#include <stdio.h>
#include<stdlib.h>
#include<string.h>
void tongji();
void demand age();
void demand work();
void demand sex();
int main()
{
    char choice[3]="";
    int len=0;
    while (choice[0]!='3')
    {
        system("color 7D");
        printf("\n统计员工信息系统\n");
        printf("\n========================\n");
        printf("\n1、按年龄查询工信息\n");
        printf("\n2、按工作查询信息\n");
        printf("\n3、按性别查询信息\n");
        printf("\n========================\n");
        printf("\n请选择（1-3）：");
        scanf("%s",choice);
        len=strlen(choice);
        if(len>1)
        {
            printf("\n请输入1-3之间的整数\n");
            printf("\n按任意键返回主菜单......\n");
            getchar();
            getchar();
            continue;
        }
        switch (choice[0])
        {
        case '1':
            demand age();
            break;
        case '2':
            demand work();
            break;
        case '3':
            demand sex();
            break;
        default:
            break;
        }

}
system("pause");
return(0);
}

 

demand 是什么东西?

void demand age();//void demand_age();
void demand work();//void demand_work();
void demand sex();//void demand_sex();