Why do we need to store a null value in vTable for a pure virtual function?

Answer 1

That’s to make it so you can’t call on the function unless it’s defined else where.

Answer 2

if we can't create an object of a class which has pure virtual function, why do we need to store a null value in vTable, wasting memory?

Answer 3

It’s a base for the inherited classes to use that method.