Object Oriented Design (OOD)
Object-Oriented Design (OOD) is a method in computer programming where programmers define not just the data type of a data structure but also the types of operations (functions) that can be applied to the data structure. This approach conceptualizes the problem at hand in terms of objects and classes and allows developers to utilize principles such as inheritance, polymorphism, encapsulation, and abstraction. 
Components of OOD
OOD involves defining objects that are instances of classes, which encapsulate both data and the methods that operate on this data. The primary components in OOD are:
- Classes: These are the blueprints from which objects are created. A class defines the properties (attributes) and methods (functions) common to all objects of a certain kind.
- Objects: These are instances of a class. Each object has a unique identity and can have different attribute values.
- Attributes: These are the properties or characteristics of a class.
- Methods: These are behaviors or functions defined within a class, used to manipulate the object's attributes.
- Inheritance: This allows the creation of hierarchical classifications. A subclass can inherit attributes and methods from a superclass.
- Polymorphism: This permits a subclass to override a method of its superclass, enabling different behaviors in different contexts.
- Encapsulation: This involves hiding the inner workings of a class and only exposing interfaces with which the class's objects will be manipulated.
- Abstraction: This involves creating simple, abstract models of more complex systems, using classes and objects.
Purpose and Role of OOD
The purpose of OOD is to design flexible, reusable, and modular code that is easy to understand, modify, and maintain. It helps intuitively model complex systems that mirror real-world objects and relationships. The key principles of OOD – encapsulation, polymorphism, and inheritance – also help reduce the complexity of software systems, improve code readability, and ensure secure and easy software maintenance.
Importance of OOD
OOD is important because it provides a clear structure for the programs. OOD makes the development process easier, facilitates efficient management of complex systems, and improves software quality. It also makes maintaining and modifying existing code easier as improvements and changes are needed.
Consider a 'Vehicle' class in a program that manages a transportation system. The 'Vehicle' class might have attributes like color, model, and speed and methods like acceleration and brake. An 'Automobile' class could inherit from this 'Vehicle' class and include additional attributes, like fuel type. Each specific automobile in the system would be an instance (object) of the 'Automobile' class, with its own color, model, speed, and fuel type values. The object-oriented design allows you to represent the general features shared by all vehicles and the specific features of each automobile.
- What is Object Oriented Design (OOD) Techopedia