (see parser). If the statement includes a referenceto one of the language’s internal features (such as anarithmetic operator or a print command), the appropriatefunction is carried out. Most languages include the basictypes of control structures (see branching statementsand loop) to test various variables and direct executionaccordingly.The trend in higher-level languages has been to requirethat all variables be declared to be used for particular kindsof data such as integer, floating-point number, or characterstring (see data types). Scripting languages, however,are designed to be easy to use and scripts are relativelysimple and easy to debug. Since the consequences of errorsinvolving data types are less likely to be severe, scriptinglanguages don’t require that variables be declared beforethey are used. The language processor will make “commonsense” assumptions about data. Thus if an integer such as23 and a floating-point number like 17.5 must be addedtogether, the integer will be converted to floating point andthe result will be expressed as the floating-point value 40.5.Similarly, scripting languages take a relaxed view aboutscope, or the parts of a program from which a variable’svalue can be accessed. Scripting languages do provide forsome form of subroutine or procedure to be declared (seeprocedures and functions). Generally, variables usedwithin a subroutine will be considered to be “local” to thatsubroutine, and variables declared outside of any subroutinewill be treated as global.With compilers for regular programming languages, agreat deal of attention must be paid to creating fast, efficientcode. A scientific program may need to optimize calculationsso that it can tackle cutting-edge problems in physicsor engineering. A commercial application such as a wordprocessor must implement many features to be competitive,and yet be able to respond immediately to the user andcomplete tasks quickly.Scripting languages, on the other hand, are typicallyused to perform housekeeping tasks that don’t place muchdemand on the processor, and that often don’t need to befinished quickly. Because of this, the relative inefficiency ofon-the-fly interpretation instead of optimized compilation isnot a problem. Indeed, by making it easy for users to writeand test programs quickly, the interpreter makes it mucheasier for administrators and others to create simple but

422 search engineuseful tools for monitoring the system and extracting necessaryinformation. Scripting languages can also be used toquickly create a prototype version of a program that will belater recoded in a language such as C++ for efficiency.Scripting languages were originally written for operatingsystems that process text commands. However, with thepopularity of Microsoft Windows, Macintosh, and variousUNIX-based graphical user interfaces, many users and evensystem administrators now prefer a visual scripting environment.For example, Microsoft Visual Basic for Windows(and the related Visual Basic for Applications and VBScript)allow users to write simple programs that can harnessthe features of the Windows operating system and userinterface and take advantage of prepackaged functionalityavailable in ActiveX controls (see BASIC). In these visualenvironments the tasks that had been performed by scriptfiles can be automated by setting up and linking appropriateobjects and adding code as necessary.Web ScriptingAside from shell programming, the most common use ofscripting languages today is to provide interactive featuresfor Web pages and to tie forms and displays to data sources.On the Web server, such technologies as ASP (see activeserver pages) use scripts embedded in (or called from) theHTML code of the page. On the client side (i.e., the user’sWeb browser) languages such as JavaScript and VBScriptcan be used to add features.(For specific scripting languages, see awk, Javascript,Lua, VBScript, Perl, PHP, and TCL. For general-purposelanguages that have some features in common with scriptinglanguages, see Python and Ruby.)Further ReadingBarron, David. The World of Scripting Languages. New York: Wiley,2000.Brown, Christopher. “Scripting Languages.” Available online. URL:http://cbbrowne.com/info/scripting.html. Accessed August 20,2007.Foster-Johnson, Eric, John C. Welch, and Micah Anderson. BeginningShell Scripting. Indianapolis: Wiley, 2005.Ousterhout, John K. “Scripting: Higher Level Programming for the21st Century.” IEEE Computer, March 1998. Available online.URL: http://www.tcl.tk/doc/scripting.html. Accessed August20, 2007.“Scriptorama: A Slightly Skeptical View on Scripting Languages.”Available online. URL: http://www.softpanorama.org/Scripting/index.shtm.Accessed August 20, 2007.Sebesta, Robert W. Concepts of Programming Languages. 8th ed.Boston: Pearson/Addison-Wesley, 2007.search engineBy the mid-1990s, many thousands of pages were beingadded to the World Wide Web each day (see World WideWeb). The availability of graphical browsing programs suchas Mosaic, Netscape, and Microsoft Internet Explorer (seeWeb browser) made it easy for ordinary PC users to viewWeb pages and to navigate from one page to another. However,people who wanted to use the Web for any sort of systematicresearch found they needed better tools for findingthe desired information.There are basically three approaches to exploring theWeb: casual “surfing,” portals, and search engines. A usermight find (or hear about) an interesting Web page devotedto a business or other organization or perhaps a particulartopic. The page includes a number of featured links to otherpages. The user can follow any of those links to reach otherpages that might be relevant. Those pages are likely to haveother interesting links that can be followed, and so on.Most Web users have surfed in this way: It can be fun andit can certainly lead to “finds” that can be bookmarked forlater reference. However, this approach is not systematic,comprehensive, or efficient.Alternatively, the user can visit a site such as the famousYahoo! started by Jerry Yang and David Filo (see portaland Yahoo!). These sites specialize in selecting what theireditors believe to be the best and most useful sites for eachtopic, and organizing them into a multilevel topical index.The portal approach has several advantages: The work ofsifting through the Web has already been done, the indexis easy to use, and the sites featured are likely to be of goodquality. However, even Yahoo!’s busy staff can examine onlya tiny portion of the estimated 1 trillion or so Web pagesbeing presented on about 175 million different Web sites(as of 2008). Also, the sites selected and featured by portalsare subject both to editorial discretion (or bias) and in somecases to commercial interest.Anatomy of a Search EngineSearch engines such as Lycos and AltaVista were introducedat about the same time as portals. Although thereis some variation, all search engines follow the same basicapproach. On the host computer the search engine runsautomatic Web searching programs (sometimes called “spiders”or “Web crawlers”). These programs systematicallyvisit Web sites and follow the links to other sites and so onthrough many layers. Usually, several such programs arerun simultaneously, from different starting points or usingdifferent approaches in an attempt to cover as much of theWeb as possible. When a Web crawler reaches a site, itrecords the address (URL) and compiles a list of significantwords. The Web crawlers give the results of their searchesto the search engine’s indexing program, which adds theURLs to the associated keywords, compiling a very largeword index to the Web.Search engines can also receive information directlyfrom Web sites. It is possible for page designers to add aspecial HTML “metatag” that includes keywords for use bysearch engines. However, this facility can be misused bysome commercial sites to add popular words that are notactually relevant to the site, in the hope of attracting morehits.To use a search engine, the user simply navigates to thesearch engine’s home page with his or her Web browser.(Many browsers can also add selected search engines to aspecial “search pane” or menu item for easier access.) Theuser then types in a word or phrase. Most search enginesaccept logical specifiers (see Boolean operators) such as

search engine 423AND, OR, or NOT. Thus, a search for “internet and statistics”will find only pages that have both words. Someengines also allow for phrases to be put in quote marks sothey will be searched for as a whole. A search for “internetstatistics” will match only pages that have these two wordsnext to each other.Because of the huge size of the Web, even seeminglyesoteric search words can yield thousands of “hits”(results). Therefore, most search engines rank the resultsby analyzing how relevant they are likely to be. This canbe done in a simple way by comparing the frequency withwhich the search terms appear on the various pages. Moresophisticated search engines such as Google can determinehow relevant a word or phrase seems to be becauseof its placement or presence in a heading or how often asite is referred to from other sites (see Google). Somesearch engines also offer the ability to “refine” searches byadding further words and performing a new match againstthe set of results.Limitations and Future of Search EnginesSearch engines do provide many useful “hits” for bothcasual and professional researchers, but the current technologydoes have a number of limitations. Even the mostcomprehensive search engines now reach and index only asmall fraction of the total available Web pages. One way tomaximize the number of pages searched is to use a “metasearch”program such as Copernic, which submits a user’ssearch to many different search engines. It then collates theresults, removing duplicates and attempting to rank themin relevance.Even with “relevancy” algorithms, searches for broad,general topics are likely to retrieve many less-than-usefulhits. Also, current search engines have difficulty findingimage and sound (music) files, which are among themost sought-after Web content. This is because the searchengine cannot recognize graphics or sound as such, onlyfile names or extensions or text descriptions. Searchengines also vary considerably in their ability to read andindex files in proprietary text formats such as MicrosoftWord or Adobe PDF.Once mainly an auxiliary tool for Web portals, searchengines have become a major business, and a variety ofnew types of search engines have proliferated. By combiningsearch with paid advertising and delivery of a varietyof services, Google in particular has become one of theWeb’s biggest success stories. In turn, Web-site owners haveattempted to use various techniques to “optimize” or raisethe ranking of their pages in search results, while Googlehas quietly tweaked its “page rank” algorithm to keep suchefforts in check.Two major search trends that can be seen in Googleare specialized searches and local search. Google offers avariety of search options to target images, video, news, evenblogs. Local search (such as Google Maps) combines mapswith lists of local businesses, making it easier for users tofind, for example, hotels near a given airport (see mappingand navigation systems). Services such as Google MapsStreet View even provide for a street-level closeup view ofCopernic, a “metasearch engine,” can pass a user’s request to manydifferent search engines and then prioritize and collate the results,weeding out duplicates. (Unfortunately some results are still muchless useful than others.)a neighborhood—almost a virtual tour, although this hasraised privacy concerns. Google offers an extensive programminginterface that is available to Web developers, aswell as an easier-to-use facility for creating custom mapdisplays (see mashups).In the future artificial intelligence techniques may makeit possible for search engines to recognize types of imagesor sounds through pattern recognition. Search engines maybe able to respond more appropriately to “natural language”queries such as “How many pages are there on the Web?”and find the answer, or at least Web pages that are likely tohave the answer. (Current services of this type such as Ask.com tend to give hit-and-miss results.)For now, search engines remain a useful tool, but systematicresearchers should complement their results with linksfrom portals and recommendations from authoritative sites.Further ReadingBatelle, John. The Search: How Google and Its Rivals Rewrote theRules of Business and Transformed Our Culture. New York:Penguin, 2005.Dornfest, Rael, Paul Bausch, and Tara Calishain. Google Hacks:Tips & Tools for Finding and Using the World’s Information. 3rded. Sebastapol, Calif.: O’Reilly, 2006.Kent, Peter. Search Engine Optimization for Dummies. Hoboken,N.J.: Wiley, 2006.Milstein, Sarah, J. D. Biersdorfer, and Matthew MacDonald. Google:The Missing Manual. 2nd ed. Sebastapol, Calif.: O’ReillyMedia, 2005.Moran, Mike, and Bill Hunt. Search Engine Marketing, Inc.: DrivingSearch Traffic to Your Company’s Web Site. Upper Saddle River,N.J.: IBM Press, 2005.Purvis, Michael, Jeffrey Sambells, and Cameron Turner. BeginningGoogle Maps Applications with PHP and Ajax: From Novice toProfessional. Berkeley, Calif.: Apress, 2006.

424 semantic WebSearch Engine Watch. Available online. URL: http://searchenginewatch.com/.Accessed August 21, 2007.semantic WebThe ever-growing World Wide Web consists of billions oflinked HTML documents (and other resources), but most ofthe links contain no information about why the linkage hasbeen made or what it might mean. Services such as Googlecan automatically trace the links and index each page (seesearch engine) with the aid of “metadata” such as keywordsthat summarize page content. However, discoveringthe relationships between data items on pages, or betweenpages—and their meaning, or semantics—requires humanscrutiny.In his 1999 book Weaving the Web, World Wide Web creatorTim Berners-Lee (see Berners-Lee, Tim) described a newway in which Web pages might be organized in the future:I have a dream for the Web [in which computers] becomecapable of analyzing all the data on the Web—the content,links, and transactions between people and computers. A“Semantic Web,” which should make this possible, has yetto emerge, but when it does, the day-to-day mechanisms oftrade, bureaucracy and our daily lives will be handled bymachines talking to machines. The “intelligent agents” peoplehave touted for ages will finally materialize.In other words, by encoding definitions of objects andtheir relationships into the text of Web pages, programs(see software agent) can be written to use this informationto answer sophisticated questions such as “whichdevices from this vendor use open-source software?”ApproachesThe development of “machine understandable” Web resourcesrequires that several layers of language be used. At bottomis the basic description of the structure of a document andits elements, such as titles or descriptions (see xml). Nextcomes RDF (Resource Description Format), which describesthe relationship between data objects (“resources”). Theserelationships might include “a motherboard is a part of acomputer” or “John owns this computer.” Programs are nowavailable to automatically create RDF statements given adatabase and its defined characteristics.For these relationships to be truly useful, they must bepart of a larger structure that describes their meaning. Thiscan be provided via an RDF scheme or through the use of alanguage such as the Web Ontology Language (OWL)—seeontologies and data models.Programs can then query for these relationships using alanguage such as SPARQL.ApplicationsThe semantic Web is not something that can appear overnight—afterall, it will take considerable human effort toencode the information needed for machines to understandWeb resources, and additional effort to code the applicationprograms that will take advantage of that information.However, the potential payoff is huge, allowing both humanand automated searchers to tackle much more sophisticatedtasks.For example, the University of Maryland is developinga prototype semantic search engine called Swoogle. It canextract information and determine relationships betweendocuments that include RDF or OWL elements. Swooglecan also help users find appropriate ontologies for exploringa subject (see ontologies and data models).Much research needs to be done. For example, there isthe problem of deriving a measure of “reliability” or “trust”based on the data sources used to answer the query, whichmay be scattered all over the world and represent very differentkinds of sources.Further ReadingAlesso, H. Peter, and Craig F. Smith. Thinking on the Web: Berners-Lee, Gödel, and Turing. New York: Wiley, 2006.Antoniou, Grigoris, and Frank van Harmelen. A Semantic WebPrimer. Cambridge, Mass.: MIT Press, 2004.Davies, John, Rudi Studer, and Paul Warren. Semantic Web Technologies:Trends and Research in Ontology-Based Systems.Hoboken, N.J.: Wiley, 2006.Swartz, Aaron. “The Semantic Web in Breadth.” Available online.URL: http://logicerror.com/semanticWeb-long. Accessed November13, 2007.Swoogle [semantic Web search engine]. Available online. URL:http://swoogle.umbc.edu/index.php. Accessed November 3,2007.senior citizens and computingA growing number of people 50 and older have beenlearning how to use computer technology and especiallyapplications such as e-mail and Web browsing. However,a substantial number of seniors have expressed reluctanceto join the digital world—as of January 2006, thePew Internet & American Life Project found that only 34percent of persons 65 and over were online. Some reasonswhy seniors have avoided the technology include the following:• the belief that it would be too hard to learn to use it• uncertainty about what can be done online andwhether it is worth the effort• fear of well-publicized dangers such as viruses andidentity theft• the expense of a personal computer and InternetaccessFortunately a number of these factors are graduallybeing ameliorated. There are numerous books and courses(such as at adult education or senior centers) that introducethe essentials of computing to seniors. Properly installedsecurity and filtering software, together with some usereducation, can minimize the chances of being victimizedonline. Finally, Internet-capable PCs are now available foraround $300 or less, though the cost of broadband accesshas not fallen as rapidly as that of hardware.

service-oriented architecture 425Seniors and the InternetAccording to research by the Pew Internet & AmericanLife Project, for seniors who do go online, e-mail is themost popular activity (and something shared with otherage groups). While teens are most prolific at adopting newtechnologies such as instant messaging, content sharing,and social networking, older users are less likely to adoptemerging services, but more likely to bank or make travelreservations online—perhaps reflecting their having moremoney for leisure travel. Older people also tend to be moreavid in pursuing health information. On the other hand,buying things online seems to be equally popular with allage groups.Computer technology can also assist seniors with theactivities of daily life. At the Quality of Life TechnologiesCenter, researchers from Pitt and Carnegie Mellon Universitiesare developing technologies including:• robotic wheelchairs with arms that can manipulateobjects and even assist in cooking meals• systems to help people get out of bed, dress, bathe,and so on• pervasive sensor networks that can monitor personsas they move around• monitoring systems that can detect growing confusionor cognitive impairment and call for help• systems to supervise daily activities and make suremedications are taken on time• “coaching” software that can help maintain memoryand cognitive skills, even in persons with Alzheimer’sdisease(See disabled persons and computing.)Further Reading“Abby & Me.” Available online. URL: http://www.abbyandme.com.Accessed November 14, 2007.Fox, Susannah, and Mary Madden. “Are ‘Wired Seniors’ SittingDucks?” Pew Internet & American Life Project, April 2006.Available online. URL: http://www.pewinternet.org/pdfs/PIP_Wired_Senior_2006_Memo.pdf. Accessed November 14,2007.———. “Generations Online.” Pew Internet & American LifeProject, December 2005. Available online. URL: http://www.pewinternet.org/pdfs/PIP_Generations_Memo.pdf. AccessedNovember 13, 2007.Rolstein, Gary. “Robotic Aids for the Disabled and Elderly.” PittsburghPost-Gazette, November 14, 2007. Available online.URL: http://www.post-gazette.com/pg/07318/833537-114.stm.Accessed November 14, 2007.Stokes, Abby. It’s Never Too Late to Love a Computer: Everything YouNeed to Know to Plug In, Boot Up and Get Online. Revised ed.New York: Workman Publishing, 2005.Stuur, Addo. Internet and E-mail for Seniors with Windows Vista.Visual Steps Publishing, 2006.serial portThere are basically two ways to move data from a computerto or from a peripheral device such as a printer or modem.A byte (8 bits) of data can be moved all at once, with eachbit traveling along its own wire (see parallel port). Alternatively,a single wire can be used to carry the data one bitat a time. Such a connection is called a serial port.The serial port receives data a full byte at a time fromthe computer bus and uses a UART (Universal AsynchronousReceiver-Transmitter) to extract the bits one at a timeand send them through the port. A corresponding circuitat the other end accumulates the incoming bits and reassemblesthem into data bytes.The data bits for each byte are preceded by a start-bit tosignal the beginning of the data and terminated by an stopbit.Depending on the application, an additional bit may beused for parity (see error correction). Devices connectedby a serial port must “negotiate” by requesting a particularconnection speed and parity setting. Failure to agree resultsin gibberish being received.The official standard for serial transmission is called RS-232C. It defines various additional pins to which wires areconnected, such as for synchronization (specifying whenthe device is ready to send or receive data) and ground.Physically, the old-style connectors are called DB-25because they contain 25 pins (many of which are not used).Most newer PCs have DB-9 (i.e. nine pin) connectors. A“gender changer” can be used in cases where two devicesboth have male connectors (with pins) or female connectors(with corresponding sockets).Because they use a single data transmission line andinclude error-correction, serial cables can be longer thanparallel cables (25 feet or more, as opposed to 10–12 feet).Serial transmission is generally slower (at up to 115,200bits/second) than parallel transmission. Serial connectionshave generally been used for such devices as modems(whose speed is already limited by phone line characteristics),keyboards, mice, and some older printers. Today thefaster and more flexible USB (see universal series bus)is replacing serial connections for many devices includingeven keyboards.Further ReadingPeacock, Craig. “Interfacing the Serial / RS232 Port.” Availableonline. URL: http://www.beyondlogic.org/serial/serial.htm.Accessed August 21, 2007.Tyson, Jeff. “How Serial Ports Work.” Available online. URL: http://computer.howstuffworks.com/serial-port.htm. Accessed August21, 2007.service-oriented architecture (SOA)The traditional model for organizing information processing,particularly in large installations, is in terms of installingand maintaining large applications that each providemany functions, and then devising ways for the applicationsto exchange data and otherwise coordinate with each other.As the information environment has become more complex(particularly with regard to databases and Web-relatedservices), this approach has become more cumbersome, lessflexible, and harder to maintain.

426 Shannon, Claude E.Service-oriented architecture is a new approach thatfocuses on services (basic functions, such as displayingand processing forms or formatting data) and providesstandardized ways for them to be accessed by programs.Applications in turn are then built up by “plugging in” therequired services and organizing them to meet the requiredlogic and sequence of processing.In order to be accessed, each service provides “metadata”(usually in XML files) that describes what data isused by a service and what it provides. The descriptionitself can be provided using Web Services Description Language(WSDL), including network addresses (ports) forconnecting to the service, the operations supported, andthe abstract format of the expected data. (For more on themessage protocol, see soap.)There are three basic roles that must be filled in designingan SOA system: The service provider creates a service(often a Web service) and “exposes” aspects of the serviceand controls access to it (through security policies). Theservice broker provides a registry of available services andtells requesters how to connect to them. (For more on brokers,see corba.) Finally, the requestor in an applicationfinds and requests services as needed.In general SOA can be seen as part of the trend towarddecentralized, loosely coupled computing (see distributedcomputing). Because all services communicate throughthe network, it is easy to reallocate or scale up services asneeded. It is also easier to upgrade software and reuse it fornew applications. (For more on combining services providedby applications, see mashups.) However, SOA bringschallenges of its own in terms of making services trulyinteroperable and conforming to standards that are stillevolving.went on to make important contributions to the young disciplineof artificial intelligence (AI).Shannon was born in Gaylord, Michigan, on April 30,1916. He received bachelor’s degrees in both mathematicsand electrical engineering at the University of Michigan in1936. He went on to MIT, where he earned a master’s degreein electrical engineering and a Ph.D. in mathematics, bothin 1940. Shannon’s background thus well equipped himto relate mathematical concepts to practical engineeringissues.While a graduate student at MIT, Shannon was incharge of programming an elaborate analog computercalled the Differential Analyzer that had been built byVannevar Bush (see analog computer and Bush, Vannevar).Actually “programming” is not quite the rightword: To solve a differential equation with the DifferentialAnalyzer, it had to be translated into a variety of physicalsettings and arrangements of the machine’s intricate electromechanicalparts.The Differential Analyzer was driven by electrical relayand switching circuits. Shannon became interested in theunderlying mathematics of these control circuits. He realizedthat their fundamental operations corresponded to theBoolean algebra he had studied in undergraduate mathematicsclasses (see Boolean operators). It turned out that theseemingly abstract Boolean AND, OR and NOT operationshad a practical engineering use. Shannon used the resultsof his research in his 1938 M.S. thesis, titled “A SymbolicAnalysis of Relay and Switching Circuits.” This work washonored with the Alfred Nobel prize of the combined engineeringsocieties (this is not the same as the more famousNobel Prize).Further ReadingErl, Thomas. SOA Principle of Service Design. Boston: Pearson Education/PrenticeHall, 2007.Hurwitz, Judith, et al. Service Oriented Architecture for Dummies.Hoboken, N.J.: Wiley, 2007.Josuttis, Nicolai M. SOA in Practice: The Art of Distributed SystemDesign. Sebastapol, Calif.: O’Reilly, 2007.QAT SOA Resource Center. Available online. URL: http://www.soaresourcecenter.com/. Accessed November 14, 2007.Service-Oriented Architecture (SOA). TechRepublic. Availableonline. URL: http://search.techrepublic.com.com/search/Service-Oriented+Architecture+( SOA).html. Accessed November14, 2007.Weerawarana, Sanjiva, et al. Web Services Platform Architecture.Upper Saddle River, N.J.: Prentice Hall PTR, 2005.Shannon, Claude E.(1916–2001)AmericanMathematician, Computer ScientistThe information age would not have been possible withouta fundamental understanding of how information couldbe encoded and transmitted electronically. Claude ElwoodShannon developed the theoretical underpinnings for moderninformation and communications technology and thenClaude Shannon developed the fundamental theory underlyingmodern data communications, as well as making contributions tothe development of artificial intelligence. (Lucent TechnologiesBell Labs)

shareware and freeware 427Along with the work of Alan Turing and John von Neumann(see Turing, Alan and von Neumann John), Shannon’slogical analysis of switching circuits would becomeessential to the inventors who would build the first digitalcomputers in just a few years. (Demonstrating the breadth ofhis interests, Shannon’s Ph.D. thesis would be in an entirelydifferent application—the algebraic analysis of problems ingenetics.)In 1941, Shannon joined Bell Laboratories, perhapsAmerica’s foremost industrial research organization. Theworld’s largest phone company had become increasinglyconcerned with how to “scale up” the burgeoning telephonesystem and still ensure reliability. The coming of waralso highlighted the importance of cryptography—securingone’s own transmissions while finding ways to breakopponents’ codes. Shannon’s existing interests in both datatransmission and cryptography neatly dovetailed with theseneeds.Shannon’s paper titled “A Mathematical Theory of Cryptography”would be published after the war. But Shannon’smost lasting contribution would be to the fundamental theoryof communication. His formulation would explain whathappens when information is transmitted from a sender toa receiver—in particular, how the reliability of such transmissioncould be analyzed (see information theory).Shannon’s 1948 paper, “A Mathematical Theory ofCommunication” was published in The Bell System TechnicalJournal. Shannon identified the fundamental unit ofinformation (the binary digit, or “bit” that would becomefamiliar to computer users). He showed how to measure theredundancy (duplication) within a stream of data in relationto the transmitting channel’s capacity, or bandwidth.Finally, he showed methods that could be used to automaticallyfind and fix errors in the transmission. In essence,Shannon founded modern information theory, which wouldbecome vital for technologies as diverse as computer networks,broadcasting, data compression, and data storage onmedia such as disks and CDs.One of the unique strengths of Bell Labs is that it didnot limit its researchers to topics that were directly relatedto telephone systems or even data transmission in general.Like Alan Turing, Shannon became interested after the warin the question of whether computers could be taught toperform tasks that are believed to require true intelligence(see artificial intelligence). He developed algorithmsto enable a computer to play chess and published an articleon computer chess in Scientific American in 1950. He alsobecame interested in other aspects of machine learning, andin 1952 he demonstrated a mechanical “mouse” that couldsolve mazes with the aid of a circuit of electrical relays.The mid-1950s would prove to be a very fertile intellectualperiod for AI research. In 1956, Shannon and AIpioneer John McCarthy (see McCarthy, John) put out acollection of papers titled “Automata Studies.” The volumeincluded contributions by two other seminal thinkers, Johnvon Neumann and Marvin Minsky (see Minsky, Marvin).Although he continued to do research, by the late 1950sShannon had changed his emphasis to teaching. As DonnerProfessor of Science at MIT (1958–1978) his lecturesinspired a new generation of AI researchers. During thesame period Shannon also explored the social impact ofautomation and computer technology as a Fellow at theCenter for the Study of Behavioral Sciences in Palo Alto,California.Shannon received numerous prestigious awards, includingthe IEEE Medal of Honor and the National Medal ofTechnology (both in 1966). Shannon died on February 26,2001, in Murray Hill, New Jersey.Further ReadingShannon, Claude Elwood. “A Chess-Playing Machine.” ScientificAmerican, February 1950, 48–51.———. Collected Papers. Ed. N. J. A. Sloane and Aaron D. Wyner.New York: IEEE Press, 1993.———. “A Mathematical Theory of Communication.” Bell SystemTechnical Journal 27; July and October, 1948, 379–423, 623–656. Available online. URL: http://plan9.bell-labs.com/cm/ms/what/shannonday/shannon1948.pdf. Accessed August 21,2007.Waldrop, M. Mitchell. “Claude Shannon: Reluctant Father of theDigital Age.” Technology Review, July/Aug. 2001. Available online.URL: http://www.technologyreview.com/Infotech/12505/.Accessed August 21, 2007.shareware and freewareThe early users of personal computers generally had considerabletechnical skill and a desire to write their ownprograms. This was partly by necessity: If one wanted toget an Apple, Atari, Commodore, or Radio Shack machineto perform some particular task, chances were one wouldhave to write the software oneself. Commercial softwarewas scarce and relatively expensive. However, given enoughtime, it was possible for hobbyists to write programs usingthe machine’s built-in BASIC language or (with more effort)assembly language.Programs such as utilities and games were often freelyshared at gatherings of PC enthusiasts (see user groups).Many talented amateur programmers considered trying toturn their avocation into a business. However, a utility toprovide better file listings or a colorful graphics programthat creates kaleidoscopic images was unlikely to interestthe commercial software companies who developed largeprograms in-house for marketing primarily to business.In 1982, Andrew Fuegelman created a program calledPC-Talk. This program provided a better way for users withmodems to connect to the many bulletin board systemsthat were starting to spring up. Fluegelman was familiarwith the common practice of public radio and TV broadcastersof soliciting pledge payments to help support their“free” service. He decided to do something similar with hisprogram. He distributed it to many bulletin boards, whereusers could download it for free. However, he asked userswho liked the program and wanted to continue to use it topay him $25.Fluegelman dubbed his method of software distribution“freeware” (because it cost nothing to try out the program).Other programmers began to use the same method withtheir own software. This included Jim Knopf, author of thePC-File database program, and Bob Wallace, who offered

428 shellPC-Write as a full-featured alternative to expensive commercialword processing program. Because Fluegelman hadtrademarked the term freeware, these other authors beganto call their offerings shareware.Today freeware means software that can be downloadedat no cost and for which there is no charge for continueduse. The program may be redistributed by users as long asthey don’t charge for it.Shareware, on the other hand, follows Fluegelman’soriginal concept. The software can be downloaded for free.The user is allowed to try the program for a limited period(either a length of time such as 30 days, or a maximumnumber of times that the program can be run). After thetrial period, the user is expected to pay the author thespecified fee of continued use. (Today this is usually donethrough the author’s Web site or a service that can acceptsecure credit card payments online.) Once the user pays,he or she receives either an unrestricted version of the softwareor frequently, an alphanumeric key that can be typedinto the program to remove all restrictions. At this pointthe program is said to be “registered.”Users can be encouraged (or forced) to pay in variousways. Some programs keep working after the trial period,but display continual “nag” messages or remove some functionality,such as the ability to print or save one’s work.(“Demos” of commercial games or other programs also havelimited functionality, but cannot be registered or upgraded.They are there simply to entice consumers to buy the commercialproduct.)Alternatively, some shareware authors prefer to enticetheir users to register by offering bonuses, such as additionalfeatures, free upgrades, or additional technical support.Sometimes (as with the RealPlayer streaming soundand video player and the Eudora e-mail program) a usefulbut limited “lite” version is offered as freeware, but usersare encouraged to upgrade to a more full-featured “professional”version.Shareware has been a moderately successful businessfor a number of program authors. For example, Phil Katz’sPKZip file compression and packaging program is so usefulthat it has found its way onto millions of PCs, and enoughusers paid for the program to keep Katz in business. (PKZipand its cousin WinZip are examples of shareware programsthat became so popular that they spawned commerciallypackaged versions.)Shareware and freeware should be distinguished frompublic domain and open source software (see open-sourcemovement). Public domain software is not only free (aswith freeware), but the author has given up all rights includingcopyright, and users are free to alter the program’s codeor to use it as part of a new program. Open-source software,on the other hand, allows users free access to the softwareand its source code, but with certain restrictions—notably,that it not be used in some other product for which accesswill be restricted.Today tens of thousands of shareware and freeware programsare available on the Internet via ftp archives, author’sWeb sites, and giant online libraries maintained by zdnet.com, cnet.com, tucows.com, and others.Further ReadingAssociation of Shareware Professionals. Available online. URL:http://www.asp-shareware.org. Accessed August 21, 2007.Ellis, Robert. Handpicked Software for Mac OS X: The Best NewFreeware, Shareware, and Commercial Software for Mac OS X.Petaluma, Calif.: Futurosity, 2002.Hasted, Edward. Software That Sells: A Practical Guide to Developingand Marketing Your Software Project. Indianapolis: Wiley, 2005.Lehnert, Wendy G. The Web Wizard’s Guide to Freeware and Shareware.Boston: Addison-Wesley, 2002.Shareware.com. Available online. URL: http://www.shareware.com. Accessed August 21, 2007.Tucows.com. Available online. URL: http://www.tucows.com.Accessed August 21, 2007.shellDuring the 1950s, using a computer generally meant thatoperators submitted batch-processing command cards (seejob control language) that controlled how each programwould use the computer’s resources. One programran at a time, and interaction with the user was minimal.However, when time-sharing computers began to appearin the 1960s, users gained the ability to control the computerinteractively from terminals. The operating systemtherefore needed to have a facility that would interpret andexecute the commands being typed in by the users, such asa request to list the files in a directory or to send a file to theprinter. This command interpreter is called a shell.To see a simple shell in action, a Windows user needonly bring up a command prompt, type the word dir, andpress Enter. A shell called command.com provides the userinterface for users of IBM PC-compatible systems runningMS-DOS. The command processor displays a prompt onthe screen. It then interprets (see parsing) the user’s commands.If the command involves one of the shell’s internaloperations (such as “dir” to list a file directory), it simplyexecutes that routine. For example the command:dir temp /pwould be interpreted as a call to execute the dir function,passing it the name “temp” (a directory) and the /p, which dirinterprets as a “switch” or instruction telling it to pause thedirectory listing after each screenful of text. If the commandis an external MS-DOS utility such as “xcopy” (a file copyingprogram), the shell runs that program, passing it the information(mainly file names) from the command line. Finally,the shell can run any other executable program on the system.It is then that program’s responsibility to interpret andact upon any additional information that was provided.MS-DOS also has the ability for the command.com shell toread a series of commands stored in a text file called a batchfile, and having the *.bat (batch) extension. This allowed forrudimentary scripting of system housekeeping operations orother routine tasks (see scripting languages).UNIX ShellsMS-DOS largely faded away in the 1990s as more usersswitched to Microsoft Windows and begun to use a graphicaluser interface to control their machines. However, shells

shell 429have achieved their greatest proliferation and elaborationwith UNIX, the operating system developed by Ken Thompsonand Dennis Ritchie starting in 1969 and widely used foracademic, scientific, engineering, and Web applications.UNIX shells serve the same basic purposes as the MS-DOS shell: interactive control of the operating system andthe ability to run stored command scripts. However, theUNIX shells have considerably more complex syntax andcapabilities.Part of the design philosophy of the UNIX system wasto place the core operating system functions in the kernel(see Kernel and UNIX). This modular design meant thatUNIX, unlike most other operating systems, did not have tocommit itself to a particular form of user interface or commandprocessor. Accordingly, a number of such processors(shells) have been developed, reflecting the programmingstyle preferences of their originators.The first shell to be developed was the Bourne Shell,named for its creator, Steven R. Bourne, who developed itat Bell Labs, the original home of UNIX. The Bourne shellimplemented some basic ideas that are characteristic ofUNIX: the ability to redirect input and output to and fromfiles, devices or other sources (using the < and > characters),and the ability to use “pipes” (the | character) to connectthe output of one command to the input of another.The next major development was the C shell (csh). TheBourne shell used a relatively simple and clean syntaxdevised by its creator. As the name suggests, the C shell(developed at the University of California, Berkeley) takesits syntax from the C programming language, which wasby far the most commonly used language on UNIX systems.One logical reason for this choice was that C programmerscould quickly learn to write scripts with the C shell. TheC shell also added support for job control (that is, movingprocesses between foreground and background operation)and in general was easier to use for interactively controllingprograms from the command line.UNIX users sometimes used both shells, since the simplerand more consistent syntax of the Bourne shell is generallythought to be better for writing scripts. (The twoshells also reflected the split in the UNIX world betweenthe version of the operating system provided by AT&T andthe variant developed at UC Berkeley.)David Korn at AT&T then decided to combine the bestfeatures of both shells. His Korn shell (Ksh) kept the betterscripting language features from the Bourne shell but addedjob-control and other features from the C shell. He alsoadded the programming language concept of functions (seeprocedures and functions), allowing for cleaner organizationof code.Another popular shell, BASH (Bourne Again Shell) wasdeveloped by the Free Software Foundation for GNU, anopen-source version of UNIX. BASH and Ksh share mostfeatures and both are compatible with POSIX, a standardspecification for connecting programs to the UNIX operatingsystem.The surge of interest in open-source UNIX in recentyears (see Linux) has brought a new generation of shellusers. Although modern Linux distributions provide a fullgraphical user interface (GUI)—indeed, a choice of them—such tasks as software installation and configuration ofteninvolve entering shell commands. Experienced users canalso find, copy, move, or otherwise manipulate batches offiles more efficiently in the shell than in using windows andmouse movements.Shell ScriptsRegardless of the version of the shell used, shell scriptswork in the same basic way. A shell script is a text filecontaining commands to the shell. The commands can usecontrol statements (see branching statements and loop)and invoke both the shell’s internal features and the manyhundreds of utility programs that are available on UNIXsystems (see scripting languages).Once the script is written, there are two ways to executeit. One way is to type the name of the shell at the commandprompt, followed by the name of the script file, as in:$ sh MyScriptAlternatively, the chmod (change mode) command can beused to mark the script’s file type as executable, and the firstline of the script then contains a statement that invokes theshell, which will parse the rest of the script. The script cannow be executed simply by typing its name at the commandprompt (or it can be included as a command in anotherscript).Here is a simple example of a shell script that prints outvarious items of information about the user and the currentsession on a UNIX system:#! /sbin/shecho My username: `whoami`echo My current directory: `pwd`echoecho My disk usage:du -kechoecho System status:uptimeif test -f log.txt; thencat log.txtelse echo Log file not foundfiThe first line tells UNIX which shell to use to interpretthe script (in this case the Bourne shell, sh, will beexecuted). The echo command simply outputs the text thatfollows it to the screen. “whoami” is a UNIX command thatprints the user’s name. The script takes advantage of aninteresting UNIX feature: The whoami command is put in“backquotes” (` `). This inserts the output of the whoamicommand (the user name) in place of that command, andthe resulting text is output by the echo command.The du command gives the user’s disk usage, while theuptime command gives some statistics about how manyusers are on the system and how long the system has beenrunning. Finally, the if statement at the end of the script

430 Simonyi, Charlestests for the presence of the file log.txt. If the file exists, itscontents are displayed by the “cat” command.When “myinfo” is typed at the UNIX prompt, the outputmight look like the following:$ myinfoMy username: hrhMy current directory: /home/h/r/hrhMy disk usage:132 ./.nn4 ./Mail48 ./.elm296 .System status:7:34pm up 56 day(s), 20:39, 73 users, loadaverage: 3.62, 3.45, 3.49This is a test file.Further ReadingGite, Vivek G. “Linux Shell Scripting Tutorial.” Available online.URL: http://www.freeos.com/guides/lsst/. Accessed August21, 2007.Kochan, Stephen, and Patrick Wood. Unix Shell Programming. 3rded. Indianapolis: Sams, 2003.Newham, Cameron. Learning the Bash Shell. 3rd ed. Sebastapol,Calif.: O’Reilly Media, 2005.Quigley, Ellie. UNIX Shells by Example. 4th ed. Upper Saddle River,N.J.: Prentice Hall, 2004.Robbins, Arnold, and Bill Rosenblatt. Learning the Korn Shell. 2nded. Sebastapol, Calif.: O’Reilly Media, 2002.Sobell, Mark G. A Practical Guide to Linux Commands, Editors, andShell Programming. Upper Saddle River, N.J.: Prentice Hall,2005.Simonyi, Charles(1948– )Hungarian-AmericanSoftware Engineer, EntrepreneurBorn in Budapest, Hungary, on September 10, 1948, CharlesSimonyi shaped the architecture of Microsoft’s dominantsoftware applications for many years, devised a new programmingparadigm and established a company to promoteit, and, along the way, became the fifth civilian “space tourist”to visit the International Space Station.Simonyi’s father was a professor of electrical engineering.In high school, Simonyi worked as a night watchmanat a computer laboratory. When he expressed his interest,one of the engineers taught him how to program; he soonwrote a compiler and sold it to a government department.After working for a Danish company for a couple of years,Simonyi moved to the United States in 1968, attending theUniversity of California, Berkeley, and earning a B.S. inengineering mathematics in 1972. Moving to Stanford Universityfor graduate study, Simonyi was also hired by XeroxPARC, where he shared ideas with innovators in computerinterfaces and networking. Simonyi received his Ph.D. incomputer science from Stanford in 1977. In his dissertationSimonyi showed his early interest in “metaprogramming”—thedevelopment of ways to coordinate programsand provide them with a higher-level context.In 1981 Simonyi applied directly to Bill Gates for a job(see Gates, Bill and Microsoft Corporation). At MicrosoftSimonyi took charge of the development of the productsthat would dominate the office software market bythe end of the 1980s, including Word and Excel. Simonyialso brought to Microsoft new program structure ideas thathe had seen at Xerox PARC—see object-oriented programming.At this time Simonyi also developed a standardsystem for naming variables that soon became known asHungarian notation in honor of his ancestry.The tremendous success of Simonyi as a software developer(and Microsoft’s gargantuan revenue) made Simonyiindependently wealthy. However, in 2002 he decided tostrike out on his own, founding a company called IntentionalSoftware with his business partner Gregor Kiczales.The company develops and promotes an approach tosoftware design called intentional programming. (Simonyihad developed forerunners of this concept at Microsoft, butapparently the latter company lost interest in it, perhapsprompting Simonyi’s departure.)To develop an application, software engineers usingintentional programming begin by building a “toolbox” ofspecific functions needed for the area in which the programis intended to operate (such as insurance or banking).Domain experts—people who have “real world” knowledgeof that area—use a special editor to create a description ofhow the application must operate; thus the program is in asense designed not by the programmers, but by the peoplewho will guide its use. The program development systemthen connects the tools to the description to generate thefinal code, which can then be refined. An important featureof this process is that the specific intentions about what theprogram needs to do are preserved along with the code,with the result largely self-documenting. It is argued thatthis makes subsequent testing and modification of the softwaremuch faster and easier. The first commercial versionof this development system is expected in 2008.Space Tourist and PhilanthropistIn April 2007 Simonyi, an experienced pilot, fulfilled a lifelonginterest in space by riding a Russian Soyuz spacecraftto the International Space Station; the 10-day “vacation” costhim about $20 million. Simonyi chronicled his preparationsand the trip itself via his “Nerd in Space” Web site. (Simonyialso sails in his sleek luxury yacht Skat.)As a philanthropist, Simonyi established a professorshipfor the Public Understanding of Science at Oxford University,as well one for Innovation in Teaching at Stanford. Hehas given tens of millions of dollars to various programsin the arts and sciences. As of 2007 Simonyi was datingdomestic arts entrepreneur and author Martha Stewart.While it remains uncertain how successful and influentialintentional programming will become, Simonyi hasbeen hailed by Bill Gates as “one of the great programmersof all time.”

simulation 431Further ReadingCharles in Space. Available online. URL: http://www.charlesinspace.com/. Accessed November 14, 2007.Greene, Stephen G. “Entrepreneur Seeks to Promote Excellencethrough Philanthropy.” Chronicle of Philanthropy 16 (February19, 2004): 20.Intentional Software. Available online. URL: http://www.intentsoft.com/. Accessed November 14, 2007.Rosenberg, Scott. “Anything You Can Do, I Can Do Meta: SpaceTourist and Billionaire Programmer Charles SimonyiDesigned Microsoft Office. Now He Wants to ReprogramSoftware.” Technology Review, January 2007. Available online.URL: http://www.technologyreview.com/Infotech/18047/?a=f.Accessed November 14, 2007.SimulaOne of the most interesting applications of computers isthe simulation of systems in which many separate actionsor events are happening simultaneously (see simulation).During the 1950s, Norwegian computer scientist KristenNygaard began to develop a more formal way of describingand designing simulations. A typical simulation consistsof a number of “objects,” such as cars in a traffic flow orcustomers waiting in a bank line. In a bank simulation,for example, the objects (customers) would demand servicefrom particular serving objects (teller windows). Theywould move in a queue and their motion would be capturedat various points of time.Nygaard used his ideas to create symbols and flow diagramsto represent the events going on in a simulation.However, existing computer languages such as Algol 60were designed to carry out procedures sequentially and oneat a time, not simultaneously. This made it difficult to writea program representing a situation in which many cars orcustomers were moving simultaneously.In the early 1960s, Nygaard was joined by Ole-JohanDahl, who had more experience with systems programmingand computer language design. They worked together tocreate a new language that they called Simula, reflectingtheir emphasis on simulation programming. In designingSimula, the authors sought to create a data structure thatwas better suited to simultaneous actions or events. Forexample, in a simulation of automobile traffic, each carwould be an “object” with data such as its location andspeed as well as actions or capabilities such as changingspeed or direction. The data for each object must be maintainedseparately and updated frequently.The Algol 60 language already had a way to define code“blocks” (see procedures and functions) that could containtheir own local data as well as actions to be performed.Further, such blocks could be called repeatedly such thatmany copies could be “open” at the same time. However,these calls were still essentially sequential, not simultaneous.In their new Simula 1 language (introduced in 1965),Dahl and Nygaard created a way to simulate simultaneousprocessing. Even though the computer would (probably)only have a single processor such that only one copy ofa block of code could be executing at a given time, Simulaset up special variables for keeping track of simulatedtime. Control would “jump” from one instance of a block toanother such that all blocks would, for example, have theiractions for the time 20:15 executed, then actions for 20:16would be executed, and so on. A list kept track of processesin time order. Thus, Simula 1 kept all the features of Algolbut made it more suitable for modeling simultaneous events(see multiprocessing).Simula 1 was quite successful as a simulation language,but the authors soon realized that the ability to use separateinvocations of a procedure to create individual “objects”had a more general application to representing data inapplications other than simulations. In creating Simula 67(the version of the language still used today), they thereforeintroduced the formal concept of the class as a specificationthat could be used to create objects of that type. Theyalso introduced the key idea of inheritance (where one classcan be derived from an earlier class), as well as a way that aderived class could redefine a procedure that it had inheritedfrom the original (base) class (see object-orientedprogramming and class).Although Simula 67 would continue to be used primarilyfor simulations rather than as a general-purpose programminglanguage, its object-oriented ideas would proveto be very influential. The designers of Smalltalk and Adawould look to Simula for structural ideas, and the popularC++ language began with an effort to create a “C withclasses” language along the lines of Simula. (See Smalltalk,Ada, and C++.)Further ReadingHolmevik, Jan-Rune. “Compiling Simula: a Study in the History ofComputing and the Construction of the SIMULA ProgrammingLanguages.” STS Report (Trondheim). Available online. URL:http://staff.um.edu.mt/jskl1/simula.html. Accessed August 21,2007.Nygaard, K., and O.-J. Dahl. “The Development of the Simula Languages”in The History of Programming Languages, R. L. Wexelblat,ed. New York: Academic Press, 1981.Pooley, R. Introduction to Programming with Simula. Oxfordshire,U.K.: Alfred Waller, 1987.Sebesta, Robert W. Concepts of Programming Languages. 7th ed.Boston: Addison-Wesley, 2006.Sklenar, J. “Introduction to OOP in Simula.” Available online.URL: http://staff.um.edu.mt/jskl1/talk.html. Accessed August21, 2007.simulationA simulation is a simplified (but adequate) model that representshow a system works. The system can be an existing,real-world one, such as a stock market or a human heart,or a proposed design for a system, such as a new factory oreven a space colony.If a system is simple enough (a cannonball falling froma height, for example), it is possible to use formulas suchas those provided by Newton to get an exact answer. However,many real-world systems involve many discrete entitieswith complex interactions that cannot be captured witha single equation. During the 1940s, scientists encounteredjust this problem in attempting to understand what wouldhappen under various conditions in a nuclear reaction.

432 singularity, technologicalTogether with physicist Enrico Fermi, two mathematicians,John von Neumann (see von Neumann, John) andStanislaw Ulam, devised a new way to simulate complexsystems. Instead of trying fruitlessly to come up with somehuge formula to “solve” the whole system, they appliedprobability formulas to each of a number of particles—in effect, “rolling the dice” for each one and then observingtheir resulting distribution and behavior. Because ofits analogy to gambling, this became known as the MonteCarlo method. It turned out to be widely useful not onlyfor simulating nuclear reactions and particle physics but formany other activities (such as bombing raids or the spreadof disease) where many separate things behave according toprobabilities.A number of other models and techniques have madeimportant contributions to simulation. For example, theattempt to simulate the operation of neurons in the brainhas led to a powerful technique for performing tasks suchas pattern recognition (see neural network). The applicationof simple rules to many individual objects can result inbeautiful and dynamic patterns (see cellular automata),as well as ways to model behavior (see artificial life).Here, instead of a system being simplified into a simulation,a simulation can be created in order to see what sort of systemsmight emerge.Software ImplementationBecause of the number of calculations (repeated for a singleobject and/or applied to many objects) required for an accuratesimulation, it is obviously useful for the simulationdesigner to have as much computer power as possible. Similarly,having many processors or a network of separate computersnot only increases the available computing power,but may make it more natural to represent different objectsor parts of a system by assigning each to its own processor.(This naturalness goes the other way, too: Simulation techniquescan be very important in modeling or predicting theperformance of computer networks including the Internet.)However, it is also important to have programming languagesand techniques that are suited for representing thesimultaneous changes to objects (see also multiprocessing).Using object-oriented languages such as Simula orSmalltalk makes it easier to package and manage the dataand operations for each object (see object-oriented programming,Simula, and Smalltalk).ApplicationsSimulations and simulation techniques are used for a tremendousrange of applications today. Besides helping withthe understanding of natural systems in physics, chemistry,biology, or engineering, simulation techniques are alsoapplied to human behavior. For example, the behavior ofconsumers or traders in a stock market can be exploredwith a simulation based on game theory concepts. Artificialintelligence techniques (such as expert systems) canbe used to give the individual “actors” in a simulation morerealistic behavior.Simulations are often used in training. A modern flightsimulator, for example, not only simulates the aerodynamicsof a plane and its response to the environment andto control inputs, but detailed graphics (and simulatedphysical motion) can make such training simulations feelvery realistic, if not quite to Star Trek holodeck standards.Whether for flight, military exercises, or stock trading, simulationscan provide a much wider range of experiences ina relatively short time than would be feasible (or safe) usingthe real-world activity. Simulations can also play an importantpart in testing software or systems or in predicatingthe results of business decisions or strategies.Simulations are also frequently sold as entertainment.Many commercial strategy and role-playing games as wellas vehicle simulators contain surprisingly complex simulationsthat make the games both absorbing and challenging(see computer games and online games). Such games canalso have considerable educational value.Further ReadingGilbert, Nigel, and Klaus G. Troitzsch. Simulation for the SocialScientist. 2nd ed. Maidenhead, Berkshire, U.K.: Open UniversityPress, 2005.Laguna, Manuel, and Johan Marklund. Business Process Modeling,Simulation, and Design. Upper Saddle River, N.J.: PrenticeHall, 2004.Rizzoli, Andrea Emilio. “A Collection of Modelling and SimulationResources on the Internet.” Available online. URL: http://www.idsia.ch/~andrea/simtools.html. Accessed August 21,2007.Ross, Sheldon M. Simulation. Burlington, Mass.: Elsevier AcademicPress, 2006.Shelton, Brett E., and David A. Wiley, eds. The Design and Use ofSimulation Computer Games in Education. Rotterdam, Netherlands:Sense Publishers, 2007.singularity, technologicalThe idea that an incomprehensible future is rushing downon us goes back at least as far as Alan Toffler’s book FutureShock (1970). Toffler suggested that fundamental changesin society brought about by industrial and postindustrialdevelopments were creating psychological stress and disorientation.Future shock can be thought of as a steep line on a graphthat represents the complexity of technological society. Butwhat if the line were asymptotic, approaching the verticaland then disappearing? This is what science fiction writerVernor Vinge described in the 1980s as the “technologicalsingularity.” In physics, a singularity is a place wherelaws break down, such as at the center of a black hole. Byanalogy, Vinge suggested that the development of artificialintelligence and related technologies would reach a pointwhere intelligent machines would drive their own furtherdevelopment, with their design and operation far outstrippinghuman understanding. Once intelligent machinescreate even more intelligent machines (and so on), moretechnological progress might occur in a decade or two thanin the preceding thousands of years.An obvious question is whether the singularity is in factcoming, and if so, when. Inventor and futurist Ray Kurzweilargues that history (including the accuracy of Moore’s lawof doubling computational power) shows that technological

Smalltalk 433progress is indeed exponential. In his book The SingularityIs Near, Kurzweil predicts that the threshold will bereached in the 2040s, leading to “technological change sorapid and profound it represents a rupture in the fabric ofhuman history.”There are a number of contrary views. First, there arethose who argue that there are fundamental reasons whycomputers will never achieve truly human-equivalent intelligence,let alone surpass it (see, for example, Dreyfus,Hubert). Others argue that the present rate of accelerationwill not necessarily continue, and that human-level AImay still be achievable, but only in centuries rather than adecades.Responding to the SingularityWhat happens if there is a singularity is the stuff of muchspeculation and science fiction. “Super AI” might lead tothe development of technologies such as the ability to storeor transfer the contents of a human brain, making peopleeffectively immortal. On the other hand, superhumanintelligences might be indifferent to, or worse, hostile to,humanity. Super AI might also foster technologies such asgenetic engineering or nanotechnology that have promisesand dangers of their own.There have been a number of responses to such dangers.Some critics (see, for example, Joy, Bill) urge that a limitingframework be put in place to prevent certain areas ofresearch from getting out of hand. Others, such as EliezerYudkowsky of the Singularity Institute for Artificial Intelligence,want to ensure that “seed” AIs (intelligences capableof improving themselves) have safeguards and dispositionsthat would make them place a high regard on human interests,rather like Isaac Asimov’s “three laws of robotics.”Another suggested approach is to use the growingknowledge of the detailed structure and function of thehuman brain to enhance or augment cognitive function. Forexample, a mathematician might think about a problem andseamlessly retrieve data from both personal memory and theWorld Wide Web, then carry out symbolic manipulationsand calculations at electronic speed, all via brain implants.A “Soft Singularity?”While the likelihood of computer software exceedinghuman intelligence remains a subject for speculation andcontroversy, existing phenomena (and trends) in softwaredesign and computer-mediated communication (see socialnetworking) suggest that a new level of complexity andsophistication is rapidly emerging. As information is beingincreasingly coded for meaning (see semantic Web) andprograms are acting more autonomously (see artificiallife and software agent), one might say the Web is startingto understand itself, if not yet becoming conscious inthe human sense. In turn, the augmentation of humancognition is already well underway. Thus many potentialeffects of the singularity are already significant issues.Further ReadingBrin, David. “Singularities and Nightmares: Extremes of Optimismand Pessimism about the Human Future.” Availableonline. URL: http://lifeboat.com/ex/singularities.and.nightmares. Accessed November 15, 2007.Kurzweil, Raymond. The Singularity Is Near: When Humans TranscendBiology. New York: Viking, 2005.KurzweilAI.net. Available online. URL: http://www.kurzweilai.net. Accessed November 15, 2007.Lifeboat Foundation. Available online. URL: http://lifeboat.com.Accessed November 15, 2007.Singularity Institute for Artificial Intelligence. Available online.URL: http://www.singinst.org/. Accessed November 15, 2007.Vinge, Vernor. “The Coming Technological Singularity: Howto Survive in the Post-Human Era.” Available online. URL:http://www-rohan.sdsu.edu/faculty/vinge/misc/singularity.html. Accessed November 15, 2007.SmalltalkWorking during the 1970s at the Xerox Palo Alto ResearchLaboratory (PARC), computer scientist Alan Kay createdmany ideas and devices that have found their way intotoday’s personal computers. While designing a proposednotebook computer called the Dynabook, Kay decided totake a new approach to creating its operating system. Theresult would be a language (and system) called Smalltalk.In developing Smalltalk, Kay built upon two importantideas. The first was that people could master the powerof the computer most easily by being able to create, test,and revise programs interactively rather than having to gothrough the cumbersome process of traditional compilation.Seymour Papert had already created Logo, an interactive,graphics-rich language that proved especially goodfor teaching children surprisingly sophisticated computerscience concepts. The name Smalltalk reflects how the firstimplementation of this language was also designed to be asimple, child-friendly language.The other key idea Kay used in Smalltalk was object-orientedprogramming, which had first been developed in thelanguage Simula 67 (see Simula and object-oriented programming).However, instead of simply adding classes andobjects to existing language features, Kay designed Smalltalkto be object-oriented from the ground up. Even thedata types (such as integer and character) that are used todeclare variables in traditional languages become objects inSmalltalk. Users can define new classes that are treated justlike the “built-in” ones. There is no need to worry abouthaving to declare variables to be of a certain type beforethey can be used; in Smalltalk variables can be associatedwith any object.To get a program to perform an action, a “message” issent to an object, which invokes one of the object’s definedcapabilities (methods). For a very simple example, considerthe BASIC assignment statement:Total = Total + 1In a traditional language like BASIC, this is conceptualizedas “add 1 to the value stored at the location labeledTotal and store the result back in that location.” In theobject-oriented Smalltalk language, however, the equivalentstatement would be:Total

434 smart buildings and homesThis means “send the message + 1 to the object thatis referenced by the variable called Total.” This messagereferences the + method, one of the methods that numericobjects “understand.” The object therefore adds 1 to itsvalue, and returns that value as a new object, which in turnis now referenced by the variable Total.A “program” in Smalltalk is simply a collection of objectswith the capabilities to carry out whatever processes arerequired. The objects and their associated variables makeup the “workspace,” which can be saved to disk periodically.For the Smalltalk programmer there is no distinctionbetween Smalltalk and the host computer’s operatingsystem. The operating system’s capabilities (such asfile handling) are provided within the Smalltalk system aspredefined objects. Kay envisaged Smalltalk as a completeenvironment that could be extended by users who were notnecessarily experienced programmers, and he designed itspioneering graphical user interface as a way to make it easyfor users to work with the system.Smalltalk includes a “virtual machine,” whose instructionsare then implemented in specific code for each majortype of computer system. Because of Smalltalk’s consistentstructure and ability to build everything up from objects,almost all of the Smalltalk system is written in Smalltalkitself, making it easy to transplant to a new computer oncethe machine-specific details are provided.Because of its elegance and consistency and its availabilityon personal computers, by the 1980s Smalltalk hadaroused considerable interest. The language has not beenwidely used for mainstream applications, in part becausethe mechanisms needed to kept track of classes and inheritanceof methods are hard to implement as efficiently asthe simpler mechanisms used in traditional languages. Theapproach of building object-oriented features onto existinglanguages (as with developing C++ from C) had greaterappeal to many because of efficiency and a less steep learningcurve.Nevertheless, the conceptual power of Smalltalk hasmade it attractive for certain AI and complex simulationprojects, and it appeals to those who want a pure objectorientedapproach where an application can cleanly mirrora real-world situation. Smalltalk also remains a good choicefor teaching programming to children (and others). A versioncalled Squeak provides a rich environment of graphicsand other functions. Squeak and a number of other Smalltalkimplementations are available for free download for anumber of different computer systems.Further ReadingDucasse, Stéphane. Squeak: Learn Programming with Robots. Berkeley,Calif.: Apress, 2005.Klimas, Edward J., Suzanne Skublics, and David A. Thomas. Smalltalkwith Style. Englewood Cliffs, N.J.: Prentice Hall, 1996.Lewis, Simon. The Art and Science of Smalltalk. Englewood Cliffs,N.J.: Prentice Hall, 1995.Smalltalk. Available online. URL: http://smalltalk.org. AccessedAugust 21, 2007.Squeak. Available online. URL: http://www.squeak.org/. AccessedAugust 21, 2007.smart buildings and homesA smart building, whether commercial space or a home, isone in which components ranging from HVAC (heating,ventilation, and air conditioning) to appliances, computers,communications, security, and entertainment systems areintegrated into a network for easy control.Some typical features of a smart building include thefollowing:• lighting that is controlled by time of day, scheduling,and occupancy sensors• temperature and air-flow sensors to determine theamount of cooling, heating, or fresh air needed• controls for central heating, hot water, and air conditioningsystems, optimizing efficiency and minimizingenergy use• alarms for intrusion, fire, carbon monoxide/dioxide,and other hazards• alarms indicating failure or unsafe operating conditionsfor various devices• integration of alarm and status messages withcommunications systems, enabling users to receivethem by e-mail, text message, phone, or othermeansUsing a secure link, the user can connect to the buildingvia mobile phone or perhaps Internet connection andgive it commands, such as to turn the heating or porch lighton, close the drapes, and so on. The system can also let theremote user know who is at the door and allow for communication,or let them in.Smart office or other buildings use many of the sametechnologies as smart homes, but the priorities and emphasesmay be different. Smart buildings are more likely tobe centrally controlled and fully automated rather thanallowing individuals to interact with them. (Regulatory andsafety requirements are also likely to be different and morecomplex.)Applications and QuestionsThe integrated controls in a smart house are potentiallyvery useful for disabled persons or seniors who have limitedmobility. Lighting could automatically be turned onas a person gets up from bed and goes to the bathroom, forexample. Appliances could be controlled remotely, and evencupboards or tables could be designed to raise or lower atthe touch of a button. (See disabled persons and computingand seniors and computing.) If such systems areeffective, their cost may be well worth the psychologicalbenefits of allowing people to remain in their homes, and incomparison to the cost of assisted living or residence facilities.Smart homes could also help parents monitor toddlersor small children as well as restrict them from enteringpotentially hazardous parts of the house.Critics of the smart-house concept point out that installingand integrating all the required equipment for a full

smart card 435A smart house or building makes it easy to control essential functions such as heating, air conditioning, lighting, and security systems.implementation is quite expensive. Incorporating the necessaryfeatures when building a new house would be easier,since infrastructure such as cabling can be incorporatedin the building design. However, much of the technologyis not fully mature. There are several standards for interconnection,including the venerable X10, Z-Wave, andInsteon—and they are incompatible with one another.Further ReadingBriere, Danny, and Pat Hurley. Smart Homes for Dummies. 3rd ed.Hoboken, N.J.: Wiley, 2007.Eisenpeter, Robert C., and Anthony Volte. Build Your Own SmartHome. Emeryville, Calif.: McGraw-Hill/Osborne, 2003.“Home Automation for the Elderly and Disabled.” Wikipedia.Available online. URL: http://en.wikipedia.org/wiki/Home_automation_for_the_elderly_and_disabled. Accessed November15, 2007.Lee, Jeanne. “Smart Homes: The Best of Today’s Intelligent, NetworkedHome Appliances Aren’t Just Cool and High-Concept.Believe It or Not, They also Make Sense.” Money, Oct. 1,2002, p. 120 ff.Mitchell, Robert. “The Rise of Smart Buildings.” Computerworld,March 14, 2005. Available online. URL: http://www.computerworld.com/networkingtopics/networking/story/0,10801,100318,00.html. Accessed November 15, 2007.account. All the actual data (such as account balances) iskept in a central server, which is why credit cards mustbe validated and transactions approved through a phone(modem) link. Some magnetic strip cards such as thoseused in rapid transit systems are rewritable, so that, forexample, the fare for the current ride can be deducted. Telephonecards work the same way. Nevertheless, these cardsare essentially passive tokens containing a small amount ofdata. They have little flexibility.However, since the mid-1970s it has been possible toput a microprocessor and rewritable memory into a cardthe size of a standard credit card. These smart cards cansmart cardThe smart card is the next generation of transaction devices.Magnetically coded credit, debit, and ATM cards have beenin use for many years. These cards contain a magnetic stripencoded with a small amount of fixed data to identify theA smart card is “smart” because it does not just hold and updatedata, but has an embedded program and the ability to respond to avariety of requests.

436 smartphonestore a hundred or more times the data of a magnetic stripcard. Further, because they have an onboard computer (seeembedded system), they can interact with a computer atthe point of service, exchanging and updating information.Magnetic strip cards have no way to verify whetherthey’re being used by their legitimate owner, and it is relativelyeasy for criminals to obtain the equipment for creatingcounterfeits. With a smart card, the user’s PIN can bestored on the card and the terminal can require that the usertype in that number to authorize a transaction. Again, thePIN can be validated without reference to a remote server.Hardware and ProgrammingBesides the microprocessor and associated circuitry, thesmart card contains a small amount of RAM (randomaccess memory) to hold “scratch” data during processing,as well as up to 64 kB of ROM (read-only memory) containingthe card’s programming instructions. The program iscreated on a desktop computer and written to the ROMthat is embedded in the card. Finally, the card includes upto 64 kB of EEPROM (Electrically Erasable ProgrammableRead Only Memory) for holding account balances and otherdata. This memory is nonvolatile (meaning that no power isneeded to maintain it), and can be erased and rewritten bythe card reader.“Contact” cards must be swiped through the reader andare most commonly used in retail, phone, pay TV, or healthcare applications. “Contactless” cards need only be broughtinto the proximity of the reader, which communicates withit via radio signals or a low-powered laser beam. Contactlesscards are more practical for applications such as collectingbridge tolls (see also rfid).The card reader (or terminal) at the point of sale containsits own computer, which runs software that requestsparticular services from the card’s program, including providingidentifying information and balances, updating balances,and so on.Microsoft and some other companies have introducedthe PC/SC standard for programming smart cards fromWindows-based systems. Another standard, Open Card,promises to be compatible with a wide range of platformsand languages, including Java. (Java, after all, descendedfrom a project to develop a language for programmingembedded systems.) However, the first commercially availableJava-based smart card programming system is basedon another standard called JavaCard.ApplicationsThe same smart card might also be programmed to handleseveral different types of transactions, and could functionas a combination phone card, ATM card, credit card, andeven medical insurance card. Europe has been well ahead ofthe United States in adopting smart card technology, withboth France and Germany beginning during the 1980s touse smart cards for their phone systems. During the 1990s,they began to develop infrastructure for universal use ofsmart cards for their national health care systems. In 2002,Ontario, Canada, began to replace citizenship papers with asmart card, as well as creating a health services card. Otherinnovative uses for smart cards include London’s city passfor tourists, which can be programmed to provide not onlyprepaid access but also various bonuses and promotions.The packing of many services and the associated informationonto a smart card raises greater concern that theinformation might be illicitly captured and abused (see privacyin the digital age). Smart chips about the size ofa grain of rice can be implanted beneath the skin. Whenscanned by hospital personnel, the patient’s entire medicalrecord can be retrieved, which can be vital for decidingwhich drugs to administer in an emergency when the patientis unable to communicate. However, the chips might be surreptitiouslyscanned by, for example, employers seeking toscreen out workers with expensive medical conditions.Smart cards (such as for digital TV access) have beencounterfeited with the aid of sophisticated programs andintrusion equipment. Card makers try to design the card’scircuits so that it resists intrusion and tampering and rejectsprogramming attempts from unauthorized equipment.Another way to prevent unauthorized use is to havethe card store identifying information that can be verifiedthrough fingerprint scanners or other means (see biometrics).Smart ID and access cards are being deployed bymore U.S. government agencies to control access to sensitiveareas in the wake of the September 11, 2001, terroristattacks. The newest smart cards, such as one called theUltra Card, can hold 20 MB of information, allowing theuse of much more extensive biometric data. The controversial“national ID card,” if implemented, is likely to be asmart card.A service called GSM (Global System of Mobile Communications)is gradually being adopted. Through the useof a smart card “subscriber identity module,” it allows wirelessphone users in any participating country to make callsand have the appropriate fees deducted. Further, the GSMcan route calls to a person’s number automatically to thatperson’s handset, regardless of the country of origin anddestination.There is a very large investment in the current creditcard technology, but the flexibility and potential security ofsmart credit and debit cards is attractive. Already some issuershave released credit cards with smart chip technology.Further ReadingJurgensen, Timothy M., and Scott B. Guthery. Smart Cards: TheDeveloper’s Toolkit. Upper Saddle River, N.J.: Prentice Hall,2002.Paret, Dominique. RFID and Contactless Smart Card Applications.New York: Wiley, 2005.Rankl, Wolfgang, and Wolfgang Effing. Smart Card Handbook. 3rded. New York: Wiley, 2004.Smart Card Basics. Available online. URL: http://www.smartcardbasics.com/. Accessed August 21, 2007.smartphoneIn biology, convergent evolution is when two very differenttypes of creatures evolve similar structures or traits to copewith similar environments—for example, wings in insects,

smartphone 437birds, and bats. Something like this has happened with handheldmobile devices that are used to manage personal informationand for communication. Personal digital assistants(see PDA) can maintain lists of phone numbers and othercontact information, as well as running a variety of useful orentertaining applications. However, the first models had noprovision for actually making phone calls, while later modelsoffered the ability to make calls through a wireless connection(see Bluetooth) to an appropriately equipped mobilephone. This meant, though, that the user had to carry twoseparate devices, the PDA and the phone, somewhat defeatingthe objectives of portability and convenience.Meanwhile, of course, mobile phones were a boomingindustry—and a very competitive one, hence the pressureto add new features. Some of these features overlap typicalPDA features, such as storing contact lists, appointments,and other personal information. Further, users want to beable to not only send text messages, but read and send e-mail, and browse the Web. But providing all these applicationsreally calls for a full-fledged (albeit compact) operatingsystem and facilities for creating user interfaces. The resultis the smartphone, which in effect is a phone that is growninto a PDA while maintaining its phone capabilities. Thusthe smartphone aims to be the way to meet all communications,information management, Web, and entertainmentneeds in a single device. Typical features also include acamera and an audio-video media player (see music andvideo players, digital) and a small but increasingly sharpscreen.Some of the major smartphone manufacturers and theiroperating systems include the following:• Symbian (Symbian OS), used by Nokia, Motorola,Samsung, and others• Windows Mobile (enhanced Windows CE), popularin phones used in Asia• Blackberry (RIM), the popular PDA/smartphone• Linux, used as the base on which to build a varietyof PDA/phone operating systems, including productsfrom Motorola, Palm, and Nokia (Maemo)• OS X (Apple), used in Apple’s innovative and verypopular iPhoneConvergenceAs a practical matter, the PDA and smartphone categoriesnow overlap so much that a device such as the Apple iPhonecan be called either, and then some. Although Apple initiallylocked out full access to the iPhone operating systemfor developing third-party applications (and locked thephone itself to only a few providers), the overall trend in theindustry is to provide more flexibility and accessibility.Although not yet accompanied by an actual device, the2007 announcement by Google of an open-source phonesoftware platform called Android has been greeted by considerableinterest. The product will be developed furtherby the Open Handset Alliance, a consortium of Google andmore than 30 other companies, including T-Mobile andSmartphone or PDA? Sometimes it is just a matter of semanticswhat to call a handheld device such as this Palm Treo 700w thatcan make phone calls and send e-mail or text messages as well asmanage information. (Palm, Inc.)Motorola. The use of open-source software should reducecosts to developers and consumers, in part by making itpossible for a developer to create an application that canrun on dozens of different smartphone models.Further ReadingAmes, Patrick, and David Maloney. Now You Know: Treo 700wSmartphone. Berkeley, Calif.: Peachpit Press, 2007.Best, Jo. “Analysis: What Is a Smart Phone?” Silicon.com, February13, 2006. Available online. URL: http://networks.silicon.com/mobile/0,39024665,39156391,00.htm. Accessed November16, 2007.Jipping, Michael J. Smartphone Operating System Concepts withSymbian OS. Hoboken, N.J.: Wiley, 2007.McPherson, Frank. How to Do Everything with Windows Mobile.New York: McGraw-Hill, 2006.Open Handset Alliance. Available online. URL: http://www.openhandsetalliance.com/. Accessed November 16, 2007.

438 SOAPPogue, David. iPhone: The Missing Manual. Sebastapol, Calif.:O’Reilly, 2007.Smartphone & Pocket PC [magazine Web site]. Available online.URL: http://www.pocketpcmag.com/defaults.asp. AccessedNovember 16, 2007.SOAPOriginally standing for Simple Object Access Protocol, butnow no longer an acronym, SOAP is a standard way toaccess Web services (see service-oriented architectureand Web services). In today’s Web, where what appears tousers to be a single site or application is usually built frommany services, such a facility is essential.Prior to SOAP, Web applications usually communicatedthrough remote procedure calls (RPC). However there wereproblems with compatibility of applications running underdifferent operating systems (and perhaps using differentprogramming languages), as well as security problems thatoften led to such facilities being blocked.SOAP, on the other hand, uses the same HTTP recognizedby all Web servers and browsers (see Web browser,Web server, and World Wide Web)—indeed, it can alsouse secure HTTP (https).A SOAP request (or message) is an ordinary XML file(see xml) that includes an “envelope” element specifyingit to be a SOAP message, an optional header, a body elementcontaining the information pertaining to the functionor transaction requested, and an optional fault elementto specify error processing. After receiving the message,the destination server returns a message providing therequested information.A very simple SOAP message might look like this:311The message asks for the price for item number 311.Despite its advantages in terms of security, versatility,and readability, SOAP does have some disadvantages.The main one is that XML files can be quite lengthy, makingtransactions slower than with the much more compactCORBA (see CORBA).Further ReadingBurd, Barry. Java & XML for Dummies. Indianapolis: Wiley, 2002.Freeman, Adam, and Allen Jones. Microsoft .NET XML Web ServicesStep by Step. Redmond, Wash.: Microsoft Press, 2003.“SOAP Tutorial.” W3schools.com. Available online. URL: http://www.w3schools.com/soap. Accessed November 17, 2007.“What Is SOAP” [Flash presentation]. Available online. URL:http://searchwebservices.techtarget.com/searchWebServices/downloads/what_is_soap.swf. Accessed November 17, 2007.Zimmermann, Olaf, Mark Tomlinson, and Stefan Peuser. Perspectiveson Web Services: Applying SOAP, WSDL, and UDDI toReal-World Projects. New York: Springer, 2003.social impact of computingIn 2001, the Computer Professionals for Social Responsibility(CPSR) held a conference titled “Nurturing theCybercommons, 1981–2021.” Speakers looked back at theamazing explosion in computing and computer-mediatedcommunications in the last two decades of the 20th century.They then turned to the next 20 years, discussinghow computing technology offered both the potential fora more robust democracy and the threat that control ofinformation by the few could disenfranchise the many.Their challenge was to create a “cybercommons”—a wayin which the benefits of technology could be shared moreequitably.It is sobering to realize just how much happened in onlytwo decades. The computer went from being an esotericpossession of large institutions to a ubiquitous companionof daily work and home life. At the same time, the Internet,which in 1981 had been a tool for a small number ofcampus computing departments and government-fundedresearchers, has burgeoned to a medium that is fast changingthe way people buy, learn, and socialize.The use of computing for specific applications generallybrings risks along with benefits (see risks of computing).Sometimes risks can go beyond a specific program into theinteraction between that program and other systems. In thebroadest sense, however, computer use as a human activityaffects all other human activities. The ultimate infrastructureis not the computer, the software program, or even theentire Internet. Rather, it is society as a whole. There are aseveral dimensions along which both positive and negativepossibilities can be seen.One of the earliest hints that computers might have a broaderimpact on society came in 1952, when Univac’s prediction ofan Eisenhower election victory was relayed by anchor WalterKronkite. (Al Fenn / Time Life Pictures/Getty Images)

social impact of computing 439Stratification v. OpportunityIn the past 30 years, the computer has created millions ofnew jobs, ranging from webmaster to support technicianto Internet café proprietor (see employment in the computerfield). Millions of other jobs have been redefined:The typist has become the word processor, for example.Many other jobs have disappeared or are in the processof disappearing—such as travel agents, who have foundthemselves under pressure both from do-it-yourself Internetbooking and the airlines deciding that they no longerneeded to give agents incentives for booking.In a rapidly changing technological and economic landscape,there are always emerging opportunities. The primacyof computer skills in the job market has, however,exacerbated a trend that was seen throughout the 20thcentury. New, well-paid jobs increasingly require technicaltraining and skills—expanding the definition of “functionalliteracy.” Throughout the second half of the century,the traditional blue-collar factory jobs that could assure acomfortable living for persons with only a high school educationhave become increasingly scarce. This has been theresult both of increasingly competitive (and lower-priced)overseas labor and factory automation (see robotics) athome. Essentially, the well-paid tech sector and the lowpaidservice sector have grown rapidly, while the ground inbetween has eroded.Sometimes jobs don’t disappear, but are “dumbed down,”becoming low-skill and low-paid. Fifty years ago, a storeclerk had to be able to count up from the cash register totalto the amount of money presented by the customer. Today,computerized cash registers tell the clerk exactly how muchchange to give (and often dispense the coins automatically).Old-style clerks had to know about prices, discounts, andspecial offers. Today these are handled automatically bybar codes and smart cards. Although the supermarket clerkstill is moderately well paid, the ultimate end of the processis seen in the fast food clerk, who often needs only pushbuttons with pictures of food on them. He or she is likelyto be paid little more than minimum wage. The impact oftechnology on jobs can even go through several stages. Forexample, skilled photo technicians have been replaced bythe use of automated photo processing equipment. In turn,however, the growing use of digital cameras is reducing theuse of film-based photography in general.The result of these trends may well be increased socialstratification. The best jobs in the information age requireskills such as programming, systems analysis, or the abilityto create multimedia content. However, the opportunityto acquire such skills varies and is not evenly distributedthrough all groups in the population (see digital divide).Although minority groups are now catching up in terms ofaccess to computers at home and in school, disparities inthe quality of education will only be magnified as technicalskills increasingly correlate with good pay and benefits.At the same time the computer offers powerful newtools for education (see education and computers).Potentially, this could overcome much of the disadvantagesof poverty because once the threshold of access is met, thepoor person’s Internet is much the same as that availableto the privileged. However, mastering the necessary skillsrequires both provision of adequate resources and that prevailingcultural attitudes support intellectual achievement.Dependency v. EmpowermentComputers have made people more dependent in someways while empowering them in others. Society is increasinglydependent on computers to operate the systems thatprovide transportation, power, and communications infrastructure.The “y2k” scare at the end of the century provedto be unfounded, but it did give people a chance to considerwhat a major, prolonged failure in the information infrastructurewould mean for maintaining the physical necessitiesof life, the viability of the economy, and the cohesionof society itself (see Y2K problem). The terrorist attacks ofSeptember 11, 2001, brought to greater public awarenessthe concerns about “cyberterrorism” that experts had beendebating since the late 1990s. (See cyberterrorism.)At the same time, computers—and particularly theInternet—have give individuals a greater feeling of empowermentin many respects. The savvy Web user now hasnumerous ways to shop for everything from airline ticketsto Viagra pills at prices that reflect disintermediation—the elimination of the middleman. Many people are lessinclined to take the word of traditional authority figures(such as doctors) and instead are tapping into the sort ofinformation that had been previously been accessible onlyto professionals. However, access to information is not thesame thing as having the necessary background and skillsto evaluate that information. Whether falling victim to anoutright scam or simply not fully understanding the consequencesof a decision, the Web user finds little in the wayof a regulatory safety net. The tension between the highdegree of regulation now existing in much of our societyand the frontierlike qualities of cyberspace will no doubt bea major theme in the next few decades.Centralization v. DemocracyWith new forms of media technology (such as radio andtelevision in the 20th century), early innovators and experimentershave considerable freedom to experiment andexpress themselves. This freedom is largely the result oflack of pressure from powerful economic interests whilethe new technology is largely still “under the radar.” However,as a technology matures, large corporate interests tendto consolidate the market, leaving fewer opportunities forsmaller, independent operators.By the late 1990s there was some concern that theInternet and World Wide Web were entering such a consolidationstage in the wake of such developments as theAOL/Time-Warner merger. However, while there are nowlarge corporate presences online, the diversity of the meansof expression has actually increased (see blogs and blogging,user-created content, wikis and Wikipedia, andYouTube). Further, the influence of activist groups hasincreased to the point where any serious political campaigngives high priority to its Internet presence and the cultivationof influential bloggers (see political activism andthe Internet).

