If you’ve started learning to code, you might have heard the term OOP, or Object-Oriented Programming. The name can sound intimidatingly technical, but it’s simply a way of writing code, and one which mirrors how we already think about the world. Once it clicks, it can make your code easier to understand, change, and work on as a team.
What is Object-Oriented Programming?
At its core, Object-Oriented Programming is a way of structuring code around “objects,” rather than just lists of instructions.
An object is a bundle of data (information about something) and behaviour (things that something can do).
As an example, imagine you’re building a program for a library. You might have objects like books, members, librarians. Each of these has properties and actions. For example, a book’s properties can be its title, author, publication year. Its actions are that it can be borrowed, returned, or reserved.
In OOP, we model these real-world things as building blocks, or objects, in our code.
The Building Blocks of OOP
Before we create an object or start thinking about its actions or properties, we usually start with a class. A class is like a blueprint or template. It describes what an object should look like (properties) and what it should be able to do (actions).
For example, a Book class might define that every book must have the properties of title and author. It might also define actions, or methods, like borrow or return. We can create an instance of that class, an object, which in this case is one specific book. Our specific book, titled Coding for Beginners and authored by Northcoders, has the required class properties. To match the class methods, it must also be available at the library to check out and return.
You can make lots of objects from the same class, all following the same structure but with different data. Our Book class may include different objects (here, specific books). And while the properties for each (specific titles and author names) will be different for each book, all of them will follow the class template of having a title, an author, and functions like being borrowed or returned.
The Four Key Principles of OOP
You’ll often hear people talk about the “four pillars” of OOP: encapsulation, abstraction, inheritance, and polymorphism. The words themselves can sound obscure, but the ideas behind them are very practical.
1. Encapsulation
Encapsulation is about keeping related things together and hiding unnecessary details.
An object should manage its own data and behaviour. Other parts of the program don’t need to know how it works internally, only what it can do.
Your code will be easier to think about, you’re less likely to accidentally break things, and you can change the internal logic without affecting the rest of the app.
2. Abstraction
Abstraction is about focusing on what an object does, not how it does it.
You don’t need to know how a book is manufactured, how the borrower chose it, or if it was even read before it was returned. You simply need to know that the book is being returned and that it has a title and author.
In code, abstraction works the same way. You interact with simple, well-named methods and don’t worry about the messy details underneath.
The good news is that this means you don’t need to understand everything at once.
3. Inheritance
Inheritance allows one class to reuse and extend another class. This can help you to avoid repeating yourself, and keep your code tidier.
For example, you might have a Book class, and Novels and Magazines could both inherit from it. Novels and magazines all share common Book behaviour (like being able to be borrowed and returned from the library), but each can also have its own specific features. Here, magazines may specifically have data about the edition number (volume 4) on top of the title (Coding Magazine) and author (Northcoders) properties simply required by novels.
4. Polymorphism
Polymorphism is a fancy word for a simple idea: different objects can respond to the same action in different ways.
For example, if you tell several vehicles to “move”, they’ll each move in a different way: a car drives, a bike pedals, and a train rolls along tracks
The action is the same, but the behaviour is different.
Polymorphism makes your code more flexible and easier to extend as your project grows.
Why Do Developers Use OOP?
Object-Oriented Programming is popular because it helps developers write cleaner, more organised code, build large applications without everything turning into chaos, work collaboratively in teams, and make code easier to test and maintain.
Many widely-used languages support OOP, like C#, Java, Python, or TypeScript. If you’re learning to code with the goal of getting into tech, understanding OOP will give you a solid foundation.
Is OOP the Only Way to Write Code?
No, OOP is one approach among several, such as functional programming or procedural programming. In the real world, developers often mix styles depending on the problem they’re solving. As a beginner though, learning OOP can help you understand how modern applications are structured and how developers talk about code.
Summary
When you’re starting out, OOP can feel abstract. It often makes more sense once you start building things, breaking them, and fixing them again. The key thing to remember is this: Object-Oriented Programming is about modelling problems in a way that makes sense to humans, not just computers.
If you’re interested in learning to code and moving into tech, getting comfortable with OOP is a big step forward. Take it slowly, practise regularly, and don’t worry if it doesn’t click straight away. Enrolling on a guided course like a Northcoders bootcamp can give you the chance to learn OOP from supportive instructors, so you can ask questions along the way and progress quicker. If you want to start learning core programming principles, explore Northcoders’ Enterprise Engineering Bootcamp, and launch your career in tech in only 13 weeks.