What is Object-Oriented Programming? A Beginner's Guide

What is Object-Oriented Programming? A Beginner's Guide

Computer programming is the process of giving well-structured and logical instructions to a computer.

Needless to say, there are multiple ways to program a computer. And object-oriented programming is one of the most popular programming methods in use today.

So if you're curious about object-oriented programming, continue reading this blog!

What is Object-Oriented Programming?

OOP is a programming paradigm where problems are modeled in the form of classes and objects. The main focus is on the data (object) rather than on the procedure or the functions used to manipulate that data.

An object is an abstract representation of things and concepts we encounter in the real world, such as employees, organizations, cars, electronics, or anything you can think of. And a class is a blueprint for creating objects.

Thus, classes are small chunks of reusable code from which multiple objects can be created. This makes programs written using OOP easy to execute, modify, and debug. Thus, object-oriented programming is very useful for building large and complex software.

The main feature of this object-based model is encapsulation, i.e., everything that the object needs is encapsulated inside that object. This includes object data (variables and arrays) and the methods and functions that operate on them.

Other important OOP concepts include inheritance, abstraction, polymorphism, etc.

Programming languages that employ OOP principles include C++, Java, Python, C#, etc.

Building Blocks of OOP

To understand how OOP works, we first need to know its components. Once we do that, we can explore how the core OOP principles are applied to these components.

The building blocks of OOP are

  • Classes
  • Objects
  • Attributes
  • Methods

Let's first explore classes and then move on to objects, attributes, and methods.


A class is a blueprint for objects. It is like the technical design of a house or a car. In such designs, you specify the features of the house. Using those features as a guide, you can then build as many houses as you want.

Classes and objects work in a similar way. If you want to create a program that processes information about your employees, you will need to start by creating an Employee class.

This class will contain

  • employee data in the form of variables (name, salary, job position, etc.) and
  • methods to process that data (calculating bonus, evaluating performance, etc.).
An Employee class will contain data about the employee and methods to process the data.
The Employee class

As can be seen from the figure above, our Employee class contains

  • the name and salary variables,
  • the calculate_bonus() method to calculate the employee's bonus.


Once we've created a class, we can create objects from the class. An object is like a real house or a real car that you make from the blueprint.

You can make as many objects as you want from a class. For example, if you have a class named Employee, you can make objects employee1, employee2, ..., employeeN.

Each of these objects is an individual instance of the Employee class. So it has its own individual data that is separate from other objects of the class. The figure below illustrates this point.

You can create as multiple objects from a single class
Classes and Objects

Now, each Employee object will have its own copy of name, salary, and the calculate_bonus() method. This is how we can model real-world concepts using classes and objects.


These are the data or information associated with the object. In the Employee class we've described above, name and salary are the class attributes since they give the required information on the objects.

Attributes are data of the class and Methods are the logic used inside Class
Attributes and Methods of a Class


These are the procedures and logic that are used to manipulate the object data or attributes. Methods can also be used to create new information about that object.

In our Employee class, we have included a method named calculate_bonus() to calculate the bonus received by an employee.

Suppose the bonus is calculated by adding 0.1% of the total company profit to 5% of the employee salary.

Bonus  = (0.1% of Company Profit) + (5% of Employee Salary)

Then, the mathematical formula needed to calculate this amount will be written inside the calculate_bonus() method.

Inside the calculate_bonus() method, you use mathematical formulas to calculate the bonus
Logic Used By the calculate_bonus() Method

Executing this method will thus create new information about the employee, i.e., the employee bonus.

Principles of Object-Oriented Programming

As programmers, we need to implement certain key features if we want to model an object properly. These key features are the four foundational principles of OOP, which are

  • Encapsulation
  • Inheritance
  • Abstraction
  • Polymorphism


In OOP, the object contains all the data and methods it needs within it.

For example, we can store variables like name and salary inside an Employee class along with a method to calculate the bonus amount.

This is known as encapsulation in OOP.


We can derive one class from another in object-oriented programming (similar to a parent-child relationship).

The parent class is called the base class or superclass, while the child class is called the derived class or subclass.

And just like children inherit traits of their parents, so do child classes inherit the attributes and methods of their parent class. This feature is known as inheritance in OOP.