440 social networkingThere continue to be centralizing or antidemocraticpressures in the online world (for example, see censorshipand the Internet). There is also the conflict between thedesire to protect intellectual property and the free sharingof images and other media (see distribution of music andvideo, online and intellectual property and computing).Loss of privacy can also inhibit untrammeled politicaldiscourse (see privacy in the digital age). At the sametime, organizations such as the Electronic Frontier Foundation,Electronic Privacy Information Center, and Center forDemocracy and Technology work to protect and advocatedemocratic expression.Isolation v. CommunityThere are many online facilities that allow individuals andgroups to maintain an ongoing dialog (see chat, onlineand conferencing systems). Students at a school in Iowacan now collaborate with their counterparts in Kenya orThailand on projects such as measuring global environmentalconditions. Senior citizens who have become isolatedfrom family members and lack access to transportation canfind social outlets online.However, critics such as Clifford Stoll believe that thegrowth of online communication (see also virtual community)may be leading to a further erosion of physicalcommunities and a sense of neighborhood. For many years,it has been observed that people in suburbia often don’tknow their neighbors: The car and the phone let them formrelationships and “communities” without much regard togeography. It is possible that the growth in online communitieswill accelerate this effect. Further, with people beingable to order an increasing array of goods and servicesonline, might the market plaza and its modern counterpartthe mega mall become less of a meeting place? Eventhe proposal to allow people to vote online might promotedemocracy at the expense of the contact between citizensand the shared rituals that give people a stake in the largercommunity.Thus, computer technology offers many opposing prospectsand visions. The social changes that are cascadingfrom information and communications technology arelikely to be at least as pervasive in the early 21st century asthe those wrought by the telephone, automobile, and televisionwere in the 20th.Further ReadingAssociation for Computing Machinery. Special Interest Group onComputers and Society. Available online. URL: http://www.sigcas.org/. Accessed August 21, 2007.Center for Democracy & Technology. Available online. URL:http://www.cdt.org/. Accessed August 21, 2007.Computer Professionals for Social Responsibility. Available online.URL: http://www.cpsr.org. Accessed August 21, 2007.De Paula, Paul. Annual Editions: Computers in Society 06/07. Guilford,Conn.: McGraw-Hill/Duskin, 2006.Electronic Frontier Foundation. Available online. URL: http://www.eff.org. Accessed August 21, 2007.Kizza, Joseph Migga. Ethical and Social Issues in the InformationAge. 2nd ed. New York: Springer, 2002.Morley, Deborah, and Charles S. Parker. Computers and Technology ina Changing Society. 2nd ed. Boston: Course Technology, 2004.Pew Internet & American Life Project. Available online. URL:http://www.pewinternet.org/. Accessed August 21, 2007.social networkingToday, millions of people—middle, high school, and collegestudents, but increasingly adults as well—have pages onpopular Web sites such as MySpace and Facebook. Thesesites are significant examples of social networking: the useof Web sites and communications and collaboration technologyto help people find, form, and maintain social relationships.The origins of social networking can be traced to onlinevenues that arose in the 1970s and 1980s, notably Usenetand, later, online chat boards (see bulletin board system,conferencing system, netnews, and virtual community).In the late 1990s social networking Web sites beganto appear, including Classmates.com (helping people findand communicate with former schoolmates) and SixDegrees.com,which emphasized “knows someone who knowssomeone who . . .” kinds of links.By the mid-2000s the two biggest sites were Facebookand MySpace. Founded in 2006 by Mark Zuckerberg, Facebookwas originally restricted to Harvard students, buteventually became open to any college student, and thenhigh schools and even places of employment. (The namecomes from a book given to incoming students in someschools to familiarize them with their peers.) As of late2007 Facebook had more than 55 million active membersand had become the seventh most visited of all Web sites.Facebook users have profile pages that include a “wall”on which their designated circle of friends can post briefmessages. (Longer or private messages similar to e-mail canalso be sent.) Users can also send each other “gifts” representedby colorful icons. Finally, users in a given Facebookcommunity can keep track of each other’s status (wherethey are and what they are doing).Beverly Hills, California-based, MySpace is an evenlarger site, near the top of the Web site popularity statisticsthrough much of 2007. Founded in 2003, the site was createdand marketed by a company called eUniverse (laterIntermix), and its launch was greatly boosted by being ableto tap many of eUniverse’s 20 million existing subscribers.User profiles are broadly similar to those in Facebook, butare less structured and more colorful, with uploaded graphicsand a blog for each user. Profiles can be elaboratelycustomized using a variety of tools and utilities. The sitehas also expanded into other areas such as instant messaging(MySpaceIM), video sharing (MySpactTV), and mobilephones (MySpace Mobile).Social network applications are also expanding behindthe linking of classmates or colleagues. Companies can usesocial networking software to set up user groups and providesupport and incentives. Medical professionals are oftenforming social networks to share knowledge and news—and not surprisingly, drug company representatives havemoved in to make their pitch as well. Business executivesand professionals can meet on LinkedIn, a site that linkspeople only if they have an existing relationship or an “invi-

social sciences and computing 441tation” from an existing member. As further proof that thetechnology is maturing, about 20 percent of adult Internetusers have reported visiting a social networking site in thepast 30 days.CommercializationIndeed, because they are now bringing so many peopletogether, social networking sites have become a very attractiveplatform for online products and businesses. Facebook,for example, is explicitly allowing selected businesses touse the site, in exchange for a portion of the revenue generated.(Even without formal relationships, many sites allowusers to add code enabling third-party services.) Some utilities(often sponsored by advertising) help users make theirprofiles more attractive, while one called MySpacelog servesusers who are anxious to see who is viewing their sites.Looming on the horizon by 2007 was Google, which isreleasing OpenSocial, a set of programming interfaces thatis expected to enable developers to create applications thatwill run on a wide variety of social networking sites.While social networking sites generally want to encourageproducts that can add revenue (and value to users), someadd-on applications can be problematic. In 2006 a site calledStalkerati let users automatically search for a person’s profileson popular social networking sites and consolidate them intoa summary. However, the perhaps unfortunately named sitedwas soon blocked by MySpace and other sites, which citedprivacy and security concerns. These concerns have becomeincreasingly important as networks such as MySpace haveproven attractive to spammers, identity thieves, and sexualpredators. (A 2007 survey by the Pew Internet & AmericanLife Project found that 23 percent of teens on social networkshad felt “scared or uncomfortable” because of an onlineencounter with a stranger. However, that same report showedthat many parents and teens themselves have become awareof potential risks and the need to more carefully managewhere and how information is disclosed.)Social networking is also attracting the attention ofsocial scientists and academics: For example, the Universityof Michigan now has a graduate program in social computing.Meanwhile sociologist Michael Macy of Cornell Universityis directing a multiyear research project, funded bythe National Science Foundation and Microsoft, titled “GettingConnected: Social Science in the Age of Networks.”Note: the term social network is also used to refer to amethod of mathematical and sociological analysis of sociallinks within organizations. Such methods can of course beapplied to the online social networking sites.Further ReadingBaloun, Karel M. Inside FaceBook: Life, Works, and Visions of Greatness.Victoria, B.C., Canada: Trafford, 2007.Facebook. Available online. URL: http://www.facebook.com/.Accessed November 18, 2007.Hupfer, Ryan, Mitch Maxson, and Ryan Williams. MySpace forDummies. Hoboken, N.J.: Wiley, 2007.Lavallee, Andrew. “At Some Schools, Facebook Evolves from TimeWaster to Academic Study.” Wall Street Journal Online, May29, 2007. Available online. URL: http://online.wsj.com/article/SB117917799574302391.html. Accessed November 18, 2007.Lenhart, Amanda, and Mary Madden. “Social Networking Websitesand Teens: An Overview.” Pew Internet & American LifeProject, January 7, 2007. Available online. URL: ttp://www.pewinternet.org/pdfs/PIP_SNS_Data_Memo_Jan_2007.pdf.Accessed November 18, 2007.———. “Teens, Privacy & Online Social Networks: How TeensManage Their Online Identities and Personal Informationin the Age of MySpace.” Pew Internet & American LifeProject, April 18, 2007. Available online. URL: http://www.pewinternet.org/pdfs/PIP_Teens_Privacy_SNS_Report_Final.pdf. Accessed November 18, 2007.MySpace. Available online. URL: http://www.myspace.com/.Accessed November 18, 2007.Shepherd, Lauren. “Social Networking Breeds Creation of Third-Party Sites.” Associated Press/San Francisco Chronicle, June18, 2007, p. C5.Weber, Larry. Marketing to the Social Web: How Digital CustomerCommunities Build Your Business. Hoboken, N.J.: Wiley, 2007.social sciences and computingBroadly speaking, social scientists study the structure anddynamics of human societies as well as groups of all kinds.Depending on subject matter, the research can fall withinone or more disciplines, for example, anthropology, psychology,economics, geography, history, political science,or sociology. As with other scientific fields, computers havegreatly enhanced and expanded the ability to carry out,analyze, and communicate research findings.ApplicationsSocial scientists can use a variety of software throughoutthe research process. For example, researchers might usethe following:• Web and bibliographical search tools to find existingresearch on their topic• note-taking and concept-diagramming (“mind-mapping”)software• software to conduct polls or surveys and compile theresults• social networking analysis to better understand agroup’s structure and dynamics• statistical analysis tools to analyze the findings (seestatistics and computing)• map-based systems for studying geographical aspects(see geographical information systems)• modeling software to simulate the mechanism beingstudied, using mathematical techniques such as theMonte Carlo and Markov-Chain methodsGames and virtual worlds in particular are being usedin innovative ways. Games such as the classic SimCity orthe “social simulator” The Sims can be used to help studentsunderstand and experiment with economic and socialdynamics. However, virtual worlds can also be studied intheir own right—for example Tufts University researchersNina Fefferman and Eric Lofgren have written a paperdescribing how the spread of a “virtual plague” in Second

442 software agentLife could be studied to learn how people would be mostlikely to react to a real disease outbreak. And at CarnegieMellon University, a National Science Foundation–fundedproject will be studying interactions in online venues asdisparate as World of Warcraft and Wikipedia.Further ReadingDochartaigh, Niall O. The Internet Research Handbook: A PracticalGuide for Students and Researchers in the Social Sciences.Thousand Oaks, Calif.: Sage Publications, 2002.Gilbert, Nigel, and Klaus G. Troitzsch. Simulation for the SocialScientist. Philadelphia: Open University Press, 1999.“The Impoverished Social Scientist’s Guide to Free Statistical Softwareand Resources.” Available online. URL: http://www.hmdc.harvard.edu/micah_altman/socsci.shtml. AccessedOctober 5, 2007.Patterson, David A. “Using Spreadsheets for Data Collection, StatisticalAnalysis, and Graphical Representation.” Availableonline. URL: http://web.utk.edu/~dap/Random/Order/Start.htm. Accessed October 5, 2007.Saam, Nicole J., and Bernd Schmidt. Cooperative Agents: Applicationsin the Social Science. Norwell, Mass.: Kluwer AcademicPublishers, 2001.Summary of Survey Analysis Software (Harvard). Available online.URL: http://www.hcp.med.harvard.edu/statistics/survey-soft/.Accessed October 5, 2007.software agentMost software is operated by users giving it commandsto perform specific, short-duration tasks. For example, auser might have a word processor change a word’s typestyleto bold, or reformat a page with narrower margins.On the other hand, a person might give a human assistanthigher-level instructions for an ongoing activity: for example,“Start a clippings file on the new global trade treaty andhow it affects our industry.”In recent years, however, computer scientists and developershave created software that can follow instructionsmore like those given to the human assistant than thosegiven to the word processor. These programs are variouslycalled software agents, intelligent agents, or bots (shortfor “robots”). Some consumers have already used softwareagents to comb the Web for them, looking, for example,for the best online price for a certain model of digital camera.Agent programs can also assist with online auctions,travel planning and booking, and filtering e-mail to removeunwanted “spam” or to direct inquiries to appropriate salesor technical support personnel. (See also Maes, Pattie.)Practical agents or bots can be quite effective, but theyare relatively inflexible and able to cope only with narrowlydefined tasks. A travel planning agent may be able to interfacewith online reservations systems and book airline tickets,for example. However, the agent is unlikely to be able torecognize that a recent upsurge in civil strife suggests thattravel to that particular country is not advisable.Researchers have, however, been working on a varietyof more open-ended agents that, while not demonstrably“intelligent,” do appear to behave intelligently. The first programthat was able to create a humanlike conversation wasELIZA. Written in the mid-1960s by Joseph Weizenbaum,ELIZA simulated a conversation with a “nondirective” psychotherapist.More recently, Internet “chatterbots” such asone called Julia have been able to carry on apparently intelligentconversations in IRC (Internet Relay Chat) rooms,complete with flirting. Other “social bots” have served asplayers in online games (see chatterbots).Chatterbots are effective because they can mirror humansocial conventions and because much of casual humanconversation contains stereotyped phrases or clichés thatcan be easily imitated. Ideally, however, one would wantbots to be able to combine the ability to carry out practicaltasks with a more general intelligence and a more “sociable”interface. This requires that the bot have an extensiveknowledge base (see knowledge representation) and agreater ability to understand human language (see linguisticsand computing). Small strides have been made inproviding online help systems that can deal with naturallanguage questions, as well as being able to interactivelyhelp users step through a particular tasks.Agents or bots have also suggested a new paradigm fororganizing programs. Currently, the most widely acceptedparadigm treats a program as a collection of objects withdefined capabilities that respond to “messages” asking forservices (see object-oriented programming). A move to“agent-oriented programming” would carry this evolution astep further. Such a program would not simply have objectsthat wait passively for requests. Rather, it would have multipleagents that are given ongoing tasks, priorities, or goals.One approach is to allow the agents to negotiate with oneanother or to put tasks “up for bid,” letting agents thathave the appropriate ability contract to perform the task.With each task having a certain amount of “money” (ultimatelyrepresenting resources) available, the negotiationmodel would ideally result in the most efficient utilizationof resources.If Marvin Minsky’s (see Minsky, Marvin) “society ofmind” theory is correct and the human brain actually containsmany cooperating “agents,” then it is possible thatsystems of competing and/or cooperating agents mighteventually allow for the emergence of a true artificial intelligence.In the future, agents are likely to become more capableof understanding and carrying out high-level requestswhile enjoying a great deal of autonomy. Some possibleapplication areas include data mining, marketing and surveyresearch, intelligent Web searching, security, and intelligencegathering. However, autonomy may cause problemsif agents get out of control or exhibit viruslike behavior.Further ReadingDenison, D. C. “Guess Who’s Smarter.” Boston Globe, May 26,2003, p. D1. Available online. URL: http://web.media.mit.edu/~lieber/Press/Globe-Common-Sense.html. Accessed August21, 2007.D’Inverno, Mark, and Michael Luck. Understanding Agent Systems.2nd ed. New York: Springer, 2004.Lieberman, H., et al. “Commonsense on the Go: Giving MobileApplications an Understanding of Everyday Life.” Availableonline. URL: http://agents.media.mit.edu/projects/mobile/BT-Commonsense_on_the_Go.pdf. Accessed August 21, 2007.

software engineering 443Padgham, Lin, and Michael Winikoff. Developing Intelligent AgentSystems: A Practical Guide. New York: Wiley, 2004.Software Agents Group (MIT Media Lab). Available online. URL:http://agents.media.mit.edu/. Accessed August 21, 2007.software engineeringBy the late 1960s, large computer programs (such as theoperating systems for mainframe computers) consistedof thousands of lines of computer code. In what becameknown as “the software crisis,” managers of software developmentwere facing great uncertainty about both programdevelopment schedules and the reliability of the resultingprograms.Programming had started out in the 1940s as an offshootof mathematics, just as the building of computers wasan offshoot of electrical or electronic engineering. Increasingly,however, programmers were searching for a new professionalidentity. What paradigm was truly appropriate?Should programmers strive to be more like mathematicians,seeking to rigorously prove the correctness of their programs?On the other hand, many programmers thought oftheir work as a craft, performed using individual experienceand intuition, and not easily subject to standardization.Between the two poles of mathematics (or science) andcraft came another possibility: engineering.The concept of software engineering proved to be attractive.Mathematics (and science in general) are usually carriedon without being immediately and directly applied tocreating a particular device or process. Outside of researchprograms, however, computer applications were written toperform real-world tasks (such as flight control) that havereal-world consequences. Thus, although the notation ofa computer program resembles that of mathematics, theoperation of a program more nearly resembles that of complexmechanical systems created by engineers. By attachingthe label of engineering to what programmers do, advocatesof software engineering hoped to develop a body ofpractices and standards comparable in some way to thoseused in engineering. Some critics, however, believe thatthis paradigm is inappropriate, either because they believeone should strive for the greater rigor of science or out of apreference for individual craft over standardization.Programming PracticesOne of the most pervasive contributions to software engineeringhas been in computer language design and codingpractices. At about the same time that the concept of softwareengineering was being promulgated, computer scientistswere advocating better facilities for defining and structuringprograms (see structured programming). These includedwell-defined control structures (see branching statementsand loop), use of built-in and user-defined kinds of data (seedata types), and the breaking of programs into more manageablemodules (see procedures and functions).The next paradigm came in the late 1970s and hadtaken hold by the late 1980s (see object-oriented programming).The ability to “hide” details of function withinobjects that mirrored those in the real world provided a furtherway to make complex programs easier to understandand maintain. The growing use of well-tested collectionsof procedures or objects (see library, program) has beenessential for keeping up with the growing complexity ofapplication programs.Software engineers are also concerned with developingtools that will better manage the programming process andhelp ensure that standards are being followed (see programmingenvironment). The use of CASE (Computer-Aided Software Engineering) tools such as sophisticatedprogram editors, documentation generators, class diagrammers,and version control systems has also steadilyincreased. Today many of these tools are available even onmodest desktop computing environments (see case).The Program Development ProcessPerhaps the most important task for software engineeringhas been seeking to define and improve the process bywhich programs are developed. In general, the overall stepsin developing a program are:The Waterfall, or Cascade, model sees software development as a more linear process going through the requirements, design, implementation,integration and testing, and maintenance phases. The results of each phase cascade down into the next.

444 software piracy and counterfeiting• Detailed specification of what the program will berequired to do. This can include developing a prototypeand getting user’s reaction to it.• Creation of a suitable program architecture—algorithm(s) and the data types, objects, or other structuresneeded to implement them (see algorithm).• Coding—writing the program language statementsthat implement the structure.• Verification and testing of the program using realisticdata and field testing (see quality assurance,software).• Maintenance, or the correction of errors and addingof requested minor features (short of creating a newversion of the program).There are a number of competing ways in which to viewthis software development cycle. The “iterative” or “evolutionary”approach sees software development as a linearprocess of progress through the above steps.The “spiral” approach, on the other hand, sees the stepsof planning, risk analysis, development, and evaluationbeing applied repeatedly, until the risk analysis and evaluationphases result in a go/no go to finish the project.The most commonly used approach is called waterfall.In it the results (output) of each stage become the inputof the next stage. This approach is easiest for scheduling(see project management software), since each stage isstrictly dependent on its predecessor. However, some advocatesof this approach have included the ability for a givenstage to feed back to the preceding stage if necessary. Forexample, a problem found in implementation (coding) mayrequire revisiting the preceding design phase.Developing Software Engineering StandardsTwo organizations have become prominent in the effort topromote software engineering. The federally funded SoftwareEngineering Institute (SEI) at Carnegie Mellon Universitywas established in 1984. Its mission statement is to:1. Accelerate the introduction and widespread useof high-payoff software engineering practices andtechnology by identifying, evaluating, and maturingpromising or underused technology and practices.2. maintain a long-term competency in software engineeringand technology transition.3. Enable industry and government organizations tomake measured improvements in their software engineeringpractices by working with them directly.4. Foster the adoption and sustained use of standardsof excellence for software engineering practice.Since 1993, the IEEE Computer Society and ACM SteeringCommittee for the Establishment of Software Engineeringas a Profession has been pursuing a set of goals that arelargely complementary to those of the SEI:1. Adopt Standard Definitions2. Define Required Body of Knowledge and RecommendedPractices (In electrical engineering, forThe Spiral Model visualizes software development as a process ofplanning, risk analysis, development, and evaluation. The cyclerepeats until the project is developed to its full scope.example, electromagnetic theory is part of the bodyof knowledge while the National Electrical SafetyCode is a recommended practice.)3. Define Ethical Standards4. Define Educational Curricula for (a) undergraduate,(b) graduate (MS), and (c) continuing education(for retraining and migration).Further ReadingBooch, Grady. “The Promise, the Limits, the Beauty of Software.”March 8, 2007. Lecture before the British Computer Society.Available online. URL: http://www.bcs.org/server.php?show=ConWebDoc.10367. Accessed August 21, 2007.Brooks, Frederick. The Mythical Man-Month: Essays on SoftwareEngineering. 20th anniversary ed. Reading, Mass.: Addison-Wesley, 1995.Christensen, Mark J., and Richard H. Thayer. The Project Manager’sGuide to Software Engineering’s Best Practices. Los Alamitos,Calif.: IEEE Computer Society Press, 2001.McConnell, Steve. After the Gold Rush: Creating a True Professionof Software Engineering. Redmond, Wash.: Microsoft Press,1999.Software Engineering Coordinating Committee (IEEE ComputerSociety and Association for Computing Machinery.) Availableonline. URL: http://www.acm.org/serving/se/homepage.html.Accessed August 21, 2007.Sommerville, Ian. Software Engineering. 8th ed. Boston: Addison-Wesley, 2006.software piracy and counterfeitingAccording to surveys by analysis firm IDC, software piracyaccounted for $7.3 billion in losses to the U.S. softwareindustry in 2006, while reducing its expansion and thus jobcreation. (This is part of a larger picture in which, accordingto a Gallup study, 22 percent of adults in the United Statesreported having bought some sort of counterfeit product.) Abit of Web searching (or even reading spam in one’s in-box)suggests that thousands of sites offer “cracked” software

Sony 445that has been stripped of copy protection. The BusinessSoftware Alliance estimates that 35 percent of new softwareinstalled on PCs in 2006 was obtained illegally.Although piracy can involve many forms of distributionincluding Web sites, file-sharing services (see file-sharingand P2P networks), and even software found on “bargain”PCs, the most visible form involves physical packages completewith box, CDs, and even holograms. These counterfeits,which range from crude to nearly indistinguishable,are often produced in full-scale factories. China has beena major source for many types of product counterfeiting,although the government has periodically cracked downon the practice. Counterfeiting has also flourished in suchunlikely locales as Bangladesh and Serbia.Industry groups also assert that the misuse of legitimatelypurchased software (such as running more copiesthan have been licensed) is also a form of piracy. The potentiallegal liability is enormous, so companies make rigorouspolicies involving software use and install monitoring systemsto detect or prevent licensing violations. (For theirpart, industry groups have offered large cash rewards toemployees who reveal their company’s violations.)CountermeasuresAs perhaps the largest potential victim, Microsoft has beendiligent in fighting software piracy. Recent versions of Windows,Office, and other products require that users “validate”the software, associating the license number withdetails of the system’s hardware configuration. When theuser wants to download later updates or patches, the softwarevalidation is checked. Failure of validation leads towarning messages and disabling of many features of thesoftware.Microsoft has also been active in suing alleged pirates,and educating consumers about the dangers of buyingpirated software, which include the risk of exposure toviruses, spyware, and other harmful programs. An industryantipiracy group, the Business Software Alliance, has vigorouslyinvestigated corporate software use (often with theaid of tipsters), finding violations and making companiespay fines and buy licenses in lieu of legal action.Meanwhile, growing pressure from the software industryhas led in turn to U.S. pressure on China and othercountries to go after software counterfeiting operations. Insummer 2007, a joint operation by the FBI and Chineseofficials led to the seizure of more than $500 million incounterfeit software.Critics of antipiracy efforts, such as the Electronic FrontierFoundation, argue that estimates of losses from piracyassume that every pirated copy of a program represents alost sale, ignoring the possibility that people (such as students)would not have the money to buy legitimate copies.They also point to what they consider to be heavy-handedenforcement of copyright laws and point to proposed legislationsuch as the Inducing Infringement of CopyrightsAct, which they argue would in effect outlaw all file-sharingnetworks and subject people to prison sentences for minorinfractions.Further ReadingBusiness Software Alliance. Available online. URL: http://www.bsa.org. Accessed November 18, 2007.Donoghue, Andrew. “Counting the Cost of Counterfeiting.” CNetNews, May 22, 2006. Available online. URL: http://www.news.com/Counting-the-cost-of-counterfeiting/2100-7348_3-6074831.html?tag=item. Accessed November 18, 2007.Evers, Joris. “Fighting Microsoft’s Piracy Check.:” CNet News,June 20, 2006. Available online. URL: http://www.bsa.org.Accessed November 18, 2007.Hopkins, David, Lewis T. Kontnik, and Mark T. Turnage. CounterfeitingExposed: How to Protect Your Brand and Market Share.Hoboken, N.J.: Wiley, 2003.Plastow, Alan L. Modern Pirates: Protect Your Company from theSoftware Police. Garden City, N.Y.: Morgan James, 2006.“Protect Yourself from Piracy.” Microsoft Corporation. Availableonline. URL: http://www.microsoft.com/piracy/. AccessedNovember 18, 2007.SonySony Corporation (NYSE symbol: SNE) is the electronicsbusiness unit of Sony Group, a large Japanese multinationalcompany that plays a leading role in worldwide electronics,games, and entertainment media (movies and music), introducingand shaping many now-familiar standards.The company traces its origin to a radio repair shopstarted by Masaru Ibuka in a bombed-out building inTokyo in 1945. He was soon joined by Akio Morita, andthe men started an electronics company whose name translatesin English to Tokyo Telecommunications EngineeringCorporation. They started by building tape recorders, butin the early 1950s the two entrepreneurs were among theearliest to realize the potential of the transistor, marketingtransistor radios starting in 1956. The devices essentiallyestablished the modern consumer electronics field, perfectlyfitting with a new music fad among American teenagers—rockand roll.With their marketing success, Ibuka and Morita realizedthat they needed a simple, catchy name that would appealto Americans and other non-Japanese customers. In 1958they came up with Sony. Although the name did not exist inany language (and thus could be made proprietary), “Sony”evokes English words such as “sound” and “sonic.” (It alsoresembled a Japanese slang phrase “sony-sony,” for somethinglike what we would call “geeks” or “nerds” today.)Influence on Media and ComputingOne of Sony’s most enduring impacts has been its establishmentof standards for media and storage technologies. Thecompany was not always successful: A famous also-ran wasits Betamax videotape format, which lost out to VHS. However,the company’s successful consumer products haveincluded the following:• Trinitron tubes for televisions and computer monitors(no longer sold in the United States)• Walkman portable music player (1979)• 3.5″ floppy disk (1983), which flourished until thelater 1990s

446 sorting and searching• Discman CD-based music player (1984)• Handycam camcorder and Video format (1985)• Digital audio tape, or DAT (1987)• Blu-ray optical discSony would also become a major player in the consolegaming market (see gaming console). In 1994 the companyintroduced the PlayStation, followed by later modelsin 2000 and 2006. Sony is also a significant seller of digitalcameras, including the Mavica floppy disc (later CD), sincediscontinued. The company also introduced its proprietary“memory stick” for storage.Stumbles and SuccessesIn 2005 a controversy erupted when it was revealed thatSony music CDs included as part of their copy protection(see also digital rights management) a “rootkit” that couldallow PCs to be compromised. Sony eventually agreed withthe Federal Trade Commission (FTC) to exchange theaffected CDs and to reimburse damage to consumers’ computersthat might have occurred while attempting to removethe software. However, in 2007 a similar problem arose withthird-party software packaged with Sony memory sticks.Around the same time, Sony had to recall laptop batteriesthat had serious flaws that could cause them to overheatand catch fire. In 2006 Sony and Dell agreed to replace over4.1 million laptop batteries—this was followed by 1.8 millionSony batteries in Apple laptops and 526,000 in IBMand Lenovo laptops.Despite these setbacks, Sony continues to be very successful,with $70.3 billion in revenue and a net income of $1.07billion in 2007, and about 163,000 employees worldwide.Further ReadingLuh, Shu Shin. Business the Sony Way: Secrets of the World’s MostInnovative Electronics Giant. New York: Wiley, 2003.Nathan, John. Sony. New York: Houghton Mifflin, 1999.Sony America. Available online. URL: http://www.sony.com/.Accessed November 18, 2007.Sony Playstation. Available online. URL: http://www.us.playstation.com/. Accessed November 18, 2007.sorting and searchingBecause they are so fundamental to maintaining databases,the operations of sorting (putting data records in order) andsearching (finding a desired record) have received extensiveattention from computer scientists. A variety of differentand quite interesting sorting methods have been devised(see algorithm).Any application that involves keeping track of a significantnumber of data records will have to keep them sortedin some way. After all, if records are simply inserted as theyarrive without any attempt at order, the time it will take tofind a given record will, on the average, be the time it wouldtake to search through half the records in the database.While this might not matter for a few hundred records ona fast modern computer, it would be quite unacceptable fordatabases that might have millions of records.Sorting ConsiderationsWhile some sorting algorithms are better than others inalmost all cases, there are basic considerations for choosingan approach to sorting. The most obvious is how fastthe algorithm can sort the number of records the applicationis likely to encounter. However, it is also necessary toconsider whether the speed of the sort increases steadily(linearly) as the number of records increases, or it becomesproportionately worse. That is, if an algorithm can sort athousand records in two seconds, will it take 20 seconds for10,000 records, or perhaps five minutes?In most cases one assumes that the records to be sortedare in more or less random order, but what happens if therecords to be sorted are already partly sorted . . . or almostcompletely sorted? Some algorithms can take advantage ofthe partial sorting and complete the job far more quicklythan otherwise. Other algorithms may slow down drasticallyor even produce errors under those conditions.The range or variation in the key (the data field by whichrecords are being sorted) may also play a role. In some casesif the keys are close together, some algorithms may be ableto take advantage of that fact.Finally, the available computer resources must be considered.Today many desktop PCs have 1 GB (gigabyte) ormore of main memory (RAM), while servers or mainframesmay have several GBs. If the database is small enough that itcan be entirely kept in main memory, sorting is fast becauseany record can be accessed in the same amount of time atelectronic speeds. If, however, part of the database must bekept in secondary storage (such as hard drives), the sortingprogram will have to be designed so that it reads a numberof records from the hard drive in a single reading operation,in order to avoid the overhead of repeated disk operations.Most likely the individual batches will be read fromthe disk, sorted in memory, written back to disk, and thenmerged to sort the whole database.Sorting AlgorithmsThere are numerous sorting algorithms ranging from theeasy-to-understand to the commonly used to the exotic andquirky. Only the highlights can be covered here; see FurtherReading for sources for more detailed discussions.Selection SortThe simplest and least efficient kind of sort is called the selectionsort. Rather like a bridge player organizing a hand, theselection sort involves finding the record with the lowest keyand swapping it with the first record, then scanning backthrough for the next lowest key and swapping it with the secondrecord, and so on until all the records are sorted. Whilethis uses memory very efficiently (since the records are sortedin place), it is not only slow, but also gets worse fast. That is,the time taken to sort n records is proportional to n 2 .The selection approach suffers because on each pass thesort determines not only the record with the lowest key but

sorting and searching 447the one with the next lowest key. However, that informationis not retained. The heapsort, invented by John Williams in1964, uses a binary tree to store a heap of sorted records(see tree and heap). Once the heap is built, the tree nodescan be used to store record numbers in a correspondingarray that will represent the sorted database. The heapsortis efficient because no records are physically moved, andthe only memory needed is for the heap and array. The heapsortis generally considered the fastest and most reliablegeneral-purpose sorting algorithm, with a maximum runningtime of log n.Bubble SortThe bubble sort is based on making comparisons and swaps.It makes the most convenient comparison possible: eachrecord with its neighbor. The algorithm looks at the firsttwo records. If the second has a lower key than the first,the records are swapped. The procedure continues with thesecond and third records, then the third and fourth, andso on through all the records, swapping pairs of adjacentrecords whenever they are out of order. After one pass therecord with highest key will have “bubbled up to” the endof the list. The procedure is then repeated for all but the lastrecord until the two highest records are at the end, and soon until all the records are sorted. Unfortunately, the numberof comparisons and swaps that must be made makes thebubble sort as slow as the selection sort.QuicksortThe quicksort improves on the basic bubble sort by firstchoosing a record with a key approximately midway betweenthe lowest and highest. This key is called the pivot. Therecords are then moved to the left of the pivot if they arelower than it, and to the right if higher (that is, the recordsare divided into two partitions). The process is then repeatedIn a bubble sort, pairs of adjacent numbers are compared andswitched if they are out of order. Eventually the lowest values (suchas 2 in this case) will “bubble up” to the front of the list.The Quicksort uses a value called the pivot to partition the list intotwo smaller lists. This process is repeated until the list has beendivided and “conquered” (sorted).to split the left side with a new pivot, and then the right sidelikewise. This is continued until the partition size is one,and the records are now all sorted. (Because of this repeatedpartitioning, quicksort is usually implemented using a procedurethat calls itself repeatedly—see recursion.)Devised by C. A. R. Hoare in 1962, quicksort is muchfaster than the bubble sort because records are moved overgreater distances in a single operation rather than simplybeing exchanged with their neighbors. Assuming an appropriateinitial pivot value is chosen, running time is proportionalto the logarithm of n rather than to the square of n.The difference becomes dramatic as the size of the databaseincreases.Insertion SortThe bubble sort and quicksort are designed to work withrecords that are in random order. However, in many applicationsa database grows slowly over time. At any giventime the existing database is already sorted, so it hardlymakes sense to have to resort the whole database each timea new record is added.Instead, an insertion sort can be used. In its simplestform, the algorithm looks sequentially through the sortedrecords until it finds the first record whose key is higherthan that of the new record. The new record can then beinserted just before that record, much like the way a bridgeplayer might organize the cards in a hand. (Since insertinga record and physically moving all the higher recordsup in memory can be time-consuming, a linked list of keyvalues and associated record number is often used instead.(See list processing.) That way only the links need to bechanged rather than any records being moved.The insertion sort was improved by Donald L. Shell in1959. His “shellsort” takes a recursive approach (like thatin the quicksort), and applies the insertion sort procedureto successively smaller partitions.Another improvement on the insertion sort is the mergesort.As the name implies, this approach begins by creatingtwo small lists of sorted records (using a simple comparisonalgorithm), then merging the lists into longer lists. Mergingis accomplished by looking at the two keys on the top oftwo lists and taking whichever is lowest until the lists areexhausted. The merge sort also lends itself to a recursive

448 sound file formatsapproach, and it is comparable in speed and stability to theheapsort.Hash SortsAll of the sorting algorithms discussed so far rely uponsome form of comparison. However, it also possible to sortrecords by calculating their relative positions or distribution(see hashing). In its simplest form, an array can becreated whose range of indexes is equal to 1 to the maximumpossible key value. Each key is then stored in theindex position equal to its value (that is, a record with a keyof 2314 would be stored in the array at position Array[2314].This procedure works well, but only if the keys are all integers,the range is small enough to fit in memory, and thereare no duplicate keys (since a duplicate would in effectoverwrite the record already stored in that position).A more practical approach is to use a formula (hashfunction) that should create a unique hash value for eachkey. The function must be chosen to minimize “collisions”where two keys end up with the same hash value, whichcreates the same problem as with duplicate keys. A hashsort is quite efficient within those constraints.SearchingOnce one has a database (sorted or not), the next questionis how to search for records in it. As with sorting, thereare a variety of approaches to searching. The simplest andleast efficient is the linear search. Like the selection sort,the linear search simply goes through the database recordssequentially until it finds a matching key or reaches the endwithout a “hit.” If there is indeed a matching record, on theaverage it will be found in half the time needed to processthe whole database.In most real applications the database will have beensorted using one of the methods discussed earlier. Here, thebasic approach is to do a binary search. First the key in themiddle record in the database is examined. The key is comparedwith the search key. If the search key is smaller, thenany matching key must be in the first half of the database.Otherwise, it must be in the second half (unless, of course,it happens to be the matching key). The process is thenrepeated. That is, if the key is somewhere in the first half,that portion of the list is in turn split in half and its middlevalue is examined, and the comparison to the search key ismade. Thus, the area in which the matching key must befound is progressively cut in half until either the matchingkey is found or there are no more records to check. Becauseof the power of successive division, the binary search isvery quick, and doubling the size of the database meansadding only one more comparison on the average.Sometimes knowledge about the distribution of keysin the database can be used to improve even the binarysearch. For example, if keys are alphabetical and the searchkey begins with S, it is likely to be faster to pick a startingpoint near the end of the list rather than from the middle. Abinary tree (see tree) can be constructed from the keys in adatabase in order to analyze the most likely starting pointsfor a search.Finally, hashing (as previously discussed) can be usedto quickly calculate the expected location of the desiredrecord, provided there are no collisions.Further ReadingKnuth, Donald E. Art of Computer Programming, Volume 3: Searchingand Sorting. 2nd ed. Upper Saddle River, N.J.: Addison-Wesley Professional, 1998.Ploedereder, Erhard. “The Sort Algorithm Animator V1.0.” Availableonline. URL: http://www.iste.uni-stuttgart.de/ps/Ploedereder/sorter/sortanimation2.html.Accessed August 21, 2007.Sedgewick, Robert. Algorithms in C++: Parts 1–4: Fundamentals,Data Structures, Sorting, Searching. Upper Saddle River, N.J.:Addison-Wesley, 1998.Wilt, Nicholas. Classical Algorithms in C++: With New Approachesto Sorting, Searching, and Selection. New York: Wiley, 1995.sound file formatsThere are a number of ways that sound can be sampled,stored, or generated digitally (see music, computer). Herewe will look at some of the most popular sound file formats.WAVThe WAV (wave) file format is specific to Microsoft Windows.It essentially stores the raw sample data that representsthe digitized audio content, including informationabout the sampling rate (which in turns affects the soundquality). Since WAV files are not compressed, they can consumeconsiderable disk space.AIFFAIFF stands for Audio Interchange File Format, and is specificto the Apple Macintosh and to Silicon Graphics (SGI)platforms. Like WAV, it stores actual sound sample data. Avariant, AIFF-C, can store compressed sound.AUThe AU (audio) file format was developed by Sun Microsystemsand is used mainly on UNIX systems, and also in Javaprogramming.MIDIMIDI stands for Musical Instrument Digital Interface.Unlike most other sound formats, MIDI files don’t representsampled sound data. Rather, they represent virtual musicalinstruments that synthesize sound according to complexalgorithms that attempt to mirror the acoustic characteristicsof real pianos, guitars, or other instruments. SinceMIDI is like a “score” for the virtual instruments ratherthan storing the sounds, it is much more compact thansampled sound formats. MIDI is generally used for musiccomposition rather than casual listening.MP3MP3 is actually a component of the MPEG (Moving PictureExpert Group) multimedia standard, and stands for MPEG-1 Audio Layer 3. It is now the most popular sound format,using compression to provide a balance of sound quality

space exploration and computers 449and compactness that is comparable to that of standardaudio CDs and suitable for most listeners. The compressionalgorithm relies upon psychoacoustics (the study ofhow people perceive the components of sound) to identifyfrequencies that humans can’t hear, and thus may be safelydiscarded. The digitized sound on a CD is compressed upto 1/12 or less of its original size, so a 630 MB CD becomesabout 50 MB in MP3 files.Since most PC users now have hard drives rated in thehundreds of gigabytes (GB), it is easy to store an extensivemusic library in MP3 form. Most PCs now come withsoftware that can play MP3 files (such as Windows MediaPlayer), and there are also free and shareware programsfrom a variety of sources, as well as plug-ins for playingsound files directly from the Web browser.Since MP3 is much more compact than “raw” CD format,users with inexpensive CD-RW drives can “burn”large amounts of music in MP3 form onto a single CD. Thisis typically done using software that “rips” the raw tracksfrom an audio CD and converts them to an MP3 file, whichcan then be stored on the PC’s hard drive.In recent years portable media players such as the iPodhave become ubiquitous (see music and video players,digital). MP3 is the most popular format for music that isnot digitally protected from copying (see digital rightsmanagement). However, because MP3 involves a numberof patents, it is not included by default in Linux distributions,which instead provide Ogg, a “container” that can beused for a variety of formats (see codecs).Further ReadingAudio File Types. Available online. URL: http://www.fileinfo.net/filetypes/audio. Accessed August 22, 2007.Johnson, Dave, and Rick Broida. How to Do Everything with MP3and Digital Music. New York: McGraw Hill Professional, 2001.Young, Robert. The MIDI Files. 2nd ed. New York: Prentice Hall,2001.space exploration and computersIt might have been barely possible to put a satellite (or person)in orbit without the use of computers, but any moreextensive exploration of space requires many types of computerapplications.Human Space ExplorationFlying to the Moon required precisely calculated and controlled“burns” to inject the Apollo spacecraft from orbitinto its arcing trajectory to the Moon. The detachableLunar Excursion Module (LEM) also had a computer onboard (roughly comparable in power to something foundin today’s programmable calculators). Although the pilotcontrolled the final landing manually, the computer interpretedradar data to fix the lander’s position, monitored fuelconsumption, and provided other key data.The Space Shuttle, the most complex vehicle ever builtby human beings, has five onboard computer systems thatcontrol flight maneuvers (including rendezvous and dockingoperations), monitor and control environmental conditions,keep track of fuel, batteries, life support, and otherconsumables, and provide many other functions to supportthe crew’s tasks and experiments.Automated Space ExplorationThus far, human explorers have flown no farther than theMoon. However, in the last 40 years an extensive survey ofmost of the solar system has been carried out by robot (thatis to say, computerized) probes and landers. These probeshave landed on Mars and visited every planet except Pluto,as well as making close approaches to asteroids and comets.The control computer aboard a space probe has severaljobs. It must keep the probe oriented in such a waythat its solar panels can receive energy from the Sun, aswell as keeping an antenna pointed toward Earth so it canreceive commands and return data from the probe’s scientificinstruments.Starting with Voyager 2 (a probe that is still returningdata from more than 7 billion miles from Earth), space probecomputers have been more autonomous, able to make attitudecorrections and course corrections as needed. The onboardcomputer can even be reprogrammed with new instructionssent from Earth. Space probes have returned incrediblydetailed pictures of the surface of the Moon and planets, preparingthe way for human missions or robot landers.Landers reach a fixed point on a planetary surface andtransmit photographs, temperature, radiation, and otherreadings. Probes can survive only for minutes on the hostilesurface of Venus, but have functioned for many monthson Mars. In a remarkably ambitious mission beginning in1976, the two Viking Mars landers were able to carry outexperiments on soil samples in an unsuccessful attempt tofind evidence of life while a third probe mapped the planet’ssurface from orbit. Besides demonstrating remarkable reliability(Viking 2 was still operating in 1982 when it wasaccidentally turned off by a remote command), the missionalso demonstrated the ability to coordinate surface andorbital exploration.In July 1997, the Mars Pathfinder probe landed on the redplanet, rolling and bouncing to a stop inside a sort of giantairbag. After deflating, the Pathfinder base station deployedthe Sojourner mobile robot. This vehicle (see robotics)was controlled by operators on Earth, but because of the10–15-minute time delay in signals arriving from Earth,the Sojourner had some autonomous ability to avoid collisionsor other hazards. The onboard computer also had tocompress and transmit images and other data. The followonMars Exploration Rover (MER) program began in 2003with the launching of two larger surface rovers dubbedSpirit and Opportunity. Landing in January 2004, the rovershave shown remarkable durability, still functioning in early2008, far beyond their original three-month mission life.The need to build compact computers and other electronicsfor space exploration helped spur the development of techniquesnow found in garden-variety consumer electronics.Space computers are also important for demonstrating thereliability and robustness that is necessary for applicationson Earth (such as in the military). Space electronics must beshielded and “hardened” to withstand the intense solar radiation,extreme changes in temperature, and electromagnetic

450 Spafford, Eugene H.and computer science from the State University of New Yorkat Brockport. He then earned M.S. (1981) and Ph.D. (1986)degrees at the Georgia Institute of Technology, with his graduatework focused on distributed operating systems.How do scientists look at images that are sent back from anotherplanet and determine what is interesting and needs further investigation?Mars rover scientists do this very task during surfacemission operations. Each day, rovers send to Earth new imagesthat the science team must examine. These images allow the scientiststo think of hypotheses that relate to help the science teamdecide what to study and determine what experiments they willconduct. (NASA photo)fluxes or surges. Redundancy can be used where possible, butweight is always at a high premium. With the exception ofcertain satellites and the Hubble Space Telescope, space computerscannot receive on-site service visits.Because of the high cost and risk of maintaining humanlife for long periods in space, it is likely that robotic probesand rovers will remain the main means for space explorationin the early 21st century.Further ReadingFurmiss, Tim. A History of Space Exploration and Its Future. London:Mercury Books, 2006.Hall, Eldon C. Journey to the Moon: The History of the Apollo GuidanceComputer. Reston, Va.: American Institute of Aeronautics,1996.Mars Exploration Rover Mission (Jet Propulsion Laboratory).Available online. URL: http://marsrovers.jpl.nasa.gov/home/index.html. Accessed August 22, 2007.Mars Pathfinder [archive]. Available online. URL: http://mpfwww.jpl.nasa.gov/MPF/index1.html. Accessed August 22, 2007.Matloff, Gregory L. Deep Space Probes: To the Outer Solar Systemand Beyond. 2nd ed. New York: Springer, 2005.Squyres, Steve. Roving Mars: Spirit, Opportunity, and the Explorationof the Red Planet. New York: Hyperion, 2005.Spafford, Eugene H.(1956– )AmericanComputer ScientistEugene (Gene) H. Spafford is a computer scientist and pioneerin network security. Spafford earned a B.A. in mathematicsUsenet and BeyondSpafford played a key role in the development of the Usenet(see netnews and newsgroups), including the backbonesand connections that provided for the efficient distributionof a growing volume of news posts, as well as the systemfor naming newsgroups. He also created basic introductorydocumentation to help new users participate in the systemresponsibly.On the night of November 2, 1988, sites throughoutthe Internet began to shut down. The culprit was a wormprogram (see computer virus) that Spafford analyzed ina technical paper. The worm would unfortunately only bethe first of a legion of worms and viruses that would infectthe network, and Spafford would apply considerable effortto helping cope with them. Since then Spafford has beena computer security consultant and adviser for numerousorganizations including Microsoft, Intel, the U.S. Air Force,the National Security Agency, the FBI, and the National ScienceFoundation.Spafford has been on the faculty at Purdue Universitysince 1987. In 2007, he was appointed an adjunct professorof computer science at the University of Texas at San Antonio.He is also executive director of the university’s newInstitute for Information Assurance.Spafford has served on the boards of a number of professionalsocieties, including the Computer ResearchAssociation and the U.S. Public Policy Committee of theAssociation for Computing Machinery (ACM). He has writtenseveral books and hundreds of papers on UNIX andInternet security and related ethical issues. Spafford becamean ACM Fellow in 1997 and a Fellow of the American Associationfor the Advancement of Science in 1999. He wasinducted as a Fellow of the Institute for Electrical and ElectronicsEngineers (IEEE) in 2000 and received its TechnicalAchievement Award in 2006. In 2007 Spafford received theACM President’ Award.Further ReadingGarfinkel, Simson L., and Eugene H. Spafford. Practical UNIXSecurity. Sebastapol, Calif.: O’Reilly, 2003.Rospach, Chuq von, with editing additions by Eugene H. Spafford.“A Primer on How to Work with the Usenet Community.”Available online. URL: http://www.faqs.org/faqs/usenet/primer/part1/. Accessed November 18, 2007.Spafford, Eugene H. “The Internet Worm: Crisis and Aftermath.”Communications of the ACM 32 (June 1989): 678–687. Availableonline. URL: http://vx.netlux.org/lib/aes01.html. AccessedNovember 18, 2007.Spaf’s Home Page. Purdue University. Available online. URL: http://homes.cerias.purdue.edu/~spaf/. Accessed November 18, 2007.spamIn a well-known 1970 sketch by the British comedy troupeMonty Python, a customer is trying to order a breakfast item

speech recognition and synthesis 451that does not include Spam (the popular luncheon meat). Agroup of Vikings then keeps interrupting the conversationby loudly singing “Spam, lovely Spam, wonderful Spam. . . .”Segue to the mid-1990s when people (including a legal firm)began automatically posting hundreds of identical messageson Usenet (see netnews and newsgroups) groups; thesketch came to mind and the postings were quickly dubbed“spam”—although the term may actually date back to the1980s. As news of the spam grew, some administrators andusers used “cancelbots” to automatically delete the offendingmessages; others opposed this as censorship, and manynewsgroups became effectively unreadable.While spam can appear in any communications medium(including chat, instant messaging, and even blogs), themost prevalent type is e-mail spam, which costs U.S. businessesbillions of dollars a year in processing expenditures,lost time, and damage caused by malicious software (malware)for which spam can be either a delivery vehicle or aninducement. In 2007 an estimated 90 billion spam messageswere sent each day.The fundamental driving force of spam is the fact that,given one has Internet access, sending e-mail costs essentiallynothing, no matter how many messages are sent. Thuseven if only a tiny number of people respond to a spamsolicitation (such as for sexual-enhancement products), theresult is almost pure profit for the spammer.Besides directly making fraudulent solicitations forproducts that are ineffective, counterfeit, or nonexistent,spam carries two other dangers: inducements to click tovisit fake Web sites (see phishing and spoofing) andattachments containing viruses or other dangerous software(see computer virus and spyware and adware).Fighting SpamMuch spam is spread by first compromising thousands ofsystems (via viruses) and planting in them “bots,” or softwarethat can be programmed to mail spam. The controllersof “botnets” can then sell their service to spammerswho want to get their message distributed widely. Thespammers can also buy lists of e-mail addresses that havebeen “harvested” from postings, poorly secured Web sites,and so on.Ways to stop the spread of spam include the following:• e-mail filtering software, using a combination of textanalysis by keyword or statistical correlation (seeBayesian analysis) and lists of Internet locations(domains) associated with spamming; filtering can bedone both by service providers and individual users,or collaboratively• tightening the technical requirements for messages tobe accepted by mail servers (much spam has poorlyformatted headers)• improving techniques for blocking the viruses usedby spammers to set up their bots—see computervirus and firewall• attempting to shut down the infrastructure that supportsspam operations, such as hosts who allow bulke-mail, and sellers of spamming software and illicitlygathered address listsSpam is illegal in a number of respects. Spamming is againstthe “acceptable use policy” of most Internet Service Providers(ISP), though willingness to enforce these rules varies.In 2003 Congress passed the CAN-SPAM act, whichbans bulk e-mail that contains misleading subject or headerlines, but has been criticized for being weak and for preemptingmore stringent state laws. (The law also requiresthat messages include an opt-out provision, but spammerssimply use this to verify that the e-mail address is valid.)Although filtering software and other measures canreduce the amount of spam seen by the average user, spammersand spam-fighters continue their relentless battle witheach countermeasure, leading to altering the spam to makeit more likely to pass through. In the long run probablyonly a Net-wide authentication of all e-mail senders and/ora small per-message e-mail fee could effectively banish thescourge of spam.Further ReadingBoutin, Paul. “Can E-mail Be Saved?” InfoWorld, April 16, 2004.Available online. URL: http://www.infoworld.com/article/04/04/16/16FEfuturemail_1.html. Accessed November 18, 2007.Garretson, Cara. “12 Spam Research Projects That Might Make aDifference.” Network World, November 2007. Available online.URL: http://www.networkworld.com/news/2007/112007-spamresearch.html.Accessed April 28, 2008.Gregory, Peter H., and Michael A. Simon. Blocking Spam & Spywarefor Dummies. Hoboken, N.J.: Wiley, 2005.Lee, Nicole. “How to Fight Those Surging Splogs” [spam blogs].Wired News, October 27, 2005. Available online. URL: http://www.wired.com/culture/lifestyle/news/2005/10/69380.Accessed November 18, 2007.Markoff, John. “Attack of the Zombie Computers Is a GrowingThreat.” New York Times, January 7, 2007. Available online.URL: http://www.nytimes.com/2007/01/07/technology/07net.html. Accessed November 18, 2007.McWilliams, Brian S. Spam Kings: The Real Story behind the High-Rolling Hucksters Pushing Porn, Pills, and %*@)# Enlargements.Sebastapol, Calif.: O’Reilly, 2004.Naughton, Philippe. “Arrest of ‘Spam King’ No Relief for Inboxes.”Times (London) online, June 1, 2007. Available online. URL:http://technology.timesonline.co.uk/tol/news/tech_and_web/article1870548.ece. Accessed November 18, 2007.Spammer-X. Inside the Spam Cartel: Trade Secrets from the DarkSide. Rockland, Mass.: Syngress, 2004.Zeller, Tom. “The Fight Against V1@gra (and Other Spam).” NewYork Times, May 21, 2006. Available online. URL: http://www.nytimes.com/2006/05/21/business/yourmoney/21spam.html?_r=1&oref=slogin. Accessed November 18, 2007.speech recognition and synthesisThe possibility that computers could use spoken languageentered popular culture with Hal 2001, the self-aware talkingcomputer in the film 2001: A Space Odyssey. On a practicallevel, the ability of users to communicate using speechrather than a keyboard would bring many advantages, suchas mobile, hands-free computing and greater independencefor disabled persons. Considerable progress has been madein this technology since Hal “talked” in 1968.

452 spreadsheetSpeech recognition begins with digitizing the speechsounds and converting them into a standard, compact representation.The analysis can be based on matching the inputsounds to one of about 200 “spectral equivalence classes”from which the representation can be created. Alternatively,algorithms can use data based on modeling how the humanvocal tract produces speech sounds, and extract key featuresthat then become the speech representation. Neuralnetworks can also be “trained” to recognize speech features(see neural network). The latter two approachesare potentially more flexible but also considerably more difficult,and tend to be used in research rather than in commercialvoice recognition systems.Whichever form of representation is used, it must thenbe matched to the characteristics of particular words orphonemes, usually with the aid of sophisticated statisticaland time-fitting techniques. The simplest systems work ona word level, which may suffice if the system is restrictedto a simple vocabulary and the user speaks slowly and distinctlyenough. Such systems usually require that the user“train” the system by speaking selected words and phrases.The user can then control the system with a set of voicecommands.Creating a system that can handle the full range of languageis much more difficult. This kind of system breaksthe language down into phonemes, its basic sound constituents(English has about 40 phonemes). The system includesa stored dictionary of phoneme sequences and the correspondingwords. However, “understanding” which wordsare being spoken is more than a matter of matching phonemesequences to a dictionary. For one thing, the sound ofthe first or last phoneme in a word can change dependingon the phoneme in an adjacent word.Once the speech has been recognized, it can be convertedto character data (see characters and strings)and treated as though the text had been entered from thekeyboard. This means, for example, that a user could dictatetext to be placed in a word processor document as wellas using voice commands to perform tasks such as formattingtext. (Special words can be used to introduce and endcommands.)Voice control and dictation have been offered commerciallyby such companies as Dragon Systems and Kurzweil.Microsoft now includes speech recognition and synthesisfacilities in the latest version of its popular office suite,Office 2007.Voice SynthesisThe other part of the speech equation is the ability to havethe computer turn character codes into spoken words. Themost primitive approach is to digitally record appropriatespoken words or phrases, which can then be replayedwhen speech is desired. Naturally, what is spoken is limitedto what is available in the recorded library, although thewords and phrases can be combined in various ways. Sincethe combinations lack the natural transitions that speakersuse, the result sounds “mechanical.” Common applicationsinclude automated announcements in train stations or inprompts for voicemail systems.To produce a synthesizer that can “speak” any naturallanguage text, the system must have a dictionary that givesthe phonemes found in each word. The 40 or so differentphonemes can then be digitally recorded and the systemwould then identify the phonemes in each word and playthem to create speech. While this solves the limited vocabularyproblem, the synthesized speech is rather unnaturaland hard to understand. This is because, as noted earlier,the way phonemes are sounded changes under the influenceof adjacent phonemes, and these nuances are lackingin a simple phoneme playback.More sophisticated voice synthesis systems record naturalspeech and identify all the possible combinations of halfof a phoneme and half of an adjacent phoneme. That way thepossible transition sounds are also recorded, and the resultingspeech sounds considerably more natural. The drawbackis that more memory and processing power are required, butthese commodities are becoming increasingly cheaper.Speech recognition and synthesis technology has madeonly slow inroads into the computing mainstream, suchas office applications. Given the costs of hardware, software,and training, the keyboard remains more productiveand cost-effective for most applications. However, voicetechnology does have a growing number of specialty uses,including security and access systems, speech synthesis fordisabled persons who cannot see or speak, and enablingservice robots to interact with people in the environment.Speech technology has also been a long-standing topic inartificial intelligence and robotics research.Further ReadingBrown, Robert. “Exploring New Speech Recognition and SynthesisAPIs in Windows Vista.” MSDN Magazine. Available online.URL: http://msdn.microsoft.com/msdnmag/issues/06/01/speechinWindowsVista/. Accessed August 22, 2007.Holmes, John, and Wendy Holmes. Speech Synthesis and Recognition.2nd ed. Boca Raton, Fla.: CRC Press, 2001.Huang, Xuedong, Alex Acero, and Hsiao-Wuen Hon. Spoken LanguageProcessing: A Guide to Theory, Algorithm, and SystemDevelopment. Upper Saddle River, N.J.: Prentice Hall, 2001.Jurafsky, Daniel, and James H. Martin. Speech and Language Processing:An Introduction to Natural Language Processing, ComputationalLinguistics and Speech Recognition. Upper SaddleRiver, N.J.: Prentice Hall, 2000.Speech Technology (Google Directory). Available online. URL:http://www.google.com/Top/Computers/Speech_Technology/.Accessed August 22, 2007.Speech Technology Research, Development, and Deployment(Carnegie Mellon University). Available online. URL: http://www.speech.cs.cmu.edu/. Accessed August 22, 2007.spreadsheetWith the possible exception of word processing, no personalcomputer application caught the imagination of thebusiness world as quickly as did the spreadsheet, whichfirst appeared as Daniel Bricklin’s VisiCalc in 1979. Visi-Calc quickly became the “killer app”—the application thatcould justify corporate purchases of Apple II computers.When the IBM PC began to dominate the office computingindustry in the mid-1980s, it had a new spreadsheet, Lotus1-2-3. By the end of the decade, however, Microsoft’s Excel

spyware and adware 453spreadsheet had come to the forefront, running on MicrosoftWindows. It remains the market leader today.How Spreadsheets WorkA spreadsheet is basically a tabular arrangement of rowsand columns that define many individual cells. Typically,the columns are lettered (A to Z, then AA, AB, and so on)while the rows are numbered. A particular cell is referencedusing its column and row coordinates; thus A1 is the cell inthe upper left corner of the spreadsheet.Any cell can contain a numeric value, a formula, or a label(such as for giving a title to the spreadsheet or some section ofit). Formulas reference the values in other cell locations. Forexample, if the formula =SUM (A1:B1) is inserted into cell C1,when the spreadsheet is calculated the sum of the contents ofcells A1 and B1 will be inserted into C1. Modern spreadsheetslet users select from a variety of functions (predefined formulas)for such things as interest or rates of return. Instead ofhaving to type the individual coordinates of cells to be usedin a formula, he or she can simply click on or drag across thecells to select them. Formulas can also include conditionalevaluation (similar to the If statements found in programminglanguages—see branching statements).Spreadsheets provide a variety of “housekeeping” commandsthat can be used for functions such as copying ormoving a range of cells or “cloning” a cell’s value into arange of cells. Large spreadsheets can be broken down intomultiple linked spreadsheets to make it easier to understandand maintain.Macros offer a powerful way to simplify and automatespreadsheet operations. A macro is essentially a set of programmedinstructions to be carried out by the spreadsheet(see macro). One use of macros is to carry out complicatedprocedures by taking advantage of features similarto those found in programming languages such as VisualBasic. Macros can also be used to automate data entry intothe spreadsheet and validate the data. Depending on theircomplexity, macros can either be typed in as a series ofstatements or recorded as the user takes appropriate menuand mouse actions. “Solver” utilities can also simplify theprocess of tweaking input variables in order to achieve adefined goal. Although spreadsheets can certainly solvemany types of algebraic equations, symbolic manipulationis better handled by programs such as Mathematica (seemathematics software).Besides having extensive graphics and charting capabilities,modern spreadsheets are often part of integratedoffice programs (see application suite). Thus, a MicrosoftExcel spreadsheet could obtain data from an Access databaseand create charts suitable for Web pages or PowerPointpresentations.Further ReadingBalakrishnan, Nagraj, Barry Render, and Ralph M. Stair, Jr. ManagerialDecision Modeling with Spreadsheets. 2nd ed. UpperSaddle River, N.J.: Prentice Hall, 2006.Google Docs and Spreadsheets. Available online. URL: http://docs.google.com. Accessed August 22, 2007.Harvey, Greg. Microsoft Office Excel 2007 for Dummies. Hoboken,N.J.: Wiley, 2007.Hayden, Yvonne. So You Need to Make a Spreadsheet: A Quick Startto Microsoft Excel 2003. Chandler, Ariz.: Copadego Publishing,2006.Jelen, Bill, ed. The Spreadsheet at 25: The 25 Year Evolution of theInvention that Changed the World. Uniontown, Ohio: HolyMacro! Books, 2005.Neuwirth, Ertich. “Spreadsheets, Mathematics, Science, andStatistics Education.” Available online. URL: http://sunsite.univie.ac.at/Spreadsite/. Accessed August 22, 2007.spyware and adwareSpyware and adware are two pervasive threats to computerusers. Both are programs that are installed more or lesssurreptitiously, often accompanying an attractive-looking“free” software package or media download. Depending onhow widely it is defined, as many as eight out of 10 PCsmay be infected by some sort of spyware. Signs of infectioncan include the system slowing down or periodically freezing,Web browsers that fail to display the expected homepage or search results, and the appearance of numerousunwanted pop-up windows (a sign of adware).Ranging from least to most harmful, spyware andadware can do the following:• Display annoying advertising that can clog up thescreen or cover up information (some adware can alsobe spyware that uses information about the user to targetadvertising)• Track Web browsing to provide information to sell tomarketers (see cookies)• Obtain personal information for use in identity theft• Install keyloggers (programs that record keystrokes,such as passwords being entered) or other “backdoor” or “trojan” programsStopping SpywareGrowing concern about spyware has prompted the use ofantispyware programs such as Ad-Aware and Spybot-Search& Destroy, as well as a free program from Microsoft. Antispywareprograms are also being included in popular securitysuites from companies such as Symantec and McAfee.The programs work similarly to antivirus programs, watchingfor suspicious behavior or “signatures” matching knownspyware or adware. Depending on the program, the spywarecan be blocked from executing at all or removed fromthe system.The software varies considerably in effectiveness, sousers may have to run several different programs to completelyremove an “infestation.”Spyware has been generally given a lower priority thanviruses or even spam. When challenged, spyware makersgenerally claim that the user authorized its installation (atleast implicitly) by installing the utility or other softwarethat contains it. Although antispyware legislation has beenintroduced in Congress, it has not passed as of mid-2008.However, state officials such as former New York StateAttorney General Eliot Spitzer successfully sued a spywarecompany, winning a $7.5 million settlement.

454 SQLFurther Reading“Antispyware.” PC Magazine. Available online. URL: http://www.pcmag.com/category2/0,1738,1639157,00.asp. Accessed November18, 2007.Chadbrow, Eric. “Spyware and Adware Continue to Plague PCs.”InformationWeek. March 27, 2006. Available online. URL:http://www.informationweek.com/story/showArticle.jhtml?articleID=183702594. Accessed November 18, 2007.Gregory, Peter H., and Michael A. Simon. Blocking Spam & Spywarefor Dummies. Hoboken, N.J.: Wiley, 2005.“Magoo’s Wise Words: Guide to Eliminating Spyware.” Availableonline. URL: http://guides\radified.com/magoo/guides/spyware/remove_spyware_01.htm. Accessed November 18,2007.Shetty, Sachin. “Introduction to Spyware Keyloggers,” April 14,2005. Available online. URL: http://www.securityfocus.com/infocus/1829. Accessed November 18, 2007.SQLStructured query language was originally developed in theearly 1970s as a command interface for IBM mainframedatabases. Today, however, SQL has become the linguaModern spreadsheets have many sophisticated features. Microsoft Excel, for example, has a “Solver” module that can be used to solve for particularvalues or to maximize or minimize specified values.

SQL 455Structured Query Language (SQL) is a standardized way to query and manipulate databases. Here the statement SELECT NUMBER, NAME,PRICE WHERE PRICE >= 50.00 extracts only the records meeting that criterion.franca for relational database systems (see database managementsystem).A relational database (such as Oracle, Sybase, IBM DB2,and Microsoft Access) stores data in tables called relations.The columns in the table describe the characteristics ofan entity (corresponding to data fields). For example, in acustomer database the Customer table might include attributessuch as customer number, First_name, Last_Name,Street, City, Phone_number, and so on. The rows in thetable (sometimes called tuples) represent the data recordsfor the various customers.Many database systems have more than one table. Forexample, a store’s database might contain a Customers table(for information identifying a customer), an Item table (givingcharacteristics of an item, such as price and number instock), and a Transaction table (whose characteristics mightbe customer number, date, item bought, and so on). Noticethat the Transaction record contains both a customer numberand an item number. It thus serves as a sort of bridge orlink between the Customer and Item tables.SQL provides commands that can be used to specify andaccess components of a database. For example, the INSERTand DELETE commands can be used to add or remove rows(records) from tables.To query a database means to give criteria for selectingcertain records from a table. For example, the querySELECT * FROM CUSTOMERS WHERE LAST_NAME =“Howard”would return the complete records for all customers whoselast name is Howard. If only selected fields are desired, theycan be specified like this:SELECT NUMBER, NAME, PRICE FROM ITEMS WHEREPRICE > = 50.00This query will display the Number, Name, and Price fieldsfor all items whose price is greater than or equal to $50.00.SQL includes many commands to further refine dataprocessing and reporting. There are built-in mathematicalfunctions as well as a GROUP BY command for furtherbreaking down a report by a particular field name orvalue.SQL can be used interactively by typing commands ata prompt, but database applications designed for less technicalusers often provide a user-friendly query form (andperhaps menus or buttons). After the user selects the appropriatefields and values, the program will then generate thenecessary SQL statements and send them to the internal“database engine” for processing. The results will then bedisplayed for the user.SQL procedures can be stored and managed as part ofa database. SQL can also be “embedded” within a morecomplete programming language environment so that, forexample, a Java program can perform SQL operations whileusing Java for processing that cannot be specified in SQL.In the mid-1990s an object-oriented version of SQL calledOQL (object query language), allowing the use of that popularparadigm for database operations (see object-orientedprogramming).One of the most popular implementations of SQL isMySQL, which is privately owned and developed but availablefor free license on many platforms, including Windowsand Linux. A number of applications are designed to workwith MySQL databases: see, for example, wikis and Wikipediaand YouTube.Further ReadingForta, Ben. Sams Teach Yourself SQL in 10 Minutes. 3rd ed. Indianapolis:Sams, 2004.Kofler, Michael. The Definitive Guide to MySQL 5. 3rd ed. Berkeley,Calif.: Apress, 2005.MySQL home page. Available online. URL: http://mysql.org/.Accessed August 22, 2007.Rankins, Ray, et al. Microsoft SQL Server 2005 Unleashed. Indianapolis:Sams, 2006.Tahaghoghi, Seyed M. M., and Hugh Williams. Learning MySQL.Sebastapol, Calif.: O’Reilly Media, 2006.Taylor, Allen G. SQL for Dummies. 6th ed. Hoboken, N.J.: Wiley,2006.

456 stackstackOften a temporary storage data area is needed duringprocessing. For example, a program that calls a procedure(see procedures and functions) usually needs to passone or more data items to the procedure. These itemsare specified as arguments that will be matched to theprocedure’s defined parameters. For example, the procedurecallSquare (50, 50, 20)could draw a square whose upper left corner is at thescreen coordinates 50, 50 and whose length per side is 20pixels.When the compiler generates the machine code for thisstatement, that code will probably instruct the processorto store the numbers 50, 50, and 20 onto a stack. A stack issimply a list that represents successive locations in memoryinto which data can be inserted. The operation of astack can be visualized as being rather like the springloadedplatform onto which dishes are stacked for washingin some restaurants. As each dish (number) is added, thestack is “pushed.” Because only the item “on top” (the lastone added) can be removed (“popped”) at any given time,a stack is described as a LIFO (last in, first out) structure.(Note that this is different from a queue, where items canbe added or removed from either end [see queue].)Stacks are useful whenever nested items must betracked. For example, a procedure might call a procedurethat in turn calls another procedure. The stack can keeptrack of the parameters (as well as the calling address) foreach pending procedure.Stacks can also be used to evaluate nested arithmeticexpressions. For example, the expression that we write inconventional (prefix) notation as7 * 5 + 2can be represented internally in postfix form as:* + 5 7 2Here one stack can be used to hold the operators (* +) andone the operands (5 7 2). The evaluation then proceeds inthe following steps:Pop the * from the operator stackSince * is a binary operator (one that needstwo operands), pop the 5 and 7 from theoperand stackMultiply 5 and 7 to get 35.Pop the + from the operator stack.Pop the 35 (which is now on the top of theoperand stack) and the 2Add 35 and 2 to get 37.An interesting programming language uses this stackmechanism for all processing (see forth). In working withstacks, it may be necessary to keep in mind any limitationson the amount of memory allocated to the stack, although astack can also be implemented dynamically as a linked list(see list processing).Further Reading“Data Structures/Stacks and Queues.” Wikibooks. Availableonline. URL: http://en.wikibooks.org/wiki/Data_Structures/Stacks_and_Queues. Accessed August 22, 2007.Stallman, Richard(1953– )AmericanComputer ScientistRichard Stallman created superb software tools—the programsthat help programmers with their work. He wenton to spearhead the open source movement, a new way todevelop software.Stallman was born on March 16, 1953, in New YorkCity. He quickly showed prodigious talent for mathematicsand was exploring calculus by the age of eight. Not muchlater, his summer camp reading included a manual for theIBM 7094 mainframe belonging to one of the counselors.Fascinated with the idea of programming languages, youngRichard began writing simple programs, even though hehad no access to a computer.Fortunately, a high school honors program let himobtain some time on a mainframe, and his programmingtalents led to a summer job with IBM. While studyingfor his B.A. in physics at Harvard (which he received in1970), Stallman found himself sneaking across town tothe MIT Artificial Intelligence Lab. There he developedEmacs, a powerful text editor that could be programmedwith a language modeled after LISP, the favorite languageof AI researchers. While working on Emacs and othersystem software for the AI Lab, Stallman participatedin the unique MIT “hacker culture.” (During the 1970s,“hacker” still meant a creative computing virtuoso, not acyber-criminal.)Stallman’s experience in the freewheeling, competitiveyet cooperative atmosphere at MIT led him to decidein 1984 to start the Free Software Foundation, whichwould become his life’s work. Stallman and his colleaguesat the FSF worked through the 1980s to develop GNU.At the time, UNIX, the operating system of choice formost campuses and researchers, required an expensivelicense from Bell Laboratories. GNU (a recursive acronymfor “GNU’s Not UNIX”) was intended to include all thefunctionality of UNIX but with code that owed nothingto Bell Labs. Stallman’s key contributions to the projectincluded the GNU C compiler and debugger, as well ashis management of a cooperative effort in which manytalented programmers would coordinate their efforts overthe Internet.By the early 1990s, most of GNU was complete exceptfor a key component: the kernel containing the essentialfunctions of the operating system. A Finnish programmer

statistics and computing 457named Linus Torvalds decided to write the kernel and integrateit with much of the existing GNU software. The resultwould become known as Linux, and today it is a popularoperating system that runs on many servers and workstations.While acknowledging Torvalds’s efforts, Stallmaninsists that the operating system is more properly calledGNU Linux, to reflect the large amount of GNU code itemploys.In recent years Stallman has best been known as a vigorousadvocate for free software (see open-source movement)and for creating alternative structures for controllingits distribution, such as the various forms of the GeneralPublic License (GPL). Stallman has been accused of beingrigid and abrasive, such as in his urging that certain terminologybe used, or, in the case of the phrase “intellectualproperty,” not used.Stallman has received a number of important awards,including the ACM Grace Hopper Award (1990), ElectronicFrontier Foundation Pioneer Award (1998), and a MacArthurFoundation fellowship (1990).Further ReadingFree Software Foundation. Available online. URL: http://www.fsf.org/. Accessed August 22, 2007.Stallman, Richard M. Free Software, Free Society: Selected Essaysof Richard M. Stallman. Boston: Free Software Foundation,2002.Williams, Sam. Free as in Freedom: Richard Stallman’s Crusade forFree Software. Sebastapol, Calif.: O’Reilly Media, 2002.standards in computingOne hallmark of the maturity of a technology is the developmentof a variety of kinds of standards that are acceptedby a majority of practitioners. There are several reasonswhy standards develop.Marketplace StandardsIn many cases, a particular product gains a prominentposition in an emerging market, and would-be competitorsadopt its interface and specifications. For example,the parallel port printer interface (and plug) developedby Centronics for its printers was adopted by virtually allprinter manufacturers. Since it would be impracticable forcomputer manufacturers to provide many different parallelconnectors on their machines, there was a clear marketadvantage in setting a standard. When a particular product(Centronics in this case) becomes that standard, it is mainlya matter of timing.Once a marketplace standard is established, manufacturersand consumers will generally not want products that areincompatible with it. When the IBM PC and its ISA expansioncard became the standard followed by many “clone”manufacturers, IBM discovered that even Big Blue floutedthe standard at its peril. When IBM came out with its MCA(Microchannel Architecture) in the late 1980s, the newmachines, although possessing some technical advances,did not sell as well as expected. Most people stayed withthe existing IBM standard and built upwardly compatiblemachines upon it.Official StandardsSome standards are developed by official bodies. For example,the International Standards Organization (ISO) has anelaborate formal process where panels of experts developstandards for a huge variety of technologies, including manyrelating to computing. In an increasingly global economy,international standards allow equipment (or software) fromone country to be used with that from another. For example,credit cards, phone cards, and “smart cards” around theworld have a common format established by ISO standards.(Standards specific to electrical and electronic engineeringare developed by a similar body, the International ElectrotechnicalCommission, or IEC.) Standards that have becomewidely accepted but are not yet official ISO standards takethe form of Publicly Available Specifications, or PAS. Governmentcontracts often specify ISO standards as well as avariety of other standards developed by various governmentagencies. The ISO 9001 standards apply specifically to computersystems, software, and its development.Evolution of StandardsThe extent of standardization within the broad informationtechnology (IT) industry varies widely among applications.Generally, things that have been established for a long time(meaning, in computing terms, a couple decades or so) arelikely to be well standardized. An example is the standardsfor character sets.For areas in which new applications are emerging, practitionerstend to have less interest (or patience) with the idea ofstandards. For example, the World Wide Web is still relativelynew, and standards for the operation of Web sites are emergingonly slowly. In this case, it is mainly concern about suchmatters as privacy protection that has encouraged the adoptionof standards for matters such as the secure transmissionof credit card information on-line or privacy policies regardingthe use of information obtained from Web users. Thepotential threat of government regulation often encouragesthe development of marketplace standards as an alternative.Technical societies such as the Institute for Electricaland Electronic Engineering (IEEE) and the World WideWeb Consortium are an important forum for the discussionand development of standards.Further ReadingDargan, P. A. Open Systems and Standards for Software ProductDevelopment. Norwood, Mass.: Artech House, 2005.Hoyle, David. ISO 9000 Quality Systems Handbook. 2nd. ed. Burlington,Mass.: Butterworth-Heinemann, 2006.“ISO IEC 90003 2004 Software Standard Translated into PlainEnglish.” Paxiom Research Group. Available online. URL:http://www.praxiom.com/iso-90003.htm. Accessed August22, 2007.Lund, Susan K., and John W. Walz. Practical Support for ISO 9001Software Project Documentation: Using IEEE Software EngineeringStandards. New York: Wiley, 2006.statistics and computingThe application of computing technology to the collectionand analysis of statistics is as old as computing itself. Indeed,

458 Stoll, CliffordCharles Babbage was an early proponent of the collection ofsocial and economic statistics in order to understand howsociety was being changed by the Industrial Revolution inthe early 19th century. By the end of that century, HermanHollerith had come to the rescue of the U.S. Census Bureauby providing his card tabulation machines for the 1890 Census.(See Babbage, Charles and Hollerith, Herman.)In the era of the mainframe, performing statisticalanalysis with a computer generally required writing a customizedprogram (although the development of FORTRANaround 1960 gradually led the accumulation of an extensivelibrary of subroutines that could be employed to performstatistical functions). Programs generally run in a batchmode, with data supplied from punched cards or tape.When the personal computer arrived, it wasn’t yet powerfulenough for much statistical work, although a programsuch as VisiCalc (see spreadsheet) could be used for simpleoperations. Gradually, spreadsheets grew more powerful,but statisticians truly rejoiced when software packagesspecifically designed for statistical work began to appear.Today there are hundreds of statistical packages available,of which the best known one for personal computersis SPSS. Most packages can be used to perform the standardforms of statistical analysis, including analysis of variance,regression analysis, discrete data analysis, time seriesanalysis, and cluster analysis. There are also packages forspecialized applications. Moving in the direction of greatergenerality, mathematical software such as Mathematica andMATLAB can also be used for statistical applications (seemathematics software). This category of software experiencessteady growth because the ability to analyze dataquickly and interactively is increasingly important given thegrowing pace of human activity, whether one is confrontedwith a rapidly spreading disease or a volatile economy.Other areas related to statistical computing include theextraction of useful correlations from existing data bases(see data mining) and the development of dynamic modelsbased on probability and statistics (see simulation).Further ReadingAmerican Statistical Association. Available online. URL: http://www.amstat.org. Accessed August 22, 2007.Givens, Geof H., and Jennifer A. Hoeting. Computational Statistics.New York: Wiley-Interscience, 2005.Griffith, Arthur. SPSS for Dummies. Hoboken, N.J.: Wiley, 2007.Linnemann, Jim. “Statistical Software Resources on the Web.”Available online. URL: http://www.pa.msu.edu/people/linnemann/stat_resources.html. Accessed August 22, 2007.McKenzie, John, and Robert Goldman, Jr. The Student Guide toMINITAB Release 14 + MINITAB Student Release 14. UpperSaddle River, N.J.: Addison-Wesley, 2004.Stoll, Clifford(1950– )AmericanAstrophysicist, Computer CriticUntil he became famous for tracking down a computer hacker,Clifford Stoll, born on June 4, 1950, in Buffalo, New York, wasan astronomer who had received his Ph.D. from the Universityof Arizona in 1980. (In the 1960s and 1970s Stoll had workedas an engineer at a public radio station in Buffalo.)In 1986, while working at the Lawrence Berkeley Laboratoryas a system administrator, Stoll was asked to track downa 75-cent accounting discrepancy. As he delved into computerfiles, Stoll discovered that an unknown hacker had penetratedsupposedly secure systems housing secret data relating to militarytechnology. Alarmed, Stoll and his colleagues decidedagainst immediately shutting down the intruder’s accounts.Instead, they painstakingly traced him, and discovered aneven more alarming possibility: that he was using the lab’scomputers to reach other computers operated by the militaryand defense contractors. Despite being virtually ignored whenreporting his findings to the FBI, Stoll and his impromptuteam soldiered on, even planting false data to keep the intruder’sinterest while continuing to trace his movements. FinallyStoll was able to get the attention of federal authorities. Theintrusion was traced to a West German hacker spy ring thatwas selling secrets to the Soviet KGB.Stoll’s book Cuckoo’s Egg recounted this adventure invivid, accessible terms, and made the New York Times bestsellerlist for 16 weeks in 1990. For many readers, this wastheir first introduction to the vulnerabilities of computersystems.Cyber-CriticIn writing and lectures, Stoll is engaging if sometimes a bitfrenetic. He soon turned his iconoclastic attitude towardcomputers themselves, warning about the dangers of overrelianceon them. Stoll’s books Silicon Snake Oil and HighTech Heretic particularly target the use of computers in education.Stoll believes that the technology has been embracedas a panacea for the endemic problem of underperformingschools. However, Stoll notes that the technology is oftenused for superficial purposes, with little attention to readingand writing skills, while the needs of teachers and studentsand their vital relationship remain neglected. In turn,advocates of computers in education have criticized Stoll asbeing superficial and lacking understanding of what goodsoftware can really do (see computers and education).In more recent years Stoll has devoted more time to hisfirst love, astronomy. He also has an unusual hobby: makingone-sided Klein bottles.Further ReadingStoll, Clifford. The Cuckoo’s Egg: Tracking a Spy through the Maze ofComputer Espionage. New York: Doubleday, 1989.———. High-Tech Heretic: Why Computers Don’t Belong in the Classroom,and Other Reflections by a Computer Contrarian. NewYork: Doubleday, 1999.———. Silicon Snake Oil: Second Thoughts on the Information Highway.New York: Doubleday, 1995.“When Slide Rules Ruled.” Scientific American, May 2006, pp. 80–87.streamingWeb users increasingly have access to such content as newsbroadcasts, songs, and even full-length videos. The problem

Stroustrup, Bjarne 459is that the user must receive the content in real time at asteady pace, not in sputters or jerks. However, factors suchas load on the Web server and network congestion betweenthe server and user can cause delays in transmission. Oneway to reduce the problem would be to compress the data(see data compression). However, excessive compressionwould compromise audio or picture quality to an unacceptableextent. Fortunately, a technology called streamingoffers a way to smooth out the transmission of largeamounts audio or video content (see also multimedia).When a user clicks on an audio or video link, the playersoftware (or Web browser plug-in) is loaded and the transmissionbegins. Typically, the player stores a few secondsof the transmission (see buffering), so any momentarydelays in the transmission of data packets will not appearas the data starts to play. Assuming the rate of transmissionremains sufficient, enough data remains in the bufferso that data can be “fed” to the playing software at a steadypace. If, however, there is too much delay due to networkcongestion, the playback will pause while the player refillsits buffer.The most popular media players for PCs (such asWinAmp, RealPlayer, and Windows Media Player) providefor streaming data. Despite streaming, connections of fewerthan about 56 kbps are likely to result in occasional interruptionof content. Together with the use of streaming, themove to faster cable or DSL connections (see broadband)is improving the multimedia experience for Web users. Inturn, the ability to easily access video online has fueledvideo-sharing services (see user-created content and You-Tube). Meanwhile, the growing use of fiber and other highspeedconnections into homes is beginning to make “ondemand” streaming video services and IPTV (televisionprogramming delivered via the Internet) competitive withexisting cable and satellite systems.Further ReadingFollansbee, Joe. Get Streaming!: Quick Steps to Delivering Audio andVideo Online. Burlington, Mass.: Focal Press, 2004.“Introduction: How to Create Streaming Video.” Media College.Available online. URL: http://www.mediacollege.com/video/streaming/overview.html. Accessed August 22, 2007.IPTV news. Available online. URL: http://www.iptvnews.net/.Accessed August 22, 2007.Mack, Steve. Streaming Media Bible. New York: Wiley, 2002.Stolarz, Damien. Mastering Internet Video: A Guide to Streaming andOn-Demand Video. Upper Saddle River, N.J.: Addison-WesleyProfessional, 2004.Bjarne Stroustrup created C++, an object-oriented successorto the popular C language that has now largely supplantedthe original language.Stroustrup was born on December 30, 1950, in Aarhus,Denmark. As a student at the University of Aarhus his interestswere far from limited to computing (indeed, he foundprogramming classes to be rather dull). However, unlike literatureand philosophy, programming did offer a practicaljob skill, and Stroustrup began to do contract programmingfor Burroughs, an American mainframe computer company.To do this work, Stroustrup had to pay attention to both theneeds of application users and the limitations of the machine,on which programs had to be written in assembly languageto take optimal advantage of the memory available.By the time Stroustrup received his master’s degree incomputer science from the University of Aarhus, he was anexperienced programmer, but he soon turned toward thefrontiers of computer science. He became interested in distributedcomputing (writing programs that run on multiplecomputers at the same time) and developed such programsat the Computing Laboratory at Cambridge University inEngland, where he earned his Ph.D. in 1979.The 1970s was an important decade in computing. Itsaw the rise of a more methodical approach to programmingand programming languages (see structured programming).It also saw the development of a powerful andversatile new computing environment: the UNIX operatingsystem and C programming language developed by DennisRitchie (see Ritchie, Dennis) and Ken Thompson and BellLaboratories. Soon after getting his doctorate, Stroustrupmoved to Bell Labs, where he became part of that effort.As Stroustrup continued to work on distributed computing,he decided that he needed a language that was betterthan C at working with the various modules runningon the different computers. He studied an early object-orientedlanguage (see object-oriented programming andSimula). Simula had a number of key concepts includingthe organization of a program into classes, entities thatcombined data structures and associated capabilities (methods).Classes and the objects created from them offered abetter way to organize large programs, and was particularlyStroustrup, Bjarne(1950– )DanishComputer ScientistIn the 1980s Bjarne Stroustrup created the object-oriented C++ languagethat became the most popular language for general applicationsprogramming. (Bjarne Stroustrup)

460 structured programmingsuited for distributed computing and parallel programmingwhere there were many separate entities running at thesame time.However, Simula was fairly obscure, and it was unlikelythat the large community of systems programmers whowere using C would switch to a totally different language.Instead, starting in the early 1980s, Stroustrup decided toadd object-oriented features (such as classes with memberfunctions, user-defined operators, and inheritance) to C. Atfirst he gave the language the rather unwieldy name of “Cwith Classes.” However, in 1985 he changed the name toC++. (The ++ is a reference to an operator in C that adds oneto its operand, thus C++ is “C with added features.”)At first some critics criticized C++ for retaining most ofthe non-object oriented features of C (unlike pure objectlanguages such as Smalltalk), while others complainedthat the overhead required in processing classes made C++slower than C. During the 1990s, however, C++ becameincreasingly popular, aided by its relatively smooth learningcurve for C programmers and the development or moreefficient compilers. C++ is now the most widely used generalpurpose computer language.Stroustrup has been honored for his contributions tocomputer science. In 1993 he received the ACM Grace HopperAward for his work on C++, and became an AT&TFellow. After leaving AT&T Stroustrup became a professorholding the College of Engineering Chair in Computer Scienceat Texas A&M University. In 2004 Stroustrup receivedthe IEEE Computer Society Computer EntrepreneurAward, and in 2005 the William Procter Prize for ScientificAchievement.Further ReadingBjarne Stroustrup [home page]. Available online. URL: http://parasol.tamu.edu/people/bs/.Accessed August 22, 2007.Dolya, Aleksey. “Interview with Bjarne Stroustrup.” Linux Journal,August 28, 2003. Available online. URL: http://www.linuxjournal.com/article/7099. Accessed August 22, 2007.Pontin, Jason. “The Problem with Programming: Bjarne Stroustrup,the Inventor of the C++ Programming Language, DefendsHis Legacy and Examines What’s Wrong with Most SoftwareCode.” Technology Review, November 28, 2006. Availableonline. URL: http://www.techreview.com/Infotech/17831/page1/. Accessed August 22, 2007.Stroustrup, Bjarne. The C++ Programming Language. Special 3rded. Upper Saddle River, N.J.: Addison-Wesley, 1997.———. The Design and Evolution of C++. Reading, Mass.: Addison-Wesley, 1995.structured programmingAs programs grew longer and more complex during the1960s, computer scientists began to pay more attention tothe ways in which programs were organized. Most programminglanguages had a statement called “GOTO” or itsequivalent. This statement transfers control to some arbitraryother point in the program, as identified by a label orline number.In 1968, computer scientist Edsger Dijkstra (see dijkstra,edsger) sent a letter to the editor of the Proceedings ofthe ACM with the title “GO TO Statement Considered Harmful.”In it he pointed out that the more such jumps programsmade from place to place, the harder it was for someone tounderstand the logic of the program’s operation.The following year, Dijkstra introduced the term structuredprogramming to refer to a set of principles for writingwell-organized programs that could be more easily shownto be correct. One of these principles is statements such asIf . . . Then . . . Else be used to organize a choice betweentwo or more alternatives (see branching statements) andthat statements such as While be used to control repetitionor iteration of a statement (see loop).Other computer scientists added further principles, suchas modularization (breaking down a program into separateprocedures, such as for data input, different stages of processing,and output or printing). Modularization makes iteasier to figure out which part of a program may be causing aproblem, and to fix part of a problem without affecting otherparts. A related principle, information hiding, keeps the dataused by a procedure “hidden” in that procedure so that itcan’t be changed from some other part of the program.Structured programming also encourages stepwiserefinement, a program design process described by NiklausWirth, creator of Pascal. This is a top-down approach inwhich the stages of processing are first described in highlevelterms (see also pseudocode), and then graduallyfleshed out in their details, much like the writing of anoutline for a book.The principles of structured programming were soonembodied in a new generation of programming languages(see Algol, Pascal, and c). Although use of well-structuredlanguage didn’t guarantee good structured programmingpractice, it at least made the tools available.The ideas of structured programming form a solid basisfor programming style today. They have been supplementedrather than replaced by a new paradigm developed in the1970s and 1980s (see object-oriented programming).Further ReadingDhal, Ole-Johan, Edsger W. Dijkstra, and C. A. R. Hoare, eds.Structured Programming. New York: Academic Press, 1972.Dijkstra, Edsger. A Discipline of Programming. Englewood Cliffs,N.J.: Prentice Hall, 1976.———. “Go To Statement Considered Harmful.” Communicationsof the ACM 11, no. 3 (1968): 147–148.———. “Notes on Structured Programming.” Available online. URL:http://www.cs.utexas.edu/users/EWD/ewd02xx/EWD249.PDF.Accessed August 22, 2007.Orr, Kenneth T. Structured Systems Development. New York: YourdonPress, 1977.Sun MicrosystemsFounded in 1982, Sun Microsystems (NASDAQ symbol:JAVA) has played an important role in the developmentof computer workstations and servers, UNIX-based operatingsystems, and the Java programming language (see Java,unix, and workstation).During the 1980s, Sun was known mainly for its workstationsfor programmers and graphics professionals, runningon its own SPARC series microprocessors. However,

supercomputer 461by the 1990s the growing power of regular desktop PCs wasreducing the need for special-purpose workstations. As theWeb grew starting in the 1990s, Sun’s line of multiprocessingWeb servers became quite successful, though the “dotbust”of the early 2000s cut revenues.One of Sun’s founders was a key developer of UNIXsoftware (see Joy, Bill). Sun developed its own version ofUNIX (SunOS) for its workstations in the 1980s, and thenjoined with AT&T to develop the widely used UNIX SystemV Release 4, which in turn became the basis for Sun’s newoperating system, Solaris. (Sun has also supported the useof Linux on its hardware.)Sun’s biggest impact on software development, however,has been its development of the Java language and platformsince the early 1990s. Although newer languages such asPython, PHP, and Ruby have come along to challenge it,Java, with its ability to run via “virtual machines” on allmajor platforms, is widely used and has a rich set of libraryroutines and programming frameworks.Scott McNealy, one of the company’s founders, remainsits chairman. Sun had $13.87 billion revenue in 2007 ($473million net income), and employs about 36,400 people.Further ReadingBoyous, Jon. “Java Technology: The Early Years.” Sun DeveloperNetwork. Available online. URL: http://java.sun.com/features/1998/05/birthday.html. Accessed November 18, 2007.Southwick, Karen. High Noon: The Inside Story of Scott McNealyand the Rise of Sun Microsystems. New York: Wiley, 1999.Sun Microsystems. Available online. URL: http://www.sun.com/.Accessed November 18, 2007.Sun Multimedia Center [videos]. Available online. URL: http://sunfeedroom.sun.com. Accessed November 18, 2007.Sun Wikis. Available online. URL: http://wikis.sun.com. AccessedNovember 18, 2007.supercomputerThe term supercomputer is not really an absolute termdescribing a unique type of computer. Rather, it has beenused through successive generations of computer designto describe the fastest, most powerful computers availableat a given time. However, what makes these machines thefastest is usually their adoption of a new technology orcomputer architecture that later finds its way into standardcomputers.The first supercomputer is generally considered to bethe Control Data CDC 6600, designed by Seymour Crayin 1964. The speed of this machine came from its use ofthe new, faster silicon (rather than germanium) transistorsand its ability to run at a clock speed of 10 MHz (a speedthat would be achieved by personal computers by the mid-1980s). Even with transistors, these machines generatedso much heat that they had to be cooled by a Freon-basedrefrigeration system.Cray then left CDC to form Cray Research. He designedthe Cray 1 in 1976, the first of a highly successful seriesof supercomputers. The Cray 1 took advantage of a newtechnology, integrated circuits, and new architecture: vectorprocessing, in which a single instruction can be appliedA Cray 190 A supercomputer. Seymour Cray’s leading-edgemachines defined supercomputing for many years. (NASA photo)to an entire series (or array) of numbers simultaneously.This innovation marked the use of parallel processing asone of the distinguishing features of supercomputers. Themachine’s monolithic appearance gave it a definite air ofscience fiction, and the first one built was installed at thesecretive Los Alamos National Laboratory.The next generation, the Cray X-MP, carried parallelismfurther by incorporating multiple processors (the successor,Cray Y-MP, had 8 processors, which together could performa billion floating-point operations per second [1 gigaflop]).Soon Cray no longer had the supercomputer field toitself, and other companies (particularly the Japanese manufacturersNEC and Fujitsu) entered the market. The numberof processors in supercomputers increased to as manyas 1,024 (in the 1998 Cray SV1), which can exceed 1 trillionfloating-point operations per second (1 teraflop).Meanwhile, processors for desktop computers (such asthe Intel Pentium) also continued to increase in power, andit became possible to build supercomputers by combininglarge numbers of these readily available (and relatively lowcost)processors.The ultimate in multiprocessing is the series of ConnectionMachines built by Thinking Machines Inc. (TMI)and designed by Daniel Hillis. These machines have upto 65,000 very simple processors that run simultaneously,and can form connections dynamically, somewhat likethe process in the human brain. These “massively parallel”machines are thus attractive for artificial intelligenceresearch. It is also possible to achieve supercomputerlikepower by having many computers on a network divide thework of, for example, cracking a code or analyzing radiotelescope data for signs of intelligent signals.Programs for supercomputers must be written usingspecial languages (or libraries for standard languages) thatare designed to provide for many processes to run at thesame time and that allow for communication and coordinationbetween processing (see multiprocessing).

