Can you list the main design patterns and describe their purpose?

Main design patterns and their purposes:

• Singleton: Ensures a class has only one instance and provides a global point of access.
• Observer: Allows objects to subscribe to events of another object and receive notifications.
• Factory Method: Defines an interface for creating an object but lets subclasses decide which class to instantiate.
• Decorator: Dynamically adds responsibilities to objects by wrapping them.
• MVC (Model-View-Controller): Separates application into data, presentation, and control logic for easier maintenance and extension.

These patterns help create flexible, extendable, and maintainable application architectures.