Overriding vs Virtual

Question

What is the purpose of using the reserved word virtual in front of functions? If I want a child class to override a parent function, I just declare the same function such as

Answer 1

Try it with:

Parent *a = new Child();
Parent *b = new Parent();

a->say();
b->say();

Without virtual, both with print '1'. Add virtual, and the child will act like a Child, even though it's being referred to via a pointer to a Parent.