462 supply chain managementApplicationsSupercomputers are always more expensive and somewhatless reliable than standard computers, so they are used onlywhen necessary. As the power of standard computers continuesto grow, applications that formerly required a multimillion-dollarsupercomputer can now run on a desktopworkstation (a good example is the creation of detailed 3Dgraphics).On the other hand, there are always applications that willsoak up whatever computing power can be brought to bear onthem. These include analysis of new aircraft designs, weatherand climate models, the study of nuclear reactions, and thecreation of models for the synthesis of proteins. The neverendingbattle of organizations such as the National SecurityAgency (NSA) to monitor worldwide communications andcrack ever-tougher encryption also demands the fastest availablesupercomputers (see quantum computing).ArchitectureThe fastest “conventional” supercomputers as of 2007 wereIBM’s Blue Gene series, expected to reach a speed of 3 pflop(peta, or quadrillion floating point operations per second).Machines of this magnitude are usually destined for institutionssuch as the Los Alamos National Laboratory (see governmentfunding of computer research).However, for many applications it may be more cost-effectiveto build systems with numerous coordinated processors(a sort of successor to the 1980s Connection Machine).For example, the Beowulf architecture involves “clusters” ofordinary PCs coordinated by software running on UNIX orLinux. The use of free software and commodity PCs canmake this approach attractive, though application softwarestill has to be rewritten to run on the distributed processors.Recently a new resource for parallel supercomputingcame from an unlikely place: the new generation of cellprocessors found in game consoles such as the Sony Playstation3. This architecture features tight integration of acentral “power processor element” with multiple “synergisticprocessing elements.” IBM is currently developing a newsupercomputer called Roadrunner that will include 16,000conventional (Opteron) and 16,000 cell processors, and isexpected to reach a speed of 1 pflop.Finally, an ad hoc “supercomputer” can be createdalmost for free, using software that parcels out calculationtasks to thousands of computers participating via theInternet, as with SETI@Home (searching for extraterrestrialradio signals) and Folding@Home (for protein-foldinganalysis). (See cooperative processing.)Further Reading“Blue Gene.” IBM. Available online. URL: http://www-03.ibm.com/servers/deepcomputing/bluegene.html. Accessed August22, 2007.Gropp, William, Ewing Lusk, and Thomas Sterling. Beowulf ClusterComputing with Linux. 2nd ed. Cambridge, Mass.: MITPress, 2003.“IBM to Build World’s First Cell Broadband Engine Based Supercomputer.”September 6, 2006. Available online. URL: http://www-03.ibm.com/press/us/en/pressrelease/20210.wss. AccessedAugust 22, 2007.Murray, C. J. The Supermen: The Story of Seymour Cray and theTechnical Wizards behind the Supercomputer. New York: Wiley,1995.National Center for Supercomputing Applications (NCSA). Availableonline. URL: http://www.ncsa.uiuc.edu/. Accessed August22, 2007.National Research Council. Getting Up to Speed: The Future ofSupercomputing. Washington, D.C.: National Academies Press,2005.Scientific American. Understanding Supercomputing. New York:Warner Books, 2002.Top 500 Supercomputer Sites. Available online. URL: http://www.top500.org/. Accessed August 22, 2007.supply chain managementFew consumers are aware of the complexity of the networkof organizations, transportation and storage facilities, andinformation processing facilities that are needed to turnraw materials into finished products. The term supply chainmanagement was developed in the 1980s to refer to the systematicefforts to improve the efficiency and reliability ofthis vital business activity. Although the details will varywith the industry, a supply chain can include the followingactivities:• obtaining the raw materials or components needed forthe product• manufacturing finished products• marketing the product• distributing the product to retailers or other outlets• servicing the product and supporting customers• (increasingly) providing for the ultimate recycling ordisposal of the productAt all stages of the chain, planners must take into considerationwhat location for operations is most advantageousand how materials will be transported, warehoused,and tracked. Potential suppliers must be evaluated for costand reliability. Schedules must be monitored. Finally, everythingshould be part of a comprehensive plan that spells outthe objectives and how they will be measured.SoftwareOf course such a complex process involving a great deal ofinformation, monitoring, and decision making is ripe forsoftware assistance. Some companies offer comprehensivesolutions (see, for example, sap), but they must still beadapted to the needs of a particular industry and manufacturer.Software must be interfaced and integrated withexisting databases, management information systems, andother software. Nevertheless, in a very competitive worldmarket, enterprises have little choice but to develop aneffective way to manage and optimize their supply chains.Further ReadingBlanchard, David. Supply Chain Management Best Practices. Hoboken,N.J.: Wiley, 2007.Chopra, Sunil, and Peter Meindl. Supply Chain Management. 3rded. Upper Saddle River, N.J.: Prentice Hall, 2006.

Sutherland, Ivan Edward 463Simchi, David, Philip Kaminsky, and Edith Simchi-Levi. Designingand Managing the Supply Chain. 2nd ed. New York: McGraw-Hill, 2002.Worthen, Ben. “ABC: An Introduction to Supply Chain Management.”CIO. Available online. URL: http://www.cio.com/article/40940. Accessed November 18, 2007.Sutherland, Ivan Edward(1938– )AmericanComputer ScientistToday it is hard to think about computers without interactivegraphics displays. Whether one is flying a simulated747 jet, retouching a photo, or just moving files from onefolder to another, everything is shown on the screen ingraphical form. For the first two decades of the computer’shistory, however, computers lived in a text-only world,except for a few experimental military systems. Duringthe 1960s and 1970s Ivan Sutherland would almost single-handedlycreate the framework for modern computergraphics while designing Sketchpad, the first computerdrawing program.Sutherland was born on May 16, 1938, in Hastings,Nebraska, but the family later moved to Scarsdale, NewYork. His father was a civil engineer, and as a young boySutherland was fascinated by the drawing and surveyinginstruments his father used. When he was about 12,Sutherland and his brother Bert got a job working fora pioneer computer scientist named Edmund Berkeley.Berkeley gave Sutherland the opportunity to play with“Simon,” a suitcase-sized electromechanical computer thatcould add numbers as long as the total did not exceed 30.Simon eventually rewired the machine so it could dividenumbers as well.Sutherland first attended Carnegie Mellon University,where he received a B.S. in electrical engineering in 1959.The following year he earned an M.A. from the CaliforniaInstitute of Technology (Cal Tech). He then went to MIT todo his doctoral work under Claude Shannon at the LincolnLaboratory (see Shannon, Claude).At MIT Sutherland was able to work with the TX-2, anadvanced (and very large) transistorized computer that wasa harbinger of the minicomputers that would become prevalentlater in the decade. Unlike the older mainframes, theTX-2 had a graphics display and could accept input from alight pen as well as switches that could serve something likethe functions that mouse buttons do today. The machinealso had 70,000 36-bit words of memory, an amount thatwould not be achieved by personal computers until the1980s. Having this much memory made it possible to storethe pixel information for detailed graphics objects.Having access to this interactive machine gave Sutherlandthe idea for his doctoral dissertation (submitted in1963). He developed a program called Sketchpad, whichrequired that he develop algorithms for drawing realisticobjects by plotting pixels and polygons as well as scalingobjects in relation to the viewer’s position. Sutherland’sSketchpad could even automatically “snap” lines into placeas the user drew on the screen with the light pen. Besidesdrawing, Sketchpad demonstrated the beginnings of the“graphical user interface” that would be further developedby researchers at Xerox PARC in the 1970s and would reachthe consumer in the 1980s.After demonstrating Sktechpad in 1963 and receivinghis Ph.D. from MIT, Sutherland took on a quite differenttask. He became the director of the Information ProcessingTechniques Office (IPTO) of the Defense Department’sAdvanced Research Projects Agency (ARPA)—see Licklider,J. C. R. While continuing his research on graphicsSutherland thus also oversaw the work on computer timesharingand the networking research that would eventuallylead to the ARPANet and the Internet.In 1968 Sutherland and David Evans went to the Universityof Utah, where they established an InformationProcessing Technology Office (IPTO)–funded computergraphics research program. There, Sutherland’s groupbrought computer graphics to a new level of realism. Forexample, they developed the ability to place objects in frontof other objects, which required intensive calculations todetermine what was obscured. They also developed an ideasuggested by Evans called incremental computing. Instead ofdrawing each pixel in isolation, they used information frompreviously drawn pixels to calculate new ones, considerablyspeeding up the rendering of graphics. The results began toapproach the realism of a photograph. (The two researchersalso founded a commercial enterprise, Evans and Sutherland,to exploit their graphics ideas. It became one of theleaders in the field.)In 1976 Sutherland left the University of Utah to serveas the chairman of the computer science department at CalTech. Working with a colleague, Carver Mead, Sutherlanddeveloped a systematic concept and curriculum for integratedcircuit design, which became the main specialty ofthe department. He would later point out that it was theimportant role that geometry played in laying out componentsand wires that had intrigued him the most.Sutherland left Caltech in 1980 and started a consultingand venture capital firm with Bob Sproull, whom he hadmet years earlier at Harvard. In 1990 Sun Microsystemsbought the company for its technical expertise, making itthe core of Sun Labs, where Sutherland continues to workas a Sun Microsystems Fellow and vice president. Sutherlandreceived the prestigious ACM Turing Award in 1988.Further Reading“An Evening with Ivan Sutherland: Research and Fun” [partialtranscript and online video]. Computer History Museum,October 19, 2005. Available online. URL: http://www.mprove.de/script/05/sutherland/index.html. Accessed November 18,2007.Frenkel, Karen A. “Ivan E. Sutherland, 1988 A. M. Turing AwardRecipient” [Interview]. Communications of the ACM 32 (June1989): 711.Sutherland, Ivan E. “Sketchpad—A Man-Machine Graphical CommunicationSystem.” University of Cambridge ComputerLaboratory. Technical Report No. 574 [with new preface],September 2003. Available online. URL: http://www.cl.cam.ac.uk/TechReports/UCAM-CL-TR-574.pdf. Accessed November18, 2007.

464 system administratorsystem administratorA system administrator is the person responsible for managingthe operations of a computer facility to ensure that itruns properly, meets user needs, and protects the integrityof users’ data. Such facilities range from offices with just afew users to large campus or corporate facilities that may beserved by a large staff of administrators.The system administrator’s responsibilities often include:• setting up accounts for new users• allocating computing resources (such as server space)among users• configuring the file, database, or local area network(LAN) servers• installing new or upgraded software on users’ workstations• keeping up with new versions of the operating systemand networking software• using various tools to monitor the performance ofthe system and to identify potential problems such asdevice “bottlenecks” or a shortage of disk space• ensuring that regular backups are made• configuring network services such as e-mail, Internetaccess, and the intranet (local TCP/IP network)• using tools such as firewalls and virus scanners toprotect the system from viruses, hacker attacks, andother security threats (see also computer crime andsecurity)• providing user orientation and training• creating and documenting policies and proceduresSystem administrators often write scripts to automate manyof the above tasks (see scripting languages). Because ofthe complexity of modern computing environments, anadministrator usually specializes in a particular operatingsystem such as UNIX or Windows.A good system administrator needs not only technicalunderstanding of the many components of the system,but also the ability to communicate well with users—good“people skills.” Larger organizations are more likely to haveseparate network and database administrators, while theadministrator of a small facility must be a jack (or jill) of alltrades.Further ReadingCulp, Brian. Windows Vista Administration: The Definitive Guide.Sebastapol, Calif.: O’Reilly Media, 2007.Frisch, Æleen. Essential System Administration. 3rd ed. Sebastapol,Calif.: O’Reilly Media, 2002.———. Essential Windows NT System Administration. Sebastapol,Calif.: O’Reilly Media, 1998.Information for Linux System Administration (Librenix). Availableonline. URL: http://librenix.com/. Accessed August 22, 2007.Limoncelli, Thomas A., Christina J. Horgan, and Strata R. Chalup.The Practice of System and Network Administration. 2nd ed.Upper Saddle River, N.J.: Addison-Wesley Professional, 2007.Nemeth, Evi, Garth Snyder, and Trent R. Hein. Linux SystemAdministration Handbook. 2nd ed. Upper Saddle River, N.J.:Prentice Hall PTR, 2006.systems analystThe systems analyst serves as the bridge between the needsof the user and the capabilities of the computer system. Thesystems analyst goes into action when users request thatsome new application or function be provided (usually in acorporate computing environment).The first step is to define the user’s requirements and toprepare precise specifications for the program. In doing so,the systems analyst is aided by methodologies developedby computer scientists over the last several decades (seestructured programming and object-oriented programming).Often flowcharts or other aids are used to helpvisualize the operation of the program (see also case).After communicating with the user, the systems analystmust then communicate with the programmers, helpingthem understand what is needed and reviewing their workas they begin to design the program. Although the systemsanalyst may do little actual programming, he or she must befamiliar with programming tools and practices. This maymake it possible to suggest existing software or componentsthat could be adapted instead of undertaking the cost andtime involved with creating a new program. As a programis developed, systems analysts are often responsible fordesigning tests to ensure that the software works properly(see quality assurance, software).Depending on the organizational structure, all or part ofthe analysis function may be included in the job description“programmer-analyst” or included as part of the duties of asenior software engineer or manager of program development.Experienced systems analysts are likely to be calledupon to participate in the evaluation of possible investmentsin new software or hardware, and other aspects oflong-term planning for computing facilities.Further ReadingSatzinger, John W., Robert B. Jackson, and Stephen D. Burd. SystemsAnalysis & Design in a Changing World. 4th ed. Boston:Course Technology, 2006.Shelly, Gary B., Thomas J. Cashman, and Harry J. Rosenblatt. SystemsAnalysis & Design. 7th ed. Boston: Course Technology,2007.Systems Analysis Web Sites. Available online. URL: http://www.umsl.edu/~sauterv/analysis/analysis_links.html. AccessedAugust 22, 2007.Whitten, Jeffrey L., and Lonnie D. Bentley. Introduction to SystemsAnalysis & Design. New York: McGraw-Hill/Irwin, 2007.———. Systems Analysis & Design Methods. 7th ed. New York:McGraw-Hill/Irwin, 2005.systems programmingApplications programmers write programs to help userswork better, while systems programmers write programsto help the computer itself work better (see operating system).Systems programmers generally work for companiesin the computer industry that develop operating systems,

systems programming 465network facilities, program language compilers and othersoftware development tools, utilities, and device drivers.However, systems programmers can also work for applicationsdevelopers to help them interface their programs tothe operating system or to devices (see device driver andapplications programming interface).Modern operating systems are highly complex, so systemsprogrammers tend to specialize in particular areas.These might include device drivers, software developmenttools, program language libraries, applications programminginterfaces (APIs), and utilities for monitoring systemconditions and resources. Systems programmers developthe infrastructure needed for networking, as well as multiple-processorcomputers and distributed computing systems.Systems programmers also play a key role when anapplication program must be “ported” to a different platformor simply modified to run under a new version of theoperating system.Generally, an application programmer works at a fairlyhigh level, using language functions and APIs to have theprogram ask the operating system for services such as loadingor saving files, printing, and so on. The systems programmer,on the other hand, must be concerned with theinternal architecture of the system (such as the buffers allocatedto hold various kinds of temporary data) and withhow commands are constructed for disks and other devices.Generally, the systems programmer must also have a morethorough knowledge of data structures and how they arephysically represented in the machine as well as the comparativeefficiency of various algorithms. Because it determineshow efficiently the system’s resources can be used,systems programming must often be “tight” and optimizedfor peak performance. Thus, although lower-level assemblylanguage is no longer used for much applications programming,it can still be found in systems programming.Further ReadingBeck, Leland L. System Software: An Introduction to Systems Programming.3rd ed. Reading, Mass.: Addison-Wesley, 1996.Hart, Johnson M. Windows System Programming. 3rd ed. UpperSaddle River, N.J.: Addison-Wesley Professional, 2004.Love, Robert. Linux System Programming. Sebastapol, Calif.:O’Reilly Media, 2007.Robbins, Kay A., and Steven Robbins. UNIX Systems Programming.Upper Saddle River, N.J.: Prentice Hall PTR, 2003.

Ttablet PCAs the name suggests, a tablet PC is a small computer aboutthe size of a notebook (not to be confused with a “notebookPC,” which is a small, light laptop). The user can write onthe screen with a stylus to take notes (for similar functionality,see graphics tablet), draw, and make selections withstylus or fingertip.If the user writes on the screen, software converts thewriting to the appropriate characters and stores them in afile (see handwriting recognition). As with some PDAs,there may also be a system of shorthand “gestures” that canbe used to write more quickly. Alternatively, the user cantype with stylus or fingertips on a “virtual keyboard” displayedon the screen (see touchscreen).A more versatile and natural interface is becoming available:“multitouch,” pioneered by the Apple iPhone andMicrosoft Surface, can recognize multiple motions andpressure points simultaneously. This allows the user to, forexample, flick the finger to “turn a page” or use a pinchingmotion to “pick up” an object.Applications for tablet PCs include many PDA-typeapplications (see personal information managementand pda), field note taking, inventory, and other tasks thatrequire a device that is not encumbering. Because of itscompactness, a tablet PC can also be a good reader for e-books (see e-books and digital libraries).Tablet PCs generally follow common specificationsdeveloped by Microsoft, and often use Windows XP TabletPC Edition or, later, Windows Vista, which has built-insupport for tablet PCs. These operating systems includesupport for sophisticated handwriting recognition thatcan be “trained” by the user and that can store handwritteninput in special data formats. Voice recognition isalso supported.A “convertible” tablet PC is a hybrid in which the tabletis attached to a base containing a keyboard. The display canbe used vertically (laptop style) or rotated and folded downover the keyboard for tablet use.Internet TabletsAn interesting variant is the Internet tablet, best known inNokia’s N-series. These are smaller and lighter than a tabletPC. The Nokia N810, for example, has a slide-out keyboardas well as a virtual screen keyboard. The most notablefeature is the Internet browser and related applications,such as e-mail and instant messaging, and built-in wirelessconnections (see bluetooth and wireless computing).Although there is no phone, Internet-based services such asSkype can be used to place calls, or a Bluetooth-equippedmobile phone. The Nokia series uses a variant of Linux andcan run a large variety of open-source applications.Further ReadingLinenberger, Michael. Seize the Work Day: Using the Tablet PC toTake Control of Your Work and Meeting Day. San Ramon, Calif.:New Academy Publishers, 2004.Stevenson, Nancy. Tablet PCs for Dummies. New York: Wiley, 2003.Tablet PC Review. Available online. URL: http://www.tabletpcreview.com/. Accessed November 19, 2007.“What Is a Tablet PC?” Microsoft, February 9, 2005. Availableonline. URL: http://www.microsoft.com/windowsxp/tabletpc/evaluation/about.mspx. Accessed November 19, 2007.466

tape drives 467tape drivesAnyone who has seen computers in old movies is familiarwith the row of large, freestanding tape cabinets with theirspinning reels of tape. The visual cue that the computerwas running consisted of the reels thrashing back and forthvigorously while rows of lights flashed on the computerconsole. Magnetic tape was indeed the mainstay for datastorage in most large computers (see mainframe) in the1950s through the 1970s.In early mainframes the main memory (correspondingto today’s RAM chips) consisted of “core”—thousands oftiny magnetized rings crisscrossed with wires by whichthey could be set or read. Because core memory was limitedto a few thousand bytes (kB), it was used only to holdthe program instructions (see punched cards and papertape) and to store temporary working data while the programwas running.The source data to be processed by the program wasread from a reel of tape on the drive. If the program updatedthe data (rather than just reporting on it), it would generallywrite a new tape with the revised data. In large facilities aperson called a tape librarian was in charge of keeping thereels of tape organized and providing them to the computeroperators as needed.OperationA mainframe tape drive had two reels, the supply reel andthe take-up reel. Because each reel had its own motor, theycould be spun at different speeds. This allowed a specifiedlength of tape to be suspended between the two reels,serving as sort of a buffer and allowing the take-up reel toaccelerate at the start of a read or write operation withoutdanger of breaking the tape. The “buffer” tape was actuallysuspended in a partial vacuum, which both kept thetape taut enough to prevent snarling and allowed for airpressure sensors to activate the appropriate motor whenthe amount of tape in the buffer went above or below presetpoints.Data was read or written by the read and write headsrespectively, in units called frames. In addition to the 1 or0 data bits, each frame included parity bits (see error correction).The frames were combined into blocks, with eachblock having a header in front of the data frames and one ormore frames of check (parity) bits following the data.The two predominant tape formats were the IBM format,which used variable-length data blocks (and thus could notbe rewritten) and the DEC format, which used fixed-lengthblocks, allowing data to be rewritten in place, albeit at somecost in speed and efficiency.During the 1960s, magnetic disks (see hard disk)increasingly came into use, and more of the temporary databeing used by programs began to be stored on disk ratherthan on tape. Eventually, tapes were relegated to storingvery large data sets or archiving old data.However, when the first desktop microcomputers (suchas the Apple II and Radio Shack TRS-80) came along inthe late 1970s and early 1980s, they, like the first mainframes,had very limited main memory and disk driveswere unavailable or expensive. As a result, programs (suchA NASA automated tape library. These facilities can store trillionsof bytes of data. (NASA Photo)as Bill Gates’s Microsoft Basic) often came on tape cassettes,and the computer included an interface allowing it tobe connected to an ordinary audio cassette recorder. However,this use of tapes was quite short-lived, and was soonreplaced by the floppy disk drive and later, hard drives andCD-ROM drives.Tapes as Backup DevicesBy the 1990s, PC users generally used tapes only for makingbackups. A typical backup tape drive uses DAT (digitalaudio tape) cartridges that hold from hundreds of megabytesto several gigabytes of data. Most drives use a rotatingassembly of four heads (two read and two write) that verifydata as it’s being written. As a backup medium, tape has alower cost per gigabyte than disk devices. It is easy to useand can be set up to run unattended (except for periodicallychanging cartridges).However, since tapes are written and read sequentially,they are not convenient for restoring selected files (seebackup and archive systems). Many smaller installationsnow prefer using a second (“mirror”) hard drive as backup,using disk arrays (see raid) or using recordable CDs oroptical drives for smaller amounts of data (see cd-rom anddvd-rom).Many large companies and government agencies havethousands of reels of tape stored away in their vaults sincethe 1960s, including data returned from early NASA spacemissions. As time passes, it becomes increasingly difficult toguarantee that this archived data can be successfully read.This is due both to gradual deterioration of the medium andthe older data formats becoming obsolete (see backup andarchive systems).Further ReadingBrain, Marshall. “How Tape Drives Work.” Available online. URL:http://electronics.howstuffworks.com/cassette.htm. AccessedAugust 22, 2007.

468 TclHaylor, Phil. Computer Storage: A Manager’s Guide. Victoria, B.C.,Canada: Trafford, 2005.Scapicchio, Mark. “How Tape Drives Work: Tape Backup Still aGood Option.” Smart Computing, October 2002, pp. 69–72.Available online. URL: http://www.smartcomputing.com/editorial/article.asp?article=articles/archive/r0608/13 r08/13r08.asp&guid=. Accessed August 22, 2007.White, Ron, and Timothy Edward Downs. How Computers Work.8th ed. Indianapolis: Que, 2005.TclDeveloped by John Ousterhout in 1988, Tcl (Tool commandlanguage) is used for scripting, prototyping, testing interfaces,and embedding in applications (see scripting languages).Tcl has an unusually simple and consistent syntax. Ascript is simply a series of commands (either built in or userdefined) and their arguments (parameters). A commanditself can be an argument to another command, creating theequivalent of a function call in other languages.For example, setting the value of a variable uses the setcommand:set total 0The value of the variable can now be referenced as$total.Control structures are simply commands that run othercommands. A while loop, for example, consists of a commandor expression that performs a comparison, followedby a series of commands to be executed each time it returns“true”:while { MoreInFile } {GetDataDisplayData}In practice, many of the commands used are utilitiesfrom the operating system, usually UNIX or Linux. Tclalso includes a number of useful data structures such asassociative arrays, which consist of pairs of data itemssuch as:set abbr (California)Extensions and ApplicationsTcl includes a number of extensions that, for example,provide access to popular database formats such as MySQLand can interface with other programming languages suchas C++ and Java. The most widely used extension is Tk,which provides a library for creating user interfaces for avariety of operating systems and languages such as Perl,Python, and Ruby.Tcl has been described as a “glue” to connect existingapplications. It is relatively easy to write and test a scriptinteractively (often at the command line), and then insert itinto the code of an application. When the application runs,the Tcl interpreter runs the script, whose output can thenbe used by the main application (see interpreter).CAFurther ReadingFoster-Johnson, Eric. Graphical Applications with Tcl & Tk. 2nd ed.New York: Hungry Minds, 1997.Wall, Kurt. Tcl and Tk Programming for the Absolute Beginner. Boston:Course Technology, 2007.Welch, Brent B., and Ken Jones. Practical Programming in Tcl andTk. 4th ed. Upper Saddle River, N.J.: Prentice Hall, 2003.TCP/IPContrary to popular perception, the Internet is not e-mail,chat rooms, or even the World Wide Web. It is a system bywhich computers connected to various kinds of networksand with different kinds of hardware can exchange dataaccording to agreed rules, or protocols. All the applicationsmentioned (and many others) then use this infrastructureto communicate.TCP/IP (Transmission Control Protocol/Internet Protocol)provides the rules for transmitting data on the Internet.It consists of two parts. The IP (Internet Protocol) routespackets of data. The header information also includes:• The total length of the packet. In theory packets canbe as large as 65 kbytes; in practice they are limited toa smaller maximum.• An identification number that can be used if a packetis broken into smaller pieces for efficiency in transmission.This allows the packet to be reassembled atthe destination.• A “time to live” value that specifies how many hops(movements from one intermediate host to another)the packet will be allowed to take. This is reduced by1 for each hop. If it reaches 0, the packet is assumedto have gotten “lost” or stale, and is discarded.• A protocol number (the protocol is usually TCP, seebelow).• A checksum for checking the integrity of the headeritself (not the data in the packet).• The source and destination addresses.The source and destination are given as IP addresses,which are 32 bits long and typically written as four sets ofup to three numbers each—for example, 208.162.106.17A Network of NetworksAs the name implies, the Internet is a network that connectsmany local networks. The IP address includes an IDfor each network (called a subnet) and each host computeron the network. The arrangement and meaning of thesefields differs somewhat among five classes of IP addresses.The first three classes are designed for different sizes ofnetworks, and the latter two are used for special purposessuch as “multicasting” where the same data packet is sentto multiple hosts.Many Internet users (at home as well as in offices) arepart of a local network (see local area network). Typically,all users on the local network share a single Internetconnection, such as a DSL or cable line. This sharing

TCP/IP 469The header fields and data for an IP (Internet Protocol) packet. Thepackets can travel over different routes to the destination addressand then be reassembled in the correct order.is enabled by having one computer (or a hardware devicecalled a router) connected to the Internet, serving as thelink between the local network and the rest of the world. Afacility called Network Address Translation (NAT) assigns aprivate IP address to each computer on the network. Whena computer wants to make an Internet connection, its outgoingpacket is assigned a public IP address from a pool.When packets replying to that public address are received,they are converted back to the private address and thusrouted to the appropriate user.NAT has the benefit of providing some security againstintrusion, since from the outside only the single public IPaddress is visible, not the private addresses of the variousNetwork Address Translation (NAT) can protect computers on alocal network by giving outgoing packets an arbitrary public sourceaddress in place of a computer’s actual (private) address. Incomingpackets addressed to that public address are then routed to the correctprivate address using a table.machines on the network. However, using NAT (and a similarscheme called PAT that allows difference hosts to use thesame IP address by being assigned different port numbers)causes some slowdown because of the translation process.Another facility, Dynamic Host Configuration Protocol(DHCP), is used to assign an arbitrary available public IPaddress to each host when it connects to the network. Thissystem is now used by most DSL and cable systems, and itreduces the danger of running out of IP numbers (each networkis assigned a range of numbers, and is thus limited tothat many IP addresses).A more lasting and flexible solution to address depletionis the new Internet Protocol version 6 (IPv6). The newaddressing scheme allows for about 3 × 10 38 addresses,more than enough to accommodate every star in the knownuniverse if it were a networked computer! The scheme isbeing rolled out gradually but should be well established bythe end of the 2000 decade.Domain Name SystemInternet users typically don’t have to worry about IP numbers,except perhaps when configuring their software.Instead they use alphabetic addresses, such as http://www.factsonfile.com. The Domain Name System (DNS) sets up acorrespondence between the names (which include domainssuch as .com for commercial or .edu for educational institutions)and the IP numbers (see dns).Transmission Control ProtocolThe Transmission Control Protocol (the TCP part of TCP/IP) controls the flow of packets that have been structured asdescribed above. To use TCP, the sending computer opensa special file called a socket, which is identified by thecomputer’s IP number plus a port number. Standard portnumbers are used for the various protocols such as www(Web) and ftp (File Transfer Protocol). The receiving computerconnects using a corresponding socket. TCP includesbasic flow control and error-checking features similar tothose used for most data transmissions. For some applications(such as connecting to the domain name server) errorcontrol is not needed, so a simpler protocol called the UserDatagram Protocol is used.The Big PictureHow does TCP/IP fit into the use of the Internet? When anapplication such as an e-mail program, Web browser, or ftpclient makes a connection, IP packets using TCP flow controlcarry the requests from the client to the server and theserver’s response back to the client. Each application has itsown protocol to specify these requests (such as for a Webpage). For e-mail the protocol is SMTP (Simple Mail TransferProtocol); Web servers and browsers use HTTP (HypertextTransfer Protocol); and for file transfers it is FTP (FileTransfer Protocol). (See also e-mail, html, hypertext andhypermedia, and file transfer protocols.)Further ReadingHagen, Silvia. IPv6 Essentials. 2nd ed. Sebastapol, Calif.: O’Reilly,2006.

470 technical supportIPv6 Information Page. Available online. URL: http://www.ipv6.org/. Accessed August 22, 2007.Kozierok, Charles M. The TCP/IP Guide: A Comprehensive, IllustratedInternet Protocols Reference. San Francisco, Calif.: NoStarch Press, 2005.Leiden, Candace, and Marshall Wilensky. TCP/IP for Dummies. 5thed. New York: Wiley, 2003.Raz, Uri. “Uri’s TCP/IP Resources List.” Available online. URL:http://www.private.org.il/tcpip_rl.html. Accessed August 22,2007.technical supportCompetition and user demand have led to modern softwarebecoming increasingly complex and often stuffed with esotericfeatures. Despite improvement in programs’ own builtinhelp systems (see help systems), users will often havequestions about how to perform particular tasks. There willalso be times when a program doesn’t perform as the userexpects because the user misunderstands some feature ofthe program, the program has an internal flaw (see bugs anddebugging), or there is a problem in interaction between theapplication program, the user’s operating system, or the user’shardware (see device driver).To get help when problems arise, users often turn tothe technical support facility, often called a help desk. Thisfacility can either be internal to an organization (helpingthe organization’s computer users with a wide rangeof problems), or belong to the maker of the software (andavailable in varying degrees to all licensed users of thatsoftware).Large help desks often have two or more levels or tiersof assistants. The first tier assistant can respond to the simplest(and usually most common) situations. For example, afirst-tier support person for a cable or DSL Internet ServiceProvider could tell a caller whether service has been interruptedin their area and if not, take the caller through a setof steps to reset a “hung” modem. If the situation is morecomplex (or the basic steps do not resolve it), the call will be“escalated” to the next tier, where a more experienced techniciancan address detailed software configuration issues.Advanced technical support representatives can usetools such as remote operation software that lets them takeover control of the user’s PC in order to see exactly what isgoing on. They can also submit detailed problem reports toengineers in cases were a modification (patch) to the softwaremight be needed.Support AlternativesUsers who are dissatisfied with the wait for phone supportor dealing with poorly trained support personnel may beable to take advantage of alternative sources of informationand support. Most software companies now have Web sitesthat include a support section that offers services such as• Frequently Asked Questions (FAQ) files with answersto common problems.• A searchable “knowledge base” of articles relating tovarious aspects of the software, including compatibilitywith other products, operating system issues,and so on.• Forms or e-mail links that can be used to submitquestions to the company. Typically questions areanswered in one or two working days.• A bulletin board where users can share solutions andtips relating to the software.Web sites for publications such as PC Magazine and ZDNetalso offer articles and other resources for working with thevarious versions of Microsoft Windows and popular applications.Technical Support IssuesAs with many other aspects of the computer industry, thechanging economic climate has had an impact on technicalsupport practices. Many companies are hoping that providingmore extensive Web-based technical support willreduce the need for help desk representatives. Companiesthat don’t want to create their own support Web sites canturn to consultants such as Expertcity.com or PCSupport.com to create and manage such services for a fee.Another way companies have sought to reduce help deskcosts is to outsource their technical support operations.Most software companies are in areas with a relatively highcost of labor. With modern communications and networkservices, there is no need for the help desk personnel to beat the company headquarters. Workers in less expensiveparts of the United States or even in countries such as Indiathat have a large pool of technically trained, English-speakingpersons can often offer help services at a lower costthan running an in-house help desk, even when the cost oftraining and phone line charges are taken into account. Onthe other hand, there have been complaints by customersthat some overseas support staff have language problems orare poorly trained, using only rote “scripts” to try to diagnoseproblems.Poor technical support can lead customers to switchto competing products. While this may not be much of aconcern in a rapidly expanding industry (where new customersseem to be available in abundance), the situationis different in stagnant or contracting economic conditions.Trying to reduce technical support costs may bringsome short-term help to the bottom line, but in the longerrun the result might be fewer customers and less revenue.An alternative approach is to consider technical supportto be part of a broad effort to maintain customer loyalty;this is often called Customer Relationship Management(see customer relationship management). With regardto technical support, CRM is implemented by using softwareto better track the resolution of customer’s problemsas well as to use information obtained in the support processto offer the customer additional products or servicescustom-tailored to individual situations. With such anapproach the effort to provide better technical support isseen not simply as a necessary business expense but as aninvestment with an expected (though hard to measure)return.

technical writing 471Further ReadingBest Free Technical Support Sites. Available online. URL: http://www.techsupportalert.com/best_free_tech_support_sites.htm. Accessed August 22, 2007.Czegel, Barbara. Help Desk Practitioner’s Handbook. New York:Wiley, 1999.Fleischer, Joe, and Brendan Read. The Complete Guide to CustomerSupport: How to Turn Technical Assistance into a ProfitableRelationship. New York: CMP Books, 2002.Tourniaire, Françoise, and Richard Farrell. The Art of SoftwareSupport: Design & Operation of Support Centers and HelpDesks. Upper Saddle River, N.J.: Prentice Hall, 1997.Tyman, Dan. “Tech Nightmares: Customer Service.” CNETReviews, January 24, 2005. Available online. URL: http://reviews.cnet.com/4520-10168_7-5621441-1.html. AccessedAugust 22, 2007.technical writingUsers of complex systems require a variety of instructionaland reference materials, which are produced by technicalwriters and editors. (It should be noted that technical writingcovers many areas other than computer software andsystems. However, it is the latter that fall within the scopeof this book.)The traditional products produced by technical writersin the computer industry can be divided into three broadcategories: software manuals, trade books, and in-housedocumentation for developers.Software ManualsUntil the mid-1990s, just about every significant softwareproduct came with a manual (or a set of manuals). A typicalmanual might include an overview of the program, anintroductory tutorial, and a complete, detailed referenceguide to all commands or functions.In theory, staff technical writers (or sometimes contractors)develop the manuals during the time the program isbeing written. They have access to the programmers forasking questions about the program’s operation, and theyreceive updates from the developers that describe changesor added features. In practice, however, writers may notbe assigned to a project until the program is almost done.The programmers, who are under deadline pressure, maynot be very communicative, and the writers may have tomake their best guess about some matters. The result canbe a manual that is no longer “in synch” with the program’sactual feature set.Technical writers often work in a publications departmentwith other professionals including editors, desktoppublishers, and graphics specialists. While manuals can bewritten using an ordinary word processing program, manydepartments use programs such as FrameMaker that aredesigned for the production and management of complexdocuments.In recent years, many software manufacturers havestopped including printed user manuals with their packages,or include only slim “Getting Started” manuals. Asa money-saving measure the traditional documentation isoften replaced by a PDF (Adobe Portable Document Format)document on the CD. There is also a greater relianceon extensive on-line help, using either a Windows orMacintosh-specific format or the HTML format that is thelingua franca of the World Wide Web. (See documentation,user.)Technical writers have thus had to learn how to constructHelp files in these various formats (see authoringsystems, help systems, and html). Creation of interactivetutorials also requires knowledge of multimedia formatsand even animation (such as Flash).Trade BooksAs millions of people became new computer users duringthe 1980s, a thriving computer book publishing industryoffered users a more user-friendly approach than that usuallyprovided in the manuals issued by the software companies.The “Dummies” books, offering bite-sized servingsof information written in a breezy style and accompaniedby cartoons, eventually spread beyond computers into hundredsof other fields and the format was then copied byother publishers. Publishers such as Sams, Coriolis, and particularlyO’Reilly have aimed their offerings at more experiencedusers, programmers, and multimedia developers.Computer trade books are often written by experienceddevelopers and systems programmers who can offeradvanced knowledge and “tips and tricks” to their lessexperienced colleagues. Since many technical “gurus” arenot experienced writers, the best results often come fromcollaboration between the expert and an experienced technicalwriter and/or editor who can review the material forcompleteness, organization, and clarity.In recent years there has been some contraction inthe computer book industry. This has arisen from severalsources: improved on-line help included in products; thedominance of many applications areas by a handful of products;and fewer people needing beginner-level instruction.In-House DocumentationMany technical writers work within software companies orin the information systems departments of other corporations,universities, or government agencies. Their work isgenerally more highly structured than that of the manualor book writer. As part of a development team, a technicalwriter may be in charge of creating documentation describingthe data structures, classes, and functions within theprogram. This task is aided by a variety of tools includingfacilities for extracting such information automatically fromC++ or Java programs. The writer may also be responsible formaintaining logs that show each change or addition made tothe program during each compiled version or “build.”This type of technical writing requires detailed knowledgeof operating systems, programming languages,software development tools, and software engineeringmethodology. It also requires the ability to work well aspart of a team, often under conditions of high pressure.Technical Writing as a ProfessionUntil the 1980s, few institutions offered degrees in technicalwriting. Programmers with an interest in writing orwriters with a technical bent entered the field informally.

472 technology policyDuring the 1980s, the number of degree offerings increased,and people began to specifically prepare for the field, oftenby earning a computer science degree with a specializationin technical writing. Organizations such as the Society forTechnical Communication have offered technical writersand editors a forum for discussing their profession, includingissues relating to certification.Further ReadingAlred, Gerald J., Charles T. Brusaw, and Walter E. Oliu. The Handbookof Technical Writing. 8th ed. Boston: St. Martin’s Press, 2006.Lindsell-Roberts, Sheryl. Technical Writing for Dummies. New York:Hungry Minds, 2001.Pringle, Alan S., and Sarah S. O’Keefe. Technical Writing 101: AReal-World Guide to Planning and Writing Technical Documentation.2nd ed. Research Triangle Park, N.C.: ScriptoriumPublishing Services, 2003.Society for Technical Communication. Available online. URL:http://www.stc.org/. Accessed August 22, 2007.technology policyPolicy makers have found themselves increasingly confrontedwith difficult issues relating to the Internet, theinformation industry, and an economy increasingly dependenton computing and communications technology. Aswith other complex issues such as health care, there hasbeen difficulty reaching a consensus or formulating comprehensiveor consistent policies.Historically many of the early innovators in moderncomputing (even Microsoft) have tended to keep aloof frompolitics and lobbying. This may have been due in part tolibertarian or laissez-faire beliefs that the best thing thegovernment could do for the information highway was tostay out of its way.Today, however, with vital economic interests and thousandsof jobs at stake, major computer companies have joinedthe political game with a vengeance. In turn, candidates in therun up to the 2008 presidential election have not neglectedto court technology leaders. (For example, in 2008 leadingDemocratic candidates Hillary Rodham Clinton and BarackObama both outlined extensive technology agendas.)Major policy issues involving information technologyindustries include:• foreign trade and the protection of intellectual property(see intellectual property and computingand software piracy and counterfeiting)• attempts to reform the patent system to prevent whatis seen as dubious and expensive litigation• the need for an increasing number of trained workersand providing a sufficient number of visas for foreignworkers (see globalization and the computerindustry)• preserving equal access to the Internet (see net neutrality),which pits content providers against telecommunicationscompanies• promoting the development of a next-generationInternet infrastructure (“Internet 2”)• government support for computer research (such asthrough the National Science Foundation)—see governmentfunding of computer research• favorable treatment of online businesses with regardto taxation (often objected to by traditional brickand-mortarbusinesses)—see e-commerce• laws against computer-related fraud and other crime(see computer crime and security and onlinefrauds and scams)• Privacy regulations (see identity theft and privacyin the digital age)The computer industry is also involved in issues thatwill affect its future over the longer term, such as the needto improve math and science education in elementary andhigh schools, energy and environmental policy, and issuessuch as health care and pensions that affect all sectors ofthe economy.International AspectsIn a global industry, American information technology policycannot be considered without looking at the policiesof other nations (both industrialized and developing) andtheir potential impacts. For example, China’s success (orlack thereof) in protecting intellectual property has a directimpact on the revenue of major software companies. Similarly,issues of censorship (see censorship and the Internet)create dilemmas for companies that must balanceconcern for human rights with the opportunity to enterhuge new markets. Other important aspects of comparativetechnology policy include research funding, subsidies, patentand copyright law, and labor standards.Further ReadingAspray, William, ed. Chasing Moore’s Law: Information TechnologyPolicy in the United States. Raleigh, N.C.: SciTech Publishing,2004.Coopey, Richard, ed. Information Technology Policy: An InternationalHistory. New York: Oxford University Press, 2004.Marcus, Alan I., and Amy Sue Bix. The Future Is Now: Scienceand Technology Policy in America since 1958. Amherst, N.Y.:Humanity Books, 2006.MIT Center for Technology, Policy, and Industrial Development.Available online. URL: http://web.mit.edu/ctpid. AccessedNovember 27, 2007.Nuechterlein, Jonathan E., and Philp J. Weiser. Digital Crossroads:American Telecommunications Policy in the Internet Age. Cambridge,Mass.: MIT Press, 2007.Ricadela, Aaron. “Technology Companies Have Much at Stake in2008.” Business Week, September 19, 2007. Available online.URL: http://www.businessweek.com/technology/content/sep2007/tc20070917_079427.htm. Accessed November 26, 2007.U.S. Technology Administration. Available online. URL: http://www.technology.gov/. Accessed November 27, 2007.telecommunicationsSince its birth in the mid-20th century, the digital computerand the telephone have had a close mutual relationship.Many of the first programmable calculators and computersbuilt in the early 1940s used relays and other compo-

telecommuting 473nents that were being manufactured for the increasinglyautomated phone system (see Aiken, Howard). The phoneindustry contributed ideas as well as hardware. Scientists atthe Bell Laboratories carried out fundamental research intoinformation theory that would soon be applied to data communications(see Shannon, Claude).As computers became more capable in the 1950s and1960s, they began to return the favor, making possibleincreasing automation for the phone system. Meanwhile,computers were starting to be hooked up to telephone lines(see modem) so they could exchange data and allow theirusers to communicate (see network).The development of a global network (see Internet)and its growth through the 1980s provided a universal platformfor data communications. At first, the Internet wasused mostly by academics and engineers, but the adventof the World Wide Web and in particular, graphical Webbrowsers made Internet access ubiquitous among smallbusinesses and home users by the late 1990s.Institutional Internet users often had fast access throughdedicated phone lines (designated T-1, and so on), whilehomes, small businesses, and schools were limited to muchslower dial-up access. This began to change in the late 1990sas alternatives to POTS (“plain old telephone service”)emerged in the form of DSL (a much faster service runningover regular phone lines) and cable modems that used theinfrastructure that already brought TV to millions of homes.Impact of DeregulationPrior to the court-ordered breakup of AT&T in 1984, thephone industry functioned in a monolithic way and wasnot very responsive to the needs of the growing computernetworking industry.The breakup of AT&T led to growing competition, providinga wider variety of telecommunications equipmentand lower phone rates just as PC users were starting tobuy modems and sign up with online services and bulletinboards. The growing deregulation movement in the1990s (culminating in the Telecommunications Act of1996) furthered this process by opening cable and broadcasttelevision, radio, and other wireless communication tocompetition.With more than half of American Internet users onhigh-speed connections (see broadband), the delivery ofcommunications and media over the Net can only grow.Wireless and mobile services (satellite, cell network,and 802.11—see wireless computing) have also beengrowing vigorously. The result is that the “informationhighway” now has many lanes, with some being expresslanes.Convergence and the FutureThe ability of the Internet to transmit any sort of data virtuallyanywhere at relatively low cost has created new alternativesto traditional communications technologies. Forexample, sending digitized voice telephone calls as packetsover the Internet can provide a lower-cost alternativeto conventional long distance calling (see VoIP). At thesame time, previously separate functions are converginginto “smarter” devices. Thus, the handheld computer andthe cell phone seem to be converging into a single devicethat can provide data management (see smartphone). Webbrowsing, and communications in a single package.Computers and communications technology will continueto grow more intertwined. Today it is increasingly hard to distinguishinformation technology, media content, and communicationstechnology as being distinctive sectors. After all, aconsumer can watch a movie in the theater or later on broadcast,cable, or satellite TV, rent it on commercial videotapeor DVD disk (playable on PCs as well as portable players),or even view it as a streaming file direct from the Internet.Although these technologies have differing technical constraints,their end products are the same for the consumer.This multiplicity of function means that the competitiveenvironment is increasingly hard to predict, since there areso many possible players. The companies offering contentthrough this variety of technologies are also increasinglyintertwined.For analysts, studying any technology requires awarenessof the many possible alternatives, while studying anyapplication means considering the many possible technologicalimplementations. For policy makers and regulators,the challenge is to provide for such public goods as equalaccess, privacy, and protection of intellectual property in acommunications infrastructure that is truly global in scopeand evolving at a pace that frequently outdistances thepolitical process.Further ReadingBenjamin, Stuart Minor, et al. Telecommunications Law and Policy.2nd ed. Durham, N.C.: Carolina Academic Press, 2006.———. Telecommunications Law and Policy, 2007 Supplement. Durham,N.C.: Carolina Academic Press, 2007.Goleniewski, Lillian. Telecommunications Essentials: The CompleteGlobal Source. 2nd ed. Upper Saddle River, N.J.: Addison-Wesley, 2007.Hill Associates. Telecommunications: A Beginner’s Guide. Berkeley,Calif.: McGraw-Hill/Osborne, 2002.“Media and Telecommunications Policy and Legislation.” MoffittLibrary, UC Berkeley. Available online, URL: http://www.lib.berkeley.edu/MRC/MediaPolicy.html. Accessed August 22,2007.Olejniczak, Stephen P. Telecom for Dummies. Hoboken, N.J.: Wiley,2006.telecommutingTelecommuting (also called telework) is the ability to workfrom home or from some location other than the mainoffice. According to a report by the nonprofit organizationWorldatWork, 28.7 million people worked from home atleast one day a month in 2006. (Self-employed persons, ofcourse, have a much higher rate of working from home.)Telecommuting was made possible by the growing capabilitiesof home computers and the availability of networkconnections that allow the worker at home to have accessto most of the people and facilities that would be availableif the worker were on site. Workers and companies that promotetelecommuting often cite the following advantages:

474 telepresence• elimination of stressful, time-wasting commutes• workers may be more productive because they havefewer office distractions, unnecessary meetings, etc.• reduction of traffic, air pollution, and fuel costs• greater flexibility in working hours• the ability of working parents with small children tocombine child care and work to some extent• reduction of costs associated with office facilitiesHowever, telecommuting has its critics in management.Some of the problems or disadvantages cited include:• Worker productivity may decrease due to lack of sufficientdiscipline and workers becoming distracted athome.• managers may have trouble keeping track of or evaluatingthe activities of workers who are not physicallypresent.• Telecommuters may miss critical information and go“out of the loop.”• Security can be compromised, particularly throughtheft of laptops containing sensitive personal data.• Possible legal liabilities and application of OSHA rulesto home working situations.It is true that telecommuting is suitable mainly forjobs that involve information processing rather than person-to-personcontact, such as service jobs. However, theuse of videoconferencing or Web conferencing technologyincreasingly makes it possible for suitably equipped telecommutersto participate in meetings almost as directlyas if they were physically present (see conferencing systemsand telepresence).In some cases involving videoconferencing or otheractivities that require high-powered computer systems andhigh bandwidth connections, telecommuters physicallycommute to a “satellite work center” near their home thathas the appropriate equipment. This can provide some ofthe advantages of telecommuting such as flexibility andlower commute and office costs.A number of issues must be worked out between workersand management for any telecommuting program, including:• Who will pay for the equipment used by the telecommuter• Procedures for monitoring the work• How telecommuters will participate in meetings(either remotely or in person)• The portion of the worker’s hours involving telecommuting,and the portion requiring attendance inhouseTrendsTelecommuting was touted in the mid-1990s as the waveof the future. In reality, the statistics given earlier suggestwhile it is a viable option for a significant minority ofworkers, telecommuting is not growing as rapidly as hadbeen predicted. The growing power of desktop PCs and theavailability of broadband (DSL or cable) network connectionsshould help facilitate telecommuting. In the longerterm new technologies may make the distinction betweentelecommuters and physically present workers much lessimportant (see telepresence and virtual reality).Further ReadingAmerican Telecommuting Association. Available online. URL:http://www.yourata.com/index.html. Accessed August 22,2007.Dziak, Michael. Telecommuting Success: A Practical Guide for Stayingin the Loop While Working Away from the Office. Indianapolis:Park Avenue, 2001.Messmer, Ellen. “Telecommuting Security Concerns Grow.” Info-World, April 18, 2006. Available online. URL: http://www.infoworld.com/article/06/04/18/77520_HNtelecommuntingsecurity_1.html.Accessed August 22, 2007.Zetlin, Minda. Telecommuting for Dummies. New York: HungryMinds, 2001.telepresenceAn old phone company slogan asserted that “long distanceis the next best thing to being there.” Today technologyhas made the ability to “be there” a much more completeexperience. It is now quite common for businesspersonsto “attend” a meeting in a distant city using video camerasto see and be seen, with images and voice traveling overspecial leased lines or high speed Internet connections (seevideoconferencing).While videoconferencing and suitable software allowsremote interaction and collaboration (such as being ableto build a spreadsheet or diagram together), the remoteparticipant has little ability to physically interact with theenvironment. He or she can’t walk freely around, perhapsjoining other meeting participants in an adjacent roomwhile they have pastries and coffee. The remote participantalso cannot handle physical objects such as models.There are two basic approaches to letting persons havean unconstrained experience in a remote environment. Thefirst is to use technology to create a virtual presence where aperson can experience a simulated environment from manydifferent angles and move freely through it while graspingand manipulating objects (see virtual reality). In a virtualenvironment each participant can be represented by an“avatar” body that can be programmed to move in responseto head trackers, gloves, and other devices.However, a virtual reality is an artificial representationof the world. A group of people having a meeting in a physicalspace can’t interact with someone who is in virtual spaceexcept in the most rudimentary ways. To be on an equalfooting, all participants would have to be in either physicalor virtual space.TeleroboticsThe alternative is to connect the remote participant to amobile robot (this is sometimes called telerobotics). Suchrobots already exist, although their capabilities are limited

terminal 475and they are not yet widely used for meetings. RodneyBrooks, director of the MIT Artificial Intelligence Laboratory,foresees a not very distant future in which such robotswill be commonplace.The robot will have considerable built-in capabilities,so the person who has “roboted in” to it won’t need toworry about the mechanics of walking, avoiding obstacles,or focusing vision on particular objects. Seeing and actingthrough the robot, the person will be able to move aroundan environment as freely as persons who are physically present.The operator can give general commands amounting to“walk over there” or “pick up this object” or perform moredelicate manipulations by using his or her hands to manipulategloves connected to a force-feedback mechanism.Brooks sees numerous applications for robotic telepresence.For example, someone at work could “robot in” to hisor her household robot and do things such as checking tomake sure appliances are on or off, respond to a burglaralarm, or even refill the cat’s food dish. Robotic telepresencecould also be used to bring expertise (such as that of asurgeon) to any site around the world without the time andexpense of physical travel. Indeed, robots may be the onlyway (for the foreseeable future) that humans are likely toexplore environments far beyond Earth (see space explorationand computers).Further ReadingBallantyne, Garth H., Jacques Marescaux, and Pier Cristoforo Giulianotti.The Primer of Robotic and Telerobotic Surgery: A BasicGuide to Heart Disease. 4th ed. Baltimore: Lippincott Williams& Wilkins, 2004.Frere, Manuel, et al., eds. Advances in Telerobotics. New York:Springer, 2007.Goldberg, Ken, ed. The Robot in the Garden: Telerobotics and Telepistemologyin the Age of the Internet. Cambridge, Mass.: MITPress, 2000.NASA Space Telerobotics Program. Available online. URL: http://ranier.hq.nasa.gov/telerobotics_page/telerobotics.shtm.Accessed August 22, 2007.Sheppard, P. J., and G. R. Walker, eds. Telepresence. New York:Springer, 1998.Tele-Robotics Links [Online robots, etc.]. Available online. URL:http://queue.ieor.berkeley.edu/~goldberg/art/teleroboticslinks.html.Accessed August 22, 2007.templateThe term template is used in a several contexts in computing,but they all refer to a general pattern that can be customizedto create particular products such as documents.In a word processing program such as Microsoft Word, atemplate (sometimes called a style sheet) is a document thatcomes with a particular set of styles for various elementssuch as titles, headings, first and subsequent paragraphs,lists, and so on. Each style in turn consists of various characteristicssuch as type font, type style (such as bold), andspacing. The template also includes properties of the documentas a whole, such as margins, header, and footer.To create a new document, the user can select one ofseveral built-in templates for different types of documentssuch as letters, faxes, and reports, or design a custom templateby defining appropriate styles and properties. Specialsequences of programmed actions can also be attached to atemplate (see macro).Templates can be created and used for applications otherthan word processing. A spreadsheet template consists ofappropriate macros and formulas in an otherwise blankspreadsheet. When it is run, the template prompts the userto enter the appropriate values and then the calculationsare performed. A database program can have input formsthat serve in effect as templates for creating new records byinputting the necessary data.Class TemplatesSome programming languages use the term template to referto an abstract definition that can be used to create a varietyof similar classes for handling different types of data, whichin turn are used to create actual objects. For example, oncethe programmer defines the following template:templateANY_TYPE maximum(ANY_TYPE a, ANY_TYPE b){return (a > b) ? a : b;This template provides any class with the maximumfunction, which can compare any two objects of that classand return the larger one. (See c++, class, and objectorientedprogramming.)Further ReadingAbrams, David, and Aleksey Gurtovoy. C++ Template Metaprogramming:Concepts, Tools, and Techniques from Boost andBeyond. Upper Saddle River, N.J.: Addison-Wesley Professional,2004.Free Templates for Work, Home, and Play. Microsoft Office Online.Available online. URL: http://office.microsoft.com/en-us/templates/FX100595491033.aspx.Accessed August 22, 2007.“Introduction to the Standard Template Library” [for C++]. SGI.Available online. URL: http://www.sgi.com/tech/stl/stl_introduction.html.Accessed August 22, 2007.Krieger, Stephanie. Advanced Microsoft Office Documents Inside Out.2007 ed. Redmond, Wash.: Microsoft Press, 2007.Vandevoorde, David, and Nicolai M. Josuttis. C++ Templates: The CompleteGuide. Upper Saddle River, N.J.: Addison-Wesley, 2002.Utvich, Michael, Ken Milhous, and Yana Beylinson. 1 Hour WebSite: 120 Professional Templates and Skins. Hoboken, N.J.:Wiley, 2006.Walkenbach, John. Microsoft Office Excel 2007 Bible. Indianapolis:Wiley, 2007.terminalThroughout the 1950s, operators interacted with computersprimarily by punching instructions onto cards that werethen fed into the machine (see punched cards and papertape). Although this noninteractive batch processing procedurewould continue to be used with mainframe computersduring the next two decades, another way to use computersbegan to be seen in the 1960s.With the beginning of time-sharing computer systems,several users could run programs on the computer at thesame time. The users communicated with the machine by

476 text editortyping commands into a Teletype or similar device. Such adevice is called a terminal.The simple early terminals did little more than acceptlines of text commands from the user and print responsesor lines of output coming from the computer. However, anewer type of terminal began to replace the Teletype. Itconsisted of a keyboard attached to a televisionlike cathoderay tube (CRT) display. User still typed commands, but thecomputer’s output could now be displayed on the screen.Gradually, CRT terminals gained additional capabilities.The text being entered was now stored in a memory bufferthat corresponded to the screen and the user could usespecial control commands or keys to move the input cursoranywhere on the screen when creating a text file. This madeit much easier for users to revise their input (see text editing).These “smart terminals” had their own small processorand ran software that provided these functions.During the 1970s, the UNIX operating system developeda sophisticated way to support the growing variety ofterminals. It provided a library of cursor-control routines(called curses) and a database of terminal characteristics(called termcap).When the personal computer came along, it had akeyboard, a processor, the ability to run software, and aconnection for a TV or monitor. The PC thus had all theingredients to become a smart terminal. Indeed, a modernPC is a terminal, but users don’t usually have to think inthose terms. The exception is when the user runs a communicationsprogram to connect to a remote computer (perhapsa bulletin board) with a modem. These programs, suchas the Hyperterminal program that comes with Windows,allow the PC to emulate (work like) one of the standard terminaltypes such as VT-100. This ability to emulate a standardterminal means that any software that supports thatphysical terminal should also work remotely with a PC.Today most interaction with remote programs is througha Web browser, although protocols such as telnet are stillused to provide terminallike access to remote programs.Many commands previously entered as text lines in a terminalare now given using the mouse with menus and icons(see user interface).The relationship between a terminal and remote computeris analogous to that between a workstation (or desktop PC)and the network server in that the burden of processing isdivided between the two devices in various ways (see clientservercomputing). A “thin client” PC performs relativelylittle processing with the server doing most of the work.Specialized terminals are still used for many applications.An ATM, for example, is a special-purpose bankingterminal driven by a keypad and touchscreen.Further ReadingArchive of Video Terminal Information. Available online. URL:http://www.cs.utk.edu/~shuford /terminal/index.html.Accessed August 22, 2007.Free Software Foundation. The Termcap Library. Available online.URL: http://www.gnu.org/manual/termcap-1.3/termcap.html.Accessed August 22, 2007.Linux Terminal Server Project. Available online. URL: http://www.ltsp.org/. Accessed August 22, 2007.text editorAs noted in the previous article (see terminal), an alternativeto batch-processing punch card driven computer operationsemerged in the 1960s in the form of text commandstyped at an interactive console or terminal. At first textcould be typed only a line at a time and there was no way tocorrect a mistake in a previous line.Soon, however, programmers began to create text editingprograms. The first editors were still line-oriented, butthey stored the lines for the current file in memory. To displaya previous line, the user might simply type its number.To correct a word in the line the user might type somethinglikec/fot/forto change the typo “fot” to the word “for” in the current line.Starting in the early 1970s, the UNIX system providedboth a line editor (ed or ex) and a “visual editor” (vi). The lattereditor works with terminals that can display full screensof text and allow the cursor to be moved anywhere on thescreen. This type of editor is also called a screen editor.Most ordinary PC users use word processors rather thantext editors to create documents. Unlike a text editor, aword processor’s features are designed to create output thatlooks as much like a printed document as possible. Thisincludes the ability to specify text fonts and styles. However,most systems also include a simpler text editor thatcan be useful for making quick notes (in Windows this programis indeed called Notepad).The primary use of text editors today is to create programsand scripts. These must generally be created usingonly standard ASCII characters (see characters andstrings), without all the embedded formatting commandsand graphics found in word processing documents. Programmer’stext editors can be very sophisticated in theirown right, providing features such as built in syntax checkingand formatting or (as with the Emacs editor) the abilityto program the editor itself. Ultimately, however, programeditors must create a source code file that can be processedby the compiler.Text editors are also useful for writing quick, shortscripts (see scripting languages) and can be handy forwriting HTML code for the Web. However, many Web pagesare now designed using word processor–like programs thatconvert the WYSIWYG (what you see is what you get) formattinginto appropriate HTML codes automatically.Further ReadingCameron, Debra, et al. Learning GNU Emacs. 3rd ed. Sebastapol,Calif.: O’Reilly, 2005.Chassell, Robert J. An Introduction to Programming in Emacs Lisp.2nd ed. Boston, Mass.: GNU Press, 2004.Robbins, Arnold, and Linda Lamb. Learning the vi Editor. 6th ed.Sebastapol, Calif.: O’Reilly, 1998.Shareware Text Editors, Word Processors, etc. Available online.URL: http://www.passtheshareware.com/c-txtwp.htm. AccessedAugust 22, 2007.Smith, Larry L. How to Use the UNIX-LINUX vi Text Editor: Tips,Tricks, and Techniques (And Tutorials Too!) Charleston, S.C.:BookSurge, 2007.

Torvalds, Linus 477texting and instant messagingAlthough they use different devices and formats, textmessaging on cell phones and PDAs and instant messagingthrough online services have much in common. Bothinvolve sending short messages to other users who canreceive them and reply as soon as they are online. (Thisis an ad hoc connection that differs from a chat room [seechat, online] in that the latter is an established locationwhere people go to converse with other members. It alsodiffers from an online discussion group [see conferencingsystems and netnews and newsgroups] where messagesare posted and may be replied to later, but there is noreal-time communication.)Text messaging or texting uses a protocol called ShortMessage Service (SMS), which is available with most cellphones and service plans as well as PDAs that have wirelessconnections. When a user sends a message to a designatedrecipient, it goes to a service center where it isrouted to the destination phone; if that phone is not connected,the message is stored and retried later. Typicallymessages are limited to 160 characters, though up to sixor so messages can be concatenated and treated as a longermessage.While texting did not become popular until the late1990s, instant messaging began in the 1970s as a way formultiple users on a shared computer or network (such asa UNIX system) to communicate in real time using commandssuch as send and talk (the latter being more conversational—seechat, online). In the late 1980s and early1990s, various dial-up services (see America Online andonline services) provided for sending text messages (AOLwas the first to use the term instant messages for its facility).By the mid-1990s instant messaging was well established onthe Internet, often employing a graphical user interface, aswith ICQ and AOL Instant Messenger (AOL later acquiredICQ as well).There have been efforts to allow users of different instantmessaging systems to communicate with one another, butresistance on the part of the proprietary networks (oftenciting security concerns) has hobbled this process thus far.Instant messaging has also been implemented as an applicationfor phones and other mobile devices (an effort headedby the Open Mobile Alliance). Generally this involvesreworking the IM software to use the SMS text service tocarry messages.Cultural ImpactBetween 2000 and 2004 the numbers of text messages sentworldwide soared from 17 billion to 500 billion. At about adime a message, texting became a major source of revenuefor phone companies. Since then, texting has continuedto grow, particularly in parts of Europe, the Asia-Pacificregion (particularly China), and Japan (where it has largelybecome an Internet-based service).In the United States texting is most popular amongteenagers (see young people and computing). It is notuncommon to see a bench full of teens talking excitedly toone another while carrying on simultaneous texting withunseen friends in what, to many adult onlookers, appearsto be an incomprehensible code, their conversation perhapsending with ttyl (talk to you later).Loosely affiliated groups communicating by text (seeflash mobs) have organized everything from “happenings”to serious protest campaigns (as in the anti-WTO [WorldTrade Organization] demonstrations in Seattle in 1999 andin the Philippines uprising in 2001.)The popularity of texting has increasingly attracted theattention of fraudsters (see phishing and spoofing andspam) as well as more legitimate marketers.Further ReadingAll about Instant Messengers. Available online. URL: http://aboutmessengers.com/. Accessed November 29, 2007.Hord, Jennifer. “How SMS Works.” Available online. URL: http://communication.howstuffworks.com/sms.htm. AccessedNovember 29, 2007.Le Bodic, Gwenael. Mobile Messaging Technologies and Services:SMS, EMS and MMS. 2nd ed. New York: John Wiley and Sons,2005.Rheingold, Howard. Smart Mobs: The Next Social Revolution. Cambridge,Mass.: Perseus Books, 2003.SMS Speak Translator. Available online. URL: http://smspup.com/smsSpeak.php. Accessed November 29, 2007.“Web Messengers Handbook.” Available online. URL: http://web2.ajaxprojects.com/web2/newsdetails.php?itemid=35. AccessedNovember 29, 2007.Torvalds, Linus(1969– )FinnishSoftware DeveloperLinus Torvalds developed Linux, a free version of the UNIXoperating system that has become the most popular alternativeto proprietary operating systems.Torvalds was born on December 28, 1969, in Helsinki,Finland. His childhood coincided with the microprocessorrevolution and the beginnings of personal computing.At the age of 10, he received a Commodore PC from hisgrandfather, a mathematician. He learned to write his ownsoftware to make the most out of the relatively primitivemachine.In 1988, Torvalds enrolled in the University of Helsinkito study computer science. There he encountered UNIX, apowerful and flexible operating system that was a delightfor programmers who liked to tinker with their computingenvironment. Having experienced UNIX, Torvalds couldno longer be satisfied with the operating systems that ranon most PCs, such as MS-DOS, which lacked the powerfulcommand shell and hundreds of utilities that UNIX userstook for granted.Torvalds’s problem was that the UNIX copyright wasowned by AT&T, which charged $5,000 for a license to runUNIX. To make matters worse, most PCs weren’t powerfulenough to run UNIX anyway.At the time there was already a project called GNUunderway (see open source and Stallman, Richard). TheFree Software Foundation was attempting to replicate all thefunctions of UNIX without using any of AT&T’s proprietary

478 touchscreencode. This would mean that the AT&T copyright wouldnot apply, and the functional equivalent of UNIX could begiven away for free. Stallman and the FSF had already providedkey tools such as the C compiler and the Emacs programeditor. However, they had not yet created the heart ofthe operating system (see kernel). The kernel contains theessential functions needed for the operating system to controlthe computer’s hardware, such as creating and managingfiles on the hard drive.In 1991, Torvalds wrote his own kernel and put ittogether with the various GNU utilities to create what soonbecame known as Linux. Torvalds adopted the open sourcelicense (GPL) pioneered by Stallman and the FSF, allowingLinux to be distributed freely. The software soon spreadthrough ftp sites on the Internet, where hundreds of enthusiasticusers (mainly at universities) helped to improveLinux, adding features and writing drivers to enable it towork with more kinds of hardware.By the mid-1990s, the free and reliable Linux hadbecome the operating system of choice for many Web sitedevelopers. Torvalds, who still worked at the University ofHelsinki as a researcher, faced an ever-increasing burdenof coordinating Linux development and deciding when torelease successive versions. As companies sprang up to marketsoftware for Linux, they offered Torvalds very attractivesalaries, but he did not want to be locked into one particularLinux package (distribution).Instead, in 1997 Torvalds moved to California’s SiliconValley, where he became a key software engineer at Transmeta,a company that makes Crusoe, a processor designedfor mobile computing.In 2003 Torvalds left Transmeta. In 2004 he movedto Portland, Oregon, where the Linux Foundation, a nonprofitconsortium dedicated to promoting the growth ofLinux, supports his work. There he concentrates on guidingthe continuing development of the Linux core, or kernel.Although he strongly supports open-source software, Torvaldshas been criticized by some advocates for his pragmaticapproach of using proprietary software when it seemsto be more suitable to a given task.Further ReadingDibona, Chris. Open Sources: Voices from the Open Source Revolution.Sebastapol, Calif.: O’Reilly, 2001.“FM Interview with Linus Torvalds: What Motivates Free SoftwareDevelopers?” First Monday, vol. 3 (1998). Available online.URL: http://www.firstmonday.org/issues/issue3_3/torvalds/.Accessed August 23, 2007.Linux Foundation. Available online. URL: http://www.linuxfoundation.org/en/Main_Page.Accessed August 23, 2007.Richardson, Marjorie. “Interview: Linus Torvalds.” Linux Journal,November 1, 1999. Available online. URL: http://www.linuxjournal.com/article/3655.Accessed August 23, 2007.Torvalds, Linus, and David Diamond. Just for Fun: The Story of anAccidental Revolutionary. New York: HarperCollins, 2001.touchscreenAs the name implies, a touchscreen is a screen display thatcan respond to various areas being touched or pressed.Invented in 1971, the first form of touchscreens to becomepart of daily life were found on automatic teller machines(ATMs) and point-of-sale credit card processors.Touchscreens can detect the pressure of a finger or stylusin several ways: A “resistive” touchscreen uses two layersof electrically conductive metallic material separated bya space. When an area is touched, the two layers are electricallyconnected, and the change in electrical current is registeredand converted to a code that identifies the locationtouched. Surface acoustic wave (SAW) touchscreens usean ultrasonic wave that is interrupted by a touch; capacitivetouchscreens respond to the change in electron storage(capacitance) caused by contact with a human body. Variousother acoustic, mechanical (strain-based), or opticalsystems can also be used, with the latter being particularlypopular.Touchscreens can have drawbacks ranging from problemswith long fingernails to screen “keys” placed too closetogether for normal fingers. Responsiveness is also considerablyslower than with a keyboard. Depending on the technologyused, dirt or grease can also become a problem.Other ApplicationsIn addition to dedicated uses such as banking and retailing,touchscreens are a common form of input for mobilephones, PDAs, and similar devices (see pda and smartphone)where a “virtual” on-screen keyboard is often usedfor entering text. Particularly versatile systems such asApple’s iPhone combine proximity sensors with touchscreentechnology in order to be able to recognize gestures suchas pinching and flicking. Another example is Microsoft’s“Surface” interface. (For related technologies, see graphicstablet and tablet pc.)Further ReadingBaig, Edward C. iPhone for Dummies. New York: Wiley, 2007.Buxton, Bill. “Multi-Touch Systems That I Have Known andLoved.” Available online. URL: http://www.billbuxton.com/multitouchOverview.html. Accessed November 29, 2007.Microsoft Surface. Available online. URL: http://www.microsoft.com/surface/. Accessed November 29, 2007.Plaisant, Catherine. “High-Precision Touchscreens: MuseumKiosks, Home Automation and Touchscreen Keyboards.”University of Maryland Human-Computer Interaction Lab,January 31, 1999. Available online. URL: http://www.cs.umd.edu/hcil/touchscreens/. Accessed November 29, 2007.Woyke, Elizabeth. “Reach Out and Touch—A Phone Screen.”Forbes.com, November 28, 2007. Available online. URL:h t t p: // w w w. f o r b e s . c o m / t e c h n o l o g y / 2 0 0 7/ 11 / 2 8 /touch-screen s-phone s -tech-hol id ay tech07- c x _ e w_1128touch.html. Accessed November 29, 2007.transaction processingMany computer applications involve the arrival of a set ofdata that must be processed in a specified way. For example,a bank’s ATM system receives a customer’s request todeposit money together with identification of the accountand the amount to be deposited. The system must accept thedeposit, update the account balance, and return a receipt tothe customer. This is an example of real-time transactionprocessing.

tree 479Some applications process transactions in batches. Forexample, a company may run a program once a month thatgenerates paychecks and withholding stubs from employeerecords that include hours worked, number of dependentsclaimed, and so on. Indeed, in the ATM example, theaccount balance is typically not updated during the on-linetransaction, but instead a batch transaction is stored. Overnightthat transaction will be processed together with othertransactions affecting that account (such as checks), andthe balance will then be officially updated. (The programmodule that keeps track of the progress of transactions iscalled a transaction monitor.)There are several considerations that are important indesigning transaction systems. While some transactionsmay simply involve a request for information and do notupdate any files, many transactions may require that severalfiles or database records be updated. For example, a transferof funds from a saving account to a checking account willrequire that both accounts be updated: the first with a debitand the second with a credit. What happens if the computerperforms the savings debit but then goes down before thechecking account can be credited? The result would be anupset customer whose money seems to have disappeared.The solution to this problem is to design a process wherethe various updates are done not to the actual databasesbut to associated temporary databases. Once these potentialtransactions are posted, the system issues a “commit” commandto the databases. Each database must send a replyacknowledging that it’s ready to perform the actual update.Only if all databases reply affirmatively is the commit commandgiven, which updates all the databases simultaneously.stored in a binary tree, a program can use two pointers, oneto the current node’s left child and one to its right child(see pointers and indirection). The pointers can then beused to trace the paths through the nodes. If the tree representsa file that has been sorted (see sorting and searching),comparing nodes to the desired value and branchingaccordingly quickly leads to the desired record.Alternatively, the data can be stored directly in contiguousmemory locations corresponding to the successivenumbers of the nodes. This method is faster than havingto trace through successive pointers, and a binary searchalgorithm can be applied directly to the stored data. On theother hand it is easier to insert new items into a linked list(see list processing).A common solution is to combine the two structures,storing the linked list in a contiguous range of memory bystoring its root in the middle of the range, its left child atthe beginning of the range, its right child at the end, andthen repeatedly splitting each portion of the range to storeeach level of children. Intuitively, one can see that algorithmsfor processing such stored trees will take a recursiveapproach (see recursion).Further ReadingLewis, Philip M., Arthur Bernstein, and Michael Kifer. Databasesand Transaction Processing: An Application-Oriented Approach.Upper Saddle River, N.J.: Addison-Wesley, 2002.Little, Mark, Jon Maron, and Greg Pavlik. Java Transaction Processing:Design and Implementation. Upper Saddle River, N.J.:Prentice Hall PTR, 2004.treeThe tree is a data structure that consists of individual intersectionscalled nodes. The tree normally starts with a singleroot node. (Unlike real trees, data trees have their root atthe top and branch downward.) The root connects to oneor more nodes, which in turn branch into additional nodes,often through a number of levels. (A node that branchesdownward from another node is called that node’s childnode.) A node at the bottom that does not branch any furtheris called a terminal node or sometimes a leaf.Trees are useful for expressing many sorts of hierarchicalstructures such as file systems where the root of a diskholds folders that in turn can hold files or additional folders,and so on down many levels. (A corporate organizationchart is a noncomputer example of a hierarchical tree.)The most common type of tree used as a data structureis the binary tree. A binary tree is a tree in which nonode has more than two child nodes. To move through dataIn a binary tree each node either has two branch (child) nodes oris a terminal node. Here a binary tree is shown with the equivalentrepresentation in an array of memory locations. Notice that thenumbers are stored level by level (50 in the top level, 25 and 75 inthe second level, and so on.) Null would be a special value (suchas -1) representing an empty node.

480 trends and emerging technologiesFor efficiency it’s important to keep all branches of a treeapproximately the same length. A B-tree (balanced tree) isdesigned to automatically optimize itself in this way.Trees lend themselves to game programs where a seriesof moves and their possible replies must be explored tovarying levels. A chess program will typically create a treefrom the current position, but use various criteria to determinewhich moves should be explored beyond just a fewlevels, thus “pruning” the game tree.Further ReadingBrookshear, J. Glenn. Computer Science: An Overview. 9th ed. Boston:Addison-Wesley, 2006.Lafore, Robert. Data Structures & Algorithms in Java. 2nd ed. Indianapolis:Sams, 2002.Parlante, Nick. “Binary Trees.” Available online. URL: http://cslibrary.stanford.edu/110/BinaryTrees.html. Accessed August23, 2007.trends and emerging technologiesBecause of the complexity of computer systems, software,and business models, it is easy to “fail to see the forest forthe trees.” Stepping back once in a while to see what ischanging (or likely to change) is recommended. Such a perspectiveis particularly useful for professionals who need toperiodically evaluate their skills against the market, investors,venture capitalists, journalists, and educators.It is nearly a commonplace to say that the future is comingat an accelerating rate (for the ultimate speculation, seesingularity, technological). What adds to the challengeis the way each new technology (and social adaptation)has multiple consequences, whether it is social networking,“viral marketing,” or individually targeted, location-awareadvertising. At the same time, attempting to distinguishshort-term hype from genuine trends is always difficult—anyone in the computing field can compile a glossary ofnow-obsolete buzzwords. Thus reading a variety of perspectivesfrom advocates to pundits to critics is essential.Overall TrendsThat said, the following table suggests some activities thatare in transition from a traditional model to one that reflectsemerging technological and social trends.Fromtodesktop PCmobile and pervasive computingwired networkswireless and mobile computingseparate handling of media integrated media serversbroadcastinguser-driven, customizable channelsof mediauser as consumer user as contributor and sharerindividual consumers social networkingsoftware as product software as serviceproprietary codeopen sourceinterface-driven tasks search-driven interfacesarbitrarily organized data semantically retrievableinformation.e-commerceintegration of online and traditionalchannelsFor more information about emerging trends, see thefollowing entries: digital convergence, open-sourcemovement, service-oriented architecture, smartbuildings and homes, social networking, ubiquitouscomputing, user-created content, Web 2.0 andbeyond, Web services.Further ReadingHaskin, David. “Don’t Believe the Hype: The 21 Biggest TechnologyFlops.” Computerworld, April 4, 2007. Available online.URL: http://www.computerworld.com/action/article.do?articleId=9012345&comm and=viewArticleBasic. AccessedNovember 29, 2007.Piquepaille, Roland. “Emerging Technology Trends” [blog]. ZDNet.Available online. URL: http://blogs.zdnet.com/emergingtech/.Accessed November 29, 2007.Plunkett Research. “Plunkett’s E-Commerce & Internet Industry.”Available online. URL: http://www.plunkettresearch.com/Industries/ECommerceInternet/tabid/151/Default.aspx.Accessed November 29, 2007.———. “Plunkett’s InfoTech, Computers & Software Industry.”Available online. URL: http://www.plunkettresearch.com/Industries/InfoTechComputersSoftware/tabid/152/Default.aspx. Accessed November 29, 2007.Seidensticker, Bob. Future Hype: The Myths of Technology Change.San Francisco: Berrett-Koehler, 2006.trust and reputation systemsTrust and reputation are inherently connected. Participantsin any transaction (such as respondents to classified ads orparticipants in an online auction) want assurance that theywill receive the promised value in exchange for what theyare giving up. The default anonymity of online transactions(see anonymity and the Internet) presents a challenge:How does one obtain information about someone’s reputation(how he or she has behaved previously) and thus beassured of his or her reliability?One solution is to collect and characterize the experiencesof participants in previous transactions with thatperson or entity. For an auction (see auctions, online andeBay), the system can solicit and tabulate ratings (“feedback”)by participants in each transaction. However, thiskind of simple system must guard against being subvertedby people who create false identities (fronts) and transactionsand use them to inflate the feedback score.A more sophisticated reputation system can be used forranking Web pages, contributions (such as blogs or productreviews), or other works. Instead of giving each participantthe same single “vote,” the feedback is weighted accordingto the responder’s own reputation. Thus if a numberof people whose own product reviews have been highlyrecommended also recommend another review, that reviewwill be much more highly rated. Examples of this sort ofsystem include the PageRank algorithm used by Google,the consumer review site Epinions.com, and the “techie”favorite Slashdot.Developing a trust and reputation system that is effectivebut unobtrusive is particularly important for the collaborativecreation of content such as for search enginesand wikis (see user-created content and wikis andWikipedia).

Turing, Alan Mathison 481Online attacks on reputation (defamation) are also agrowing problem for both businesses and individuals. Evenif the perpetrator is legally prosecuted or otherwise forcedto stop, removing the defamatory material (and links to it)can be difficult, since the material may have been extensivelycached, archived, or otherwise copied. Thus consultantsin “reputation management” have begun to offer theirservices to the victims of undeserved negative reputations.(This includes optimizing for search engines so that negativematerial will be pushed to the bottom of the results.)Further ReadingDellarocas, Chrysanthos. “Reputation Mechanisms” [overviewand resources]. University of Maryland, R. H. Smith School ofBusiness. Available online. URL: http://www.washingtonpost.com/wp-dyn/content/article/2007/07/01/AR2007070101355.html? hpid=artslot. Accessed November 29, 2007.Kinzie, Susan, and Ellen Nakashima. “Calling In Pros to RefineYour Google Image.” Washington Post.com, July 2, 2007.Available online. URL: http://www.washingtonpost.com/wp-dyn/content/article/2007/07/01/AR2007070101355.html?hpid=artslot. Accessed November 29, 2007.Masum, Hassan, and Yi-Cheng Zhang. “Manifesto for the ReputationSociety.” First Monday, vol. 9 (July 2004). Availableonline. URL: http://www.firstmonday.org/issues/issue9_7/masum/index.html. Accessed November 29, 2007.Solove, Daniel J. The Future of Reputation: Gossip, Rumor, and Privacyon the Internet. New Haven, Conn.: Yale University Press,2007.Trust Metrics Evaluation Project. Available online. URL: http://www.trustlet.org/wiki/Trust_Metrics_Evaluation_project.Accessed November 29, 2007.Turing, Alan Mathison(1912–1954)BritishMathematician, Computer ScientistAlan Turing’s broad range of thought pioneered manybranches of computer science, ranging from the fundamentaltheory of computability to the question of what mightconstitute true artificial intelligence.Turing was born in London on June 23, 1912. His fatherworked in the Indian (colonial) Civil Service, while hismother came from a family that had produced a number ofdistinguished scientists. As a youth Turing showed greatinterest and aptitude in both physical science and mathematics.When he entered King’s College, Cambridge, in1931, his first great interest was in probability, where hewrote a well-regarded thesis on the Central Limit Theorem.Turing’s interest then turned to the question of whatproblems could be solved through computation (see computabilityand complexity). Instead of pursuing conventionalmathematical strategies, he re-imagined the problemby creating the Turing Machine, an abstract “computer”that performs only two kinds of operations: writing ornot writing a symbol on its imaginary tape, and possiblymoving one space on the tape to the left or right. Turingshowed that from this simple set of states (see finitestate machine) any possible type of calculation could beconstructed. His 1936 paper “On Computable Numbers”together with another researcher’s different approach (seeChurch, Alonzo) defined the theory of computability.Turing then came to America, studied at Princeton University,and received his Ph.D. in 1938.Turing did not remain in the abstract realm, however,but began to think about how actual machines could performsequences of logical operations. When World War IIerupted, Turing returned to Britain and went into servicewith the government’s Bletchley Park code-breaking facility.He was able to combine his previous work on probabilityand his new insights into computing devices to help analyzecryptosystems such as the German Enigma cipher machineand to design specialized code-breaking machines.As the war drew to an end, Turing’s imagination broughttogether what he had seen of the possibilities of automaticcomputation, and particularly the faster machines thatwould be made possible by harnessing electronics ratherthan electromechanical relays. In 1946, he received a Britishgovernment grant to build the ACE (Automatic ComputingEngine). This machine’s design incorporated advanced programmingconcepts such as the storing of all instructionsin the form of programs in memory without the mechanicalsetup steps required for machines such as the ENIAC.Another important idea of Turing was that programs couldmodify themselves by treating their own instructions justlike other data in memory. However, the engineering of theadvanced memory system led to delays, and Turing left theproject in 1948 (it would be completed in 1950). Turing alsocontinued his interest in pure mathematics and developed anew interest in a completely different field, biochemistry.Turing’s last and perhaps greatest impact would come inthe new field of artificial intelligence. Working at the Universityof Manchester, Turing devised a concept that becameknown as the Turing Test. In its best-known variation, thetest involves a human being communicating via a Teletypewith an unknown party that might be either another personor a computer. If a computer at the other end is sufficientlyable to respond in a humanlike way, it may fool the humaninto thinking it is another person. This achievement couldin turn be considered strong evidence that the computer istruly intelligent. Since Turing’s 1950 article computer programssuch as ELIZA and Web “chatterbots” have been ableto temporarily fool people they encounter, but no computerprogram has yet been able to pass the Turing Test whensubjected to extensive probing questions by a knowledgeableperson.Alan Turing had a secret that was very dangerous in thattime and place: He was gay. In 1952, the socially awkwardTuring stumbled into a set of circumstances that led to hisbeing arrested for homosexual activity, which was illegaland heavily punished at the time. The effect of his trial andforced medical “treatment” suggested that his death fromcyanide poisoning on June 7, 1954, was probably a suicide.Alan Turing’s many contributions to computer sciencewere honored by his being elected a Fellow of the BritishRoyal Society in 1951 and by the creation of the prestigiousTuring Award by the Association for Computing Machinery,given every year since 1966 for outstanding contributionsto computer science.

482 Turkle, SherryFurther ReadingHenderson, Harry. Modern Mathematicians. New York: Facts OnFile, 1996.Herken, R. The Universal Turing Machine. 2nd ed. London: OxfordUniversity Press, 1988.Hodges, A. Alan Turing: The Enigma. New York: Simon & Schuster,1983. Reprinted New York: Walker, 2000.———. “Alan Turing” [Web site]. Available online. URL: http://www.turing.org.uk/. Accessed August 23, 2007.Turing, Alan M. “Computing Machinery and Intelligence.” Mind,vol. 49, 1950, 433–460.———. “On Computable Numbers, with an Application to theEntscheidungsproblem.” Proceedings of the London MathematicalSociety, vol. 2, no. 42, 1936–1937, 230–265.———. “Proposed Electronic Calculator.” In Carpenter, B. E. andR. W. Doran, eds. A. M. Turing’s ACE Report of 1946 and otherPapers. Charles Babbage Institute Reprint Series in the Historyof Computing, vol. 10. Cambridge, Mass.: MIT Press,1986.Turkle, Sherry(1948– )AmericanScientist, WriterFrom the time cyberspace began to become a reality in the1980s, Sherry Turkle has been a pioneer in studying thepsychological, social, and existential effects of computeruse and online interaction.Turkle was born Sherry Zimmerman on June 18, 1948,in Brooklyn, New York. After graduating from AbrahamLincoln High School as valedictorian in 1965, she enrolledin Radcliffe College (which later became part of HarvardUniversity) in Cambridge, Massachusetts. However, whenshe was a junior her mother died, she quarreled with herstepfather, and dropped out of Radcliffe because she was nolonger able to keep up with her studies.Turkle then went to France, which by the late 1960s hadbecome the scene of social and intellectual unrest. A newmovement called poststructuralism was offering a radicalcritique of modern institutions. Turkle became fascinatedby its ideas and attended seminars by such key figures asMichael Foucault and Roland Barthes. In particular, personalexperience and intellectual interest joined in spurringher to investigate personal identity in the modern world.Poststructuralism and postmodernism see identity assomething constructed by society or by the individual, notsomething inherent. The new philosophers spoke of peopleas having multiple identities between which they couldmove “fluidly.” In being able to try on a new identity forherself, Turkle could see the applicability of these ideasto her own life and began to explore how they may alsoexplain the changes that were sweeping through society.Turkle decided to return to the United States to resumeher studies. In 1970 she received an A.B. degree in socialstudies, summa cum laude, from Radcliffe. After workingfor a year with the University of Chicago’s Committee onSocial Thought, she enrolled in Harvard, receiving an M.A.in sociology in 1973. She went on to receive her doctoratein sociology and personality psychology in 1976, writingabout the relationship between Freudian thought and themodern French revolutionary movements.Psychology of CyberspaceAfter getting her Harvard Ph.D. Turkle accepted a positionas an assistant professor of sociology at nearby MIT. Hereshe found a culture as exotic as that of the French intellectuals,but seemingly very different. In encountering theMIT hackers that would later be described in Steven Levy’sbook Hackers, Turkle became intrigued by the way the studentswere viewing all of reality (including their own emotions)through the language of computers.For many of the MIT computer students, the mindwas just another computer, albeit a complicated one. Anemotional overload required “clearing the buffer,” andtroubling relationships should be “debugged.” Fascinated,Turkle began to function as an anthropologist, takingnotes on the language and behavior of the computer students.In her second book, The Second Self: Computers andthe Human Spirit (1984), Turkle says that the computer forits users is not an inanimate lump of metal and plastic, butan “evocative object” that offers images and experiencesand draws out emotions. She also explained that the computercould satisfy deep psychological needs, particularlyby offering a detailed but structured “world” (as in a videogame) that could be mastered, leading to a sense of powerand security.Although the computer culture of the time was largelymasculine, Turkle also observed that this evocative natureof technology could also allow for a “soft approach” basedon relationship rather than rigorous logic. This “feminine”approach usually met with rejection. Turkle believed thatthis message had to be changed if girls were not to be leftbehind in the emerging computer culture.Turkle had already observed how computer activities(especially games) often led users to assume new identities,but she had mainly studied stand-alone computer use. Inthe 1990s, however, online services and the Internet in particularincreasingly meant that computer users were interactingwith other users over networks. In her 1995 bookLife on the Screen, Turkle takes readers inside the fascinatingworld of the MUD, or multi-user dungeon (see onlinegames). In this fantasy world created by descriptive text,users could assume any identity they wished. An insecureteenage boy could become a mighty warrior—or perhaps aseductive woman. A woman, by assuming a male identity,might find it easier to be assertive and would avoid the sexismand harassment often directed at females.The immersive world of cyberspace offers promises, perils,and potential, according to Turkle. As with other media,the computer world can become a source of unhealthyescapism, but it can also give people practice in using socialskills in a relatively safe environment, although there canbe difficulty in transferring skills learned online to a faceto-faceenvironment.Although the computer has provided a new mediumfor the play of human identity, Turkle has pointed out thatthe question of identity (and the reality of multiple identities)is inherent in the postmodern world. Looking to the

typography, computerized 483future, Turkle suggests that the boundary between cyberspaceand so-called real life is vanishing, forcing people toconfront the question of what “reality” means. Meanwhile,she remains concerned about the paradox in which peoplemay be becoming at once more connected and more alienatedthan ever before.Turkle married artificial intelligence pioneer and educatorSeymour Papert; the marriage ended in divorce. Shecontinues today at MIT as a professor of the sociology ofscience and as director of the MIT Initiative on Technologyand Self. She has received a number of fellowships, includinga Rockefeller Foundation fellowship (1980), a Guggenheimfellowship (1981), Fellow of the American Associationfor the Advancement of Science (1992), and World EconomicForum Fellow (2002).In 1984 Turkle was selected Woman of the Year by Ms.magazine, and she has made a number of other lists ofinfluential persons such as the “Top 50 Cyber Elite” of TimeDigital (1997) and Time Magazine’s Innovators of the Internet(2000).Further Reading“Sherry Turkle” [Home page]. Available online. URL: http://web.mit.edu/sturkle/www/. Accessed November 29, 2007.Turkle, Sherry. “Can You Hear Me Now?” Forbes, May 7, 2007, p.176.———. Evocative Objects: Things We Think With. Cambridge,Mass.: MIT Press, 2007.———. Life on the Screen: Identity in the Age of the Internet. NewYork: Simon and Schuster, 1995.———. The Second Self: Computers and the Human Spirit. NewYork: Simon and Schuster, 1984.typography, computerizedThe more than five-century-old art of typography (thedesign, arrangement, and setting of printing type) wastransformed in the latter part of the 20th century by digitaltechnology. With the exception of some traditional pressesdevoted to the fine book market, nearly all type used todayis designed and set by computer.Most users are familiar with the typefaces distributedwith their operating system and software, such as the popularAdobe and TrueType (see Adobe systems and font).Many such font designs are based on (and sometimes namedafter) traditional typefaces, modified for readability usingtypical displays and printers.For control of composition, there are three overlappinglevels of software, ranging from easiest to use (but mostlimited) to most complex, versatile, and precise. Modernword processors such as Microsoft Word and Open Officeprovide enough control for many types of shorter documents(see word processing). Desktop publishing softwareadds facilities suitable for layout of fliers, brochures,newsletters, and similar publications that often mix textand graphics (see desktop publishing).More elaborate documents such as books, magazines,and newspapers require more sophisticated facilitiesto control the layout and flow of text. Some traditionalchoices include LaTex (for the Tex typesetting program),used particularly by scientists and other academics, andthe older troff and its offshoots on UNIX systems. Morerecent programs include Quark, FrameMaker, PageMaker,and InDesign. Related utilities often used in digital typographyinclude font editors (for design and modification) andutilities to convert fonts from one format to another.Further ReadingBringhurst, Robert. The Elements of Typographic Style. Version 3.0.Point Roberts, Wash.: Hartley & Marks, 2004.Ellison, Andy. The Complete Guide to Digital Type: Creative Use ofTypography in the Digital Arts. New York: Collins Design, 2004.FontLab. Available online. URL: http://www.fontlab.com/i.Accessed November 30, 2007.FontSite: Digital Typography & Design. Available online. URL:http://www.fontsite.com/. Accessed November 30, 2007.Knuth, Donald E. Computers and Typesetting. 5 vols. Upper SaddleRiver, N.J.: Addison-Wesley Professional, 2001.Page Layout Programs. Aeonix Publishing Group. Availableonline. URL: http://www.aeonix.com/pagelay.htm. AccessedNovember 30, 2007.Troff: The Text Processor for Typesetters. Available online. URL:http://troff.org/. Accessed November 30, 2007.

