• Allows dynamic (run-time) binding
• Otherwise uses static (compile-time) binding

class base // simplest situation
{
public: 
   constructor, destructor
   public members 
   virtual public members
protected: 
   data accessible to derived classes
private: 
   data members
   private members functions 
}

class derived: public base
{
   any members not listed are derived unchanged
   (except constructor, destructor, copy constructor, operator= 
public: 
   constructor, destructor if defaults are not good
   base members to be changed
   new public members 
protected: 
   possible data for classes using this as base
private: 
   additional data members
   additional private members functions
   base member functions to be disabled 
}