文件操作

#include<iostream>
#include<fstream>
#include<windows.h>
using namespace std;
string a,b;
void showmain()
{
    cout<<"用户管理系统"<<endl;
    cout<<"1.用户注册"<<endl;
    cout<<"2.用户登录"<<endl;
    cout<<"0.退出"<<endl;
}
void Register()
{
    ofstream of;
    of.open("f2.txt",ios::app);
    cout<<"请输入用户名："<<endl;
    cin>>a;
    cout<<"请输入密码："<<endl;
    cin>>b;
    of<<a<<" "<<b<<endl;
    of.close();

}
void login()
{
    cout<<"用户登录"<<endl;
    cout<<"用户名:";
    cin>>a;
    cout<<"密码:";
    cin>>b;
    string a1,b1;
    ifstream infile ("f2.txt",ios::in);
    int flag=0;
    while(infile>>a1>>b1&&!flag)
    {
        if(a==a1&&b1==b)
        {
            flag=1;
            cout<<"登陆成功"<<endl;
        }

    }
    if(!flag) cout<<"登陆失败"<<endl;
}
int main()
{
    int flag=1;
    int choose;
    while(flag)
    {
        showmain();
        cin>>choose;
        switch(choose)
        {
        case 1:
            Register();
            break;
        case 2:
            login();
            break;
        case 0:
            flag=0;
            break;
        }
        system("pause");
        system("cls");

    }


    return 0;
}