C++ Program on Polymorphism

      #include <iostream>
   using namespace std;
   class Shape
   {
     protected:
       int width, height;
     public:
       Shape( int a=0, int b=0)
       {
         width = a;
         height = b;
       }
       int area()
       {
         cout << "Parent class area :" <<endl;
         return 0;
       }
   };
   class Rectangle: public Shape
   {
     public:
       Rectangle( int a=0, int b=0)
       {
         Shape(a, b);
       }
       int area ()
       {
         cout << "Rectangle class area :" <<endl;
         return (width * height);
       }
   };
   class Triangle: public Shape
   {
     public:
       Triangle( int a=0, int b=0)
       {
         Shape(a, b);
       }
       int area ()
       {
         cout << "Rectangle class area :"<<endl;
         return (width * height / 2);
       }
   };
   // Main function for the program
   int main( )
   {
     Shape *shape;
     Rectangle rec(10,7);
     Triangle tri(10,5);
     // store the address of Rectangle
     shape = &rec;
     // call rectangle area.
     shape->area();
     // store the address of Triangle
     shape = &tri;
     // call triangle area.
     shape->area();
     return 0;
   }