void Data_()
{
    struct tm *sysTime;
    time_t nowTime;
    time(&nowTime);
    sysTime=localtime(&nowTime);

    printf("系统日期：%d-%d-%d \n",1900+sysTime->tm_year,symTime->tm_mon,sysTime->tm_mday);

}
void Time_()
{
    struct tm *sysTime;
    time_t nowTime;
    time(&nowTime);
    sysTime=localtime(&nowTime);
   
    printf("系统日期：%d:%d:%d \n",sysTime->tm_hour,symTime->tm_min,sysTime->tm_sec);
}
error: 'symTime' undeclared (first use in this function)|

怎么会没有声明变量

#include <stdio.h>
#include <windows.h>

int main()
{
    SYSTEMTIME stTime;
    GetSystemTime(&stTime);
    printf("%d年%d月%d日\n", stTime.wYear, stTime.wMonth, stTime.wDay);
    printf("%d点%d分%d秒\n", stTime.wHour, stTime.wMinute, stTime.wSecond);
    return 0;
}

你那段代码没写全，我上面给你重写了一段。

#include<stdio.h>
#include<time.h>
void Manu_();
void Data_();
void Time_();
void Exit_();
int main()
{

    struct tm *sysTime;
    int num;
    while(1)
    {
        printf("Please chooce one:");
        scanf("%d",&num);
        switch(num)
        {
        case 0:
            Manu_();
            break;
        case 1:
            Date_();
            break;
        case 2:
            Time_();
            break;
        case 3:
            Exit_();
            break;
        default:
            Manu_();
        }
    }

}
void Manu_()
{
    printf("Welcome!\n0--Manu\n1--Data\n2--Time\n3--Exit\n");
}
void Data_()
{
    struct tm *sysTime;
    time_t nowTime;
    time(&nowTime);
    sysTime=localtime(&nowTime);

    printf("系统日期：%d-%d-%d \n",1900+sysTime->tm_year,symTime->tm_mon,sysTime->tm_mday);

}
void Time_()
{
    struct tm *sysTime;
    time_t nowTime;
    time(&nowTime);
    sysTime=localtime(&nowTime);

    printf("系统日期：%d:%d:%d \n",sysTime->tm_hour,symTime->tm_min,sysTime->tm_sec);
}
void Exit_()
{
    return;
}
这是全部的代码，哪里有错吗

程序没什么错误  之所以编译不过 全部是拼写错误  很低级的错误

请自行查找