Virtual functions in C++

virtual.cpp

#include <iostream>

using namespace std;

class Base {
public:
    void f1() {
        cout<<"f1 from base class\n";
    }
    void f2() {
        cout<<"f2 from base class\n";
    }
    virtual void f3() {
        cout<<"f3 from derived class\n";
    }
};

class Derived: public Base {
public:
    void f1() {
        cout<<"f1 from derived class\n";
    }
    void f3() {
        cout<<"f3 from derived class\n";
    }
};

int main()
{
   Derived d;
   d.f1();
   d.f2();
   d.f3();
   
   Base *q = new Derived();
   q->f1();
   q->f2();
   q->f3();
   
   return 0;
}

// Output:
// f1 from derived class
// f2 from base class
// f3 from derived class
// f1 from base class
// f2 from base class
// f3 from derived class