The document provides information on three programming languages: COBOL, LISP, and Python. COBOL was released in 1959 and was used for 80% of business transactions due to its reliability. LISP was the second high-level language created in 1958 and introduced innovations like garbage collection and recursion using linked lists. Python was developed in the 1990s and prioritizes readability through features like whitespace and a simple grammar.
1. COBOL Background
Released in 1959
Grace Hopper
Industry, universities, and government collaboration
Cold War pressures
80% of business transactions
65% of all code is in COBOL
2. COBOL – Why?
Software Lifecycle
Cheaper to maintain
Y2K
Self-documenting code
Verbose
“IF a < b AND > c …”
Divisions
4. COBOL – Data Division
Data Division
Pictures
9 = digit
X = any character
A = alphabetic character
V = decimal point position
S = sign
Repeats
PIC 9 (4) = 9999
8. COBOL
Reliability
Stood test of time
Has “ALTER X TO PROCEED TO Y” (a negative)
Uses GOTO statements (a negative)
Today
Cross platform: OpenCOBOL C translation
IDEs (Net Express)
16. LISP - Examples
If then else
(if nil
(list ‘2 ‘3)
(list ‘5 ‘6))
One line variant:
(if nil (list ‘2 ‘3) (list ‘5 ‘6))
17. LISP - Examples
Factorial
(defun factorial (n)
(if (<= n 1)
1
(* n (factorial (- n 1)))))
One line variant:
(defun factorial (n) (if (<= n 1) 1 (* n (factorial (- n 1)))))
21. Python
Developed early 1990’s
Guido van Rossum
ABC language
Python 2.0
2000
Community-supported -> reliability
Modular; community expandable
Python 3.0
2008
22. Python – Readability is Key
Design goal
One way to do things
Clarity over clever code
Whitespace over braces
“pass” for No-Op
23. Python
Writability
Similar to other OO languages
Verification support
Interpreted, assert, no statements in conditions
Clean style
Few keywords
Simple grammar -> few ways to do something
24. Python
Comparisons
== tests values, not references
A < b <= C works properly
Ternary operator readable
“a if b else c”
26. Python - Examples
a = 15
if(a < 10):
print(“input less than 10”)
elif(10 < a < 20):
print(“input between 10 and 20”)
else:
print(“input greater than 20”)
27. Python - Examples
Function definition
def greatest(a, b, c):
largest = a if a > b else b
largest = largest if largest > c else c
print(largest)
Function call
greatest(7, 3, 14)
14
28. Python - Examples
Determine if prime
def isPrime(num):
prime = True
for i in range(2, (num / 2) + 1):
if num % i == 0:
prime = False
return prime
29. def tenPrimes():
list = []
count = 0
current = 2
#store the first 10 primes in a list
while count < 10:
if isPrime(current):
count += 1
list.append(current)
current = current + 1
#print the list
for element in list:
print(element)
