#include<stdio.h>
#define g 10
int calculate(int Mass);
int main()
{
    int m_Mass;
    int gravity;
    float Mass;
   
   printf("请输入物体的质量:\n");
    scanf("%d",&m_Mass);
   
    gravity=calculate(m_Mass);
    printf("物体的重力为:");
    printf("%d\n",gravity);
    return 0;
}
    int calculate(int Mass)
        {
            int gravity=Mass*g;
            return gravity;
        }

float Mass的用意是啥？你返回的整数，printf出来的也是取整，怎么会输出小数？

好，我改改