Node Class in C++

A node class is a class that,
  > relies on the base class for services and implementation,
  > provides a wider interface to the 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.