Node class
A node class is a class that,
- relies on the base class for services and implementation,
- provides a wider interface to te users than its base class,
- relies primarily on virtual functions in its public interface
- depends on all its direct and indirect base class
- can be understood only in the context of the base class
- can be used as base for further derivation
- can be used to create objects.
A node class is a class that has added new services or functionality beyond the services inherited from its base class.