用c++语言编写一个学生成绩管理系统，实现学生基本信息（包括学号、姓名、数学成绩、英语成绩、计算机课成绩）的录入并用类进行封装、计算学生的总成绩和平均成绩、学生基本信息的删除、学生基本信息的查询、学生基本信息的修改，并且实现对学生基本信息的存盘（保存为文本文件）和读盘

好的，以下是一个简单的学生成绩管理系统的C++代码，实现了您要求的功能：

#include <iostream>
#include <fstream>
#include <vector>
#include <string>

using namespace std;

// 学生类
class Student {
public:
    int id;
    string name;
    float mathScore;
    float englishScore;
    float computerScore;

    // 构造函数
    Student(int id, string name, float mathScore, float englishScore, float computerScore) {
        this->id = id;
        this->name = name;
        this->mathScore = mathScore;
        this->englishScore = englishScore;
        this->computerScore = computerScore;
    }

    // 计算总成绩
    float getTotalScore() {
        return mathScore + englishScore + computerScore;
    }

    // 计算平均成绩
    float getAverageScore() {
        return getTotalScore() / 3;
    }

    // 输出学生信息
    void printInfo() {
        cout << "学号：" << id << "，姓名：" << name << "，数学成绩：" << mathScore
            << "，英语成绩：" << englishScore << "，计算机课成绩：" << computerScore
            << "，总成绩：" << getTotalScore() << "，平均成绩：" << getAverageScore() << endl;
    }

    // 将学生信息写入文件
    void writeToFile(ofstream& out) {
        out << id << " " << name << " " << mathScore << " " << englishScore << " " << computerScore << endl;
    }
};

// 学生管理类
class StudentManager {
public:
    vector<Student> students;

    // 添加学生信息
    void addStudent(int id, string name, float mathScore, float englishScore, float computerScore) {
        Student student(id, name, mathScore, englishScore, computerScore);
        students.push_back(student);
    }

    // 删除学生信息
    void deleteStudent(int id) {
        for (vector<Student>::iterator it = students.begin(); it != students.end(); ++it) {
            if (it->id == id) {
                students.erase(it);
                break;
            }
        }
    }

    // 查询学生信息
    void queryStudent(int id) {
        for (vector<Student>::iterator it = students.begin(); it != students.end(); ++it) {
            if (it->id == id) {
                it->printInfo();
                break;
            }
        }
    }

    // 修改学生信息
    void modifyStudent(int id, string name, float mathScore, float englishScore, float computerScore) {
        for (vector<Student>::iterator it = students.begin(); it != students.end(); ++it) {
            if (it->id == id) {
                it->name = name;
                it->mathScore = mathScore;
                it->englishScore = englishScore;
                it->computerScore = computerScore;
                break;
            }
        }
    }

    // 从文件中读取学生信息
    void readFromFile(string filename) {
        ifstream in(filename);
        if (!in) {
            cout << "打开文件失败！" << endl;
            return;
        }

        int id;
        string name;
        float mathScore, englishScore, computerScore;
        while (in >> id >> name >> mathScore >> englishScore >> computerScore) {
            addStudent(id, name, mathScore, englishScore, computerScore);
        }

        in.close();
    }

    // 将学生信息写入文件
    void writeToFile(string filename) {
        ofstream out(filename);
        if (!out) {
            cout << "打开文件失败！" << endl;
            return;
        }

        for (vector<Student>::iterator it = students.begin(); it != students.end(); ++it) {
            it->writeToFile(out);
        }

        out.close();
    }
};

int main() {
    StudentManager manager;
    manager.readFromFile("students.txt");

    while (true) {
        cout << "请选择操作：1.添加学生信息 2.删除学生信息 3.查询学生信息 4.修改学生信息 5.保存学生信息 6.退出" << endl;
        int option;
        cin >> option;

        if (option == 1) {
            int id;
            string name;
            float mathScore, englishScore, computerScore;
            cout << "请输入学号、姓名、数学成绩、英语成绩、计算机课成绩：" << endl;
            cin >> id >> name >> mathScore >> englishScore >> computerScore;
            manager.addStudent(id, name, mathScore, englishScore, computerScore);
            cout << "添加成功！" << endl;
        } else if (option == 2) {
            int id;
            cout << "请输入要删除的学生学号：" << endl;
            cin >> id;
            manager.deleteStudent(id);
            cout << "删除成功！" << endl;
        } else if (option == 3) {
            int id;
            cout << "请输入要查询的学生学号：" << endl;
            cin >> id;
            manager.queryStudent(id);
        } else if (option == 4) {
            int id;
            string name;
            float mathScore, englishScore, computerScore;
            cout << "请输入要修改的学生学号、姓名、数学成绩、英语成绩、计算机课成绩：" << endl;
            cin >> id >> name >> mathScore >> englishScore >> computerScore;
            manager.modifyStudent(id, name, mathScore, englishScore, computerScore);
            cout << "修改成功！" << endl;
        } else if (option == 5) {
            manager.writeToFile("students.txt");
            cout << "保存成功！" << endl;
        } else if (option == 6) {
            break;
        } else {
            cout << "输入有误，请重新输入！" << endl;
        }
    }

    return 0;
}

该程序中，Student类表示学生，包含学号、姓名、数学成绩、英语成绩、计算机课成绩等信息，并封装了计算总成绩、平均成绩、输出学生信息、将学生信息写入文件等方法；StudentManager类表示学生管理器，包含了添加、删除、查询、修改、从文件中读取、将学生信息写入文件等方法。主函数中通过循环实现了不断选择操作的功能。