Difference between redefining and overriding a function

Question

Suppose I have class A with a virtual function F():

class A {     virtual void F()     {         // Do something     }; }; 

And I have another class B which inherits A and redefines F():

class B : A {     void F()     {         // Do something     }; }; 

And a different class C which also inherits A but overrides F():

class C : A {     void F() override     {         // Do something     }; }; 

What is the difference between F() in classes B and C?

Answer 1

Both are overrides.

When you use the keyword override you ensure a compilation failure if it should happen to not be an override.

And that's good practice.

Answer 2

Both B::f() and C::f() are overrides and they are exactly the same.

override is essentially a compile-time advisory term that will cause a compilation error if the function does not override one in a base class.

This can help program stability: if the name and parameter types to A::f() are changed, then a compile error will result.