c07_02.c

it can help you know C++ souce program quckily

/*用带参数的宏定义计算圆面积*/
#include <stdio.h>
#define PI 3.1415926
#define S(r) PI*(r)*(r)

int main()
{
	float	area, m;
	printf("请输入圆的半径：\n");
	scanf("%f",&m);
	area=S(m);
	printf("圆面积S=%f\n", area);
	
	return 0;
}