http://en.wikibooks.org/wiki/C%2B%2B_Programming/Classes/Abstract_Classes

gistfile1.cpp

 class DrawableObject 
 {
  public:
    virtual void Draw(GraphicalDrawingBoard&) const = 0; //draw to GraphicalDrawingBoard
 };
 
 class Triangle : public DrawableObject
 {
 public:
   void Draw(GraphicalDrawingBoard&) const; //draw a triangle
 };
 
 class Rectangle : public DrawableObject
 {
 public:
   void Draw(GraphicalDrawingBoard&) const; //draw a rectangle
 };
 
 class Circle : public DrawableObject
 {
 public:
   void Draw(GraphicalDrawingBoard&) const; //draw a circle
 };
 
 typedef std::list<DrawableObject*> DrawableList_t;
 
 DrawableList_t drawableList;
 GraphicalDrawingBoard gdrawb;
 
 drawableList.pushback(new Triangle());
 drawableList.pushback(new Rectangle());
 drawableList.pushback(new Circle());
 
 for(DrawableList_t::const_iterator iter = drawableList.begin(), 
    endIter = drawableList.end();
    iter != endIter;
    ++iter)
 { 
   DrawableObject *object = *iter;
   object->Draw(gdrawb);
 }