16_1.cpp

//pointers to base class
#include <iostream>
using namespace std;

class CPolygon
{
      protected:
                int width, height;
      public:
             void set_values(int a, int b)
             {
                  width = a;
                  height = b;
             }
};

class CRectangle: public CPolygon
{
      public:
             int area(void)
             {
                 return (width*height);
             }
};

class CTriangle: public CPolygon
{
      public:
             int area(void)
             {
                 return (width*height/2);
             }
};

int main()
{
    CRectangle rect;
    CTriangle trgl;
    CPolygon *ppoly1 = &rect;
    CPolygon *ppoly2 = &trgl;
    ppoly1->set_values(4,5);
    ppoly2->set_values(4,5);
    cout << rect.area() << endl;
    cout << trgl.area() << endl;
    getchar();
    return 0;
}