Open-Closed Principle

In object-oriented programming, the open/closed principle states “software entities (classes, modules, functions, etc.) should be open for extension, but closed for modification”; that is, such an entity can allow its behavior to be modified without altering its source code.

Modules that conform to the open-closed principle have two primary attributes:

1. They are “Open For Extension”. This means that the behavior of the module can be extended. That we can make the module behave in new and different ways as the requirements of the application change, or to meet the needs of new applications.
2. They are “Closed for Modification”. The source code of such a module is inviolate. No one is allowed to make source code changes to it.

In the implementation of this principle, normally, the abstract interfaces are used.