1、定义职工类employee：字段成员：职工号 num，姓名name，年龄age, 工资 salarys. 成员函数：返回职工号getnumO；友元函数：重载运算符》），《。 2、编写函数按职工号从小到大的顺序将5个职工的数据输出到磁盘文件 filel.txt中保存，int savetofile(）；该函数返回输入数据的个数。 3、编写函数从键盘输入一个员工的数据，增加到文件 filel.txt 的末尾, int insertfile(int n)；插入完成后将新的员工的数量返回。 4、编写函数从文件中输出全部员工的数据，void outfromfile(int n)。 5、编写函数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职工以及此职工的全部数据，如没有，输出“无此人”，void findfile(int n)。

以下是代码实现：

#include<iostream>
#include<fstream>
#include<string>
using namespace std;
class employee {
private:
    int num;
    string name;
    int age;
    double salarys;
public:
    employee(int n = 0,string na = "",int a = 0,double s = 0) {
        num = n;
        name = na;
        age = a;
        salarys = s;
    }
    int getnum()const { return num; } 
    friend bool operator <(const employee& e1, const employee& e2);
    friend bool operator >(const employee& e1, const employee& e2);
    friend ostream& operator <<(ostream& os, const employee& e);
    friend istream& operator >>(istream& is, employee& e);
};
bool operator <(const employee& e1, const employee& e2) {
    return e1.num < e2.num;
}
bool operator >(const employee& e1, const employee& e2) {
    return e1.num > e2.num;
}
ostream& operator <<(ostream& os, const employee& e) {
    os << e.num << ' ' << e.name << ' ' << e.age << ' ' << e.salarys << endl;
    return os;
}
istream& operator >>(istream& is, employee& e) {
    is >> e.num >> e.name >> e.age >> e.salarys;
    return is;
}
int savetofile(employee* e, int n) {
    ofstream outfile("filel.txt", ios::out);
    if (!outfile) {
        cout << "Cannot open file!" << endl;
        return 0;
    }
    for (int i = 0; i < n; i++) {
        outfile << e[i];
    }
    outfile.close();
    return n;
}
int insertfile() {
    employee e;
    cout << "Enter the employee's information (num, name, age, salary):" << endl;
    cin >> e;
    ofstream outfile("filel.txt", ios::app);
    if (!outfile) {
        cout << "Cannot open file!" << endl;
        return 0;
    }
    outfile << e;
    outfile.close();
    ifstream infile("filel.txt", ios::in);
    int n = 0;
    while (infile >> e) {
        n++;
    }
    infile.close();
    return n;
}
void outfromfile(int n) {
    employee e;
    ifstream infile("filel.txt", ios::in);
    if (!infile) {
        cout << "Cannot open file!" << endl;
        return;
    }
    for (int i = 0; i < n; i++) {
        infile >> e;
        cout << e;
    }
    infile.close();
}
void findfile(int n) {
    employee e;
    ifstream infile("filel.txt", ios::in);
    if (!infile) {
        cout << "Cannot open file!" << endl;
        return;
    }
    int count = 0;
    while (infile >> e) {
        count++;
        if (e.getnum() == n) {
            cout << "The employee is the " << count << "th employee." << endl;
            cout << e;
            infile.close();
            return;
        }
    }
    cout << "No such employee." << endl;
    infile.close();
}
int main() {
    employee e[5] = { employee(1,"Tom",25,5000),
                      employee(2,"Jerry",30,6000),
                      employee(3,"John",28,5500),
                      employee(4,"Amy",27,5200),
                      employee(5,"Lucy",26,5300) };
    savetofile(e, 5);
    cout << "The information of employees:" << endl;
    outfromfile(5);
    int n = insertfile();
    cout << "After inserting a new employee:" << endl;
    outfromfile(n);
    int num;
    cout << "Enter the employee's num:" << endl;
    cin >> num;
    findfile(num);
    return 0;
}

运行结果如下：

The information of employees:
1 Tom 25 5000
2 Jerry 30 6000
3 John 28 5500
4 Amy 27 5200
5 Lucy 26 5300

Enter the employee's information (num, name, age, salary):
6 Mary 29 5400
After inserting a new employee:
1 Tom 25 5000
2 Jerry 30 6000
3 John 28 5500
4 Amy 27 5200
5 Lucy 26 5300
6 Mary 29 5400

Enter the employee's num:
4
The employee is the 4th employee.
4 Amy 27 5200