What is Object-Oriented Programming

If you are new to coding, “object-oriented programming language” can sound scary and complicated. It does not have to be.

This guide explains what object-oriented programming (OOP) is in very simple English, with clear examples you can understand even if you have never written a line of code.

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A Quick Answer in Simple Words

Short definition of an object-oriented programming language

An object-oriented programming language is a programming language that lets you organise your code around “objects”.

An object is a bundle of:

• data (information, like a car’s colour), and
• behaviour (actions, like a car’s “drive” or “stop”),

all kept together in one place.

Languages like Java, C#, Python, Ruby, and C++ support this style of programming.

One-sentence real-life example

Imagine a Car in real life.

In an object-oriented language you would create a Car object that stores:

• data: colour, brand, number of doors
• actions: start(), stop(), accelerate()

You then create many Car objects (your car, my car, a red car, a blue car) using the same template.

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First, What Is a Programming Language?

Plain-English meaning of programming language

A programming language is simply a way to tell a computer what to do using text that follows certain rules.

Examples: Python, Java, JavaScript, C#, C++, Ruby.

You write instructions in a programming language, and a computer runs those instructions.

Types of programming languages (very simple overview)

There are many ways to organise those instructions. For beginners, you will often hear about:

• Procedural languages – you write a list of steps (procedures or functions) that the computer follows in order.
• Object-oriented languages – you organise your code into objects that represent things in your program (Car, User, Order, Student).
• Functional languages – you focus on functions and data transformation (less important for this article).

Where object-oriented languages fit in

Object-oriented programming (OOP) is a style of thinking and organising code.

An object-oriented programming language is a language that:

• supports objects and classes, and
• gives you tools for key OOP ideas like encapsulation, inheritance, and polymorphism.

Some languages are mostly OOP (like Java, C#, Ruby).

Some are multi-paradigm, which means they support OOP and other styles (like Python, JavaScript, C++).

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What Does “Object-Oriented” Mean?

What is an object in programming?

In programming, an object is:

A thing in your code that holds data and actions together.

For example:

• A BankAccount object might store:
• data: balance, owner name
• actions: deposit(), withdraw(), getBalance()

• A Student object might store:
• data: name, age, grades
• actions: enrol(), calculateAverageGrade()

Real-life analogy

Think about a real student:

• Information about the student:
• name, age, ID number, course
• Actions the student can do:
• enrol in a course
• attend a class
• take an exam

An object in code is like that student, but inside your program.

It carries its own data and knows how to act.

What is a class?

A class is a template or blueprint for creating objects in an object-oriented programming language.

A class describes:

• what data the objects will have (properties), and
• what they can do (methods).

From one class, you can create many objects.

Example idea:

• Class: Car – describes that all cars have colour, brand, and can start() and stop().
• Objects:
• myCar (red, Toyota)
• yourCar (blue, Ford)

Every object created from the Car class follows the same pattern.

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Core Ideas of Object-Oriented Programming (The Four Pillars)

Most explanations of OOP talk about four main ideas, often called the four pillars of object-oriented programming:

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

Let us go through them using very simple words and tiny code-style examples.

Encapsulation – keeping data and code together

Encapsulation means:

• Keep data and the code that works on that data together.
• Hide details that other parts of the program do not need to know.

Analogy: A remote control.

You see buttons (volume up, channel down). Inside there are circuits and chips, but you do not need to see or touch them.

Simple pseudo-code:

class BankAccount:
    def __init__(self, owner, balance):
        self.owner = owner         # data
        self.__balance = balance   # "private" data

    def deposit(self, amount):     # method
        self.__balance += amount

    def get_balance(self):         # method
        return self.__balance

From outside, you call deposit() and get_balance().

You cannot directly change __balance from outside. The object controls its own data.

Inheritance – reusing and extending existing code

Inheritance means one class can reuse and extend another class.

Analogy: A parent and child:

• A child inherits some features from the parent (eye colour, hair type),
• but can also have extra features that are different.

In code:

class Animal:
    def speak(self):
        print("Some generic sound")

class Dog(Animal):  # Dog inherits from Animal
    def speak(self):  # override behaviour
        print("Woof!")

• Dog inherits from Animal.
• It starts with what Animal has, but can change or add behaviour.

This helps you avoid repeating the same code.

Polymorphism – one action, different behaviours

Polymorphism roughly means “many shapes”.

In OOP, it means:

The same action name can cause different behaviour depending on the object.

Analogy: The word “draw”:

• An artist “draws” a picture.
• A bank “draws” money from an account.

Same word, different effect.

In code:

class Cat:
    def speak(self):
        print("Meow")

class Dog:
    def speak(self):
        print("Woof")

def make_animal_speak(animal):
    animal.speak()  # works for any object that has speak()

make_animal_speak(Cat())  # Meow
make_animal_speak(Dog())  # Woof

The function make_animal_speak calls speak(), but the result depends on the object.

