C++ Interview Questions for Beginners: Most Asked Topics – Part 2

Welcome back to our series on C++ interview preparation! In this post, we’re diving into the essential concepts of Object-Oriented Programming (OOP) that every budding developer should know. If you’re gearing up for an interview, understanding these concepts will not only help you answer questions confidently but also lay a solid foundation for your coding skills.

In this article, we’ll explore the four pillars of OOP—encapsulation, inheritance, polymorphism, and abstraction—along with important C++ concepts like constructors, destructors, and operator overloading. Let’s break these down into easy-to-digest sections and connect them to real-world scenarios so you can tackle those interview questions with ease.

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C++ OOPs Interview Questions :

When an interviewer asks about OOP, it’s best to avoid giving a one-liner. Instead, think of object-oriented programming (OOP) in C++ as a way to organise your code around objects, rather than just functions or logic. It revolves around four key principles. First, there’s encapsulation, which means wrapping up data and the methods that work on it, keeping some parts private to maintain control. Then you have inheritance, which lets you create new classes based on existing ones, saving time and effort through code reuse. Polymorphism is about flexibility, allowing functions to operate differently depending on the objects they’re dealing with. Lastly, there’s abstraction, which helps manage complexity by focusing on essential characteristics rather than details. These principles together make your code more modular, easier to maintain, and efficient.

After giving an answer like this, the interviewer might be impressed if they’re looking for theoretical knowledge rather than just practical skills. However, I plan to provide both, so let’s dive into some real-world examples of OOP in C++ to deepen our understanding.

Encapsulation

Inheritance

Polymorphism

Abstraction

I have a detailed guide on OOP in C++ with in-depth examples and real-world scenarios. Please click on the relevant topics above to jump directly to the specific section you’re interested in.

Constructors and Destructors in C++

Constructor :

A constructor is a special member function in C++ that initializes objects of a class. It’s like setting up your workspace before starting a project. Constructors are automatically called when an object is created, ensuring that the object starts in a valid state.

#include <iostream>
#include <string>
using namespace std;

class Book {
private:
    string title;

public:
    Book(string bookTitle) : title(bookTitle) {}

    // Function to display the book title
    void display() const {
        cout << "Title: " << title << endl;
    }
};

int main() {
    // Create a Book object
    Book myBook("InterviewsPreparation.com");

    // Display the book title
    myBook.display();

    return 0;
}

Destructor :

A destructor is a member function executed when an object is destroyed. It’s responsible for cleaning up resources that the object may have acquired during its lifetime, much like cleaning up your workspace after finishing a project.

In C++, destructors have the same name as the class preceded by a tilde (~)

class Book {
public:
    ~Book() {
        // Code to release resources, if any
    }
};

Operator Overloading in C++ :

Operator overloading allows developers to redefine the behavior of operators for user-defined types. It enhances code readability and expressiveness by allowing objects to be manipulated using standard operators, like adding two complex numbers with the + operator.

Example: Overloading the + Operator for a Box Class. Imagine you have two boxes, and you want to create a new box that represents the combined size of the two. Here’s how you can do that using operator overloading.

#include <iostream>
using namespace std;

class Box {
private:
    double width, height, depth;

public:
    // Constructor to initialize the dimensions of the box
    Box(double w, double h, double d) : width(w), height(h), depth(d) {}

    // Overloading the + operator to add two Box objects
    Box operator+(const Box& other) {
        // Add the corresponding dimensions of the two boxes
        return Box(width + other.width, height + other.height, depth + other.depth);
    }

    // Function to display the dimensions of the box
    void display() const {
        cout << "Box Dimensions: " 
             << "Width = " << width 
             << ", Height = " << height 
             << ", Depth = " << depth << endl;
    }
};

int main() {
    // Create two Box objects
    Box box1(2.0, 3.0, 4.0);  // Box with dimensions 2x3x4
    Box box2(1.5, 2.5, 3.5);  // Box with dimensions 1.5x2.5x3.5

    // Add the two boxes using the overloaded + operator
    Box box3 = box1 + box2;

    // Display the dimensions of the original boxes and the combined box
    cout << "Box 1: ";
    box1.display();

    cout << "Box 2: ";
    box2.display();

    cout << "Combined Box: ";
    box3.display();

    return 0;
}

Key Takeaways

• Operator Overloading: Allows you to define how operators like + work with your custom objects, making the code more intuitive and natural.
• Encapsulation: The logic for adding two boxes is hidden inside the class, keeping the main function clean and focused.
• Reusability: Once you’ve defined the + operator for Box objects, you can easily use it anywhere in your program.

Operator Overloading a powerful feature in C++ that makes your custom objects behave like built-in types. start with simple operators like + and * to get comfortable with the concept, then explore more complex overloads.

Summarizing C++ Interview Questions Part-2

The four pillars of OOP—encapsulation, inheritance, polymorphism, and abstraction—provide a robust framework for designing and organizing software. By understanding and applying these principles, you’ll be well-prepared to tackle C++ interview questions and develop efficient, maintainable, and scalable applications.

Remember, the key to mastering these concepts is practice and real-world application. Try implementing these principles in your projects to solidify your understanding and make your code more robust.

Good luck with your interview preparation, and stay tuned for more insights in our C++ series!