2023 OOPS IQCode: Key Features You Need to Know


This article provides an overview of Object-Oriented Programming (OOP). It explains the top features of OOP, including inheritance, encapsulation, abstraction, and polymorphism. It also covers objects, classes, constructors, and destructors. Finally, it includes some frequently asked questions and additional resources to learn more about OOP.

What is OOPS?

OOP is a programming paradigm that uses objects to represent real-world entities. These objects are instances of classes that can have properties and methods.

Top Features of OOPS

  • Inheritance
  • Encapsulation
  • Abstraction
  • Polymorphism
  • Method Overriding
  • Method Overloading
  • Objects
  • Classes
  • Constructors and Destructors


OOP is a powerful programming paradigm that helps developers write modular, reusable, and scalable code. By using OOP features, programmers can create complex systems that are easy to understand and maintain.


  • Q1: Which are the best features of OOPs, and why explain?
  • Q2: What is an object in OOPs?
  • Q3: What are the basic principles of OOPs?

Additional Resources

To learn more about OOP, check out the following resources:

  • Object-oriented programming on Wikipedia
  • Object-oriented analysis and design on IBM Developer
  • Object-oriented design principles on SourceMaking

Object-Oriented Programming (OOP) Fundamentals

Object-oriented programming (OOP) is a popular programming paradigm used by almost all developers at some point in their profession. OOP is a powerful and efficient way to write code. This article will introduce the basics and characteristics of OOP to assist you in incorporating it into your own projects.

Object-Oriented Programming (OOP) – Overview

Object-Oriented Programming (OOP) uses classes and objects to create reusable code blueprints. Programming languages such as Python, Java, C++, and JavaScript are OOP languages.

Classes are generic templates that can create more specialized and concrete objects. Individual objects have unique values for each attribute specified in the class. Additionally, classes have methods that execute actions that are beneficial to that particular object type.

Features of OOP

Below are the main features of Object-Oriented Programming:

1. Encapsulation - bundling data and code that operate on it, and keeping both safe from outside interference and misuse.
2. Inheritance - ability of a class to inherit properties and characteristics from a parent class.
3. Polymorphism - ability to use a single type entity, such as a method, to represent different types in different scenarios.
4. Abstraction - defining only the essential features of an object and hiding other implementation details from the user.

These features make OOP an efficient and organized approach to programming.


Inheritance is a feature in OOP where classes can inherit attributes from other classes. Parent classes extend properties and behaviors to their child classes, improving reusability. In JavaScript, inheritance is called prototyping, where a prototype object serves as a base for other objects to derive their actions and features. This further forms prototype chains.

For instance, consider the application Polygon, which represents several Shapes. Now we want to create two different types of polygons – Rectangle and Triangle.


Encapsulation refers to enclosing critical information within an object and revealing only a subset of it to the outside world. When an object is created from a class, its data and methods are enclosed within it. Encapsulation helps to conceal the code implementation and internal data of objects. In a class, some fields are designated as private, while others are public.

The private/internal interface comprises methods and attributes only available from other methods in the same class, while the public/external interface includes those available from outside the class. Encapsulation’s real-time example is a school bag in which books and other items are kept.

Advantages of encapsulation include data hiding, increased flexibility, reusability, and ease of alteration to meet new needs. Encapsulation is a vital process in object-oriented programming as it builds a barrier between different parts of a program acting like an API.

Abstraction in Object-Oriented Programming

Abstraction is a technique that simplifies the interaction between the user and an object, by revealing only a subset of its characteristics and operations. It makes use of simple, high-level techniques to show the complexity of an item and keeps complicated information hidden from the user.

Simple classes are used to indicate the complexity of an object in abstraction, which is an extension of encapsulation.

Real-life Example of Abstraction: When we ride a bike, we only need to know how to ride it, not how it works, or how its internals are designed.

Advantages of Abstraction: It simplifies the process of dealing with complex objects, avoids code duplication, increases reusability, and enhances application security by showing only the necessary information to the user.

// Example:

// A simple class to demonstrate abstraction
class BankAccount {
// Fields
private int accountNumber;
private double balance;

// Methods
public void deposit(double amount) {
balance += amount;

public void withdraw(double amount) {
balance -= amount;

public double getBalance() {
return balance;

// Using abstraction to access the BankAccount class
public class User {
public static void main(String[] args) {
BankAccount account = new BankAccount();
double balance = account.getBalance();
System.out.println("Current balance: $" + balance);


Polymorphism is when objects have similar behavior, such as when child objects override parent behaviors through inheritance. This can be achieved through method overriding and method overloading.

To better understand how this relates to the real world, let’s look at an example with a mobile phone. A phone can store contacts, and if you need to store multiple numbers for one person, you can save the second number under the same name as the first.

In an object-oriented language like Java, you can create a function called createContact that accepts two numbers and the name of the individual as arguments, using the following code:

public void createContact(String name, int number1, int number2) {
// code for creating a contact with two numbers for the same individual

Method Overriding in Object-Oriented Programming

Method overriding is a concept used in runtime polymorphism in object-oriented programming. In this scenario, a child class replaces the implementation of a method in the parent class with its own implementation.