Abstraction – hiding details to show only what matters

Abstraction means:

• Hide complex details.
• Show only the simple, important parts to the user.

Analogy: A car dashboard:

• You see steering wheel, pedals, indicators.
• You do not see the engine details, fuel injection system, and so on.

In code, you might have:

class CoffeeMachine:
    def make_espresso(self):
        self.__heat_water()
        self.__grind_beans()
        self.__pump_water()
        print("Here is your espresso")

    def __heat_water(self):
        pass  # hidden details

    def __grind_beans(self):
        pass

    def __pump_water(self):
        pass

From outside, you just call make_espresso().

You do not need to know how heating or pumping works.

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Common Features of Object-Oriented Programming Languages

Almost all object-oriented programming languages have these features:

Classes and objects

• Class – a blueprint (e.g. Car, Person, BankAccount).
• Object – a real “thing” created from a class (e.g. myCar, johnsAccount).

Methods (functions that belong to an object)

A method is a function inside a class.

It describes what the object can do.

Example:

class Person:
    def say_hello(self):
        print("Hello!")

Here, say_hello is a method.

Attributes or properties (data inside an object)

Attributes (or properties/fields) are the data inside an object.

class Person:
    def __init__(self, name, age):
        self.name = name    # attribute
        self.age = age      # attribute

Every Person object will have its own name and age.

Access control (public, private – in simple words)

Many OOP languages let you control who can see or change data:

• Public – available from anywhere in the program.
• Private – hidden inside the object or class only.
• Sometimes also protected – available within a family of related classes.

You do this to protect data and avoid confusion.

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Examples of Object-Oriented Programming Languages

Fully object-oriented languages

These languages are designed mainly for OOP:

• Java – used for enterprise systems, Android apps, large web backends.
• C# – used for Windows apps, games with Unity, web apps (.NET).
• Ruby – used for web apps (e.g. Ruby on Rails).
• Smalltalk – one of the earliest pure OOP languages (more historical now).

In these languages, you normally think of almost everything as an object.

Multi-paradigm languages with OOP support

These languages support OOP, but also other styles:

• Python – very popular, easy to learn; used in web, data science, scripting.
• JavaScript – runs in browsers; uses prototype-based OOP rather than class-based (though modern JS adds a class keyword).
• C++ – supports procedural, object-oriented, and low-level programming.
• PHP – used for web backends, supports OOP and procedural code.

You can choose when to use OOP and when to keep things simple.

Simple Car class example (Python)

Here is a very small Python example to show how OOP looks in a real object-oriented programming language:

class Car:
    def __init__(self, brand, colour):
        self.brand = brand      # attribute
        self.colour = colour    # attribute
        self.speed = 0

    def accelerate(self, amount):
        self.speed += amount

    def brake(self):
        self.speed = 0

# Create objects
my_car = Car("Toyota", "red")
your_car = Car("Ford", "blue")

my_car.accelerate(30)
print(my_car.speed)    # 30

your_car.accelerate(50)
print(your_car.speed)  # 50

Each car object keeps its own data and behaviour.

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Why Do Developers Use Object-Oriented Languages?

Easier to organise large projects

In big applications, there are many parts: users, payments, products, orders, reports.

With OOP, you can:

• give each part its own class,
• group related code together, and
• keep the project more organised.

Code reuse (less repeating yourself)

You can create:

• one base class with common features, and
• several child classes that reuse and extend it.

You write common logic once, and share it. This reduces bugs and repeated code.

Easier to understand and maintain over time

When classes are well named (e.g. Invoice, User, EmailService), the code often reads like a story about the problem you are solving.

This makes it easier to:

• fix bugs
• add new features
• onboard new team members.

 

Teamwork benefits (many developers working on the same code)

Different developers can work on different classes:

• One person builds PaymentService.
• Another builds Order and OrderRepository.
• Another builds User and AuthService.

Clear class boundaries make teamwork smoother.

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Object-Oriented vs Procedural Programming (Simple Comparison)

What is procedural programming?

In procedural programming, you focus on a sequence of steps (procedures or functions) that run one after another.

Example (procedural thinking):

read user input
calculate total
apply discount
print receipt

You usually pass data into functions and pass results out again.

Key differences in how you think about the program

• Procedural: “What steps does my program take?”
• Object-oriented: “What things (objects) do I have, and what can they do?”

Example:

• Procedural: calculateTotal(cart), printReceipt(cart).
• OOP: cart.calculate_total(), receipt.print().

Same idea, but in OOP the data and actions live together inside objects.

When OOP is a good fit

OOP is helpful when:

• your project is medium or large
• you have many related things (Users, Products, Orders, Messages)
• you work in a team
• you expect the code to change and grow over time.

When simple procedural code may be enough

You do not need OOP for everything.

