C++ term.

An abstract class is a class containing at least one pure virtual function. As a result, no objects of the class can exist. One will have to derive classes from the abstract base class. These classes must then overload all the pure virtual functions of the base class in order not to be abstract as well.

Why bother?, you might ask. Well - I just started using the technique this week, after having programmed in C++ for 4 years. I use it, because: Skipping the first two statements above, I conclude that I obtain a more readable, more structured end class hierachy.