用c或c++编写一个多级菜单。至少三级。

一个参考程序如下。程序涉及到一些底层库函数的调用和cpu内部寄存器的使用，需要有相当软硬件水准去理解。
编译环境：中文win-tc或tc3.0或borland c++
#include <stdio.h>
#include <dos.h>
#include <stdlib.h>
#include <bios.h>
#include <conio.h>
#include <string.h>
#include <ctype.h>

#define BORDER 1
#define ESC 27
#define REV_VID 0x1e
#define NORM_VID 0x40

char *main_menu[] =
{
"F --- 文件管理",
"D --- 磁盘管理",
"H --- 打印服务",
"X --- 退出菜单",
};

char* sub_menu1[] =
{
"S --- 文件显示",
"P --- 文件打印",
"C --- 文件拷贝",
"D --- 文件删除",
"X --- 返回上级",
};

char* sub_menu2[] =
{
"B --- BOOT区备份",
"R --- BOOT区恢复",
"X --- 返回上级",
};

char* sub_menu3[] =
{
"O