I could not understand why to use a pure virtual function to make the class an abstract class instead of using only a virtual function

As far as i know, a class ia abstract when contain one pure virtual function.

The purpose of pure virtual function is this function may redefined my your later derived class function.

It seems unpractical for me because i also cannot see this usage of this features because this is out of my knowledge.

Polymorphism is the most difficult part of OOP.

http://en.wikipedia.org/wiki/Polymor...ed_programming



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