/*------------------------------------------------------------------*/
/* circle.c                                                         */
/* Definition of a simple main function.                            */
/*------------------------------------------------------------------*/

#include <stdio.h>

#define PI 3.14159265358979323846

int main(void)

/* Read a circle's radius from stdin, and compute and write its
   diameter, circumference, and area to stdout.  */

{
   int iRadius;
   int iDiameter;
   double dCircumference;
   double dArea;

   printf("What is the circle's radius?\n");
   scanf("%d", &iRadius);

   iDiameter = 2 * iRadius;
   dCircumference = PI * (double)iDiameter;
   dArea = PI * (double)iRadius * (double)iRadius;

   printf("\n");
   printf("A circle with radius %d has diameter %d,\n", 
      iRadius, iDiameter);
   printf("circumference %f, and area %f.\n", dCircumference, dArea);

   return 0;
}


/* Sample executions:

$ gcc -Wall -ansi -pedantic -o circle circle.c

$ circle
What is the circle's radius?
1

A circle with radius 1 has diameter 2,
circumference 6.283185, and area 3.141593.

$ circle
What is the circle's radius?
5

A circle with radius 5 has diameter 10,
circumference 31.415927, and area 78.539816.

*/