Using Class with Pointer Object in C++ Example Code

How to use pointer to class object and Using Class with Pointer Object Example Code 

1. What will be the output of this code?

class CPolygon {

  protected:

    int width, height;

  public:

    void set_values (int a, int b)

      { width=a; height=b; }

    virtual int area (void) =0;

    void printarea (void)

      { cout << this->area() << endl; }

  };

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 () {

  CPolygon * ppoly1 = new CRectangle;

  CPolygon * ppoly2 = new CTriangle;

  ppoly1->set_values (4,5);

  ppoly2->set_values (4,5);

  ppoly1->printarea();

  ppoly2->printarea();

  delete ppoly1;

  delete ppoly2;

  system("pause");

  return 0;

}

20 10