27. Using virtual functions

• Once a function is virtual in some base class, it is virtual in all descendant classes, whether labeled so or not:

  
          class Shape {
          public:
              virtual void draw();
  
          };//class Shape
  
  
          class Circle : public Shape {
          public:
              void draw(); // Still virtual
  
          };//class Circle
  
  

• Use the virtual label in derived classes to avoid confusion!