#include<stdio.h>
viod main()
{
    int n,sel;
    double res;
    double fact(int n);
    double sum(int n);
    while(1)
    {
        printf("    菜单功能\n");
        printf("------------------------------------\n");
        printf("1-求阶乘     2-求累加和     0-退出\n");
        printf(-------------------------------------\n");
            printf("请选择输入(1、2或0):");
        scanf("%d",&sel);
        if(sel==0)break;
        switch(sel)
        {
        case 1:
            printf("请输入一个正整数:");
            scanf("%d",&n);
            res=fact(n);
            printf("%d!=%1f\n",n,res);
            break;
        case 2:
            printf("请输入一个正整数:");
            scanf("%d",&n);
            res=sum(n);
            printf("1+2+...+%d=%1f\n",n,res);
            break;
        default:
            printf("选择错误！\n");
            break;
        }
    }
    printf("欢迎下次使用!\n");
}
double fact(int n)
{
    int i,n;
    double xu;
    xu=1;
    for(i=1;i<=n;i++)
    xu=xu*i;
    xu=fact(n);
    return fact(n);
}
double sum(int n)
{
    int b,n;
    double he;
    he=0;
    for(i=1;i<=n;i++)
        he=he+i;
    he=sum(n);
    return sum(n);
}
这是简单的计算器编程，只有阶乘和累加的功能，但是我运行时，它说error C2146: syntax error : missing ';' before identifier 'main'，这是啥，要在哪里加；