// FILE: AreaMain.cpp
// FINDS AND PRINTS THE AREA AND CIRCUMFERENCE OF A CIRCLE
//    USING FUNCTIONS

#include <iostream.h>

   // global constant ...
   const double pi = 3.14159;

   // Functions used ...
   // COMPUTES THE AREA OF A CIRCLE
   double compute_area     (double);	// IN: radius of the circle

   // COMPUTES THE CIRCUMFERENCE OF A CIRCLE
   double compute_circum     (double);	// IN: radius of the circle

   // COMPUTES THE CIRCUMFERENCE OF A CIRCLE
   double compute_circum     (double);	// IN: radius of the circle

   // COMPUTES THE SQUARE OF A FLOATING-POINT NUMBER
   double square_double     (double);	// IN: number to be squared

int main ()
{
   // Local data ...
   double radius;	// input: radius of circle
   double area;	// input: area of circle
   double circum;	// output: circumference of circle

   // Read radius of circle.
   cout << "Enter the circle radius: ";
   cin  >> radius;

   // Compute area of circle.
   area = compute_area (radius);

   // Compute circumference of circle.
   circum = compute_circum (radius);

   // Display area and circumference.
   cout << "The area of the circle is " << area << endl;
   cout << "The circumference of the circle is " << circum
         << endl;

   return 0;
}

// COMPUTES THE AREA OF A CIRCLE
double compute_area  (double r)	// IN: radius of the circle
{
   // Compute and return the area.
   return pi * square_double (r);
}  // end compute_area

// COMPUTES THE CIRCUMFERENCE OF A CIRCLE
double compute_circum  (double r)		// IN: radius of the circle
{
   // Compute and return the circumference.
   return 2.0 * pi * r;
}  // end compute_circum

// Insert definition for function square_double
double square_double     (double x)	// IN: number to be squared
{
   return x * x;
}// end square_double