#include<stdio.h>
double Fact(unsigned int n);
int main()
{
    int m;
    for (m=1; m<=40; m++)
    {
        printf("%d! = %.0f\n", m, Fact(m));
    }
    return 0;
}
double Fact(unsigned int  n)
{
    unsigned int   i;
    double result = 1;
    for (i=2; i<=n; i++)
        result *= i;
    return result;   
}

用%g格式输出

可以用数组存，对于这种溢出的情况；

自己用数组实现乘法运算

        #include<stdio.h>
         int fab( int n)
        {   int c;
            if(n==1||n==0)
                c=1;
          else c=fab(n-1)*n;
          return c;
        }
        int main()
    {
        int n;
        printf("请输入一个数：\n");
        scanf("%d",&n);
        printf("%d的阶乘是%d\n",n,fab(n));
        return 0;
    }
试一下这个。