题目一：简单输出

#include <stdio.h>
int main()
{
     printf("Hello word! \n");
     return 0;
}

题目二:圆的面积

#include <stdio.h>
#define PI 3.14
double calculateVolume(int radius);
int main()
{
     int cRadius = 0;
     double volume = 0;
     printf("请输入圆的半径: \n");
     scanf("%d", &cRadius);
     volume = calculateVolume(cRadius);
     printf("圆的面积是：%f \n", volume);
     return 0;
}
double calculateVolume(int radius)
{
      double result = PI*radius*radius;
      return result;
}