A design pattern is a software engineering part. Magento uses many types of design patterns.
(i) MVC Pattern:- MVC stand for Model View Controller.
Model:- is used for database logic.
View:- is used for presentation logic.
Controller:- is used for routing.
(ii) Front Controller Pattern:- It has a single entry point (index.php) for all of it’s requests.
(iii) Singleton Pattern:-It can be only one instance of a given class. It checks instance is already created or not if created then use this otherwise create a new instance.
(iii) Factory Pattern:-The Factory Method is used to instantiate classes in Magento.
(iv) Registry Pattern:-It is used for transferring data between scopes when they cannot be passed on. It is a global scoped container for storing data. All the singletons are stored in the internal registry.
It is used for storing value.
It is used for getting the store value.
It is used for unregister the variable which is in the registry.