Handout - Function using global variables

// Program to calculate the area of a triangle 
// USE OF GLOBAL VARIABLES IS, UNDER MOST CIRCUMSTANCES,
// CONSIDERED POOR PROGRAMMING PRACTICE.
//
#include < iostream>
#include < cmath>

using namespace std;

float AreaTriangle ();  // prototype 

// DECLARE GLOBAL VARIABLES
float a, b, c;          // the three sides of the triangle

int main ()
{

  float area;

  cout << endl << "This program calculates the area of a triangle";
  cout << endl << " given the lengths of the three sides" << endl;

  cout << "Enter lengths of the three sides:  ";
  cin >> a >> b >> c;
  
  area = AreaTriangle();
  cout << endl << "The area of the triangle is " <<  area << endl;

  return 0;
}


/* 
 * PRE:  a, b, and c (WHAT ARE THEY?) are positive numbers that
 *       form the sides of a triangle
 * POST: returns the area of a triangle with sides a, b, c   
 */

float AreaTriangle ()
{
  float s;		// local variable - the semiperimiter

  s = (a + b + c) / 2.0;
  return (sqrt ( s * (s - a) * (s - b) * (s - c) ) );
}