Open Closed Design Pattern 

The Open-Closed Principle (OCP) is a design pattern in computer programming that states that software entities (classes, modules, functions, etc.) should be open for extension but closed for modification. This means that a module should be designed in such a way that it can be extended to meet new requirements, without requiring changes to its source code.

The Open Closed Principle (OCP) is a key principle of object-oriented programming, and is part of the SOLID design principles. It helps to improve code maintainability by allowing new functionality to be added to a system without modifying existing code.

To follow the OCP, a module should be designed in such a way that it can be extended to meet new requirements through the use of inheritance, polymorphism, and other mechanisms, without requiring changes to its source code. This can be achieved by defining a stable and well-defined interface that can be extended, while keeping the implementation details private and protected from changes.

The OCP helps to reduce coupling between modules, making the code easier to understand, test, and modify. It also helps to improve code reusability, by allowing existing modules to be used as building blocks for new functionality, without requiring changes to their source code.

In summary, the OCP helps to create modular and scalable systems, by allowing new functionality to be added to a system without modifying existing code. This makes the code easier to understand, maintain, and modify, and improves the overall quality of the code.