On top of that, child classes can also possess attributes and methods that the parent class doesn't possess. For example, suppose we derive a Programmer class from the Employee class.

In OOP inheritance, the child class inherits the features of the parent class
Inheritance in OOP

The attributes and methods of this class might look something like this







Here, we have created a new method - write_code() - for the Programmer class. However, all the other methods and attributes are inherited from the Employee class.

So when deriving the Programmer class, we only need to create the write_code() method inside it. This class automatically accesses all the other attributes and methods defined in the Employee class, thus eliminating the need to code them again.


We have seen that an object contains all sorts of data and logic within it. However, we should write our software so that our users can utilize our objects without any knowledge of the object's inner workings.

For example, office workers who need to enter employee data and calculate their bonuses should not need to know how the data is entered and calculated. All they need to know is how to enter the data and which command to use to calculate the bonus.

This simplifies our program implementation, as the objects are independent pieces of code that can be used by people without any coding knowledge. All they need do is to provide employee data and issue some commands.

This act of hiding the object's data and logic from our users is known as abstraction in OOP. Using this principle, we only make the relevant data accessible to our users.


A single method of a class can take multiple forms. This is known as polymorphism.

For example, suppose there are different ways to calculate the bonus depending on the status of the employee.

We can create multiple calculate_bonus() methods to reflect this in our code. Each version of this method will contain a different formula to calculate the bonus.

We can then call the appropriate method depending on the specific situation.

This is often achieved by creating different versions of the function in different derived classes. So when we use an object of a specific derived class, it will execute the method unique to that class.

Benefits of Object-Oriented Programming

OOP principles and components offer multiple advantages and benefits to programmers. Some of them are

  • Reusable Code: Since classes are blueprints for objects, we can use a single set of codes to create multiple objects. Inheritance also leads to reusability since child classes have access to the parent class.
  • Self-Contained Codes: Since all of the object's data and logic is encapsulated within that object, the object becomes an independent and self-contained piece of code. This makes editing and debugging the program easier.
  • Useful Libraries: The reusability of code in OOP allows developers to create libraries of useful code. For example, OOP languages have libraries for advanced mathematics, data analysis, machine learning, audio-visual manipulation, etc. This means that developers working in this field don't need to code everything from scratch.
  • Real-world Modeling: OOP is better suited to model aspects of the real world than other programming paradigms. This is because objects are coded representations of real-world entities and concepts.
  • Easily Upgradable and Scalable: Since objects are self-contained, programmers can implement system functionalities independently.
  • Security: OOP provides program security since the data and logic of the objects are hidden from the users.
  • Flexibility: Using polymorphism, we can adapt a single method to work with a wide variety of logic and scenarios.

Limitations of Object-Oriented Programming

Despite having multiple advantages, OOP also comes with limitations. Some of them are

  • Steep Learning Curve: OOP concepts might be difficult to understand and implement for beginners.
  • Overemphasis on Data: Some programmers feel that OOP places too much emphasis on data, often at the expense of the programming logic.
  • Large Programs: Using OOP often leads to larger programs since it often requires more lines of code.
  • Slower Execution: Since the program files are often larger, execution is often slower.
  • Not Suitable for All Problems: There are programming problems that are better handled by other programming paradigms. Using OOP in such cases would result in inefficient code.

Frequently Asked Questions

1. What is the best OOP language?

There is no such thing as "the best" OOP language since different languages have different applications.

Among the most popular programming languages, Java has the most focus on OOP principles. It is also a great language for software development and mobile applications.

But if you're looking to implement OOP in your web applications, then Python, Ruby, and Golang are the go-to languages.

Finally, OOP languages such as C++ and C# are ideal for game development.

2. Is Python an OOP language?

Yes, Python is an object-oriented programming language. However, it also supports other paradigms such as functional programming. But its primary paradigm is object-oriented programming.

3. Which language is pure OOP?

A pure OOP language treats everything as objects and doesn't allow primitive data types like integer, double, character, etc. As a result, popular languages like Java, Python, C++, C#, etc., are not pure OOP languages.

Instead, the following languages are pure OOP languages:

  • Ruby
  • Scala
  • JADE
  • Emerald