Slide 1.8: Topics covered (cont.): Data structures and algorithms

Data Structures and Algorithms

Computer modeling is the process of creating an abstract model (including databases, data structures, and algorithms) to simulate the behavior and response of a real-world problem like air transportation system.

For example, a GCD (greatest common divisor) algorithm is given on the right side. Below is the system implemented by using Python, where the % operator is the modulo operation that returns the remainder of a division:

procedure GCD( int a, int b )
  repeat
    gcd = a mod b
    a = b
    b = gcd
  until a mod b == 0
  return gcd
end procedure

a = b =

~/public_html/cgi-bin/101/1/GCD.py (simplified)

#!/usr/bin/python
#
# Python code to demonstrate a naive method
#   GCD (greatest common divisor) using Euclidean algorithm
#

import cgi       # CGI module

form = cgi.FieldStorage( )     # Reads the HTML form data.
act  = form["act"].value
a    = form["a"  ].value
b    = form["b"  ].value

if ( act == "Find GCD( a, b )" ):
  # Print HTML.
  print( "Content-type: text/html\n\n" )
  # Command issued:
  print( "/usr/bin/python GCD.py " + a + " " + b )

  print( "GCD( " + a + ", " + b + " ) = " )
  a = int( a )
  b = int( b )
  while( b ):
    a, b = b, a % b
  print( abs( a ) )

Review: Computer Modeling

Computer modeling is the process of creating an abstract model to simulate the behavior of a real-world problem. Which is NOT included in an abstract model?

Result: