用C++编写程序实现以下功能： (1)按职工号由小到大的顺序将5个员工的数据(包括号码、姓名、年龄、工资)输出到磁盘文件中保存。 (2)从键盘输入两个员工的数据(职工号大于已有的职工号)，增加到文件的末尾。 (3)输出文件中全部职工的数据。 (4)从键盘输入一个号码，从文件中查找有无此职工号，如有则显示此职工是第几个只工以及此职工的全部数据。如没有，就输出“无此人”。可以反复多次查询，如果输入找的职工号为0，就结束查询。

以下是使用C++实现的程序，实现以上功能：

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

using namespace std;

// 员工结构体
struct Employee {
    int id;       // 职工号
    string name;  // 姓名
    int age;      // 年龄
    float salary; // 工资
};

// 比较函数，用于按职工号排序
bool cmp(const Employee& a, const Employee& b) {
    return a.id < b.id;
}

// 将员工数据写入文件
void writeToFile(Employee employees[], int count) {
    // 按职工号排序
    sort(employees, employees + count, cmp);

    // 写入文件
    ofstream outFile("employee.txt");
    if (outFile.is_open()) {
        for (int i = 0; i < count; i++) {
            outFile << employees[i].id << " " << employees[i].name << " " << employees[i].age << " " << employees[i].salary << endl;
        }
        outFile.close();
    }
}

// 从文件中读取员工数据
int readFromFile(Employee employees[]) {
    int count = 0;
    ifstream inFile("employee.txt");
    if (inFile.is_open()) {
        while (!inFile.eof()) {
            inFile >> employees[count].id >> employees[count].name >> employees[count].age >> employees[count].salary;
            count++;
        }
        inFile.close();
    }
    return count;
}

// 增加员工数据
void addEmployee(Employee employees[], int& count) {
    cout << "请输入新员工的职工号：" << endl;
    int id;
    cin >> id;

    // 查找职工号是否已存在
    bool found = false;
    for (int i = 0; i < count; i++) {
        if (employees[i].id == id) {
            found = true;
            break;
        }
    }

    // 如果职工号已存在，输出错误信息
    if (found) {
        cout << "职工号已存在！" << endl;
        return;
    }

    // 输入其他信息
    cout << "请输入新员工的姓名：" << endl;
    string name;
    cin >> name;
    cout << "请输入新员工的年龄：" << endl;
    int age;
    cin >> age;
    cout << "请输入新员工的工资：" << endl;
    float salary;
    cin >> salary;

    // 增加新员工数据
    employees[count].id = id;
    employees[count].name = name;
    employees[count].age = age;
    employees[count].salary = salary;
    count++;

    // 写入文件
    writeToFile(employees, count);

    cout << "新员工数据已添加。" << endl;
}

// 显示所有员工数据
void showAllEmployees(Employee employees[], int count) {
    cout << "职工号\t姓名\t年龄\t工资" << endl;
    for (int i = 0; i < count; i++) {
        cout << employees[i].id << "\t" << employees[i].name << "\t" << employees[i].age << "\t" << employees[i].salary << endl;
    }
}

// 查找员工数据
void searchEmployee(Employee employees[], int count) {
    cout << "请输入要查找的职工号：" << endl;
    int id;
    cin >> id;

    // 查找职工号是否存在
    int index = -1;
    for (int i = 0; i < count; i++) {
        if (employees[i].id == id) {
            index = i;
            break;
        }
    }

    // 输出查找结果
    if (index == -1) {
        cout << "无此人。" << endl;
    } else {
        cout << "第" << index + 1 << "个职工" << endl;
        cout << "职工号\t姓名\t年龄\t工资" << endl;
        cout << employees[index].id << "\t" << employees[index].name << "\t" << employees[index].age << "\t" << employees[index].salary << endl;
    }
}

int main() {
    Employee employees[10];
    int count = readFromFile(employees);

    int choice;
    do {
        cout << "请选择操作：" << endl;
        cout << "1. 输出所有员工数据到文件" << endl;
        cout << "2. 增加员工数据" << endl;
        cout << "3. 显示所有员工数据" << endl;
        cout << "4. 查找员工数据" << endl;
        cout << "0. 退出程序" << endl;
        cin >> choice;

        switch (choice) {
            case 1:
                writeToFile(employees, count);
                break;
            case 2:
                addEmployee(employees, count);
                break;
            case 3:
                showAllEmployees(employees, count);
                break;
            case 4:
                searchEmployee(employees, count);
                break;
            case 0:
                break;
            default:
                cout << "无效的选择！" << endl;
                break;
        }
    } while (choice != 0);

    return 0;
}

注意：以上程序使用了文件读写操作，需要在程序所在的目录下新建一个名为“employee.txt”的文件，用于存储员工数据。