What does =0 in Pure virtual function means? IS there any specific purpose for that?

poolan

It means it is PURE virtual; this is it's only meaning; do you mean to ask what does Pure virtual function mean? If not, your question has been answered

Regards,
Luci

Using =0 in a function delcaration declares it as a pure virtual function. If you derive a class from a base class that has a pure virtual function in it, then you MUST write that function for the derived class.

Why not -1 or some other number?

Think of function declarations as pointers to the code that executes the body of the function. In fact, this is basically true at the object code level, as each class has a function table that contains pointers to the function code. (Inline expansion is an exception, I suppose.)

Hence, "pure virtual" implies a NULL pointer.

Matthew