c++学籍管理系统

程序在编译时出错（vc++ 6.0）

求哪位大神帮忙改改

#include<iostream>
#include <string>
#include<conio.h>
void bangzhu();

using namespace std;
class sj
{public :
int year,month,day;                             ////////时间类
void shuru()
{cin>>year>>month>>day;
}
};
class student                                  ////////////学生类
{
public :
	string xm,kc[5];
	int bj,xh,cj[5];
	sj time;
	void sr()                   //////初始化输入学生信息
	{cout<<"请输入学号";
		cin>>xh;
		 system("cls");
		cout<<"请输入姓名";
		cin>>xm;
		 system("cls");
		 cout<<"请输入入学日期中间用空格隔开";
		 time.shuru();
		  system("cls") ;
		cout<<"请输入班级";
		cin>>bj;
		 system("cls");
		 cout<<"请输入课程（5门）中间用空格隔开";
		for(int i=0;i<5;i++)
			cin>>kc[i];
		system("cls");}
		  void chengji()                         ///////成绩录入
		  {int i;
			  for(i=0;i<5;i++)
			  {cout<<"请输入"<<kc[i]<<"的成绩"<<endl;
			  cin>>cj[i];}
		  }
student chazhao(student t);        ////////////////////////////这个地方明明定义了为何还是报错
/*	void shuruchengji()     
	{int i;
		for(i=0;i<5;i++)
	{
			cout<<"请输入"<<kc[i]<<"的成绩";
				cin>>cj[i];
		}
	}*/
};
string mima()                ////////初始化设置密码
{cout<<"请设置密码:";
string mm1,mm2;
char ch;
 while ((ch=_getch())!=13)
 {
  mm1+=ch;
  cout<<"*";
 }
 	 cout<<endl;
cout<<"请再次确认密码:";
while ((ch=_getch())!=13)
 {
  mm2+=ch;
  cout<<"*";
 }
	 system("cls");
if(mm1==mm2)
return mm1;
else
mima();
}
int denglu(string mm)              /////////登陆程序
{
	cout<<"请输入登陆密码：";
	string mm1;
	char ch;
 while ((ch=_getch())!=13)
 {
  mm1+=ch;
  cout<<"*";
 }	
 system("cls");
	if(mm==mm1)
		return 1;
	else
	{cout<<"密码错误，您还有两次机会，请重试";
     while ((ch=_getch())!=13)
 {
  mm1+=ch;
  cout<<"*";
 }
	 	 system("cls");
	 if(mm==mm1)
		return 1;
	else
	{cout<<"密码错误，您还有一次机会，请重试";
     while ((ch=_getch())!=13)
 {
  mm1+=ch;
  cout<<"*";
 }
	 	 system("cls");
	 if(mm==mm1)
		return 1;
	else
	{cout<<"密码错误，请明天再试";
	return 0;}
	}
	}
}
	int main()                        ////主函数..................................................................................
	{int n,i,xh;
	string mm;
	student stu[500];
	mm=mima();
	i=denglu(mm);
	if(i)
	{	cout<<"请输入学生人数: ";
	cin>>n;
		 system("cls");
	for(i=0;i<n;i++)
		stu[i].sr();
	int a;
	bangzhu();
		while(cin>>a)
		{if(a==0)
		break;
		else
		{
			switch(a)
		{case 1: (n++,stu[n].sr());break;
			case 2:  {for(i=0;i<n;i++)cout<<stu[i].xm;stu[i].chengji();}break;
			case 3: cin>>xh;for(i=0;i<n;i++) if(stu[i].xh==xh) stu[i]=chazhao(stu[i]);break;
		case 9:bangzhu();break;}}

	}}
return 0;
	}
void bangzhu()                         //操作指令提示
{  cout<<"请输入以下指令"<<endl<<endl; 
	
	cout<<"    1.添加学生              " <<endl;
    cout<<"============================"<<endl;
	cout<<"    2.成绩录入        "<<endl;
	cout<<"============================"<<endl;
	cout<<"    3.输入学号修改学生信息        "<<endl;
	cout<<"============================"<<endl;
	cout<<"    4,"<<endl;
	cout<<"============================"<<endl;
	cout<<"    5,"<<endl;
	cout<<"============================"<<endl;
	cout<<"    9."<<endl;
    cout<<"============================"<<endl;
    cout<<"    0.结束本程序          "<<endl ;
	cout<<"============================"<<endl;
}
student chazhao(student t)
{cout<<"修改姓名请输入1，修改入学时间请输入2，修改班级请输入3."<<endl;
cout<<"修改课程请输入4，修改成绩请输入5";
int a,i;
cin>>a;
switch(a)
{case 1:cin>>t.xm;break;
case 2:cin>>t.time.year>>t.time.month>>t.time.day;break;
case 3:cin>>t.bj;break;
case 4:for(i=0;i<5;i++) cin>>t.kc[i];break;
case 5:for(i=0;i<5;i++) {cout<<t.xm;t.chengji();}break;
	   }
return t;

}