Yes, abstract classes do have vtables, also with pure abstract methods (these can actually be implemented and called), and yes - their constructor does initialize the pure entries to a specified value.

Can abstract class have virtual function?

An abstract class contains at least one pure virtual function. You declare a pure virtual function by using a pure specifier ( = 0 ) in the declaration of a virtual member function in the class declaration.

Does every class have virtual table?

So the short answer is no. The standard does not specify this.