Example of pure abstract class in C++

pure_abstract.cpp

#include <iostream>
using namespace std;

class Device {
    public:
        virtual void turn_on() = 0;
};

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

class Laptop: public Device {
    public:
        void turn_on() {
            cout << "Welcome to Windows XP" << endl;
        }
};

int main() {
    Computer my_computer;
    Laptop my_laptop;
    // Device my_device;
    // will cause compile time error

    my_computer.turn_on();
    my_laptop.turn_on();

    return 0;
}