Uubiquitous computingTraditionally people have thought of computers as discretedevices (such as a desktop or handheld device), used forspecific purposes such as to send e-mail or browse the Web.However, many researchers and futurists are looking towarda new paradigm that many believe is rapidly emerging. Ubiquitous(or pervasive) computing focuses not on individualcomputers and tasks but on a world where most objects(including furniture and appliances) have the ability to communicateinformation. (This has also been called “the Internetof things.”) This can be viewed as the third phase in aprocess where the emphasis has gradually shifted from individualdesktops (1980s) to the network and Internet (1990s)to mobile presence and the ambient environment.Some examples of ubiquitous computing might include:• picture frames that display pictures attuned to theuser’s activities• “dashboard” devices that can be set to display changinginformation such as weather and stock quotes• parking meters that can provide verbal directions tonearby attractions• kiosks or other facilities to provide verbal cues toguide travelers, such as through airports• home monitoring systems that can sense and dealwith accidents or health emergenciesUbiquitous computing greatly increases the ability ofpeople to seamlessly access information for their dailyactivities, but the fact that the user is in effect “embedded”in the network can also raise issues of privacy and thereceiving of unwanted advertising or other information (seeprivacy in the digital age).An early center of research in ubiquitous computing wasXerox PARC, famous for its development of graphical userinterfaces (particularly the work of Mark Weiser). Today amajor force is MIT (see MIT Media Lab), especially its ProjectOxygen, which explores networks of embedded computers.This challenging research area brings together aspectsof many other fields (see artificial intelligence, distributedcomputing, psychology of computing, smart buildings andhomes, touchscreen, user interface, and wearable computers).Note that while the user’s experience of ubiquitouscomputing might be similar in some ways to that of virtualreality, the latter puts the user into a computer-generatedworld, while the former uses computing power to enhancethe user’s connections to the outside world (see virtualreality).Further ReadingGreenfield, Adam. Everywhere: The Dawning Age of UbiquitousComputing. Berkeley, Calif.: New Riders, 2006.Igoe, Tom. Making Things Talk: Practical Methods Connecting PhysicalObjects. Sebastapol, Calif.: O’ Reilly, 2007.MIT Project Oxygen. Available online. URL: http://www.oxygen.lcs.mit.edu/. Accessed November 30, 2007.Morville, Peter. Ambient Findability: What We Find Changes WhoWe Become. Sebastapol, Calif.: O’Reilly, 2005.Terdiman, Daniel. “Meet the Metaverse, Your New Digital Home.”CNET News. Available online. URL: http://news.com.com/Meet+the+metaverse%2C+your+new+digital+home/2100-1025_3-6175973.html. Accessed November 30, 2007.484

UNIX 485Vasilakos, Athanasios, and Witold Pedrycz, eds. Ambient Intelligence,Wireless Networking, and Ubiquitous Computing. Boston:Artech House, 2006.UNIXBy the 1970s, time-sharing computer systems were in use atmany universities and engineering and research organizations.Such systems, often running on computers such asthe PDP series (see minicomputer), required a new kindof operating system that could manage the resources foreach user as well as the running of multiple programs (seemultitasking).An elaborate project called Multics had been begun inthe 1960s in an attempt to create such an operating system.However, as the project began to bog down, two of its participants,Ken Thompson and Dennis Ritchie (see Ritchie,Dennis) decided to create a simple, more practical operatingsystem for their PDP-7. The result would become UNIX,an operating system that today is a widely used alternativeto proprietary operating systems such as those from IBMand Microsoft.ArchitectureThe essential core of the UNIX system is the kernel, whichprovides facilities to organize and access files (see kerneland file), move data to and from devices, and controlthe running of programs (processes). In designing UNIX,Thompson deliberately kept the kernel small, noting that hewanted maximum flexibility for users. Since the kernel wasthe only part of the system that could not be reconfigured orreplaced by the user, he limited it to those functions that reliabilityand efficiency dictated be handled at the system level.Another way in which the UNIX kernel was kept simplewas through device independence. This meant that insteadof including specific instructions for operating particularmodels of terminal, printers, or plotters within the kernel,generic facilities were provided. These could then be interfacedwith device drivers and configuration files to controlthe particular devices.A UNIX system typically has many users, each of whommay be running a number of programs. The interface thatprocesses user commands is called the shell. It is importantto note that in UNIX a shell is just another program,so there can be (and are) many different shells reflectingvarying tastes and purposes (see shell). Traditional UNIXshells include the Bourne shell (sh), C shell (csh), and Kornshell (ksh). Modern UNIX systems can also have graphicaluser interfaces similar to those found on Windows andMacintosh personal computers (see user interface).Working with CommandsUNIX systems come with hundreds of utility programs thathave been developed over the years by researchers workingat Bell Labs and campuses such as the University of Californiaat Berkeley (UCB). These range from simple commandsfor working with files and directories (such as cd to set acurrent directory and ls to list the files in a directory) tolanguage compilers, editors, and text-processing utilities.Whatever shell is used, UNIX provides several key featuresfor constructing commands. A powerful system ofpatterns (see regular expression) can be used to find filesthat match various criteria. For a very simple example, thecommand% ls *.docwill list all files in the current directory that end in .doc.(The % represents the command prompt given by the shell.)Most earlier operating systems used special syntax torefer to devices such as the user’s terminal and the printer.UNIX, however, treats devices just like other files. Thismeans that a program can receive its input by opening a terminalfile and send its output to another file. For example:% cat > noteThis is a note.^DThe cat (short for concatenate) command adds the user’sinput to a file called note. The ^D stands for Control-D, thespecial character that marks end-of-file. Once the commandfinishes, there is a file called note on the disk, which can belisted by the ls command:% ls –l note-rw———- 1 hrh well 16 Mar 25 20:16 noteThe contents of the file can be checked by issuinganother cat command:% cat noteThis is a note.Many commands default to taking keyboard input if noinput file is specified. For example, one can type sort followedby a list of words to sort:% sortapplepearorangetangerinelemon^DOnce the input is finished, the sort command outputsthe sorted list:applelemonorangepeartangerineOne of the things that makes UNIX attractive to its usersis the ability to combine a set of commands in order to performa task. For example, suppose a user on a timesharingsystem wants to know which other users are logged on. Thewho command provides this information, but it includes alot of details that may not be of interest. Suppose one justwants the names of the current users. One way to do this isto connect the output of the who command to awk, a scriptinglanguage (see awk and scripting languages).

486 USB% who | awk ' { print $1 }'Here the vertical bar (called a pipe) connects the outputof the first command to the input of the second. Thus, theawk command receives the output of the who command.The statement print $1 tells awk to output the first columnfrom who’s output, which is just the names of the users.The first part of the list looks like this:mnemonicberniekryannanlevgoddessjbradydemaristechgirlThis is fine, but the output might be better if it were sorted.All that’s needed is to add one more pipe to connect the outputof the awk command to the sort command:% who | awk ' {print $1}' | sortaarongaimeealmanacamicusautumnbiscuitbradburnbrianThe ability to redirect input and output and to use pipes toconnect commands makes it easy for UNIX users to createmini-programs called scripts to perform tasks that wouldrequire full-fledged compiled programs on other systems.For example, the preceding command could be put into afile called users, and the file could be set to be executable.Once this is done, all the user has to do to get the user listis to type users at a shell prompt. Today UNIX users have awide choice of powerful scripting languages (see perl andpython).Unix Then and NowThe versatility of UNIX quickly made it the operating systemof choice for most campuses and laboratories, as well asfor many software developers. When PCs came along in thelate 1970s and 1980s, they generally lacked the resources torun UNIX, but developers of PC operating systems such asCP/M and MS-DOS were influenced by UNIX ideas includingthe hierarchical file system with its levels of directories,the use of a command-processing shell, and wildcards formatching filenames.Besides hardware requirements, another barrier to theuse of UNIX by home and business users was that theoperating system was copyrighted by Bell Labs and a UNIXlicense often cost more than the PC to run it on. However,a combination of the efforts of the Free Software Foundation(see Stallman, Richard) and a single inspired programmer(see Torvalds, Linus) resulted in the release ofLinux, an operating system that is fully functionally compatiblewith UNIX but uses no AT&T code and is thus freeof licensing fees (see Linux).Although UNIX has been somewhat overshadowed byits Linux progeny, a variety of open-source versions of traditionalUNIX systems have become available. In 2005 SunMicrosystems released OpenSolaris (based on UNIX SystemV). There is also OpenBSD, derived from the UC BerkeleySoftware Distribution (but with stronger security features),and available for most major platforms. Finally, the continuinginfluence of UNIX can also be seen in the currentgeneration of operating systems for the Apple Macintosh(see os x).Further ReadingBach, Maurice J. The Design of the UNIX Operating System. UpperSaddle River, N.J.: Prentice Hall, 1986.Lucas, Michael W. Absolute OPENBSD: UNIX for the Practical Paranoid.San Francisco: No Starch Press, 2003.OpenBSD. Available online. URL: http://www.openbsd.org/.Accessed August 23, 2007.OpenSolaris Project. Available online. URL: http://www.opensolaris.org/os/. Accessed August 23, 2007.Peek, Jerry, Grace Todino-Gonquet, and John Strang. Learning theUNIX Operating System. 5th ed. Sebastapol, Calif.: O’ReillyMedia, 2002.Robbins, Arnold. UNIX in a Nutshell. 4th ed. Sebastapol, Calif.:O’Reilly Media, 2005.Salus, Peter H. A Quarter Century of UNIX. Reading, Mass.: Addison-Wesley,1994.“Unix Introduction and Quick Reference.” Available online. URL:http://www.decf.berkeley.edu/help/handouts/unix-intro.pdf.Accessed August 23, 2007.USBThe traditional ways to connect a computer to peripheraldevices such as printers are via parallel and serial connections(see parallel port and serial port). Both methodsare standardized and reliable, but by the mid-1990s peoplewanted to connect many more data-hungry devices totheir PCs, including scanners, digital cameras, and externalstorage drives. Besides wanting faster data transfers,system designers looked for a way to connect more deviceswithout having to add more ports to the motherboard.It would also be convenient to be able to plug or unplugdevices without having to reboot the PC. The UniversalSerial Bus (USB) has all these features: It is relatively fastand quite flexible.Introduced in 1996, USB uses a four-wire cable withsmall rectangular connectors. Devices can be connecteddirectly to the host USB hub built into the computer. Alternatively,a second hub can be connected to the host hub,allowing for several devices to share the same connection.(Often for convenience, monitors and other devices nowinclude built-in USB hubs for ease in connecting otherdevices on the desktop.)Two of the four wires carry power from the PCs powersupply (or from a secondary powered hub) to the connecteddevices. The other two wires carry data. The 1s and 0s inthe data are signaled by the difference in voltage betweenthe two wires. (This tends to reduce the effects of outside

user-created content 487electromagnetic interference, since if both wires are affectedsimilarly, the difference between them won’t change.)When a USB device is connected, it creates a voltagechange that causes the USB system in the PC to queryit for identifying information. If the information indicatesthat the device has not been installed, the operating systembegins an installation procedure that can be carried outeither automatically or with a little help from the user (seeplug and play).Once a device is installed, its identifying informationtells the USB system what data rate it can handle. (Somedevices, such as keyboards, don’t need to be very fast, whileothers, such as CD drives, place a premium on speed.) TheUSB system assigns each device an address. The systemfunctions like a miniature token-ring network, sending queriesor commands with tokens identifying the appropriatedevice. The devices respond to requests that have their tokenand in turn send requests when they have data to transmit.The USB system can assign priorities to devices accordingto their need for an uninterrupted flow of data. Arecordable CD (CD-RW) drive, for example, is sensitive tointerruptions in the flow of data, so it is given a high priority.A keyboard sends only a tiny bit of data at a time, and itcan get by with a low priority, requesting service as needed.Other devices such as scanners and printers may handle alarge flow of data, but are not very sensitive to interruptionsand can have a medium priority.The original USB specification allowed for up to 12 MB/sec data transfers. However, the current USB 2.0 specificationallows speeds up to 480 MB/sec, enough to easily handle adigital camera, scanner, and CD-RW drive simultaneously.Today USB connections are also often used to add externalhard drive storage as well as for handy “thumb drives”or “memory sticks” that make it easy to carry one’s documentsand even software from one machine to the next (seeflash drive). Finally, a USB-connected wireless adapter(see Bluetooth and wireless computing) can be themost convenient way to put an older desktop or laptop PCinto communication with the rest of the world.Further ReadingAxelson, Jan. “USB Central” [Web site]. Available online. URL:http://www.lvr.com/usb.htm. Accessed August 23, 2007.———. USB Complete: Everything You Need to Develop Custom USBPeripherals. 3rd ed. Madison, Wisc.: Lakeview Research,2005.———. USB Mass Storage: Designing and Programming Devices andEmbedded Hosts. Madison, Wisc.: Lakeview Research, 2006.ZDNET USB Resources. Available online. URL: http://updates.zdnet.com/tags/USB.html?t=17&s=0&o=0. Accessed August23, 2007.user-created contentTraditional print and broadcast media divide the worldinto two groups: content producers and content consumers.However, as noted by its creator Tim Berners-Lee atits very beginning, the World Wide Web had at least thepotential for users to take an active role in linking existingcontent and contributing their own (see Berners-Lee, Timand World Wide Web). Indeed, Berners-Lee wanted Webclient software to include not only browsing functions buteasy ways for users to create their own Web pages.In reality, early users faced something of a learningcurve, usually having to cope with HTML to some extent,for example. But by the mid-2000s a variety of new mediaof communication had become readily accessible using anordinary Web browser at sites that host the required software.The most prominent applications are blogs (see blogsand blogging) and wikis, particularly Wikipedia (seewikis and Wikipedia).Meanwhile, inexpensive digital still and video camerasand easy-to-use editing software encouraged people to maketheir own media creations. Sites to enable users to upload,share, and comment on their creations have flourished (seeYouTube).The growth of sites such as Facebook and MySpace(see social networking) has also provided new ways forusers from junior high school age on up to create and sharecontent.Applications and IssuesThe effects of this ability to create as well as consume mediaare proving to be far-reaching. YouTube, for example, hasfeatured elaborate documentaries and controversial politicalpieces. Candidates in the 2008 presidential primarycampaign had to deal with a new debate format where voter’squestions, rather than being read by a moderator, arepresented in videos created by the voters themselves.User-created content is also becoming significant inmedia and journalism. Some newspapers are even beginningto experiment with assigning stories to volunteer collaborators—possiblyas a way of coping with diminishingrevenues and budgets for professional journalists.Forms of user-created content are also increasinglyprevalent in the traditional broadcast media. While previouslyexisting only in such forms as talk radio and gameshows, more or less unscripted participation is now foundin reality TV and the endless variants on American Idol.Economists and social scientists are beginning toexplore how a combination of open-source, user-createdcontent, and mass collaboration are changing how informationis assembled and used and even how products aredesigned (see open-source movement).However, user-created content also raises challenges:What kind of journalistic standards might be applied to nonprofessionalreporting and documentaries? (See journalismand computers.) What should be the responsibility of theowner of a venue such as YouTube for content that might violatesomeone’s copyright or be defamatory? The creation ofcontent that contains information about personal identity canalso be problematic from a privacy and security standpoint.Finally, in venues such as online games where users mayhave spent hundreds of hours creating content, the questionof who owns it and what they can do with it is significant.Further ReadingEspejo, Roman. User-Generated Content. (At Issue Series). Farmington,Mich.: Greenhaven Press, 2007.

488 user groupsGarofoli, Joe. “User News Sites Offer Diverse Stories, SomeQuestionable Sources.” San Francisco Chronicle. Availableonline. URL: http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/09/12/MNPDS3RE6.DTL&hw=user+content&sn=001&sc=100. Accessed November 30, 2007.Gillmor, Dan. We the Media: Grassroots Journalism by the People, forthe People. Cambridge, Mass.: O’Reilly, 2004.Hietannen, Herkko, Ville Oksanen, and Vikko Valimaki. CommunityCreated Content: Law, Business, and Policy. Helsinki,Finland: Turre Publishing, 2007.King, Brad. “User-Created Content Comes to TV.” TechnologyReview blogs, December 5, 2006. Available online. URL:http://www.technologyreview.com/blog/editors/17485/.Accessed November 30, 2007.Tapscott, Don, and Anthony D. Williams. Wikinomics: How MassCollaboration Changes Everything. New York: Portfolio, 2006.Vickery, Graham, and Sacha Wunsch-Vincent. Participative Weband User-Created Content: Web 2.0 Wikis and Social Networking.Paris: Organization for Economic Cooperation and Development,2007.user groupsComputer users have always had an interest in finding andsharing information about the systems they are trying touse. As early as 1955, users of the IBM 701 mainframebanded together, in this case to try to influence IBM’s decisionsabout new software. Later, users of minicomputersmade by Digital Equipment Corporation formed DECUS.By the mid-1970s, microcomputer experimenters hadorganized several groups, of which the most influential wasprobably the Homebrew Computer Club, meeting first in agarage in Menlo Park, California, 1975. The group soon wasfilling an auditorium at Stanford University. Members demonstratedand explained their hand-built computer systems,argued the merits of kits such as the Altair, and later, witnessedSteve Wozniak’s prototype Apple I computer.At the other end of the scale, users of UNIX on universitycomputer systems had formed USENIX, the UNIX user’sgroup. A growing system of newsgroups called USENET(see netnews and newsgroups) would soon extendbeyond UNIX concerns to hundreds of other topics.Early PC users had great need for user groups. Technicalsupport was primitive and the variety of computerbooks limited, so the best way to get quirky hardware orbalky software to work was often to ask fellow users, readuser group newsletters, or skim through the great varietyof small publications that catered to users of particular systems.Users could also meet to swap public domain softwaredisks. User groups could be formed around software as wellas hardware. Thus, users could swap spreadsheet templatesor discuss Photoshop techniques.User groups have gradually become less important, orperhaps it is better to say that they have changed theirmode of existence. Starting in the mid-1980s, the modemand bulletin board, on-line services such as CompuServeand later, Web sites offered more convenient access to informationand software without the need to attend meetings.At the same time, the quality and reliability of hardwareand software has steadily improved, even though there isalways a new crop of problems.User groups played a key role in the adoption of newtechnology, much as they had in earlier movements suchas amateur radio. Today it might be said that every userhas the opportunity to join numerous virtual user groups,although the sense of fellowship and mutual explorationmay be somewhat lacking.Further ReadingAssociation of Personal Computer User Groups. Available online.URL: http://www.apcug.org/. Accessed August 23, 2007.Moen, Rick. “Linux User Group HOWTO.” Available online. URL:http://www.linux.org/docs/ldp/howto/User-Group-HOWTO.html. Accessed August 23, 2007.MUG Center: The Mac User Group Resource Site. Available online.URL: http://www.mugcenter.com/. Accessed August 23, 2007.USENIX. Available online. URL: http://www.usenix.org/. AccessedAugust 23, 2007.User Group Network. Available online. URL: http://www.usergroups.net/.Accessed August 23, 2007.WUGNET (Windows Users Group Network). Available online.URL: http://www.wugnet.com/. Accessed August 23, 2007.user interfaceAll computer designers are faced with the question of howusers are going to communicate with the machine in orderto get it to do what they want it to do. User interfaces haveevolved considerably in 60 years of computing.The user interface for ENIAC and other early computersconsisted of switches or plugs for configuring the machinefor a particular problem, followed by loading instructionsfrom punch cards. The mainframes of the 1950s and 1960shad control consoles from which text commands could beentered (see job control language).The time-sharing computers that became popular startingin the 1960s still used only text commands, but theywere more interactive. Users could type commands toexamine directories and files, and run utilities and otherprograms. Starting in the 1970s, UNIX provided a powerfuland flexible way to combine commands to carry out a varietyof tasks interactively or through batch processing (seeunix and shell).The first graphical user interfaces (GUIs) resulted fromexperimental work at the Xerox Palo Alto Research Center(PARC) during the 1970s. Instead of typing commands ata prompt, GUI users can use a mouse to open menus andselect commands, and click on icons to open programs andfiles. For operations that require detailed specifications, astandard dialog box can be presented, using controls suchas check boxes, buttons, text boxes, and sliders.GUIs entered the mainstream thanks to Apple’s Macintoshand Microsoft Windows for IBM-compatible PCs. Bythe mid-1990s, the GUI had supplanted text-based operatingsystems such as MS-DOS for most PC users. Thestrength of the GUI is that it can visually model the wayusers work with objects in the real world. For example, afile can be deleted by dragging it to a trash can icon anddropping it in. Dragging a slider control to adjust the volumefor a sound card is directly analogous to moving aslider on a home stereo system.

user interface 489Because a system like Windows or the Macintosh providesdevelopers with standardized interface objects andconventions, users are able to learn the basics of operatinga new application more quickly. Whereas in the old daysdifferent programs might use slightly different keystrokesor commands for saving a file, Windows users know that invirtually any application they can open the File menu andselect Save, or press Ctrl-S.With the growth of the World Wide Web, interfacedesign has extended to Web pages. Generally, Web pagesuse similar elements to desktop GUIs, but there are somespecial considerations such as browser compatibility,response at differing connection speeds, and the integrationof text and interactive elements.GUIs do have some general drawbacks. An experienceduser of a text-based operating system might be able to typea precise command that could find all files of a given typeon the system and copy them to a backup directory. TheGUI counterpart might involve opening the Search menu,typing a file specification, and making further selectionsand menu choices to perform the copy. Command-drivensystems also provide for powerful scripting capabilities.GUI systems often allow for the recording of keystrokes ormenu selections, but this is less powerful and versatile.Another important consideration is the difficulty thatpeople with certain disabilities may have in using GUI systems.There are a variety of possible solutions, many ofwhich are incorporated in Microsoft Windows, Web browsers,and other software. These include screen magnifier orreader utilities for the visually impaired and alternatives tothe mouse such as head tracker/pointers (see disabled personsand computing).Designers of user interfaces have to consider whether theelements of the system are intuitively understandable andconsistent and whether they can be manipulated in efficientyet natural ways (see also ergonomics of computing).Alternative and Future InterfacesThe marketplace has spoken, and the desktop GUI is nowthe mainstream interface for most ordinary PC users. However,there are a variety of other interfaces that are used forparticular circumstances or applications, such as:• touchscreens (as with ATMs) (see touchscreen)• handwriting or written “gesture” recognition, such ason handheld computers (see handwriting recognition)or for drawing tablets• voice-controlled systems (see speech recognitionand synthesis)• trackballs, joysticks, and touchpads (used as mousealternatives)• virtual reality interfaces using head-mounted systems,sensor gloves, and so on (see virtual reality)Because much interaction with computers is now away fromthe desktop and taking place on laptops, handheld, or palmcomputers, and even in cars, there is likely to be continuingexperimentation with user interface design.Further ReadingArlov, Laura. GUI Design for Dummies. New York: Wiley, 1997.Galitz, Wilbert O. The Essential Guide to User Interface Design: AnIntroduction to GUI Design Principles and Techniques. 3rd ed.Indianapolis: Wiley, 2007.Hobart, John. “Principles of Good GUI Design.” Available online.URL: http://www.iie.org.mx/Monitor/v01n03/ar_ihc2.htm.Accessed August 23, 2007.Johnson, Jeff. GUI Bloopers 2.0: Common User Interface DesignDon’ts and Dos. San Francisco: Morgan Kaufmann, 2007.Krug, Steve. Don’t Make Me Think: A Common Sense Approach toWeb Usability. 2nd ed. Berkeley, Calif.: New Riders, 2005.Stephenson, Neil. In the Beginning Was the Command Line. NewYork: Avon Books, 1999.

VvariableVirtually all computer programs must keep track of a varietyof items of information that can change as a result ofprocessing. Such values might include totals or subtotals,screen coordinates, the current record in a database, or anynumber of other things. A variable is a name given to sucha changeable quantity, and it actually represents the area ofcomputer memory that holds the relevant data.Consider the following statement in the C language:int Total = 0;Variables have several attributes. First, every variablehas a name—Total in this case. Although this name actuallyrefers to an address in memory, in most cases the programmercan use the much more readable name instead ofthe actual address.It is possible to have more than one name for the samevariable by having another variable point to the first variable’scontents, or by declaring a “reference” variable (seepointers and indirection).Each variable has a data type, which might be number,character, string, a collection (such as an array), a datarecord, or some special type defined by the programmer(see data types). With some exceptions (see scriptinglanguages) most modern programming languages requirethat the programmer declare each variable before it is used.The declaration specifies the variable’s type—in the currentexample, the type is int (integer, or whole number).A variable is usually given an initial value by using anassignment statement; in the example above the variableTotal is given an initial value of 0, and the assignment iscombined with the declaration. (Some languages automaticallyassign a default value such as 0 for a number or a nullcharacter for a string, but with other languages failure toassign a value results in the variable having as its valuewhatever happens to be currently stored in the memoryaddress associated with the variable. An explicit assignmentis thus always safer and more readable.)When exactly do variables get set up, and when do theyget their values? This varies with the programming language(see binding). With C and similar languages, a variablereceives its data type when the program is compiled(compile time). The type in turn determines the range ofvalues that the variable can hold (physically based on thenumber of bytes of memory allocated to it). The variable’svalue is actually stored in that location when the program isexecuted (run time).A few languages such as APL and LISP use dynamicbinding, meaning that a data type is not associated with avariable until run time. This makes for flexibility in programming,but at some cost in efficiency of storage andexecution speed.During processing, a variable’s value can changethrough the use of operators in expressions (see operatorsand expressions). Thus, the example value Total might bechanged by a statement such as:Total = Total + Subtotal;When this statement is executed, the following happens:The value of the memory location labeled “Subtotal” isobtained.490

VBScript 491The value of the memory location labeled “Total” isobtained.The two values are added together.The result is stored in the location labeled “Total,” replacingits former value.Scope of VariablesIn early programming languages variables were generallyglobal, meaning that they could be accessed and changedfrom any part of the program. While this practice is convenient,it became riskier as programs became larger and morecomplex. One part of a program might be using a variablecalled Total or Subtotal to keep track of some quantity. Later,another part is written to deal with some other calculation,and uses the same names. The programmer may think of thesecond Total and Subtotal as being quite separate from thefirst, but in reality they refer to the same memory locationsand any change affects both of them. Thus, it’s easy to createunwanted “side effects” when using global variables.Starting in the 1960s and more systematically duringthe 1970s, there was great interest in designing computerlanguages that could better manage the structure and complexityof large programs (see structured programming).One way to do this is to break programs up into more manageablemodules that each deal with some specific task (seeprocedures and functions). Unless explicitly declared tobe global, variables within a procedure or function are localto that unit of code. This means that if two procedures bothhave a variable called Total, changes to one Total do notaffect the other.Generally, in block-structured languages such as Pascala variable is by default local to the block of code in whichit is defined. This means it can be accessed only within thatblock. (Its visibility is said to be limited to that block.) Thevariable will also be accessible to any block that is nestedwithin the defining block, unless another variable with thesame name is declared in the inner block. In that case theinner variable supersedes the outer one, which will not bevisible in the inner block.Some languages such as APL and early versions of LISPdefine scope differently. Since these languages are not blockstructured, scope is determined not by the relationship ofblocks of code but by the sequence in which functions arecalled. At run time each variable’s definition is searchedfor first in the code where it is first invoked, then in whateverfunction called that code, then in the function thatcalled that function, and so on. As with dynamic binding,dynamic scooping offers flexibility but at a considerableprice. In this case, the price is that the program’s effects onvariables will be hard to understand, and the search mechanismslows down program execution. Dynamic scoping isthus not often used today, even in LISP.Global variables were convenient because they allowedinformation generated by one part of a program to beaccessed by any other. However, such accessibility can beprovided in a safer, more controlled form by explicitly passingvariables or their values to a procedure or functionwhen it is called (see procedures and functions).Object-oriented languages provide another way to controlor encapsulate information. Variables describing dataused within a class are generally declared to be private(accessible only within the functions used by the class).Public (i.e., global) variables are used sparingly. The ideais that if another part of the program wants data belongingto a class, it will call a member function of the class, whichwill provide the data without giving unnecessary access tothe class’s internal variables.A final concept that is important for understanding variablesis that of lifetime, that is, how long the definition of avariable remains valid. For efficiency, the runtime environmentmust deallocate memory for variables when they canno longer be used by the program (that is go “out of scope”).Generally, a variable exists (and can be accessed) only whilethe block of code in which it was defined is being executed(including any procedures or functions called from thatblock). In the case of a variable declared in the main program,this will be until the program as a whole reaches itsend statement. For variables within procedures or functions,however, the lifetime lasts only until the procedure or functionends and control is returned to the calling statement.However, languages such as C allow the special keywordstatic to be used for a variable that is to remain in existenceas long as the program is running. This can be useful whena procedure needs to “remember” some information betweenone call and the next, such as an accumulating total.Further ReadingKernighan, Brian W., and Dennis Ritchie. The C Programming Language.2nd ed. Englewood Cliffs, N.J.: Prentice Hall, 1988.Sebesta, Robert W. Concepts of Programming Languages. 8th ed.Boston: Addison-Wesley, 2007.Stroustrup, Bjarne. The C++ Programming Language. special ed.Reading, Mass.: Addison-Wesley, 2000.VBScriptDating back to the mid-1990s, VBScript is a scripting languagedeveloped by Microsoft and based on its popularVisual Basic programming language (see basic and scriptinglanguage). It is also part of the evolution of whatMicrosoft called “active scripting,” based on componentsthat allow outside access to the capabilities of applications.The host environment in which scripts run is providedthrough Windows (as with Windows Script Host) or withinMicrosoft’s Internet Explorer browser.For client-side processing, VBScript can be used to writescripts embedded in HTML pages, which interact with thestandard Document Object Model (see dom) in a way similarto other Web scripting languages (in particular, seeJavaScript). However, VBScript is not supported by popularnon-Microsoft browsers such as Firefox and Opera, sodevelopers generally must use the widely compatible Java-Script instead. VBScript can also be used for processing onthe Web server, particularly in connection with Microsoft’sWeb servers (see active server pages).Because versions of Windows starting with Windows98 include Windows Script Host, VBScripts can also bewritten to run directly under Windows. One unfortunate

492 videoconferencingconsequence was scripts containing worms (such as the ILOVE YOU worm) or other malware and mailed as attachmentsto unwary users.ExamplesVBScript code will be very familiar to users of Visual Basicand generally follows syntax similar to that of other objectorientedlanguages. The canonical “Hello World” programcan be simply written as:WScript.Echo “Hello World!”Where WScript is the object representing the script host.To get user input through a text box, the programmercan write code like this:option explicitdim userInputuserInput = InputBox(“What is your name?:”,“Greetings”)if userInput = “ ” thenMsgbox “You did not write anything or youpressed cancel!”elseMsgBox “Hello, “ & userInput & “.”,vbInformationend ifOf course VBScript has libraries and interfaces to enableit to perform much more complicated tasks, such as queryingdatabases and configuring other aspects of Windowssystems through Windows Management Instrumentation(WMI) and Active Directory Services Interface (ADSI).Although the language (and code using it) will be in usefor years to come, Microsoft is no longer actively developingVBScript, having moved on to a new programming framework(see Microsoft .NET) and focusing on languagessuch as Visual Basic .NET.Further ReadingJones, Don. VBScript, WMI, and ADSI Unleashed. Indianapolis:Sams, 2007.VBScript Sample Scripts. Available online. URL: http://cwashington.netreach.net/depo/default.asp?topic=repository&scripttype =vbscript. Accessed December 2, 2007.VBScript Tutorial. W3Schools. Available online. URL: http://www.w3schools.com/vbscript/default.asp. Accessed December 2,2007.VBScript User’s Guide. Microsoft Developer Network. Availableonline. URL: http://msdn2.microsoft.com/en-us/library/sx7b3k7y.aspx. Accessed December 2, 2007.Wilson, Ed. Microsoft VBScript Step by Step. Redmond, Wash.:Microsoft Press, 2007.videoconferencingThe growth of the global economy has meant that manycompanies have operations in many locations aroundthe world. The time and expense involved in travel haveencouraged the search for alternatives to face-to-face meetings(see telepresence). The added discomfort and uncertaintyrelated to current airline travel is likely to furtherspur this movement.Basic videoconferencing is carried out by using videocameras and microphones to carry the image and voice ofeach person so that it can be seen by all participants. Thevideo and sound data is digitized and transmitted betweenthe participants’ locations, using some existing communicationslink. Although direct satellite technology can beused, it is very expensive. A more practicable alternativeis the use of a proprietary system over special phone lines(such as ISDN or DSL). Increasingly, however, broadbandconnections to the general Internet are used (see also VoIP).This is relatively inexpensive and flexible, but sometimesless reliable because of the effects of network congestion.The quality of imagery depends on the system. Highendsystems, which can cost tens of thousands of dollars,use large, high-definition screens or even special projectionequipment that can give a 3D look to peoples’ faces.Although high-end videoconferencing software and hardwarecan be expensive, there are now a variety of alternativesfor small businesses and individual users. (As of 2002the printing store chain Kinko’s is offering videoconferencingthrough some of its stores for $450/hr.)For smaller, less formal meetings there are more affordablealternatives. Products such as Microsoft NetMeeting,CuSeeMe, and Yahoo Messenger set up user accounts anda directory that makes it easy for users to connect. Otherthan the Internet connection, the only hardware needed is amicrophone and an inexpensive camera (see web cam).Business videoconferencing systems often include the abilityfor participants to view and interact with software applications.This makes it possible not only to view slide shows orother presentations (see presentation software) but to collaborateon creating documents. An “electronic whiteboard”can be used to display not only computer text and graphicsbut also handwritten notes created by participants using electronicdrawing pads. The system can also create a hardcopyrecord of documents developed during the meeting.Besides business meetings and conferences and productroll-outs, videoconferencing can also be used for a varietyof other applications including sales presentations and forconducting focus groups for market research.Videoconferencing is also being used increasingly ineducation. For K-12 classes, a videoconferencing field tripcan take children to a museum or science laboratory thatwould otherwise be too far to visit. Both docent and studentscan see and hear one another, as well as being able tosee exhibits or experiments close up. For college studentsand adults, it is possible to attend classes given by eminentlecturers and participate fully just as though they wereenrolled on campus (see also distance education andcomputers).Further ReadingBarlow, Janelle, Peta Peter, and Lewis Barlow. Smart Videoconferencing:New Habits for Virtual Meetings. San Francisco: Berrett-KoehlerPublishers, 2002.Pachnowski, Lynn M. “Virtual Field Trips Through Teleconferencing.”Learning & Leading with Technology 29, no. 6 (March2002): 10.

virtual community 493Prencipe, Loretta W. “Management Briefing: Do You Know theRules and Manners of an Effective Virtual Meeting?” Info-World 23, no. 18 (April 30, 2001): 46.Spielman, Sue, and Liz Winfield. The Web Conferencing Book. NewYork: AMACOM, 2003.Videoconferencing Product Reviews from PC Magazine. Availableonline. URL: http://www.pcmag.com/category2/0,1874,4836,00.asp. Accessed August 23, 2007.Winters, Floyd Jay, and Julie Manchester. Web Collaboration UsingOffice XP and NetMeeting. Upper Saddle River, N.J.: PrenticeHall, 2002.video editing, digitalWhen videotape first became available in the 1950s, recorderscost thousands of dollars and could only be affordedby TV studios. Today the VCR is inexpensive and ubiquitous.However, it is hard to edit videotape. Tape is a linearmedium, meaning that to find a given piece of videothe tape has to be moved to that spot. Removing or addingsomething involves either physically splicing the tape(as is done with film) or more commonly, feeding in tapefrom two or more recorders onto a destination tape. Besidesbeing tedious and limited in capabilities, “linear editing” bycopying loses a bit of quality with each copying operation.Today, however, it is easy to shoot video in digital form(see photography, digital) or to convert analog video intodigital form. Digital video is a stream of data that representssampling of the source signal, such as from the chargecoupleddevice (CCD) that turns light photons into electronflow in a digital camera or digital camcorder. This processinvolves either software or hardware compression forstorage and decompression for viewing and editing (sucha scheme is called a CODEC for “compression/decompression”).The most widely used formats include DV (DigitalVideo) and MPEG (Motion Picture Expert Group), whichhas versions that vary in the amount of compression andthus fidelity.In a turnkey system, the input source is automaticallydigitized and stored. In desktop video using a PC, a videocapture card must be installed. The card turns the analogvideo signal into a digital stream. The most commonlyused interface to bring video into a PC is IEE1394, betterknown as FireWire, which has the high bandwidth neededto transfer video data.Once the video is captured, it can be stored in framebuffers in memory and edited in various ways using a varietyof software. Expensive turnkey systems come withadvanced software, while desktop video users can choosefrom products such as Media Studio Pro or Adobe Premiere.The editing interface usually has a timeline and thumbnailsshowing the location of key frames in the sequence. Individualclips can be extracted and tweaked with motion andtransition effects; a variety of filters (see plug-in) can beapplied to the video. The accompanying sound track(s) canalso be edited. Once things look right, the software is toldto render (create) the finished video and save it to disk.The ever-increasing processing power and disk capacityof today’s PC is likely to make real-time video editing morefeasible. This means that video can be played back directlyfrom the edited timeline without transitions or effectshaving to be rendered first. Digital video cameras are alsolikely to increase in picture quality. Already desktop videois proving to be an affordable, viable alternative to expensiveturnkey systems for many applications.Meanwhile, like digital photography, digital video is rapidlybecoming a creative medium for the masses, aided byeasy-to-use basic software for Macintosh (such as iMovie)and numerous products for Windows. Another driver forthe proliferation of this medium is the ease with which videoscan be uploaded and shared (see user-created contentand YouTube).Further ReadingBrandon, Bob. The Complete Digital Video Guide: A Step-by-StepHandbook for Making Great Home Movies Using Your DigitalCamcorder. Pleasantville, N.Y.: Readers Digest, 2005.Digital Video Editing. Available online. URL: http://videoediting.digitalmedianet.com/. Accessed August 23, 2007.Digital Video Resources. Available online. URL: http://www.manifest-tech.com/links/mmtech.htm. Accessed August 23,2007.Goodman, Robert M., and Patrick McCrath. Editing DigitalVideo: The Complete Creative and Technical Guide. New York:McGraw-Hill, 2003.Pogue, David. iMovie 6 & iDVD: The Missing Manual. Sebastapol,Calif.: O’Reilly Media, 2006.Underahl, Keith. Digital Video for Dummies. Hoboken, N.J.: Wiley,2006.virtual communityBack in the mid-19th century, a number of technical professionalsbegan to “chat” online without meeting physically—theywere telegraph operators who relayed messagesacross the growing web that one author has called “TheVictorian Internet.” When computer networking began togrow in the 1970s, its own pioneers used facilities such asnewsgroups (see netnews and newsgroups) to discuss avariety of topics. By the early 1980s, users were interactingon-line in complex fantasy games called MUDs (Multi-UserDungeons, or Dimensions) or MOOs (Muds, Object-Oriented).A little later, bulletin boards and especially systemssuch as the WELL (Whole Earth ’Lectronic Link) based inthe San Francisco Bay Area (see bulletin board and conferencingsystems) provided long-term outlets for peopleto share information and interact on-line.Looking at the WELL, a writer named Howard Rheingoldintroduced the term virtual community in a 1993 book. Heexplored the ways in which a sufficiently compelling and versatiletechnology encouraged people to form long-term contacts,form personal relationships, and carry out feuds. Whenon-line, participants experience such a venue as the WELL asa place that becomes almost as tangible (and often as “real”)as a physical place such as a small town or corner bar.Virtual community members who live in the same geographicalarea sometimes do get together physically (theWELL has had picniclike “WELL Office Parties” for manyyears). Members can band together to support a colleaguewho faces a crisis such as the life-threatening illness of ason (on the WELL, blank postings called beams are often

494 virtualizationused as an expression of sympathy). The virtual communitycan also serve as a rallying point following a physicaldisaster such as the 1989 earthquake in the San FranciscoBay Area. On a daily basis, virtual communities can oftenprovide help or advice from a remarkable variety of highlyqualified experts.Virtual communities have their share of human foiblesand worse. A virtual world that is compelling enough toimmerse participants for hours on end is also powerfulenough to engage emotions and expose vulnerabilities.For example, in a MUD called LambdaMOO one participantused descriptive language to have his game character“rape” a female character created by another participant,inflicting genuine distress. Like physical communities,virtual communities must evolve rules of governance, andactions in a virtual community can have real-world legalconsequences.Critics such as Clifford Stoll have argued that virtualcommunities are not only not a substitute for “true” physicalcommunity, but also may be further fragmenting neighborhoodsand isolating people. (On the other hand, peoplewho are already physically isolated, such as rural folk andthe elderly or disabled, may find an outlet for their socialneeds in a virtual community.) Certainly the “bandwidth”in terms of human experience is less in a virtual communitythan in a physical community. Ideally, individualsshould cultivate a mixture of virtual and physical communityrelationships.Like a number of “virtual” concepts, virtual communityis gradually blending into everyday life and thus becomingless distinct as an idea. Millions of people now participatein a form of virtual community through games such as SecondLife (see online games). Young people keep constantlyin touch through a web of text messages (see flash mobsand texting and instant messaging). Finally, the popularityof sites such as MySpace and Facebook may be partlydue to the seamless way they bring together conventionalsocial ties and their virtual extensions (see social networking).Further ReadingBarnes, S. B. On-line Connections: Internet Personal Relationships.Cresskill, N.J.: Hampton Press, 2000.Dibbel, J. “Rape in Cyberspace: How an Evil Clown, a HaitianTrickster Spirit, Two Wizards and a Cast of Dozens Turned aDatabase into a Society.” The Village Voice, Dec. 21, 1993, 39.———. My Tiny Life: Crime and Passion in a Virtual World. NewYork: Henry Holt, 1998.Powazek, Derek. Design for Community: The Art of Connecting RealPeople in Virtual Places. Berkeley, Calif.: New Riders, 2001.Renninger, K. Ann, and Wesley Shumar, eds. Building Virtual Communities:Learning and Change in Cyberspace. New York: CambridgeUniversity Press, 2002.The Well. Available online. URL: http://www.well.com. AccessedAugust 23, 2007.Rheingold, Howard. The Virtual Community: Homesteading on theElectronic Frontier. 2nd ed. Reading, Mass.: Addison-Wesley,1993.———. “Howard Rheingold Home Page.” http://www.rheingold.com/Turkle, Sherry. Life on the Screen: Identity in the Age of the Internet.New York: Simon & Schuster, 1995.virtualizationOne of the most powerful tools for understanding andmanipulating a complex system is creating models or representationsthat simplify (while retaining the essentials)or that provide other useful ways of looking at the system.This ability to translate systems into representations is usedin many fields, and probably dates back to the first cavepaintings of our prehistoric ancestors.In the computing field, virtualization involves the creationof a working model or representation of one systemwithin a different system. This idea has been widely usedin the field since the 1960s. Some applications of virtualizationinclude:• An appropriate model of a system (such as a programmingframework—see application programminginterface) that hides unneeded details canmake it easier for programmers to understand andaccess its functions (see design patterns and modelinglanguages).• A compiler for a language that compiles all programsto an intermediate representation (such as “bytecode”).A virtual machine running on each kind ofplatform can then run the code, taking care of thedetails required by the host hardware (see compilerand Java).• A virtual machine created in software can be designedto perform all the functions available on a particularhardware platform or operating system, allowing softwareto be run on a system different from the onefor which it was originally written (see emulation).For example, there are a number of virtualizationprograms (such as VMWare for PCs) that can createseparate areas in memory, each running a differentoperating system, such as a version of Windows orLinux.• multiple processors or entire computers can betreated as a single entity for processing a program,with software designed to assign threads of executionto physical processors and to coordinate the use ofshared data (see grid computing).• A physical device such as a disk drive can be madeto appear as several separate devices to the operatingsystem (for better organization of data). Similarly,many servers can run on the same physical machine.Conversely, multiple drives can appear to be a singlelogical device while providing redundancy and errorrecovery (see raid).• A secure “virtual private network” can be createdwithin the larger public Internet. The virtual systemtakes care of encrypting and transmitting datathrough the physical network.Social VirtualizationThe concept of virtualization can also be applied to howwork involving computers is being conceptualized and

virtual reality 495organized in the modern world (see globalization andthe computer industry and ubiquitous computing). A“virtual office” or even “virtual corporation” is a businessentity that is not tied to a physical location, but uses networks,communications technology, and facilities such asvideo conferencing to keep workers in touch. Alternatively,several organizations can share the same physical space(such as for mail or shipping) while maintaining their separateidentities.Similarly, people can form long-lasting social networkswhile meeting physically seldom (if at all)—see socialnetworking and virtual community.Further ReadingBrown, M. Katherine. Managing Virtual Teams: Getting the Mostfrom Wikis, Blogs, and Other Collaborative Tools. Plano, Tex.:Wordware, 2007.Golden, Bernard. Virtualization for Dummies. Indianapolis: Wiley,2007.Goldworm, Barb, and Anne Skamarock. Blade Servers and Virtualization:Transforming Enterprise Computing while CuttingCosts. Indianapolis: Wiley, 2007.Smith, James E., and Ravi Nair. Virtual Machines: Versatile Platformsfor Systems and Processes. San Francisco: MorgannKaufmann, 2005.Virtualization [news]. NetworkWorld. Available online. URL:http://www.networkworld.com/topics/virtualization.html.Accessed December 2, 2007.Virtualization News Digest. Available online. URL: http://www.virtualization.info/. Accessed December 2, 2007.Wolf, Chris, and Erick M. Halter. Virtualization: From the Desktopto the Enterprise. Berkeley, Calif.: Apress, 2005.virtual realityAs the graphics and processing capabilities of computers grewincreasingly powerful starting in the 1980s, it became possibleto think in terms of creating a 3D environment that wouldnot only appear to be highly realistic to the user, but alsowould respond to the user’s natural motions in realistic ways.This idea is not that new in itself. Starting as early as the1930s, the military built mechanical flight trainers or simulatorsthat could create a somewhat realistic experience ofwhat a pilot would see and feel during flight. More sophisticatedversions of these mechanical simulators helped theUnited States train the tens of thousands of pilots it neededduring World War II while reducing the resources neededfor actual flight hours. Today the military continues to pioneerthe use of realistic computerized simulators to trainA NASA researcher wearing an early virtual reality (VR) outfit, including head-mounted display and gloves whose position can betracked. (NASA photo)

496 VoIPtank crews and even individual soldiers in the field (seemilitary applications of computers).Early simulators used “canned” graphics and could notrespond very smoothly to control inputs (such as a pilotmoving stick or rudder). Modern virtual reality, however,depends on the ability to smoothly and quickly generaterealistic 3D graphics. At first such graphics could only begenerated on powerful workstations such as those madeby Sun or Silicon Graphics. However, as anyone who hasrecently played a computer game or simulation knows,there has been great improvement in the graphics availableon ordinary desktop PCs since the mid-1990s.A variety of software and programming tools can beused to generate 3D worlds on a PC (see computer graphics).First released in 1995, a facility called VRML (VirtualReality Modeling Language) is now supported by manyWeb browsers. There are also programming extensions forJava (Java 3D).Modern computer games thus embody aspects of virtualreality in terms of graphics and responsiveness. But trueVR is generally considered to involve a near total immersion.Instead of a screen, a head-mounted display (HMD) isgenerally used to display the virtual world to the user whileshutting out environmental distractions. Typically, slightlydifferent images are presented to the left and right eyes tocreate a 3D stereo effect.The other half of the VR equation is the way in whichthe user interacts with the virtual objects. Head-trackingsensors are used to tell the system where the user is lookingso the graphics can be adjusted accordingly. Other sensorscan be placed in gloves worn by the user. The system canthus tell where the user’s hand is within the virtual world,and if the user “grasps” with the glove, the user’s hand inthe virtual world will grasp or otherwise interact with thevirtual object. More elaborate systems involve a full-bodysuit studded with sensors.To make interaction realistic, VR researchers have hadto study both the operation of human senses and that of theskeleton and muscles. For a truly realistic experience, theuser must be able to feel the resistance of objects (whichcan be implemented by a force-feedback system). Soundcan be handled easily, but as of yet not much has been donewith the senses of smell and taste.In designing a VR system, there are a number of importantconsiderations. Will the user be physically immersed(such as with an HMD), or, as in some military applications,will the user be seeing both a virtual and the actualphysical world? How important is graphic realism vs. realtimeresponsiveness? (Opting too much for computationallyintensive realism might cause unacceptable latency, or delaybetween a user action and the environment’s response.)ApplicationsBesides military training, currently the most viable applicationfor VR seems to be entertainment. VR techniqueshave been used to create immersive experiences in elaboratefacilities at venues such as Disneyland and UniversalStudios, and to some extent even in local arcades. VR that isaccompanied by convincing physical sensations has allowedfor the creation of a new generation of roller coasters that ifbuilt physically would be too expensive, too dangerous, oreven physically impossible.However, there are other significant emerging applicationsfor VR. When combined with telerobotic technology(see telepresence), VR techniques are already being usedto allow surgeons to perform operations in new ways. VRtechnology can also be used to make remote conferencingmore realistic and satisfactory for participants. Clearly thepotential uses for VR for education and training in manydifferent fields are endless. VR technology combined withrobotics could also be used to give disabled persons muchgreater ability to carry out the tasks of daily life.In the ultimate VR system, users will be networked andable to simultaneously experience the environment, interactingboth with it and one another. The technical resourcesand programming challenges are also much greater for suchapplications. The result, however, might well be the sortof environment depicted by science fiction writers such asWilliam Gibson (see cyberspace and cyber culture).Further ReadingKim, Gehard Jounghyun. Designing Virtual Reality Systems: TheStructured Approach. New York: Springer, 2005.McMenemy, Karen, and Stuart Ferguson. A Hitchhiker’s Guide toVirtual Reality. Wellesley, Mass.: A. K. Peters, 2007.Sherman, William R., and Alan B. Craig. Understanding VirtualReality: Interface, Application, and Design. San Francisco: MorganKaufman, 2003.Sturrock, Carrie. “Virtual Becomes Reality at Stanford.” SanFrancisco Chronicle, April 29, 2007, p. A1. Available online.URL: http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/04/29/MNGFPPGVPF1.DTL. Accessed August 23, 2007.Virtual Reality Resources. Available online. URL: http://vresources.org/. Accessed August 23, 2007.VoIP (voiceover Internet protocol)The basic idea of VoIP is simple: the Internet can carrypackets of any sort of data (see tcp/ip), which means it cancarry the digitized human voice as well, carrying ordinaryphone calls. There are several ways to do this:• a regular phone plus an adapter that connects to thecomputer and compresses and converts between regularanalog phone signals and the digital equivalent• a complete “IP phone” unit that includes all neededhardware and software—no computer needed, just anetwork connection, such as to a router• use of the computer’s own sound card and speakerswith a microphone, plus software (often free)Using that last option, VoIP service can be essentiallyfree, regardless of distance. However, one can only callsomeone who is currently connected to the Internet andalso has VoIP software.Alternatively, one can subscribe to a VoIP provider suchas Skype who also provides connectivity to the “plain oldtelephone service” (POTS). This allows calling anyone whohas an ordinary phone: The VoIP provider sends the call

von Neumann, John 497A regular telephone carries the voice as an analog signal over the phone line. For Internet (IP) telephony, however, the user’s voice from themicrophone is converted to a digital signal that is carried by standard Internet packets. At the destination, the packets are reassembled into astream of digital data that is then sent to the sound card to be turned back into voice sounds to be played through the system speaker.over the Internet to the nearest connection point, whereit is placed as a regular phone call. The charges are muchlower than typical long-distance plans. (For example, as of2007 Skype charged a flat rate of $3.00 a month for unlimitedcalls to the United States and Canada and only a fewcents per minute to most developed countries.)Since video can also be sent over the Internet, videoover IP for calling and conferencing is also becoming morecommon. Video does require a higher bandwidth connectionthan does voice.Advantages and DrawbacksVoIP has several advantages over regular phone service.Because it uses the Internet’s flexible packet-switching system,it uses bandwidth more efficiently (indeed, much conventionalphone service is now carried as digital packetsas well). If done through a direct computer-to-computerconnection with free software, VoIP can be essentially freeto the user, since the Internet connection is presumablyalready paid for. (It also follows that VoIP is most advantageousfor long-distance calling.) Finally, VoIP can be usedwith wireless mobile devices, sometimes with lower costthan cell service.At least as currently implemented, VoIP does have somedisadvantages:• Like cordless phones (but unlike traditional phones),VoIP requires that the user be connected to power. Thismay make the system unavailable in an emergency.• Also, in an emergency, a 911 operator has no way toknow where the caller is located geographically. Thiscould be a problem if the caller is unable to providethis information.• While a regular phone is a pretty simple device, VoIPrequires special hardware or a PC, which might fail.• VoIP requires a working Internet connection—inpractice, a high-speed connection (see broadband).Load or instability in the network could cause interruptionsin calls or a lowering of voice quality.• As with other data sent over the Internet, there arepotential security concerns. Encryption can be usedto secure VoIP calls, but this in turn leads to concernsby law enforcement agencies seeking to implementeavesdropping warrants.Despite these disadvantages, VoIP is likely to continueto become more prevalent and reliable due to the advantagesof integrating with the global Internet and a widevariety of devices.Further Reading“History of VoIP.” Available online. URL: http://www.utdallas.edu/~bjackson/history.html. Accessed December 3, 2007.Kelly, Timothy V. VoIP for Dummies. Hoboken, N.J.: Wiley, 2005.Skype. Available online. URL: http://www.skype.com/. AccessedDecember 3, 2007.Valdes, Robert. “How VoIP works.” Available online. URL: http://communication.howstuffworks.com/ip-telephony.htm.Accessed December 3, 2007.Van Meggelen, Jim, Jared Smith, and Leif Madsen. Asterisk: TheFuture of Telephony. Sebastapol, Calif.: O’Reilly, 2005.Venezia, Paul. “Open Source VoIP Makes the Business Connection.”Infoworld, March 19, 2007. Available online. URL:http://www.infoworld.com/article/07/03/19/12FEopenvoip_1.html. Accessed December 3, 2007.Wallingford, Ted. Switching to VoIP. Sebastapol, Calif.: O’Reilly,2005.von Neumann, John(1903–1957)Hungarian–AmericanMathematician, Computer ScientistJohn von Neumann made wide-ranging contributions infields as diverse as pure logic, simulation, game theory, andquantum physics. He also developed many of the key conceptsfor the architecture of the modern digital computerand helped design some of the first successful machines.Von Neumann was born on December 28, 1903, in Budapest,Hungary, to a family with banking interests. As a youthhe showed a prodigious talent for calculation and interest inmathematics, but his father opposed his pursuing a career inpure mathematics. Therefore, when von Neumann enteredthe University of Berlin in 1921 and the Technische Hochschulein 1923, he earned his Ph.D. in chemical engineering.However, in 1926 he went back to Budapest and earned aPh.D. in mathematics with a dissertation on set theory. He

498 von Neumann, JohnJohn von Neumann developed automata theory as well as fundamentalconcepts of computer architecture such as storing programsin memory along with the data. He also did seminal work in logic,quantum physics, simulation, and game theory. (SPL / PhotoResearchers, Inc.)would then serve as privatdozcent, or lecturer, at Berlin andthe University of Hamburg.During the mid-1920s, two competing mathematicaldescriptions of the behavior of atomic particles were beingoffered by Erwin Schrödinger’s wave equations and WernerHeisneberg’s matrix approach. Von Neumann showed thatthe two theories were mathematically equivalent. His 1932book, The Mathematical Foundations of Quantum Mechanics,remains a standard textbook to this day. Von Neumann alsodeveloped a new form of algebra where “rings of operators”could be used to describe the kind of dimensional spaceencountered in quantum mechanics.Meanwhile, von Neumann had become interested in themathematics of games, and developed the discipline thatwould later be called game theory. His “minimax theorem”described a class of two-person games in which both playerscould minimize their maximum risk by following aspecific strategy.Computation and Computer ArchitectureIn 1930, von Neumann immigrated to the United States,where he would become a naturalized citizen and spend therest of his career. He was made a Fellow at the new Institutefor Advanced Study at Princeton at its founding in 1933,and would serve in various capacities there and as a consultantfor the U.S. government.In the late 1930s, interest had begun to turn to the constructionof programmable calculators or computers (seeChurch, Alonzo and Turing, Alan). Just before and duringWorld War II, von Neumann worked on a variety ofproblems in ballistics, aerodynamics, and later, the designof nuclear weapons. All of these problems cried out formachine assistance, and von Neumann became acquaintedboth with British research in calculators and the massiveHarvard Mark I programmable calculator (see Aiken,Howard).A little later, von Neumann learned that two engineerswere working on a new kind of machine: an electronic digitalcomputer called ENIAC that used vacuum tubes for itsswitching and memory, making it about a thousand timesfaster than the Mark I. Although the first version of ENIAChad already been built by the time von Neumann came onboard, he served as a consultant to the project at the Universityof Pennsylvania’s Moore School.The earliest computers (such as the Mark I) read instructionsfrom cards or tape, discarding each instruction as itwas performed. This meant, for example, that to program aloop, an actual loop of tape would have to be mounted andcontrolled so that instructions could be repeated. The electronicENIAC was too fast for tape readers to keep up, so ithad to be programmed by setting thousands of switches tostore instructions and constant values. This tedious proceduremeant that it wasn’t practicable to use the machine foranything other than massive problems that would run formany days.In his 1945 “First Draft of a Report on the EDVAC” andhis more comprehensive 1946 “Preliminary Discussion ofthe Logical Design of an Electronic Computing Instrument,”von Neumann established the basic architecture and designprinciples of the modern electronic digital computer.Von Neumann declared that in future computers themachine’s internal memory would be used to store constantdata and all instructions. With programs in memory, loopingor other decision making can be accomplished simplyby “jumping” from one memory location to another. Computerswould have two forms of memory: relatively fastmemory for holding instructions, and a slower form of storagethat could hold large amounts of data and the results ofprocessing. (In today’s PCs these functions are provided bythe random access memory [RAM] and hard drive respectively.)The storage of programs in memory also meant thata program could treat its own instructions like data andchange them in response to changing conditions.In general, von Neumann took the hybrid design ofENIAC and conceived of a design that would be all-electronicin its internal operations and store data in the mostnatural form possible for an electronic machine—binary,with 1 and 0 representing the on and off switching statesand, in memory, two possible “marks” indicated by magnetism,voltage levels, or some other phenomenon. The logicaldesign would be consistent and largely independent of thevagaries of hardware.

von Neumann, John 499Eckert and Mauchly (see Eckert, J. Presper andMauchly, John William) and some of their supporterswould later claim that they had already conceived of theidea of storing programs in memory, and in fact they hadalready designed a form of internal memory called a mercurydelay line. Whatever the truth in this assertion, itremains that von Neumann provided the comprehensivetheoretical architecture for the modern computer, whichwould become known as the von Neumann architecture.Von Neumann’s reports would be distributed widely andwould guide the beginnings of computer science researchin many parts of the world.Looking beyond EDVAC, von Neumann, together withHerman Goldstine and Arthur Burks, designed a newcomputer for the Institute for Advanced Study that wouldembody the von Neumann principles. The IAS machine’sdesign would in turn lead to the development of researchcomputers for RAND Corporation, the Los Alamos NationalLaboratory, and in several countries including Australia,Israel, and even the Soviet Union. The design would eventuallybe commercialized by IBM in the form of the IBM 701.In his later years, von Neumann continued to explorethe theory of computing. He studied ways to make computersthat could automatically maintain reliability despite theloss of certain components, and he conceived of an abstractself-reproducing automaton (see cellular automata).Von Neumann’s career was crowned with many awardsreflecting his diverse contributions to American sciencetechnology. These include the Distinguished Civilian ServiceAward (1947), Presidential Medal of Freedom (1956),and the Enrico Fermi Award (1956). Von Neumann died onFebruary 8, 1957, in Washington, D.C.Further ReadingAspray, William. John von Neumann and the Origins of ModernComputing. Cambridge, Mass.: MIT Press, 1990.Heims, S. J. John von Neumann and Norbert Wiener: From Mathematicsto the Technologies of Life and Death. Cambridge, Mass.:MIT Press, 1980.“John Louis von Neumann” [biography]. Available online. URL: http://ei.cs.vt.edu/~history/VonNeumann.html. Accessed August 23,2007.MacRae, Norman. John Von Neumann: The Scientific Genius WhoPioneered the Modern Computer, Game Theory, Nuclear Deterrence,and Much More. 2nd ed. Providence, R.I.: AmericanMathematical Society, 2000.von Neumann, John. The Computer and the Brain. New Haven,Conn.: Yale University Press, 1958.———. Theory of Self-Reproducing Automata. Edited and compiledby Arthur W. Burks. Urbana: University of Illinois Press, 1966.

WWales, Jimmy(1966– )AmericanInternet EntrepreneurJimmy Wales is a key force behind Wikipedia, the community-editedonline encyclopedia that has become a popularstop for Web users seeking information about any of millionsof topics.Wales was born on August 7, 1966, in Huntsville, Alabama,and received his early education in a tiny privateschool run by his mother and grandmother. However, Walesthen went to an advanced college preparatory school inHuntsville, where he was extensively exposed to computertechnology. Wales went on to earn a bachelor’s degree infinance from Auburn University and a master’s in finance atthe University of Alabama. He entered but did not completethe doctoral program, later attributing his dropping out toboredom. During the 1990s Wales became research directorat Chicago Options Associates, trading so successfully incurrency and interest rate options that he achieved lifetimefinancial security.By that time Wales had become involved with the growinge-commerce boom. However, his first project, an “eroticsearch engine” called Bomis, would be controversial. Usingthe Bomis site, Wales and Larry Sanger then launchedtheir first online encyclopedia, Nupedia. In 2001, however,Sanger suggested the use of wiki software (see wikisand Wikipedia). Wales and Sanger set up the parametersfor how users would contribute, collaborate, and reviewarticles. Wikipedia soon far outstripped Nupedia. Sangerand Wales found themselves in frequent disagreement, andSanger left Wikipedia in 2002.Wikipedia and BeyondIn 2003 Wales established the Wikimedia Foundation, anonprofit organization to support Wikipedia and a varietyof new projects based on online communities. In 2004Wales and Angela Beesley founded a for-profit company,Wikia, Inc. Besides making it easy for individuals andcommunities to organize and manage their own wikis andblogs, Wikia also intends to apply the wiki collaborativeprinciple to creating a search engine that would draw uponusers’ own expertise and interests and operate “transparently.”Wales believes this model will prove to be superiorto proprietary operations such as Google.Wales was criticized in 2005 for editing his own biographyin Wikipedia, downplaying the pornographic natureof Bomis and minimizing Sanger’s role as a cofounder ofWikipedia. Wales later expressed regrets about his editing,while continuing to insist that Sanger’s role was that ofan employee rather than a cofounder. (Sanger later createdCitizendium, an online encyclopedia that requires strictercredentials for editors.)Politically, Wales describes himself as a passionateobjectivist (follower of Ayn Rand’s philosophy) and a libertarianwho admires philosopher-economist F. A. Hayek(though distancing himself from the Libertarian Party).Wales’s interest in decentralized, emergent organizations(such as Wikipedia and Wikia) can be seen as flowing outof his political philosophy. At the same time, the scope and500

Web 2.0 and beyond 501powers Wales continues to exercise over Wikipedia can beunclear and subject to controversy.In 2005 Wales became a member of the board of directorsof Socialtext, a developer of wiki technology. In 2006he also joined the board of Creative Commons, developerof new ways to share intellectual property. That same yearTime listed Wales among 100 of the year’s most influentialpeople, and Wales received a Pioneer Award from the ElectronicFrontier Foundation. Wales lives near St. Petersburg,Florida.Further Reading“Jimmy Wales: Free Knowledge for Free Minds” [blog]. http://blog.jimmywales.com/. Accessed May 10, 2007.Lee, Ellen. “As Wikipedia Moves to S.F., Founder DiscussesPlanned Changes.” San Francisco Chronicle, November 30,2007. Available online. URL: http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/11/30/BUOMTKNJA.DTL. AccessedDecember 3, 2007.Mangu-Ward, Katherine. “Wikipedia and Beyond: Jimmy Wales’Sprawling Vision.” Reason, June 2007, pp. 18–29.Tapscott, Don, and Anthony D. Williams. Wikinomics: How MassCollaboration Changes Everything. New York: Penguin, 2006.Wikipedia. Available online. URL: http://en.wikipedia.org/wiki/Main_Page. Accessed May 10, 2007.wearable computersFor some time, technology pundits have talked about computersbeing literally woven into daily life, embedded inclothing and personal accessories. However, implementationshave thus far seen only limited use. For example,watches with limited computer functions (see pda) havenot proven popular—a watch large enough for input anddisplay of information would likely be too bulky for comfort.(People have also walked about with attached webcams,although the novelty seems to have quickly wornoff.)Emerging PossibilitiesThere are, however, a number of more limited wearablecomputers that are likely to be practical. Small cards (seerfid and smart card) could provide tracking for childrenor others needing monitoring. Embedded sensors could bedesigned to detect whether an elderly person has fallen orperhaps has suffered a heart attack.Head-mounted displays that fit into eyeglasses or gogglesare already in use and can offer applications rangingfrom gaming (see virtual reality) to providing informationaloverlays to aid in military reconnaissance, policepatrol, or firefighting. (This could also be combined withtracking and communications.) Other embedded computersmight provide hands-free voice recognition or languagetranslation.More whimsical wearable computers could control thecolors and patterns displayed by garments, perhaps varyingthem with the mood of the wearer.Whimsy aside, some serious effort is now going intodeveloping a wide range of wearable computer applications.The most prominent effort is wearIT@work, funded by theA fashion model wears a “Skooltool” outfit that allows informationto be played through earphones or projected onto the lenses. Theoutfit was a collaboration between MIT researchers and fashiondesigners. (Sam Ogden / Photo Researchers, Inc.)European Union. It is developing an Open Wearable ComputingFramework and standard hardware.Further ReadingCristol, Hope. “The Future of Wearable Computers.” The Futurist36 (September 1, 2002): 68.MIT Media Lab Wearable Computing. Available online. URL:http://www.media.mit.edu/wearables/index.html. AccessedDecember 3, 2007.“Wearing Technology on Your Sleeve.” PhysOrg, November 26,2007. Available online. URL: http://www.physorg.com/news115310793.html. Accessed December 3, 2007.WearIt@Work. Available online. URL: http://www.wearitatwork.com/. Accessed December 3, 2007.Xu, Yangsheng, Wen Jung Li, and Ka Keung Lee. Intelligent WearableInterfaces. Hoboken, N.J.: Wiley Interscience, 2007.Web 2.0 and beyondSomewhere between a buzzword and a genuine new paradigm,Web 2.0 refers to a number of developments that are

502 Web 2.0 and beyond“Web 2.0” is a somewhat nebulous term, but its core technologies are changing both how information is presented on the Web and how userscan create and share their own content.changing the way content is created and presented on theWeb, as well as ways in which Web users are using technologyto create new communities and institutions. (The termis somewhat misleading because it seems to imply a newversion of the fundamental Web software itself. It is more achange in the way the Web is perceived and used.)The term emerged into prominence following a 2004conference that emphasized the Web as being not justa place to offer services, but a platform upon which tobuild them, offering applications that are not dependenton any particular operating system. As services were builtand users participated in new ways, the emerging communitieswould then extend the power of the Web platformeven further (see social networking and user-createdcontent). For some often-cited examples, see Craigslist,eBay, Wikipedia, and YouTube.Web 2.0 ToolsAlthough the most important part of Web 2.0 is its businessand social models, a number of Web technologies areneeded to provide the flexibility and rich interaction neededto offer a new Web experience. These include:• dynamic, efficient generation of content (see Ajax)• programming interfaces (see api) using structuredtext files (see xml)• platforms for running applications in the browser,such as Google apps• merging and customizing content from differentsources (see mashups)• user subscription to content (see podcasting and rss)

Web browser 503• platforms for user-created content and collaboration(see blogs and blogging, social networking, andwikis and Wikipedia)In some quarters the term Web 2.0 is already obsoleteor relegated to a marketing buzzword, while the search ison for new ways to describe the latest developments suchas, inevitably, “Web 3.0.” One possible emphasis movingbeyond Web 2.0 is the leveraging of the actual knowledgecontained in Web pages, properly encoded and interpretedby applications (see semantic web and software agent).Whatever terminology might be used, the importantthing is that people are using the Web in the late 2000decade in substantially new ways, and that the consequencesare likely to spread beyond the online world tosociety as a whole.Further ReadingFost, Dan. “Digital Utopia: A New Breed of Technologists Envisionsa Democratic World Improved by the Internet.” SanFrancisco Chronicle, November 5, 2006, p. F1. Availableonline. URL: http://sfgate.com/cgi-bin/article.cgi?file=/c/a/2006/11/05/BUGIGM5A2D1.DTL. Accessed December 4,2007.———. “The People Who Populate Web 2.0” San FranciscoChronicle, November 5, 2006, p. F5. Available online. URL:http://sfgate.com/cgi-bin/article.cgi?file=/c/a/2006/11/05/BUG78M5OUA1.DTL. Accessed December 4, 2007.Madden, Mary, and Susannah Fox. “Riding the Waves of ‘Web2.0.’ ” Pew Internet & American Life Project, October 5, 2006.Available online. URL: http://www.pewinternet.org/pdfs/PIP_Web_2.0.pdf. Accessed December 4, 2007.Metz, Cade. “Web 3.0.” PC Magazine, March 14, 2007. Available online.URL: http://www.pcmag.com/article2/0,1759,2102852,00.asp.Accessed December 4, 2007.Solomon, Gwen, and Lynne Schrum. Web 2.0: New Tools, NewSchools. Eugene, Ore.: ISTE, 2007.Vossen, Gottfried, and Stephan Hagemann. Unleashing Web 2.0:From Concepts to Creativity. Burlington, Mass.: MorganKaufmann, 2007.When the Web was first created in the early 1990s (seeBerners-Lee, Tim) it consisted only of text pages, althoughthere were a few experimental graphical Web extensionsdeveloped by various researchers. The first graphical Webbrowser to achieve widespread use was Mosaic created byMarc Andreessen, developed at the National Center forSupercomputing Applications (NCSA). (See Andreessen,Marc.) By 1993, Mosaic was available for free downloadand had become the browser of choice for PC users.Andreessen left NCSA in 1994 to found Netscape Corporation.The Netscape Navigator browser improved Mosaicin several ways, making the graphics faster and more attractive.Netscape included a facility called Secure SocketsLayer (SSL) for carrying out encrypted commercial transactionson-line (see e-commerce).Microsoft, which had been a latecomer to the Internetboom, entered the fray with its Microsoft Internet Explorer.At first the program was inferior to Netscape, but it wassteadily improved. Aided by Microsoft’s controversial tactic ofbundling the free browser starting with Windows 95, InternetExplorer has taken over the leading browser position withWeb browserThe World Wide Web consists of millions of sites (seeWorld Wide Web and Web server) that provide hypertextdocuments (see html and Web page design) that caninclude not only text but still images, video, and sound. Toaccess these pages, the user runs a Web-browsing program.The basic function of a Web browser is to request apage by specifying its address (URL, uniform [or universal]resource locator). This request resolves to a request (HTTP,HyperText Transport Protocol) that is processed by the relevantWeb server. The server sends the HTML document tothe browser, which then displays it for the user. Typically,the browser stores recently requested documents and filesin a local cache on the user’s PCs. Use of the cache reducesthe amount of data that must be resent over the Internet.However, sufficiently skilled snoopers can examine thecache to find details of a user’s recent Web surfing. (Cachingis also used by Internet Service Providers so they canprovide frequently requested pages from their own serverrather than having to fetch them from the hosting sites.)A Web browser such as Microsoft Internet Explorer or Firefoxmakes it easy to find and move between linked Web pages. Browserusers can record or “bookmark” favorite pages. Browser plug-insprovide support for services such as streaming video and audio.Here, part of the photo library of the National Oceanic and AtmosphericAdministration is shown. (NOAA image)

504 webcamabout a 75 percent market share by 2001. However, a ratherstrong competitor later emerged in Firefox, and other browserssuch as Opera and Safari also have their supporters, whofeel those products are more agile, versatile, and perhaps moresecure than Internet Explorer.Some typical features of a modern Web browser include• navigation buttons to move forward and back throughrecently visited pages• tabs to switch between Web pages• a “history” panel allowing return to pages visited inrecent days• a search button that brings up the default searchengine (which can be chosen by the user)• the ability to save page as “favorites” or “bookmarks”for easy retrievalThe Browser as PlatformToday a Web user can view a live news broadcast, listen tomusic from a radio station, or view a document formatted tonear-print quality. All these activities are made possible by“helper” software (see plug-in) that gives the Web browserthe capability to load and display or play files in special formats.Examples include the Adobe PDF (Portable DocumentFormat) reader, the Windows Media Player, and RealPlayerfor playing video and audio content (see streaming).What makes the browser even more versatile is the abilityto load and run programs from Web sites (see Java).Java was highly touted starting in the mid-1990s, and someobservers believed that by making Web browsers into platformscapable of running any sort of software, there wouldbe less need for proprietary operating systems such asMicrosoft Windows. Microsoft has responded by trying toshift developers’ emphasis from Java to its proprietary technologycalled .NET. Meanwhile, the tools for making Webpages more versatile and interactive continue to proliferate,including later versions of HTML and XML (see Web pagedesign). This proliferation, as well as use of proprietaryextensions can cause problems in accessing Web sites fromolder or less-known browsers.The growing numbers of handheld or palm computers(see portable computers) are accompanied by scaleddownWeb browsers. These are generally controlled bytouch and have a limited display size, but can provideinformation useful to travelers such as driving directions,weather forecasts, and capsule news or stock summaries.Further ReadingBarker, Donald I., and Katherine T. Pinard. Microsoft InternetExplorer 7, Illustrated Essentials. Boston: Course Technology,2007.Browser Review. Available online. URL: http://www.yourhtmlsource.com/starthere/browserreview.html.Accessed August23, 2007.Firefox 2. Available online. URL: http://www.mozilla.com/en-US/firefox/. Accessed August 23, 2007.Opera Browser Home Page. Available online. URL: http://www.opera.com/. Accessed August 23, 2007.Ross, Blake. Firefox for Dummies. Hoboken, N.J.: Wiley, 2006.Windows Internet Explorer 7. Available online. URL: http://www.microsoft.com/windows/products/winfamily/ie/default.mspx. Accessed August 23, 2007.webcamThousands of real-time views of the world are available onthe Web. These include everything from the prosaic (a coffeemachine at MIT) to the international (a view of downtownParis or Tokyo) to the sublime (a Rocky Mountainsunset). All of these views are made possible thanks to theavailability of inexpensive digital cameras (see photography,digital).To create a basic webcam, the user connects a digitalcamera to a PC, usually via a USB cable. A program controlsthe camera, taking a picture at frequent intervals (perhapsevery 30 seconds or minute). The picture is received fromthe camera as a JPG (JPEG) file. The program then uploadsthe picture to the user’s Web page (usually using file transferprotocol, or ftp), replacing the previous picture. Usersconnected to the Web site can click to see the latest picture.Alternatively, a script running on the server can update thepicture automatically.History and ApplicationsOne of the earliest and most famous webcams was createdby Quentin Stafford-Fraser in 1991. He later recalled that heand his fellow “coffee club” members were tired of makingthe long trek to the coffee room at the Cambridge Universitycomputer laboratory. It seemed that more often thannot the life-giving brew so necessary to computer sciencehad already been consumed. So they rigged a video camera,connected it to a video capture card, and fed the imageinto the building’s local network. Now researchers workinganywhere in the building could get an updated image of thecoffee machine three times a minute. This wasn’t technicallya webcam. At the time the Web was just being developedby Tim Berners-Lee (see Berners-Lee, Tim). However,the camera was put on the Web in 1993, where it resideduntil 2001 when the laboratory housing the now-famouscoffee machine was moved.The webcam became a social phenomenon in 1996 whena college student named Jennifer Ringley started Jennicam,a webcam set up to make a continuing record of her dailylife available on the Web. There were soon many imitators.Apparently this use of Webcams taps into humans’ intensecuriosity about the details of each other’s lives—a curiositythat to some critics tips over into voyeurism and obsession.The popularity of such social webcams may have contributedto the “reality TV” phenomenon at the turn of the newcentury.Webcams have many practical applications, however.People on the road can log into the Web and check to makesure everything is okay at home. A webcam also makes aninexpensive monitor for checking on infants or toddlers inanother room, or checking on the behavior of a babysitter(“Nannycam”).Webcams can also serve an educational purpose. Theycan take viewers to remote volcanoes or the interior of an

webmaster 505Amazon rain forest. In a sense, viewers who saw the picturesof the Martian surface and the explorations of theSojourner rover were using the farthest-reaching webcamof all.Further ReadingBreeden, John, and Jason Byrne. Guide to Webcams. Indianapolis:Prompt Publications, 2001.Layton, Julia. “How Webcams Work.” Available online. URL:http://www.howstuffworks.com/webcam.htm. AccessedAugust 23, 2007.Mobberly, Martin. Lunar and Planetary Webcam User’s Guide. NewYork: Springer, 2006.Webcam Resources. Available online. URL: http://www.resourcehelp.com/qserwebcam.htm. Accessed August 23, 2007.Web filterListings of the most frequent requests typed into Web searchengines usually begin with the word sex. Although sensationaljournalism of the mid-1990s sometimes unfairlyportrayed the World Wide Web as nothing more than anelectronic red light district, it is indisputable that there aremany Web sites that feature material that most people wouldagree is not suitable for young people. Many parents as wellas some schools, libraries, and workplaces have installed Webfilter programs, marketed under names such as SurfWatch orNetNanny. Popular Internet security programs (such as thosefrom Norton/Symantec) also include Web filter modules.The Web filter examines requests made by a Web user(see World Wide Web and Web browser) and blocksthose associated with sites deemed by the filter user to beobjectionable. There are two basic mechanisms for determiningwhether a site is unsuitable. The first is to check thesite’s address (URL) against a list and reject a request forany site on the list. (Most filter programs come with defaultlists; the filter user can add other sites as desired. Generally,the filter is installed with a password so only the authorizeduser [such as a parent] can change the filter’s behavior.)The other filtering method relies on a list of keywordsassociated with objectionable activities (such as pornography).When the user requests a site, the filter checks the pagefor words on the keyword list. If a matching word or phraseis found, the site is blocked and not shown to the user.Each method has its drawbacks: Using a site list willmiss new sites that appear between list updates, while usingkeywords can result in appropriate sites also being blocked.For example, a keyword filter that blocks sites with theword breast will probably also block a site devoted to breastcancer research, a fact often pointed out by opponents oflaws requiring the use of Web filters. The list and keywordmethods can be combined.Filtering and parental control often involves more thansimply blocking Web sites. Many filtering products attemptto scan and block problematic chat and e-mail messages.Another type of filtering tries to stop users (particularlychildren) from providing sensitive information such astheir name and address online. Another common parentalcontrol feature is the ability to limit the times of day andtotal amount of time a child can go online.Besides protecting children from inappropriate materialat home or in a school or library, Web filters are also used inworkplaces. Besides wanting to keep workers from becomingdistracted, employers are concerned that allowing Internetpornography in the workplace may make them liable forcreating a “hostile work environment” under sexual harassmentlaws.However, civil liberties groups such as the ACLU objectto the use of Web filters in public libraries on First Amendmentgrounds and have vigorously fought such legislationin the courts. The 1996 Communications Decency Act wasdeclared unconstitutional by the U.S. Supreme Court, anda later law, the 1998 Child On-line Protection Act (whichrequires that users of adult Web sites provide proof of age)was overturned by the U.S. Supreme Court in 2004.The next attempt at protecting children online was the2002 Children’s Internet Protection Act. This law was eventuallyupheld by the courts subject to the requirement thatadult library users be given prompt unfiltered access to theInternet upon request.Critics of Web filters suggest that rather using technicaltools to block access to the Internet, parents and teachersshould talk to children about their use of the Internet andsupervise it if necessary. Another approach is to focus onWeb sites that are designed especially for kids.Further ReadingGilbert, Alorie, and Stefanie Olsen. “Do Web Filters Protect YourChild?” CNET News. Available online. URL: http://news.com.com/Do+Web+filters+protect+your+child/2100-1032_3-6030200.html. Accessed August 23, 2007.Internet Filter Reviews. Available online. URL: http://internetfilter-review.toptenreviews.com/.Accessed August 23, 2007.Olsen, Stefanie. “Kids Outsmart Web Filters.” CNET News. Availableonline. URL: http://news.com.com/Kids+outsmart+Web+filters/2009-1041_3-60 62548.html. Accessed August 23, 2007.Parental Control Software. Available online. URL: http://www.softforyou.com/. Accessed August 23, 2007.webmasterThere are many online services (including some free ones)that will provide users with personal Web pages. Thereare also programs such as Microsoft FrontPage that allowusers to design Web pages by arranging objects visually onthe screen and setting their properties. However, creatingand maintaining a complete Web site with its many linkedpages, interactive forms and interfaces to databases andother services is a complicated affair. For most moderateto large-size organizations, it requires the services of a newcategory of IT professional: the webmaster.Although the mixture of tasks and responsibilities willvary with the extent and purpose of the Web site, the skillset for a webmaster can include the following:Developing and Extending the Web site• understanding how the Web site responds to andmanages requests (see Web server)

506 Web page design• fluency in the basic formatting of text and other pagecontent and the use of frames and other tools fororganizing and presenting text (see html)• extended formatting and content organization facilitiessuch as Cascading Style Sheets (CSS), DynamicHTML (DHTML), and Extensible Markup Language(see xml)• use of graphics formats and graphics and animationprograms (such as Photoshop, Flash, and Dream-Weaver)• extending the interactivity of Web pages throughwriting scripts using tools such as JavaScript and PHP(see cgi, JavaScript, and Python)• dealing with platform and compatibility issues,including browser compatibilityIt is hard to draw a bright line between advanced tasksfor webmasters and full-blown applications designed torun on servers or Web browsers. Some additional tools forextending Web capabilities include:• languages for Web application development (see c#,Java, Ruby, and Visual Basic)• Web server and browser plug-ins• Active X controls and the Microsoft .NET framework(for Windows-based systems)• techniques for the efficient updating of dynamic Webpages (see Ajax)Administrative Tasks• Obtaining, organizing, and updating the content forWeb pages (this may be delegated to writers, editors,or graphics specialists)• monitoring the performance of the Web server• ensuring site availability and response time• recommending acquisition of new hardware or softwareas necessary• using tools to gather information about how the site isbeing used, what parts are being visited, the effectivenessof advertising, and so on (This is particularly relevantto commercial sites, and can raise privacy issues.)• setting up and managing facilities for online shopping(see e-commerce)• installing and using security tools (particularly importantfor commercial and sensitive government sites)• developing policies and deploying tools to help protectusers’ privacy and to control the use of informationthey submit online• working with major search engine providers to ensurethat the site is presented to relevant searches• fielding queries from users about the operation of thesite• relating the Web site operation to other concerns suchas marketing, technical support, or the legal department• developing policies for Web site use• integrating the Web site operations into the overallcorporate planning and budgeting processThe mixture of technical professional and administratorthat is the webmaster makes for an always interesting andchallenging career. In larger organizations there may befurther differentiation of roles, with the webmaster mainlycharged with operation and maintenance of the site, withthe development and extension of the site handled by contentproviders and programmers. However, even in suchcases the webmaster will need to have a general understandingof how the various features of the Web site interact andof the tools used to create and maintain them. People withwebmaster skills can also work as independent consultantsto set up and run Web sites for smaller businesses, schools,and nonprofit organizations.Webmaster skills are now taught in high school, communitycollege, vocational school, and as part of universityinformation technology programs. However the situationwith regard to certification remains somewhat chaotic, witha variety of proprietary and multivendor certifications competingfor attention.The long-term outlook for qualified webmasters remainsgood. Many organizations have made a fundamental commitmentto use of the Web for business functions, and webmastersare needed to manage this effort.Further ReadingAmerican Association of Webmasters. Available online. URL:http://www.aawebmasters.com/. Accessed August 23, 2007.Big Webmaster—Webmaster Resources. Available online. URL:http://www.bigwebmaster.com/. Accessed August 23, 2007.Spainhour, Sebastian. Webmaster in a Nutshell. 3rd ed. Sebastapol,Calif.: O’Reilly, 2002.Still, Julie. The Accidental Webmaster. Medford, N.J.: InformationToday, 2003.Web page designThe World Wide Web has existed for fewer than twodecades, so it is not surprising that the principles and practicesfor the design of attractive and effective Web pages arestill emerging. As seen in the preceding entry (see webmaster),creating Web pages involves many skills. In additionto the basic art of writing, many skills that had belonged toseparate professions in the print world now often must beexercised by the same individual. These include typography(the selection and use of type and type styles), composition(the arrangement of text on the page), and graphics. To thismix must be added nontraditional skills such as designinginteractive features and forms, interfacing with other facilities(such as databases), and perhaps the incorporation offeatures such as animation or streaming audio or video.However new the technology, the design process stillbegins with the traditional questions any writer must ask:

Web server 507What is the purpose of this work? Who am I writing for?What are the needs of this audience? A Web site that isdesigned to provide background information and contactfor a university department is likely to have a printlikeformat and a restrained style. Nevertheless, the designer ofsuch a site may be able to imaginatively extend it beyondthe traditional bounds—for example, by including streamingvideo interviews that introduce faculty members.A site for an online store is likely to have more graphicsand other attention-getting features than an academicor government site. However, despite the pressure to “grabeyeballs,” the designer must resist making the site so clutteredwith animations, pop-up windows, and other featuresthat it becomes hard for readers to search for and read aboutthe products they want.A site intended for an organization’s own use should notbe visually unattractive, but the emphasis is not on grabbingusers’ attention, since the users are already committedto using the system. Rather, the emphasis will be on providingspeedy access to the information people need to do theirjob, and in keeping information accurate and up to date.Once the general approach is settled on, the design mustbe implemented. The most basic tool is HTML, which hasundergone periodic revisions and expansions (see html).Even on today’s large, high-resolution monitors a screenof text is not the same as a page in a printed book ormagazine. There are many ways text can be organized (seehypertext and hypermedia). A page that is presentinga manual or other lengthy document can mimic a printedbook by having a table of contents. Clicking on a chaptertakes the reader there. Shorter presentations (such as productdescriptions) might be shown in a frame with buttonsfor the reader to select different aspects such as featuresand pricing. Frames (independently scrollable regions ona page) can turn a page into a “window” into many kindsof information without the user having to navigate frompage to page, but there can be browser compatibility issues.Tables are another important tool for page designers. Settingup a table and inserting text into it allows pages to beformatted automatically.Many sites include several different navigation systemsincluding buttons, links, and perhaps menus. This can begood if it provides different types of access to serve differentneeds, but the most common failing in Web design isprobably the tendency to clutter pages with features to thepoint that they are confusing and actually harder to use.Although the Web is a new medium, much of the traditionaltypographic wisdom still applies. Just as many peoplewho first encountered the variety of Windows or Macintoshfonts in the 1980s filled their documents with a varietyof often bizarre typefaces, beginning Web page designerssometimes choose fonts that they think are “edgy” or cool,but may be hard to read—especially when shown against apurple background!Today it is quite possible to create attractive Web pageswithout extensive knowledge of HTML. Programs suchas FrontPage and DreamWeaver mimic the operation of aword processor and take a WYSIWYG (what you see iswhat you get) approach. Users can build pages by selectingand arranging structural elements, while choosing stylesfor headers and other text as in a word processor. Theseprograms also provide “themes” that help keep the visualand textual elements of the page consistent. Of course,designing pages in this way can be criticized as leading to a“canned” product. People who want more distinctive pagesmay choose instead to learn the necessary skills or hire aprofessional Web page designer. A feature called CascadingStyle Sheets (CSS) allows designers to precisely control theappearance of Web pages while defining consistent stylesfor elements such as headings and different types of text(see cascading style sheets).Most Web pages include graphics, and this raises anadditional set of issues. Most users now have fast Internetconnections (see broadband), but others are still limited toslower dial-up speeds. One way to deal with this situation isto display relatively small, lower-resolution graphics (usually72 pixels per inch), but to allow the user to click on ornear the picture to view a higher-resolution version. Anotherconsideration in today’s wireless world is ensuring that Webpages likely to be useful to users on the go, such as a restaurantguide, display well in the small browsers found inmobile devices (see pda and smartphone). Page designersmust also make sure that the graphics they are using are createdin-house, are public domain, or are used by permission.Animated graphics (animated GIFs or more elaboratepresentations created with software) can raise performanceand compatibility issues. Generally, if a site offers, for example,Flash animations, it also offers users an alternative presentationto accommodate those with slower connections orwithout the necessary browser plug-ins.The line between Web page design and other Web servicescontinues to blur as more forms of media are carriedonline (see digital convergence). Web designers need tolearn about such media technologies (see for example podcasting,rss, and streaming) and find appropriate ways tointegrate them into their pages. Web pages may also needto provide or link to new types of forums (see blogs andblogging and wikis and Wikipedia).Further ReadingBeaird, Jason. The Principles of Beautiful Web Design. Lancaster,Calif.: Sitepoint, 2007.Lopuck, Lisa. Web Design for Dummies. 2nd ed. Hoboken, N.J.:Wiley, 2006.Robbins, Jennifer Niederst. Learning Web Design: A Beginner’sGuide to HTML, Graphics, and Beyond. Sebastapol, Calif.:O’Reilly Media, 2003.Sitepoint. Available online. URL: http://www.sitepoint.com.Accessed August 23, 2007.Web serverMost Web users are not aware of exactly how the informationthey click for is delivered, but the providers of informationon the Web must be able to understand and usethe Web server. In simple terms, a Web server is a programrunning on a networked computer (see Internet). Theserver’s job is to deliver the information and services thatare requested by Web users.

