C++ programming to virtual function

#include <iostream>
using namespace std;
class B
{
    public:
     virtual void display()      /* Virtual function */
         { cout<<"Content of base class.\n"; }
};

class D1 : public B
{
    public:
       void display()
         { cout<<"Content of first derived class.\n"; }
};

class D2 : public B
{
    public:
       void display()
         { cout<<"Content of second derived class.\n"; }
};

int main()
{
    B *b;
    D1 d1;
    D2 d2;

/* b->display();  // You cannot use this code here because the function of base class is virtual. */

    b = &d1;
    b->display();   /* calls display() of class derived D1 */
    b = &d2;          
    b->display();   /* calls display() of class derived D2 */
    return 0;
}
*****************************************
Output
Content of first derived class.
Content of second derived class.
////////////////////////////////////////////////////////////////////////////
Virtual Function in C++ Programming
If there are member function with same name in derived classes, virtual functions gives programmer capability to call member function of different class by a same function call depending upon different context. This feature in C++ programming is known as polymorphism which is one of the important feature of OOP.