谁帮我解一下这个c++程序问题？

你改一下吧，我不想弄了
#include<stdio.h> /*引用库函数*/
#include<stdlib.h>
#include<ctype.h>
#include<string.h>
typedef struct /*定义结构体数组*/
{
char num[10]; /*学号*/
char name[20]; /*姓名*/
int score; /*成绩*/
}Student;
Student stu[80]; /*结构体数组变量*/
int menu_select() /*菜单函数*/
{
char c;
do{
system("cls"); /*运行前清屏*/
printf("\t\t****Students' Grade Management System****\n"); /*菜单选择*/
printf("\t\t | 1. Input Records |\n");
printf("\t\t | 2. Display All Records |\n");
printf("\t\t | 3. Sort |\n");
printf("\t\t | 4. Insert a Record |\n");
printf("\t\t | 5. Delete a Record |\n");
printf("\t\t | 6. Query |\n");
printf("\t\t | 7. Statistic |\n");
printf("