使用const来定义常量值

#include <stdio.h>

int main(void)
{
  float diameter = 0.0f;                    // The diameter of a table
  float radius = 0.0f;                      // The radius of a table
  const float Pi = 3.14159f;                // Defines the value of Pi as fixed

  printf("Input the diameter of a circle:");
  scanf("%f", &diameter);

  radius = diameter/2.0f;

  printf("/nThe circumference is %.2f.", 2.0f*Pi*radius);
  printf("/nThe area is %.2f./n", Pi*radius*radius);
  return 0;
}