C++文件输入输出

首先是输入到文件中

ofstream outfile;
outfile.open(str);   /// str为对应文件的位置 例如 str = "D:\\outfile.dat";
outfile << ....       /// 输入相应的内容到文件中
outfile.close();     /// 关闭文件

接着是从文件中读取内容

ifstream infile;
infile.open(str);   /// str为对应文件的位置 例如 str = "D:\\outfile.dat";
infile >> ....       /// 从文件中读取内容
infile.close();		/// 关闭文件

实际的例子如下

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

int main()
{
    ofstream outfile("D:\\student.dat");
    string name,id;
    int math,eng,computer;
    for (int i = 0; i < 3; i++){
        cout << "输入姓名： ";   cin >> name;
        cout << "输入学号： ";   cin >> id;
        cout << "输入数学成绩: "; cin >> math;
        cout << "输入英语成绩: "; cin >> eng;
        cout << "输入计算机成绩: "; cin >> computer;
        outfile << name << " " << id << " " << math << " " << eng << " " << computer << endl;
    }
    outfile.close();
	
	system("pause");

    system("cls");

	ifstream infile("D:\\student.dat");
    string name,id;
    int math,eng,computer,sum = 0;
    cout << "姓名\t" << "学号\t" << "数学\t" << "英语\t" << "计算机\t" << "总分\t" << endl;
    infile >> name;
    while (!infile.eof()){
        infile >> id >> math >> eng >> computer;
        sum = math + eng + computer;
        cout << name << "\t" << id << "\t" << math << "\t" << eng << "\t" << computer << "\t" << sum << endl;
        infile >> name;
        sum = 0;
    }
    infile.close();
    return 0;
}