private_access.cpp

#include <iostream>
using namespace std;

class SocialWebsite {
    private:
    protected:
    public:
        virtual void secret() = 0;
};

class Facebook: public SocialWebsite {
    private:
        string password;

        void secret() {
            cout << "password is: " << password << endl;
        }

    public:
        Facebook(string password) {
            this->password = password;
        }
};

int main() {
    Facebook f("12345");
    
    SocialWebsite *sw = &f;
    sw->secret();

    return 0;
}