Object-oriented programming is the successor of procedural (structural) programming. Procedural programming describes programs as groups of reusable code units (procedures) which define input and output parameters. Procedural programs consist of procedures, which invoke each other.
The problem with procedural programming is that code reusability is hard and limited – only procedures can be reused and it is hard to make them generic and flexible. There is no easy way to work with abstract data structures with different implementations.
The object-oriented approach relies on the paradigm that each and every program works with data that describes entities(objects or events) from real life. For example: accounting software systems work with invoices, items, warehouses, availabilities, sale orders, etc.
This is how objects came to be. They describe characteristics (properties) and behavior (methods) of such real life entities.
The main advantages and goals of OOP are to make complex software faster to develop and easier to maintain. OOP enables the easy reuse of code by applying simple and widely accepted rules (principles). Let’s check them out.
Fundamental Principles of OOP
In order for a programming language to be object-oriented, it has to enable working with classes and objects as well as the implementation and use of the fundamental object-oriented principles and concepts: inheritance, abstraction, encapsulation and polymorphism. Let’s summarize each of these fundamental principles of OOP:
- Encapsulation
We will learn to hide unnecessary details in our classes and provide a clear and simple interface for working with them.
- Inheritance
One of the most important concepts in object-oriented programming is inheritance. Inheritance allows us to define a class in terms of another class, which makes it easier to create and maintain an application. This also provides an opportunity to reuse the code functionality and speeds up implementation time.The idea of inheritance implements the IS-A relationship. For example, mammal IS A animal, dog IS-A mammal hence dog IS-A animal as well, and so on.
- Abstraction: Abstraction is an emphasis on the idea, qualities and properties rather than the particulars (a suppression of detail). The importance of abstraction is derived from its ability to hide irrelevant details and from the use of names to reference objects. Abstraction is essential in the construction of programs. It places the emphasis on what an object is or does rather than how it is represented or how it works. Thus, it is the primary means of managing complexity in large programs.
- Polymorphism : The word polymorphism means having many forms. In object-oriented programming paradigm, polymorphism is often expressed as 'one interface, multiple functions'.
Polymorphism can be static or dynamic. In static polymorphism, the response to a function is determined at the compile time. In dynamic polymorphism, it is decided at run-time.