The given code defines a base class "Shape" to represent two different derived classes Triangle and Rectangle. Each of these two classes has a member function displayArea()to display the area of relevant shape on the screen and a member function getdata() to initialize base class data members. In case of Triangle class, these two values of base class will treated as base and height whereas in Rectangle these two values of base class will treated as length and breadth of rectangle.

    #include<iostream.h>
    #include<stdio.h>
    #include<conio.h>

    class Shape
    {
     protected :
     double x0, y0;
     public :
     void getdata(double x, double y)
     {
     x0 = x;
     y0 = y;
     }
     virtual void displayArea() = 0;
    };
    class Triangle : public Shape
    {
     public :
     void getdata(double x, double y)
     {
     Shape :: getdata(x,y);
     }
     void displayArea()
     {
     double area = (x0 * y0)/2.0;
     cout << "\n Area of triangle = " << area;
     }
    };
    class Rectangle : public Shape
    {
     public :
     void getdata(double x, double y)
     {
     Shape :: getdata(x,y);
     }
     void displayArea()
     {
     double area = (x0 * y0);
     cout << "\n Area of rectangle = " << area;
     }
    };
    void main()
    {
     Triangle *tptr;
     Rectangle *rptr;
     Shape *sptr[2];
     int i;
     tptr = new Triangle;
     rptr = new Rectangle;
     tptr->getdata(20.0,30.0);
     rptr->getdata(20.0,20.0);
     sptr[0] = tptr;
     sptr[1] = rptr;
     for(i=0; i<2; i++)
     sptr[i]->displayArea();
     getch();
    }