1、创建dat/txt文件（若dat文件不存在时）并向其中写入数据

#include <string>
#include <iostream>  
#include <fstream>  
using namespace std;

int main()  
{
    ofstream outfile("E:\\myfile.dat", ofstream::app); 
    //ofstream outfile("E:\\myfile.txt", ofstream::app);  

    string temp = "O \nM \nG \n!";  //写入内容
    if(outfile.is_open())  
    {  
        outfile<<temp<<"\n";
        outfile.close();
    }
    else
    {
        cout<<"can not open the file \n"<<endl;
        return -1;
    }
    return 0;  
}

2、读取dat/txt文件中的数据

#include <string>
#include <iostream>  
#include <fstream>  
using namespace std;

int main()  
{  
    ifstream infile("E:\\myfile.dat");  
    //ifstream infile("E:\\myfile.txt");  

    string temp;
    if (!infile.is_open())
    {  
        cout<<"can not open the file \n"<<endl;
        return -1;
    }
    while(getline(infile,temp))  
    {  
        cout<<temp<<"\n";
    }
    infile.close();
    return 0;  
}