C++ Interview Questions and Answers (Detailed Explanation)

1) What is C++ and why is it used?

C++ is a general-purpose programming language developed by Bjarne Stroustrup. It is an extension of the C language with added object-oriented features. C++ supports procedural programming, object-oriented programming, and generic programming.

It is widely used in system programming, game development, embedded systems, competitive programming, and performance-critical applications because it provides high execution speed and direct memory management.

2) Explain Object-Oriented Programming (OOP) in C++.

Object-Oriented Programming (OOP) is a programming paradigm based on objects and classes. In C++, OOP helps organize code into reusable and manageable components.

The four main principles of OOP are Encapsulation, Abstraction, Inheritance, and Polymorphism. These concepts improve code reusability, scalability, and maintainability.

3) What is the difference between a class and an object?

A class is a blueprint or template used to create objects. It defines data members (variables) and member functions (methods).

An object is an instance of a class. For example, if “Car” is a class, then “BMW” is an object created from that class.

4) What is a constructor in C++?

A constructor is a special member function of a class that is automatically called when an object is created. It has the same name as the class.

Its main purpose is to initialize data members and allocate necessary resources when the object is created.

5) What is a destructor?

A destructor is a special member function that is automatically called when an object goes out of scope or is deleted.

It is used to release resources such as dynamically allocated memory or file handles. A destructor has the same name as the class but is preceded by a tilde (~) symbol.

6) What is inheritance and why is it important?

Inheritance is a feature of C++ that allows one class (derived class) to acquire properties and behaviors of another class (base class).

It promotes code reusability and reduces duplication. Types of inheritance include Single, Multiple, Multilevel, Hierarchical, and Hybrid inheritance.

7) Explain polymorphism in C++.

Polymorphism means “many forms.” It allows functions or operators to behave differently depending on the object or input.

In C++, polymorphism is achieved through function overloading (compile-time polymorphism) and function overriding using virtual functions (runtime polymorphism).

8) What is the difference between stack and heap memory?

Stack memory is automatically managed and stores local variables and function calls. It is fast but limited in size.

Heap memory is dynamically allocated during runtime using new and delete operators. It provides more flexibility but requires manual memory management.

9) What are pointers in C++?

A pointer is a variable that stores the memory address of another variable.

Pointers allow direct memory access and dynamic memory allocation. They are widely used in data structures like linked lists, trees, and graphs.

10) What is the difference between shallow copy and deep copy?

A shallow copy copies the values of data members but does not duplicate dynamically allocated memory. This may cause multiple objects to share the same memory location.

A deep copy duplicates both data members and dynamically allocated memory, ensuring independent copies of objects.

Preparation Tip: Focus on OOP concepts, memory management, constructors/destructors, and pointers. These topics are frequently asked in technical interviews.