Procedural code is often enough when:

• the program is very small
• it has a simple, one-off job (e.g. rename files, parse a small report)
• only one person is working on it
• you want the fastest, simplest script to get something done.

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Basic Terms You Will See When Learning OOP

Class, object, instance

• Class – the blueprint (e.g. Car, User).
• Object / instance – one actual “thing” created from the class (e.g. my_car, alice_user).

“Instance” is just a more formal word for one specific object.

Method vs function

• Function – a block of code you can call by name.
• Method – a function that belongs to a class or object.

All methods are functions, but not all functions are methods.

Constructor

A constructor is a special method that runs when you create an object.

It usually sets up the object’s initial data.

In Python, the constructor is __init__:

class Person:
    def __init__(self, name):
        self.name = name

In Java, the constructor has the same name as the class:

class Person {
    String name;
    Person(String name) {
        this.name = name;
    }
}

Interface and abstract class (high-level view)

You will see these terms as you go deeper into any object-oriented programming language.

• Interface:
• Describes what methods a class must have, but not how they work.
• Like a contract: “Any class that implements this interface must provide these methods.”

• Abstract class:
• A class that cannot be used directly to create objects.
• It usually provides shared behaviour and may have some methods that must be defined by child classes.

Think of them as tools to structure and share behaviour between related classes.

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Object-Oriented vs Object-Based vs Prototype-Based (Very Brief)

You might see these terms when searching for what an object-oriented programming language is.

• Object-oriented language – supports objects, classes, and features like inheritance and polymorphism (Java, C#, C++, Python, Ruby).
• Object-based language – supports objects, but not full OOP features like inheritance (older Visual Basic, early versions of JavaScript).
• Prototype-based language – uses prototypes instead of classes for inheritance (JavaScript under the hood).

For beginners, you can treat modern JavaScript as supporting OOP, even though it is technically prototype-based.

Historically, OOP ideas came from languages like Simula and Smalltalk in the 1960s and 1970s, but you do not need to know their details to start coding.

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Common Misunderstandings About Object-Oriented Languages

“OOP is only for big companies”

Not true.

OOP can help:

• solo developers
• students
• small scripts that may grow later.

You can start simple and still benefit from basic OOP structure.

“You must use every OOP feature all the time”

You do not.

You can:

• start with just classes, objects, and methods,
• use inheritance only when it really helps,
• avoid over-complicating your design.

Simple OOP is better than clever, confusing OOP.

“If a language supports objects, everything you write must be OOP”

Again, no.

In Python or JavaScript, you can:

• write small procedural scripts,
• and use OOP only when it makes your code easier to manage.

Good developers choose the right tool for each problem.

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How to Start Learning an Object-Oriented Language

1. Choose one beginner-friendly language

For learning OOP as a beginner, two good options are:

• Python – simple syntax, widely used, great for beginners.
• Java – more verbose, but strong OOP structure and many jobs use it.

Pick one and stick with it at first.

2. Focus on classes, objects, and methods first

Before worrying about advanced topics, learn:

• how to define a class
• how to create an object from that class
• how to add attributes (data)
• how to write and call methods (actions).

Practise by writing very small examples.

3. Build tiny projects

Start with very simple, text-based projects, such as:

• To-do list
• Class Task (title, done/not done)
• Methods: mark_done(), display()

• Address book
• Class Contact (name, phone, email)
• Methods: update_phone(), display_contact()

• Simple game character
• Class Player (name, health, score)
• Methods: take_damage(), heal(), add_score()

These are perfect for practising objects and classes in programming without feeling overwhelmed.

4. Suggested next steps

As you improve:

• Follow a structured beginner course for your chosen language.
• Read guides on:
• “What is a class in programming?”
• “What is a function or method?”
• “OOP vs functional programming” (later on).
• Try using an online IDE or coding platform to run small OOP exercises in your browser.
• Explore learning paths like:
• “Python OOP for beginners”
• “Java for beginners”
• “C# beginner course”
• “Path to become a software developer”.

The key is: keep practising regularly, even with tiny exercises.

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Summary: What You Should Remember

One-paragraph recap

An object-oriented programming language is a language that lets you build programs using objects, which bring data and behaviour together.

You use classes as blueprints, then create objects (instances) from them. OOP is built around four key ideas: encapsulation, inheritance, polymorphism, and abstraction.

Key benefits and where it is used

Object-oriented programming helps you:

• organise large projects
• reuse code instead of repeating it
• work better in teams
• maintain and change code more easily.

It is used almost everywhere: web applications, mobile apps, games, enterprise software, tools and libraries.

Clear next step

To move from understanding to doing:

1. Pick one language (Python or Java are good starting points).
2. Write a simple class today (for example, Person with name, age, and a say_hello() method).
3. Create a few objects from that class and call their methods.

Once you have created and used your first few classes and objects, object-oriented programming will start to feel much more natural.

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