1. CS149D Elements of Computer Science
Ayman Abdel-Hamid
Department of Computer Science
Old Dominion University
Lecture 14: 10/17/2002
Lecture 14: 10/17/2002
CS149D Fall 2002

2. Outline Simple C++ programs Program structure
A simple C++ program: Hello World Program!
A longer C++ program: Compute distance between two points
Lecture 14: 10/17/2002
CS149D Fall 2002

3. The main() function body
C++ Program Structure
Global area
The main() function body
Another function
Another function
Lecture 14: 10/17/2002
CS149D Fall 2002

4. A Simple C++ Example White Space? /* Author: Ayman Abdel-Hamid */
// This is your first C++ program
// The program will only print hello on the command line
#include <iostream.h>
#include <stdlib.h>
int main() {
cout << “Hello” ;
return 0; }
Comments
Preprocessor directives
White Space?
Any C++ program must have a main function
All C++ statements must end with a ;
Lecture 14: 10/17/2002
CS149D Fall 2002

5. A Longer Example1/3 Problem Statement Input Output
Compute the straight line distance between two points in a plane
Input
A point has an x and y coordinates. We need 2 points
Assume (x1, y1) = (1,5) & (x2, y2) = (4,7)
Output
The distance between the 2 points. How?
(x1, y1)
(x2, y2) x1 x2 y1 y2
side1
side2
distance
Calculate side1 = x2 - x1
Calculate side2 = y2 - y1
Calculate distance =
Square root (side12 + side22)
Lecture 14: 10/17/2002
CS149D Fall 2002

6. A Longer Example2/3 Algorithm Assign x1 the value 1
Assign y1 the value 5
Assign x2 the value 4
Assign y2 the value 7
Assign side1 the value x2 –x1
Assign side2 the value y2-y1
Assign distance the value sqrt (side12 + side22)
Write distance on the screen
Stop
Lecture 14: 10/17/2002
CS149D Fall 2002

7. A Longer Example3/3
// This program computes the distance between two points. A point has an x and y coordinate
//Program from Etter Text, chapter 2, page 22 (also chapter 1, page 17)
//Preprocessor directives
#include <iostream.h>
#include <stdlib.h>
#include <math.h>
int main() {
// Define and initialize variables.
double x1=1, y1=5, x2=4, y2=7, side_1, side_2, distance;
// Compute length of sides of right triangle.
side_1 = x2 - x1;
side_2 = y2 - y1;
distance = sqrt( side_1 * side_1 + side_2 * side_2 );
// Print distance.
cout << "The distance between the two points is "<< distance << " cm." << endl;
// Exit program.
return EXIT_SUCCESS; }
Lecture 14: 10/17/2002
CS149D Fall 2002