508 Web servicesWhen a user types in (or clicks on) a link in the browserwindow, the browser sends a HTTP request (see http andweb browser). To construct the request, the browser firstlooks at the address (URL) in the user request. An addresssuch as http://www.well.com/conferencing.html consists ofthree parts:• The protocol, specifying the type of request. For Webpages this is normally http. In many cases this partcan be omitted and the browser will assume that it ismeant.• The name of the server—in this case, www.well.com. The www indicates that it is a World Wide Webserver. The rest of the server name gives the organizationand the domain (.com, or commercial).• The specific page being requested. A Web page is simplya file stored on the server, and has the extensionhtm or html to indicate that it is an HTML-formattedpage. If no page is specified, the server will normallyprovide a default page such as index.html.In order to direct the browser’s request to the appropriatehost and server, the browser sends the URL to a nameserver (see domain name system). The name server providesthe appropriate numeric IP address (see tcp/ip). Thebrowser then sends an HTTP “get” request to the server’s IPaddress.Assuming the page requested is valid, the server sendsthe HTML file to the browser. The browser in turn interpretsthe formatting and display instructions in the HTMLfile and “renders” the text and graphics appropriately. It isremarkable that this whole process from user click to displayedpage usually takes only a few seconds, even if theWeb site is thousands of miles away and requests must berelayed through many intervening computers.Web Server FeaturesWeb servers would be simple if Web pages consisted onlyof static text and graphics. However, Web pages today aredynamic: They can display animations, sound, and video.They also interact with the user, responding to menusand other controls, presenting and processing forms, andretrieving data from linked databases. To do these things,the server cannot simply serve up a preformatted page, itmust dynamically generate a unique page that responds tothe user’s actions.This interactivity requires that the server be able torun programs (scripts) embedded in Web pages. The CommonGateway Interface (CGI) is the basic mechanism forthis, though many Web page developers can now work at ahigher level to create their page’s interaction through scriptsin languages such JavaScript. (See cgi and scripting languages.)The task of interfacing Web pages with databasefacilities is often accomplished using powerful data-managementlanguages (see Perl and Python).Windows-based servers use ASP (Active Server Pages), afacility that links the Web server to Windows ActiveX controlsto access databases. The interaction is usually scriptedin VB Script or JScript.Modern Web server software also contains modules formonitoring and security—an increasingly important considerationas Web sites become essential to business andthe delivery of goods and services.One of the most popular and reliable Web servers inuse today is Apache, developed in 1995 and freely distributedwith Linux and other UNIX systems (there is also aWindows version). The name is a pun on “a patchy server,”meaning that it was developed by adding a series of “softwarepatches” to existing NCSA server code. Microsoft alsoprovides its own line of Web server software that is specificto Windows.The future should see an increasingly seamless integrationbetween Web servers, browsers, and other applications.Microsoft has been promoting .NET, an initiative thatis designed to build Internet access and interoperabilityinto all applications, providing operating system extensionsand programming frameworks (see Ajax and Microsoft.NET).Beyond Microsoft’s mainly proprietary efforts, anothersource of integration is the growing use of the ExtensibleMarkup Language (see xml) and its offshoot SOAP (SimpleObject Access Protocol) (see soap). The goal is to give Webdocuments and other objects the ability to “communicate”their content and structure to other programs, and to allowprograms to freely request and provide services to oneanother regardless of vendor, platform, or location. As thistrend progresses, the Web server starts to “disappear” as aseparate entity and the provision of Web services becomes adistributed, cooperative effort (see also Web services).Further ReadingApache Software Foundation. Available online. URL: http://www.apache.org/. Accessed August 23, 2007.Aulds, Charles. Linux Apache Web Server Administration. 2nd ed.Alameda, Calif.: Sybex, 2002.Braginski, Leonid. Running Microsoft Internet Information Server.New York: McGraw-Hill, 2000.Jones, Brian W. How to Host Your Own Web Server. Morrisville,N.C.: Lulu.com, 2006.Rosenbrock, Eric, and Eric Filson. Setting Up LAMP: Getting Linux,Apache, MySQL, and PHP Working Together. Alameda, Calif.:Sybex, 2004.Silva, Steve. Web Server Administration. Boston: Course Technology,2003.Web servicesA characteristic of the modern Web and its development isthat much of the software is designed to offer services orcapabilities that can be called upon by applications. Thiscreation of powerful, versatile building blocks has greatlysped the evolution of Web applications (see Web 2.0 andbeyond).In order to be useful, a service must be able to understand“messages” (requests) and provide appropriateresponses. The medium of exchange is a structured textfile (see xml) and a standard format. Three commonly usedspecifications (defined by the World Wide Web Consortium,or W3C) are what was originally called Simple Object

Weizenbaum, Joseph 509Access Protocol (see soap), the Web Services DescriptionLanguage (WSDL), and the Universal Description Discoveryand Integration (UDDI), which can coordinate and“broker” the services. To keep requester and responder onthe same page (so to speak), the W3C also provides a set of“profiles” that specify which versions of which specificationsare being used. Additionally, a number of specializedspecifications are under development, such as for handlingconsiderations for security and transactions.There are several ways in which Web services can beaccessed:• Remote Procedure Call (RPC), which generally usesWSDL and follows a format similar to the traditionalway programs call upon library functions• An organization based on the available messagesrather than calls or operations (see service-orientedarchitecture)• Representational State Transfer (REST), which viewsapplications or services as collections of “resources”with specific addresses (URLs) and specific requestsusing HTTPA variety of other specifications and approaches can beused; this area is a very fluid one. Fortunately, programmersand even users (see mashups) can build new Webapplications without having to know the details of how theunderlying services work.Further ReadingCerami, Ethan. Web Services Essentials: Distributed Applicationswith XML-RPC, SOAP, UDDI & WSDL. Sebastapol, Calif.:O’Reilly, 2002.Papazoglu, Michael. Web Services: Principles and Technology. UpperSaddle River, N.J.: Prentice-Hall, 2007.Richardson, Leonard, and Sam Ruby. RESTful Web Services. Sebastapol,Calif.: O’Reilly, 2007.World Wide Web Consortium. Web Services Activity. Availableonline. URL: http://www.w3.org/2002/ws/. Accessed December4, 2007.Weizenbaum, Joseph(1923– )German-AmericanComputer ScientistJoseph Weizenbaum, after writing one of the most famousprograms in the history of artificial intelligence research,eventually became one of the most persistent and cogentcritics of the AI project itself.Weizenbaum was born on January 8, 1923, in Berlinto Jewish parents. Having fled Nazi Germany with hisparents, in 1941 Weizenbaum enrolled in Wayne Universityin Detroit, Michigan. However, the following year heenlisted in the United States Army Air Corps. After thewar he resumed his study of mathematics. While workingas a research assistant, Weizenbaum had the opportunityto help design and build an early digital computer, andalthough he received his master’s degree in mathematics in1950, he would spend his career in the computer field.From 1955 to 1963 Weizenbaum worked for GeneralElectric’s Computer Development Laboratory as a systemsengineer. During this time he would oversee the design andimplementation of the first integrated computerized bankingsystem, for Bank of America.In 1963 Weizenbaum returned to academia, joining thefaculty at MIT, which had one of the nation’s foremost programsin artificial intelligence research. He contributed tothe development of the time-sharing computer system atMIT and early computer networks, but the work for whichhe would be most remembered started with his interestin getting machines to “understand” human language (seenatural language processing).In 1966 Weizenbaum and a collaborator, psychiatristKenneth Colby, created a remarkable program called Eliza(named for the character in Bernard Shaw’s play who istaught “proper English” by Professor Henry Higgins). Elizawas remarkable not for its complexity or for innovative useof AI techniques, but for the way it used a few simple proceduresto convey the impression that it was a true artificialintelligence—or indeed, a real person.Eliza worked basically by identifying key words andbasic sentence structure and then “mirroring” the user’sstatements back. A sample snippet of human-Eliza dialogmight look like this (Eliza’s words are in caps).Men are all alike.IN WHAT WAY?They’re always bugging us about something or other.CAN YOU THINK OF A SPECIFIC EXAMPLE?Well, my boyfriend made me come here.YOUR BOYFRIEND MADE YOU COME HERE?He says I’m depressed much of the time.I AM SORRY TO HEAR YOU ARE DEPRESSED.It’s true. I am unhappy.DO YOU THINK COMING HERE WILL HELP YOU NOT TOBE UNHAPPY?I need some help, that much seems certain.WHAT WOULD IT MEAN TO YOU IF YOU GOT SOME HELP?Perhaps I could learn to get along with my mother.TELL ME MORE ABOUT YOUR FAMILY.Although the program seemed to have at best a superficialunderstanding of human language, Weizenbaum soonbecame dismayed at how readily people treated it as thoughit were a human being. (Indeed, Colby wanted to use a programlike Eliza to automate psychotherapy.)The result of these concerns was Weizenbaum’s bookComputer Power and Human Reason, a collection of essaysthat both explain the achievements of AI pioneers andpoints out their limitations. If, as Weizenbaum observes,“the computer programmer is creator of universes for whichhe alone is responsible . . . universes of almost unlimited

510 Wiener, Norbertcomplexity . . .,” then indeed the computer scientist musttake responsibility for his or her creations. This is the challengethat Weizenbaum believes has not been taken seriouslyenough.As the 1960s progressed, the United States plunged intothe Vietnam War, and racial tension crackled in the streetsof major cities. Weizenbaum became increasingly concernedthat technology was being used for warlike and oppressivepurposes. As an activist, Weizenbaum campaigned againstwhat he saw as the misuse of technology for military purposessuch as missiles and missile defense systems. He wasfounder of a group called Computer Professionals againstthe ABM (anti-ballistic missile).Weizenbaum does not consider himself to be a Luddite,however, and he is not without recognition of thepotential good that can come from computer technology,though he believes that this potential can only be realizedif humans change their attitudes toward nature and theirfellow humanity.During the 1970s and 1980s Weizenbaum not onlytaught at MIT, but also lectured or served as a visiting professorat a number of institutions, including the Center forAdvanced Studies in the Behavioral Sciences at StanfordUniversity (1972–73), Harvard University (1973–74), andcoming full circle, the Technical University of Berlin andthe University of Hamburg.In 1988 Weizenbaum retired from MIT. That same yearhe received the Norbert Wiener Award for Professionaland Social Responsibility from Computer Professionalsfor Social Responsibility (CPSR). In 1991 he was given theNamur Award of the International Federation for InformationProcessing. He also received European honors suchas the Humboldt Prize from the Alexander von HumboldtFoundation in Germany.Further ReadingBen-Aaron, Diana. “Weizenbaum Examines Computers [and]Society.” The Tech (Massachusetts Institute of Technology)vol. 105, April 9, 1985. Available online. URL: http://wwwtech.mit.edu/V105/N16/weisen.16n.html.Accessed December4, 2007.ELIZA [running as a Java Applet]. Available online. URL: http://www.manifestation.com/neurotoys/eliza.php3. AccessedDecember 4, 2007.Henderson, Harry. Artificial Intelligence: Mirrors for the Mind. NewYork: Chelsea House, 2007.Weizenbaum, Joseph. Computer Power and Human Reason. SanFrancisco: W. H. Freeman, 1976.“Weizenbaum: Rebel at Work” [information about and excerptsfrom a film by Peter Haas]. Available online. URL: http://www.ilmarefilm.org/W_E_1.htm. Accessed December 4,2007.Wiener, Norbert(1894–1964)AmericanMathematician, PhilosopherNorbert Wiener developed the theory of cybernetics, or theprocess of communication and control in both machinesand living things. His work has had an important impactboth on philosophy and on design principles.Wiener was born on November 26, 1894, in Columbia,Missouri. His father was a linguist at Harvard University,and spurred an interest in communication which the boycombined with an avid pursuit of mathematics and science(particularly biology). A child prodigy, Wiener startedreading at age three, entered Tufts University at age 11,and earned his B.A. in 1909 at the age of 14, after concludingthat his lack of manual dexterity made biological worktoo frustrating. He earned his M.A. in mathematics fromHarvard only three years later, and his Harvard Ph.D. inmathematical logic just a year later in 1913. He then traveledto Europe, where he met leading mathematicians suchas Bertrand Russell, G. H. Hardy, Alfred North Whitehead,and David Hilbert. When the United States entered WorldWar I, Wiener served at Aberdeen Proving Ground, wherehe designed artillery firing tables.After the war, Wiener was appointed as an instructorat MIT, where he would serve until his retirement in 1960.However, he continued to travel widely, serving as a GuggenheimFellow at Copenhagen and Göttingen in 1926, anda visiting lecturer at Cambridge (1931–32) and Tsing-HuaUniversity in Beijing (1935–36). Wiener’s scientific interestsproved to be as wide as his travels, including research intostochastic and random processes (such as the Brownianmotion of microscopic particles) where he sought more generalmathematical tools for the analysis of irregularity.During the 1930s, Wiener began to work more closelywith MIT electrical engineers who were building mechanicalcomputers (see Bush, Vannevar and analog computer). Helearned about feedback controls and servomechanisms thatenabled machines to respond to forces in the environment.During World War II, he did secret military researchwith an engineer, Julian Bigelow, on antiaircraft gun controlmechanisms, including methods for predicting thefuture position of an aircraft based upon limited and possiblyerroneous information.Wiener became particularly interested in the feedbackloop—the process by which an adjustment is made on thebasis of information (such as from radar) to a predictednew position, a new reading is taken and a new adjustmentmade, and so on. (He had first encountered these conceptsat MIT with his friend and colleague Harold Hazen.) Theuse of “negative feedback” made it possible to design systemsthat would progressively adjust themselves such as byintercepting a target. More generally, it suggested mechanismsby which a machine (perhaps a robot) could progressivelywork toward a goal.Wiener’s continuing interest in biology led him alwaysto relate what he was learning about control and feedbackmechanisms to the behavior of living organisms. He had followedthe work of Arturo Rosenbleuth, a Mexican physiologistwho was studying neurological conditions that appearedto result from excessive or inaccurate feedback. (Unlike thehelpful negative feedback, positive feedback in effect amplifieserrors and sends a system swinging out of control.)By the end of World War II, Wiener, Rosenbleuth, theneuropsychiatrist Warren McCulloch, and the logician

wikis and Wikipedia 511Walter Pitts were working together toward a mathematicaldescription of neurological processes such as the firingof neurons in the brain. This research, which startedout with the relatively simple analogy of electromechanicalrelays (as in the telephone system) would eventually resultin the development of neural network theory (see neuralnetwork and Minsky, Marvin). More generally, these scientistsand others (see von Neumann, John) had begun todevelop a new discipline for which Wiener in 1947 gave thename cybernetics. This word is from a Greek word referringto the steersman of a ship, suggesting the control of a systemin response to its environment.The field of cybernetics attempted to draw from manysources, including biology, neurology, logic, and whatwould later become robotics and computer science. Wiener’s1948 book, Cybernetics or Control and Communicationin the Animal and the Machine, was as much philosophicalas scientific, suggesting that cybernetic principles could beapplied not only to scientific research and engineering butalso to the better governance of society. (On a more practicallevel Wiener also worked with Jerome Wiesner ondesigning prosthetics to replace missing limbs.)Although Wiener did not work much directly with computers,the ideas of cybernetics would indirectly influencethe new disciplines of artificial intelligence (AI) and robotics.However, in his 1950 book, The Human Use of HumanBeings, Wiener warned against the possible misuse of computersto rigidly control or regiment people, as was theexperience in Stalin’s Soviet Union. Wiener became increasinglyinvolved in writing these and other popular works tobring his ideas to a general audience.Wiener received the National Medal of Technology fromPresident Johnson in 1964. The accompanying citationpraised his “marvelously versatile contributions, profoundlyoriginal, ranging within pure and applied mathematics, andpenetrating boldly into the engineering and biological sciences.”He died on March 18, 1964, in Stockholm, Sweden.Further ReadingConway, Flo, and Jim Siegelm. Dark Hero of the Information Age: InSearch of Norbert Wiener, The Father of Cybernetics. New York:Basic Books, 2005.Heims, Steve J. John von Neumann and Norbert Wiener: From Mathematicsto the Technologies of Life and Death. Cambridge, Mass.:MIT Press, 1980.Wiener, Norbert. Cybernetics, or Control and Communication in theAnimal and Machine. Cambridge, Mass.: MIT Press, 1950 (2nded. 1961).———. The Human Use of Human Beings: Cybernetics and Society.Boston: Houghton Mifflin, 1950. (2nd ed., Avon Books,1970).———. Invention: The Care and Feeding of Ideas. Cambridge, Mass.:MIT Press, 1993.wikis and WikipediaA wiki (from the Hawaiian word for “quick”) is a generallyWeb-based software application that allows users to collaborativelycontribute and edit articles on various topics.Developed by Howard G. “Ward” Cunningham in the mid-1990s, the best-known example today is Wikipedia.Structure and SoftwareWiki software varies in details such as use of markup languages,programming interface, and platform. However,most wikis include the following features:• Users can create new pages (articles) or edit existingones.• Pages contain links to related pages, sometimes using“wiki words” where WordsAreScrunchedTogether-WithIntialCaps.• Simple markup can be used to create such effects asboldface, headings, or lists. The wiki software usuallytranslates this to HTML for rendering.• A record is kept of each contribution or edit, oftendisplayed on a “Recent Changes” page.• many wikis use a database (such as MySQL) to storeand retrieve pages. Some wikis simply store each pageas a file, and a few (such as TiddlyWiki) store allpages together as a single document.• Wikis can be public (open to anyone) or restricted,such as to members of an organization.• The administrator of the wiki establishes guidelinesor standards (such as for citing sources for facts) andprocedures for dealing with disputes and controversialtopics.There is now a great variety of wiki software for justabout every computing platform. At one end there is MediaWiki,the software used to implement Wikipedia, and“enterprise wikis” such as BrainKeeper and Twiki, providingcomplex features for large-scale knowledge bases. Socalledpersonal Wikis such as DidiWiki and TiddlyWikican be used by individuals for note-taking, research, ormanaging personal information.Wikipedia and Its CriticsFounded in 2001 (see Wales, Jimmy), Wikipedia is theworld’s largest and best-known wiki. As of mid-2008 Wikipediahad more than 2,500,000 articles in English and7,500,000 in more than 250 other languages. At any giventime there are about 75,000 people from all backgroundsand walks of life contributing or editing articles.Wikipedia has a number of strengths. Its ubiquity anddiversity enable it to cover tens of thousands of topics(including the obscure or the simply local) that would bedeemed unsuitable or impracticable for traditional encyclopedias.Emerging topics, including recent news events, canbe covered quickly and comprehensively (though perhapsblurring the lines between reference and journalism).The principal problem raised by critics stems from issuesof “quality control.” Unlike the case with traditional encyclopedias,there are no requirements that contributors haveacademic training or otherwise demonstrate their expertisein their chosen area. Further, the ability of anyone to editan article has led to “edit wars” as people on different sides

512 wikis and WikipediaWiki software such as the extensive and ever-growing Wikipedia, allows users to collaborate to create and update knowledge bases. Entriescan include images such as the astronomical photo shown here. There is also a place for ongoing discussion of changes to the page.of a controversial topic (or even politicians) would changearticles back and forth to reflect their views.Defenders of Wikipedia believe that the same “bottomup” writing and editing process cited by critics can alsobe one of the project’s strengths. Each article has a recordof changes, and many articles have attached discussionpages where writers can critique the page or discuss theirrationales for edits. Finally, they cite a study by the journalNature that found that in the science articles analyzed,Wikipedia averaged four errors while the Encyclopaedia Britannicawas only slightly more accurate, averaging three.Defenders of Britannica, however, point out that theirpublication has the kind of consistency that can only comethrough rigorous application of editorial standards. Wikipediadoes have standards that writers and editors areurged to apply, such as providing a citation for every significantstatement, maintaining a “neutral point of view,” andrefraining from including original research. Nevertheless,the quality of organization and writing does vary considerablyfrom one article to the next.Meanwhile innovators in Wikipedia and its communityare developing new tools that may improve the reliability of

wireless computing 513the encyclopedia. One tool, WikiScanner, searches for andcompiles information (such as affiliations) about wiki contributors,allowing readers to better judge their competenceand motivations. Wikipedia’s parent Wikimedia Foundationis also introducing a system by which previouslyunknown contributors will undergo a sort of probationaryperiod while their material is scrutinized. (Eventually theywould become “trusted” and their material would appearinstantly, as it does now for most articles.)Wikis have, like blogs, become a pervasive form ofonline communication and information sharing, and havegained considerable attention as an application for the“new” Web (see user-created content, Web 2.0 andbeyond, and social networking). Wikis are currentlybeing used to create rapidly expanding knowledge bases(such as for technical support), to share emerging scholarship,and to promulgate documentation within an organization.Hosting services (called “wiki farms”) such as Wikiaoffer communities wiki software and Web space, sometimesfree of charge. Wiki principles are also finding their wayinto software such as personal information managers (seecontent management).Further ReadingComparison of Wiki Software. Available online. URL: http://en.wikipedia.org/wiki/Comparison_of_wiki_software.Accessed May 11, 2007.Ebersbach, Anja, Markus Glaser, and Richard Heigl. Wiki: WebCollaboration. New York: Springer, 2005.Giles, Jim. “Wikipedia 2.0: Now with Added Trust.” NewScientist.com News Service. Available online. URL: http://technology.newscientist.com/channel/tech/mg19526226.200-wikipedia-20%20-now-with -added-trust.html. Accessed December 4,2007.Klobas, Jane. Wikis: Tools for Information Work and Collaboration.Oxford: Chandos Publishing, 2006.Lee, Ellen. “As Wikipedia Moves to S.F., Founder DiscussesPlanned Changes.” San Francisco Chronicle, November 30,2007. Available online. URL: http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/11/30/BUOMTKNJA.DTL. AccessedDecember 3, 2007.Leuf, Bo, and Ward Cunningham. The Wiki Way: Quick Collaborationon the Web. Reading, Mass.: Addison-Wesley, 2001.MediaWiki. Available online. URL: http://www.mediawiki.org.Accessed December 4, 2007.Wikipedia. Available online. URL: http://www.wikipedia.org.Accessed December 4, 2007.Woods, Dan. Wikis for Dummies. Hoboken, N.J.: Wiley, 2007.wireless computingUsing suitable radio frequencies to carry data among computerson a local network has several advantages. The troubleand expense of running cables (such as for Ethernet) inolder buildings and homes can be avoided. With a wirelessLAN (WLAN) a user could work with a laptop on the deckor patio while still having access to a high-speed Internetconnection.Typically, a wireless LAN uses a frequency band witheach unit on a slightly different frequency, thus allowingall units to communicate without interference. (Althoughradio frequency is now most popular, wireless LANs canalso use microwave links, which are sometimes used as analternative to Ethernet cable in large facilities.)Usually there is a network access point, a PC that containsa transceiver and serves as the network hub (it mayalso serve as a bridge between the wireless network and awired LAN). The hub computer can also be connected toa high-speed Internet service via DSL or cable. It has anantenna allowing it to communicate with wireless PCs upto several hundred feet away, depending on building configuration.Each computer on the wireless network has an adapterwith a transceiver so it can communicate with the accesspoint. The adapter can be built-in (as is the case with somehandheld computers), or mounted on a PC card (for laptops)or an ISA card (for desktop PCs) or connected to aUSB port.Simple home wireless LANs can be set up as a “peer network”where any two units can communicate directly witheach other without going through an access point or hub.Applications needing Internet access (such as e-mail andWeb browsers) can connect to the PC that has the Internetcable or DSL connection.A wireless LAN can make it easier for workers who haveto move around within the building to do their jobs. Examplesmight include physicians or nurses entering patientdata in a hospital or store workers checking shelf inventory.ProtocolsSeveral protocols or standards have been developed forwireless LANs. The most common today is IEEE 802.11b,also called WiFi with speeds up to 11 mbps (megabitsper second) transmitting on 2.4 GHz (gigahertz) band.Although that would seem to be fast enough for mostapplications, a new alternative, 802.11n, can offer speedsup to 54 mbps. Because it uses the unlicensed 5 GHzfrequency range it is not susceptible to interference fromother devices.The question of security for 802.11 wireless networkshas been somewhat controversial. Obviously, wirelessdata can be intercepted in the same way that cell phone orother radio transmissions can. The networks come with asecurity feature, WEP or the newer WPA, but many usersneglect to enable it, and it is vulnerable to certain types ofattack. Users can obtain greater security by reducing emissionsoutside the building, changing default passwordsand device IDs, and disabling DHCP to make it harderfor snoopers to obtain a valid IP address for the network.Users can also add another layer of encryption and possiblyisolate the wireless network from the wired networkby using a more secure Virtual Private Network (VPN).Many of these measures do involve a tradeoff between thecost of software and administration on the one hand andgreater security on the other. However, the growing popularityof wireless access should spur the development ofimproved built-in security.Another wireless protocol called Bluetooth has beenembedded in a variety of handheld computers, appliances,and other devices. It provides a wireless connection atspeeds up to 1 MB/second (see Bluetooth).

514 Wirth, NiklausMobile Wireless NetworkingWireless connections can also keep computer users intouch with the Internet and their home office while theytravel. Increasingly, more devices are becoming wirelesscapable while at the same time the functions of handheldcomputers, cell phones, and other devices are being merged(see also portable computers). A new initiative called 3G(third generation) involves the establishment of ubiquitouswireless services that can connect users to the Internet (andthus to one another) from a growing number of locations.Currently, the 3G agenda is further advanced in Europethan in the United States. One problem is that a standardprotocol has not yet emerged. The leading candidatesappear to be GSM (Global System for Mobile Communications),which is used by European cell phone networks, andCDMA (Code Division Multiplexing Access).3G has different speeds ranging from 144 bps for vehicularconnections to 384 kbps for personal handheld devicesto 2 bps for indoor installations. All providers, rangingfrom cell phones to packet (IP) telephony would using astandard billing format and database so that users couldoperate across many sorts of services seamlessly. Anotheralternative is WIMAX, which can be thought of as a widerareaversion of Wifi in which each base station can transmitover up to 50 kilometers. As of 2008 deployment hasbeen slower than anticipated, with widespread coverage inU.S. cities not likely to be available for at least several years.Ultimately, these technologies may bring a Star Trek–like world, with handheld devices that include not onlye-mail and Web browsing capability but a “smart phone,”MP3 music player, and even a digital camera.Further ReadingBriere, Dany, Pat Hurley, and Edward Ferris. Wireless Home Networkingfor Dummies. 2nd ed. Hoboken, N.J.: Wiley, 2006.Geier, Eric. Wi-Fi Hotspots: Setting Up Public Wireless InternetAccess. Indianapolis: Cisco Press, 2006.Haley, E. Phil. Over-the-Road Wireless for Dummies. Hoboken, N.J.:Wiley, 2006.Kwok, Yu-Kwong Ricky, and Vincent K. N. Lau. Wireless Internetand Mobile Computing: Interoperability and Performance. NewYork: Wiley, 2007.Wireless Networks and Mobile Computing. Available online.URL: http://www.networkworld.com/topics/wireless.html.Accessed August 23, 2007.Wirth, Niklaus(1934– )SwissComputer ScientistNiklaus Wirth created new programming languages suchas Pascal that helped change the way computer scientistsand programmers thought about their work. His workinfluenced later languages and ways of organizing programresources.Wirth was born on February 15, 1934, in Winterhur,Switzerland. He received a degree in electrical engineeringat the Swiss Federal Institute of Technology (ETH) in 1959,then earned his M.S. at Canada’s Laval University. He wentto the University of California, Berkeley, where he receivedhis Ph.D. in 1963 and taught in the newly founded ComputerScience Department at nearby Stanford University. Bythen he had become involved with computer science andthe design of programming languages.Wirth returned to the ETH in Zurich in 1968, wherehe was appointed a full professor of computer science. Hehad been part of an effort to improve Algol. Although Algoloffered better program structures than earlier languagessuch as FORTRAN, the committee revising the languagehad become bogged down in adding many new features tothe language that would become Algol-68 (see Algol).Wirth believed that adding several ways to do the samething did not improve a language but simply made it harderto understand and less reliable. Between 1968 and 1970,Wirth therefore crafted a new language, Pascal, named afterthe 17th-century mathematician who had built an early calculatingmachine.Pascal required that data be properly defined (see datatypes) and allowed users to define new types of data suchas records (similar to those used in databases). It providedall the necessary control structures (see loop and branchingstatements). Following the new thinking about structuredprogramming (see Dijkstra, Edsger) Pascal retainedthe “unsafe” GOTO statement but discouraged its use.Pascal became the most popular language for teachingprogramming. By the 1980s, versions such as UCSDPascal and later, Borland’s Turbo Pascal were bringingthe benefits of structured programming to desktop computerusers. Meanwhile, Wirth was working on a newlanguage, Modula-2. As the name suggested, the languagefeatured the use of modules, packages of program codethat could be linked to programs to extend their datatypes and functions. Wirth also designed a computerworkstation called Lilith. This powerful machine not onlyran Modula-2; its operating system, device drivers and allother facilities were also implemented in Modula-2 andcould be seamlessly integrated, essentially removing thedistinction between operating system and application programs.Wirth also helped design Modula-3, an object-orientedextension of Modula-2, as well as another language,Oberon, which was originally intended to run in built-incomputers (see embedded systems).Looking back at the development of object-orientedprogramming (OOP), the next paradigm that captured theattention of computer scientists and developers after structuredprogramming, Wirth has noted that OOP isn’t all thatnew. Its ideas (such as encapsulation of data) are largelyimplicit in structured procedural programming, even if itshifted the emphasis to binding functions into objects andallowing new objects to extend (inherit from) earlier ones.But he believes the fundamentals of good programminghaven’t really changed in 30 years. In a 1997 interviewWirth noted that “the woes of Software Engineering are notdue to lack of tools, or proper management, but largely dueto lack of sufficient technical competence. A good designermust rely on experience, on precise, logical thinking; andon pedantic exactness. No magic will do.”

women and minorities in computing 515Wirth has received numerous honors, including theACM Turing Award (1984) and the IEEE Computer PioneerAward (1987).Further ReadingPescio, Carlo. “A Few Words with Niklaus Wirth.” SoftwareDevelopment, vol. 5, no. 6, June 1997. Available online. URL:http://www.eptacom.net/pubblicazioni/pub_eng/wirth.html.Accessed August 23, 2007.Wirth, Niklaus. Algorithms + Data Structures = Programs. EnglewoodCliffs, N.J.: Prentice Hall, 1976.———, and Kathy Jensen. PASCAL User Manual and Report. 4thed. New York: Springer-Verlag, 1991.———. Project Oberon: The Design of an Operating System and Compiler.Reading, Mass.: Addison-Wesley, 1992.———. “Recollections about the Development of Pascal.” InBergin, Thomas J., and Richard G. Gibson, eds., History ofProgramming Languages-II, 97–111. New York: ACM Press;Reading, Mass.: Addison-Wesley, 1996.———. Systematic Programming: An Introduction. Reading, Mass.:Addison-Wesley, 1973.women and minorities in computingAlthough the development of computer science and technologyhas been an international effort, there is no doubt thatthe majority of contributors (particularly in the early years)were men—specifically white men. The interesting exceptionsinclude Charles Babbage’s collaborator Ada Lovelace,ENIAC’s first trained programmers—all women—and ofcourse Grace Hopper, whose COBOL revolutionized businesscomputing. Finally, the 2007 winner of one of thefield’s most prestigious honors, the ACM Turing Award, is awoman, compiler developer Frances E. Allen.Today women have gained prominent roles in all aspectsof computer science as well as some high-profile posts inbusiness (such as Carly Fiorina, former CEO of Hewlett-Packard, and Meg Whitman of eBay). However, the overallinvolvement of women in the higher echelons of computingremains relatively small.Educational surveys suggest that boys and girls start outwith roughly equal interest and involvement with computers,including basic courses in computer literacy and applications.However, a 2006 report from the College Boardfound that 59 percent of boys reported taking courses inprogramming, compared with 41 percent of girls. Further,the great majority of students taking advanced placementcomputer science exams are male.At the college level, women made gains in the percentageof bachelor’s degrees in the computer field, reaching 37percent by the mid-1980s. However, by 2005 that percentagehad declined to 22 percent. (However, women wereearning 34 percent of master’s degrees by 2001.) Further,the number of women working in information technologydeclined from 984,000 (28.9 percent) in 2000 to 908,000(26.2 percent) in 2006.The reasons for this decline are unclear, though somepossible causes that have been suggested include the effectsof the “dot-bust” and the perception that IT jobs were nolonger secure, the “geek” stereotype not appealing to youngwomen, and the availability of more attractive career paths.Jean Bartik (standing) and Betty Holberton answered a callfor “computers” during World War II. At the time, that was thename for a clerical person who performed calculations. But thesetwo computer pioneers, shown here at a reunion, would go on todevelop important programming techniques for the ENIAC andlater machines. (Courtesy of the Association for Womenin Computing)In terms of race or ethnicity, whites and Asians earn adisproportionate number of degrees in computing, althoughinterestingly, minority women tend to earn a higher percentagethan white women. Although minorities have beengradually increasing their participation in the computingfield, economic disadvantage (see digital divide) and pooreducational preparation continue to be obstacles for some.Efforts at ChangeA variety of programs have sought to interest women andminority students in computer programming and otherdigital careers. These can include the creation of nontraditionalprogramming environments such as Alice, whichallows students to create animated stories using scriptingand 3D graphics tools. (The theory behind this is that girlsare more interested in storytelling and character interaction,while traditional programming classes focused moreon “shoot ’em up” games and other things of more interestto boys.) There has also been a move away from emphasison “hard core” programming skills to a more broad-basedability to think about technology and its possible uses. (Asa result of this and a certain amount of affirmative action,Carnegie Mellon raised its percentage of women computerscience students from 8 percent to 40 percent.)African Americans and other minorities have also developeda number of organizations and programs designed

516 word processingto promote networking among minority professionals, linkapplicants to job openings, and encourage professionaldevelopment.Further ReadingACM Committee on Women in Computing. Available online. URL:http://women.acm.org/. Accessed December 4, 2007.ADA Project. Available online. URL: http://women.cs.cmu.edu/ada/. Accessed December 4, 2007.Association for Women in Computing. Available online. URL:http://www.awc-hq.org/. Accessed December 4, 2007.Black Data Processing Associates. Available online. URL: http://www.bdpa.org. Accessed December 4, 2007.Dean, Cornelia. “Computer Science Takes Steps to Bring Womento the Fold.” New York Times, April 17, 2007. Available online.URL: http://www.nytimes.com/2007/04/17/science/17comp.html?_r=1&oref=slogin. Accessed December 4, 2007.Margolis, Jane, and Allan Fisher. Unlocking the Clubhouse. Cambridge,Mass.: MIT Press, 2001.National Center for Women and Information Technology. Availableonline. URL: http://www.ncwit.org/. Accessed December4, 2007.National Institute for Women in Trades, Technology & Science.Available online. URL: http://www.iwitts.com/. AccessedDecember 4, 2007.Pinkett, Randal D. “Strategies for Motivating Minorities to EngageComputers.” Carnegie Mellon University. Available online.URL: ttp://llk.media.mit.edu/papers/cmu1999.pdf. AccessedDecember 4, 2007.Yount, Lisa. A-Z of Women in Science and Math. Rev. ed. New York:Facts On File, 2007.word processingAlthough computers are most often associated with numbersand calculation, creating text documents is probablythe most ubiquitous application for desktop PCs.The term word processor was actually coined by IBMin the 1960s to refer to a system consisting of a Selectrictypewriter with magnetic tape storage. This allowed thetypist to record keystrokes (and some data such as marginsettings) on tape. Material could be corrected by being rerecorded.The tape could then be used to print as manyperfect copies of the document as required. A version usingmagnetic cards instead of tape appeared in 1969.The first modern-style word processor was marketed byLexitron and Linolex. It also used magnetic tape, but itadded a video display screen. Now the writer could seeand correct text without having to print it first. A few yearslater, a new invention, the floppy disk, became the standardstorage medium for dedicated word processing systems.The word-processing systems developed by Wang,Digital Equipment Corporation, Data General, and othersbecame a feature in large offices in the late 1970s. Thesesystems were essentially minicomputers with screens, keyboards,and printers and running a specialized softwareprogram. Because these systems were expensive (rangingfrom about $8,000 to $20,000 or more), they were notaffordable by smaller businesses. Typically, they were operatedby specially trained personnel (who became knownalso as “word processors”) to whom documents were funneledfor processing, as with the old “typing pool.”PC Word ProcessingThe first microcomputer systems had very limited memoryand storage capacity. However, by the late 1970s varioussystems using the S-100 bus and running CP/M had wordprocessingprograms, as did the Apple II and other firstgenerationPCs. However, it took the entry of the IBM PCinto the market in 1981 to make the PC a word-processingalternative for mainstream businesses. The machine hadmore memory and storage than earlier machines, and theIBM name provided reassurance to business.A number of word-processing programs were written forthe IBM PC running MS-DOS, but the market leaders wereWordStar and WordPerfect. Both programs offered basictext editing and formatting, including the ability to embedcommands to mark text for boldface, italic, and so on. Theprograms came with drivers for the more popular printers.In 1984, the Macintosh offered a new face for word processingand other applications. Using bitmapped fonts, theMac could show a good representation of the fonts and typestylesthat would be in the printed document. This “whatyou see is what you get” (WYSIWYG) approach, togetherwith the graphical user interface with mouse-driven menusmeant that users did not have to learn the often obscurecommand key sequences used in WordStar or WordPerfect.Microsoft then developed Windows as a graphical userinterface alternative to MS-DOS for IBM-compatible PCs.By 1990, Windows was rapidly replacing DOS as the operatingsystem of choice, and Microsoft Word was winning thebattle against WordPerfect, whose Windows version wasrather flawed at first.In addition to being able to visually show fonts andformatting, Word and other modern word processors arepacked with features. Some typical features today include:• different views of the document, including an outlineshowing headings down to a user-specified level• automatic table of contents and index generation• tables and multicolumn text• automatic formatting of bulleted and numbered lists• built-in and user-defined styles for headings, paragraphs,and so on.• the ability to use built-in or user-defined templatesto provide starting settings for new documents (seetemplate)• the ability to record or otherwise specify a seriesof commands to be performed automatically (seemacro)• spelling and grammar checkers• the ability to incorporate a variety of graphics imageformats in the document• automatic formatting and linking of Web hyperlinkswithin documents• the ability to import and export documents in a varietyof formats, including Web documents (see html)

World Wide Web 517• an extensive online help system including “wizards”to guide the user step-by-step through various tasksAs word processors become more extensive in theircapabilities, it has become harder to distinguish them fromprograms designed to create precise copy for publication(see desktop publishing). However, copy prepared bywriters with a word processor must generally be furtherprocessed through a desktop publishing or in-house computerizedtypography system.At the other end of the spectrum many users find thatword processors are “overkill” for making simple notes. Avariety of programs for entering simple text are available,including the Notepad program that comes with Windows.There are also applications for which plain text must beproduced, without the formatting codes added by word processors.In particular, programmers often use specializedediting programs to create source code (see text editor).TrendsToday word processing programs are generally part of anoffice software suite such as Microsoft Office, Corel Office,or Open Office. Documents created by other components ofthe suite can be embedded in word processing documents.(In Windows, object linking and embedding [OLE] is a systemthat allows for embedded documents to be automaticallyupdated and to be edited using the functions of thehost program. Thus, an Excel spreadsheet embedded in aWord document can be worked in place using the standardExcel interface.)There are also features that can facilitate collaborationbetween workers in a networked office, such as by keepingtrack of revisions made by various people working on thesame document.A new alternative is the free (or low-cost) online wordprocessor such as Google Docs & Spreadsheets and ZohoWriter. These products can be used from any Web browserand facilitate the central storage of documents for mobileusers (see application service provider).As with other applications, word processors are increasinglybeing integrated with the Web, and include the abilityto create HTML documents. In turn, the programs specificallydesigned for creating HTML documents now havemany word-processor features including templates, styles,and the visual representation of the page.Further ReadingCox, Joyce, and Joan Preppernau. Microsoft Office Word 2007 Stepby Step. Redmond, Wash.: Microsoft Press, 2007.Google Docs & Spreadsheets. Available online. URL: http://www.docs.google.com. Accessed August 23, 2007.Kunde, Brian. “A Brief History of Word Processing (Through1986).” Available online. URL: http://www.stanford.edu/~bkunde/fb-press/articles/wdprhist.html. Accessed August23, 2007.Open Office.org. Available online. URL: http://www.openoffice.org/. Accessed August 23, 2007.Petrie, Michael. “A Potted History of WordStar.” Available online.URL: http://www.wordstar.org/wordstar/history/history.htm.Accessed August 23, 2007.Zoho Writer (online word processor). Available online. URL:http://writer.zoho.com/jsp/home.jsp?serviceurl=%2Findex.do. Accessed August 23, 2007.workstationLike minicomputer, workstation is a rather slippery termwhose meaning and significance has changed somewhatwith the growing power of desktop PCs.In the late 1960s and 1970s, most “personal” computingwas done by individuals connected to time-sharing mainframesor minicomputers by terminals. Generally, the terminalscould only display text, not graphics.However, researchers at the Xerox Palo Alto ResearchCenter (PARC) began to develop a more powerful computerfor individual use (see Englebart, Douglas and Kay,Alan). The Xerox Alto had a high-resolution bitmappedgraphics display and a mouse-controlled graphical userinterface. While it was expensive and not very successfulcommercially, the Alto set the stage for the Macintosh in1984 and for Microsoft Windows.Although the desktop PCs of the 1980s such as the IBMPC had some graphics capabilities, the machines lacked thecapacity for graphics-intensive applications such as engineeringdesign and the generation of movie effects. Ledby Sun and Silicon Graphics (SGI), the high-performancegraphics workstation emerged as a distinctive product category.These machines used relatively powerful microprocessors(such as the Sun SPARC and the MIPS) with instructionsets optimized for speed (see risc). These systems generallyran UNIX as their operating system.However, by the late 1990s, ordinary desktop PCs werecatching up to dedicated workstations in terms of processingpower and graphics features. By 2002, a desktop PCcosting about $2,000 offered a 2-GB processor, 256 MB ofRAM, 120 GB hard drive, and an optimized 3D graphicscard that can drive displays up to 1600 by 1200 pixels ormore. These systems can run Windows NT or XP, or, forusers preferring UNIX, Linux offers a robust and inexpensiveoperating system. This sort of system rivals the capabilitiesof a dedicated workstation while offering all of theversatility of a general-purpose PC. As a result, the termworkstation today refers more to a way of using a computerthan to a specific class of hardware. Machines are thoughtof as workstations if they emphasize graphics performanceand are dedicated to particular activities such as science,imaging, engineering, design (see also computer-aideddesign and manufacturing), or video editing.Further ReadingGoldberg, Adele. A History of Personal Workstations. Reading,Mass.: Addison-Wesley/ACM, 1988.Sun Microsystems. The New User’s Guide to Sun Workstation. NewYork: Springer-Verlag, 1991.World Wide WebIn little more than a decade the World Wide Web hasbecome nearly as ubiquitous as the telephone and hasbecome for many a preferred medium for shopping, news,entertainment, and education. Some cultural observersbelieve that this vast system of linked information may behaving an impact on society as great as that of the inventionof the printing press more than five centuries earlier.

518 World Wide WebBy the beginning of the 1990s, the Internet had becomewell established as a means of communication betweenrelatively advanced computer users, particularly scientists,engineers, and computer science students—primarily usingUNIX-based systems (see unix). A number of services usedthe Internet protocol (see tcp/ip) to carry messages or data.These included e-mail, file transfer protocol (see ftp) andnewsgroups (see netnews and newsgroups). A Wide AreaInformation Service (WAIS) even provided a protocol forusers to retrieve information from databases on remotehosts. Another interesting service, Gopher, was developedat the University of Minnesota in 1991. It used a system ofnested menus to organize documents at host sites so theycould be browsed and retrieved by remote users.Gopher was quite popular for a few years, but it wouldsoon be overshadowed by a rather different kind of networkedinformation service. A physicist/programmer (seeBerners-Lee, Tim) working at CERN, the European particlephysics laboratory in Switzerland had devised in 1989a system that he eventually called the World Wide Web(sometimes called WWW or W3). By 1990, he was runninga prototype system and demonstrating it for CERNresearchers and a few outside participants.Using the WebThe Web consists essentially of three parts. Berners-Leedevised a markup language: that is, a system for indicatingdocument elements (such as headers), text characteristics,and so on (see html). Any document could be linkedto another (see hypertext and hypermedia) by specifyingthat document’s unique address (called a UniformResource Locator or URL) in a request. Berners-Lee definedthe HyperText Transport Protocol, or HTTP, to handle thedetails needed to retrieve documents. (Although HTTP ismost often used to retrieve HTML-formatted Web documents,it can also be used to specify documents using otherprotocols, such as ftp, news, or Gopher.)A program (see Web server) responds to requests fordocuments sent over the network (usually the Internet, thatis, TCP/IP). The requests are issued by a client program asa result of the user clicking on highlighted links or buttonsor specifying addresses (see Web browser). The browserin turn interprets the HTML codes on the page to display itcorrectly on the user’s screen.At first the Web had only text documents. However,thanks to Berners-Lee’s flexible design (see client-servercomputing) new, improved Web browsers could be createdand used with the Web as long as they followed therules for HTTP. The most successful of these new browserswas Mosaic, created by Marc Andreesen at the NationalCenter for Supercomputing Applications. NCSA Mosaic wasavailable for free download and could run on Windows,Macintosh, and UNIX-based systems. Mosaic not only dispensedwith the text commands used by most of the firstbrowsers, it also had the ability to display graphics andplay sound files. With Mosaic the text-only hypertext of theearly Web rapidly became a richer hypermedia experience.And thanks to the ability of browsers to accept modules tohandle new kinds of files (see plug-in), the Web could alsoaccommodate real-time sound and video transmissions (seestreaming).In 1994, Andreessen left NCSA and co-founded a companycalled Netscape Communications, which improvedand commercialized Mosaic. Microsoft soon entered witha competitor, Internet Explorer; today these two browsersdominate the market with Microsoft having taken thelead. Together with relatively low-cost Internet access(see modem and internet service provider) these userfriendlyWeb browsers brought the Web (and thus theunderlying Internet) to the masses. Schools and librariesbegan to offer Web access while workplaces began to useinternal webs to organize information and organize operations.Meanwhile, companies such as the on-line booksellerAmazon.com demonstrated new ways to deliver traditionalproducts, while the on-line auction site eBay took advantageof the unique characteristics of the on-line medium toredefine the auction.The burgeoning Web was soon offering millions ofpages, especially as entrepreneurs began to find additionalbusiness opportunities in the new medium (see e-commerce).Two services emerged to help Web users makesense of the flood of information. Today users can searchfor words or phrases (see search engine) or browsethrough structured topical listings (see portal). Estimatesfrom various sources suggest that as of 2007 approximately1.2 billion people worldwide access the Web, with usageincreasing most rapidly in the emerging industrial superpowersof India and China.Impact and TrendsThe Web is rapidly emerging as an important news medium(see journalism and the computer industry). Themedium combines the ability of broadcasting to reach manypeople from one point with the ability to customize contentto each person’s preferences. Traditional broadcastingand publishing are constrained by limited resources andthe need for profitability, and thus the range and diversityof views made available tend to be limited. With the Web,anyone with a PC and a connection to a service providercan put up a Web site and say just about anything. Millionsof people now display aspects of their lives and interests ontheir personal Web pages (see blogs and blogging). TheWeb has also provided a fertile medium for the creation ofonline communities (see social networking and virtualcommunity) while contributing to significant issues (seeprivacy in the digital age).As the new century continues, the Web is proving itselfto be truly worldwide, resilient, and adaptable to many newcommunications and media technologies (see digital convergence).Nevertheless, the Web faces legal and politicalchallenges (see censorship and the Internet, and intellectualproperty and computing) as well as technicalchallenges (see semantic Web and Web 2.0).Further ReadingBerners-Lee, Tim. Weaving the Web: The Original Design and UltimateDestiny of the World Wide Web. New York: Harperbusiness,2000.

Wozniak, Steven 519Gillies, James, and Robert Cailliau. How the Web Was Born: TheStory of the World Wide Web. New York: Oxford UniversityPress, 2000.Internet Society. Available online. URL: http://www.isoc.org.Accessed August 23, 2007.Internet World Stats. Available online. URL: http://www.internetworldstats.com/stats.htm. Accessed August 23, 2007.Wozniak, Steven(1950– )AmericanComputer Inventor and EngineerSteve Wozniak, often known as “Woz,” cofounded Applecomputer and designed the Apple II, one of the first popularpersonal computers.Born on August 11, 1950, in San Jose, California, Wozniakgrew up to be a classic “electronics whiz.” He built aworking electronic calculator when he was 13, winning thelocal science fair. After graduating from Homestead HighSchool, Wozniak tried community college but quit to workwith a local computer company. Although he then enrolledin the University of California, Berkeley, to study electronicengineering and computer science, he dropped out in 1971to go to work again, this time as an engineer at Hewlett-Packard, at that time one of the most successful companiesin the young Silicon Valley.By the mid-1970s, Wozniak was in the midst of a technicalrevolution in which hobbyists explored the possibilitiesof the newly available microprocessor or “computeron a chip.” A regular attendee at meetings of the HomebrewComputer Club, Wozniak and other enthusiasts wereexcited when the MITS Altair, the first complete microcomputerkit, came on the market in 1975. The Altair, however,had a tiny amount of memory, had to be programmed bytoggling switches to input hexadecimal codes (rather likethe ENIAC), and had very primitive input/output capabilities.Wozniak decided to build a computer that would bemuch easier to use—and more useful.Wozniak’s prototype machine, the Apple I, had a keyboardand could be connected to a TV screen to provide avideo display. He demonstrated it at the Homebrew ComputerClub and among the interested spectators was hisfriend Steve Jobs. Jobs had a more entrepreneurial interestthan Wozniak, and spurred him to set up a business tomanufacture and sell the machines. Together they foundedApple Computer in June 1976. Their “factory” was Jobs’sparents’ garage, and the first machines were assembled byhand.Wozniak designed most of the key parts of the Apple,including its video display and later, its floppy disk interface,which is considered a model of elegant engineering tothis day. He also created the built-in operating system andBASIC interpreter, which were stored in read-only memory(ROM) chips so the computer could function as soon as itwas turned on.In 1981, just as the Apple II was reaching the peak ofits success, Wozniak was almost killed in a plane crash. Hetook a sabbatical from Apple to recover, get married, andreturn to UC Berkeley (under an assumed name!) to finishhis B.S. in electrical engineering and computer science.Wozniak’s life changes affected him in other ways. AsApple grew and became embroiled in the problems of largecompanies, “Woz” sold large amounts of his Apple stock andgave the money to Apple employees that he thought had notbeen properly rewarded for their work. Later in the 1980s,he produced two rock festivals that lost $25 million, whichhe paid out of his own money. He was quoted as saying, “I’drather be liked than rich.” He left Apple for good in 1985and founded Cloud Nine, an unsuccessful company thatdesigned remote control and “smart appliance” hardware.During the 1990s, Wozniak organized a number ofcharitable and educational programs, including cooperativeactivities with people in the former Soviet Union. He particularlyenjoyed classroom teaching, bringing the excitementof technology to young people. In 1985, Wozniak receivedthe National Medal of Technology.Further ReadingCringely, Robert X. Accidental Empires: How the Boys of Silicon ValleyMake Their Millions, Battle Foreign Competition, and StillCan’t Get a Date. Reading, Mass.: Addison-Wesley, 1992.Freiberger, Paul, and Michael Swaine. Fire in the Valley: the Makingof the Personal Computer. 2nd ed. New York: McGraw-Hill,1999.Kendall, Martha E. Steve Wozniak, Inventor of the Apple Computer.2nd rev. ed. Los Gatos, Calif.: Highland Publishing, 2001.Woz.org [Steve Wozniak’s Home Page]. Available online. URL:www.woz.org. Accessed August 27, 2007.Wozniak, Steve, and Gina Smith. iWoz: From Computer Geek toCult Icon: How I Invented the Personal Computer, Co-FoundedApple, and Had Fun Doing It. New York: W. W. Norton, 2006.

XXMLSeveral markup languages have been devised for specifyingthe organization or format of documents. Today the mostcommonly known markup language is the Hypertext MarkupLanguage (see html, dhtml, and xhtml), which is the organizational“glue” of the Web (see World Wide Web).HTML is primarily concerned with rendering (displaying)documents. It describes structural features of documents(such as headers, sections, tables, and frames), butit does not really convey the structure of the informationwithin the document. Further, HTML is not extensible—that is, one can’t define one’s own tags and use them as partof the language. XML, or Extensible Markup Language, isdesigned to meet both of these needs. In effect, while HTMLis a descriptive coding scheme, XML is a scheme for creatingdata definitions and manipulating data within documents.(XML can be viewed as a subset of the powerful and generalizedSGML, or Standard Generalized Markup Language.)The basic building block of XML is the element, whichcan be used to define an entity (rather like a databaserecord). For example, the following statement:Babe RuthLou GehrigXML text is bracketed by tags as with HTML. The“team” element has an attribute called “name” that isassigned the value “New York Yankees.” (Attribute valuesmust be enclosed in quote marks.) It also contains a nestedelement called players, which in turn defines player names,Babe Ruth and Lou Gehrig. The elements are defined atthe beginning of the XML document by a DTD (DocumentType Definition), or such a definition can be “included”from another file.XML is currently supported by the leading Web browsers.In effect, it includes HTML as a subset, or more accuratelyXHTML (HTML conformed to XML 1.0 standards)(see html, dhtml, and xhtml). Thus, XML documentscan be properly rendered by browsers, while applicationsthat are XML-enabled (or that use XML-aware ActiveX controlsor similar Java facilities, for example) can parse theXML and identify the data structures and elements in thedocument. Together with programming languages such asJava and facilities such as SOAP (Simple Object Access Protocol),XML can be used to create applications that connectservers and documents across the Internet—it is rapidlybecoming the data “glue” that holds Web sites together.XML can be viewed as part of a trend to make data “selfdescribing.”The ability to encode not just the structure butthe logical content of documents promises a growing abilityfor automated agents or “bots” to take over much of thework of sifting through the Web for desired information,bringing the Web closer to the intentions of its inventor,Tim Berners-Lee (see Berners-Lee, Tim; semantic web).Further ReadingCarey, Patrick. New Perspectives on XML. 2nd ed. Boston: CourseTechnology, 2006.520

XML 521Eisenberg, J. David. “Introduction to XML.” Available online. URL:http://www.digital-web.com/articles/introduction_to_xml.Accessed August 23, 2007.Harold, Elliotte Rusty, and W. Scott Means. XML in a Nutshell. 3rded. Sebastapol, Calif.: O’Reilly Media, 2004.Jacobs, Sas. Beginning XML with DOM and Ajax: From Novice toProfessional. Berkeley, Calif.: Apress, 2006.XML Resources. Available online. URL: http://www.softwareag.com/xml/Techn_Links/default.htm. Accessed August 23,2007.

YY2K problemSherlock Holmes once referred to a dog barking in thenight. Watson, puzzled as usual, replied that no dog hadbarked. Holmes replied that it was the nonbarking that wassignificant. The same can be said about the growing concerntoward the end of the 1990s that the year 2000 mightbring massive, disastrous failures to many of the computersystems on which society now depended for its well-being.Most programs written in the 1960s and 1970s (seemainframe and cobol) saved expensive memory space bystoring only the second two digits of year dates. After all,dates could be understood to begin with “19” for manyyears to come (although some farsighted computer scientistsdid warn of future trouble). Eventually the centurybegan to draw to an end.Although much computing activity had moved ontonewer systems by the 1990s, many large government andcorporate computer systems were still running the originalapplications or their descendents. If such a program wererun in the year 2000, it would have no way to distinguisha date in that year from a date in 1900. While the prospectof a centenarian being suddenly treated as a newborn waslikely to be more amusing than significant, what wouldhappen to a 30-year mortgage that was written in 1975and intended to come due in 2005? Would people be billedbased on a 70-year term? Many observers feared that somesystems would actually crash because they would begin togenerate nonsensical data. What, for example, might happento an air traffic control system or automated power gridsystem that used dates and times to track events?No one really knew. One problem was that there weremillions of lines of code, often written by programmerswho had long since retired. Nor was it simply a matter oflooking for references to date fields (such as in decisionstatements), because of the many ways programmers couldexpress such statements. In addition to mainframe applications,there were also the computers hardwired into devicesof all kinds including cars and airplanes (see embeddedsystem). As with the early mainframes, these systems wereoften designed with limited available memory, and thustheir programmers, too, may have been tempted to savebytes by lopping off the century years.As the fateful date approached, government agenciesand businesses began to invest billions of dollars and hireexpensive consultants to check code for “Y2K compatibility.”In the end, Y2K problems were found and fixedin the most critical systems, and the year 2000 dawnedwithout significant mishaps. (It turned out that virtually allthe embedded systems did not in fact have Y2K problems,mostly because they didn’t even track year dates.)But although the “dog didn’t bark” and in retrospectsome of the hype about Y2K seems excessive, it did leadto improvement in a great deal of software. Further, itincreased awareness of dependence on computers for somany aspects of life—a dependence that has been cast ina harsh new light by the terrorist events of September 11,2001 (see risks of computing).Further ReadingCrawford, Walt. “Y2K: Lessons from a Non-Event.” Online, vol. 25,issue 2, March 2001, 73.522

young people and computing 523Finkelstein, Anthony. “Y2K: a Retrospective View.” Computingand Control Engineering Journal, vol. 11, no. 4, August 2000,156–159. Available online. URL: http://www.cs.ucl.ac.uk/staff/A.Finkelstein/papers/y2kpiece.pdf. Accessed August 23,2007.Manion, M., and W. M. Evan. “The Y2K Problem and ProfessionalResponsibility: A Retrospective Analysis.” Technology in Society22 (August 2000): 351–387.Yahoo! Inc.Yahoo! (NASDAQ symbol: YHOO) has played an importantrole in the development of Web services. In 1994 Stanfordstudents Jerry Yang and David Filo developed the firstpopular directory of Web sites (see portal). Realizing thatthe millions of Web users flocking to their site provided anopportunity for advertising and services, the two partnersincorporated Yahoo! in 1995. (In 1996 the company wentpublic and raised $33.8 million, a significant amount ata time when the business potential of the Web was onlybeginning to be appreciated.)Yahoo! continued to grow, and the company acquireda number of other online services, which they used to provideWeb-based e-mail, Web hosting, and news. But havingflown so high, Yahoo! had far to fall when the dot-com marketbubble burst in 2001: A stock that had traded at around$130.00 per share fell as low as $4.06.However, Yahoo! proved its resilience as one of the fewearly dot-coms to survive and has continued to thrive inthe post-bubble era since 2002. The company made strategicpartnerships with telecommunications companies suchas BT and Verizon. Yahoo! entered a continuing strugglewith another Web services powerhouse (see Google) whileacquiring new media sites (such as the photo-sharing serviceFlickr and the social “bookmarking” service del.icio.us), and creating new services (see blogs and bloggingand social networking). Yahoo! also provides onlinestorefronts, competing in that venue mainly with eBay.Yahoo! has a strong international presence, which, however,led to a controversial case where the company provideduser information to Chinese authorities that led toimprisonment of two dissidents on charges of passing statesecrets. (A lawsuit by the families of the dissidents wassettled by Yahoo.)Yahoo!’s main source of revenue remains search-relatedadvertising. The company may have received a competitiveboost in 2007 with a new online advertising system called“Panama,” catching up to similar technology previouslydeployed by Google. In fiscal 2007 Yahoo! had revenue of$6.7 billion and earned about $730 million. At the timeYahoo! had about 13,600 employees.In 2008 Yahoo! became the target of a takeover bid byMicrosoft. Although this has met with at least initial rejection,rumors continued, including the possibility that TimeWarner might acquire the company and merge it with itsAOL division.Further ReadingAngel, Karen. Inside Yahoo!: Reinvention and the Road Ahead. NewYork: Wiley, 2002.Fost, Dan. “Web Portal Works to Integrate the Companies It HasAcquired.” San Francisco Chronicle, December 24, 2006, p.F1. Available online. URL: http://sfgate.com/cgi-bin/article.cgi?file=/c/a/2006/12/24/BUGUIN3TKS1.DTL. AccessedDecember 4, 2007.Kopytoff, Verne. “‘Panama System Helping Yahoo Compete.” SanFrancisco Chronicle, April 8, 2007, p. D1. Available online.URL: http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/04/08/BUGKNP3UD91.DTL. Accessed December 4, 2007.Snell, Rob. Starting a Yahoo! Business for Dummies. Hoboken, N.J.:Wiley, 2006.Wagner, Richard. Yahoo! SiteBuilder for Dummies. Hoboken, N.J.:Wiley, 2005.Yahoo! Available online. URL: http://www.yahoo.com/. AccessedDecember 4, 2007.young people and computingComputers and technology play a role in the lives of mostyoung people that many adults have difficulty comprehending.Children in industrialized countries are liable toencounter video games even before they arrive at school.Once there, they will be exposed to a considerable amountof educational software, depending on their school’s affluence(see education and computers). Upon returningfrom school, there are more sophisticated games, MySpacepages to keep updated (see social networking), sophisticatedtools for creating music and video, and, of course, theInternet in all its vast diversity. Meanwhile, a web of incessantmessages (see texting and instant messaging) islikely to keep the youngster in touch with friends.ChallengesA major positive aspect of young peoples’ involvement withcomputer technology is that, as with learning a second language,learning the “language” of the digital world is easiestfor the young. The capabilities and opportunities for creativityoffered to today’s teens are astonishing—as are manyof the impressive results that can be seen in young peoples’blogs, Web sites, and YouTube videos. It is also widelybelieved that children will need to master current andemerging technology in order to be competitive as adults.At the same time, adults and parents in particularremain concerned about the dangers and drawbacks ofteens’ pervasively digital life. A 2007 survey by the PewInternet & American Life Project found that a majority ofparents whose children were online had rules about whattheir kids could see or play—and for how long each day. Ingeneral parents seem to be becoming somewhat less enthusiasticabout their children’s online activities even as thelatter’s positive attitude toward the technology continuesto increase. Use of protective software (see Web filter) iscommon, although tech-savvy teens have a way of stayingahead of the curve of parental restrictions.Common parental concerns include:• potential exposure to online sexual predators or bullying(see cyberstalking and harassment)• viewing of inappropriate material such as pornographyand highly violent games

524 YouTube• excessive time spent online to the detriment of study,physical activity, or sleepWhile some of this concern echoes an earlier generation’smisgivings about television, the online world is farmore deeply embedded in daily life, and both opportunitiesand concerns are thus more complex (see identity in theonline world). While parents can learn more about therelevant issues, and schools can help students develop asavvy, critical attitude toward technology, communicationbetween generations will need to be an important strategyfor coping with such rapid technological change.Further ReadingBuckingham, David, and Rebekah Willett, editors. Digital Generations:Children, Young People, and the New Media. Mahwah,N.J.: Lawrence Erlbaum, 2006.Lenhart, Amanda, and Mary Madden. “Social Networking Websitesand Teens: An Overview.” Pew Internet & American LifeProject, January 7, 2007. Available online. URL: http://www.pewinternet.org/pdfs/PIP_SNS_Data_Memo_Jan_2007.pdf.Accessed December 4, 2007.———. “Teens and Technology: Youth Are Leading the Transitionto a Fully Wired and Mobile Nation.” Pew Internet &American Life Project, July 27, 2005. Available online. URL:www.pewinternet.org/pdfs/PIP_Teens_Tech_July2005web.pdf. Accessed December 4, 2007.Macgill, Alexandra Rankin. “Parent and Teenager Internet Use.”Pew Internet & American Life Project, October 24, 2007.Available online. URL: http://www.pewinternet.org/pdfs/PIP_Teen_Parents_data_memo_Oct2007.pdf. Accessed December4, 2007.Mazzarella, Sharon R., ed. Girl Wide Web: Girls, the Internet, andthe Negotiation of Identity. New York: Peter Lang, 2005.Reimer, Jeremy. “Study Shows Youth Embracing TechnologyEven More than Before.” Ars Technica, August 1, 2006. Availableonline. URL: http://arstechnica.com/news.ars/post/20060801-7401.html. Accessed December 4, 2007.Willard, Nancy E. Cyber-Safe Kids, Cyber-Savvy Teens: HelpingYoung People Learn to Use the Internet Safely and Responsibly.San Francisco, Calif.: Jossey-Bass, 2007.YouTubeSince the late 1990s, Web users (particularly younger ones)have been adept at sharing media content online (see filesharingand p2p networks). In the 2000 decade, however,the emphasis has shifted to users not merely sharing otherpeoples’ content, but creating their own (see user-createdcontent). The first part of the recipe was the availability ofubiquitous digital cameras and camcorders; the second partwas easy-to-use video-editing software; and the third partwas a Web site that could host the results.Created in 2005 by three former PayPal employees, thevideo-sharing site YouTube has been the leading venue foramateur video. Although available content includes clipsfrom movies and TV shows (some unauthorized), much ofthe most interesting content is original videos created anduploaded by users. Beyond just sharing or accessing content,users are encouraged to rate and comment on the videosthey see, and users can also subscribe to “feeds” of newmaterial that is likely to be of interest to them.By 2008 more than 83 million videos were available onYouTube—and hundreds of thousands added each day.Political InfluenceJust as political pundits were beginning to notice thatbloggers were creating parallel structures that rivaled theinfluence of the mainstream media (see journalism andcomputers), YouTube broke into the highly visual field ofpolitical advertising. Most candidates in the 2008 presidentialprimaries have put their statements and other videos onYouTube. However, other supporters soon got into the act,including the creator of a pro–Barack Obama ad that castrival Hillary Rodham Clinton in the role of Big Brother inthe classic “1984” Apple Macintosh commercial (see mashups).Political commentators and journalists have also beenactive in putting their opinions on YouTube (or commentingon those of others). Perhaps the political establishment’sbiggest nod to YouTube is the series of debates cosponsoredby CNN and YouTube, bringing together the Republicanand Democratic primary fields.YouTube has had its share of criticism: Critics havecharged the service with not sufficiently policing copyrightviolations and violent content (including videos of fightsor bullying in schools), as well as neo-Nazi propaganda,scenes of animal abuse, and videos by anti-American insurgentgroups, as well as generally tasteless exhibitionism. Afew countries and some schools have responded by blockingaccess to the service.If YouTube’s main resource is the creativity and enthusiasmof its users, its main revenue is advertising—about $15million per month by 2006. Don Tapscott and Anthony D.Williams, authors of the book Wikinomics, cite YouTube asa classic example of the new economics of mass collaborationon the Web. Google signaled its appreciation for theeconomic potential of YouTube by buying it for $1.65 billionin late 2006.Further ReadingFah, Chad. How to Do Everything with YouTube. Emeryville, Calif.:McGraw-Hill Osborne, 2007.Miller, Michael. YouTube 4 You. Indianapolis: Que, 2007.Sahlin, Doug. YouTube for Dummies. Indianapolis: Wiley, 2007.YouTube. Available online. URL: http://www.youtube.com. AccessedDecember 4, 2007.Weber, Steve. Plug Your Business! Marketing on MySpace, YouTube,Blogs and Podcasts, and Other Web 2.0 Social Networks. FallsChurch, Va.: Weber Books, 2007.Winograd, Morley, and Michael D. Hais. Millennial Makeover:MySpace, YouTube, and the Future of American Politics. Piscataway,N.J.: Rutgers University Press, 2008.

ZZuse, Konrad(1910–1995)GermanEngineer, InventorGreat inventions seldom have a single parent. Althoughpopular history credits Alexander Graham Bell with thetelephone, the almost forgotten Elisha Gray invented thedevice at almost the same time. And although the ENIACis widely considered to be the first practical electronic digitalcomputer (see Eckert, J. Presper and Mauchly, John)another American inventor built a smaller machine onsomewhat different principles that also has a claim to being“first” (see Atanasoff, John). Least known of all is KonradZuse, perhaps because he did most of his work in a nationthat was plunging the world into war.Zuse was born on June 22, 1910, in Berlin. He studiedcivil engineering at the Technische Hochschule Berlin-Charlottenburg, receiving his degree in 1935. One of histasks in engineering was performing calculations of thestress on structures such as bridges. At the time these calculationswere carried out by going through a series of stepson a form over and over again, plugging in the data andcalculating by hand or using an electromechanical calculator.Like other inventors before him, Zuse began to wonderwhether he could build a machine that could carry outthese repetitive steps automatically.Zuse was unaware of the nearly forgotten work ofCharles Babbage and that of other inventors in Americaand Britain who were beginning to think along the samelines (see Babbage, Charles). With financial help from hisparents (and the loan of their living room), Zuse began toassemble his first machine from scrounged parts. His firstmachine, the Z1, was completed in 1938. The machine usedslotted metal plates with holes and pins that could slide tocarry out binary addition and other operations (in usingthe simpler binary system rather than decimal, Zuse wasdeparting from other calculator designers).The Z1 had trouble storing and retrieving numbers andnever worked well. Undeterred, Zuse began to develop anew machine that used electromechanical telephone relays(a ubiquitous component that was also favored by HowardAiken [see Aiken, Howard]). The new machine workedmuch better, and Zuse successfully demonstrated it at theGerman Aerodynamics Research Institute in 1939.With World War II under way, Zuse was able to obtainfunding for his Z3, which was able to carry out automaticsequences from instructions (Zuse used discarded moviefilm instead of punched tape). The machine used 22-bitwords and had 600 relays in the calculating unit and1,800 for the memory. However, the machine could not dobranching or looping the way modern computers can. Itwas destroyed in a bombing raid in 1944. Meanwhile, Zuseused spare time from his military duties at the Henschelaircraft company to work on the Z4, which was completedin 1949. This machine was more fully programmable andwas comparable to Howard Aiken’s Mark I.By that time, however, Zuse’s electromechanical technologyhad been surpassed by the fully electronic vacuum tubecomputers such as the ENIAC and its successors. (Zuse hadconsidered vacuum tubes but had rejected them, believingthat their inherent unreliability and the large numbers525

526 Zuse, Konradneeded would make them impracticable for a large-scalemachine.) During the 1950s and 1960s, Zuse ran a computercompany, ZUSE KG, which eventually produced electronicvacuum tube computers.Zuse’s most interesting contribution to computer sciencewould not be his hardware but a programming languagecalled Plankalkül or “programming calculus.” Although thelanguage was never implemented, it was far in advance ofits time in many ways. It started with the radically simpleconcept of grouping individual bits to form whatever datastructures were desired. It also included program modulesthat could operate on input variables and store their resultsin output variables (see procedures and functions). Programswere written using a notation similar to mathematicalmatrices.Zuse labored in obscurity even within the computer sciencefraternity. However, toward the end of his life his workbegan to be publicized. He received numerous honorarydegrees from European universities as well as awards andmemberships in scientific and engineering academies. Zusealso took up abstract painting in his later years. He died onDecember 18, 1995.Further ReadingBauer, F. L., and H. Wössner. “The Plankalkül of Konrad Zuse: AForerunner of Today’s Programming Languages.” Communicationsof the ACM, vol. 15, 1972, 678–685.Lee, J. A. N. Computer Pioneers. Los Alamitos, Calif.: IEEE ComputerSociety Press, 1995.Zuse, Konrad. The Computer—My Life. New York: Springer-Verlag,1993.

Appendix IBibliographies and Web ResourcesThe following selections provide reference material andresources to supplement the Further Reading selections atthe conclusion of the majority of entries in this book.Print Resources2008 Software Industry Directory. Greenwood Village, Colo.:Webcom Communications, 2007.Bidgoli, Hassan, ed. The Internet Encyclopedia. New York: Wiley,2003.Cortada, James W. Historical Dictionary of Data Processing. 3vols. New York: Greenwood Press, 1987.Daintith, John, and Edmund Wright. The Facts On File Dictionaryof Computer Science. Rev. ed. New York: Facts On File,2006.De Palma, Paul, ed. Annual Editions: Computers in Society 08/09.Guilford, Conn.: McGraw-Hill/Dushkin, 2007.Downing, Douglas, Michael Covington, and Melody MauldinCovington. Dictionary of Computer and Internet Terms. 9thed. Hauppauge, N.Y.: Barron’s, 2006.Hackett, Edward J. et al., eds. The Handbook of Science and TechnologyStudies. 3rd ed. Cambridge, Mass.: MIT Press, 2007.Henderson, Harry. A to Z of Computer Scientists. New York: FactsOn File, 2003.Knee, Michael. Computer Science and Computing: A Guide to theLiterature. Greenwich, Colo.: Libraries Unlimited, 2005.Lee, John A. N. International Biographical Dictionary of ComputerPioneers. New York: Routledge, 1995.Lubar, Stephen. InfoCulture: The Smithsonian Book of InformationAge Inventions. Boston: Houghton Mifflin, 1993.McGraw-Hill Encyclopedia of Science & Technology. 10th ed. NewYork: McGraw-Hill, 2007.Sun Technical Publications. Read Me First!: A Style Guide for theComputer Industry. 2nd ed. Upper Saddle River, N.J.: PrenticeHall, 2003.Web ResourcesAbout.com. “Computing and Technology.” Available online.URL: http://about.com/compute/. Accessed December 6,2007.Academic Info: Computer Science & Computer Engineering.Available online. URL: http://www.academicinfo.net/compsci.html. Accessed December 6, 2007.ACM Computing Reviews. Available online. URL: http://www.reviews.com/home.cfm. Accessed December 6, 2007.ACM Digital Library. Available online. URL: http://portal.acm.org/dl.cfm. Accessed December 6, 2007.ACM Tech. News. Available online. URL: http://technews.acm.org/current.cfm. Accessed December 7, 2007.Ars Technica. Available online. URL: http://arstechnica.com/.Accessed December 6, 2007.ClickZ Stats. Available online. URL: http://www.clickz.com/stats/. Accessed December 6, 2007.Cnet. Available online. URL: http://www.cnet.com. AccessedDecember 6, 2007.Collection of Computer Science Bibliographies. Available online.URL: http://liinwww.ira.uka.de/bibliography/. AccessedDecember 7, 2007.Computer Dictionaries, Acronyms, and Glossaries. Availableonline. URL: http://www.compinfo-center.com/tpdict-t.htm.Accessed December 6, 2007.Computer History Museum. Available online. URL: http://www.computerhistory.org/. Accessed December 6, 2007.Connected: An Internet Encyclopedia. Available online. URL:http://freesoft.org/CIE/. Accessed December 7, 2007.FOLDOC (Free On-Line Dictionary of Computing). Availableonline. URL: http://foldoc.org/. Accessed December 7,2007.How Stuff Works. Available online. URL: http://www.howstuffworks.com/.Accessed December 6, 2007.IDG (International Data Group). Available online. URL: http://www.idg.net/. Accessed December 7, 2007.IEEE Annals of the History of Computing. Available online.URL: http://www.computer.org/annals/. Accessed December6, 2007.InfoWorld. Available online. URL: http://www.infoworld.com.Accessed December 6, 2007.Internet News. Available online. URL: http://www.internetnews.com/. Accessed December 6, 2007.Pew/Internet. Available online. URL: http://www.pewinternet.org. Accessed December 6, 2007.527

528 Appendix IRed Herring: The Business of Technology. Available online. URL:http://www.redherring.com/pages/pagenotfound/. AccessedDecember 7, 2007.Slashdot. Available online. URL: http://slashdot.org. AccessedDecember 6, 2007.Smithsonian Institution. Science and Technology Division,Information Technology. Available online. URL: http://www.si.edu/Encyclopedia_SI/science_and_technology/Information_Technology.htm. Accessed December 6, 2007.Webopedia. Available online. URL: http://www.webopedia.com/.Accessed December 6, 2007.Wikipedia. Available online. URL: http://en.wikipedia.org.Accessed December 6, 2007.Yahoo! Finance. Available online. URL: http://biz.yahoo.com.Accessed December 7, 2007.Yahoo! Science: Computer Science. Available online. URL:http://dir.yahoo.com/Science/Computer_Science/. AccessedDecember 6, 2007.ZDNet. Available online. URL: http://www.zdnet.com. AccessedDecember 7, 2007.

Appendix IIA Chronology of ComputingThe following chronology lists some significant events in thehistory of computing. Although the first calculators (i.e.,the abacus) were known in ancient times, the chronologybegins with the development of modern mathematics and thefirst calculators in the 17th century.1617• John Napier published an explanation of “Napier’s bones,”a manual aid to calculation based on logarithms, and theancestor to the slide rule.1624• William Schickard invented a mechanical calculator thatcan perform automatic carrying during addition and subtraction.It can also multiply and divide by repeated additionsor subtractions.1642• Blaise Pascal invented a calculator that he calls the Pascaline.Its improved carry mechanism used a weight to allowit to carry several places. A small batch of the machines wasmade, but it did not see widespread use.1673• Gottfried Wilhelm Leibniz (co-inventor with Isaac Newtonof the calculus) invented a calculator called the LeibnizWheel. He also wrote about the binary number system thateventually became the basis for modern computation.1786• J. H. Muller invented a “difference engine,” a machine thatcan solve polynomials by repeated addition or subtraction.1822• Charles Babbage designed and partially built a much moreelaborate difference engine.1832• Babbage sketched out a detailed design for the AnalyticalMachine. This machine was to have been programmed bypunched cards, storing data in a mechanical memory, andeven including a printer. Although it was not built duringhis lifetime, Babbage’s machine embodied most of the conceptsused in modern computers.1843• Ada Lovelace provided extensive commentary on a book byBabbage’s Italian supporter Menabrea. Besides being thefirst technical writer, Lovelace also wrote what might beconsidered the world’s first computer program.1844• Samuel Morse demonstrated the electromagnetic telegraphby sending a message from Washington to Baltimore. Thetelegraph inaugurated both electric data transmission andthe use of a binary character code (dots and dashes).1850• Amedee Mannheim created the first modern slide rule. Itwill become an essential accessory for engineers and scientistsuntil the inexpensive electronic calculator arrived inthe 1970s.1854• George Boole’s book The Laws of Thought described what isnow called Boolean algebra. Boolean operators are essentialfor the branching statements and loops that controlthe operation of computer programs.1884• W. S. Burroughs marketed his first adding machine, beginningwhat will become an important calculator (and later,computer) business.1890• Herman Hollerith’s punched card tabulator enabledthe U.S. government to complete the 1890 census in recordtime.1896• Hollerith founded the Tabulating Machine Company,which will become the Computing, Tabulating, and Record-529

530 Appendix IIing company (CTR) in 1911. In 1924, it will become InternationalBusiness Machines (IBM).1904• J. A. Fleming invented the diode vacuum tube. Together withLee de Forest’s invention of the triode two years later, thisdevelopment defined the beginnings of electronics, offering aswitching mechanism much faster than mechanical relays.1919• The “flip-flop” circuit was invented by two American physicists,W. H. Eccles and R. W. Jordan. The ability of the circuitto switch smoothly between two (binary) states wouldform the basis for computer arithmetic logic units.1921• Karl Capek’s play R.U.R. introduced the term robot. Robotswill become a staple of science fiction “pulps” starting in the1930s.1930• Vannevar Bush’s elaborate analog computer, the DifferentialAnalyzer, went into service.1936• Alonzo Church developed the lambda calculus, which canbe used to demonstrate the computability of mathematicalproblems.• Konrad Zuse built his first computer, a mechanical machinebased on the binary system.1937• Alan Turing provided an alternative (an equivalent) demonstrationof computability through his Turing Machine, animaginary computer that can reduce any computable problemto a series of simple operations performed on an endlesstape.• Bell Laboratories mathematician George Stibitz createdthe first circuit that could perform addition by combiningBoolean operators.1938• In a key development in robotics, Doug T. Ross, an Americanengineer, created a robot that can store its experience inmemory and “learn” to navigate a maze.• G. A. Philbrick developed an electronic version of the analogcomputer.• Working in a garage near Stanford University, WilliamHewlett and David Packard began to build audio oscillators.They called their business the Hewlett-Packard Company.Fifty years later, the garage would be preserved as a historicallandmark.1939• John Atanasoff and Clifford Berry built a small electronicbinary computer called the Atanasoff-Berry Computer(ABC). A 1973, court decision would give this machine precedenceover ENIAC as the first electronic digital computer.• George Stibitz built the Complex Number Calculator, whichis controlled by a keyboard and uses relays.1940• Claude Shannon introduced the fundamental concepts ofdata communications theory.• George Stibitz demonstrated remote computing by controllinghis Complex Number Calculator in New York from aTeletype terminal at Dartmouth College in New Hampshire.1941• Working in isolation in wartime Germany, Konrad Zusecompleted the Z3. Although still mechanical rather thanelectronic, the machine used sophisticated floating-pointnumeric data.1943• The British-built Colossus, an electronic (vacuum tube) special-purposecomputer that can rapidly analyze permutationsto crack the German Enigma cipher.1944• Howard Aiken completed the Harvard Mark I, a large programmablecalculator (or computer) using electromechanicalrelays.• John von Neumann and Stanislaw Ulam developed theMonte Carlo method of probabilistic simulation, a toolthat would find widespread use as computer power becomesavailable.1945• Zuse continued computer development and created asophisticated matrix-based programming language calledPlankalkül.• Vannevar Bush envisioned hypertext and knowledge linkingand retrieval in his article “As We May Think.”• Alan Turing developed the concept of using proceduresand functions (subroutines) called with parameters. Histeam also developed the Pilot ACE (Automatic ComputingEngine), which would help the development of a Britishcomputer industry.1946• ENIAC went into service. Developed by J. Presper Eckertand John Mauchly, the machine is widely considered tobe the first large-scale electronic digital computer. It used18,000 vacuum tubes.• In the “Princeton Reports” based upon the ENIAC work, Johnvon Neumann, together with Arthur W. Burks and HermanGoldstine described the fundamental operations of moderncomputers including the stored program concept—the holdingof all program instructions in memory, where they can bereferred to repeatedly and even manipulated like other data.1947• The Association for Computing Machinery (ACM) wasfounded.

