⑶选择“添加学生成绩记录”后，输入要插入记录的位置。按程序提示依次输入学号，姓名，性别，成绩，插入记录成功。若追加记录，可连续添加。 ⑷选择“显示学生成绩记录”，显示学生成绩表中已有的学生记录的个数，并显示出各个学生记录的相关信息。 ⑸选择“查找学生成绩记录”，按提示输入要查找的学生的学号，输入学号，若该学号存在，则输出相应的学生记录，如该学号不存在，则按任意键返回主菜单。 ⑹选择“删除学生成绩记录”，按提示输入要删除的学生的学号，输入学号，若该学号存在，则删除相应的学生记录，如果该学号不存在，则按任意键返回主菜单。 ⑺选择“保存学生成绩记录”，系统会将已有的学生记录保存在默认的文件名为fname.txt的文件中。 ⑻选择“导出学生成绩记录”，系统会提示输入文件名，输入默认的文件名为fname.txt，则可将文件中的相关信息导出。c++代码

下面是一个简单的学生成绩管理系统的C++代码：

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

using namespace std;

struct Student {
    string id; // 学号
    string name; // 姓名
    string gender; // 性别
    float score; // 成绩
};

void addStudent(Student students[], int& count) {
    int pos;
    cout << "请输入要插入的位置：";
    cin >> pos;
    if (pos < 1 || pos > count + 1) {
        cout << "位置不合法！" << endl;
        return;
    }
    Student stu;
    cout << "请输入学号：";
    cin >> stu.id;
    cout << "请输入姓名：";
    cin >> stu.name;
    cout << "请输入性别：";
    cin >> stu.gender;
    cout << "请输入成绩：";
    cin >> stu.score;
    if (pos == count + 1) {
        students[count] = stu;
    } else {
        for (int i = count; i >= pos; i--) {
            students[i] = students[i - 1];
        }
        students[pos - 1] = stu;
    }
    count++;
    cout << "插入记录成功！" << endl;
}

void showStudents(Student students[], int count) {
    cout << "学生记录个数：" << count << endl;
    for (int i = 0; i < count; i++) {
        cout << "学号：" << students[i].id << "\t姓名：" << students[i].name << "\t性别：" << students[i].gender << "\t成绩：" << students[i].score << endl;
    }
}

void searchStudent(Student students[], int count) {
    string id;
    cout << "请输入要查找的学号：";
    cin >> id;
    for (int i = 0; i < count; i++) {
        if (students[i].id == id) {
            cout << "学号：" << students[i].id << "\t姓名：" << students[i].name << "\t性别：" << students[i].gender << "\t成绩：" << students[i].score << endl;
            return;
        }
    }
    cout << "该学号不存在！" << endl;
}

void deleteStudent(Student students[], int& count) {
    string id;
    cout << "请输入要删除的学号：";
    cin >> id;
    for (int i = 0; i < count; i++) {
        if (students[i].id == id) {
            for (int j = i + 1; j < count; j++) {
                students[j - 1] = students[j];
            }
            count--;
            cout << "删除成功！" << endl;
            return;
        }
    }
    cout << "该学号不存在！" << endl;
}

void saveStudents(Student students[], int count) {
    ofstream outfile("fname.txt");
    if (!outfile.is_open()) {
        cout << "文件打开失败！" << endl;
        return;
    }
    outfile << "学号\t姓名\t性别\t成绩" << endl;
    for (int i = 0; i < count; i++) {
        outfile << students[i].id << "\t" << students[i].name << "\t" << students[i].gender << "\t" << students[i].score << endl;
    }
    outfile.close();
    cout << "保存成功！" << endl;
}

void exportStudents(Student students[], int count) {
    string filename;
    cout << "请输入导出文件名：";
    cin >> filename;
    ofstream outfile(filename);
    if (!outfile.is_open()) {
        cout << "文件打开失败！" << endl;
        return;
    }
    outfile << "学号\t姓名\t性别\t成绩" << endl;
    for (int i = 0; i < count; i++) {
        outfile << students[i].id << "\t" << students[i].name << "\t" << students[i].gender << "\t" << students[i].score << endl;
    }
    outfile.close();
    cout << "导出成功！" << endl;
}

int main() {
    Student students[100];
    int count = 0;
    int choice;
    while (true) {
        cout << "1. 添加学生成绩记录" << endl;
        cout << "2. 显示学生成绩记录" << endl;
        cout << "3. 查找学生成绩记录" << endl;
        cout << "4. 删除学生成绩记录" << endl;
        cout << "5. 保存学生成绩记录" << endl;
        cout << "6. 导出学生成绩记录" << endl;
        cout << "0. 退出程序" << endl;
        cout << "请选择：";
        cin >> choice;
        switch (choice) {
            case 1:
                addStudent(students, count);
                break;
            case 2:
                showStudents(students, count);
                break;
            case 3:
                searchStudent(students, count);
                break;
            case 4:
                deleteStudent(students, count);
                break;
            case 5:
                saveStudents(students, count);
                break;
            case 6:
                exportStudents(students, count);
                break;
            case 0:
                return 0;
            default:
                cout << "选择错误！" << endl;
                break;
        }
    }
    return 0;
}

该程序使用结构体存储学生信息，可以添加、显示、查找、删除、保存和导出学生成绩记录。其中保存和导出功能将学生记录写入文件中。