/* Peter Cline CISC 105, June 6 2007
 * 
 * calculates area of a circle
 */

#include <stdio.h>
#define PI 3.14159

int main() {
  double radius = 0;
  double area = 0;

  printf("Enter a radius: ");
  scanf("%lf", &radius);

  /* area is calculated by the formula: area = pi*r^2 */
  area = PI*radius*radius;

  printf("The area of the circle with the radius %lf is: %lf\n", radius, area);

  return 0;
}