Appendix II 531•Eckert and Mauchly formed the Eckert-Mauchly Corporationfor commercial marketing of computers based on theENIAC design.John von Neumann began development of the EDVAC(Electronic Discrete Variable Automatic Calculator) forthe U.S. government’s Ballistic Research Laboratory. Thismachine, completed in 1952, would be the first to use programscompletely stored in memory and able to be changedwithout physically changing the hardware.Richard Hamming developed error correction algorithms.Alan Turing’s paper on “Intelligent Machinery” began layingthe groundwork for artificial intelligence research.In Britain, Manchester University built the first electroniccomputer that can store a full program in memory. It wascalled “baby” because it was a small test version of a plannedlarger machine. For its main memory it used a CRT-like tubeinvented by F. C. Williams.IBM under Thomas J. Watson, Sr. decided to enter the newcomputer field in a big way by beginning to develop theSelective Sequence Electronic Calculator (SSEC) as a competitorto ENIAC and the Harvard Mark I. The huge machineused thousands of both vacuum tubes and relays.Tom Kilburn and M. H. A. Newman invented the index register,which would be used to keep track of the current locationin memory of instructions or data.The transistor was invented at Bell Labs by John Bardeen,Walter Brattain, and William Shockley. The solid-statedevice could potentially replicate all the functionality of thevacuum tube with much less size and power consumption.It would be some time before it was inexpensive enough tobe used in computers, however.Norbert Wiener coined the term cybernetics to refer to controland feedback systems.Claude Shannon formally introduced statistical informationtheory.•••••••••1949• The Cambridge EDSAC demonstrated versatile stored-programcomputing. Meanwhile, Eckert and Mauchly workon BINAC, a successor/spinoff of ENIAC for Northrop AircraftCorporation.• Frank Rosenblatt developed the perceptron, the first form ofneural network, for solving pattern-matching problems.• An Wang patented “core memory,” using an array of magnetizedrings and wires, which would become the main memory(RAM) for many mainframes in the 1950s.1950• Alan Turing proposed the Turing Test as a way to demonstrateartificial intelligence.• Development began of the high-speed computers Whirlwindand SAGE for the U.S. military. The military also began touse computers to run war games or simulations.• Claude Shannon outlined the algorithms for a chess-playingprogram that could evaluate positions and perform heuristiccalculations. He would build a chess-playing computercalled Caissac.• Japan began development of electronic computers under theleadership of Hideo Yamashita, who would build the TokyoAutomatic Calculator.• Approximately 60 electronic or electromechanical computerswere in operation worldwide. Each was built “by hand”as there were no production models yet.1951• Eckert and Mauchly marketed Univac I, generally consideredthe first commercial computer (although the FerrantiMark I is sometimes given co-honors).• An Wang founded Wang Laboratories, which would becomea major computer manufacturer through the 1970s.• Grace Hopper at Remington Rand coined the word compilerand began developing automatic systems for creatingmachine codes from higher-level instructions.1952•••Alick Glennie developed autocode, generally considered tobe the first true high-level programming language.Magnetic core memory began to come into use.election night a Univac I predicted that Dwight D. Eisenhowerwould win the 1952 U.S. presidential election. Itmade its prediction an hour after the polls closed, but itsfindings were not released at first because news analystsinsisted the race was closer.MANIAC was On developed to do secret nuclear research inLos Alamos.The IBM 701 went into production. It was one of the firstcomputers to use magnetic tape drives as primary meansof data storage.IBM was accused of violating the Sherman Antitrust Actin its computer business. Litigation in one form or anotherwould drag on until 1982.John von Neumann described self-reproducing automata.The symbolic assembler was introduced by NathanielRochester.IBM and Remington Rand (Univac) dominated the youngcomputer industry.••••••1954• The ibm 650 was marketed. It was the first truly mass-producedcomputer, and relatively affordable by businesses andindustries. It used a magnetic drum memory.• In Britain, the Lyons Electronic Office (LEO) became thefirst integrated computer system for use for business applications,primarily accounting and payroll.1955• Grace Hopper created Flow-matic, the first high-level languagedesigned for business applications of computers.• The Computer Usage Company (CUC) was founded by JohnW. Sheldon and Elmer C. Kubie. It is considered to be thefirst company devoted entirely to developing computer softwarerather than hardware.• Bendix marketed the G-15, its competitor to the IBM 650 inthe “small” business computer market.

532 Appendix II• Users of the new IBM 704 mainframe, frustrated at thelack of technical supported, formed the first computer usergroup, called SHARE.• The large ibm 705 mainframe is marketed by IBM. It usesmagnetic core memory.1956• The IBM 704 and Univac 1103 introduced a new generationof commercial mainframes with magnetic core storage.• John McCarthy coined the term artificial intelligence,or AI.• The Dartmouth AI conference brought together leadingresearchers such as McCarthy, Marvin Minsky, HerbertSimon, and Allen Newell. It would set the agenda for the field.• Newell, Shaw, and Simon developed Logic Theorist, the firstprogram that can prove theorems.• A. I. Dumey described hashing, a procedure for quicklysorting or retrieving data by assigning calculated values.• The infant transistor industry began to grow as companiessuch as IBM began to build transistorized calculators.• IBM signed a consent decree ending the 1952 antitrust complaintby restricting some of its business practices in sellingmainframe computers.1957•John Backus and his team released fortran, which wouldbecome the most widely used language for scientific computingapplications.Digital Equipment Corporation (DEC) was founded by KenOlsen and Harlan Anderson. The company’s agenda involvedthe development of a new class of smaller computer, theminicomputer.Minicomputer development would be inspired by the MITTX-0 computer. While not yet a “mini,” the machine was thefirst fully transistorized computer.The hard drive came into service in ibm’s 305 RAMAC.IBM developed the first dot matrix printer.••••1958• The I/O interrupt used by devices to signal their needs tothe CPU was developed by ibm. It would be used later inpersonal computers.• China began to build computers based on Soviet designs,which in turn had been based upon American and Britishmachines.• Sperry Rand introduced the Univac II, a huge, powerful,and surprisingly reliable computer that used 5,200 vacuumtubes, 18,000 crystal diodes, and 184,000 magnetic cores.• Jack Kilby of Texas Instruments built the first integratedcircuit, fitting five components onto a half-inch piece of germanium.• As the cold war continued, the U.S. Air Force brought SAGEon-line. This integrated air defense system featured realtimeprocessing and graphics displays.1959• John McCarthy developed Lisp, a language based onAlonzo Church’s lambda calculus and including extensivefacilities for list processing. It would become the favoritelanguage for artificial intelligence research.• cobol was introduced, with much of the key work andinspiration coming from Grace Hopper.• ibm marketed the 7090 mainframe, a large transistorizedmachine that could perform 229,000 additions a second. Thesmaller IBM 1401 would prove to be even more popular. IBMalso introduced a high-speed printer using type chains.• Robert Noyce of Fairchild Semiconductor built a differenttype of integrated circuit, using aluminum traces and layersdeposited on a silicon substrate.1960• Digital Equipment Corporation (DEC) marketed the PDP-1,generally considered the first commercial minicomputer.• Control Data Corporation (CDC) impressed the industrywith its CDC 1604, designed by Seymour Cray. It offeredhigh speed at considerably lower prices than ibm and theother major companies.• The Algol language demonstrated block structure for betterorganization of programs. The report on the language introducedBNF (Backus-Naur form) as a systematic descriptionof computer language grammar.• Donald Blitzer introduced PLATO, the first large-scaleinteractive computer-aided instruction system. It wouldlater be marketed extensively by Control Data Corporation(CDC).• Paul Baran of RAND developed the idea of packet-switching toallow for decentralized information networks; the idea wouldsoon attract the attention of the U.S. Defense Department.• In an advance in practical robotics, the remote-operated“Handyman” robot arm and hand was put to work in anuclear power plant.• The U.S. Navy began to develop the Naval Tactical DataSystem (NTDS) to track targets and the status of ships in acombat zone.1961• Time-sharing computer systems came into use at MIT andother facilities. Among other things, they encouraged theefforts of the first hackers to find clever things to do withthe computers.• Leonard Kleinrock’s paper “Information Flow in Large CommunicationNets” was the first description of the packetswitchingmessage transfer system that would underlie theInternet.• Arthur Samuel’s ongoing research into computer gamesdesign culminated in his checkers program reaching masterlevel. The program includes learning algorithms that canimprove its play.• The ibm STRETCH (IBM 7030) is installed at Los AlamosNational Laboratory. Its advanced “pipeline” architectureallowed new instructions to begin to be processed whilepreceding ones were being finished. It and Univac’s LARCare sometimes considered to be the first supercomputers.• IBM made a major move into scientific computing withits modular 7040 and 7044 computers, which can be used

Appendix II 533••together with the 1401 to build a “scalable” installation fortackling complex problems.Unimation introduced the industrial robot (the Unimate).Fairchild Semiconductor marketed the first commercialintegrated circuit.1962•The discipline of computer science began to emergewith the first departments established at Purdue and Stanford.MIT students created Spacewar, the first video computergame, on the PDP-1.On a more practical level, MIT programmers Richard Greenblattand D. Murphy develop TECO, one of the first texteditors.J. C. R. Licklider described the “Intergalactic Network,”a universal information exchange system that would helpinspire the development of the Internet.Douglas Engelbart invented the computer mouse at SRI.IBM developed the SABRE online ticket reservation systemfor American Airlines. The system will soon be adoptedby other carriers and demonstrate the use of networkedcomputer systems to facilitate commerce. Meanwhile, ibmearned $1 billion from its computer business, which by thenhad overtaken its traditional office machines as the company’sleading source of revenue.•••••1963• Joseph Weizenbaum’s Eliza program carried on naturalsoundingconversations in the manner of a psychotherapist.• Ivan Sutherland developed Sketchpad, the first computerdrawing system.• Reliable Metal Oxide Semiconductor (MOS) integrated circuitswere perfected, and would become the basis for manyelectronic devices in years to come, including computers forspace exploration.1964• The ibm System/360 was announced. It would become themost successful mainframe in history, with its successorsdominating business computing for the next two decades.• IBM introduced the MT/ST (Magnetic Tape/Selectric Typewriter),considered to be the first dedicated word processingsystem. While rudimentary, it allowed text to becorrected before printing.• Seymour Cray’s Control Data CDC 6600 is announced.When completed, it ran about three times faster than IBM’sSTRETCH, irritating Thomas Watson, head of the far largerIBM.• J. Kemeny and T. Kurtz developed basic to allow students toprogram on the Dartmouth time-sharing system.• At the other end of the scale, IBM introduced the complex,feature-filled PL/1 (Programming Language 1) for use withits System/360.• The American National Standards Institute (ANSI) officiallyadopted the ASCII (American Standard Code for InformationInterchange) character code.• Paul Baran of SRI wrote a paper, “On Distributed CommunicationNetworks,” further describing the implementationof packet-switched network that could route around disruptions.The work began to attract the attention of militaryplanners concerned with air defense and missile control systemssurviving nuclear attack.• Jean Sammet and her colleagues developed the first computerprogram that can do algebra.• Gordon Moore (a founder of Fairchild Semiconductor andlater, of Intel Corporation) stated that the power of CPUswould continue to double every 18 to 24 months. “Moore’slaw” proved to be remarkably accurate.1965• ibm introduced the floppy disk (or diskette) for use with itsmainframes.• Edsgar Dijkstra devised the semaphore, a variable that twoprocesses can use to synchronize their operations and aidingthe development of concurrent programming.• The APL language developed by Kenneth Iverson provideda powerful, compact, but perhaps cryptic way to formulatecalculations.• The Simula language introduced what will become knownas object-oriented programming.• The DEC PDP-8 became the first mass-produced minicomputer,with over 50,000 systems being sold. The machinebrings computing power to thousands of universities,research labs, and businesses that could not afford mainframes.Designed by Edson deCastro and engineered by GordonBell, the PDP-8 design marked an important milestoneon the road to the desktop PC.• NASA uses an IBM onboard computer to guide Geminiastronauts in their first rendezvous in space.• The potential of the expert system was demonstrated byDendral, a specialized medical diagnostic program thatbegan development by Edward Feigenbaum, Joshua Lederberg,and Bruce Buchanan.• The U.S. Defense Department’s ARPA (Advanced ResearchProjects Agency) sponsored a study of a “co-operative networkof time-sharing computers.” A testbed network wasbegun by connecting a TX-2 minicomputer at MIT via phoneline to a computer at System Development Corporation inSanta Monica, California.• Ted Nelson’s influential vision of universal knowledge sharingthrough computers introduced the term hypertext.1966•••In the first federal case involving computer crime (U.S. v.Bennett), a bank programmer is convicted of altering a bankprogram to allow him to overdraw his account.The first ACM Turing Award is given to Alan Perlis.The New York Stock Exchange automated much of its tradingoperations.1967• The memory cache (a small amount of fast memory usedfor instructions or data that are likely to be needed) wasintroduced in the IBM 360/85 series.

534 Appendix II••ibm developed the first floppy disk drive.Seymour Papert introduced Logo, a Lisp-like language thatwould be used to teach children programming conceptsintuitively.A chess program written by Richard Greenblatt of MIT,Mac Hack IV, achieved the playing skill of a strong amateurhuman player.Fred Brooks did early experiments in computer-mediatedsense perception, laying groundwork for virtual reality.••1968• Edsger Dijkstra’s little letter entitled “GO TO ConsideredHarmful” argued that the GOTO or “jump” statement madeprograms hard to read and more prone to error. The resultingdiscussion gave impetus to the structured programmingmovement. Another aspect of this movement was theintroduction of the term software engineering.• Robert Noyce, Andrew Grove, and Gordon Moore foundedIntel, the company that would come to dominate themicroprocessor industry by the early 1980s.• ibm introduced the System/3, a lower-cost computer systemdesigned for small businesses.• Bolt, Beranek and Newman (BBN) was awarded a governmentcontract to build “interface message processors” orIMPs to translate data between computers linked overpacket-switched networks.• Alan Kay prototyped the Dynabook, a concept that ledtoward both the portable computer and the graphicaluser interface.• Stanley Kubrick’s movie 2001 introduced Hal 9000, theself-aware (but paranoid) computer that kills members of adeep-space exploration crew.1969• Ken Thompson and Dennis Ritchie began work on theunix operating system. It will feature a small kernel thatcan be used with many different command shells, and willeventually incorporate hundreds of utility programs thatcan be linked to perform tasks.• Edgar F. Codd introduced the concept of the relational systemthat would form the foundation for most modern databasemanagement system.• ibm was sued by the U.S. Department of Justice for antitrustviolations. The voluminous case would finally be dropped in1982. However, government pressure may have led the computergiant to finally allow its users to buy software fromthird parties, giving a major boost to the software industry.• ARPANET is officially launched. The first four nodes of theARPANET came online, prototyping what would eventuallybecome the Internet.• SRI researchers developed Shakey, the first mobile robotthat could “see” and respond to its environment. The actualcontrol computer was separate, however, and controlled therobot through a radio link.• Neil Armstrong and Edwin Aldrin successfully made thefirst human landing on the Moon, despite problems with theonboard Apollo Guidance Computer.• The first automatic teller machine (ATM) was put in service.1970• Gene Amdahl left ibm to found Amdahl Corporation, whichwould compete with IBM in the mainframe “clone” market.• An Intel Corporation team led by Marcian E. Hoff began todevelop the Intel 4004 microprocessor.• Digital Equipment Corporation announced the PDP-11, thebeginning of a series of 16-bit minicomputers that will supporttime-sharing computing in many universities.• John Conway’s “Game of Life” popularized cellularautomata.• The ACM held its first all-computer chess tournament inNew York City. Northeastern University’s Chess 3.0 toppedthe field of six programs competing.• Charles Moore began writing programs to demonstrate theversatility of his programming language Forth.• Xerox Corporation established the Palo Alto Research Center(PARC). This laboratory will create many innovations ininteractive computing and the graphical user interface.1971•••Niklaus Wirth formally announced Pascal, a small, wellstructuredlanguage that will become the most popularlanguage for teaching computer science for the next twodecades.The IEEE Computer Society was founded.The ibm System/370 series ushered in a new generation ofmainframes using densely packed integrated circuits forboth cpu and memory.1972• Dennis Ritchie and Brian Kernighan developed c, a compactlanguage that would become a favorite for systems programming,particularly in unix.• The creation of an e-mail program for the ARPANETincluded the decision to use the at (@) key as part of e-mailaddresses.• Alan Kay developed Smalltalk, building upon SIMULAto create a powerful, seamless object-oriented programminglanguage and operating system. The language wouldeventually be influential although not widely used. Kay alsoprototyped the Dynabook, a notebook computer, but Xeroxofficials showed little interest.• Seymour Cray left CDC and founded Cray Research todevelop new supercomputer.• Intel introduced the 8008, the first commercially available8-bit microprocessor.• The 5.25-inch diskette first appeared. It would become amainstay of personal computing until it was replaced by themore compact 3.5-inch diskette in the 1990s.• Nolan Bushnell’s Atari Corp. had the first commercial computergame hit, Pong. It and its beeping cousins would soonbecome an inescapable part of every parent’s experience.1973• Alain Colmerauer and Philippe Roussel at the University ofMarseilles developed Prolog (Programming in Logic), alanguage that could be used to reason based upon a stored

Appendix II 535base of knowledge. The language would become popular forexpert systems development.• Bell Laboratories established a group to support and promulgatethe unix operating system.• The Ethernet protocol for LANs (local area networks)was developed by Robert Metcalfe.• In a San Francisco hotel lobby Vinton Cerf sketched thearchitecture for an Internet gateway on a napkin.• Don Lancaster published his “TV Typewriter” design inRadio Electronics. It would enable hobbyists to build displaysfor the soon-to-be available microcomputer.• The Boston Computer Society (BCS) was founded. It becameone of the premier computer user groups.• Gary Kildall founded Digital Research, whose CP/M operatingsystem would be an early leader in the microcomputerfield.• A federal court declared that the Eckert-Mauchly ENIACpatents were invalid because John Atanasoff had the sameideas earlier in his ABC computer.1974• The Alto graphical workstation was developed by AlanKay and others at Xerox PARC. It did not achieve commercialsuccess, but a decade later something very much like itwould appear in the form of the Apple Macintosh.• An international computer chess tournament is won by theRussian KAISSA program, which crushed the Americanfavorite Chess 4.0.• Computerized product scanners were introduced in an Ohiosupermarket.• Intel released the 8080, a microprocessor that had 6,000transistors, could execute 640,000 instructions per second,was able to access 64 kB of memory, and ran at a clock rateof 2 MHz.• David Ahl’s Creative Computing magazine began to offer anemphasis on using small computers for education and otherhuman-centered tasks.• Vinton Cerf and Robert Kahn began to publicize their tcp/ip internet protocol.• A group at the University of California, Berkeley, began todevelop their own version of the unix operating system.• The 1974 Privacy Act began the process of trying to protectindividual privacy in the digital age.1975• Fred Brooks published the influential book The MythicalMan-Month. It explained the factors that bog down softwaredevelopment and focused more attention on softwareengineering and its management.• Electronics hobbyists were intrigued by the announcementof the MITS Altair, the first complete microcomputer systemavailable in the form of a kit. While the basic kit costonly $395, the keyboard, display, and other peripherals wereextra.• MITS founder Ed Roberts also coined the term personalcomputer. Hundreds of hobbyists built the kits and yearnedfor more capable machines. Many hobbyists flocked tomeetings of the Homebrew Computer Club in Menlo Park,California.• ibm introduced the first commercially available laserprinter. The very fast, heavy-duty machine was suitableonly for very large businesses.• The first ARPANET discussion mail list was created. Themost popular topic for early mail lists was science fiction.• In Los Angeles, Dick Heiser opened what is believed to bethe first retail store to sell computers to “ordinary people.”1976• Seymour Cray’s sleek, monolithlike Cray 1 set a new standardfor supercomputers.• Whitfield Diffie and Martin Hellman announced a publickeyencryption system that allowed users to securely sendinformation without previously exchanging keys.• ibm developed the first (relatively crude) inkjet printer forprinting address labels.• Shugart Associates offered a floppy disk drive to microcomputerbuilders. It cost $390.• Steve Wozniak proposed that Hewlett-Packard fund the creationof a personal computer, while his friend Steve Jobsmade a similar proposal to Atari Corp. Both proposals wererejected, so the two friends started Apple Computer Company.• Chuck Peddle of MOS Technology developed the 6502microprocessor, which would be used in the Apple, Atari,and some other early personal computers.• Bill Gates complained about software piracy in his “OpenLetter to Hobbyists.” People were illicitly copying his BASIClanguage tapes. copy protection would soon be used in anattempt to prevent copying of commercial programs for personalcomputers.• Computer enthusiasts found an erudite forum in themagazine Dr. Dobb’s Journal of Computer Calisthenics andOrthodontia: Running Light without Overbyte. The more mainstreamByte magazine also became a widely known forumfor describing new projects and selling components.• William Crowther and Don Woods at Stanford Universitydeveloped the first interactive computer game involvingan adventure with monsters and other obstacles. Universityadministrators would soon complain that the game waswasting too much computer time.1977• Benoit Mandelbrot’s book on fractals in computing popularizeda mathematical phenomenon that would find usesin computer graphics, data compression, and other areas.• The Data encryption Standard (DES) was announced. Criticscharged that it was too weak and probably already compromisedby spy agencies.• Vinton Cerf demonstrated the versatility and extent ofthe Internet Protocol (IP) by sending a message around theworld via radio, land line, and satellite links.• The Charles Babbage Institute was founded. It wouldbecome an important resource for the study of computinghistory.

536 Appendix II• Bill Gates and Paul Allen found a tiny company calledMicrosoft. Its first product was a basic interpreter forthe newly emerging personal computer systems.• Radio Shack began selling its TRS-80 Model 1 personalcomputer.• The Apple II was released. It will become the most successfulof the early (pre-IBM) personal computers.1978• Diablo Systems marketed the first daisy-wheel printer.• Atari announced its Atari 400 and Atari 800 personal computers.They offered superior graphics (for the time).• Daniel Bricklin’s VisiCalc spreadsheet is announced. It willbecome the first software “hit” for the Apple II, leading businessesto consider using personal computers.• Ward Christiansen and Randy Suess developed the first softwarefor bulletin board systems (BBS).• The first West Coast Computer Faire was organized in SanFrancisco. The annual event became a showcase for innovationand a meeting forum for the first decade of personalcomputing.• The BSD (Berkeley Software Distribution) version of UNIXwas released by the group at the University of California,Berkeley, under the leadership of Bill Joy.• The awk (named for Aho, Weinberger, and Kernighan)scripting language appeared.1979• medical applications of computing were highlightedwhen Allan M. Cormack and Godfrey N. Hounsfieldreceived the Nobel Prize in medicine for the development ofcomputerized tomography (CAT), creating a revolutionaryway to examine the structure of the human body.• The Ashton-Tate company began to market dBase II, a databasemanagement system that became the leader in personalcomputer databases during the coming decade.• Intel’s new 16-bit processors, the 8086 and 8088, began todominate the market.• Hayes marketed the first modem, and the CompuServe onlineservice and early bulletin boards gave a growing numberof users something to connect to.• unix users Tom Truscott, Jim Ellis, and Steve Bellovin developeda program to exchange news in the form of files copiedbetween the Duke University and University of North Carolinacomputer systems. This gradually grew into USENET(or netnews), providing thousands of topical newsgroups.• The first networked computer fantasy game, MUD (Multi-User Dungeon), was developed.• The first COMDEX was held in Las Vegas. It would becomethe PC industry’s premier trade show.• Boston’s Computer Museum was founded. This perhaps signaledthe computing field’s consciousness of coming of age.1980• Ada, a modular descendent of Pascal, was announced. Thelanguage was part of efforts by the U.S. Defense Departmentto modernize its software development process.• RISC (reduced instruction set computer) microprocessorarchitecture was introduced.• Apple’s initial public offering of 4.6 million shares at $22per share sold out immediately. It was the largest IPO sincethat of Ford Motor Company in 1956. Apple founders, SteveJobs and Steve Wozniak, became the first multimillionairesof the microcomputer generation.• XENIX, a version of unix for personal computers, wasoffered. It met with limited success.• Shugart Associates announced a hard disk drive for personalcomputers. The disk stored a whopping 5 megabytes.1981• The ibm PC was announced. Apple “welcomed” its competitorin ads, but the IBM machine would soon surpass its competitorsas the personal computer of choice for business. Itssuccess is aided by a version of the VisiCalc spreadsheetthat sells more than 200,000 copies.• Osborne introduced the portable (sort of) computer, amachine with the size and weight of a heavy suitcase.• Apple tried to market the Apple III as a more powerful desktopcomputer for business, but the machine was plaguedwith technical problems and did not sell well.• Digital Equipment Corporation introduced its DECmatededicated word-processing system.• Xerox PARC displayed the Star, a successor to the Alto with512 kB of RAM. It was intended for use in an Ethernet network.• A network called BITNET (“Because It’s Time Network”)began to link academic institutions worldwide.• Tracy Kidder’s best-selling The Soul of a New Machinerecounted the intense Silicon Valley working culture as seenin the development of Data General’s latest workstation,the Eclipse.• Japan announced a 10-year effort to create “Fifth Generation”computing based on application of artificial intelligence.1982• Sun Microsystems was founded. It would specialize inhigh-performance workstations.• AT&T began marketing unix (System III) as a commercialproduct.• Compaq became one of the most successful makers of“clones” or ibm PC-compatible computers, introducing aportable (luggable) machine.• The AutoCad program brought CAD (computer-aideddesign and manufacturing) to the desktop.• The Time magazine “man of the year” was not a person atall—it was the personal computer!1983• Business use of personal computers continued to grow.word processing leaders WordStar and WordPerfect werejoined by the first version of Microsoft Word. Lotus 1-2-3became the new spreadsheet leader.• Borland International introduced Turbo Pascal, a speedy, easyto use programming environment for personal computers.

Appendix II 537• An industry pundit introduced the term vaporware to referto much-hyped but never-released software, such as a productcalled Ovation for ibm PCs.• IBM tried to market the PC Jr., a less-expensive PC for homeand school users. It failed to gain a foothold in the market.• More successfully, IBM offered the PC XT, the first personalcomputer that had a built-in hard drive.• Radio Shack introduced the Model 100, the first practicalnotebook computer.• Apple introduced the Lisa, a $10,000 computer with agraphical user interface. Its high price and slow performancemade it a flop, but its ideas would be more successfullyimplemented the following year in the Macintosh.• John Sculley became president of Apple Computer, beginninga bitter struggle with Apple cofounder Steve Jobs.• Richard Stallman began the GNU (GNU’s not UNIX) projectto create a version of UNIX that would not be subject toAT&T licensing.• The movie War Games portrayed teenage hackers takingcontrol of nuclear missile facilities.1984• A classic Super Bowl commercial introduced the AppleMacintosh, the computer “for the rest of us.” Based largelyon Alan Kay’s earlier work at Xerox PARC, the “Mac” usedmenus, icons, and a mouse instead of the cryptic text commandsrequired by MS-DOS.• Meanwhile, IBM introduced a more powerful personal computer,the PC/AT with the Intel 80286 chip.• Steve Jobs leaves Apple Computer to found a company calledNeXT.• Microsoft CEO Bill Gates was featured on a Time magazinecover.• The domain name system began. It allows Internet usersto connect to remote machines by name without having tospecify an exact network path.• British institutions develop JANET, the Joint AcademicNetwork.• Science fiction writer William Gibson coined the wordcyberspace in his novel Neuromancer. It began a new SFgenre called cyberpunk, featuring a harsh, violent, immersivehigh-tech world.1985• Desktop publishing was fueled by several developmentsincluding John Warnock’s PostScript page description languageand the Aldus PageMaker page layout program. TheMacintosh’s graphical interface gave it the early lead in thisapplication.• Microsoft Windows 1.0 was released, using many of thesame features as the Macintosh, although not nearly aswell.• There was increasing effort to unify the two versions ofunix (AT&T and BSD), with guidelines including the SystemV Interface Standard and POSIX.• Commodore introduces the Amiga, a machine with a sophisticatedoperating system and powerful color graphics. Themachine had many die-hard fans but ultimately could notsurvive in the marketplace.• ibm marketed the IBM 3090, a large, powerful mainframethat cost $9.3 million.• The Cray 2 supercomputer broke the 1-billion-instructions-a-secondbarrier.• A conferencing system called the Whole Earth ‘LectronicLink (WELL) was founded. Its earliest users are largelydrawn from Grateful Dead fans and assorted techies.1986• The National Science Foundation funded NSFNET, whichprovides high-speed Internet connections to link universitiesand research institutions.• Borland released a PROLOG compiler, making the artificialintelligence language accessible to PC users. A PCversion of Smalltalk also appeared from another company.• Apple beefed up the relatively anemic Macintosh with theMacintosh Plus, which has more memory.1987• Bjarne Stroustrup’s C++ language offered object-orientedprogramming in a form that was palatable to the legions ofC programmers. The language would surpass its predecessorin the coming decade.• Sun marked its first workstation based on RISC (reducedinstruction set computing) technology.• Apple sold its one millionth Macintosh. Apple also broughtout a new line of Macs (the Macintosh SE and Macintosh II)that, unlike the original Macs, were expandable by pluggingin cards.• Apple also introduced Hypercard, a simple hypertextauthoring system that became popular with educators.• ibm introduced a new line of personal computers called thePS/2. It featured a more efficient BUS called the Microchanneland some other innovations, but it sold only modestly.Most of the industry continued to further develop standardsbased upon the IBM PC AT.• The Thinking Machines Corporation’s Connection Machineintroduced massive parallel processing. It contained 64,000microprocessors that could collectively perform 2 billioninstructions per second.1988•Robert Morris Jr.’s “worm” accidentally ran out of control onthe Internet, bringing concerns about computer crimeand security to public attention. The Computer EmergencyResponse Team (CERT) was formed in response.Wolfram’s Mathematica program was a milestone in mathematicalcomputing, allowing users to not merely calculatebut also to solve symbolic equations automatically.Cray introduced the Cray Y-MP supercomputer. It couldprocess 2 billion operations per second.ibm announced a new midrange mainframe, the AS/400.Sandia National Laboratory began to build a massively parallel“hypercomputer” that would have 1,024 processorsworking in tandem.••••

538 Appendix II• A consortium called the Open Software Foundation wasestablished to promote open source shared software development.1989••The Internet now had more than 100,000 host computers.Deep Thought defeated Danish chess grandmaster BentLarsen, marking the first time a grandmaster had beendefeated by a computer.Intel announced the 80486 CPU, a chip with over a milliontransistors.Astronomer Clifford Stoll’s book The Cuckoo’s Eggrecounted his pursuit of German hackers who were seekingmilitary secrets. Stoll soon became a well-known critic ofcomputer technology and the Internet.The ARPANET officially ends, having been succeeded by theNSFNET.•••1990• Microsoft Windows became truly successful with version3.0, diminishing the user interface advantages of the Macintosh.• At Sun Microsystems, James Gosling developed the Oak languageto control embedded systems. After the original projectwas canceled, Gosling redesigned the language as Java.• ibm announced the System/390 mainframe.• ibm and Microsoft developed OS/2, an operating systemintended to replace MS-dos. Microsoft withdrew in favor ofWindows, and despite considerable technical merits, OS/2never really takes hold.• Secret Service agents raided computer systems and bulletinboards, seeking evidence of illegal copying of a BellSouthmanual, disrupting an innocent game company. In response,Mitch Kapor founded the Electronic Frontier Foundationto advocate for civil liberties of computer users. Anothergroup, the Computer Professionals for Social Responsibility,filed a Freedom of Information Act (FOIA) request for FBIrecords involving alleged government surveillance of bulletinboard systems.1991• The Science Museum in London exhibited a reconstructionof Charles Babbage’s never-built difference engine.• A Finnish student named Linus Torvalds found that hecouldn’t afford a unix license, so he wrote his own unixkernel and combined it with GNU utilities. The resultwould eventually become the popular Linux operatingsystem.• Developers at the University of Minnesota created Gopher,a system for providing documents over the Internet usinglinked menus. However, it was soon to be surpassed by theWorld Wide Web, created by Tim Berners-Lee at theCERN physics laboratory in Geneva, Switzerland.• Advanced Micro Devices began to compete with Intel bymaking IBM PC-compatible CPU chips.• Apple and ibm signed a joint agreement to develop technologyin areas that include object-oriented operating sys-tems, multimedia, and interoperability between Macintoshand IBM networks.1992• Reports of the Michelangelo computer virus frightenedcomputer users. Although the virus did little damage, itspurred more users to practice “safe computing” and installantivirus software.• Motorola announced the Power PC, a 32-bit RISC microprocessorthat contains 28 million transistors.• An estimated 1 million host computers were on the Internet.The Internet Society is founded to serve as a coordinatorof future development of the network.1993• Apple’s Newton handheld computer created a new categoryof machine called the pda, or personal digital assistant.• Microsoft Windows NT was announced. It is a version ofthe operating system designed especially for network servers.• Steve Jobs announced that his NeXT company wouldabandon its hardware efforts and concentrate on marketingits innovative operating system and developmentsoftware.• Leonard Adleman demonstrated molecular computing byusing DNA molecules to solve the Traveling Salesman problem.• The Cray 3 supercomputer continued the evolution of thatline. It could be scaled up to a 16-processor system.• The Mosaic graphical Web browser popularized the WorldWide Web.• The Clinton administration announced plans to develop anational “Information Superhighway” based on the Internet.Volunteer “Net Day” programs would begin to connectschools to the network.• The White House established its Web site, www.whitehouse.gov.1994•Mosaic’s developer, Marc Andreessen, left NCSA and joinedJim Clark to found Netscape. Netscape soon released animproved browser called Netscape Navigator.Apple announced that it would license the Mac operatingsystem to other companies to make Macintosh “clones.”Few companies would take them up on it, and Apple wouldsoon withdraw the licensing offer.Intel Corporation was forced to recall millions of dollarsworth of its new Pentium chips when a mathematical flawwas discovered in the floating-point routines.Marc Andreessen and Jim Clark founded Netscape anddeveloped a new Web browser, Netscape Navigator. Itwould become the leading Web browser for several years.Red Hat released a commercial distribution of Linux 1.0.Search engines such as Lycos and Alta Vista started helpingusers find Web pages. Meanwhile, a graduate studentnamed Jerry Yang started compiling an online list of his•••••

Appendix II 539favorite Web sites. That list would eventually becomeYahoo!• Advertising in the form of banner ads began to appear onWeb sites.1995•Microsoft Windows 95 gave a new look to the operatingsystem and provided better support for devices, includingplug and play device configuration.Microsoft began its own on-line service, the MicrosoftNetwork (MSN). Despite its startup icon being placed onthe Windows 95 desktop, the network would trail industryleader America Online, which had overtaken CompuServeand Prodigy.Jeff Bezos’s online bookstore, Amazon.com, opened for business.It would become the largest e-commerce retailer.The major online services began major promotion of accessto the World Wide Web.NSFNET retired from direct operation of the Internet,which had now been fully privatized. The agency thenfocused on providing new broadband connections betweensupercomputer sites.Sun announced the Java language. It would become one ofthe most popular languages for developing applications forthe World Wide Web.Motorola announced the Power PC-602, a 64-bit cpu chip.Compaq ranked first in personal computer sales in theUnited States, followed by Apple.Physicists Peter Fromherz and Alfred Stett of the MaxPlanck Institute of Biochemistry in Munich, Germany, demonstratedthe direct stimulation of a specific nerve cell ina leech by a computer probe. This conjured visions of the“jacked-in” neural implants foreseen by science fiction writerssuch as William Gibson.The next generation of Cray supercomputers, the T90series, could be scaled up to a rate of 60 billion instructionsper second.streaming (real-time video and audio) began to becomepopular on the Web.Computer-generated imagery (CGI) was featured by Hollywoodin the movie Toy Story.•••••••••••1996• A product called Web TV attempted to bring the WorldWide Web to home consumers without the complexity offull-fledged computers. The product achieved only modestsuccess as the price of personal computers continued todecline.• The U.S. Postal Service issued a stamp honoring the 50thanniversary of ENIAC.• The Boston Computer Society, one of the oldest computeruser groups, disbanded.• World chess champion Garry Kasparov won his first matchagainst IBM’s Deep Blue chess computer, but said the matchhad been unexpectedly tough.• Yahoo! offered its stock to the public, running up the second-highestfirst-day gain in NASDAQ history.• Seymour Cray’s Cray Research (a developer of supercomputers)was acquired by Silicon Graphics.• Pierre Omidyar turned a small hobby auction site into eBayand was soon attracting thousands of eager sellers and buyersto the site.• In one of its infrequent ventures into hardware, Microsoftannounced the NetPC, a stripped-down diskless PC thatwould run software from a network. Such “network computers”never really caught on, being overtaken by the everdecliningprice for complete PCs.1997•The chess world was shocked when world champion GarryKasparov was defeated in a rematch with Deep Blue.A single Internet domain name, business.com, was sold for$150,000.Amazon.com had a successful initial public offering (IPO).A technology called “push” began to be hyped. It involvedWeb sites continually feeding “channels” of news or entertainmentto user’s desktops. However, the idea would fail tomake much headway.Internet users banded together to demonstrate distributedcomputing by cracking a 56-bit DES cipher in 140days.The Association for Computing Machinery (ACM) celebratedits 50th anniversary.•••••1998• Microsoft Windows 98 provided an incremental improvementin the operating system.• Apple announced the iMac, a stylish machine that rejuvenatedthe Macintosh line.• eBay’s IPO was wildly successful, making Pierre Omidyar,Meg Whitman, and other eBay executives instant millionaires.• Merger-mania hit the online service industry, with AmericaOnline buying CompuServe’s online service (spinning offthe network facilities to WorldCom). AOL then acquiredNetscape and its Web hosting technology.• In another significant merger, Compaq acquired DigitalEquipment Corporation (DEC).1999•••Federal Judge Thomas Penfield Jackson found that Microsoftviolated antitrust laws. The case dragged on withappeals, with the process of crafting a remedy (such aspossibly the split-up of the company) still unresolved in2002.Another virus, Melissa, panicked computer users.Some companies began to offer “free” computers to peoplewho agreed to sign up for long-term, relatively expensiveInternet service.Computer scientists and industry pundits debated the possibilityof widespread computer disasters due to the y2k problem.Companies spent millions of dollars trying to find andfix old computer code that used only two digits to store yeardates.•

540 Appendix II• Apple released os x, a new unix-based operating systemfor the Macintosh.2000• New Year’s Day found the world to be continuing much asbefore, with only a few scattered y2k problems.• Unknown hackers, however, brought down some commercialWeb sites with denial-of-service (DOS) attacks.• AOL merged with Time-Warner, creating the world’s largestmedia company. Critics worried about the affects ofgrowing corporate concentration on the diversity of theInternet.• Microsoft Windows 2000 began the process of mergingthe consumer Windows and Windows NT lines into a singlefamily of operating systems that would no longer use any ofthe underlying ms-dos code.• The World Wide Web was estimated to have about 1 billionpages online.• Tech stocks (and particularly e-commerce companies)began to sharply decline as investors became increasinglyskeptical about profitability.• A growing number of Web users were beginning to switchto much faster broadband connections using dsl or cablemodems.2001• The decline in e-commerce stocks continued, with tens ofthousands of jobs lost. One of the many failures was Webvan,the Internet grocery service. Amazon.com sufferedlosses but continued trying to expand into profitable niches.Only eBay among the major e-commerce companies continuedto be profitable.• Microsoft Windows XP offered consumer and “professional”versions of Windows on the same code base.• ibm researchers created a seven “qubit” quantum computerto execute Shor’s algorithm, a radical approach to factoringthat could potentially revolutionize cryptography.• Among the specters raised in the wake of the September 11terrorist attacks was cyberterrorism having the potentialto disrupt vital infrastructure, services, and the economy.biometrics and more sophisticated database techniqueswere enlisted in the war on terrorism while civil libertiesgroups voiced concerns.2002• Wireless networking using the faster 802.11 standardbecame increasingly popular as an alternative to cabled orphone line networks for homes and small offices.• Consumer digital cameras began to approach “professional”quality.• The U.S. Supreme Court ruled that “virtual” child pornography(in which no actual children were used) was protectedby the First Amendment.• Continuing stock market declines threaten growth in thecomputer and Internet sectors.• The music-sharing service Napster goes out of business,when it is forced to stop distributing copyrighted music.2003• The U.S. economy begins to recover, including the technologysector. However, there is a growing concern aboutjobs being “outsourced” to countries such as India andChina.• Weblogs, or blogs, are an increasingly popular form ofonline expression. Some journalists even use them to“break” major stories.• The Recording Industry Association of America (RIAA) fileshundreds of lawsuits against individual users of music filesharingsystems.• Apple and AMD introduce the first 64-bit microprocessorsin the personal computer market.2004• Security remains an urgent concern as viruses and wormsflood the Internet in vast numbers.• spam also floods users’ e-mail boxes. phishing messagestrick users into revealing credit card numbers and othersensitive information.• Apple’s iPod dominates the portable media player market,while its iTunes store sells over 100 million songs.• Bloggers become a political force, winning access to majorparty conventions.• Enthusiastic response to Google’s initial public stock offeringsignals that investors may have regained confidence inthe strength of the Internet sector.2005• “Web 2.0” becomes a buzzword with Web services beingdesigned to be leveraged into new applications to be deliveredto users’ browsers.• Sony’s flawed CD copy protection leaves users vulnerable tohackers; consumers increasingly demand an end to restrictionson use of media they buy.• Concerns about the security of new electronic votingsystems grow.2006• Apple begins selling Intel-based Macs; meanwhile mostPCs now have dual processors.• Google buys the phenomenally successful video site You-Tube for $1.65 billion.• Microsoft releases its delayed Windows Vista operatingsystem, but response is lukewarm.• New versions of Linux such as Ubuntu attract enthusiasts,but are slow in making inroads on the desktop.2007• social networking sites such as MySpace and FaceBookare used by millions of students, but raise concerns aboutprivacy and bullying.• Wikipedia now has more than 9 million articles in 252 languages.• CNN and YouTube join to sponsor presidential politicaldebates, and candidates respond to questions posed in videossubmitted by the public.

Appendix II 541• Google and other free Web-based applications offer newalternatives for office software.• Apple introduces the iPhone and new iPods with innovativeuser interfaces.• Albert Fert and Peter Grunberg receive the Nobel Prize inphysics for their development of “giant magnetoresistance,”a phenomenon that enables disk drives to read fainter, moredensely packed magnetic signals. The result is shrinkingdisks and/or greater storage capacity.2008• A record amount of money is raised online during the presidentialelection campaign.• Microsoft engages in a protracted campaign to acquireonline rival Yahoo!• Providers and advocacy groups struggle over net neutrality(equal treatment of online applications and content).

Appendix IIISome Significant AwardsThis appendix describes some of the major awards in computerscience and technology and lists recipients as of 2001.The last names of persons with entries in this book aregiven in small capital letters.Association for ComputingMachinery (ACM)ACM Turing AwardThe ACM Turing Award “is given to an individual selectedfor contributions of a technical nature made to the computingcommunity. The contributions should be of lasting andmajor technical importance to the computer field.”Annual Recipients(A few years have joint recipients.)1966 A. J. Perlis: “For his influence in the area of advancedprogramming techniques and compiler construction.”1967 Maurice V. Wilkes: “Professor Wilkes is best known asthe builder and designer of the EDSAC, the first computer withan internally stored program. Built in 1949, the EDSAC useda mercury delay line memory. He is also known as the author,with Wheeler and Gill, of a volume on ‘Preparation of Programsfor Electronic Digital Computers’ in 1951, in which programlibraries were effectively introduced.”1968 Richard Hamming: “For his work on numerical methods,automatic coding systems, and error-detecting and errorcorrectingcodes.”1969 Marvin Minsky [Citation not listed by ACM. However,Minsky was a key pioneer in artificial intelligence research,including neural networks, robotics, and cognitive psychology.]1970 J. H. Wilkinson: “For his research in numerical analysisto facilitate the use of the high-speed digital computer, havingreceived special recognition for his work in computations in linearalgebra and ‘backward’ error analysis.”1971 John McCarthy: “Dr. McCarthy’s lecture ‘The PresentState of Research on Artificial Intelligence’ is a topic that coversthe area in which he has achieved considerable recognition forhis work.”1972 E. W. Dijkstra.: “Edsger Dijkstra was a principal contributorin the late 1950s to the development of the ALGOL, ahigh-level programming language which has become a model ofclarity and mathematical rigor. He is one of the principal exponentsof the science and art of programming languages in general,and has greatly contributed to our understanding of theirstructure, representation, and implementation. His fifteen yearsof publications extend from theoretical articles on graph theoryto basic manuals, expository texts, and philosophical contemplationsin the field of programming languages.”1973 Charles W. Bachman: “For his outstanding contributionsto database technology.”1974 Donald E. Knuth: “For his major contributions to theanalysis of algorithms and the design of programming languages,and in particular for his contributions to the ‘art ofcomputer programming’ through his well-known books in acontinuous series by this title.”1975 Alan Newell and Herbert A. Simon: “In joint scientificefforts extending over twenty years, initially in collaborationwith J. C. Shaw at the RAND Corporation, and subsequentiallywith numerous faculty and student colleagues at Carnegie-MellonUniversity, they have made basic contributions to artificialintelligence, the psychology of human cognition, and list processing.”1976 Michael O. Rabin and Dana S. Scott: “For their jointpaper ‘Finite Automata and Their Decision Problem,’ whichintroduced the idea of nondeterministic machines, which hasproved to be an enormously valuable concept. Their [Scott &Rabin] classic paper has been a continuous source of inspirationfor subsequent work in this field.”542

Appendix III 5431977 John Backus: “For profound, influential, and lastingcontributions to the design of practical high-level programmingsystems, notably through his work on FORTRAN, and for seminalpublication of formal procedures for the specification of programminglanguages.”1978 Robert W. Floyd: “For having a clear influence on methodologiesfor the creation of efficient and reliable software,and for helping to found the following important subfields ofcomputer science: the theory of parsing, the semantics of programminglanguages, automatic program verification, automaticprogram synthesis, and analysis of algorithms.”1979 Kenneth E. Iverson: “For his pioneering effort in programminglanguages and mathematical notation resulting in whatthe computing field now knows as APL, for his contributions tothe implementation of interactive systems, to educational uses ofAPL, and to programming language theory and practice.”1980 C. Anthony R. Hoare: “For his fundamental contributionsto the definition and design of programming languages.”1981 Edgar F. Codd: “For his fundamental and continuingcontributions to the theory and practice of database managementsystems. He originated the relational approach to databasemanagement in a series of research papers published commencingin 1970. His paper ‘A Relational Model of Data forLarge Shared Data Banks’ was a seminal paper, in a continuingand carefully developed series of papers. Dr. Codd built uponthis space and in doing so has provided the impetus for widespreadresearch into numerous related areas, including databaselanguages, query subsystems, database semantics, locking andrecovery, and inferential subsystems.”1982 Stephen A. Cook: “For his advancement of our understandingof the complexity of computation in a significant andprofound way. His seminal paper, ‘The Complexity of TheoremProving Procedures,’ presented at the 1971 ACM SIGACT Symposiumon the Theory of Computing, laid the foundations forthe theory of NP-Completeness. The ensuing exploration of theboundaries and nature of NP-complete class of problems hasbeen one of the most active and important research activities incomputer science for the last decade.”1983 Ken Thompson and Dennis Ritchie: “For their developmentof generic operating systems theory and specifically forthe implementation of the UNIX operating system.”1984 Niklaus Wirth: “For developing a sequence of innovativecomputer languages, EULER, ALGOL-W, MODULA andPASCAL. PASCAL has become pedagogically significant and hasprovided a foundation for future computer language, systems,and architectural research.”1985 Richard M. Karp: “For his continuing contributions tothe theory of algorithms including the development of efficientalgorithms for network flow and other combinatorial optimizationproblems, the identification of polynomial-time computabilitywith the intuitive notion of algorithmic efficiency, and,most notably, contributions to the theory of NP-completeness.Karp introduced the now standard methodology for provingproblems to be NP-complete which has led to the identificationof many theoretical and practical problems as being computationallydifficult.”1986 John Hopcroft and Robert Tarjan: “For fundamentalachievements in the design and analysis of algorithms and datastructures.”1987 John Cocke: “For significant contributions in the designand theory of compilers, the architecture of large systems andthe development of reduced instruction set computers (RISC);for discovering and systematizing many fundamental transformationsnow used in optimizing compilers including reductionof operator strength, elimination of common subexpressions,register allocation, constant propagation, and dead code elimination.”1988 Ivan Sutherland: “For his pioneering and visionary contributionsto computer graphics, starting with Sketchpad, andcontinuing after. Sketchpad, though written twenty-five yearsago, introduced many techniques still important today. Theseinclude a display file for screen refresh, a recursively traversedhierarchical structure for modeling graphical objects, recursivemethods for geometric transformations, and an object orientedprogramming style. Later innovations include a ‘Lorgnette’ forviewing stereo or colored images, and elegant algorithms forregistering digitized views, clipping polygons, and representingsurfaces with hidden lines.”1989 William (Velvel) Kahan: “For his fundamental contributionsto numerical analysis. One of the foremost experts onfloating-point computations. Kahan has dedicated himself to‘making the world safe for numerical computations.’ ”1990 Fernando J. Corbato: “For his pioneering work organizingthe concepts and leading the development of the general-purpose,large-scale, time-sharing and resource-sharingcomputer systems, CTSS and Multics.”1991 Robin Milner: “For three distinct and complete achievements:1) LCF, the mechanization of Scott’s Logic of ComputableFunctions, probably the first theoretically based yet practicaltool for machine assisted proof construction; 2) ML, the firstlanguage to include polymorphic type inference together witha type-safe exception-handling mechanism; 3) CCS, a generaltheory of concurrency. In addition, he formulated and stronglyadvanced full abstraction, the study of the relationship betweenoperational and denotational semantics.”1992 Butler W. Lampson: “For contributions to the developmentof distributed, personal computing environments and thetechnology for their implementation: workstations, networks,operating systems, programming systems, displays, security anddocument publishing.”

544 Appendix III1993 Juris Harmanis and Richard E. Stearns: “In recognitionof their seminal paper which established the foundations for thefield of computational complexity theory.”1994 Edward Feigenbaum and Raj Reddy: “For pioneeringthe design and construction of large-scale artificial intelligencesystems, demonstrating the practical importance and potentialcommercial impact of artificial intelligence technology.”1995 Manuel Blum: “In recognition of his contributions to thefoundations of computational complexity theory and its applicationto cryptography and program checking.”1996 Amir Pneueli: “For seminal work introducing temporallogic into computing science and for outstanding contributionsto program and systems verification.”1997 Douglas Engelbart: “For an inspiring vision of thefuture of interactive computing and the invention of key technologiesto help realize this vision.”1998 James Gray: “For seminal contributions to database andtransaction processing research and technical leadership in systemimplementation.”1999 Frederick P. Brooks, Jr.: “For landmark contributionsto computer architecture, operating systems, and softwareengineering.”2000 Andrew Chi-Chih Yao: “In recognition of his fundamentalcontributions to the theory of computation, including thecomplexity-based theory of pseudorandom number generation,cryptography, and communication complexity.”2001 Ole-Johan Dahl and Kristen Nygaard: “For ideas fundamentalto the emergence of object oriented programming,through their design of the programming languages Simula Iand Simula 67.”2002 Ronald L. Rivest, Adi Shamir, and Leonard M. Adelman:“For their ingenious contribution for making public-key cryptographyuseful in practice.”2003 Alan Kay: “pioneering many of the ideas at the root ofcontemporary object-oriented programming languages, leadingthe team that developed Smalltalk, and for fundamental contributionsto personal computing.”2004 Vinton G. Cerf and Robert E. Kahn: “For pioneeringwork on internetworking, including the design and implementationof the Internet’s basic communications protocols, TCP/IP,and for inspired leadership in networking.”2005 Peter Naur: “For fundamental contributions to programminglanguage design and the definition of Algol 60, to compilerdesign, and to the art and practice of computer programming.”2006 Frances E. Allen: “For contributions that fundamentallyimproved the performance of computer programs in solving problems,and accelerated the use of high-performance computing.”2007 Edmund M. Clarke, E. Allen Emerson, and Joseph Sifakis:“For . . . developing ModelChecking into a highly effectiveverification technology, widely adopted in the hardware andsoftware industries.”Eckert-Mauchly AwardAdministered jointly by ACM and IEEE Computer Societyand “given for contributions to computer and digital systemsarchitecture where the field of computer architectureis considered at present to encompass the combined hardware-softwaredesign and analysis of computing and digitalsystems.”Annual Recipients1979 Robert S. Barton: “For his outstanding contributionsin basing the design of computing systems on the hierarchicalnature of programs and their data.”1980 Maurice V. Wilkes: “For major contributions to computerarchitecture over three decades including notable achievementsin developing a working stored-program computer,formulation of the basic principles of microprogramming, earlyresearch on cache memories, and recent studies in distributedcomputation.”1981 Wesley A. Clark: “For contributions to the early developmentof the minicomputer and the multiprocessor, and forcontinued contributions over 25 years that have found theirway into computer networks, modular computers, and personalcomputers.”1982 C. Gordon Bell: “For his contributions to designing andunderstanding computer systems: for his contributions in theformation of the minicomputer; for the creation of the first commercial,interactive timesharing computer; for pioneering workin the field of hardware description languages; for co-authoringclassic computer books and co-founding a computer museum.”1983 Tom Kilburn: “For major seminal contributions tocomputer architecture spanning a period of three decades. Forestablishing a tradition of collaboration between university andindustry which demands the mutual understanding of electronicstechnology and abstract programming concepts.”1984 Jack B. Dennis: “For contributions to the advancementof combined hardware and software design through innovationsin data flow architectures.”1985 John Cocke: “For contributions to high performancecomputer architecture through lookahead, parallelism and pipelineutilization, and to reduced instruction set computer architecturethrough the exploitation of hardware-software tradeoffsand compiler optimization.”1986 Harvey G. Cragon: “For major contributions to computerarchitecture and for pioneering the application of integrated circuitsfor computer purposes. For serving as architect of the Texas

Appendix III 545Instruments scientific computer and for playing a leading role inmany other computing developments in that company.”1987 Gene M. Amdahl: “For outstanding innovations in computerarchitecture, including pipelining, instruction look-ahead,and cache memory.”1988 Daniel P. Siewiorek: “For outstanding contributions inparallel computer architecture, reliability, and computer architectureeducation.”1989 Seymour Cray: “For a career of achievements that haveadvanced supercomputing design.”1990 Kenneth E. Batcher: “For contributions to parallel computerarchitecture, both for pioneering theories in interconnectionnetworks and for the pioneering implementations ofparallel computers.”1991 Burton J. Smith: “For pioneering work in the design andimplementation of scalable shared memory multiprocessors.”1992 Michael J. Flynn: “For his important and seminal contributionsto processor organization and classification, computerarithmetic and performance evaluation.”1993 David Kuck: “For his impact on the field of supercomputing,including his work in shared memory multiprocessing,clustered memory hierarchies, compiler technology, and application/librarytuning.”1994 James E. Thornton: “For his pioneering work on highperformanceprocessors; for inventing the ‘scoreboard’ forinstruction issue; and for fundamental contributions to vectorsupercomputing.”1995 John Crawford: “In recognition of your impact on thecomputer industry through your development of microprocessortechnology.”1996 Yale N. Patt: “For important contributions to instructionlevel parallelism and superscalar processor design.”1997 Robert Tomasulo: “For the ingenious Tomasulo’s algorithm,which enabled out-of-order execution processors to beimplemented.”1998 T. Watanabe: [Citation not available, but NEC notes thatWatanabe “was a chief architect for NEC’s first supercomputer,the SX-2, and is recognized for his significant contributions tothe architectural design of supercomputers having multiple, parallelvector pipelines and programmable vector caches.”]1999 James E. Smith: “For fundamental contributions to highperformancemicroarchitecture, including saturating countersfor branch prediction, reorder buffers for precise exceptions,decoupled access/execute architectures, and vector supercomputerorganization, memory, and interconnects.”2000 Edward Davidson: “For his seminal contributions to thedesign, implementation, and performance evaluation of highperformancepipelines and multiprocessor systems.”2001 John Hennessy: “For being the founder and chief architectof the MIPS Computer Systems and contributing to thedevelopment of the landmark MIPS R2000 microprocessor.”2002 B. Ramakrishna (Bob) Rau: “For pioneering contributionsto statistically scheduled instruction-level parallel processorsand their compilers.”2003 Joseph A. (Josh) Fisher: “In recognition of 25 years ofseminal contributions to instruction-level parallelism, pioneeringwork on VLIW architectures, and the formulation of theTrace Scheduling compilation technique.”2004 Frederick P. Brooks: “For the definition of computerarchitecture and contributions to the concept of computer familiesand to the principles of instruction set design; for seminalcontributions in instruction sequencing, including interruptsystems and execute instructions; and for contributions to theIBM 360 instruction set architecture.”2005 Robert P. Colwell: “For outstanding achievements in thedesign and implementation of industry-changing microarchitectures,and for significant contributions to the RISC/CISC architecturedebate.”2006 James H. Pomerene: “For pioneering innovations in computerarchitecture, including early concepts in cache, reliablememories, pipelining and branch prediction, for the design of theIAS computer and for the design of the Harvest supercomputer.”2007 Mateo Valero: “For extraordinary leadership in buildinga world class computer architecture research center, for seminalcontributions in the areas of vector computing and multithreading,and for pioneering basic new approaches to instructionlevelparallelism.”2008 David Patterson: “For seminal contributions to RISCmicroprocessor architectures, RAID storage systems design, andreliable computing, and for leadership in education and in disseminatingacademic research results into successful industrialproducts.”Grace Murray Hopper AwardThe ACM gives this award for “the outstanding young computerprofessional of the year . . . selected on the basis of asingle recent major technical or service contribution.”Annual RecipientsNote: this award has not been given every year.1971 Donald E. Knuth: “For the publication in 1968 (at age30) of Volume I of his monumental treatise ‘The Art of ComputerProgramming.’ ”

546 Appendix III1972 Paul E. Dirksen and Paul H. Kress: “For the creation ofWATFOR Compiler, the first member of a powerful new familyof diagnostic and educational programming tools.”1973 Lawrence M. Breed, Richard Lathwell, and Roger Moore:“For their work in the design and implementation of APL/360,setting new standards in simplicity, efficiency, reliability andresponse time for interactive systems.”1974 George N. Baird: “For his successful development andimplementation of the Navy’s COBOL Compiler ValidationSystem.”1975 Allen L. Scherr: “For his pioneering study in quantitativecomputer performance analysis.”1976 Edward H. Shortliffe: “For his pioneering research whichis embodied in the MYCIN program. MYCIN is a program whichconsults with physicians about the diagnosis and treatment ofinfections. In creating MYCIN, Shortliffe employed his backgroundof medicine, together with his research in knowledgebasedsystems design, to produce an integrated package whichis easy for expert physicians to use and extend. Shortliffe’s workformed the basis for a research program supported by NIH, andhas been widely studied and drawn upon by others in the fieldof knowledge-based systems.”1978 Raymond C. Kurzweil: “For his development of aunique reading machine for the blind, a computer-based devicethat reads printed pages aloud. The Kurzweil machine is an 80-pound device that shoots a beam of light across each printedpage, converts the reflected light across each printed page, convertsthe reflected light into digital data that is analyzed by itsbuilt-in computer, and then transformed into synthetic speech.It is expected to make reading of all printed material possiblefor blind people, whose reading was previously limited to materialtranslated into Braille. The machine would not have beenpossible without another achievement by Kurzweil, that is, aset of rules embodied in the mini-computer program by whichprinted characters of a wide variety of sizes and shapes are reliablyand automatically recognized.”1979 Steven Wozniak: “For his many contributions to therapidly growing field of personal computing and, in particular,to the hardware and software for the Apple Computer.”1980 Robert M. Metcalfe: “For his work in the developmentof local networks, specifically the Ethernet.”1981 Daniel S. Bricklin: “For his contributions to personalcomputing and, in particular, to the design of VisCalc. Bricklin’sefforts in the development of the ‘Visual Calculator’ provide theexcellence and elegance that ACM seeks to sustain through suchactivities as the Awards program.”1982 Brian K. Reid: “For his contributions in the area of computerizedtext-production and typesetting systems, specificallyScribe which represents a major advance in this area. It embodiesseveral innovations based on computer science research inprogramming language design, knowledge-based systems, computerdocument processing, and typography. The impact ofScribe has been substantial due to the excellent documentationand Reid’s efforts to spread the system.”1984 Daniel H. H. Ingalls, Jr.: “For his work at the Xerox PaloAlto Research Center, where he was a major force, both technicaland inspirational, in the development of the SMALLTALKlanguage and its graphics facilities. He is the designer of theBITBLT primitive that is now widely used for generating imageson raster-scan displays. The combination of a good idea, a gooddesign, and very effective and careful implementation has ledto BITBLT’s wide acceptance in the computing community. Mr.Ingalls’ research has also directly and dramatically affected thecomputing industry’s view of what people should have in theway of accessible computing.”1985 Cordell Green: “For establishing several key aspects ofthe theoretical basis for logic programming and providing a resolutiontheorem prover to carry out a programming task by constructingthe result which the computer program is to compute.For proving the constructive technique correct and for presentingan effective method for constructing the answer; these contributionsproviding an early theoretical basis for Prolog andlogic programming.”1986 William N. Joy: “For his work on the Berkeley UNIXOperating System as a designer, integrator, and implementor ofmany of its advanced features including Virtual Memory, the C-shell, the vi Screen editor, and Networking.”1987 John K. Ousterhout: “For his contribution to very largescale integrated circuit computer aided design. His systems,Caesar and Magic, have demonstrated that effective CAD systemsneed not be expensive, hard to learn, or slow.”1988 Guy L. Steele: “For his general contributions to thedevelopment of Higher Order Symbolic Programming, principallyfor his advancement of lexical scoping in LISP.”1989 W. Daniel Hillis: “For his basic research on data parallelalgorithms and for the conception, design, implementation andcommercialization of the Connection Machine.”1990 Richard Stallman: “For pioneering work in the developmentof the extensible editor EMACS (Editing Macros).”1991 Feng-hsuing Hsu: “For contributions in architecture andalgorithms for chess machines. His work led to the creation ofthe Deep Thought Chess Machine, which led to the first chessplaying computer to defeat Grandmasters in tournament playand the first to achieve a certified Grandmaster level rating.”1993 Bjarne Stroustrup: “For his early work laying the foundationsfor the C++ programming language. Based on the foundationsand Dr. Stroustrup’s continuing efforts, C++ has becomeone of the most influential programming languages in the historyof computing.”

Appendix III 5471996 Shafrira Goldwasser: “For her early work relating computation,randomness, knowledge committee and proofs, whichhas shaped the foundations of probabilistic computation theory,computational number theory, and cryptography. This work is acontinuing influence in design and certification of secure communicationsprotocols, with practical applications to developmentof secure networks and computer systems.”1999 Wen-mei Hwu: “For the design and implementationof the IMPACT compiler infrastructure which has been usedextensively both by the microprocessor industry as a baselinefor product development and by academia as a basis foradvanced research and development in computer architectureand compiler design.”2000 Lydia Kavraki: “For her seminal work on the probabilisticroadmap approach which has caused a paradigm shiftin the area of path planning, and has many applications inrobotics, manufacturing, nanotechnology and computationalbiology.”2001 George Necula: “For his seminal work on the conceptand implementation of Proof Carrying Code, which has had agreat impact on the field of programming languages and compilersand has given a new direction to applications of theoremproving to program correctness, such as safety of mobile codeand component-based software.”2002 Ramakrishnan Srikant: “For his seminal work on miningassociation rules, which has led to association rules becoming akey data mining tool as well as part of the core syllabus in databaseand data mining courses.”2003 Stephen W. Keckler: “For ground-breaking analysis oftechnology scaling for high-performance processors that shedsnew light on the methods required to maintain performanceimprovement trends in computer architecture, and on the designimplications for future high-performance processors and systems.”2004 Jennifer Rexford: “For models, algorithms, and deployedsystems that assure stable and efficient Internet routing withoutglobal coordination.”2005 Omer Reingolf: “For his work in finding a deterministiclogarithmic-space algorithm for ST-connectivity in undirectedgraphs.”2006 Daniel Klein: “For the design of a system capable oflearning a high-quality grammar for English directly from text.”2007 Vern Paxson: “For his work in measuring and characterizingthe Internet.”Electronic FrontierFoundation (EFF)Pioneer AwardsThe EFF gives annual “Pioneer Awards” to leaders in“expanding knowledge, freedom, efficiency, and utility.”1992 Douglas C. Engelbart, Robert Kahn, Jim Warren, TomJennings, and Andrzej Smereczynski.1993 Paul Baran, Vinton Cerf, Ward Christensen, DaveHughes, and the USENET software developers, represented bythe software’s originators Tom Truscott and Jim Ellis.1994 Ivan Sutherland, Whitfield Diffie and Martin Hellman,Murray Turoff and Starr Roxanne Hiltz, Lee Felsenstein, BillAtkinson, and the Well.1995 Philip Zimmermann, Anita Borg, and Willis Ware.1996 Robert Metcalfe, Peter Neumann, Shabbir Safdar, andMatthew Blaze.1997 Marc Rotenberg, Johan “Julf” Helsingius, and (specialhonorees) Hedy Lamarr and George Antheil.1998 Richard Stallman, Linus Torvalds, and BarbaraSimons.1999 Jon Postel, Drazen Panic, and Simon Davies.2000 Tim Berners-Lee, Phil Agre, and “Librarians Everywhere.”2001 Seth Finkelstein, Stephanie Perrin, and Bruce Ennis.2002 Dan Gillmour, Beth Givens, Jon Johansen, and “writersof DeCSS.”2003 Amy Goodman, Eben Moglen, and David Sobel.2004 Kim Alexander, David Dill, and Arviel Rubin.2005 Patrick Ball, Edward Felten, and Mitch Kapor.2006 Craigslist, Gigi Sohn, and Jimmy Wales.2007 Yochai Benkler, Cory Doctorow, and Bruce Scheier.2008 Mozilla Foundation, Mitchell Baker, Michael Geist, andMark Klein.IEEE Computer SocietyComputer Pioneer AwardThe IEEE Computer Society presents the Computer PioneerAward “for significant contributions to concepts and developmentsin the electronic computer field which have clearlyadvanced the state of the art in computing.” The award isgiven a minimum of 15 years after the achievement beingawarded.Charter RecipientsHoward H. AikenSamuel N. AlexanderGene M. Amdahl

548 Appendix IIIJohn W. BackusRobert S. BartonC. Gordon BellFrederick P. Brooks, Jr.Wesley A. ClarkFernando J. CorbatoSeymour R. CrayEdsgar W. DijkstraJ. Presper EckertJay W. ForresterHerman H. GoldstineRichard W. HammingGrace M. HopperAlston S. HouseholderDavid A. HuffmanKenneth E. IversonTom KilburnDonald E. KnuthHerman LukoffJohn W. MauchlyGordon E. MooreAllen NewellRobert N. NoyceLawrence G. RobertsGeorge R. StibitzShmuel WinogradMaurice V. WilkesKonrad ZuseAnnual Recipients(With year and achievement as cited by the ComputerSociety.)1981 Jeffrey Chuan Chu: “For his early work in electroniccomputer logic design”1982 Harry D. Huskey: “For the first parallel computerSWAC”1982 Arthur Burks: “For his early work in electronic computerlogic design”1984 John Vincent Atanasoff: “For the first electronic computerwith serial memory”1984 Jerrier A. Haddad: “For his part in the lead IBM 701design team”1984 Nicholas C. Metropolis: “For the first solved atomicenergy problems on ENIAC”1984 Nathaniel Rochester: “For the architecture of IBM 702electronic data processing machines”1984 Willem L. van der Poel: “For the serial computerZEBRA”1985 John G. Kemeny: “For BASIC”1985 John McCarthy: “For LISP and artificial intelligence”1985 Alan Perlis: “For computer language translation”1985 Ivan Sutherland: “For the graphics SKETCHPAD”1985 David J. Wheeler: “For assembly language programming”1985 Heniz Zemanek: “For computer and computer languages—MAILUEFTERL”1986 Cuthbert C. Hurd: “For contributions to early computing”1986 Peter Naur: “For computer language development”1986 James H. Pomerene: “For IAS and Harvest computers”1986 Adriann van Wijngaarden: “For ALGOL 68”1987 Robert E. Everett: “For Whirlwind”1987 Reynold B. Johnson: “For RAMAC”1987 Arthur L. Samuel: “For Adaptive non-numeric processing”1987 Nicklaus E. Wirth: “For PASCAL”1988 Freidrich L. Bauer: “For computer stacks”1988 Marcian E. Hoff, Jr.: “For microprocessor on a chip”1989 John Cocke: “For instruction pipelining and RISC concepts”1989 James A. Weidenhammer: “For high speed I/O mechanisms”1989 Ralph L. Palmer: “For the IBM 604 electronic calculator”1989 Mina S. Rees: “For the ONR Computer R&D developmentbeginning in 1946”1989 Marshall C. Yovits: “For the ONR Computer R&D developmentbeginning in 1946”1989 F. Joachim Weyl: “For the ONR Computer R&D developmentbeginning in 1946”1989 Gordon D. Goldstein: “For his work with the Office ofNaval Research and computer R&R beginning in 1946”1990 Werner Buchholz: “For computer architecture”1990 C. A. R. Hoare: “For programming languages definitions”1991 Bob O. Evans: “For compatable computers”

Appendix III 5491991 Robert W. Floyd: “For early compilers”1991 Thomas E. Kurtz: “For BASIC”1992 Stephen W. Dunwell: “For project stretch”1992 Douglas C. Engelbart: “For human computer interaction”1993 Erich Bloch: “For high speed computing”1993 Jack S. Kilby: “For co-inventing the integrated circuit”1993 Willis H. Ware: “For the design of IAS and Johnniaccomputers”1994 Gerrit A. Blaauw: “In recognition of your contributionsto the IBM System/360 Series of computers”1994 Harlan B. Mills: “In recognition of contributions toStructured Programming”1994 Dennis M. Ritchie: “In recognition of contributions tothe development of UNIX”1994 Ken L. Thompson: “For his work with UNIX”1995 Gerald Estrin: “For significant developments on earlycomputers”1995 David Evans: “For seminal work on computer graphics”1995 Butler Lampson: “For early concepts and developmentsof the PC”1995 Marvin Minsky: “For conceptual development of artificialintelligence”1995 Kenneth Olsen: “For concepts and development of minicomputers”1996 Angel Angelov: “For computer science technologies inBulgaria”1996 Richard F. Clippinger: “For computing laboratory staffmember, Aberdeen Proving Ground, who converted the ENIACto a stored program”1996 Edgar Frank Codd: “For the invention of the firstabstract model for database management”1996 Norber Fristacky: “For pioneering digital devices”1996 Victor M. Glushkov: “For digital automation of computerarchitecture”1996 Jozef Gruska: “For the development of computer sciencein former Czechoslovakia with fundamental contributions to thetheory of computing and extraordinary organizational activities”1996 Jiri Horejs: “For informatics and computer science”1996 Lubomir Georgiev Iliev: “A founder and influentialleader of computing in Bulgaria; leader of the team that developedthe first Bulgarian computer; made fundamental and continuingcontributions to abstract mathematics and software”1996 Robert E. Kahn: “For the co-invention of the TCP/IPprotocols and for originating the Internet program”1996 Laszlo Kalmar: “For recognition as the developer of a1956 logical machine and the design of the MIR computer inHungary”1996 Antoni Kilinski: “For pioneering work in the constructionof the first commercial computers in Poland, and for thedevelopment of university curriculum in computer science”1996 Laszlo Kozma: “For development of the 1930 relaymachines, and going on to build early computers in post-warHungary”1996 Sergey A. Lebedev: “For the first computer in the SovietUnion”1996 Alexej A. Lyuponov: “For Soviet cybernetics and programming”1996 Romuald W. Marczynski: “For pioneering work in theconstruction of the first Polish digital computers and contributionsto fundamental research in computer architecture”1996 Grigore C. Moisil: “For polyvalent logic switching circuits”1996 Ivan Plander: “For the introduction of computer hardwaretechnology into Slovakia and the development of the firstcontrol computer”1996 Arnols Reitsakas: “For contributions to Estonia’s computerage”1996 Antonin Svoboda: “For the pioneering work leading tothe development of computer research in Czechoslovakia andthe design and construction of the SAPO and EPOS computers”1997 Homer (Barney) Oldfield: “For pioneering work in thedevelopment of banking applications through the implementationof ERMA, and the introduction of computer manufacturingto GE”1997 Francis Elizabeth (Betty) Snyder-Holberton: “For thedevelopment of the first sort-merge generator for the Univacwhich inspired the first ideas about compilation”1998 Irving John (Jack) Good: “For significant contributionsto the field of computing as a cryptologist and statisticianduring World War II at Bletchley Park, as an early worker anddeveloper of the Colossus at Bletchley Park and on the Univer-

550 Appendix IIIsity of Manchester Mark I, the world’s first stored program computer”1999 Herbert Freeman: “For pioneering work on the firstcomputer built by the Sperry Corporation, the SPEEDAC, andfor subsequent contributions to the areas of computer graphicsand image processing”2000 Harold W. Lawson: “For inventing the pointer variableand introducing this concept into PL/I, thus providing for thefirst time, the capability to flexibly treat linked lists in a generalpurposehigh level language”2000 Gennady Stolyarov: “For pioneering development in‘Minsk’ series computers’ software, of the information systems’software and applications and for data processing and data basemanagement systems concepts dissemination and promotion”2000 Georgy Lopato: “For pioneering development in Belarusof the ‘Minsk’ series computers’ hardware, of the multicomputercomplexes and of the ‘RV’ family of mobile computers for heavyfield conditions”2001 Vernon Schatz: “For the development of ElectronicsFunds Transfer which made possible computer to computercommercial transactions via the banking system”2001 William H. Bridge: “For the marrying of computer andcommunications technology in the GE DATANET 30, puttingterminals on peoples’ desks to communicate with and timesharea computer, leading directly to the development of the personalcomputer, computer networking and the internet”2002 Per Brinch Hansen: “For pioneering development inoperating systems and concurrent programming, exemplified bywork on the RC4000 multiprogramming system, monitors, andConcurrent Pascal”2002 Robert W. Bemer: “For meeting the world’s needs forvariant character sets and other symbols via ASCII, ASCII-alternatesets, and escape sequences”2003 Martin Richards: “For pioneering system softwareportability through the programming language BCPL widelyinfluential and used in academia and industry for a variety ofprominent system software”2004 Frances (Fran) E. Allen: “For pioneering work establishingthe theory and practice of compiler optimization”2005 [No award given]2006 Arnold M. Spielberg: ”For recognition of contributionto real-time data acquisition and recording that significantlycontributed to the definition of modern feedback and controlprocesses”2006 Mamoru Hosaka: “For recognition of pioneering activitieswithin computing in Japan”National Medal of Technologyand INNOVATIONGiven by the President of the United States, the NationalMedal of Technology and Innovation is “the highest honorbestowed by the President of the United States to America’sleading innovators.”Computer-Related Recipients1985AT&T Bell Laboratories: “For contribution over decades tomodern communication systems.”Frederick P. Brooks, Jr., Erich Bloch, and Bob O. Evans, InternationalBusiness Machines Corp.: “For their contributions to thedevelopment of the hardware, architecture and systems engineeringassociated with the IBM System/360, a computer systemand technologies which revolutionized the data processingindustry and which helped to make the United States dominantin computer technology for many years.”Steven P. Jobs and Steven Wozniak, Apple Computer, Inc.: “Fortheir development and introduction of the personal computerwhich has sparked the birth of a new industry extending thepower of the computer to individual users.”John T. Parsons and Frank L. Stulen, John T. Parsons Company:“For their development and successful demonstration ofthe numerically-controlled machine tool for the production ofthree-dimensional shapes, which has been essential for the productionof commercial airliners and which is seminal for thegrowth of the robotics, CAD-CAM, and automated manufacturingindustries.”1986Bernard Gordon, Analogic Corp.: “Father of high-speed analogto-digitalconversion which has been applied to medical, analytical,computer and communications products; founder of twocompanies with over 2,000 employees and over $100 million inannual sales and creator of a new master’s level institute locatedin Massachusetts to teach engineering leadership and projectengineering to engineers.”Reynold B. Johnson, International Business Machines Corp.:“Introduction and development of magnetic disk storage forcomputers that provided access to virtually unlimited amountsof information in fractions of a second and is the basis for timesharing systems and storage of millions of records. Over $10 billionin annual sales and over 100,000 jobs arose from this development.”William C. Norris, Control Data Corp.: “Advancement of microelectronics and computer technology and creation of one of theFortune 500—Control Data Corporation—which has over $5billion in annual sales and over 50,000 employees.”1987Robert N. Noyce, Intel Corp.: “For his inventions in the fieldof semiconductor integrated circuits, for his leading role in theestablishment of the microprocessor which has led to much

Appendix III 551wider use of more powerful computers, and for his leadership ofresearch and development in these areas, all of which have hadprofound consequences both in the United States and throughoutthe world.”1988Robert H. Dennard, IBM T.J. Watson Research Center: “Forinvention of the basic one-transistor dynamic memory cell usedworldwide in virtually all modern computers.”David Packard, Hewlett-Packard Company: “For extraordinaryand unselfish leadership in both industry and government,particularly in widely diversified technological fields whichstrengthened the competitiveness and defense capabilities of theUnited States.”1989Jay W. Forrester, Massachusetts Institute of Technology andRobert R. Everett, The MITRE Corp.: “For their creative workin developing the technologies and applying computers to realtimeapplications. Their important contributions proved vital tonational and free world defense and opened a new era of worldbusiness.”1990John V. Atanasoff, Iowa State University (Ret.): “For hisinvention of the electronic digital computer and for contributionstoward the development of a technically trained U.S. workforce.”Jack St. Clair Kilby, Jack Kilby Co.: “For his invention and contributionsto the commercialization of the integrated circuitand the silicon thermal print-head; for his contributions to thedevelopment of the first computer using integrated circuits; andfor the invention of the hand-held calculator, and gate array.”John S. Mayo, AT&T Bell Laboratories: “For providing the technologicalfoundation for information-age communications, andfor overseeing the conversion of the national switched telephonenetwork from analog to a digital-based technology forvirtually all long-distance calls both nationwide and betweencontinents.”Gordon E. Moore, Intel Corp.: “For his seminal leadership inbringing American industry the two major postwar innovationsin microelectronics—large-scale integrated memory and themicroprocessor—that have fueled the information revolution.”1991C. Gordon Bell, Stardent Computers: “For his continuing intellectualand industrial achievements in the field of computerdesign; and for his leading role in establishing cost-effective,powerful computers which serve as a significant tool for engineering,science and industry.”John Cocke, International Business Machines Corp.: “For hisdevelopment and implementation of Reduced Instruction SetComputer (RISC) architecture that significantly increased thespeed and efficiency of computers, thereby enhancing U.S. technologicalcompetitiveness.”Grace Murray Hopper, U.S. Navy (Ret.)/Digital EquipmentCorp.: “For her pioneering accomplishments in the developmentof computer programming languages that simplified computertechnology and opened the door to a significantly largeruniverse of users.”1992William H. Gates III, Microsoft Corp.: “For his early vision ofuniversal computing at home and in the office; for his technicaland business management skills in creating a world-wide technologycompany; and for his contribution to the developmentof the personal computer industry.”1993Kenneth H. Olsen, Digital Equipment Corp.: “For his contributionsto the development and use of computer technology; andfor his entrepreneurial contribution to American business.”1994[No computer-related recipients]1995Edward R. McCracken, Silicon Graphics, Inc.: “For his groundbreakingwork in the areas of affordable 3D visual computingand super computing technologies; and for his technical andleadership skills in building Silicon Graphics, Inc., into a globaladvanced technology company.”IBM Team: Praveen Chaudhari, IBM TJ Watson Research Center;Jerome J. Cuomo, North Carolina State University (formerlywith IBM); and Richard J. Gambino, State University of NewYork at Stony Brook (formerly with IBM): “For the discoveryand development of a new class of materials—the amorphousmagnetic materials—that are the basis of erasable, read-write,optical storage technology, now the foundation of the worldwidemagnetic-optic disk industry.”1996James C. Morgan, Applied Materials, Inc.: “For his leadershipof 20 years developing the U.S. semiconductor manufacturingequipment industry, and for his vision in building Applied Materials,Inc. into the leading equipment company in the world,a major exporter and a global technology pioneer which helpsenable Information Age technologies for the benefit of society.”1997Vinton Gray Cerf, MCI, and Robert E. Kahn, Corporationfor National Research Initiatives: “For creating and sustainingdevelopment of Internet Protocols and continuing to provideleadership in the emerging industry of internetworking.”1998Kenneth L. Thompson, Bell Laboratories, and Dennis M.Ritchie, Lucent Technologies: “For their invention of UNIX®operating system and the C programming language, whichtogether have led to enormous growth of an entire industry,

552 Appendix IIIthereby enhancing American leadership in the InformationAge.”1999Raymond Kurzweil, founder, chairman, and chief executiveofficer, Kurzweil Technologies, Inc.: “For pioneering and innovativeachievements in computer science such as voice recognition,which have overcome many barriers and enriched the livesof disabled persons and all Americans.”Robert Taylor (Ret.): “For visionary leadership in the developmentof modern computing technology, including computer networks,the personal computer and the graphical user interface.”2000Douglas C. Engelbart, director, Bootstrap Institute: “For creatingthe foundations of personal computing including continuous,real-time interaction based on cathode-ray tube displaysand the mouse, hypertext linking, text editing, on-line journals,shared-screen teleconferencing, and remote collaborative work.More than any other person, he created the personal computingcomponent of the computer revolution.”The IBM Corporation: “For 40 years of innovations in thetechnology of hard disk drives and information storage products.IBM is widely recognized as the world’s leader in basic datastorage technologies, and holds over 2,000 U.S. patents. IBMis a top innovator of component technologies—such as flyingmagnetic heads (thin film heads, and magneto resistive heads),film disks, head accessing systems, digital signal processing andcoding, as well as innovative hard disk drive systems. Some specificIBM inventions are used in every modern hard drive today:thin film inductive heads, MR and GMR heads, rotary actuators,sector servos and advanced disk designs. These advances outranforeign hard disk technology and enabled the U.S. industry tomaintain the lead it holds today.”2001Arun N. Netravali, Chief Scientist, Lucent Technologies andPast President of Bell Labs: “For his leadership in the field ofcommunication systems; for pioneering contributions thattransformed TV from analog to digital, enabling numerous integratedcircuits, systems and services in broadcast TV, CATV,DBS, HDTV, and multimedia over the Internet; and for technicalexpertise and leadership, which have kept Bell Labs at the forefrontin communications technology.”Jerry M. Woodall, Yale University: “For his pioneering role inthe research and development of compound semiconductormaterials and devices; for the invention and development oftechnologically and commercially important compound semiconductorheterojunction materials, processes, and relateddevices, such as light-emitting diodes, lasers, ultra-fast transistors,and solar cells.”new industries in wide bandgap semiconductors and enablingother new industries in efficient blue, green, and white light,full-color displays, high-power solid-state microwave amplifiers,more efficient/compact power supplies, higher efficiency powerdistribution/transmission systems, and gemstones.”Carver A. Mead, California Institute of Technology: “For hispioneering contributions to microelectronics that include spearheadingthe development of tools and techniques for modernintegrated-circuit design, laying the foundation for fabless semiconductorcompanies, catalyzing the electronic-design automationfield, training generations of engineers that have made theUnited States the world leader in microelectronics technology,and founding more than twenty companies.”Team of Nick Holonyak, Jr. (University of Illinois at Urbana-Champaign), M. George Craford (Lumileds Lighting Corp.)and Russell Dean Dupuis (Georgia Institute of Technology):“For contributions to the development and commercializationof light-emitting diode (LED) technology, with applications todigital displays, consumer electronics, automotive lighting, trafficsignals, and general illumination.”2003Robert M. Metcalfe: “For leadership in the invention, standardization,and commercialization of the Ethernet.”Watts S. Humphrey: “For his vision of a discipline for softwareengineering, for his work toward meeting that vision, and forthe resultant impact on the U.S. Government, industry, and academiccommunities.”2004Ralph H. Baer: “For his groundbreaking and pioneering creation,development and commercialization of interactive videogames, which spawned related uses, applications, and megaindustriesin both the entertainment and education realms.”2005Semiconductor Research Corporation: “For building the world’slargest and most successful university research force to supportthe rapid growth and advance of the semiconductor industry;for proving the concept of collaborative research as the firsthigh-tech research consortium; and for creating the concept andmethodology that evolved into the International TechnologyRoadmap for Semiconductors.”Xerox Corporation: “For over 50 years of innovation in marking,materials, electronics communications, and software thatcreated the modern reprographics, digital printing, and printon-demandindustries.”2006–2007[No computer-related recipients]2002Calvin H. Carter, Cree, Inc.: “For his exceptional contributionsto the development of silicon carbide wafers, leading to

