keyword for overriding

keywords for overriding.

1)Virtual=overridable.

By default all methods are overridable.

2)Override=overrides.

If we are using override keyword with a function
then this override keyword also more functions as virtual.

3)Sealed=not overidable.

4)Abstract=must overridable.

*Abstract method must contain in abstract class.

*A method followed by abstract keyword is known as
abstract method.

It has following limitation.

1. Abstract method must contain in abstract class.

2. Abstract method do not contain definition.It
contain only signature of method.