这个程序编译能通过，但是运行后，在D盘建立的TXT文档是空的。没有预期输入的数据

如题，希望大家帮下忙；
#include <iostream>
#include <fstream>
#include <ostream>
using namespace std;
class cstudent
{
    private:
        int num;            //学号
        char name[3];        //姓名
        char sex;            //性别,男为M，女为F
        int age;            //年龄
        int mscore;            //数学成绩
        int cscore;            //计算机成绩
        int escore;            //英语成绩
        float ascore;        //平均成绩
        float all;            //总成绩
    public:
        void get();                        //从文件中读取学生信息
        void send();                    //向文件中输入学生信息
        void output1();                    //输出信息
        void fun();                        //计算平均成绩和总成绩
void input();                    //输入数据
        
};ofstream outfile;
ifstream infile;

void cstudent::fun()
{   
    all=mscore+cscore+escore;cout<<"总成绩："<<all<<endl;
    ascore=all/3;cout<<"平均成绩："<<ascore<<endl;
}

void cstudent::send()
{

    outfile<<"学号:";            outfile<<num;        outfile<<endl;
    outfile<<"姓名:";            outfile<<name;        outfile<<endl;
    outfile<<"性别:";            outfile<<sex;        outfile<<endl;
    outfile<<"年龄:";            outfile<<age;        outfile<<endl;
    outfile<<"数学成绩:";        outfile<<mscore;    outfile<<endl;
    outfile<<"计算机成绩:";        outfile<<cscore;    outfile<<endl;
    outfile<<"英语成绩:";        outfile<<escore;    outfile<<endl;
    outfile<<endl;
}

void cstudent::output1()
{
    cout<<"学号:";            cout<<num;        cout<<endl;
    cout<<"姓名:";            cout<<name;    cout<<endl;
    cout<<"性别:";            cout<<sex;        cout<<endl;
    cout<<"年龄:";            cout<<age;        cout<<endl;
    cout<<"数学成绩:";            cout<<mscore;    cout<<endl;
    cout<<"计算机成绩:";            cout<<cscore;    cout<<endl;
    cout<<"英语成绩:";            cout<<escore;    cout<<endl;
}



void cstudent::input()
{
    cout<<"学号:";            cin>>num;        
    cout<<"姓名:";            cin>>name;   
    cout<<"性别:";            cin>>sex;        
    cout<<"年龄:";            cin>>age;        
    cout<<"数学成绩:";            cin>>mscore;   
    cout<<"计算机成绩:";            cin>>cscore;   
    cout<<"英语成绩:";            cin>>escore;   
}




void main()
{   
    cstudent a[2];
    ofstream outfile("D:\\学生信息.txt",ios::out);
        for (int i=0;i<2;i++)
            {
            a[i].input();
            a[i].send();
            cout<<endl;
            }
    outfile.close();
    ifstream infile("D:\\学生信息.txt",ios::in);
        for (i=0;i<2;i++)
        {
            cout<<"No."<<i+1<<endl;
            a[i].output1();
            a[i].fun();
            cout<<endl;
        }

}