Appendix IVComputer-Related OrganizationsThe following is a list of some important computer-relatedorganizations, including contact information.General Computer ScienceOrganizationsAmerican Society for Information Science (http:www.asis.org/)1320 Fenwick Lane, Suite 510, Silver Spring, MD 20910.Telephone: (301) 495-0900 e-mail: asis@asis.orgAssociation for Computing Machinery (http://www.acm.org/)2 Penn Plaza, Suite 701, New York, NY 10121-0701. Telephone:(800) 342-6626 e-mail: acmhelp@acm.orgComputing Research Association (http://www.cra.org) 1100Seventeenth Street, NW, Suite 507, Washington, DC 20036-4632. Telephone: (202) 234-2111 e-mail: webmaster@cra.orgIEEE Computer Society (http:www.computer.org) 1730 MassachusettsAve. NW, Washington, DC 20036-1992. Telephone:(202) 371-0101 e-mail: membership@computer.orgSoftware Engineering Institute (http://sei.cmu.edu) 4500 FifthAve., Pittsburgh, PA 15213-2612. Telephone: (888) 201-4479 e-mail: customer-relations@sei.cmu.eduApplication and Industry-SpecificGroupsAeA (formerly American Electronics Association) (http://www.aeanet.org/) 601 Pennsylvania Avenue NW, Suite 600,North Building, Washington, DC 20004. Telephone: (202)682-9110 e-mail: Web formsAmerican Association for Artificial Intelligence (http://www.aaai.org/) 445 Burgess Drive, Suite 100, Menlo Park, CA94025-3442. Telephone: 650-328-3123 e-mail: info7contact@aaai.orgAmerican Design Drafting Association (http://www.adda.org)105 East Main St., Newham, TN 38059. Telephone: (731)627-0802 e-mail: Web formAmerican Society for Photogrammetry and Remote Sensing(http://www.asprs.org) 5410 Grosvenor Lane, Suite 210,Bethesda, MD 20814-2160. Telephone: (301) 493-0290 e-mail: asprs@.orgAmerican Statistical Association (http://www.amstat.org) 732North Washington St., Alexandria, VA 22314-1943. Telephone:(703) 684-1221 e-mail: asainfo@amstat.orgAssociation for Library and Information Science Education(http:www.alise.org) 68 E. Wacker Place, Suite 1900, Chicago,IL 60601-7246. Telephone: (312) 795-0996 e-mail:contact@alise.orgAssociation for Multimedia Communication (http://www.amcomm.org) P.O. Box 10645, Chicago, IL 60610. Telephone:(773) 276-9320 e-mail: Web formAssociation of American Geographers (http://www.aag.org)1710 16th St. NW, Washington, DC 20009-3198. Telephone:(202) 234-1450 e-mail: gaia@aag.orgAssociation of Information Technology Professionals (http://www.aitp.org) 401 North Michigan Avenue, Suite 2400, Chicago,IL 60611-4267. Telephone: (312) 673-4793 e-mail: Web formCAM-I (Computer-Aided Manufacturing International) (http://cami.affiniscape.com) 6836 Bee Cave, Suite 256, Austin,TX 78746. Telephone: (512) 617-6428 e-mail: Web formComputing Technology Industry Association (CompTIA)(http://www.comptia.org) 1815 S. Meyers Road, Suite 300Oakbrook Terrace, IL 60181-5228. Telephone: (630) 678-8300 e-mail: Web formDigital Library Federation (http://www.digilib.org) 1755 MassachusettsAve. NW, Suite 500, Washington, DC 20036-2124.Telephone: (202) 939-4761 e-mail: dlfinfo@clir.orgElectronics Industries Alliance (http://www.eia.org/) 2500 WilsonBlvd., Arlington, VA 22201. Telephone: (703) 907-7500 e-mail: Web formInformation Technology Association of America (http://www.itaa.org) 1401 Wilson Blvd., Suite 1100, Arlington, VA22209. Telephone: (703) 522-5005 e-mail: Web directoryInternational Game Developer’s Association (http://www.igda.org) 19 Mantua Road, Mt. Royal, NJ 08061. Telephone:(856) 423-2990 e-mail: contact@igda.orgInternational Society for Technology in Education (http://www.iste.org) 1710 Rhode Island Ave. NW, Suite 900, Washington,DC 20036. Telephone: (800) 336-5191 e-mail: iste@orgInternational Technology Law Association (http://www.itechlaw.org) 401 Edgewater Place, Suite 600, Wakefield, MA 01800.Telephone: (781) 876-8877 e-mail: office@itechlaw.org553

554 Appendix IVInternational Webmasters Association (http://www.irwa.org/)119 E. Union St., Suite F, Pasadena, CA 91103. Telephone:(626) 449-3709 e-mail: via Web linksLibraries for the Future (http://www.lff.org) 27 Union SquareWest, Suite 204, New York, NY 10003. Telephone: (646)336-6236 e-mail: info@lff.orgLibrary and Information Technology Association (http://www.lita.org) American Library Association, 50 East Huron St.,Chicago, IL 60611-2795. Telephone: (800) 545-2433 e-mail: library@ala.orgOffice Automation Society International (http://www.pstcc.cc.tn.us/ost/oasi.html) 5170 Meadow Wood Blvd., Lyndhurst,OH 44124. Telephone: (216) 461-4803 e-mail: jbdyke@aol.comRobotics Industries Association (http://www.robotics.org) 900Victors Way, Suite 140, P.O. Box 3724, Ann Arbor, MI48106. Telephone: (734) 994-6088 e-mail: webmaster@robotics.orgSIGGRAPH [Graphics special interest group of the Associationfor Computing Machinery] (http://www.siggraph.org). e-mail: Web linksSociety for Information Management (http://www.simnet.org/)401 N. Michigan Ave., Chicago, IL 60611-4267. Telephone:312 644-6610 e-mail: info@simnet.orgSociety for Modeling and Simulation International (http://www.scs.org) P.O. Box 17900 San Diego, CA 92177-7900. Telephone:(858) 277-3888 e-mail: info@scs.orgSociety for Technical Communication (http://www.stc.org/) 901N. Stuart St., Suite 904, Arlington, VA 22203-1854. Telephone:(703) 522-4114 e-mail: stc@stc.orgSoftware & Information Industry Association (http://www.siia.org/) 1090 Vermont Ave. NW, Sixth Floor, Washington, DC20005-4095. Telephone: (202) 289-7442 e-mail: Web formTelecommunications Industry Association (http://www.tiaonline.org) 2500 Wilson Blvd., Suite 300, Arlington, VA 22201-3834. Telephone: (703) 907-7700 e-mail: tia@tiaonline.orgGovernment, Standards andSecurity OrganizationsAmerican National Standards Institute (ANSI) (http://ansi.org)1819 L Street NW, 6th Floor, Washington, DC 20036. Telephone:(202) 293-8020 e-mail: info@ansi.orgComputer Emergency Response Team (CERT) (http://www.cert.org) CERT Coordination Center, Software EngineeringInstitute, Carnegie Mellon University, Pittsburgh, PA15213-3890. Telephone: (412) 268-7090 e-mail: cert@cert.orgComputer Security Institute (http://www.gocsi.com/) 600 HarrisonSt., San Francisco, CA 94107. Telephone: (415) 947-6320 e-mail: csi@cmp.comDefense Advanced Research Projects Agency (DARPA) (http://www.darpa.gov). 3701 North Fairfax Drive, Arlington,VA 22203-1714. Telephone: (571) 218-4219 e-mail: WebformsInformation Systems Security Association (http://www.issa.org)9200 SW Barbour Blvd. #119-333 Portland, OR 97219.Telephone: (866) 349-5818 e-mail: Web formsInstitute for the Certification of Computing Professionals(http://www.iccp.org) 2350 East Devon Ave., Suite 115, DesPlaines, IL 60018-4610. Telephone: (847) 299-4227 e-mail:office@iccp.orgInternational Organization for Standardization (ISO) (http://www.iso.org) 1, ch de la Voie-Creuse, Case postale 56, CH-1211 Geneva 20, Switzerland. Telephone: +41 22 749 01 11e-mail: Web formsInternet Society (http://www.isoc.org/) 1775 Wiehle Ave., Suite102, Reston, VA 20190-5108. Telephone: (703) 326-9880e-mail: info@isoc.orgNational Center for Supercomputing Applications (NCSA)(http://www.ncsa.uiuc.edu) University of Illinois at Urbana-Champaign, 1205 W. Clark St., Room 1008, Urbana, IL61801. Telephone: (217) 244-0710 e-mail: tlbarker@ncsa.uiue.eduNational Telecommunications and Information Administration(http://www.ntia.doc.gov/) U.S. Dept. of Commerce, 1401Constitution Ave. NW, Washington, DC 20230. Telephone:(202) 482-1840 e-mail: Web directoryQuality Assurance Institute Worldwide (http://www.qaiworldwide.com.qai.html)2101 Park Center Drive, Suite 200,Orlando, FL 32835-7614. Telephone: (407) 363-1111 e-mail: Web directoryUrban and Regional Information Systems Association (http://www.urisa.org) 1460 Renaissance Drive, Suite 305, ParkRidge, IL 60068. Telephone: (847) 824-6300 e-mail: WebdirectoryWorld Wide Web Consortium (www.w3c.org) MassachusettsInstitute of Technology, 32 Vassar St., Room 32-G515,Cambridge, MA 02139. Telephone: (617) 253-2613 e-mail:Web linksAdvocacy GroupsAssociation for Women in Computing (http://www.awc-hq.org)41 Sutter St., Suite 1006, San Francisco, CA 94104. Telephone:(415) 905-4663 e-mail: info@awc-hq.orgBlack Data Processing Associates (http://www.bdpa.org) 6301Ivy Lane, Suite 700, Greenbelt, MD 20770. Telephone:(800) 727-BDPA e-mail: Web formsCenter for Democracy and Technology (http://www.cdt.org)1634 Eye St., NW, #100, Washington, DC 20006. Telephone:(202) 637-9800 e-mail: Web formComputer Professionals for Social Responsibility (http://www.cpsr.org) 1370 Mission St., 4th Floor, San Francisco, CA94103-2654. Telephone: (415) 839-9355 e-mail: cpsr@cpsr.orgElectronic Frontier Foundation (http://www.eff.org) 454 ShotwellSt., San Francisco, CA 94110-1914. Telephone: (415)436-9333 e-mail: information@eff.orgElectronic Privacy Information Center (http://www.epic.org)1718 Connecticut Ave. NW, Suite 200, Washington, DC20009. Telephone: (202) 483-1140 e-mail: Web formWomen in Technology (http://www.womenintechnology.com)717 Princess St., Alexandria, VA 22314. Telephone: (703)683-4033 e-mail: staff@womenintechnology.org

I n d e xBoldface page numbers denotemain entries; italic page numbersindicate illustrations.AA-0 231AACS (Advanced Access ContentSystem) 149Aaron (program) 25abacus 70, 226ABC (Atanasoff-Berry computer)30, 297Abelson, Harold 284About.com 350, 379AboutUs 122abstract data type. See dataabstractionabstract object 68Abstract Windowing Toolkit(AWT) 254accelerated graphics port (AGP)63, 214, 243Access (Microsoft) 131, 132Access Certificates for ElectronicServices (ACES) 79accessibility (data) 130–131accessibility (universal design). Seedisabled persons and computingaccountability, and privacy 384accounting applications 64accumulator 304ACE (Automatic ComputingEngine) 481A+ Certificate 80ACES (Access Certificates forElectronic Services) 79ACH (automated clearing house) 39ACLU v. Reno 125ACM (Association for ComputingMachinery) 7, 79, 267, 296,297, 404ACP (Associate ComputingProfessional) certificate 80Acrobat 257, 374, 504. See also PDFactive matrix display 199active RFID 405Active Server Pages (ASP) 1, 249,422, 491, 508. See also ASP.NETActiveX 89, 422, 508Ada 2in computer history 229enumerations in 184government funding for 404Pascal and 363sets in 185Simula and 431ADA (American with DisabilitiesAct) 152Ad-Aware 453address bus 51addressing 3, 3. See alsoindirection; pointersAnalytical Engine and35–36in ARPANET 247binding and 45bits and 51hexadecimals for 225indirect 375–377on Internet 155–158in list processing 282in machine code 28in memory 301in minicomputers 227in MS-DOS 321–322in multiprocessing 323with pointers 375–376variables in 490–491in virtual memory 302address register 304Adelman, Leonard 146, 181ad hoc computer grid 217administrative applications 64administrator status 136Adobe Systems 3–4. See alsoAcrobat; Illustrator; PageMaker;PDF; Photoshop; PostScript;PremiereADO.NET 306adoption scams 345AdSense 211, 344ADSL (asymmetric DSL) 162adult education 171Advanced Access Content System(AACS) 149Advanced Computing SystemsLaboratory (IBM) 10Advanced Graphics Port (AGP) 86Advanced Micro Devices (AMD)4–5, 86, 140, 218, 245Advanced Network and Services272Advanced Technology Attachment(ATA) 223advertising 164, 251. See alsoonline advertisingADVISE 119, 136adware 111, 344–345, 384,453–454AdWord 211Aegis 311Aero 307affective computing 313affiliate marketing 344agent-oriented programming 442agent software. See software agentsAge of Intelligent Machines, The(Kurzweil) 269Age of Spiritual Machines, The(Kurzweil) 269AGP (accelerated graphics port)63, 214, 243AGP (Advanced Graphics Port) 86agriculture 143Aho, Alfred V. 33AI. See artificial intelligenceAIBO robot dog 411AIFF (Audio Interchange FileFormat) 448Aiken, Howard 5, 231air traffic control system 399–400Ajax (asynchronous JavaScript andXML) 5–6, 6, 110AL. See artificial lifealarm system, in smart buildings434Alcatel 42“Alchemy and ArtificialIntelligence” (Dreyfus) 162Aldus 4Aldus Pagemaker. See PagemakerAlexander, Christopher 142Algol 6–7Backus-Naur Form and 38McCarthy’s work on 297Pascal and 362PL/I and 373recursion in 401Simula and 431Wirth’s work with 514algorithms 7–8in banking security 39in computer animation 16in computer science 109in computing 295for data compression 134error handling and 186genetic 8, 28, 75, 207–208Google PageRank 57, 210,211, 423, 480in graphics 106in graphics cards 214in implementation 394for memory management302in music 325–326in Pascal 362patentability of 245in pattern recognition 363for random numbergeneration 399for scheduling andprioritization 417–418for searching 446for search relevancy 423. Seealso PageRank algorithmin software engineering 444for sorting 446–448for speech recognition 452Alice (chatterbot) 84, 515Alienware 140Allen (robot) 59Allen, Frances E. 515Allen, George 377Allen, Paul 206alpha version 394Altair 206, 228, 304, 366, 519AltaVista 422Alto 320, 517ALU (arithmetic logic unit) 23,119, 120, 305Amazin’ Software 174Amazon.com 8–9, 44–45CRM used by 123data mining by 136entrepreneurship and 184in mashups 294online research with 349“Search inside the Book”on 167software sales of 294World Wide Web and 518Amazon Unbox 327ambient intelligence 314AMD (Advanced Micro Devices)4–5, 86, 140, 218, 245AMD64 4Amdahl, Gene Myron 10–11American with Disabilities Act(ADA) 152America Online (AOL) 11, 11–12chat on 83instant messaging on 477as ISP 252MapQuest under 292Netscape acquired by 16as online information service350–351Amicus Attorney 274Amnesty International 76analog 12, 12–13, 13, 147, 213, 371analog computer 13–14, 14,226, 510. See also differentialanalyzer555

556 IndexAnalytical Engine 35–36, 36, 226,301, 392anchor 234Anderson, Harlan 41AND operator 51, 54Andreessen, Marc 14–15, 15, 184,503, 518Android 437Angle, Colin 59, 60, 253animal behavior, cellular automataand 75animated GIF 214, 507animation, computer 16–17, 104,194. See also computer graphicsanonymity and the Internet 17censorship and 76in chat 83cyberbullying and 126cyberterrorism and 118with digital cash 147on file-sharing networks 193fraud and 345identity and 237reputation and 480ANSI BASIC 40ANSI characters 81ANSI COBOL 90anthropometry 47Antikythera Mechanism 13, 405Anti-Phishing Phil 370Anti-Phishing Working Group 370antitrust 107, 206–207, 274, 306antivirus software 100, 111, 417.See also securityANTLR 361AOL. See America OnlineApache 81, 306, 352, 508API. See application programinterfaceAPL (a programming language) 18,204, 490, 491Apollo spacecraft 449Apple I 18, 258, 519Apple IIin education 99, 169emulator for 179hard disk of 222IBM PC and 366market entry of 106Pascal on 362success of 18, 258VisiCalc on 452word processing on 516Wozniak’s work on 519Apple Corporation 18–19. See alsoiPhone; iPod; Macintoshin computing history 228DRM and 150in FireWire development 197IBM PC and 236Jobs at 257–258Kay at 264Omidyar at 343Wozniak at 519Apple DOS 353Apple LaserWriter 379Apple Lisa 18Apple Logo (Abelson) 284Apple Newton 220–221, 364AppleScript 19applet 19–20. See also JavaApple TV 19appliance computing 107, 177, 434application layer 334application program interface (API)20, 20–21C in 66for content managementsystems 116graphics in 105in mashups 294for operating systems 354virtual 494Application Service Provider (ASP)broadband and 107in computer industry trends108in computing history 229groupware and 217Microsoft Windows and 309office suites through 107Oracle on Demand 356PC market and 367for remote backup services37SAP as 415software installation and 244in software market 294for SOHO market 230word processor from 517application service provider (ASP)6, 21–22application software 22auditing of 31backup of 37benchmarks for 43bugs in. See bugs anddebuggingcommenting in 158compatibility of 94copyright for 245CORBA for 118custom 293device drivers and 144document model and 160for early computers 427for education 170ergonomics of 185error handling in 186file formats in 135files in 192firewalls and 197fonts in 200free access to 21freeware 427–428help systems in 225in identity theft prevention238installation of 244internationalization of246–247Internet-related 249in law enforcement 273legal 273–274licensing violations 445for Linux 279, 280literacy in 109localization of 246–247for Macintosh 287macros in 289for management informationsystems 292marketing of 107–108,293–294mathematics 145, 295–296,338, 453, 458. See alsospreadsheetmessage passing in 303multiprocessing and 324for music 326with OS X 357for PDAs 364plug-in versions of 374–375portability of 95presentation 32, 64, 380,380–381, 492. See alsoMicrosoft PowerPointproject management 342,389–390, 418, 444quality assurance in. Seequality assurance,softwareregistration of 244renting 21reverse engineering 404–405for RSS 412–413by SAP 415scheduling and prioritizationof 417–418in service-orientedarchitecture 426shareware 427–428for supply chain management462threading in 324as trade secret 245–246types of 22updates for 244user documentation for 159,471validation of 445Web services for 508–509application suite 23. See alsoMicrosoft Officein computer industry 107document model and 160from Google 211market for 206marketing of 293in office automation 342spreadsheet in 453word processor in 517APT (Automatically ProgrammedTool) 98Aqua 357arcade games 103–104archive attribute 191archive systems. See backup andarchive systemsArchon (game) 174arithmetic coding 134arithmetic expressions 354arithmetic logic unit (ALU) 23,119, 120, 305Arnie Street 326ARPANETbulletin board systemsand 61Cerf and 78in computer history 228cyberspace and 125distance education on 153e-mail and 177funding for 212hypertext in 182Internet and 247network for 266Roberts’s work on 145Sutherland’s work on 463array 23–25, 24. See also hashingin C 65in computer science 109data in 128as data type 138data types in 137in data warehouse 139in FORTRAN 202in hash sort 448in heapsort 447list compared to 137–138,282logical errors in 61art and the computer 25, 25–26artificial intelligence (AI) 26–28academic credentials for 79in automatic programming33Brooks’s work in 59in chatterbots 83–84cognitive science and 92–93computer science in 110computer vision in 112creativity in 25cybernetics in 511dangers of 261–262data models in 351Dreyfus’s work in 161–162in education 99epistemology and 369in expert systems 187, 188Feigenbaum’s work in 190in games 103government funding of 212for image interpretation 239for information retrieval 241Joy on 261–262knowledge representation in266–267Kurzweil’s work in 268Licklider and 277LISP used in 204, 280–281,297McCarthy’s work in 297Minsky’s work in 313in natural languageprocessing 330ontologies in 351Papert’s work in 359pattern recognition in 363philosophy and 369programming profession and386–387Prolog used in 390research institutions in 403risk and 409in robotics 411in science fiction 418, 419in search engines 423in semantic Web 424Shannon’s work in 427simulation and 432singularity from 269Smalltalk for 434software agents in 289, 442for software testing 395in technological singularity432–433Turing in 481Weizenbaum in 509–510artificial life (AL) 28artificial intelligence in 27cellular automata in 75finite state machines and 196genetic algorithms in 208robotic 411simulation and 432technological singularityand 433artificial limbs 335Art of Computer Programming, The(Knuth) 267ASCII characters 81, 81–82, 236,265Asheron’s Call 104Asia 108Asimov, Isaac 418, 433Ask Jeeves 241ASP. See application serviceproviderASP (active server pages) 1, 249,422, 491, 508. See also ASP.NETA-Space 119ASP .NET 1, 306assembler 5, 28–29, 29, 95, 288,388assertion 188, 266assistive devices 268, 425Associate Computing Professional(ACP) certificate 80Association for ComputingMachinery (ACM) 7, 79, 267,296, 297, 404associative arrays 24“As We May Think” (Bush) 182

Index 557Asymetrix Toolbook 32asymmetric multiprocessing 323asynchronous JavaScript and XML(Ajax) 5–6, 6, 110asynchronous processes 154ATA (Advanced TechnologyAttachment) 223Atanasoff, John Vincent 30, 226,297Atanasoff-Berry computer (ABC)30, 297Atari 104, 179, 205, 258, 264Atkinson, Bill 322ATM. See automatic teller machinesAtom 413AT&T 473, 477–478, 486. See alsoBell Laboratoriesattachments 111, 134, 177, 193attenuation 191Attila (robot) 56AT (Advanced Technology)machine 62attributes 191, 201, 232auctions, online 31, 100, 120, 343.See also eBayAuctionWeb 165, 343Audio Interchange File Format(AIFF) 448auditing in data processing 31, 130AU format 448Augmentation Research Center182augmented finite state machines 59“Augmenting Human Intellect:A Conceptual Framework”(Engelbart) 182authentication 31–32, 39, 146, 181authoring systems 32automata 196, 410. See also cellularautomata“Automata Studies” (Shannon andMcCarthy) 427automated cars 71–72automated clearing house (ACH)39Automatically Programmed Tool(APT) 98Automatic Computing Engine(ACE) 481automatic programming 33automatic tabulating machine 229,230, 294, 341, 392automatic teller machines (ATM)authentication at 32in banking 39biometrics used with 48–49real-time processing in 400as terminal 476touchscreens in 478transaction processing in478–479automotive computers 71, 71–72,177, 293avatars 237–238, 348awk 33–34, 83, 365, 485–486AWT (Abstract WindowingToolkit) 254axioms, in Prolog 390BBabbage, Charles 35–36, 36analog computer of 226mechanical computer of 294memory and 301printer design by 381punched cards and 392on statistics 458Babel Fish 271back door, in Clipper Chip 146,181background process. See demonbackup and archive systems 36–37in auditing 31in content managementsystems 116copy protection and 117, 150in database administration130–131in disaster planning andrecovery 152as fair use 246fault tolerance with 189floppy disks and 200in libraries 276outsourcing of 108tape for 467Backus, John W. 38, 202, 404Backus-Naur form (BNF) 38, 38,110, 278backward chaining 188Baker, Nicholas 276Ballistic Research Laboratory 167ballots 175bandwidth 38, 298, 335. See alsobroadbandBankers Trust 44banking and computers 39biometrics used in 48–49identity theft and 238investing 348personal software for 195phishing and 370smart card in 435terrorism against 127Bank of America 370, 509banner ads 344Bardeen, John 42, 85, 404Bard’s Tale, The (game) 174Barlow, John Perry 123, 124BarnesandNoble.com 349Bartik, Jean 515BASH (Bourne Again Shell) 429BASIC 39–40classes and 88games in 103Gates and 305graphics in 105, 105as interpreter 252loop in 285–286Microsoft and 305parsing 360in personal computers 228procedures in 384–385strings in 82basic input/output system (BIOS)49–50, 54, 236, 319, 405Bateson, Gregory 124battle management 311baud 298Baudot character set 265Bayes, Thomas 40Bayesian analysis 40–41, 270BBN (Bolt Beranek and Newman)247, 277, 284, 404BBS. See bulletin board systemsbeams 493–494Beesley, Angela 500behavioral biometrics 48Being Digital (Negroponte) 331Bell, C. Gordon (Bennet) 41–42Bell Laboratories 42art research at 25C++ at 67charged-couple device at 371government funding of 212research of 404Ritchie at 409Shannon at 427Stroustrup at 459telecommunications and 473UNIX and 486Bell’s Law of Computer Classes 41benchmark 43Bendix 227Benford, Gregory 28Bense, Max 25Beowulf clusters 217, 462Berkeley, Edmund 463Berkeley Open Infrastructure forNetwork Computing (BOINC)117Berkeley Software Distribution(BSD) 261, 486Berners-Lee, Tim 43–44in computer history 229Dertouzos and 141as entrepreneur 184HTML invented by 232in Internet growth 247semantic Web and 424on user-created content 487in World Wide Webdevelopment 518Bernstein, Daniel 125, 181, 246Berry, Clifford E. 30Bertillon, Alphonse 47best fit algorithm 302beta testing 395Better Business Bureau 345Bezos, Jeffrey P. 8, 44, 44–45, 184Bigelow, Julian 510Bill and Melinda Gates Foundation207Billings, John Shaw 229bill payment, online 39Billpoint 146–147Bina, Eric 15BINAC 167, 296, 381binary data 128, 225binary search 448binary tree 479binding 45–46bins 223biodiversity, measuring 46bioinformatics 46–47, 110, 136, 179biology and computing 75biometrics 27, 47–49, 48for authentication 32employment in 179in flash drives 198in law enforcement 273military use of 310pattern recognition in 363with smart cards 436BIOS (Basic Input-Output System)49–50, 54, 236, 319, 405biotechnology 262bird flight 75BISON 361bitmapped fonts 201bitmapped image 50, 50, 81, 214bits 50–51, 51, 52, 204, 298BitTorrent 193, 413bitwise operations 51–52, 54black, in CYMK 93BlackBerry 220, 364, 437black box testing 395blacklists 370blindness 151block-structured languages 491Blogger.com 52, 211Bloglines 52blogs and blogging 52–53advertising in 344censorship of 76in cyberbullying 126on eBay 166freedom of speech for 125Google in 211hypertext in 234in Internet growth 248as journalism 259netiquette in 332in office automation 342political activism and 377RSS for 412user-created content of 487World Wide Web and 518blue, in RGB 93Blue Gene 462Blue Origin 45Bluetooth 53, 273, 299, 487, 513Blu-ray 75, 205, 446BMP (Windows bitmap) 214BNF (Backus-Naur form) 38, 38,110, 278board games 103body language, in robots 56–57boids 28BOINC (Berkeley OpenInfrastructure for NetworkComputing) 117Bolt Beranek and Newman (BBN)247, 277, 284, 404Bomis 500Boneh, Dan 317bookmarks 234, 374books, technical 471bookstore, online. See Amazon.comBoole, George 40, 53–54Boolean bitwise operators 51Boolean data type 138Boolean operators 53–54in branching statements 55Differential Analyzer and426with flags 197for information retrieval 240in searching 422–423in switched computers 295Boot Camp 19, 288booting 353boot sequence 54–55Bootstrap Institute 182Borland 20Borland Sidekick 368Bosack, Leo 87botnet 100, 111, 451bots. See software agentsbound port 303bounds, of arrays 24Bourne, Steven R. 429Bourne Again Shell (BASH) 429Bourne Shell 429, 485Boyer, Amy 126bragging rights 100Braille 151brain implants 336BrainKeeper 511Brainstorms Community 407branching statements 55Boolean operators in 54in C 65in COBOL 91in error handling 187in flowcharts 200functional languages and 204in PL/I 373in procedural languages 388in structured programming460Brand, Stewart 407Brattain, Walter 42, 85, 404breakpoint 61Breazeal, Cynthia 27, 56, 56–57, 60Bricklin, Daniel 366, 452Brief Code 297Brin, David 384Brin, Sergey 57, 210, 358broadband 57–59. See also cablemodem; DSL; satellite Internetservicewith AOL 12cable modems for 69

558 Indexdata communications over133in digital divide 149for distance education153–154fiber optic cable for 191firewalls and 196, 197in Internet growth 248ISPs for 252modems and 316net neutrality and 332office applications over 107packet-sniffing and 100streaming and 459telecommunications and 473for videoconferencing 492video distribution and 327for VoIP 497Web page design and 507broadcast journalism 259–260Brooks, Frederick 386Brooks, Rodney 27, 56, 59–60,253, 289, 475browser. See Web browserbrowser history, Ajax pages and 6“brute force” strategy 84–85BSD (Berkeley SoftwareDistribution) UNIX 261, 486bubble sort 447, 447Buckimaster, Jim 120buddy system 302budgeting software 195buffering 60. See also queuein data acquisition 130for graphics display 105in I/O processing 243overflows in 60pointers for 376queue in 396in streaming 459in tape drives 467in video capture 493bugs and debugging 61in C 66CASE tools for 74in compiling 96data and, threat to 36dynamic binding and 46error handling and 186in programming environment388quality assurance and 394risk of 408technical support and 470bulletin board systems (BBS)61–62on ARPANET 247in computer history 228conferencing systems and114cultures of 125cyberspace and 125early use of 11in Internet development 247Rheingold and 407as social networking 440for technical support 470bullet train 408bullying 126bump mapping 106Burks, Arthur 499“Burning Chrome” (Gibson) 419Burroughs 459Burroughs, William 70bus 62, 62–63bits and 51in boot sequence 54in chipset 86clock speed and 90CPU and 304in Ethernet network 283for graphics cards 214in IBM PC 236for I/O processing 242–243for modem 316on motherboard 319in multiprocessing 323in personal computers 228Bush, Vannevar 13, 63, 182, 212,233Bushnell, Nolan 258business applications of computers63–64. See also application suiteblogging in 53in disaster planning andrecovery 152enterprise computing183–184ergonomics and 185financial software and 195groupware in 217Macintosh and 287management informationsystems for 291–292mashups 294online advertising 344–345PCs 366personal informationmanagers 368portals 379project management software389–390SAP software in 415software installation and 244supply chain management462surveillance 383text in 81Web filters 505Business Objects 415Business Software Alliance 445bus mastering 62bus snooping 323“Buy It Now” 165byte 50–51, 51, 52, 204, 298byte code 19, 95, 253Byte magazine 260, 366CC (language) 65–66BASIC and 40bitwise operator symbolsin 52branching statements in 55commenting in 158in computer history 228C shell and 429current use of 389development of 42, 404, 410enumerations in 184–185functions in 385logic errors in 61macros in 288numeric data in 338Pascal and 363Perl and 365PL/I and 374pointers in 375–376porting to C++ 68procedures in 385professional programmingwith 386program libraries in 276recursion in 401strings in 82syntax errors in 61variables in 490, 491viability of 389C# (language) 66, 307C++ (language) 67–69classes in 88commenting in 158compiling 96in computer history 228development of 459–460Eiffel and 173–174enumerations in 184–185error handling in 187inheritance in 340for Internet applicationsprogramming 249Java and 255in Microsoft Windows 309operators in 341Pascal and 363pointers in 376–377procedures in 385program libraries in 276Simula and 431cable modem 38, 58, 69, 162–163,299cache 69–70buffering and 60in chipset 86in client-server computing89in computer engineering 101CPU and 304, 305development of 10for file server 192for hard disks 223in information retrieval 240memory for 301in multiprocessing 323in Web browsers 503CAD/CAM (computer-aided designand manufacturing) 64, 98–99CAI (computer-aided instruction)32, 99, 169, 311calculation speed 298calculator 5, 70–71, 341, 392. Seealso mechanical calculatorcalendaring, in groupware 217call. See procedurescamcorders, digital 372, 446camera-ready copy 142cameras 108, 223, 371–372. Seealso photography, digitalcamouflage 203Campbell, John W. 418cancelbots 451Canion, Rod 184CAN-SPAM Act 370, 451capacitive touchscreens 478capacitors 30Čapek, Carl 410, 418carbon dioxide emissions 216card readers. See punched cardsand paper tapeCareerJournal 348Carnegie Mellon HumanComputation 117Carnegie Mellon University 403Carpal Tunnel Syndrome (CTS)185cars and computing 71, 71–72,177, 293cartography 208–209cartridge drives 37, 258, 467,467–468cascading style sheets (CSS) 5–6,72, 72–73, 152, 233, 507case. See branching statementsCASE (computer-aided softwareengineering) 73, 73–74, 200,443Case, Steve 11, 12, 350case statement 55cash, digital 146–147Casino City 346cassette tape 37, 258, 467, 467–468CAT (computerized tomography)scanning 300cataloging, library 275Cate, Fred H. 383cathode ray tube (CRT)in defense computingprojects 212for graphics 104, 105as memory 301in monitors 199, 317for terminals 476CB Simulator 350CBT (computer-aided instruction)32, 99, 169, 311CCM (CORBA Component Model)118CCP (Certified ComputingProfessional) certificate 80CCTV (closed-circuit television)164, 273CDC (Control Data Corporation)99, 121, 227, 323, 461CD copy protection 149–150CDMA (Code DivisionMultiplexing Access) 514CD-ROM and DVD-ROM 74, 74–75in boot sequence 55for data backup 37, 200in game consoles 205in laptops 272lasers for 356multimedia and 322for music files 449reusable media for 216Sony and 446CDT (Center for Democracy andTechnology) 125, 440cell chip 205, 305cell phones. See also smartphonebroadband access through 58by Motorola 320MySpace and 440smartphones and 108texting on 477touchscreens on 478with VoIP 497cell processors 462cells, of memory 224cellular automata 28, 75, 75–76,432, 499. See also Game of Lifecensorship and the Internet 76of blogs 53centralization and 440in China 211, 250encryption and 246policy and 472political extremism and 377Center for Democracy andTechnology (CDT) 125, 440CenterStage 299central computer 154centralization 439–440central processing unit. See CPUCentronics 360Cerf, Vinton D. 78CERN 43, 247, 403certificate, digital 78–79, 79,223–224certification authority 78–79, 79certification of computerprofessionals 79–80, 131, 171,356, 386, 506Certified Computing Professional(CCP) certificate 80Certified Netware Administrator(CNA) certificate 80Certified Netware Engineer (CNE)certificate 80CFCs (chlorofluorocarbons) 216CGA (Color Graphics Adapter) 213CGI. See computer graphicsCGI (common gateway interface)80, 80–81, 249, 365, 508

Index 559chads 175, 392chairs, ergonomic 185channels 83, 243, 290, 323chaos 203Chapel 324characters and strings 81–83in C 65classes of 88compression of 134as data types 138file transfer protocols and193pointers and 376processing 33–34, 402, 485character sets 457charge-coupled device (CCD) 42,371, 416, 493charitable solicitations, fraudulent345Charles Schwab 348chat, online 83on AOL 350community and 440on CompuServe 350conferencing and 113cyber culture and 125filtering 505in groupware 217identity used in 237instant messaging comparedto 477pseudonymity in 17Rheingold on 407texting compared to 477chatterbots 83–84, 442, 481Chautauqua 153check clearing 39checksum 133, 186, 194chess and computers 26, 84, 84–85, 427, 480Child On-line Protection Act 505Children’s Internet Protection Act76, 505Children’s Machine 331Chinablogging in 53censorship in 76, 211, 251in computer industry 108computing in 143digital divide in 149Internet anonymity in 17Internet cafés in 250, 250phishing operators in 370policy and 472pollution controls in 216software counterfeiting in445Yahoo! and 523Chinese Room 93chip 85–86. See also CPU(central processing unit);microprocessorbenchmarks for 43clock speed and 90in game consoles 205, 235by Intel 244in Macintosh 245optical computing and 356chipset 86, 101chlorofluorocarbons (CFCs) 216Chomsky, Noam 278Christenson, Ward 194chron 140Chuang, Isaac L. 395Church, Alonzo 86–87, 295Church theorem 87Church thesis 87cipher machines 180circuit design 295circular buffer 60circular queue 396, 397CISC (complex instruction setcomputing) 402Cisco Systems 80, 87Citizendium 500citizen journalism 259Civilization strategy game 99,103, 103Clark, Jim 15, 184Clarke, Arthur C. 418classes 88, 88Ada and 2for APIs 20binding and 45–46in C# 67in C++ 68, 459–460in computer science 109data abstraction in 129data structures and 138data types and 138in Eiffel 173encapsulation with 180in Java 254–255in Lua 286in Microsoft .NET 306in object-orientedprogramming 67–68,340–341, 388in ontologies 351in Ruby 413in Simula 431in Smalltalk 433structs compared to 67templates for 475in UML 315variables and 88virtual 88class frameworks 89clean room 4, 404–405clearinghouses 39“click fraud” 344clicking (mouse) 321click through 344client-server computing 89–90,183, 192, 255, 303, 476Climate Savers ComputingInitiative 216Clinton, Hillary 377, 524Clipper Chip 146, 181clock 90clock speed 90, 101, 119–120, 130closed-circuit television (CCTV)164, 273closed feedback loop 13cloud computing 21Cloud Nine 519cluster analysis 458cluster computing 216–217clustering 136clusters 216, 323CLUT (color lookup table) 93, 94CMC (Computer-MediatedCommunications) 113CMOS (complementary metal oxidesemiconductor) 49, 54, 301CMS (color matching system) 93CMS (content managementsystems) 115CMYK 93CNA (Certified NetWareAdministrator) certificate 80CNE (Certified NetWare Engineer)certificate 80CNET 260, 293–294, 428coalescence 302COBOL (Common Business-Oriented Language) 90–92commenting in 158current use of 389for databases 131Hopper and 231PL/I and 373professional programmingand 386RPG and 412Y2K and 522cochlear implant 335Cocke, John 402Codd, Edgar F. 131codec 92, 493Code Division Multiplexing Access(CDMA) 514code generation 96Code and Other Laws of Cyberspace(Lessig) 274–275code profiling 8Code Version 2.0 (Lessig) 274–275code word, in Hamming Code 186coffee shops 250Cog (robot) 27, 56, 59–60, 411cognitive prosthetics 336cognitive science 92–93in computer science 110, 391neural network and 313,336–337Papert’s work in 359senior citizens and 425technological singularityand 433Cognitive Tutor 99Cohen, Harold 25coherence 323coherency, cache 70Colby, Kenneth 509collaborative filtering 289collating sequence 82collision 223, 283, 448Colmerauer, Alain 390Color Graphics Adapter (CGA) 213color in computing 50, 93–94, 94color laser printers 382Colossus 226Colossus (film) 378, 418COM (Common Object Model) 160comma-delimited files 135command interpreter 55command processor 321comments, in program code 158commercial applications 22Commodore 228common gateway interface (CGI)80, 80–81, 249, 365, 508Common Language Runtime 306Common LISP 281–282common object request brokerarchitecture (CORBA) 89, 118,154, 310communications 124, 241, 242, 248communications buffer 60Communications Decency Act 76,274Communications Nets (Kleinrock)266communications theory 295Compaq 107, 184, 228, 237, 273,366compatibility and portability 94–95, 135, 465compiler(s) 402, 490, 494compilers 95, 95–97, 96binding in 45in COBOL 91in computer history 227in computer science 110data and 128for Eiffel 173for embedded systems 178enumerations in 184–185for FORTRAN 202Hopper’s work on 231interpreters and 252for Java 255for Lua 286parsers and 361in Pascal 362program libraries in 277Smalltalk and 433stack and 456compile-time binding 45complementary metal oxidesemiconductor (CMOS) 49,54, 301COMPLEMENT bitwise operators51completeness 267complex instruction set computing(CISC) 402complexity. See computability andcomplexitycomponent object model. SeeMicrosoft .NETcomposite, in hypertext 234composite data types 138Comprehensive Perl ArchiveNetwork (CPAN) 365compression. See data compressionComptometer 70CompuServe 214, 252, 350, 351computability and complexity97–98Church and 87in computer science 109Physical Symbol SystemHypothesis and 93quantum computing and 395in scientific applications 419Turing on 481computational biology 46Computek 141computer-aided design andmanufacturing (CAD/CAM) 64,98–99computer-aided instruction (CAI)32, 99, 169, 311computer-aided softwareengineering (CASE) 73, 73–74,200, 443computer animation 16–17, 104,194. See also computer graphicsComputer-based EducationResearch Laboratory 169computer-based-training 32, 99,169, 311computer crime 100–101, 408.See also hackers and hacking;identity theft; law enforcementand computers; online fraud andscams; securityavatars and 237–238banking and 39on Craigslist 121cyberlaw and 123–124digital certificates and 78–79on eBay 166firewalls and 196forensics in 102–103by hackers 220Internet growth and 248Internet regulation and 251law enforcement and 273policy on 472RFID and 406Computer Decency Act 125computer engineering 101–102computer forensics 101, 102–103,118, 179, 273computer games 103–104. See alsoonline gamesanimation in 16beta testing of 395in education 99, 169by Electronic Arts 174finite-state machines in 196fractals used in 203

560 Indexgraphics in 106, 194haptic interfaces for 221Lua for 286natural language processingin 330in popular culture 378random number generationfor 399simulation in 432virtual reality as 496computer graphics 104–106, 105.See also animation, computer;image processinganimated 507on Apple II 258benchmarks for 43color in 93–94compression of 134, 203computer science in 110in education 99in games 103, 104geometry in 295graphics cards for 213–214Macintosh for 287measurement units for 298monitor for 317scheduling algorithms and418in scientific applications420–421Sutherland’s work on 4633D 213–214in virtual reality 496in Web page design 507on workstations 517Computer History Museum 42computer industry 106–109certification in 80entrepreneurs of 184establishment of 227globalization and 108,209–210hackers in 219journalism and. Seejournalismnanotechnology in 329–330computerized tomography (CAT)scanning 300computerized typography 267,483. See also fontscomputer languages. Seeprogramming languagescomputer literacy 109, 148–149,170, 171, 225Computer-MediatedCommunications (CMC) 113computer music 325–326,448–449computer platforms 41Computer Power and Human Reason(Weizenbaum) 509–510computer professionals,certification of 79–80Computer Professionals against theABM 510Computer Professionals for SocialResponsibility (CPSR) 438computer programming. Seeprogrammingcomputer research, governmentfunding of 212–213, 404, 462,472computersBoolean logic in 54dependency on 439development of 226Eckert’s work on 167–168energy consumption of215–216e-waste from 216government-funded 212greenhouse emissions and216invention of 30for modeling cognition 92pollution from 216recycling of 140resource consumption of 216in science fiction 418–419self-replicating 329switches in 295Turing machines equivalentto 97Computers and Thought(Feigenbaum and Feldman,eds.) 190computer science 7–8, 109–110,124, 138, 171, 277, 294–295. Seealso education in computer fieldComputer Science Corporation(CSC) 293Computer Society of the Instituteof Electrical and ElectronicsEngieers 404computer technicians 108computer theory 109Computer Usage Corporation(CUC) 293computer virus 110–112data and 36in denial-of-service attacks100e-mail and 177identity theft from 238Internet growth and 248Microsoft Windows and 309Spafford’s work on 450from spam 451user status and 137computer vision 27, 112, 363, 411Computerworld 260computing 313, 314Computing Research Association(CRA) 404Computing Technology IndustryAssociation (CompTIA) 80concurrent programming 112–114,154, 263conditionals 204conferencing, video 83, 322, 342,474, 492–493, 497. See alsotelepresenceconferencing systems 114–115,125, 407, 440, 474confidence factors 188confrontation, constructive 218congruential algorithm 399connectionists 93Connection Machines 461consciousness 369Consolidated Controls 182constants 115constructive confrontation 218constructivist learning 144, 284,359constructor function 88, 340consumer electronics 19, 140, 445.See also specific typesconsumer privacy 383–384container 92, 160content management 115–116, 179content management systems(CMS) 115, 132Content Scrambling System (CSS)149contextual advertising 211Control Data Corporation (CDC)99, 121, 227, 323, 461controls, in Microsoft Windows 308control structures. See alsobranching statements; loopin Ada 2in Algol 7in awk 33–34in BASIC 40in C 65in Pascal 514in PL/I 373in pseudocode 390–391in scripting languages 421in shell scripting 429in structured programming443in Tcl 468in Z3 525control unit 119–120, 120Conway, John 28, 75cookies 116, 211, 384, 453cooperative processing 116–117,155, 462cooperative programs 117co-ops 143Copernic 423, 423coprocessor 243, 304copyleft 352copy protection 117–118. See alsodigital rights managementcyberlaw and 123in data security 130digital convergence and 148of digital libraries 167digital rights management for149–150in e-books 166file-sharing networks and193First Amendment and 246hacking 219–220reverse engineering and 405copyright 245, 275, 445CORBA (Common Object RequestBroker Architecture) 89, 118,154, 310CORBA Component Model (CCM)118Corel Draw 143Core Service Technician exam 80Corley, Eric 246Corning 191correspondence classes 153counterculture 378counterfeiting 166, 436. Seealso software piracy andcounterfeitingcounterterrorism and computers118–119, 127, 220country codes, for DNS 155–157Count Zero (Gibson) 220CourseBuilder (Discovery Systems)32CPAN (Comprehensive PerlArchive Network) 365CP/Mdevelopment of 353in microcomputers 236, 366Microsoft and 206MS-DOS and 321UNIX and 486word processing on 516Xmodem for 194CPSR (Computer Professionals forSocial Responsibility) 438CPU (central processing unit)35, 119–120, 120. See alsomicroprocessorarithmetic logic unit in 23benchmarks for 43bits and 51cache for 60, 69–70chips for 86in concurrent programming113in Dell computers 140evolution of 107in information retrieval240by Intel 218, 318–319in I/O processing 242–243,243in laptops 272in Macintosh 287measurement units for 298on motherboard 319in multiprocessing 323in multitasking 324–325scheduling andprioritization of 417speed of 90CRA (Computing ResearchAssociation) 404Craigslist 120–121, 294, 348Crawford, Chris 104Cray, Seymour 121, 121–122, 227,461Cray Research 121–122, 227, 324,461CRC (cyclical redundancy check)186, 194Creative Commons 275Creative Labs Zen 327Creative Suite 3 (Adobe) 4credit card transactions 39, 146credit ratings, “repairing” 345crime. See computer crimeCRM. See customer relationshipmanagementCRT. See cathode ray tubeCrusoe 478cryptography. See also encryptionin ARPANET 145ciphers in 180in DRM 150hashing in 223–224number theory in 295public key 32, 145–146,180–181, 181quantum computing and 396in RFID 406Shannon’s work in 427Turing’s work in 481CSC (Computer ScienceCorporation) 293C shell (csh) 261, 365, 429, 485CSS (cascading style sheets) 5–6,72, 72–73, 152, 233, 507CSS (Content Scrambling System)149CTS (Carpal Tunnel Syndrome)185CUC (Computer UsageCorporation) 293Cuckoo’s Egg (Stoll) 458culture, and computing 314Cunningham, Howard (Ward)122–123, 511Cu-SeeMe 83, 492customer relationship management(CRM) 123at Amazon.com 9ASPs for 21business use of 64in computing history 229data mining in 136employment in 179natural language processingin 330SAP software for 415technical support in 470cyan, in CYMK 93CyberCash 146cybercommons 438cyberlaw 123–124, 237–238,274–275, 347–348cybernetics 110, 124, 277, 510–511

Index 561Cybernetics of Control andCommunication in the Animal andthe Machine (Wiener) 511cyberpunk 220, 335, 419cyberspace advocacy groups124–125cyberspace and cyber culture 125–126, 391, 419, 482–483cyberstalking and harassment 100,126, 248, 252, 523cyberterrorism 126–127computer crimes in 100countering 118–119data backup and 37disaster planning and 152hackers in 220information warfare and 242Internet growth and 248online gambling and 346threat of 439Cyc 27, 267, 351cyclical redundancy check (CRC)186, 194cylinders, in hard disks 222DDAC (digital to analog converter)317daemon. See demonDahl, Ole-Johan 431DailyStrength.com 367daisy-wheel printer 381DAQ (data acquisition device) 129,130Dark Web 127DARPA (Defense AdvancedResearch Projects Agency) 113funding of 212Kay and 263Licklider at 277multiprocessing languageand 324networks and 334research of 311, 404Sutherland at 463DARPA automated vehiclechallenge 71Dartmouth Summer ResearchProject on Artificial Intelligence281, 297Darwin 357DAT (digital audio tape) 446data 128. See also backup andarchive systemsin classes 88constants 115in distributed computing154in LISP 281in pattern recognition 363redundancy in 427repurposing 139in service-orientedarchitecture 426unanticipated use of 408in XML 520data abstraction 128–129data accessibility 130–131data acquisition 110, 129, 129–130,419data acquisition device (DAQ)129, 130databaseBoolean operators in 54for business data processing64caching for 70for CAD 98client-server computingand 89CORBA for 118in CRM 123data dictionary for 135data mining of 135–136data security in 137in decision support systems139distributed computing for154hard disk space for 223hashing in 223, 224information retrieval from240–241for library catalogs 275in management informationsystem 292middleware for 310for online research 349PHP and 372for real-time processing 400record-level security in 137relational model for 131–132,139, 292, 455. See alsodatabase managementsystemssearching in 446for software agents 289in software engineering 73sorting in 446storage of 192templates in 475WAIS for 248for wikis 511database administration 130–131,178database management systems(DBMS) 131, 131–133automatic programmingin 33benchmarks for 43for cartography 208computer science in 110development of 131early market for 206management informationsystems and 292network traffic and 334object-oriented programmingand 341in office automation 342by Oracle 356SQL for 455data breaches 137data bus. See busdata communications 133–134with Bluetooth 53broadband. See broadbandclock speed and 90in computer science 110error correction in 186measurement units for 298in UNIX 410data compression 134, 134–135codecs for 92of digital photographs 372on hard disks 223of images 50, 203, 214, 239of MP3 files 448–449in networks 334of PDFs 364redundancy and 241in streaming 459data conversion 135data dictionary 73–74, 135Data division 91Data Encryption Standard (DES)39, 145, 180, 317Data General 106, 516data glove 221–222data integrity 130, 131, 132, 194data link layer 334data list 282data mining 27, 135–136cookies in 116in counterterrorism 118, 119in CRM 123data warehouses for 139in e-commerce 168employment in 179expert systems for 188Google’s use of 211in information retrieval 241knowledge representationin 267management informationsystems and 292Microsoft research on 404natural language processingin 330neural networks in 337pattern recognition in 363privacy and 384statistics in 458data models. See ontologies anddata modelsData Over Cable Service InterfaceSpecification (DOCSIS) 69data processingfor bank transactions 39batch processing 257buffering in 60in business 63–64, 291in client-server computing89in COBOL 91in flowcharts 200job control language for 257mainframes for 290in scientific applications419–420, 420data security 136–137. See alsosecurityin database administration130at “hot spots” 250Internet growth and 248online backup servicesand 37in operating systems 354risk and 408satellite service and 416user accounts in 354data storage 36, 37, 74–75, 89, 222,299, 445–446data structures 137–138. See alsoarray; branching statements;enumerations and sets; hashing;loop; queue; treein Algol 7in algorithm design 8in APIs 20in BASIC 88bit manipulation in 52in computer science 109data types compared to 138lists for 282object-oriented programmingand 339in Pascal 88queue 396–397in Ruby 413in Simula 431systems programming and465data types 138. See also classes;enumerations and setsabstract 128–129in Ada 2in Algol 7in BASIC 40binding and 45in C 65in C++ 68checking 66, 68in COBOL 91in compiling 96in computer science 110conversion of 61, 67in data structures 137data structures comparedto 138for FORTRAN 202in interpretation of data 128for knowledge representation266in LISP 281–282in Lua 286numeric 338in object-orientedprogramming 340in Pascal 362, 514in Perl 365in PHP 373in PL/I 373in procedural languages 388procedures and 385Python and 392in Ruby 413in scripting languages 421in Smalltalk 433in structured programming443for variables 490data validation 186–187, 197data warehouse 135, 139, 139, 292dates, storage of 522dBase 131DBMS. See database managementsystemsDCE (Distributed ComputingEnvironment) 310DCOM (Distributed ComponentObject Model) 89, 154DDR (double data rate) SDRAM301deafness 151Dean, Howard 377debit card transactions 39debugging. See bugs and debuggingDEC Alpha 402decimal numbers 338decision making, Feigenbaum’swork in 190decision statements. See branchingstatements; loopdecision support system (DSS)139–140decompilation 405decrement operation 65DeCSS 149, 246DECUS 488DEC VAX 227deductive synthesis 33Deep Blue 26, 85Deep Thought 85defragmentation 222–223DejaNews 333delegates 67deletion, from list 282del.icious.us 294, 523Dell, Inc. 108, 140, 184, 237, 366Dell, Michael 140, 184Delphi 114demo 428democracy 439demon 140–141, 144DENDRAL 27, 187, 190denial-of-service (DOS) attacks100, 111, 242Department of Defense. SeeARPANET; DARPADepartment of Homeland Security119, 136dependencies 389

562 IndexDertouzos, Michael L. 141DES (Data Encryption Standard)39, 145, 180, 317Descartes, Rene 295D. E. Shaw Company 44design documents 159design patterns 122, 142Design Patterns (book) 142Desk Set (film) 378desktop publishing (DTP) 4, 18,64, 142–143, 287, 483, 517desktop replacement. See laptopcomputersdestructor function 88deterministic games 103developing nations and computing108, 143–144, 149, 209device driver 144–145, 145assembly languages and 29BIOS and 49in boot sequence 55in computer science 110CPU and 304for hard disks 223in operating systems 353, 354Plug and Play and 374in software installation 244systems programmer and465UNIX and 485device-independent bitmap (DIB)214Devol, Joseph 182DHCP (Dynamic HostingConfiguration Protocol) 469Dhrystone 43DHTML (dynamic HTML) 161,232–233. See also HTML;XHTMLDiablo II 104dialog boxes 308dial-return satellite system 416dial-up modem access 38, 58DIB (device-independent bitmap)214dictionary 134, 201, 270, 271. Seealso data dictionaryDidiWiki 511difference engine 35–36Differential Analyzer 13, 14, 63, 426Diffie, Bailey Whitfield 145–146,180diffraction 191DigiCash 146digital 12, 12–13, 13, 147digital audio tape (DAT) 446digital camcorders 372digital cameras 108, 223, 371–372.See also photography, digitaldigital cash 146–147digital certificate 78–79, 79, 223–224Digital Chocolate 174digital convergence 59, 147, 147–148, 331, 378, 473, 507. See alsoubiquitous computingdigital dashboard 148, 294digital divide 58, 109, 148–149,170, 172, 439Digital Editions (Adobe) 4Digital Equipment Corporation(DEC) 41, 187, 261, 467, 516.See also PDP minicomputerdigital libraries 166–167, 211, 260Digital Millennium Copyright Act(DMCA) 150, 246, 405digital music and video players.See music and video players,digitaldigital photography. Seephotography, digitalDigital Research 236, 321digital rights management (DRM)149–150, 166, 246, 326. See alsocopy protectiondigital signature 32, 39, 146digital subscriber line. See DSLdigital to analog converter (DAC)317digital video recording (DVR)163–164digitizing tablet 215, 215Dijkstra, Edsger W. 150, 150–151,374, 460diodes 86Dipmeter Advisor 187Direct2D 105Direct3D 214direct deposit 39direct memory access (DMA) 243directories 191direct-recording electronic (DRE)175DirectX 105, 214Dirt Dog (robot) 253disabled persons and computing151–152Ajax pages and 6JavaScript and 256neural interface for 269senior citizens and 425smart homes for 434speech synthesizer for 268user interface and 489virtual reality and 496voting systems and 176disassembly 405disaster planning and recovery37, 152Discovery Systems CourseBuilder32discrete data analysis 458discrete mathematics 296discrimination net 190disk array. See RAIDdisk cache 60, 70, 223disk compression 223disk controllers 223disk drives 55, 70. See also CD-ROM and DVD-ROM; flashdrive; floppy disk; hard diskdiskette. See floppy diskdisplay. See flat-panel display;monitordistance education 153, 153–154,170, 322distracted driving 72, 327–328Distributed Component ObjectModel (DCOM) 89, 154distributed computing 113, 154–155, 324, 354, 426, 459, 462Distributed ComputingEnvironment (DCE) 310distributed database system 188,292, 303, 334distributed denial-of-service(DDOS) attacks. See denial-ofserviceattacksdistributed object computing 89,118distributed processing 310diversity 179divisions, in COBOL 91DLLs (dynamic link libraries) 20,277, 277, 309DMA (direct memory access) 243DMCA (Digital MillenniumCopyright Act) 150, 246, 405DNA 316, 316–317DNS (domain name system) 154,155–158, 247, 251, 469, 508DOCSIS (Data Over Cable ServiceInterface Specification) 69Dr. Dobbs’ Journal 260doctors, ratings of 367–368documentation 158, 159–160,225, 471documentation of programcode 74, 158–159. See alsodocumentation; technicalwritingdocument model 160–161, 192Document Object Model (DOM)160, 161, 233, 256documents, XML 520DOM (Document Object Model)160, 161, 233, 256domain name system (DNS) 154,155–158, 247, 251, 469, 508domain squatting 158Donahoe, John 166dongle 117doping 86DOS. See denial-of-service attacks;MS-DOSDOS-SHELL 322DOS/Windows Service Technicianexam 80dot-com bustAmazon.com and 9, 45AOL and 12ASPs in 21in computing history 229in e-commerce 168employment after 179recovery from 108women in computing and515Yahoo! and 523dot-matrix printers 379, 381,381–382dot pitch 318Dot project 67DoubleClick 212double data rate (DDR) SDRAM301double precision float 338doubly linked lists 282downward compatibility 94, 135“Drafting Dan” 98dragging 321Dragon Systems 452DRAM (dynamic random accessmemory) 218, 301DRE (direct-recording electronic)175Dreamweaver (Macromedia) 4, 507Drexler, K. Eric 329Dreyfus, Hubert 93, 161–162, 297drill and practice programs 99drive connection 86driver. See device driverDRM (digital rights management)149–150, 166, 246, 326. See alsocopy protectiondrone aircraft 311Drudge, Matt 259drum, in laser printer 382drum scanners 417Drupal 52DSL (digital subscriber line) 38,58, 69, 162–163, 163, 299, 335DSL access Multiplexer (DSLAM)162DSS (decision support system)139–140DTP. See desktop publishingdual-core processors 4, 19, 245,305, 324“Dummies” series 159, 471Dungeons and Dragons 104, 237,347DUP 201DV (Digital Video) 493DVD copy protection 149, 246DVD-ROM. See CD-ROM and DVD-ROMDvorak keyboard 185, 265DVR (digital video recording)163–164Dynabook 263, 273, 433dynamic arrays 24dynamic binding 46, 490Dynamic Hosting ConfigurationProtocol (DHCP) 469dynamic HTML (DHTML) 161,232–233. See also HTML;XHTMLdynamic link libraries (DLLs) 20,277, 277, 309dynamic random access memory(DRAM) 218, 301dynamic scoping 491Eearly binding 46ease of use 37, 137eBay 31, 165–166Craigslist and 120–121entrepreneurship and 184founder of 342–344in mashups 294reputation system of 480World Wide Web and 518EBCDIC (Extended Binary-CodedDecimal Interchange Code) 81EBNF (extended Backus-Naurform) 38e-books 9, 166–167, 260, 382, 466e-cash 146–147eCharge 146Echelon 181, 383Eckert, J. Presper 167–168, 184,226, 226, 296, 499. See alsoUNIVACEckert-Mauchly ComputerCorporation 167, 231, 296. Seealso Eckert, J. Presper; Mauchly,John WilliamEclipse 122, 235, 352, 388ECMAScript 256ecology and computers 75e-commerce 168–169, 169Amazon.com in 8–9, 45Andreessen in 15anonymity in 17auctions in 31authentication in 32certification for 80in computer history 229computer science in 110CRM in 123data mining in 136digital cash for 146–147encryption in 181, 503expert systems for 188fraud in 100in Internet growth 248mainframes used in 290management informationsystems in 292natural language processingin 330Omidyar in 343policy on 472security in 101in software market 294Web page design for 507World Wide Web and 518ECP (Extended Capabilities Port)360ECPA (Electronic CommunicationsPrivacy Act) 383

Index 563Edelman, Leonard 316Edison, Thomas 403EDO (Extended Data Out) 301EDP (electronic data processing)341EDS (Electronic Data Systems)16, 293educational fraud 345Educational Research Laboratory99education and computers 169–171.See also computer-aidedinstruction (CAI)computer-aided instruction99in computer history 229computer literacy in 109in developing countries 143in digital divide 149employment and 179Logo for 284–285, 359long-distance 153, 153–154multimedia and 322Papert and 359PCs in 366robotics in 411Smalltalk for 434social impact of computingin 439Stoll on 458videoconferencing in 492webcams in 504–505webmaster skills in 506education in computer field 79–80,171–172, 179, 363, 514, 515EDVAC 167, 227, 498–499EEPROM (electrically erasableprogrammable read-onlymemory) 49, 436EFF (Electronic FrontierFoundation) 124–125, 150, 275,440, 445effectuators 178, 178EFT (electronic funds transfer) 39EGA (Enhanced Graphics Adapter)213e-government 172–173EIDE (Enhanced IDE) 86, 223EIES (Electronic InformationExchange System) 114Eiffel 173–174eigenfaces 4880-core processor 305EISA (Extended ISA) bus 62eldercare robots 183electrical current, in hard drives222electrically erasable programmableread-only memory (EEPROM)49, 436electricity, access to 143Electric Minds 407electromagnetic radiation, frommonitors 185Electronic Arts 174–175electronic calculators 70–71Electronic CommunicationsPrivacy Act (ECPA) 383electronic data processing (EDP)341Electronic Data Systems (EDS)16, 293Electronic Frontier Foundation(EFF) 124–125, 150, 275, 440,445electronic funds transfer (EFT) 39Electronic Information ExchangeSystem (EIES) 114electronic ink 382–383electronic library 166–167, 211, 260electronic mail. See e-mailelectronic music 325Electronic Music Studio 325Electronic Privacy InformationCenter (EPIC) 125, 440electronic voting systems 175,175–176element 23, 138, 520Elementary Perceiver andMemorizer (EPAM) 190eListening Post 326Eliza (chatterbot) 26, 83, 442,481, 509Ella (chatterbot) 83Ellis, Jim 333Ellison, Larry 356else statements 55EMACS 387Emacs 456e-mail 176–177, 177advertising in 344on ARPANET 247business use of 64in computing history 228data compression in 134encryption of 181filtering 451, 505fraud in 345in groupware 217in identity theft 238Internet and 518in Internet growth 247–248in journalism 259netiquette in 332netnews and 333in office automation 342persistence of 332personal informationmanagers and 368phishing with 369–370senior citizens’ use of424–425on smartphones 437spam in 451for technical support 470viruses spread by 100, 111wiretapping 273from Yahoo! 523e-mail filters 41embedded systems 177–178, 178Ada for 2in cars 71engineering of 102Forth for 202marketing of 107microprocessors in 305operating systems for 354PC market and 367real-time processing in 400in smart cards 435in ubiquitous computing 484in wearable computers 501Y2K and 522embedding, in documents 160emerging technologies. See trendsand emerging technologiesEmerson Electric 320emotion 56, 313Emotion Machine, The (Minsky)313employment in the computer field108, 171–172, 178–179, 439employment schemes 345emulation 179–180, 405, 476, 494Encapsulated PostScript (EPS) 214encapsulation 88, 88, 109, 129,180, 341Encore Computer 41encryption 180–181. See alsocryptographyfor authentication 32in banking systems 39censorship and 76in computer security 100for copy protection 117in data security 137Diffie and 145digital certificates and78–79under First Amendment 246of flash drives 198in networks 334of PDFs 364privacy and 383public key 32, 78–79, 79,145–146, 180–181, 181quantum computing and395supercomputers and 462of VoIP 497for voting systems 176in Web browsers 503on wireless networks 513encyclopedias, multimedia 322endless loop 286energy consumption, of computers215–216Energy Star 215–216Engaged 114Engelbart, Douglas 182, 233, 320Engelberger, Joseph 182–183engineering 110, 208engineering applications 75, 130Engineering Research Associates(ERA) 121Enhanced Graphics Adapter (EGA)213Enhanced IDE (EIDE) 86, 223Enhanced Parallel Port (EPP) 360ENIAC (Electronic NumericalIntegrator and Computer)in computing history226–227development of 525Eckert’s work on 167government funding of 212Mauchly’s work on 296patent dispute over 297in popular culture 378programming in 386user interface for 488von Neumann and 498Enigma cipher 180, 226, 481enterprise computing 183–184Enterprise Resource Planning(ERP) 415entrepreneurs in computing 184,252entropy, in information theory 241enumerations and sets 67, 184–185environment, computers’ impact on215–216, 229Environment division 91EPAM (Elementary Perceiver andMemorizer) 190EPIC (Electronic PrivacyInformation Center) 125, 440Epinions.com 480epistemology 267, 369EPP (Enhanced Parallel Port) 360EPS (Encapsulated PostScript) 214ERA (Engineering ResearchAssociates) 121ergonomics of computing 185–186,265, 318Ericsson Corporation 53eroticism, virtual 125ERP (Enterprise ResourcePlanning) 415error codes 187error correction 186, 186in data communication 133,427file transfer protocols and193, 194hashing in 224in information theory241–242mathematics in 295in modems 316in networks 334in programming environment388quantum computing and 395in RAID 398serial ports and 425in tape drives 467error handling 186–187, 373,408, 427eShop 343Estonia 242Estrada, Joseph 198Estridge, Phillip “Don” 236ETH (Swiss Federal Institute ofTechnology) 362, 514Ethernet network 38, 283, 299ethnic diversity 179eToys 264E*Trade 348Eudora 428eUniverse 440Evans, David 463Evans and Sutherland 463even parity 186events, in Microsoft Windows 308Everquest (game) 104, 347evidence 102–103, 147evolution, in genetic algorithms207evolutionary biology 46evolutionary programming. Seegenetic algorithmsevolutionary software engineering444e-waste 216ex 261Excel (Microsoft) 160, 452–453,454expansion slots 62, 62expert systems 187–188, 188. Seealso DENDRAL; SHRDLUartificial intelligence in 27in automated programming33computer science in 110in decision support systems139for fault diagnosis 189Feigenbaum’s work with 190fuzzy logic in 204genetic algorithms in 208knowledge engineering in190knowledge representation in266, 267for medical field 300Prolog for 390risk and 409exponent 338exponential time 98expressions 354–355, 490. See alsoregular expressionext3 192extended ASCII characters 81extended Backus-Naur form(EBNF) 38Extended Binary-Coded DecimalInterchange Code (EBCDIC) 81Extended Capabilities Port (ECP)360Extended Data Out (EDO) 301extremism 377eye, biometric scanning of 48eyestrain 318

564 IndexFFacebook 16, 440–441, 487, 494facial scanning 48factories, CAD/CAM in 98–99fail-safe 189, 408Fairchild Semiconductor 4, 85,218, 318fair use 246false color 239, 421false positives, from Bayesianalgorithms 41FAQ (Frequently Asked Questions)470farming 143FAT (file allocation table) 191, 321fat client 89fault coverage testing 395fault tolerance 39, 155, 178,189–190Federal Privacy Act 383–384Federal Wire Act 346Fedora 279feedback 56, 124feedback loop 510feedback system, on eBay 165–166,343, 480Fefferman, Nina 441Feigenbaum, Edward 187, 190Feldman, Julian 190Felt, Dorr E. 70Fermi, Enrico 432ferrite core memory 301Feynman, Richard 329, 395fiber optics 58, 162, 190–191, 356fiber-to-the-home (FTTH) 191fiction, hypertext used for 234Fido BBS 61FidoNet 247FIFO (first in, first out) 60, 138,396Fifth Generation, The (Feigenbaumand McCorduck) 190Fifth Generation ComputerProgram 390file 191–192, 217, 264, 321, 353,410file allocation table (FAT) 191, 321file conversion 135file extensions 192file formats 37, 94–95, 135,163–164file permissions 136–137, 248File & Serve (Lexis) 274file server 107, 192–193, 235,335, 396. See also client-servercomputing; RAIDfile-sharing and P2P networks 193anonymity in 17counterfeit software on 445Electronic FrontierFoundation and 125liability of 246for music and videodistribution 326of protected content 150service providers and 332file transfer protocols (FTP) 193–194, 248, 518film industry and computing 16,104, 194–195Filo, David 379, 422, 523filters, image processing 239financial calculators 195financial software 195fingerprints 48, 49finger scanning 48finite-state machine 195–196, 196,278, 481Fiorina, Carly 515Fios (Verizon) 58, 69, 191Firefly Networks 289Firefox 374–375, 504firewall 100, 111, 196–197, 334FireWire 197, 493First Amendment 124–125, 246“First Draft of a Report on theEDVAC” (von Neumann) 498first fit algorithm 302first in, first out (FIFO) 60, 138,396FISA (Foreign IntelligenceSurveillance Act) 119, 383Fitel 44flag 197–198flaming 17, 83, 114, 331Flash (Macromedia) 4, 20, 32,374, 507flash and smart mobs 198, 407, 477flash drive 37, 198–199, 200, 446,487flash memory 4, 272, 301, 372flatbed scanner 416flat file database model 131flat-panel display 199, 199, 318FLEX 263Flickr 294, 523floating ads 344floating point numbers 338floating-point units (FPUs) 61,138, 305, 323floppy disk 199–200in Apple 519capacity of 74CD-ROM replacement of 74copy protection of 117in IBM PC 236Sony and 445viruses on 111in word processors 516flops 298flowchart 73, 73, 200, 200flow control, in datacommunication 133flowers, robotic 57FLOW-MATIC 90, 231FOIA (Freedom of InformationAct) 173Folding@Home 46–47, 217, 462fonts 3, 110, 143, 200–201, 201,364, 507. See also typography,computerizedforce-feedback systems 221, 496Foreign Intelligence SurveillanceAct (FISA) 119, 383fork statement 113formalism 162formal language 278formatting, of hard disks 222forms 80–81, 256, 470Forster, E.M. 418Forth 201–202, 456FORTRAN 202–203current use of 389development of 404mathematics and 295for mathematics libraries296PL/I and 373procedures in 384professional programmingand 386Fortress 113, 324forums 350forward chaining 188FPS 43fractals in computing 134, 203,203, 295, 401fragmentation 222–223, 302framesin artificial intelligence 27,313of data packets 283in data transmission 133in expert systems 188for knowledge representation266–267for language processing278–279in natural languageprocessing 330frameworks 6, 20, 89, 95, 173. Seealso Microsoft .NETFrank, Barney 346fraud, online 100, 344, 345–346,349, 472. See also identity theftFree Culture (Lessig) 274–275Freedom of Information Act (FOIA)173freedom of speech 124, 125Freescale Semiconductors 320Free Software Foundation 429,456, 477–478, 486Free Speech Movement 378free trade 209–210freeware 104, 293–294, 352,427–428Frequently Asked Questions (FAQ)470Fritz 9 84Front Row 357FTP (file transfer protocol) 193–194, 248, 518FTTH (fiber-to-the-home) 191FUD (fear, uncertainty, and doubt)10Fuegelman, Andrew 427Fujitsu 108Full Spectrum Warrior (game) 311functional languages 67, 203–204,286, 338. See also LISPfunctions 384–385in APIs 20, 20binding and 45–46in C 66in C# 67in C++ 68in computer science 109, 110in data abstraction 129in functional languages203–204in Korn shell 429in LISP 281, 389in Lua 286macros and 288–289object-oriented programmingand 339, 443in Plankalkül 526programming languagesand 388recursive 401in Ruby 413in spreadsheets 453for strings 82in structured programming443virtual 88fund-raising 377future event, probability of 40–41Future Shock (Toffler) 432fuzzy logic 204, 337, 356fuzzy set 204Ggain, in DAQ performance 130Galvin Manufacturing Corporation320gambling, online 346–347game consoles 108, 174, 205–206,235, 305. See also Nintendo Wii;PlayStation; XboxGame of Life 28, 75, 75games. See computer games; onlinegamesgame theory 103, 432, 498GAMM (Gesellschaft fürangewandte Mathematik undMechanik) 7Gantt charts 389GarageBand 326garbage collection 224, 281Gardner, Martin 75Garmin 293Garriott, Richard 104Gates, William, III (Bill) 79, 184,206–207, 207, 305–306, 321, 430Gateway 366gateway programs 80gateways 177, 247, 248gauges 129GDI (Graphics Device Interface) 308geeks 378, 515gender diversity 179General Dynamics 320General Electric 509General Motors 183General Public License (GPL3)150, 352, 457, 478General Services Administration79generative grammar 278gene sequencing 46genetic algorithms 8, 28, 75,207–208genetics 27, 46, 188, 262Genghis (robot) 59Geographical Information Systems(GIS) 208–209, 404geometry 295German Aerodynamics ResearchInstitute 525germanium 85Gershenfeld, Neil R. 395Geschke, Charles 3, 379Gesellschaft für angewandteMathematik und Mechanik(GAMM) 7Gibson, William 125, 419. See alsoNeuromancer (Gibson)GIF (graphics interchange format)94, 134, 214gigabyte 51, 298Gilmore, John 124GIS (Geographical InformationSystems) 208–209, 404Gise, Preston 44glare 185global flags 197–198globalization and the computerindustry 179, 209–210, 229, 472Global Positioning System (GPS)209, 292Global System of MobileCommunications (GSM) 436,514global variables 491Gmail 211GNU Linux. See LinuxGNU Project 279, 352, 429, 456,477–478Gnutella 193Go (game) 85Godel, Kurt 295Goldstine, Herman 296, 499Google 210–212advertising business of 344,346, 358blogging and 52censorship in China and 76Cerf at 78in Chinese market 108digital library of 166, 167founding of 57, 358mashups and 294for online research 350

Index 565PageRank algorithm of 57,210, 211, 423, 480phone platform from 437searching with 423in social networking 441Yahoo! and 523YouTube and 524Google Apps 21, 107, 211, 217,294, 306Google Book Search 167, 211Google Docs & Spreadsheets 21,107, 211, 294, 517Google Earth 211, 292–293Google Groups 333–334Google Language Tools 271Google Maps 211, 292–293, 294,423Google News 211Google Pack 21Google Product Search 211Gopher 248, 518Gosling, James 255“GO TO Considered Harmful”(Dijkstra) 151Gouraud shading 106government 49, 76, 172–173, 181,250, 436government funding of computerresearch 212–213, 404, 462, 472GPL3 (General Public License)150, 352, 457, 478GPS (Global Positioning System)209, 364, 384Grand Theft Auto series 104graphical user interface. See userinterfacegraphics. See computer graphicsgraphics card 213, 213–214BIOS and 49–50chipset for 86games and 104in IBM PC 236in I/O processing 243in laptops 272microprocessor for 305on motherboard 319in PCs 322performance of 106Graphics Device Interface (GDI)308graphics engine 105–106graphics formats 94, 214–215graphics interchange format (GIF)94, 134, 214graphics modeling 105–106graphics tablet 215, 215graphing calculators 71Gray, Elisha 525greedy algorithm 8green, in RGB 93greenhouse emissions 216green PC 101, 215–216Greiner, Helen 60, 253grid computing 87, 155, 216–217,494Grokster 246groupware 217–218Grove, Andrew S. 218, 318GSM (Global System of MobileCommunications) 436, 514GUI. See user interfaceGulf War 242Gulliver’s Travels (Swift) 418Gutmans, Andi 372HHackers (Levy) 482hackers and hacking 219–220. Seealso computer crime; securityof application serviceproviders 21banking and 39copy protection and 246in cyber culture 125IBM and 235Mitnick and 314in open-source movement352in popular culture 378Stallman and 456Stoll and 458of voting systems 176hacktivism 127hafnium 86HAL 9000 (character) 59Halo (game) 306Halting problem 97Hamming Code 186Handbook of Artificial Intelligence(Feigenbaum, ed.) 190hand geometry 48handheld scanner 416handwriting recognition 220–221,221, 466, 489hanging chads 175, 392Hannibal (robot) 56haptic interfaces 221–222harassment 100, 126, 248, 252,523hard disk 222, 222–223BIOS and 49bits in 50in boot sequence 55for data backup 37development of 404for file servers 192in game consoles 205in IBM PC 236in information retrieval 240in laptops 272tape drives and 467for virtual memory 302hardware 95, 137, 240, 245Harvard Mark I 5, 61, 231, 498Harvey, Brian 285hashing 24, 223–224, 240, 365,448hash sort 448Haskell language 204Hawking, Stephen 151Hawkins, Trip 174Hayek, F. A. 500Hazen, Harold 510HD-DVD 75HDTV 75head-mounted display (HMD)496, 501health, personal 300–301, 367–368, 436heap 24, 224heapsort 447hearing damage, from musicplayers 327heat 101, 305Heinlein, Robert 98Hellman, Martin 145, 180“Hello World” 67Help America Vote Act 176help desks 108HelpMate (robot) 183, 410HelpMate Robotics, Inc. 183help systems 224–225, 233, 308,471. See also technical supportheuristic 8Heuristic Compiler 33Hewlett-Packard (HP) 16, 237, 258hexadecimal system 225–226high-level language 29, 227,252–253, 278, 288, 337. See alsoC (language); C++ (language);FORTRANhigh-speed Internet. See broadbandHigh Tech Heretic (Stoll) 458highway system, automated 71–72Hilbert, David 87Hillis, Daniel 461history (Web browser) 234history of computing 226–229HMD (head-mounted display)496, 501Hoare, Anthony 33Hoare, C. A. R. 447Hoff, Marcian E. “Ted” 304,318–319Holberton, Betty 515Holland, John 28Hollerith, Herman 229–230, 458Homebrew Computer Club 18,366, 488, 519home business schemes 345Homeland Security 119, 136home media center 299home office 230–231Honeywell 297Hopper, Grace Murray 90, 231,231–232, 515hospital information systems (HIS)299HotBits 399Hot Plug 63“hot spots” 58, 250, 250Howard, John H. 63HP (Hewlett-Packard) 16, 237, 258HTML (Hypertext MarkupLanguage) 232, 232–233. Seealso DHTML; XHTMLCGI and 80–81in document formatting 342for help systems 225for hypertext 233for Internet applicationsprogramming 249with Java 255with JavaScript 256for presentations 381Web browsers and 503in Web page design 507for World Wide Web 518XML and 520HTTP (HyperText TransferProtocol) 157–158, 233, 438,503, 508, 518Huffman coding 134human-computer symbiosis 139,277, 391human genome 46human mind, modeling 92–93Human Use of Human Beings, The(Wiener) 511HVAC, in smart buildings 434hybrid cars 71Hypercard 32, 99, 122, 233, 322hypermedia 233–234. See alsomultimediaHyperterminal 476hypertext 233–234Bush and 63in computer history 229Engelbart’s work on 182in help systems 225multimedia and 322for World Wide Web 43in World Wide Web 518II18n 246–247IAD (Internet addiction disorder)391IBM (International BusinessMachines) 235–236Amdahl at 10Apple and 258in computing history 227Deep Blue and 85FORTRAN developed at 202government funding of 212hafnium chips by 86Hollerith and 230IAS computer and 499Java and 255mainframes by 290, 290marketing of 106Mark I underwritten by 5McCarthy at 297in office automation 341optical hybrid chip by 356parallel interface by 360patents owned by 245popular culture and 378research of 404RPG at 412supercomputers of 462tape format of 467word processor and 516X10 at 324IBM/360 227, 235, 290, 290, 323IBM/370 235, 290IBM/390 290IBM MVS JCL 257IBM PC 236–237. See also PCclonesApple II and 18, 258boot sequence for 54–55bus in 62in computing history 228in education 99in IBM business 235introduction of 366keyboard of 265Macintosh and 287market entry of 106–107microprocessors in 304, 319monitor for 318operating system for 107,206, 305, 307, 321processors for 4, 218reverse engineering of 405standards and 457word processing on 516Ibuka, Masaru 445IC. See integrated circuitICANN (Internet Corporation forAssigned Names and Numbers)17, 158, 251ICCP (Institute for Certification ofComputing Professionals) 80Icon 83icons 247ICT (Information andCommunication Technologies)Task Force 251ICYou.com 368IDE (Integrated Drive Electronics)223Identification division 91identity fraud 238identity in the online world 17,124, 125, 237–238, 391, 482, 524identity theft 100, 238–239. Seealso computer crime; onlinefraud and scamsbiometrics and 49credit card use and 146data security and 137by hackers 220information collection in384Internet growth and 248phishing in 369, 370policy on 472risk and 408spyware in 453with viruses 111ideographs 82

566 IndexIDNA (Internationalizing DomainNames in Applications) 158IEC (International ElectrotechnicalCommission) 298IEEE Transactions on InformationTheory (Diffie and Hellman)146IETF (Internet Engineering TaskForce) 251if statements 55IGF (Internet Governance Forum)251IIOP (Internet Inter-ORB Protocol)118iLife 357I.Link 197Illustrator (Adobe) 4iMac 19, 258, 288image, bitmapped 50, 50, 81, 214image manipulation, as art 25image processing 110, 112, 204,239, 300. See also computergraphicsiMovie 493IMP 78impaired driving, monitoring 71imperative languages 203implementation 138, 154, 394, 444IMPs (Interface MessageProcessors) 266income, in digital divide 149incremental computing 463increment operation 65index file, in information retrieval240index register 119–120, 304index table 223India 143, 149, 209indirection 375–377Inducing Infringement ofCopyrights Act 445induction 190industrial robots 182–183,410–411industry 99. See also CAD/CAMinference engine 188, 188Information and CommunicationTechnologies (ICT) Task Force251information design 239–240“Information Flow in LargeCommunication Nets”(Kleinrock) 266information hiding 129, 460Information Processing TechnologyOffice (IPTO) 463information retrieval 240–241,273. See also search engineinformation science 46, 110information services, online. Seeonline servicesinformation systems auditing 31,130information systems degrees 171information theory 42, 241–242,427information transfer rate 38information warfare 100, 127, 220,242, 248, 311Information Week 260InfoTrac 349InfoWorld 260infrastructurein developing nations 143embedded systems in 178for enterprise computing 183in information warfare 242for Internet 87pyramid model of 291, 291for smart home 435society as 438inheritancein C# 67in cellular automata 75in classes 20, 88in data abstraction 129in object-orientedprogramming 67, 340in Simula 431Smalltalk and 434in-house applications 22in-house documentation 471Ink Development 343inkjet printer 380, 382inner identity 237In pointer 60input device. See graphics tablet;keyboard; mouseInput/Output (I/O) 242–243, 243in C 66in C++ 68in COBOL 91in computer engineering 101CPU and 304in flowcharts 200in mainframes 290microprocessor and 304in minicomputers 312in MS-DOS 321in operating systems 353in PL/I 373insertion, in list 282insertion sort 447–448installation of software 244instant messaging 11, 126, 198,217, 440, 477, 523Institute for Advanced Study 499Institute for Certification ofComputing Professionals (ICCP)80Institute for Electrical andElectronic Engineers (IEEE)79, 457Institute of Electrical andElectronics Engineers ComputerSociety 404instructionsaddressing 3in Analytical Engine 35in BINAC 167in cache 10, 69–70CPU processing of 304in machine code 28storage of 167instrumentation, scientific419–420integer 138, 338integrated circuit (IC). See alsoCPU; microprocessorin calculators 71in chipsets 86in computing history 227invention of 85in microcomputer 228Moore’s work with 318in supercomputers 461Sutherland’s work on 463Integrated Drive Electronics (IDE)223Intel Corporation 244–245AMD processors and 4Apple and 258chipset architecture of 86Grove at 218hafnium chips by 86in industry standardization237Macintosh and 288, 357microprocessors of 228, 304Moore at 318–319nanotechnology at 330in USB development 197intellectual property andcomputing 245–246censorship and 76centralization and 440digital rights managementand 149–150DVRs and 164file-sharing networks and193Google Book Search and167, 211hackers and 219ISPs and 252at MIT Media Lab 313policy on 472YouTube and 524intelligence, defining 26intelligence agencies 118–119, 136IntelliGenetics 190intelligent agents. See softwareagentsIntellipedia 119intentional programming 430Intentional Software 430InterCasino 346Interface Message Processors(IMPs) 266interfaces. See specific typesinterference 408interlaced display 318interlock mechanism 113intermediate language (IL) 67intermediate representation 96, 96International ElectrotechnicalCommission (IEC) 298internationalization andlocalization 158, 246–247Internationalizing Domain Namesin Applications (IDNA) 158International Space Station 430International StandardsOrganization (ISO) 457International TelecommunicationUnion (ITU) 251, 316Internet 247–249. See also WorldWide Webbandwidth on 38broadband for 57–59business use of 64centralization and 439–440computer-aided instructionover 99computer engineering and102in computer science 110in computer security 100in computing history 228,229data communications over133definition of 468digital divide of 148–149distance education over153–154DNS in 155employment in 178–179in groupware 217infrastructure for 87for journalism research 259legal theory on 274–275in libraries 276local area networks and 284multimedia on 322in office automation 342organization and governanceof 124, 250–251, 274–275,439, 494packet switching on 78, 133in popular culture 378portability and 95publications on 260risk and 408–409in science fiction 418–419in software marketing293–294TCP/IP and 468–469telecommunications and 473viruses spread by 100wiretapping and 119Internet addiction disorder (IAD)391Internet addresses 157–158Internet applications programming249–250Internet cafés 250, 250Internet Corporation for AssignedNames and Numbers (ICANN)17, 158, 251Internet Crime Complaint Center345Internet Engineering Task Force(IETF) 251Internet Explorer. See MicrosoftInternet ExplorerInternet Governance Forum (IGF)251Internet Inter-ORB Protocol (IIOP)118Internet Law Treatise 274Internet-only banks 39Internet radio 251Internet Relay Chat (IRC) 83, 442Internet security packages 197,505Internet service provider (ISP) 70,251–252, 332, 350–351, 451,503. See also America OnlineInternet tablet 466Internet telephony. See VoIPInternet Worm 111interpolation 371InterPress 379interpreter 252, 252–253in APL 18for BASIC 40Brief Code 297in LISP 281parsing by 360–361for Pascal 362for PostScript 379for Python 392for Ruby 413–414in scripting languages 421for Tcl 468interprocess communication 264interrupt-driven I/O 243, 243interrupt request (IRQ) 243, 243interstitial ads 344Intranet 229, 284, 292intrusion detection 102inventory 291investments 345, 348IP addresses 155, 158, 468, 469iPhone 19, 147, 258, 364, 437,466, 478iPod 19, 108, 154, 258, 326, 327,327–328, 375IP phone 496iptables 197IPTO (Information ProcessingTechnology Office) 463IPTV 69IP Version 6 158Iraq War 53, 198IRC (Internet Relay Chat) 83, 442iris scanning 48, 48iRobot Corporation 60, 253iRobot Create 253IRQ (interrupt request) 243, 243ISA (industry standardarchitecture) 62, 62, 237, 319,457