Let’s consider an example of a family of three – a father, mother, and son. The father wants to teach his son how to shoot a rifle, but they have different dominant hands. While the father is right-handed, the child is left-handed, making it difficult to teach the child how to shoot.

However, the son came up with a solution to flip his father’s hands, placing his dominant hand on the trigger. By doing this, he was able to learn quickly and successfully shoot the rifle. This approach reflects method overriding in programming.

In simple terms, the child class provides an alternative implementation, which replaces the parent class method’s original implementation.

Method Overloading

Method overloading is a feature of Compile Time Polymorphism in which two methods or functions can share the same name but with different parameters. This allows you to obtain different results depending on the number of arguments entered.

For instance, consider a class named “Addition” that contains two add() methods – one with int a and int b arguments and the other with int a, int b, and int c arguments. This makes the add() function overloaded.

The method called depends on the number of arguments given in the method calling statement. For example, add(20,30) would call the two-parameter add() function, whereas add(10,20,30) would call the three-parameter add() method.

class Addition{
int add(int a, int b){
return a+b;
int add(int a, int b, int c){
return a+b+c;
public static void main(String args[]){
Addition obj = new Addition();
System.out.println(obj.add(20, 30));
System.out.println(obj.add(10, 20, 30));

Objects in Object-Oriented Programming

Objects are essential building blocks of programs in object-oriented programming. They are self-contained units that consist of attributes and processes to make data usable. Objects are derived from a specific class and can be thought of as a representation of real-world objects or processes in the application being developed.

In programming, variables, functions, and data structures can all be considered objects. An object is an instance of a class that combines data components with accompanying methods that modify them. This allows for the use of abstract data structures.

Using objects results in improved program dependability, easier software maintenance, library administration, and effective task division in programming teams. They are the fundamental data types in object-oriented programming languages and are used extensively in software development.

Understanding Classes in Object-Oriented Programming

Classes are a fundamental concept in object-oriented programming.
They define the blueprint for creating objects, which are instances of the class.

A class specifies its attributes, or member variables, which determine the state of its objects. Additionally, classes define methods which allow objects to exhibit certain behaviors.

For example, a Bird class would contain properties and functionality specific to birds. Each bird instance would be an object of the Bird class and could display the behaviors defined in the methods.

Classes have access specifiers to control access to their members. Private members can only be accessed by methods within the same class, while protected members can be accessed by the class itself and its subclasses. Public members can be accessed by any code.

Constructors and Destructors in Object-Oriented Programming

In most object-oriented languages, constructors have the same name as the class and are public. Overloading is allowed, so multiple argument lists can be used with the same name. In PHP 5.0, the native code function Object() is the same as the _construct() method. Typically, attribute values are initialized in the constructor. Optional _destruct() methods can be used for cleanup tasks such as closing files and database connections when an object is destroyed.

Advantages of OOP:

* OOP models complex things as repeatable, basic structures.
* OOP objects are reusable and can be used in multiple applications.
* Modularity facilitates easier troubleshooting.
* Classes are easier to debug because they generally include all relevant information.
* Code can be reused through inheritance.

Benefits of Object-Oriented Programming

Object-oriented programming requires careful planning and consideration of the program’s structure before coding. This includes decomposing requirements into basic, reusable classes that can be used to create object instances. OOP provides reusable data structures, resulting in time-saving in the long run.

//code can be added with appropriate comments if provided

Best Features of OOP and their Benefits

Object-Oriented Programming (OOP) has three fundamental features that provide numerous benefits over non-OOP languages. These features are Encapsulation, Inheritance, and Polymorphism.

Encapsulation allows for the creation of self-contained modules that connect processing processes to data. This feature provides security by preventing unauthorized access to the data and makes code easy to read and modify.

Inheritance allows for the transfer of one class’s structure and functions to another class in the hierarchy. This feature minimizes code repetition and simplifies code maintenance.

Finally, Polymorphism enables the creation of procedures regarding objects whose exact type is unknown until runtime. This feature increases code flexibility, reduces code complexity and makes it easier to develop and maintain code.

Overall, these features make OOP a powerful programming paradigm that is widely used in various software development industries to build robust and scalable software.

//example of implementation of OOP features
class Animal {
constructor(name) {
this.name = name;

speak() {
console.log(this.name + ' makes a noise.');

class Dog extends Animal {
constructor(name) {

speak() {
console.log(this.name + ' barks.');

let dog = new Dog('Rex');
dog.speak(); //Output: Rex barks.

Understanding Objects in Object-Oriented Programming

In object-oriented programming, an object is an instance of a class. In simpler terms, it’s a real-world entity like a pen, phone, or a chair. Objects can be created using various methods in Java, such as new keyword, newInstance() method, clone() method, factory method, and deserialization. For example, in the class “Human,” the objects could be “Man” or “Woman,” while in the class “Fruit,” the objects could be “Apple,” “Banana,” “Mango,” or “Guava.”


OOP is based on four fundamental principles, which are Abstraction, Encapsulation, Inheritance, and Polymorphism. Additionally, OOP involves the use of classes and objects to implement these principles.

OOPs Interview Questions

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