C++ application

#include <iostream>
#include <stdexcept>
#include <exception>
#include <format>
#include <string>

#include "Database.h"
#include "Employee.h"
using namespace std;
using namespace Records;

int displayMenu();
void doHire(Database& db);

void doFire(Database & db);
void doPromote(Database& db);
int main()
{
    Database employeeDB;
    bool done{ false };
    while (!done) {
        int selection{ displayMenu() };
        switch (selection) {
        case 0:
            done = true;
            break;
        case 1:
            doHire(employeeDB);
            break;
        case 2:
            doFire(employeeDB);
            break;
        case 3:
            doPromote(employeeDB);
            break;
        case 4:
            employeeDB.displayAll();
            break;
        case 5:
            employeeDB.displayCurrent();
            break;
        case 6:
            employeeDB.displayFormer();
            break;
        default:
            cerr << "Unknown command." << endl;
            break;
        }
    }
}

int displayMenu()
{
    int selection;
    cout << endl;
    cout << "Employee Database" << endl;
    cout << "-----------------" << endl;
    cout << "1) Hire a new employee" << endl;
    cout << "2) Fire an employee" << endl;
    cout << "3) Promote an employee" << endl;
    cout << "4) List all employees" << endl;
    cout << "5) List all current employees" << endl;
    cout << "6) List all former employees" << endl;
    cout << "0) Quit" << endl;
    cout << endl;
    cout << "---> ";
    cin >> selection;
    return selection;
}