输入一个圆半径r,当r>=0时,计算并输出圆的面积和周长,否则,输出提示信息。
#include <stdio.h>
#define PI 3.14
int main(void)
{ double r ,area , girth;
printf("please input r:\n");
scanf("%lf",&r);
if (r>=0)
{ area =PI*r*r;
girth =2*PI*r ;
printf("the area is %.2f\n", area);
printf("the girth is %.2f\n", girth);}
else
printf("Input error!\n");
return 0;
}
运行结果:
当r>=0时:
当r<0时: