自己写的一个简单学生信息管理，高手可以给我看看哪里出错了吗？

#include <iostream>
#include <string>
#include <fstream>

using namespace std;

class Student{
private:
    string NUM;
    string NAME;
    double SCORE;
    friend void OUTPUT();
public:
    Student(){}
    Student(string num,string name,double score){
        NUM = num;
        NAME = name;
        SCORE = score;
    }
    void setStudent(string num,string name,double score){
        NUM = num;
        NAME = name;
        SCORE = score;
    }
    void display(){
        cout<<NUM<<"\t"<<NAME<<"\t"<<SCORE<<endl;
    }
    double getSCORE(){return SCORE;}
    string getNUM(){return NUM;}
};
void WELCOM(){
    cout<<"***************************************"<<endl;
    cout<<"***************************************"<<endl;
    cout<<"**                                   **"<<endl;
    cout<<"**                                   **"<<endl;
    cout<<"**-------------欢迎使用--------------**"<<endl;
    cout<<"**                                   **"<<endl;
    cout<<"**                                   **"<<endl;
    cout<<"***************************************"<<endl;
    cout<<"***************************************"<<endl;
    cout<<"添加学生信息----add"<<endl;
    cout<<"查看学生信息----look"<<endl;
    cout<<"退出系统----exit"<<endl;
}
void INPUT(){
    int n;
    string num,name;
    double score;
    cout<<"请输入这次要存入学生的人数：";
    cin>>n;
    Student stu[n];
    ofstream ofile("student.dat",ios::app|ios::binary);
    ofile.seekp(0,ios::end);
    for(int i=0;i<n;i++){
            cout<<"编号:";cin>>num;
            cout<<"姓名:";cin>>name;
            cout<<"成绩:";cin>>score;
        stu[i].setStudent(num,name,score);
        ofile.write((char *)&stu[i],sizeof(stu[i]));
    }
    cout<<"已存入这"<<n<<"个学生的信息,请继续操作..."<<endl;
    ofile.close();
}
void OUTPUT(){
    char bol;
    string num;
    Student temp;
    ifstream ifile("student.dat",ios::in|ios::binary);
    ifile.seekg(0,ios::beg);
    cout<<"按编号查询(f)或显示全部(a)"<<endl;
    cin>>bol;
    if(bol=='f'){
        cout<<"请输入学生编号:";
        cin>>num;
        ifile.read((char *)&temp,sizeof(temp));
        while(!ifile.eof()){
            if(temp.NUM==num){temp.display();}
            ifile.read((char *)&temp,sizeof(temp));
        }
    }
    else if(bol=='a'){
        ifile.read((char *)&temp,sizeof(temp));
        cout<<"1"<<endl;
        temp.display();
        cout<<"2"<<endl;
        while(!ifile.eof()){
            temp.display();
            ifile.read((char *)&temp,sizeof(temp));
        }
    }
    ifile.close();
}
int main(){
    WELCOM();
    bool Judge=true;
    string Cal;
    while(Judge){
        cin>>Cal;
        if(Cal=="add"){INPUT();}
        else if(Cal=="look"){OUTPUT();}
        else if(Cal=="exit"){Judge=false;}
    }
    return 0;
}