What is object-oriented programming? Explain OOP in depth.

Object-Oriented Programming (OOP) is a programming paradigm based on the concept of "objects," which can contain data, in the form of fields (often known as attributes or properties), and code, in the form of procedures (often known as methods). This approach aims to implement real-world entities like inheritance, hiding, polymorphism etc. in programming. The main aim of OOP is to bind together the data and the functions that operate on them so that no other part of the code can access this data except that function.

Core Concepts of OOP

OOP revolves around four fundamental concepts:

1. Encapsulation
2. Inheritance
3. Polymorphism
4. Abstraction

Let’s delve into each of these concepts:

1. Encapsulation

Encapsulation is the mechanism of hiding the data (attributes) of an object and restricting access to them. This is usually achieved by making the attributes private and then providing public methods to access and modify the values of these private attributes. This ensures that the internal representation of the object is hidden from the outside, only allowing modifications through an interface. Encapsulation enhances data integrity and security.

2. Inheritance

Inheritance allows a class to inherit properties and methods from another class, referred to as the parent class. This helps in code reusability and in creating a new class with the existing class. The new class known as derived class or child class inherits the features from the base class (parent class) and can have additional features of its own.

3. Polymorphism

Polymorphism means "many forms." It allows methods to do different things based on the object it is acting upon. In other words, polymorphism allows defining one interface or method with multiple implementations. There are two primary types of polymorphism:

• Compile-time polymorphism (Method Overloading): Multiple methods can have the same name with different parameters within the same class.
• Runtime polymorphism (Method Overriding): A method in a child class has the same signature as a method in the parent class.

4. Abstraction

Abstraction is the concept of hiding the complex reality while exposing only the necessary parts. It helps in reducing programming complexity and effort. This is achieved by making classes that focus on the essential qualities of an object, rather than the specific details. In programming terms, this often means creating an interface or abstract class that encapsulates a set of functions and properties that various concrete classes will have in common.

Benefits of OOP

• Modularity: The source code for an object can be written and maintained independently of the source code for other objects. Once created, an object can be easily passed around inside the system.
• Reusability: Objects can be reused in different programs, thus reducing code duplication.
• Scalability: OOP provides a clear modular structure for programs which makes it good at handling complex applications that are growing and evolving.
• Maintainability: Due to encapsulation, objects can be maintained independently of each other. This helps with maintaining and updating complex applications.
• Security: By using encapsulation and abstraction, OOP hides the internal states and functionality of objects, protecting the integrity of the data and preventing unauthorized access.

OOP Languages

Several programming languages support OOP, including:

• Java: Everything is treated as an object. Java also provides extensive support for class libraries.
• C++: Allows object-oriented programming, but unlike Java, it does not enforce OOP since it is a hybrid language that also supports procedural programming.
• Python: Uses an object-oriented approach but is flexible enough to support procedural programming as well.
• Ruby, C#, PHP: These languages also support object-oriented programming and provide various degrees of functionality to implement OOP concepts.

In conclusion, OOP is a powerful programming paradigm that structures software design around data, or objects, rather than functions and logic. By focusing on the fundamental concepts of encapsulation, inheritance, polymorphism, and abstraction, OOP provides a clear modular structure which makes it good for defining abstract datatypes, making complex software easier to manage and work with.