#include <iostream>
using namespace std;

class Device {
    public:
        int serial_number = 12345678;

        void turn_on() {
            cout << "Device is on" << endl;
        }
};

class Computer: private Device {
    public:
        void say_hello() {
            turn_on();
            cout << "Welcome to Windows 95!" << endl;
        }
};

int main() {
    Device Unknown_device;
    Computer my_computer;

    cout << "\t Unknown Device" << endl;
    cout << "Serial number is: "<< Unknown_device.serial_number << endl;
    Unknown_device.turn_on();

    // cout << "Serial number is: " << my_computer.serial_number << endl;
    // my_computer.turn_on();
    // will cause compile time error

    cout << "\t My computer" << endl;
    my_computer.say_hello();

    return 0;
}