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;
}