c how to program 习题3.41

运行结果：

C语言代码：

/* c how to program 习题3.41 */
#include <stdio.h>

// function main begins program execution
int main( void )
{
    //分别定义变量半径，直径，周长，面积
    float radius, pi = 3.14159;
    //获取半径的值
    printf("请输入圆的半径：", radius);
    scanf("%f", &radius);
    printf("\n圆的直径是：%.2f", radius * 2);
    printf("\n圆的周长是：%.2f", radius * 2 * pi);
    printf("\n圆的面积是：%.2f\n", radius * radius * pi);
}