Index 567ISAM (Indexed Sequential AccessMethod) 192ISDN (integrated services digitalnetwork) 58, 299ISO (International StandardsOrganization) 457ISP (Internet service provider) 70,251–252, 332, 350–351, 451,503. See also America Online;satellite Internet serviceiterative software engineering 444ITU (InternationalTelecommunication Union) 251iTunes 19, 150, 258, 326, 327Iverson, Kenneth E. 18iWork 357JJabberwocky (chatterbot) 83Jackson, Steve 124–125Jacquard, Joseph-Marie 392Jansky, Karl 42Japan 108“Jaron’s World” 272Java 254, 254–256, 255applets in 19C++ and 68–69development of 461for financial calculators 195inheritance in 340for Internet applicationsprogramming 249interpreters for 253Joy and 261Microsoft and 206Microsoft .NET comparedto 307Microsoft Windowschallenged by 107multiprogramming in 324plug-ins 374pointers and 377portability of 95procedures in 385program libraries in 276pseudocode and 391for smart cards 436SQL and 455for virtual realityprogramming 496in Web browser 504XML and 520Java API for XML (JAX) 255JavaBeans 255JavaCard 436Java/RMI (Java/Remote MethodInvocation) 154–155JavaScript 256–257, 508in Ajax 6in DOM 161Java Server Pages (JSPs) 255Java Virtual Machine (JVM) 179,253, 255, 461JAX (Java API for XML) 255JCL (job control language) 97,257, 276J dialect 18Jennicam 504Jennings, Tom 61Jet Propulsion Laboratory (JPL) 78Jini 261JobCentral 348job control language (JCL) 97,257, 276job market 108, 171–172, 178–179,439Jobs, Steven Paul 18, 19, 150,257–259, 357, 519job searching and recruiting,online 348–349John Madden Football (game) 174join, in database 131Joint Photographic Experts Group(JPEG) 214–215, 372Jones, D.F. 418JotSpot 211journaling, in file systems 192journalismblogs in 52, 53, 125censorship of 76and computer industry260–261and computers 259–260multimedia and 322online research in 349podcasts in 375political activism and 377user-created content in 487World Wide Web in 518Joy, Bill 255, 261, 261–262joystick 489JPEG (Joint Photographic ExpertsGroup) 214–215, 372JScript 257, 508JScript.NET 257JSPs (Java Server Pages) 255Julia (chatterbot) 83, 442jurisdiction 123JVM (Java Virtual Machine) 179,253, 255, 461KKaczynski, Theodore 261Kahn, Robert 78Kana Unicode 82Kaphan, Shel 45Kapor, Mitch 124Kasparov, Garry 26, 85Katz, Phil 428Katz v. U.S. 383Kay, Alan 263–264, 433Kazaa 193Kelvin, Lord. See Thomson,WilliamKemeny, John G. 39Kepler, Johannes 70Kermit 194kernel 264in boot sequence 55for GNU 279, 456–457in Linux 279, 478in operating systemarchitecture 354in OS X 357in UNIX 353, 429, 485Kernighan, Brian W. 33kerning 201key 24, 131, 223, 224, 446–448. Seealso public key cryptographykeyboard 129, 185, 265, 265, 272,364key escrow 146, 181key exchange 146keyframes 16keyloggers 453Keynote (Apple) 381keystroke commands 489keywordscooperative assignmentof 117for information retrieval 241in online advertising 211,344in parsing 361in Pascal 362in search engines 422in Web filters 505Kiczales, Gregor 430Kilby, Jack 85Kildall, Gary 321kilobyte 51, 298Kimball, Lisa 407Kimsey, Jim 11Kindle 9, 166Kismet (robot) 27, 56, 411Kleinrock, Leonard 265–266Knopf, Jim 427knowledge, encoding 187knowledge base 188, 188, 470“knowledge engine” 418knowledge engineering 190knowledge principle 190knowledge representation 110,266–267, 369, 390, 442Knuth, Donald 267–268Korn, David 429Korn shell (Ksh) 429, 485Kowalski, Robert 390KR 110, 266–267, 369, 390, 442KRM (Kurzweil Reading Machine)268Kurtz, Thomas 39Kurzweil, Ray 268, 268–269, 325,355, 432–433, 452Kurzweil Reading Machine (KRM)268LL1 cache 70L2 cache 70L10n 246–247Laboratory for Computer Science141lagged-Fibonacci algorithm 399lambda calculus 87, 97LambdaMOO 494LAN. See local area networkLandau, Susan 146landers 449languages. See programminglanguageslanguage translation software270–271, 278–279, 330, 363Lanier, Jaron 271–272LAPACK 43laptop computers 272, 272–273batteries for 446data security on 137by Dell 140fingerprint readers on 49global market for 108“hot spots” and 250by IBM 237identity theft from 238keyboard for 265market entry of 107military use of 310operating system and 354PDAs and 364Larson, Earl Richard 30, 297laser 42, 74–75, 300, 356laser printer 379, 380, 382, 382LaserWriter (Apple) 379last in, first out (LIFO) 138, 456last mile 87latency 416LaTex 483law enforcement and computers 17,31, 49, 273, 345–346, 370law offices 273–274laws of robotics 418, 433layered architecture 59LCD (liquid crystal display) 199,199, 272, 318LCS (MIT Laboratory for ComputerScience) 141learning theory 284, 359LEFT SHIFT bitwise operator 52Legal Information Institute 274legal research 349legal software 273–274legal theory 274–275LEGO Logo 285, 411Leibniz, Gottfried Wilhelm 70, 294Leinster, Murray 418–419LEM (Lunar Excursion Module)449Lempel-Ziv compression 134Lenat, Douglas 27, 267, 351Lenovo 235Leonardo (robot) 56, 56–57Lerdorf, Rasmus 372Lerner, Sandy 87Lessig, Lawrence 123, 251,274–275Levy, David 85Levy, Steven 482lexical analysis 95, 96lexical binding 45LexisNexis 274, 349LexisOne 274Lexitron 516libraries, digital 166–167libraries and computing 275–276,349, 505library, program 276, 276–277. Seealso DLLsin Algol 7algorithms in 7for APIs 20in C++ 68in compiling 96–97for mathematics 296in Microsoft .NET 306in Microsoft Windows 20,309in object-orientedprogramming 341, 443in operating system 353for PHP 373procedures and functionsin 385for sequential calculators 5for VBScript 492Licklider, Joseph Carl Robnett277–278Life on the Screen (Turkle) 482lifetime, of variables 491LIFO (last in, first out) 138, 456lighting, in smart buildings 434light level, in graphics 106Lilith (workstation) 514Linden Lab 347–348linear search 448line noise 316line printers 381linguistics and computing 278–279, 330, 442LinkedIn 349, 440–441linking, in document model 160links. See hypertextLinksys 87Link trainer 311Linolex 516Linpack 43Linux 279, 279–280, 280. See alsoUNIXASP .NET on 1in computer industry trends108in computer market 107on Dell computers 140development of 456–457,477–478, 486device drivers in 145DRM on 149, 150DVR capability of 163–164emulators on 179files in 192firewall in 197on flash drive 198kernel in 264as media center 299Microsoft and 306, 309

568 Indexin open-source movement352personal informationmanagers for 368server version of 192shell in 429for smartphones 437software installation on 244updates under 244for workstations 517Lisa (computer) 258LISP 280–282applications of 204, 389development of 403in EMACS 387as functional language 204lambda calculus in 87Logo and 284McCarthy’s work on 297recursion in 401variables in 490, 491list 137–138list processing 282, 282–283in C# 67in computer science 109in insertion sort 447lambda calculus in 87LISP for 281in Logo 284in memory allocation 224queue for 396stack and 456trees for 479literacy 143, 149literals 115literature, hypertext used for 234lithography 85, 86Littman, Jonathan 314LiveScript 256load balancing 310loader program 54local area network (LAN) 283,283–284business use of 64in cluster computing 216in computer history 228data communications over133groupware and 217in office automation 342for SOHO market 230local buses 62–63localization 158, 246–247local search 423locational privacy 384Loebner Contest 84Lofgren, Eric 441logical comparisons 65logical operators 51logic bombs 111logic error 61Logic Named Joe, A (Leinster)418–419logic programming languages 338,389Logic Theorist 33, 190, 295logistics 310Logo 170, 282, 284–285, 359, 433Loislaw 274London, cholera outbreaks in 239long-distance education 153,153–154, 170, 322long integer 138, 338loop 285, 285–286in arrays 24in BASIC 40in C 65in COBOL 91in error handling 187in flowcharts 200in FORTRAN 202infinite 97in interpreters 252logical errors in 61in Perl 365in procedural languages 388recursion and 400in structured programming460lossless compression 92, 214lossy compression 92, 134, 214,372Lotus 1-2-3 366, 452Lotus Notes 217, 342LoudCloud 16Lovelace, Ada 2, 35, 36, 515LR parsing 267Lua 286Lucent Technologies 42Lunar Excursion Module (LEM)449Lunar X Prize 358Lycos 422LZW (lossless compression) 214Mmachine code 28–29, 45, 95, 388Machine Readable Cataloging(MARC) 275“Machine Stops, The” (Forster) 418machine translation (MT) 270Macintosh 18–19, 287–288, 288.See also Apple; iMacin computing history 228C on 66desktop publishing on 143device drivers in 144–145digital video on 493DVR capability of 163–164in education 99, 169embedding and 160emulators on 179floppy disks and 199graphics on 105, 322help systems in 225hypertext on 233Intel chips in 245introduction of 258, 524Jobs and 257–258laptops by 273market entry of 107market share of 306as media center 299microprocessors in 320, 357mouse and 320–321operating systems for 353,357. See also OS Xin personal computing 366personal informationmanagers for 368scripting in 422user documentation in 159user interface of 18, 228,258, 307, 488–489word processing on 516Mac-LISP 281macro 29, 111, 288–289, 453Macromedia 4Macromedia Director 381Macromedia DreamWeaver 4, 507Macromedia Flash 4, 20, 32, 374,507Macsyma 145Macy, Michael 441Made In America (Dertouzos) 141Maes, Pattie 289–290Magellan 293magenta, in CYMK 93magnetic ink character recognition(MICR) 39magnetic resonance imaging (MRI)300mailer demon 140mainframe 290, 290–291Amdahl and 10backup systems for 37batch processing in 257buses in 62in CAD 98compiling in 97in computing history 227employment and 179FORTRAN for 202IBM and 235I/O processing in 243marketing of 106memory in 467multiprocessing in 323in popular culture 378printers for 381professional programmersfor 386program libraries in 276RPG for 412SQL and 454Stallman’s work with 456statistical analysis with 458tape drives in 467user group for 488Y2K and 522maintenance 444makefile 388malware 451. See also spyware andadwaremanaged backup services 37“Management Game, The” 103management information system(MIS) 110, 171, 291, 291–292Mandelbrot, Benoit 203mantissa 338manuals 159, 471map information and navigationsystems 71, 209, 211, 229,292–293, 441MapQuest 292MARC (Machine ReadableCataloging) 275marker, in hypertext 234marketing 9, 11marketing applications 64marketing of software 107–108,293–294Markhoff, John 314Mark I 5, 61, 231, 498Mark II 5Mark III 5Mark IV 5markup languages 5–6, 161, 232–233, 256, 520. See also DHTML;HTML; XHTMLmarriage scams 345Mars Pathfinder 449Mars rovers 59, 410, 449, 450Martinian, Emin 49mashups 110, 211, 275, 292, 294,423masking 52Massachusetts Institute ofTechnology. See MITmassively multiplayer online roleplayinggames (MMORPGs) 347master boot record 55matchmaking, software agentsfor 289Mathematical Foundations ofQuantum Mechanics, The (vonNeumann) 498“Mathematical Theory ofCommunication, A” (Shannon)241, 427“Mathematical Theory ofCryptography, A” (Shannon)427mathematics 7, 110, 326, 443mathematics of computing294–295mathematics software 145,295–296, 338, 453, 458. See alsospreadsheetMatrix films 378, 419Matsumoto, Yakihiro 413Mauchly, John William 167, 184,226, 226, 296–297, 499Mauldin, Michael 83Mavica floppy disk 446Maxwell theory 420Mayo Clinic 367MBTF (mean time betweenfailures) 189MCA (Microchannel Architecture)62, 236, 457McCarthy, John 297–298in artificial intelligence 26Brooks and 59on chess 85on encoding knowledge 187LISP and 281Minsky and 313Shannon and 427McCorduck, Pamela 190McCulloch, Warren S. 336,510–511McGill Random Number GeneratorSuper-Duper 399MCSE (Microsoft Certified SystemEngineer) 80Mead, Carver 463Mead, Margaret 124mean time between failures(MBTF) 189measurement units used incomputing 298–299mechanical calculator 35–36, 70,226, 294mechanical computer 13–14, 14,226, 510. See also differentialanalyzermechanical integrator 13media center, home 299Media Studio Pro 493MediaWiki 116medical applications of computers299–301, 300of artificial intelligence 27bioinformatics 47haptic interfaces 222image processing 239inkjet technology and 382personal health informationmanagement 367–368robotics 183, 411for senior citizens 425smart ships 436virtual reality 496medical informatics 299–301medical research 349MEDLINE 350meeting management, ingroupware 217megabyte 51, 298megapixels 371Memex 63, 233memory 301–302. See also cache;heap; stackin Analytical Engine 35–36,226for arrays 24assembly languages and 29BASIC and 40bits in 50–51buffer in 60for cache 69–70capacitors in 30cells of 224

Index 569in chipset 86chips for 86, 218clock speed and 90in computer engineering 101CPU and 120, 304–305demons and 141for digital cameras 372in embedded systems 178,178for fonts 201fragmentation of 302for graphics cards 214for hard disks 223in heap 224in IBM PC 236by Intel 244interpreters and 252in I/O processing 242–243in laptops 272in mainframes 467microprocessor and 304in minicomputers 312on motherboard 319in MS-DOS 321–322in multiprocessing 323,323–324nanotechnology and 329in PDAs 364in personal computers 228program access to 137prosthetic 336punched cards and 392in recursion 401in smart cards 436sorting and 446for stored programs 227virtual 3, 224, 261, 302,308, 353von Neumann’s work on498Y2K and 522memory (human), in cognitivescience 92memory bus. See busmemory management 302–303addresses in 3allocation 302, 376deallocation 224early binding and 46kernel and 264in LISP 281in list processing 282in Microsoft Windows 308in operating systems 353pointers and 375–376stack for 456Menlo Park 403Mephisto 52mercury delay line 499mergesort 447–448message passing 113, 303, 308, 324Message Passing Interface (MPI)303, 324metacharacters 402, 403Meta-Dendral 190METAFONT 267Metal Oxide Semiconductor FieldEffect Transistor (MOSFET) 301metasearch engine 423, 423metatag 422metavariables 38method. See functionsmetric prefixes 298Metro chip 305Meyer, Bertrand 173MFC (Microsoft FoundationClasses) 20, 89, 309, 341MFLOPS 43Michelangelo virus 111MICR (magnetic ink characterrecognition) 39Microchannel Architecture (MCA)62, 236, 366, 457microchip. See chipmicrocode 227microcomputer. See also Altair;personal computerBASIC on 39–40buses in 62–63in computing history 228CPU for 304Forth on 201–202graphics on 213hacking 219IBM PC and 236I/O processing in 243marketing of 106publications on 260tape drives in 467user groups for 488word processing on 516Wozniak’s design for 258Microelectronics and ComputerTechnology Corporation 41microfilm, archiving with 276microkernel 264microlasers 356micropayment systems 146–147microprocessor 303, 303–305.See also CPU; multiprocessing;reduced instruction setcomputer (RISC)from Advanced MicroDevices 4in calculators 71in chipset 86clock speed and 90emulators and 179engineering of 101for graphics cards 214for IBM PC 236increasing complexity of401–402by Intel 218, 244, 318–319in Macintosh 19, 288, 357measurement units for 298in minicomputers 312Moore’s work with 318–319on motherboard 319by Motorola 320nanotechnology and 329in office automation 341–342in PC development 366in personal computers 228scripts and 421–422in smart cards 435–436speed of 90in supercomputers 461in synthesizers 325–326Microsoft Access 131, 132Microsoft Certified SystemEngineer (MCSE) 80Microsoft Corporation 305–306.See also Gates, William, III;MS-DOSantitrust case against 15,107, 206–207, 274, 306Bell at 42browser development by 15censorship in China and 76certification through 80in computer history 228founding of 206in industry standardization237Java and 255open source projects at 122RTF at 413Simonyi at 430smart card standard of 436software piracy and 445Yahoo! and 523Microsoft Excel 160, 452–453, 454Microsoft Exchange 217Microsoft Foundation Classes(MFC) 20, 89, 309, 341Microsoft FrontPage 505, 507Microsoft Internet Explorer503–504development of 305–306JavaScript in 256Netscape and 15–16plug-ins for 374Windows packaged with229, 306World Wide Web and 518Microsoft .NET 306–307ASP and 1C# and 67CORBA and 118for distributed computing154for distributed objectcomputing 89for Internet applicationsprogramming 249Java and 504network object model in160–161VBScript and 492Web servers and 508in Windows 309Microsoft NetMeeting 492Microsoft Network (MSN) 306, 351Microsoft Office 23competition for 306copy protection of 117–118development of 305document model used in 160dominance of 107for Macintosh 287macros in 289market for 293in office automation 342in personal computing 366Simonyi’s work on 430speech recognition in 452Microsoft Office Live 21Microsoft OneNote 221Microsoft Outlook 177, 342, 368Microsoft PowerPoint 380, 381Microsoft Project 390Microsoft Research 404Microsoft Surface 466, 478Microsoft Visual Basic 20, 40, 309,387, 388, 422, 491Microsoft Visual Basic .NET 492Microsoft Visual Studio .NET 388Microsoft Windows 307–310. Seealso Microsoft Windows VistaAPI of 20, 354Apple and 18–19backup software in 37competition against 107in computer history 228–229in computer market 107C on 66copy protection of 117–118demons in 141desktop publishing on 143development of 206, 305, 353device drivers in 144–145disabled users and 151DVR capability of 163–164dynamic link libraries in 20in education 99, 169emulator for 179files in 191–192graphics on 105, 214help systems in 225hypertext on 233Java dialect for 255keyboard for 265on laptops 273Macintosh and 107, 287–288mathematics software in 295Media Center in 299mouse and 321MS-DOS in 322multitasking in 324, 325objects in 340OS/2 and 236in personal computing 366personal informationmanagers for 368PL/I and 374Plug and Play in 374scheduling and prioritizationin 417scripting in 422server version of 192, 508shell in 428software installation under244for tablet PCs 466updates under 244user documentation in 159VBScript in 491–492wizards in 225word processing in 516for workstations 517Microsoft Windows 7 307–308Microsoft Windows CardSpace 307Microsoft WindowsCommunication Foundation307Microsoft Windows Explorer 308Microsoft Windows Live 351Microsoft Windows ManagementInstrumentation (WMI) 492Microsoft Windows Media Player327, 504Microsoft Windows Mobile 437Microsoft Windows NT 305–306,307Microsoft Windows PresentationFoundation 307Microsoft Windows Vista 307–309,308caching in 70firewall in 197help system in 225Media Center in 299memory in 198, 223, 301sales of 306security of 100, 111for tablet PCs 466Microsoft Windows WorkflowFoundation 307Microsoft Word 135, 143, 160, 192,403, 483, 516–517Microsoft Xbox 205, 206Microsoft Xbox 360 108, 205Microsoft Zune 327MicroWorlds Logo 285middleware 139, 310MIDI (musical instrument digitalinterface) 326, 448military applications of computers310–312ENIAC 167fractals in 203government funding and 212in history of computing 226IBM in 235image processing 239information warfare 242laptops 273Mauchly’s work with 296robotics 253, 410simulation 432virtual reality 271, 495–496MIME (Multipurpose Internet MailExtensions) 333

570 IndexMinard, Joseph 239mind 92–93, 313mind-mapping 441minicomputer 312, 312–313Bell’s work on 41buses in 62business use of 64complexity and 401–402in computing history 227graphics on 104mainframes and 290marketing of 106monitors for 317operating systems for 353,410, 485professional programmersof 386user group for 488minimax theorem 498minorities in computing 515–516Minority Report (film) 384Minsky, Marvin Lee 313in artificial intelligence 26,27, 162at Dartmouth Conference297Kurzweil and 268LISP and 281neural networks and336–337software agents and 442MIPS 43, 90, 517mirrored hard disk 37, 398MIS (management informationsystem) 110, 171, 291, 291–292MIT (Massachusetts Institute ofTechnology)Breazeal at 56Brooks at 59Bush at 63Dertouzos at 141Kleinrock at 266Kurzweil at 268Licklider at 277Maes at 289MIT Architecture Machine Group331MIT Artificial IntelligenceLaboratory 59, 289, 313, 336–337, 359, 403, 456MIT Laboratory for ComputerScience 141MIT Media Lab 289, 313–314, 314,331, 403, 484Mitnick, Kevin D. 220, 314–315MITS 206, 228, 304, 366, 519Mitsubishi Electric ResearchLaboratories 49ML language 204MLM (multi-level marketing) 345MMORPGs (massively multiplayeronline role-playing games) 347mobile computingbusiness use of 64in computing history 229data communications over134e-commerce and 169employment in 179handwriting recognitionfor 220at “hot spots” 250JavaScript and 256keyboards for 265paperless office and 383wireless 514mode 196modeling languages 74, 315modem 315–316bandwidth of 38, 298, 335in computer history 228for data communication 133in journalism 259for satellite Internet service416telecommunications and 473transfer speed of 299moderators 83, 114Modula-2 363, 514Modula-3 514modularization 460Mohr, Manfred 25molecular computing 42, 305,316–317molecular machines 314Mondrian, Piet 25money, digital 146–147Moneymaker, Chris 346money management software 195monitor 104–105, 142, 185, 236,272, 317, 317–318. See also flatpaneldisplayMono project 1, 67, 405monospace fonts 201Monster.com 348Monte Carlo simulations 399, 432Moog synthesizer 325Moondust (game) 271Moore, Charles H. 201Moore, Gordon E. 86, 218, 244,318–319Moore’s Law 86, 229, 304, 318MOOs (Muds, Object-Oriented)493Moravec, Hans 28, 59, 411More, Grinell 59Morita, Akio 445morphing 16morphology 270Morris, Robert, Jr. 111Mosaic 322, 503, 518Mosaic Web browser 15MOSFET (Metal OxideSemiconductor Field EffectTransistor) 301Moss, Frank 313motherboard 101, 319Motorola Corporation 320mouse 320, 320–321data acquisition with 129Dynabook and 263ergonomics of 185graphics tablet and 215invention of 182in Microsoft Windows 308user interface and 489movies 16, 104, 194–195MP3 format 448–449MP3 players 327, 327–328. Seealso iPodMPEG (Motion Picture ExpertGroup) 493MPI (Message Passing Interface)303, 324MPI-2 303MRI (magnetic resonance imaging)300MS-DOS 321–322API of 354compiling in 97C on 66demons in 141development of 353disabled users and 151files in 191help systems in 225hypertext on 233in IBM PC 107, 236, 307on laptops 273market entry of 107in Microsoft success 305in Microsoft Windows 307PL/I and 374regular expressions in 402shell for 428UNIX and 486MSDs (musculo-skeletal disorders)185MSN (Microsoft Network) 306, 351MT (machine translation) 270MUDs (Multi-User Dungeons) 104,125, 347, 407, 482, 493M.U.L.E. (game) 174multicore processor 305Multics 353, 409–410, 485multidimensional arrays 24multifunction peripherals 230, 417multi-level marketing (MLM) 345multimedia 322–323Adobe in 4broadband for 58–59codecs for 92in cyberbullying 126digital convergence in 147digital photography in 371in education 99floppy capacity and 74graphics in 106hard disk space for 223at home 299library access to 276in Microsoft Windows Vista307network and 335in presentations 381streaming of 458–459multiplayer games 174multiple inheritance 88multiple intelligence agents 92multiplexed transmission 133multiplexing 243multiprocessing 323, 323–324.See also dual-core processors;parallel processingin Ada 2Amdahl’s law of 10cache coherency in 70clock speed and 90in computer engineering 101in computer science 109in computing history 229in concurrent programming113Intel and 245microprocessors for 305in molecular computing 317multitasking compared to325object-oriented programmingand 341operating system and 354quantum processor and 395in real-time systems 400scheduling and prioritizationand 418Simula and 431in simulations 432in supercomputers 461multiprogramming 324, 353, 354Multipurpose Internet MailExtensions (MIME) 333multitasking 324–325, 325in computer science 109CPU and 113DLLs and 277document model and 160kernel and 264in Microsoft Windows 308operating system and 353preemptive 113scheduling and prioritizationof 417multithreading 305, 325multitouch 19, 364, 466, 478Multi-User Dungeons (MUDs) 104,125, 347, 407, 482, 493musculo-skeletal disorders (MSDs)185Muses 125music, computer 325–326,448–449musical instrument digitalinterface (MIDI) 326musical synthesizer 268–269, 325music and video distribution,online 326–327bandwidth and 38broadband for 58centralization and 440copy protection and 148,149–150in Internet growth 248by iTunes 150, 258media center and 299multimedia access and 322on MySpace 440real-time processing and 400streaming for 459music and video players, digital19, 108, 258, 327–328, 375, 437,445–446, 449Muslims, extremist 127mutual exclusion 151MYCIN 27MyLifeBits 42My Real Baby (robot) 253MySpace 237, 370, 377, 440–441,487, 494MySQL 132, 352, 455, 468, 511Mythical Man-Month, The (Brooks)386MythTV 299Nnames, in computing 154, 490name server 158namespaces 67Nannycam 504nanotechnology 42, 86, 305,329–330nanotubes 329–330nanowires 330Napier’s bones 70, 226Napoléon I, Russia invaded by239–240Napster 148, 150, 193, 326NAS 152, 192, 335NAT (Network AddressTranslation) 469, 469National Center forSupercomputing Applications(NCSA) 15, 212national ID card 436National Science Foundation (NSF)212National Security Agency (NSA)181, 383, 462National Tele-Immersion Initiative272natural language processing (NLP)27, 278, 330–331, 390, 404, 509natural selection, in geneticalgorithms 207nature, fractals in 203Naur, Peter 38navigation systems 71, 209, 211,229, 292–293, 441NCSA (National Center forSupercomputing Applications)15, 212negative feedback 510Negroponte, Nicholas 313–314,331Nelson, Theodore 233

Index 571nerds 378nested loops 286.NET. See Microsoft .NETNet, The (film) 378netiquette 331–332NetNanny 505net neutrality 44, 275, 332–333,472netnews and newsgroups 61,333–334. See also bulletin boardsystemson ARPANET 247in computing history 228conferencing systems and114cyberspace and 125Internet and 248, 518netiquette and 331–332Rheingold on 407as social networking 440Spafford’s work on 450spam on 451Netscape Corporation 14, 350,503, 518Netscape Navigator (NetscapeCommunicator) 15–16, 256,322, 352, 368, 374, 503Network Address Translation(NAT) 469, 469network administration 108, 178network cache 70networked storage 152, 192, 335network file system (NFS) 192,261, 335network layer 334Network News Transfer Protocol(NNTP) 333networks 334–335. See alsointranet; local area networkbandwidth of 38Cisco’s work in 87in computer engineering101, 102in computer history 228in computer science 110data communications over133decentralized 209in enterprise computing 183in fault tolerance 189file servers in 192file transfer protocols on193–194firewalls and 196–197floppy disk usage and 200in hacking 220hypertext on 233in Internet 468–469Kleinrock’s work on 266Licklider’s work in 278mainframes and 290mathematics in 295measurement units for 298Microsoft and 305–306with Microsoft Windows 307Mitnick and 314object-oriented programmingand 341in office automation 342operating system and 354packet-switched 78, 133,189, 265–266in popular culture 378in science fiction 418–419security of 450for simulations 432system administrators and464TCP/IP for 468–469telecommunications and 473in telecommuting 473–474viruses spread by 111for voting systems 175–176Weizenbaum’s work on 509network technicians 108Neumann, John von. See vonNeumann, JohnNeural Computing Center 403neural interfaces 335–336, 336neural network 27, 28, 336–337,337. See also perceptroncognitive science and 92computer science in 110connectionists on 93EPAM and 190for handwriting recognition220Minsky and 313Papert’s work in 359in pattern recognition 363risk and 409simulation and 432for speech recognition 452Wiener’s work on 510–511Neuromancer (Gibson) 125, 220,419neurons 336, 432neuroprosthetics 335–336, 336Neverwinter Nights (games) 347Newell, Allen 26, 93, 162, 190, 295New Kind of Science, A (Wolfram)76Newmark, Craig 120news cycle 259newsfeed 333news servers 333New Technology File System(NTFS) 191–192Newton (Apple) 220–221, 364Nextlink 58NextStep 258NFS (network file system) 192,261, 335Nigerion money scheme 345Ning 16Nintendo 205Nintendo 64 205Nintendo Wii 205, 221NLP (natural language processing)27, 278, 330–331, 390, 404, 509NLS/Augment 212, 233NNTP (Network News TransferProtocol) 333nodesof ARPANET 266in distributed computing154in hypertext 234in LISP 281in lists 282, 282in multiprocessing 323in networks 133in trees 479, 479Nokia N810 466Noll, A. Michael 25nondeterministic polynomial 98nonprocedural languages 337–338,389nonvolatile memory 178noosphere 369normalization 131, 338Norman (robot) 59notebook computers. See laptopcomputersNotepad 476, 517note-taking 441NOT operator 54Novell Linux 279Novell Netware 80, 228, 284Noyce, Robert 85, 218, 244, 318NSA (National Security Agency)181, 383, 462NSF (National Science Foundation)212NSFnet 247NTFS (New Technology FileSystem) 191–192nuclear magnetic resonance (NMR)technology 395–396nuclear reactions, simulating 432number theory 295numerical analysis 296numeric data 110, 138, 338, 341Nupedia 500Nvidia GeForce 8800 305Nygaard, Kristen 431OObama, Barack 377, 524Oberon 363, 514object(s) 88in C++ 459–460data abstraction and 129database components as 132design patterns and 142in distributed computing 154interoperability of 118in Java 254–255in Microsoft Windows308–309in object-orientedprogramming 340in PHP 373in Ruby 413in simulation 431object-based media 314Object Linking and Embedding(OLE) 160, 309, 517Object Management Group (OMG)118object-oriented database model132, 183object-oriented programming(OOP) 339–341, 340, 388binding and 45–46in C# 67in C++ 67–69, 460classes in 88COBOL and 91in computer history 228in computer science 109data abstraction in 129data structures in 138for expert systems 188flowcharting and 200Forth and 201in FORTRAN 202in JavaScript 256Kay’s work on 263message passing in 303at Microsoft 430with Microsoft .NET 306–607in Microsoft Windows 309operators defined in 355with Perl 365with PHP 372procedures in 385in Ruby 413Simonyi’s work in 430in Simula 431for simulation 432in Smalltalk 433software agents and 442in software engineering73–74, 443SQL and 455strings in 82UML for 315variables in 491Wirth on 514object query language (OQL) 455Object Request Broker (ORB) 118,310OCLC (On-line College LibraryCenter) 275OCR (optical characterrecognition) 268, 342, 355–356,417OCX (OLE controls) 309odd parity 186office automation 341–342office suites. See application suiteoffshoring 209Ogg 449Oikarinen, Jarkko 83OLAP (Online AnalyticalProcessing) 139OLE (Object Linking andEmbedding) 160, 309, 517Olmstead v. U.S. 383Olsen, Kenneth 41OMG (Object Management Group)118Omidyar, Pierre 165, 184, 342–344, 343Omidyar Network 343–344Omnifont 268“On Computable Numbers”(Turing) 481One Laptop Per Child 108, 109,144, 149, 314, 331OneNote 221online advertising 116, 123, 210–211, 212, 344–345, 358, 441Online Analytical Processing(OLAP) 139online auctions 31, 100, 120, 343.See also eBayonline backup services 37online banking 39online chat. See chat, onlineOn-line College Library Center(OCLC) 275online fraud and scams 100, 344,345–346, 349, 472. See alsoidentity theftonline gambling 346–347online games 347–348. See alsoonline gamblingon AOL 11broadband for 59chatterbots in 442cyberlaw and 124for distance education 154identity used in 237Internet cafés for 250multimedia in 322in popular culture 378popularity of 104pseudonymity in 17simulation in 432social sciences and 441–442user-created content in 487online investing 348online job searching and recruiting348–349online music and videodistribution. See music andvideo distribution, onlineonline relationships 237online research 259, 274, 349–350,377, 422–423, 441, 518online services 350–351bulletin boards and 61–62chat on 83cyberspace and 125e-mail on 177in hacking 220instant messaging on 477Internet development and247maps used in 292for research 349Web pages provided by 505

572 IndexOnStar 71ontologies and data models 267,351, 369, 424OOP. See object-orientedprogrammingOpenBSD 486Open Card 436OpenDoc 160Open Document standard 160OpenGL 105, 214Open Handset Alliance 437OpenMP 324Open Office 21, 309, 381, 405, 483OpenRide 12OpenSocial 441OpenSolaris 486open-source movement 352in computer industry trends108Cunningham in 122database alternatives from132in digital rights management150employment in 179in globalization 209hacking in 220IBM in 235Licklider in 278Linux in 279–280at Microsoft 122Microsoft and 306, 309Netscape Navigator in 16phone software and 437plug-ins in 375reverse engineering in 405Ruby in 414shareware and 428Stallman in 457Torvalds in 478UNIX in 261, 410, 486user-created content in 487voting systems and 176open system interconnection (OSI)334OpenType fonts 3Opera 504operands 354operating system 352–354, 353.See also Linux; Macintosh;Microsoft Windows; UNIXfor Altair 206APIs of 20, 20for Apple 519backup of 37BIOS and 49in boot sequence 55compromising 137in computer engineering 102in computer science 110CPU and 119–120data security in 137demons in 141device drivers and 144–145DLLs in 277for embedded systems 178entrepreneurship in 184ergonomics of 185error handling in 186files in 191–192as finite-state machine 196on flash drive 198fonts in 200hard disk and 222–223Java and 255kernel of. See kernelfor laptops 272marketing of 107mathematics software in 295memory management by 302message passing in 303multiprocessing under 324multitasking in 324–325networks and 334new 145for PDAs 364in personal computers 228portability and 95program-level security under137queues in 396in real-time processing 400scheduling and prioritizationby 417scripts and 421Smalltalk and 434system administrators and464systems programmer and464–465for time-sharing 219Trojan horses in 100virtual machine for 494virtual memory in 224operation(s) 28, 51–52, 54, 137operational amplifier 14operational analysis 139, 291–292operators 65, 68, 341, 354–355,355, 490. See also BooleanoperatorsOpportunity rover 449Opsware 16optical character recognition(OCR) 268, 342, 355–356, 417optical computing 42, 356optical lithography 86optical mouse 321optical scanning, for votingsystems 175–176optimization 95, 96, 115OQL (object query language) 455Oracle 80, 132, 415Oracle Corporation 356–357Oracle Information Architecture356Oracle on Demand 356ORB (Object Request Broker) 310Ordnance Engineering Corporation30organizations, theory of 139OrganizedWisdom 367OR operator 51, 54OS/2 236, 305, 307, 374Osborne 1 273OSI (open system interconnection)334OSI MHS (Message HandlingSystem) 177OS X 19, 258, 288, 357, 437, 486Ousterhout, John K. 468outer identity 237outline fonts 201Out pointer 60outsourcing 209, 470. See alsoglobalization and the computerindustryoverclocking 90overloading 67, 68, 340–341OWL (Web Ontology Language)20, 267Oxygen 141PP2P networks. See file-sharing andP2P networksP-159/A (Mohr) 25packages 2, 244PackBot (robot) 253packet, in Ethernet network 283packet-sniffing 100, 250packet-switched network 78, 133,189, 265–266Pac-Man 104Page, Larry 57, 210, 358–359Pagemaker 4, 18, 143, 287, 307PageRank algorithm 57, 210, 211,423, 480Painter’s Algorithm 106palettes, color 93–94, 94Palm, handwriting recognitionon 220Palm Pilot 364Palm Treo 364Panama 523paperless office 216, 342, 382paperless statements 39Papert, Seymour 109, 170, 282,284, 313, 359, 359–360, 483paradox, in Halting problem 97parallel ATA (PATA) 223parallel port 360, 425, 457, 486parallel processing 5, 10, 121–122,204, 263, 285, 389, 461. See alsomultiprocessingParallel Virtual Machine (PVM)217parameters 385PARC. See Xerox PARC laboratoryParis in the Twentieth Century(Verne) 418parity 186, 186Parry (chatterbot) 83parsing 360–362, 361in compiling 95, 96, 96in computer vision 112Knuth’s work in 267recursion in 401of scripts 421PAS (Publicly AvailableSpecifications) 457Pascal 362–363BASIC and 40branching statements in 55classes and 88in computer history 228enumerations in 184–185interpreters for 252–253PL/I and 373procedures in 385recursion in 401sets in 185variables in 491Wirth’s work on 514Pascal, Blaise 70, 226, 294passing by reference 385passing by value 385passive matrix display 199passive RFID 405PATA (parallel ATA) 223patches 111patent, for ENIAC 297Patent Reform Act 245patent system 245, 472patent trollers 245Paterson, Tim 321Patient Safety Institute 300PATRIOT Act 383pattern language 142Pattern Language, A (Alexander)142pattern matching 33–34, 402, 485pattern recognition 112, 363–364in counterterrorism 119in data mining 136fuzzy logic in 204in handwriting recognition220, 221for information retrieval241Kurzweil’s work in 268in law enforcement 273Paul, Ron 377PayPal 146–147payroll software 64PC. See personal computerPC AT 236, 265PCB (printed circuit board) 85PC clones 107, 228, 236, 304, 366,405PC-DOS 321PC-File 427PCI (peripheral componentinterconnect) 63, 86, 237, 319PC Magazine 260p-code 362, 391PCR (polymerase chain reaction)316PC/SC standard 436PC’s Limited 140PC-Talk 427PC-Write 428PCX 215PC-XT 236PDA (personal digital assistant)364, 437. See also mobilecomputingin computing history 229GPS in 293“hot spots” and 250keyboards and 265music playback on 327in office automation 342operating system and 354PC market and 367personal informationmanagers on 368smartphones and 108, 437texting on 477touchscreens on 478PDF (portable document format)364–365in desktop publishing 143for e-books 166in office automation 342PostScript and 380success of 3for technical manuals 471for user documentation 159PDP Assembly 65PDP minicomputer 41, 106, 227,312, 485PEAR (PHP Extension andApplication Repository) 373pedophiles, chat rooms and 83PEEK 40peephole optimization 96peering arrangements 332peer network 513pen, with graphics tablet 215pen computing 343Pentium microprocessor 4, 218,244, 304, 305perception 92, 112, 162perceptron 313, 336–337, 359Perceptrons (Papert and Minsky)359peripheral hardware 49–50, 54,101, 140, 230, 374Perl (Practical Extraction andRepot Language) 24, 83, 365–366, 393, 508permission status 136–137Perot, H. Ross 293perpendicular hard disk 223persistent cookies 116personal ads 120personal computer (PC) 366–367.See also laptop computers;microcomputerbackup for 37BASIC used on 40BIOS in 49bus in 62in CAD 98

Index 573in client-server computing89computer-aided instructionon 99in computing history 228in data acquisition 130by Dell 140in desktop publishing 142as DVR 163–164entrepreneurship in 184file servers and 192fingerprint readers on 49graphics on 105, 213–214,322help systems for 225in home office 230Kay and 263Linux offered for 306mainframes and 290marketing of 106–107McCarthy and 297as media center 299microprocessors in 304minicomputer and 312motherboard in 319, 319in office automation 342operating systems for 353podcasts on 375in popular culture 378professional programmersof 386publications on 260RISC processors in 402sales of 108software marketed for 293standards for 457statistical analysis with 458tablet 221, 466as terminal 476UNIX and 486user groups for 488user interfaces for 488–489virtual memory in 302in wireless network 513personal data management 42personal digital assistant. See PDApersonal finance software 39personal health informationmanagement 300–301, 367–368, 436personal information manager(PIM) 368–369, 389, 437, 466personal robots 314PERT (Program Evaluation andReview Technique) 389Pet 228PET (positron emissiontomography) 300PGP (Pretty Good Privacy) 181,383pharming 370phenomenology 162philosophical and spiritual aspectsof computing 28, 148, 237, 369phishing and spoofing 369–371anonymity of 17banks and 39in e-commerce 168fraud from 345by hackers 220identity theft from 238information collection from384in information warfare 242Internet growth and 248spam and 451viruses spread by 111phoneme 452phone phreaks 314Phong shading 106phosphors 105photography, digital 239, 275, 371,371–372, 382. See also digitalcameras; video editing, digital;Web camphotonic crystal 191Photoshopart and 25, 25in desktop publishing 143for image processing 4, 239on Macintosh 287memory for 301for photo editing 372plug-ins for 374photosites 371photovoltaic cells 42PHP 372–373PHP Extension and ApplicationRepository (PEAR) 373physical layer 334Physical Symbol System Hypothesis93Piaget, Jean 284, 359Picospan 114picture frames, electronic 484PIM (personal informationmanager) 368–369, 389, 437,466Pinball Construction Set (game)174pipelining 101, 305, 402pipes, in software engineering 73piracy. See software piracy andcounterfeitingPitts, Walter 336, 510–511pivot 447Pixar 258pixelsin bitmaps 50, 214in CRTs 317, 318in digital photography 371in GIFs 214in graphics 105, 214in LCD displays 199PKZip 428plain old telephone service (POTS)162, 473Plan 9 410Plankalkül 526PLATO (Programmed Logic forAutomatic Teaching Operations)99, 114, 153, 169, 322, 347Plato Notes 114platters, in hard disks 222, 222PlayStation 446PlayStation 2 205PlayStation 3 108, 205, 305, 462PL/I 373–374Plug and Play (PnP) 50, 63, 144–145, 244, 374, 487plug-in 19–20, 79, 374–375, 459,493, 504, 518P-machine 252–253podcasting 19, 251, 375pointers 375–377, 376addressing and 3in Algol 7in arrays 24in binary trees 479in buffering 60in C 65in C# 67Java and 255in list processing 282logical errors in 61in memory allocation 224in procedures 385in queues 396, 396–397variables and 490pointing devices 185POKE 40poker, online 346political activism and the Internet377–378democracy and 439flash and smart mobs 198journalism and 259–260Lessig and 275podcasts 375user-created content in 487YouTube and 524political policy 472polling 243poll-taking 441pollution 216polymerase chain reaction (PCR)316polymorphism 45–46, 340–341polynomial period of time 98Pong (game) 205pooled buffer 60popular culture and computing378–379, 418–419, 496pop-under ads 344pop-up ads 344pornography 76, 193, 505, 523port 303portability 94–95, 135, 465portable computers. See also laptopcomputers; mobile computing;PDA; smartphoneglobal market for 108handwriting recognitionfor 220“hot spots” and 250identity theft from 238market entry of 107medical use of 300military use of 310Web browsers on 504wireless access for 514portable document format. See PDFportal 350, 379, 422, 523Portland Pattern Repository 122port numbers 469port scanning 196positive feedback 510positron emission tomography(PET) 300POSIX 429POST (power-on self test) 49, 54postal mail 177POS terminal 89postfix notation 201PostScript 3, 180, 201, 202, 214,364, 379–380poststructuralism 482posttraumatic stress disorder(PTSD) 311POTS (plain old telephone service)162, 473, 496PowerBook 18, 273PowerPC chip 245, 288, 320precedence, of operators 355Predator 311predicate calculus 266predictability, fractals and 203preemptive multitasking 113,324–325Premiere 493Premiere (Adobe) 493preprocessor directives 66presentation layer 334presentation software 32, 64, 380,380–381, 492. See also MicrosoftPowerPointpresidential election 175, 227, 296,392, 438pressure, haptic interfaces and 221pressure gauges 129Pretty Good Privacy (PGP) 181,383Primavera Project Planner 390primitives 18printed circuit board (PCB) 85printers 381, 381–383. See also dotmatrixprinters; inkjet printer;laser printerBraille from 151in desktop publishing 142device driver for 144for digital photos 372parallel port for 360PostScript for 379–380for SOHO market 230standard for 457toner cartridges for 216print journalism 259–260print spooler demon 140, 396prior art 245prioritization 389, 417–418privacy in the digital age 383–384advocacy groups for 125anonymity and 17avatars and 237–238banking and 39biometrics and 49centralization and 440Clipper Chip and 146computer crime and 101cookies and 116counterterrorism and 119in CRM 123data mining and 136e-commerce and 168e-government and 173encryption and 181Google Earth and 211,292–293Google Maps and 423Internet growth and 248ISPs and 252law enforcement and 273medical information and 300network PCs and 367online advertising and 345online backup servicesand 37policy on 472RFID and 406risk and 408smart cards and 436social networking and 441ubiquitous computing and484user-created content and487Privacy in the Information Age(Cate) 383Privacy on the Line (Diffie andLandau) 146private class variables 88private key cryptography 146,180–181, 181probability 40–41, 241, 270, 296,389probes, in space exploration 449problem solving, design patternsin 142Probst, Larry 174procedural languages 138, 282,337, 388. See also C (language)Procedure division 91procedures 384–385in Algol 7in BASIC 40, 88in classes 88in COBOL 91in computer science 109,110encapsulation and 180in Logo 284–285macros and 288–289in mathematics software 296

574 Indexin object-orientedprogramming 340–341,388in Pascal 88, 362in Plankalkül 526programming languagesand 388in scripting languages 421in Simula 431in SQL 455stack and 456in structured programming443, 460process control 264processes 151, 154, 186, 264process management 353processor. See CPU; microprocessorProdigy 350production applications 64. Seealso CAD/CAMproduction systems, in artificialintelligence 26–27professional organizations 79profiles, Bluetooth 53profiling, cookies in 116program(s)addressing in 3applications. See applicationsoftwarefor batch processing 257code clarity in 158commenting in 158concurrent 112–113CPU and 120data security in 137demons 140–141as finite-state machine 196firewalls and 197global flags in 197–198internationalization of 247libraries for. See library,programlocalization of 247scripts and 421in Smalltalk 434in software engineering 444stored 227for supercomputers 461testing 394as trade secrets 245–246undecidable 97program code, documentationof 74, 158–159. See alsodocumentation; technicalwritingprogram code modules 73–74, 135Program Evaluation and ReviewTechnique (PERT) 389program library. See library,programprogrammable calculator 71programmable read-only memory(PROM) 49, 301programming. See also automaticprogramming; concurrentprogramming; object-orientedprogramming; structuredprogramming; systemsprogrammingbenchmarks in 43bugs in 61in data integrity 130of Differential Analyzer 426employment in 385–387of Internet applications 249libraries for. See library,programin Microsoft Windows308–309as profession 385–387pseudocode for 390–391for supercomputers 461systems analyst and 464in text editor 476of UNIVAC 296–297programming environment 387,387–388CASE tools in 73compilers in 253current use of 389documentation tools in 159for games 104interpreters in 253for Microsoft Windows 309for OS X 357professional programmersand 386punched cards and 392for Ruby 414Smalltalk as 434in software engineering 443programming languages 388, 388–389. See also specific languagesin ASP .NET 1assembly language and 29Backus-Naur Form for 38binding and 45compatibility and 94compilers for 95in computing history 227,228for concurrent programming113data in 128data structures in 138for embedded systems 178graphics and 105lambda calculus in 87linguistics in 278for multiprocessing 324open-source 352operator precedence in 355parsing 360–361scripting and 421string-oriented 82–83variables in 490–491Project Gutenberg 167project management software 342,389–390, 418, 444Project Oxygen 484Prolog 389, 390PROM (programmable read-onlymemory) 49, 301PROMIS 140propaganda 126–127, 242propagation 131proportional fonts 201propositional calculus 53–54prostheses 335–336, 336, 411protected class variables 88protein folding 46–47, 117Proteins@home 117protein simulation 47, 47protocols 154, 157–158, 177, 360,469, 513. See also file transferprotocols; TCP/IP; VoIPproxy address 197pruning strategy 84–85PS/2 236, 366pseudocode 73, 362, 390–391, 460pseudonymity 17psychoacoustics 449psychology of computing 237, 391,482–483psychotherapy, ELIZA and 83, 509PTSD (posttraumatic stressdisorder) 311public key cryptography 32, 78–79,79, 145–146, 180–181, 181Publicly Available Specifications(PAS) 457public variables 88, 491puck, with graphics tablet 215punched cards and paper tape 392in Analytical Engine 35, 226automatic tabulation of229–230commenting in 158in ENIAC 488in mainframes 290in voting systems 175PVM (Parallel Virtual Machine)217Python 392–393, 508QQDOS 321Qpass 146quad-core processors 4, 245quadriplegia 151quality assurance, software 61,109, 186, 394–395, 408, 444,464Quality of Life Technologies Center424–425Quantum Computer Services 11quantum computing 181, 329,395–396Quantum Random Bit GeneratorService 399QuarkXPress 4qubit 395queries 131, 139, 337, 455queue 396, 396–397in circular buffer 60in computer science 109as data structure 138in multitasking 325for scheduling andprioritization 417stack and 456Quick BASIC 40QuickBooks 195Quicken 39, 195quicksort 447, 447QuickTime 374quote marks, in search engines 423QWERTY keyboard 185Rrace 149, 515–516race condition 113Racter (chatterbot) 83radiation, from monitors 185radio astronomy 42radio frequency identification(RFID) 384, 405–407, 406, 436radio interference 408Radio Shack 228radix 338RAID (redundant array ofinexpensive disks) 398,398–399for data backup 37in disaster planning andrecovery 152fault tolerance with 189as file server 192hard disks for 223for networked storage 335virtualization and 494Rainbow Six (game) 311RAM (random access memory) 3,3, 301, 304. See also memoryRAND Corporation 162. See alsoSperry-Rand Corporationrandom access 192random access memory (RAM) 3,3, 301, 304. See also memoryrandomization, in qualityassurance 395random number generation 295,399range, in DAQ performance 130rape, virtual 125, 494Rapid Selector 63raster data 208Raster Image Processor (RIP) 379RateMDs.com 367–368rationalism 162RCA MKI 325RCA MKII 325RDF (Resource DescriptionFormat) 424RDF Site Summary 413read attribute 191readme 244Read-Only Memory (ROM) 301,304ReadyBoost 70, 198reality, nature of 369, 378,482–483Really Simple Syndication (RSS)375, 412–413RealPlayer 327, 374, 428, 504real-time games 104real-time processing 2, 399–400real-time simulations (RTS) 104,311reasoning, in cognitive science 92record data type 138Recording Industry Association ofAmerica (RIAA) 125, 150, 246record-level security 137recruitment, of terrorists 126–127recursion 400, 400–401in Algol 7in FORTRAN 202lambda calculus in 87in LISP 281in Logo 359in mergesort 447in quicksort 447Ritchie and 409in shellsort 447trees and 479recycling of computers 140red, in RGB 93Red Hat 279, 352reduced instruction set computer(RISC) 261, 288, 305, 320,401–402redundancy 39, 247, 427redundant array of inexpensivedisks. See RAIDrefactoring 74reference counter 224referential integrity 130, 131referral network, of Amazon.com 9refraction 190–191registers 28, 304regression analysis 136, 458regular expression 402–403, 485relational database model 131–132,139, 292, 455. See also databasemanagement systemsrelations 455relationships, online 237relevance, in information retrieval241reliability 36, 39, 130–131religion, extremist 127Remington-Rand UNIVAC 90, 296remote backup services 37remote procedure call (RPC) 154,309, 438, 509Reno, ACLU v. 125repetitive stress injuries (RSIs)185, 265Replay TV 163Report Program Generator (RPG)412repository 116. See also datawarehouse

Index 575Representational State Transfer(REST) 509reputation systems 480–481research, online. See onlineresearchresearch laboratories in computing403–404. See also specificlaboratoriesResearch Library InformationNetwork (RLIN) 275resistive touchscreen 478resource consumption, ofcomputers 216resource data type 373Resource Description Format(RDF) 424resource lock 113resource management 151, 389REST (Representational StateTransfer) 509retina scanning 48retirement planning 195reverse engineering 4, 404–405Reynolds, Craig 28RFID (radio frequencyidentification) 384, 405–407,406, 436RGB 93, 371Rhapsody 326Rheingold, Howard 198, 407–408,493Rheingold Associates 407RIAA (Recording IndustryAssociation of America) 125,150, 246Rich Text Format (RTF) 135, 413RIGHT SHIFT bitwise operator 52Riley, Bridget 25RIM BlackBerry 220, 364, 437Ringley, Jennifer 504RIP (Raster Image Processor) 379RISC (reduced instruction setcomputer) 261, 288, 305, 320,401–402Rise of the Expert Company, The(Feigenbaum) 190risks of computing 408–409, 438Ritchie, Dennis 65, 409, 409–410,429, 485River, The 114Rivest, Ron 146, 181RLE (run-length encoding) 214RLIN (Research LibraryInformation Network) 275Roadrunner 462Roberts, Lawrence G. 145, 266RoboHelp 225robotics 410–412academic credentials for 79artificial intelligence in 27in artificial life 28artificial limbs and 335–336in assistive technologies 425Breazeal’s work in 56–57Brooks’s work in 59–60in CAM 98computer science in 110computer vision in 112cybernetics in 124finite state machines in 196frames used in 313genetic algorithms in 208haptic interfaces in 222industrial use of 182–183in law enforcement 273“laws” of 418, 433layered architecture for 59military use of 311Minsky’s work in 313natural language processingin 330neural networks in 337personal robots 314research institutions in 403risk and 408in science fiction 418social impact of 439in space exploration 449for telepresence 474–475Robotics in Practice (Engelberger)183Robotics in Service (Engelberger)183Robot Wars 410Rock, Andrew 318Rockefeller Differential Analyzer(RDA2) 63RoCo (robot) 57role-playing games 104, 237, 347Rollins, Kevin B. 140ROM (Read-Only Memory) 301Roomba (robot) 60, 253root, of tree 138rootkit 150, 446root status 136Rosenblatt, Frank 313, 336Rosenbleuth, Arturo 510–511routers 87, 197routines 45, 49, 197–198, 200,207, 296royalties, for Internet radio 251RPC (remote procedure call) 154,309, 438, 509RPG (Report Program Generator)412R. R. Donnelly 292RSA algorithm 146, 181RSIs (repetitive stress injuries)185, 265RSS (Really Simple Syndication)375, 412–413RTF (Rich Text Format) 135, 413RTS (real-time simulations) 104,311Ruby 413–414Ruby on Rails 414ruggedized laptops 273rules 188, 204, 270, 271run-length encoding (RLE) 214run-time errors 186R.U.R. (Čapek) 410, 418Rural Free Delivery 153SSABRE 404SAC (Strategic Air Command) 311Safari 504SAGE (Strategic Air GroundEnvironment) 104, 139, 212,235, 311SageTV 299SAIL (Stanford ArtificialIntelligence Laboratory) 59,145, 403sales applications 64Salesforce.com 21salon.com 259SAM (software asset management)244Samba 405sampling, in computer vision 112sampling rate 130, 399–400SAN (storage area network) 192,335sandbox 255Sanger, Larry 500sans serif fonts 201SAP 293, 415–416, 462SAP Business ByDesign 415SATA (serial IDE) 223satellite communications network320satellite Internet service 58, 416SAX (Simple API for SML) 161Scalia, Antonin 274scams, online 100, 344, 345–346,349, 472. See also identity theftscanner 12–13, 48, 268, 342, 355,416–417scheduling and prioritization 389,417–418schema. See framesScheme 281Schickard, Wilhelm 70Schmidt, Eric 358Schmitt, William 297Schockley Semiconductor Labs 318Scholastic Aptitude Test (SAT) 71school shootings 126science fiction and computing 220,335, 410, 411, 418–419Scientific Atlanta 87scientific computing applications27, 110, 130, 136, 419–421, 420,431–432. See also FORTRANscientific instrumentation 419–420scientific modeling 106. See alsosimulationScooba (robot) 253scope, of variables 491Scottrade 348screen savers 203scripting languages 421–422.See also awk; JavaScript; Lua;Perl; PHP; Python; Ruby; Tcl;VBScriptfor administrative tasks 464in Ajax 5–6applets and 19in ASP 1in authoring systems 32for CGI 80–81computer science in 110for database development132with DHTML 233in DOM 161for Internet applicationsprogramming 249Java and 256regular expressions in 402in shell 428, 429–430in software installation 244in text editor 476in UNIX 485–486Web servers and 508scriptwriting 194SCSI (Small Computer SystemsInterface) 63, 197, 223, 335Sculley, John 258SDRAM (synchronous DRAM) 301search engine 422–424, 423.See also Google; informationretrievalAjax pages and 6Boolean operators in 54in computing history 229in cyberstalking 126for information retrieval241, 241in Internet growth 248knowledge representationin 267Microsoft research in 306natural language processingin 330in online advertising 344for online research 350portals and 379Semantic web and 424searching 109, 240–241, 401, 402,446–448“Search Inside the Book” 9Searle, John 93Seattle Computer Products 321Second Life 347, 347–348as computer game 104cyberlaw and 124distance education in 154study of 391, 441–442virtual community of 494Second Self, The (Turkle) 482sector interleaving 222sectors 222Secure Digital (SD) memory card198secure shell (ssh) 248Secure Sockets Layer (SSL) 79, 503security 100–101. See alsocomputer crime; data securityauditing and 31banking and 39buffer overflows and 60cable modems and 69cookies and 116of credit card transactions146digital certificates and 78–79in e-commerce 168e-mail and 177employment in 178, 179forensics in 102–103in information warfare 242Internet growth and 248JavaScript and 256of mainframes 290–291in Microsoft Windows 309in military systems 311Mitnick and 314NAT and 469networks and 334, 450in operating systems 354outsourcing of 108risk and 408system administrators and464telnet and 248of voting systems 176of Web servers 508on wireless networks 513security patches 111sed 365seed 399Sega 205SEI (Software EngineeringInstitute) 444selection sort 446–447selection statements. See branchingstatementsSelectric typewriter 516self 369self-replicating computers 329semantic analysis 96, 96semantics 270semantic Web 424Berners-Lee and 44in counterterrorism 118for information retrieval 241knowledge representationin 267ontologies in 351, 369technological singularityand 433Web 2.0 and 503semaphore 113, 151semiconductors 85, 318semipassive RFID 405sendmail 60, 111, 177senior citizens and computing424–425, 434sensors 178, 178, 208, 496September 11, 2001, attacks 53,383, 439sequential access 192

576 Indexsequential calculator 5serial IDE (SATA) 223serial numbers 117–118serial port 360, 425, 486serial transmission 133serif fonts 201server 89, 133. See also file server;Web serverserver message block (SMB) 335service broker 426service bureaus 64service-oriented architecture (SOA)110, 415, 425–426, 509service robot 183, 410servlets 255session layer 334SETI@home 116–117, 155, 217, 462sets 67, 184–185set theory 87, 351Seven Cities of Gold (game) 174sexual content, in chat rooms 83SGI (Silicon Graphics) 122SGML (Standard GeneralizedMarkup Language) 232, 520Shakey 411Shamir, Adi 146, 181Shannon, Claude E. 84, 103, 241,404, 426, 426–427, 463SHARE 373shareware and freeware 104, 293–294, 352, 427–428Shaw, Cliff 162sheet-fed scanner 416shell 110, 354, 421, 428–430, 485,488Shell, Donald L. 447shellsort 447shift operators 51shift-register algorithm 399Shimomura, Tsutomu 314Shockley, William 42, 85, 404Shockwave 20Sholes, Christopher Latham 265Shor, Peter 395Short Message Service (SMS) 477SHRDLU 27, 187Shuttlesworth, Mark 279Sidekick (Borland) 368sign 338signal conditioning circuit129–130signal processors 178signatures. See authentication;certificate, digitalsignificand 338silicon 85Silicon Graphics (SGI) 122Silicon Snake Oil (Stoll) 458Sim City 103Simon 463Simon, Herbert 26, 33, 85, 93, 162,190, 295Simonyi, Charles 430–431Simple API for SML (SAX) 161Simple Mail Transport Protocol(SMTP) 177, 177, 247Simple Object Access Protocol 1,118, 438, 508–509, 520Sims, The (game) 174, 441Simula 88, 263, 339–340, 431, 459simulation 431–432. See alsoemulation; virtualizationanalog computers in 14biological 47, 47in CAD system 98of cognition 92–93in decision support systems139fractals used in 203GIS in 208haptic interfaces for 222military use of 311in Nintendo Wii 205random number generationfor 399in scientific applications 420Simula for 431Smalltalk for 434in social sciences 441in virtual reality 271virtual reality and 495–496simulation games 103simultaneous processing 431singularity, technological 269,432–433Singularity Is Near, The (Kurzweil)269, 433site licenses 244SixDegrees.com 440Sketchpad 263, 463Skoll, Jeff 165, 343Skype 87, 496–497Slashdot 260, 480slide rule 13slides 380Slot-1 chipset architecture 86small businesses 195Small Computer System Interface(SCSI) 63, 197, 223, 335Small Office/Home Office (SOHO)230–231Smalltalk 88, 228, 263–264, 340,389, 431, 433–434smart buildings and homes 107,434–435, 435smart card 405, 435, 435–436smart cars 71–72smart mobs 198, 407, 477Smart Mobs (Rheingold) 198, 407smartphone 436–438, 437. See alsomobile computingin computer industry 108in computing history 229distance education on 154GPS in 293“hot spots” and 250iPhone 19, 147, 258keyboards and 265multimedia on 147music playback on 327PDAs and 364podcasts on 375touchscreens on 478SMB (server message block) 335SMP (symmetric multiprocessing)323SMS (Short Message Service) 477SMTP (Simple Mail TransferProtocol) 177, 177, 247sneaker-net 200Sneakers (film) 378sniping 31Snobol 82–83Snow, John 239SOA (service-oriented architecture)110, 415, 425–426, 509SOAP 1, 118, 438, 508–509, 520social bookmarking 294. See alsodel.icious.ussocial bots 83–84, 442, 481social engineering 100, 220, 314,370social impact of computing438–440in computer literacy 109Dertouzos on 141of digital photography 372of e-government 172–173Lanier on 272of online identity 237–238Shannon’s work on 427smart mobs 407virtual worlds and 348webcams in 504of World Wide Web 517social networking 440–441cyberbullying and 126cyberstalking and 126in globalization 209in intelligence agencies 119in Internet growth 248for job-hunting 349persistence of postings 332political activism and 377software agents and 289in software engineering 74support groups and 367technological singularityand 433user-created content in 487as virtual community 494in Web 2.0 502World Wide Web and 518by young people 523social sciences and computing441–442social security numbers 408Socialtext 501social virtualization 494–495social worlds 104society of mind 237, 313, 314, 442Society of Mind, The (Minsky) 237,313, 336Socket 7 chipset architecture 86sockets 469Softbank 407software. See application softwaresoftware agents 442–443artificial intelligence in 27demons and 141globalization and 209Maes’s work in 289at MIT Media Lab 314natural language processingin 330ontologies in 351in personal informationmanagers 368psychology and 391in semantic Web 424for spam 451technological singularityand 433Web 2.0 and 503Software Agents Group 289software applications. Seeapplication softwaresoftware asset management (SAM)244software crisis 443software engineering 22, 443,443–444with Ada 2benchmarks in 43blogging in 53CASE for 73, 73–74compatibility and 94–95computer engineering and101in computer science 109Cunningham’s work in 122under Defense Department2documenting in 159employment in 178emulators in 179flowcharting in 200of games 104with intentionalprogramming 430patterns used in 142professional programmingin 386quality assurance and394–395reverse engineering 404–405risk and 408Wirth on 514Software Engineering Institute(SEI) 444software installation 244software piracy and counterfeiting444–445. See also copyprotection; intellectual propertyand computingapplication service providersand 21copy protection and 117–118,246digital rights managementand 149–150in global market 108, 210by hackers 219–220policy on 472Software Publishers Association(SPA) 117software suite. See application suitesoftware testing 61, 109, 186,394–395, 408, 444, 464SOHO (Small Office/Home Office)230–231Sojourner 449Solaris 461solar power 42solid state computer 227Sony 108, 150, 445–446Sony ACID Pro 326Sony PlayStation 2 205Sony PlayStation 3 108, 205sorting and searching 109, 240–241, 401, 402, 446–448sound cards 326sound file formats 448–449source bits 51source code 95, 158SPA (Software PublishersAssociation) 117space exploration and computers45, 358, 410, 410, 449–450Space Invaders (game) 205Space Shuttle 449Spacewar 103Spafford, Eugene H. 450spam 17, 111, 332, 384, 450–451spambots 83spam filters 41, 117, 370, 451SPARC (Scalable ProcessorARChitecture) 402, 460–461,517speakers 326specialized applications 22specification 444spectral equivalence classes 452speech recognition and synthesis451–452artificial intelligence for 27for assistive devices 268Bell Labs and 42keyboards and 265Kurzweil’s work in 268, 269language translation with271military use of 311neural networks in 337in user interfaces 489Sperry-Rand (Sperry-Univac)Corporation 30, 106, 168, 227,297spiders 422spiral model 444, 444Spirit rover 449spiritual aspects of computing.See philosophical and spiritualaspects of computing

Index 577Spitzer, Eliot 453spoofing. See phishing and spoofingspool. See bufferingsports betting 346spreadsheet 452–453, 454. See alsoLotus 1-2-3; Microsoft Excel;VisiCalcfor business data processing64early market for 206mathematics with 295in office automation 342PC and 366as personal informationmanager 368statistical analysis with 458templates for 475sprites 16Sproull, Bob 463SPSS 458Spybot Search & Destroy 453spyware and adware 111, 344–345,384, 453–454SQL (Structured Query Language)454–455, 455computer science in 110for database management132for data warehouse 139for information retrieval 241Oracle and 356procedures and 337Squeak 264, 434SRI (Stanford Research Institute)320SSL (Secure Sockets Layer) 503stack 456abstract 129in C 67in C++ 68as data structure 138in Forth 201queue and 396in recursion 401Stafford-Fraser, Quentin 504Stalkerati 441stalking 100, 126, 248, 252, 523Stallman, Richard 150, 279, 352,456–457Standard Generalized MarkupLanguage (SGML) 232, 520standards in computing 457Stanford Artificial IntelligenceLaboratory (SAIL) 59, 145, 403Stanford Cart 59, 411Stanford Knowledge SystemsLaboratory 403Stanford Research Institute (SRI)320, 411Stanford Robotics Laboratory 403Stanley (car) 71–72Starflight (game) 174StarLogo 285star network 283, 283Star Office 352state-based devices 195static array 24static RAM 301static variables 491statistics and computing 270, 271,296, 330, 420, 441, 457–458stepper motor 222stepwise refinement 460Sterling, Bruce 125Steve Jackson Games 124–125Stockhausen, Karlheinz 325stock trading 348Stoll, Clifford 170, 440, 458, 494storage, networked 152, 192, 335storage area network (SAN) 192,335storage media 191stored program 227storyboarding 194Strategic Air Command (SAC) 311Strategic Air Ground Environment(SAGE) 104, 139, 212, 235, 311strategic planning 291stratification 439streaming 458–459buffering in 60codecs for 92digital convergence and 147in Internet growth 248of Internet radio 251of multimedia 322network and 335real-time processing and 400of television episodes326–327stress gauges 129STRETCH 10string-oriented languages 82–83strings. See characters and stringsstriping 398Stroustrup, Bjarne 67, 341, 459,459–460struct 65, 138structured data types 138structured programming 460. Seealso Algol; C (language); Pascalwith Ada 2BASIC and 40C++ and 459COBOL and 91in computer science 109in computing history 228Dijkstra and 151documentation in 159encapsulation in 180FORTRAN and 202Pascal. See Pascalin software engineering 443subroutines and 180variables in 491Structured Query Language. SeeSQLstyles 72subatomic particles 395–396subprograms. See proceduressubrange 185subroutine. See proceduressubscripts, in arrays 23, 24substitution ciphers 180substrate 85Sun Labs 463Sun Microsystems 113, 146, 255–256, 261, 324, 460–461SunOS 461Sun SPARC (Scalable ProcessorARChitecture) 402, 460–461,517supercomputer 461, 461–462benchmarks for 43cell chip for 205cluster computing as 217in computing history 227Cray’s work with 121–122government funding of 212grid computing as 216Prolog used in 390Superfund Program 216Super Mario Brothers (game) 205Super Socket 7 chipset architecture86Super VGA (SVGA) 213supply chain management 64, 415,462–463support groups, online 367Suraski, Zeev 372surface acoustic wave (SAW) 478surfing 422SurfWatch 505surgery 300surveillancebiometrics with 49in computer attacks 100in counterterrorism 118–119Electronic FrontierFoundation and 125with Google Earth 292image processing in 239in law enforcement 273privacy and 383surveys 441Sutherland, Ivan Edward 463SVGA (Super VGA) 213swapfile 302Swift, Jonathan 418Swiss Federal Institute ofTechnology (ETH) 362switch. See branching statementsswitched Ethernet systems 283switch statement 55Swoogle 424Symbian 437symbolic assembler 29symbolic programming 29symbolists 93symmetric multiprocessing (SMP)323synchronous DRAM (SDRAM) 301synchronous processes 154syntax error 61synthesizer, musical 268–269, 325system administrator 178, 421, 464system chart 200system clock 90systems analyst 464systems programming 29, 65, 67,464–465System X 217SYSTRAN 271Ttables, in relational databases 131tablet PC 221, 466tabulating machine 229, 230, 294,341, 392“Tactical Iraqi” (game) 311Tagged Image File Format (TIFF)215tags, markup 232, 520TAI (Technology AchievementIndex) 143Tandy 228tape drives 37, 258, 467, 467–468Tapscott, Don 524tasks, in groupware 217tax-avoidance schemes 345tax returns 79, 172, 195Tcl 468TCP (Transmission ControlProtocol) 469TCP/IP 468–470, 469Cisco’s work on 87in computer science 110development of 78DNS in 155e-mail and 177in Internet 247Internet and 518for local area networks 284for networks 334UNIX support for 261Web server and 508TD Ameritrade 348technical publishing 159technical support 140, 178, 210,230, 470–471technical writing 471–472. See alsodocumentation; documentationof program codetechnological singularity 269,432–433Technology Achievement Index(TAI) 143technology policy 472Technology-Related AssistanceAct 152Teilhard de Chardin, Pierre 369telecommunications 110, 472–473,496–497Telecommunications Act 473telecommuting 473–474telegraph 383, 493telephone 38, 58, 69, 266, 314, 383,496. See also modemtelepresence 300, 411, 474, 474–475. See also videoconferencingtelerobotics 474–475, 496teletex 168Teletype 151, 265, 381, 476television 163–164, 194television networks, onlinedistribution by 326–327telnet 248, 476template 68, 88, 96, 98, 112, 355,475terabyte 51, 298TeraGrid 217Termin, Lev 325terminal 475–476terminate and stay resident (TSR)function 321terrorism. See cyberterrorismTexas Instruments 85TeX system 267text editor 110, 387, 476, 517. Seealso word processingtexting 113, 126, 198, 477, 494,523text-to-speech software 151texture mapping 106TFT (thin film transistor) 199Therac 25 408thermistors 129thermocouples 129thermostats 124thin client 89thin film transistor (TFT) 199Thinking Machines Inc. (TMI) 461Thompson, Ken 261, 409–410,429, 485Thomson, James 13Thomson, William (Lord Kelvin)13THOR 297threads 61, 113, 154, 201, 324, 3533D graphics 213–2143DMark 433DO 1743G (third generation) 58, 514three laws of robotics 418, 433thumb drive 37, 198–199, 200,446, 487thumb tribes 198TiddlyWiki 511TIFF (Tagged Image File Format)215Time Machine 357Time magazine 207time series analysis 458time-sharingBASIC and 40in computer-aidedinstruction 99e-mail for 176–177government funding for 212hackers and 219Licklider’s work in 278mainframes and 290McCarthy’s work on 297shell and 428

578 Indexterminals in 475–476user interface for 488Weizenbaum’s work on 509Time-Warner 11–12, 350TiVo 163Tk 468TMI (Thinking Machines Inc.) 461Toffler, Alan 432token 95–96, 201, 360–361token ring network 283, 283TomTom 293toner 382Tools for Thought (Rheingold) 407topology 295torrents 193Torvalds, Linus 184, 279, 352,456–457, 477–478Toshiba 108touchpad 321, 489touchscreen 19, 175–176, 364, 466,478, 489TP (transaction processing) 130,291, 310, 478–479trace 61trackball 185, 321, 489tracker (torrent) 193trade secrets 245–246transaction processing (TP) 130,291, 310, 478–479transducer 129transfer speeds 299transformation 33transistorsin calculator 71on chips 86in computing history 227development of 42invention of 85in minicomputers 312Moore’s work with 318Sony and 445in supercomputers 461transition 196Transmeta 478Transmission Control Protocol(TCP) 469transparency, privacy and 384transport layer 334trap-door function 145–146travel, software agents for 289Traveling Salesman Problem97–98tree 138, 479, 479–480trends and emerging technologies102, 480in computer industry 108in database management132in data compression 134in data mining 136in digital photography 372in e-commerce 168–169in education 170in e-mail 177in expert systems 188in financial software 195in game consoles 205for haptic interfaces 221–222in Internet applicationsprogramming 249in laptop computers 273in medicine 300–301in networks 334–335in object-orientedprogramming 341in office automation 342in operating systems 354in PCs 366–367in search engines 423in telecommuting 474in user interfaces 489in work processors 517in World Wide Web 518Treo (Palm) 364Trilogy 10–11Trojan horse 100, 111TRS-80 228True BASIC 40TrueType fonts 3, 201Truscott, Tom 333trust and reputation systems480–481TRUSTe 345, 384TRW 206TSR (terminate and stay resident)function 321Tucows.com 428tuples 158Turbo Pascal 363, 387, 514Turbo Prolog 390Turing, Alan Mathison 87, 103,196, 481–482. See also Turingmachine; Turing testTuring Machine 481computability and 97, 295Turing Test 26, 83, 481Turk, the 84, 410Turkle, Sherry 237, 482–483turnkey system 493Turoff, Murray 114turtle, in Logo 284, 359turtle robot 124tweening 16Twiki 5112001: A Space Odyssey (film) 378,418, 419, 451two-way satellite system 416TX-2 463Type 1 fonts 3typeface. See fontstypes. See data typestypewriters 381typing, ergonomics of 185typography, computerized 267,483. See also fontsUUART (Universal AsynchronousReceiver-Transmitter) 425ubiquitous computing 331, 384,484–485. See also digitalconvergenceUbuntu 279, 280, 306, 309UCSD P-System 362, 387–388, 391UDDI (Universal DescriptionDiscovery and Integration)508–509UDP (User Datagram Protocol)469Ulam, Stanislaw 432Ultima (game) 104, 174Ultima Online (game) 347ultra broadband 58Ultra Card 436ultra-wide band (UWB) 53UML (Unified Modeling Language)315Unabomber 261Unbox 327Unfinished Revolution, The(Dertouzos) 141Unicode characters 82, 247Unified Modeling Language (UML)315uniform resource locator (URL)43, 157–158, 503, 508, 518. Seealso DNSUnimate (robot) 182–183, 410Unimation 182, 410uninterruptible power supply(UPS) 37, 152union 65Unisys Corporation. See Sperry-Rand CorporationUnited Nations 251UNIVACin computing history 227Cray’s work on 121Hopper’s work on 231mainframes and 290marketing of 106Mauchly’s work on 296–297memory in 301in popular culture 378Presper’s work on 167–168social impact of 438Univac (company) 212Universal Asynchronous Receiver-Transmitter (UART) 425universal computer concept 179,196, 336Universal Description Discoveryand Integration (UDDI)508–509Universal Plug and Play (UPnP)374universities 212, 219. See alsospecific universitiesUniversity of Phoenix 170UNIX 485–486. See also LinuxAPI of 354ASP .NET on 1awk scripting languagefor 33compiling in 97in computer history 228–229C on 65data security in 136–137development of 42, 312, 404,409–410file attributes in 191file transfer for 194GNU project and 456help system in 225Internet and 518Joy’s work on 261kernel in 264Linux and 279mathematics software in 295multitasking in 325netnews and 333in OS X 19, 258, 288, 357parsing in 360programming environmentof 387real-time processing in 400regular expressions in 402scripting in 422shell and 428–429software installation on 244Sun and 461terminals and 476text editing in 476time-sharing with 353Torvalds work with 477. Seealso Linuxuser groups for 488user interface of 488in workstations 517Unlawful Internet GamblingEnforcement Act 346upload speeds 58UPnP (Universal Plug and Play)374UPS (uninterruptible powersupply) 37, 152upward compatibility 94urban playground movement 198URL (uniform resource locator)43, 157–158, 503, 508, 518. Seealso DNSusability 141, 394, 489USA.gov 172USB (universal serial bus) 486–487in boot sequence 55for data backup 37for digital cameras 372for external hard disks 223FireWire and 197for flash drives 198introduction of 63on laptops 272parallel ports and 360serial ports and 425U.S. Department of Defense. SeeARPANET; DARPAUsenet. See netnews andnewsgroupsUser Account Control 100, 307user accounts 354user-created content 487–488on Amazon.com 9blogs as 52, 53on bulletin boards 61–62in computing history 229in development of WorldWide Web 44on eBay 165–166, 343in e-commerce 169in globalization 209mashups 294multimedia 323open-source movement and352in personal healthmanagement 367–368in trust and reputationsystems 480video 493, 524in Web 2.0 502in Wikipedia 511–513in wikis 511on YouTube 493, 524User Datagram Protocol (UDP) 469user-defined data types 138, 286,362user documentation. Seedocumentation, useruser groups 260, 427, 488user interface 488–489. Seealso application programinterface; graphics tablet; hapticinterfaces; keyboard; mousecomputer science in 110copyright and 245for decision support systems140for digital dashboard 148disabled users and 152Engelbart’s work in 182graphics on 105for Macintosh 18, 228, 258,287, 307for Microsoft .NET 307in Microsoft Visual Basic 388in Microsoft Windows 206,308in Microsoft Windows Vista307in Nintendo Wii 205for operating systems 354psychology and 391Sketchpad and 463for terminals 476in UNIX 485in virtual reality 271voice-controlled 330by Xerox PARC 105, 404Userland Software 52users 37, 100, 130, 394user status 136, 137, 191Utah Street Networks 87UUCP 333

Index 579Vvacuum, robotic 253vacuum tube 85, 226, 525–526vandalism, electronic 100van Rossum, Guido 392variables 490–491. See also flagas address 3in Algol 7in Analytical Engine 35in BASIC 40binding and 45in classes 88COBOL and 91in compiling 96constants and 115in data mining 136functional languages and203–204in Pascal 362in PL/I 373in procedural languages 388in procedures 385in scripting languages 421in Smalltalk 433in Tcl 468variance, analysis of 458VAXcluster 216VAX minicomputers 41, 261VBA (Visual Basic for Applications)289, 422VBScript 422, 491–492, 508VDT (Video Display Terminal) 317Veblen, Oswald 86vector data 208, 337vectored interrupts 243vector fonts 201vector graphics 50, 214vector processing 461VeriSign 78–79Verizon Fios 58, 69, 191Verne, Jules 418Verro (robot) 253versioning 74, 115, 159VESA bus 63VGA (Video Graphics Array) 62,213, 236vi 261video, on PCs 322video accelerator 214video blogging 52video buffer 60video cameras, digital 372, 446,492video card. See graphics cardvideo cassette recorders (VCRs)163videoconferencing 83, 322, 342,474, 492–493, 497. See alsotelepresenceVideo Display Terminal (VDT) 317video distribution, online. Seemusic and video distribution,onlinevideo editing, digital 493. See alsophotography, digitalvideo games. See computer gamesVideo Graphics Array (VGA) 62,213, 236video players, digital. See musicand video players, digitalVideo RAM (VRAM) 214Viewpoints Research Institute 264Viking landers 449Vinge, Verner 28, 419, 432violence, in games 104Violence Against Women Act 126virtual classes 88virtual community 83, 114, 125,407, 440, 493–494, 518Virtual Community, The (Rheingold)407virtual functions 68, 88virtual identities 237–238, 348virtualization 209, 494–495. Seealso simulationvirtual library 166–167, 211, 260virtual machine 95, 179, 286,434, 494. See also Java VirtualMachinevirtual memory 3, 224, 261, 302,308, 353Virtual Private Network (VPN)494, 513virtual property law 124virtual reality 495, 495–496art in 26in cyber culture 126digital convergence and 148Lanier’s work in 271–272military use of 311multimedia and 322neural interfaces and 335programming environmentin 388in science fiction 419for telepresence 474ubiquitous computing and484as user interface 489wearable displays for 501Virtual Reality (Rheingold) 407Virtual Reality Modeling Language(VRML) 496virtual school 170virtual worlds 104, 124, 237, 347–348, 391, 441–442, 482virus. See computer virusVisiCalc 18, 106, 258, 295, 366,452, 458vision, computer 27, 112, 363, 411VisualAge RPG 412Visual Basic 20, 40, 309, 387, 388,422, 491Visual Basic for Applications (VBA)289, 422visualization 47, 47, 420–421VL bus 63VMware 179, 494vocoder 42voice-coil actuator 222voiceprint 48voice recognition. See speechrecognition and synthesisvoice scanning 48voice synthesis 151VoIP (voice over Internet protocol)496–497, 497broadband for 59cable service and 69, 163for chat 83Cisco’s work in 87satellite service and 416telecommunications and 473Volkswagen Touareg 71–72von Neumann, John 28, 167, 190,329, 432, 497–499, 498von Rospach, Chuq 331voting systems, electronic 175,175–176Voyager 2 449voyeurism 504VPL Research 271VPN (Virtual Private Network)494, 513VRAM (Video RAM) 214VRML (Virtual Reality ModelingLanguage) 496WWAIS (Wide Area InformationService) 248, 518Wales, Jimmy 500–501, 511Wall, Larry 365Wallace, Bob 427–428Wallace, Richard 84Walt Disney Imagineering 264Walter, Grey 59, 124WAN (wide area network) 133, 334Wang, An 341Wang Corporation 106, 516Warcraft 104warez 220war games 103War Games (film) 378Warnock, John 3, 379Warwick, Kevin 406Wasik, Bill 198watch 61waterfall model 443, 444Watson, Thomas, Sr. 5, 235Wave Table Synthesis 326WAV format 448Wayne, Ronald 18wearable computers 141, 496,501, 501wearIT@work 501Weaving the Web (Berners-Lee) 424Web. See World Wide WebWeb 2.0 110, 501–503, 502Web browser 503, 503–504. Seealso Microsoft Internet Explorer;Mosaic; Netscape Navigatoranti-phishing in 370Berners-Lee and 43in blogging 52bulletin boards and 62cache for 70in computer history 229cookie control in 116digital dashboard and 148disabled users of 152for file transfer 194history in, Ajax pages and 6in Internet growth 247, 248JavaScript in 256Microsoft Windowschallenged by 107multimedia and 322navigation in 234newsreaders in 333plug-ins for 374on smartphones 437threading in 324XML in 520Web cam 83, 492webcam 504–505Web crawler 141, 422webcrawler 241WebEx 87Web feed 375, 412–413Web filter 76, 77, 505, 523Web logs. See blogs and bloggingwebmaster 80, 505–506WebMD 367Web Ontology Language (OWL)20, 267, 351, 424Web page design 506–507Ajax for 5–6applets in 19–20cascading style sheets in 72DOM for 161for information display 240with JavaScript 256PHP for 372scripting in 422user interface in 489Web browser and 504webmaster and 506Web portal 350, 379, 422, 523Web server 507–508access from ISPs 252Berners-Lee and 43caching by 70for client-server computing89cookies from 116development of 107digital dashboard on 148queue in 396by Sun 461VBScript and 491webmaster and 505–506World Wide Web and 518Web services 508–509active server pages for 1broadband connectionsand 58CGI for 80–81employment in 179JavaScript and 256–257in service-orientedarchitecture 426SOAP for 438Web Services Description Language(WSDL) 426Web sitesattacks on 127banner ads on 344for businesses 64content management of115–116for database hosting 342databases and 132disabled users of 152document model in 161for government agencies 172for help systems 225in information warfare 242for newspapers 259in office automation 342political activism and 377spoofing 369–370for technical support 470for user documentation 159viruses from 111Web server and 507–508from Yahoo! 523WebTV 107WebVan 168Weinberger, Peter J. 33Weizenbaum, Joseph 26, 83, 442,509–510Weizmann Institute of Science 317WELL, The 17, 62, 113, 314, 407,493–494Westin, Alan F. 383Westlaw 274What Computers Can’t Do (Dreyfus)162What Computers Still Can’t Do(Dreyfus) 162What Will Be (Dertouzos) 141Whetstone 43Whirlwind 104, 212whiteboard programs 217, 342, 492white box testing 394–395Whitman, Margaret (Meg) 165,166, 343, 515Whois 17Whole Earth Catalog (Brand) 407Wide Area Information Service(WAIS) 248, 518wide area network (WAN) 133, 334widgets 73Wiener, Norbert 124, 277, 510–511Wiesner, Jerome 313, 331, 511WiFi 53, 513. See also wirelesscomputingWii 205, 221wiki(s) 511–513accuracy of 259on Amazon.com 9as content managementsystems 116

580 Indexdatabases in 132development of 122on eBay 166Google and 211as groupware 217hypertext in 234in Internet growth 248journalism and 259for legal information 274netiquette and 332in office automation 342user-created content of 487Wikia, Inc. 500, 513Wikimedia Foundation 500, 513Wikinomics (Tapscott andWilliams) 524Wikipedia 119, 122, 292, 350, 487,500–501, 511–513, 512WikiScanner 513wildcards 402, 403Williams, Anthony D. 524Williams, John 447Williamson, Jack 418WiMAX 58, 514Windows. See Microsoft WindowsWine 405Winer, David 52WinHelp 225Wintel. See IBM PC; Intel;Microsoft WindowsWinZip 428Wired 260, 331wireless computing 513–514with Bluetooth 53broadband 58data communications over134in developing nations 143employment in 179at “hot spots” 250with laptops 272, 273for local area networks 284mouse 321with PDAs 364for portable devices 107with tablet PC 466transfer speed of 299USB adapters for 487wiretapping 119, 242, 273, 383,497Wirth, Niklaus 362, 363, 460,514–515WISC (Wisconsin IntegrallySynchronized Computer) 10Wizardry 104wizards 225, 308WLAN. See wireless computingWMI (Windows ManagementInstrumentation) 492Wolfram, Stephen 76women and minorities incomputing 515–516Wonder, Stevie 268WordPerfect 516WordPress 52word processing 516–517in business 64computer science in 110desktop publishing and 143document model and 160early market for 206in office automation 341–342revision marking in 342templates in 475text editors and 476typography in 483word processors (machines) 106words, in Forth 201WordStar 516workstation 517World Community Grid 117World of Warcraft (game) 286, 347World Wide Web 517–519. See alsoWeb browserAOL and 11bulletin boards and 62business use of 64centralization and 439–440in computer history 229conferencing systems on 114development of 43disabled users and 152as distributed computing154in education 169empowerment by 439entrepreneurship and 184hypertext on 233information design on 240in Internet development247, 248libraries and 276medical information on300–301Microsoft and 305–306multimedia on 322–323for online research 350PDFs on 364in personal healthinformation management367philosophy and 369portals for 350, 379, 422, 523professional programmersand 386senior citizens’ use of424–425standards for 457telecommunications and 473terrorists on 126–127user interface and 489World Wide Web Consortium(W3C) 43, 141, 161, 251, 457worm 111, 450, 492Wozniak, Steven 18, 258, 519wrist rest 185write attribute 191WSDL (Web Services DescriptionLanguage) 426W3C 43, 141, 161, 251, 457WYSIWYG 142, 287, 507, 516XX10 324Xanadu 233Xbox 205, 206, 306Xbox 360 108, 205Xcode 357XCON 187Xerox PARC (Palo Alto ResearchCenter) laboratory 18Ethernet at 283Kay at 263–264laptop and 273PostScript and 379research of 404Simonyi at 430Simula developed at 339–340Smalltalk at 433ubiquitous computing at 484user interface developed at258, 307, 463, 488workstation at 517XHTML (Extensible HyperTextMarkup Language) 5–6,232–233, 233, 256, 520. See alsoDHTML; HTMLXML (extensible markup language)520–521in ASP .NET 1computer science in 110with DOM 161for information retrieval 241for Internet applicationsprogramming 249Java with 255knowledge representationin 267for RSS 412in service-orientedarchitecture 426in SOAP 438Web servers and 508in Web services 508Xmodem 194XNU 357XOR operator 51, 54XSLT (XML style sheet processor)161XWindows 354YY2K problem 91, 159, 178, 439,522–523YACC 361Yahoo!advertising on 346censorship in China and 76in Chinese market 108entrepreneurship and 184Microsoft acquisition of 306for online research 350, 422online services and 350as portal 379, 422Yahoo! Inc. 523Yahoo! Internet Life 260Yahoo! Messenger 492Yang, Jerry 184, 379, 422, 523yellow, in CYMK 93“Yenta” agent 289Ymodem 194young people and computing 237,248, 477, 523–524YouTube 524access to 194advertising on 345distribution by 326DVRs and 164Google and 211journalism and 260in mashups 294political activism and 377streaming by 459user-created content of 487Yudkowsky, Eliezer 433ZZ1 525Z3 525Z4 525Zadeh, L.A. 204Z-buffer algorithm 106ZDNet 260, 293–294, 428Zen 327Ziff Davis 260Zimmermann, Philip 181Zimmermann, Tom 271Zip disks 200Zip program 134Zmodem 194ZOG/KMS 140ZoneAlarm 197Zuckerberg, Mark 440Zune 327Zuse, Konrad 226, 525–526ZUSE KG 526

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