学生信息存储并读取

比眉伴天荒 2023-07-07 05:53 10阅读 0赞

#include <fstream>
    #include<iostream>
    #include <iomanip>
    using namespace std;
    struct Student          // 学生结构
    {
        
     int Birth;            // 学号
     char name[16];      // 姓名
     float score1;
     float score2;
     float score3;      // 成绩
    };
    int main(void)          // 主函数main()
    {
          
     cout.setf(std::ios::left);
     Student stud[4] = {
         {
        2009101, "李靖", 98,89,56}, {
        2009102, "刘敏", 100,23,25},{
        2009103, "王强", 99,56,89} ,{
        2009104,"小明",97, 78, 84} };   // 定义数组
     fstream iofile("stud.dat", ios::out | ios::binary);// 定义文件对象,这样如果文件不存储将建立一个空文件
     if (!iofile)        // 打开文件失败
     {
        
      cout << "打开文件失败!" << endl;
      exit(1);        // 退出程序
     }
     for (int i = 0; i < 3; i++)
      iofile.write((char*)&stud[i], sizeof(stud));// 写数据到文件中
     iofile.seekp(0 * sizeof(Student), ios::beg);  // 定位于第1个学生数据的起始位置
     for (int i = 0; i < 3; i++)
     {
        
      cout << stud[i].Birth << " " << stud[i].name << " " << stud[i].score1 << " " << stud[i].score2 << " " << stud[i].score3
       << endl;    // 显示学生信息
     }
     cout << endl;
     stud[1].score2 = 100;        //修改第二个学生的分数
     stud[1].score3 = 100;
     iofile.seekp(1 * sizeof(stud[0]), ios::beg);
     iofile.write((char*)&stud[1], sizeof(stud[1]));
     iofile.seekg(0, ios::beg);
     for (int i = 0; i < 4; i++)
     {
        
      iofile.read((char*)&stud[i], sizeof(stud[i]));    //读出四位学生的数据
      cout << stud[i].Birth << "  " << stud[i].name << "  " << stud[i].score1 << " " << stud[i].score2 << " " << stud[i].score3 << endl;
     }
     cout << endl;
     for (int i = 0; i < 1; i++)
     {
        
      iofile.read((char*)&stud[i], sizeof(stud[i]));
      iofile.seekp(0 * sizeof(stud[i]), ios::beg);
      cout<< stud[i].Birth << "  " << stud[i].name << "  " << stud[i].score1 << " " << stud[i].score2 << " " << stud[i].score3 << endl;
     }
     for (int i = 2; i < 4; i++)
     {
        
      iofile.read((char*)&stud[i], sizeof(stud[i]));
      iofile.seekp(0 * sizeof(stud[i]), ios::beg);
      cout << stud[i].Birth << "  " << stud[i].name << "  " << stud[i].score1 << " " << stud[i].score2 << " " << stud[i].score3 << endl;
     }
     double a = (stud[0].score1 + stud[0].score2 + stud[0].score3) / 3;
     double b = (stud[2].score1 + stud[2].score2 + stud[2].score3) / 3;
     double c = (stud[3].score1 + stud[3].score2 + stud[3].score3) / 3;
     cout << setiosflags(ios::fixed)
      << setprecision(1) << a << endl;
     cout << setiosflags(ios::fixed)
      << setprecision(1) << b << endl;
     cout << setiosflags(ios::fixed)
      << setprecision(1) << c << endl;
     iofile.close();   // 关闭文件
     return 0;
    }