REUSEBILITY

once a class has been written created and debugged it can be distributed
to other programemers for use in their own programs>This is called Reusability it is similar to the way a library functions in a procedural language can be incorporated in to the different programes.
However in OOP the concept of the inheritance provides an important extension to the idea reusability .A programmercan take an existing class and without modifying it add additional features and capabilities to this is done by deviring a nerw class from the existing one.
The new class will inhert the capabilities of the old one .But is free to add new faturesof own.