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C++ Interview Questions and Answers

In this article we have gathered the latest and most asked C++ Interview Questions and Answers for both freshers and experienced candidates. These C++ or CPP Interview Questions will get you familiar with the types of questions that you will likely come across during your interview.

C++ is a popular object-oriented programming (OOP) language. Due to its reliability, speed, compatibility, and performance, it is widely used in the development of operating systems, applications, games, servers, etc. It was developed by Bjarne Stroustrup at Bell Labs. It is an extension of C and supports object-oriented, procedural and generic programming. C++ has a wide range of applications. It is used in operating systems, database software, banking applications, embedded systems, and more.

C++ Interview Questions and Answer

Here are the top commonly asked C++ interview questions and answers for both freshers and experienced candidates. These C++ Interview Questions will help job seekers to prepare well for the job interview and cross the panel discussion easily.

So let’s get started :

1. What is C++?
2. What are the features of C++?
3. What is the difference between C and C++?
4. What are access modifiers in C++?
5. Explain what is C++ objects?
6. What is Encapsulation in C++?
7. Define token in C++.
8. What is Object Oriented Programming (OOP)?
9. How to export a function from a DLL?
10. What is a virtual function?
11. What is the size of the int data type in C++?
12. What is an overflow error?
13. What is function overriding?
14. What is upcasting in C++?
15. What is a constructor?
16. What is a class template?
17. How to find the length of an array in C++?
18. What is the difference between delete and delete[]?
19. What is the full form of STL in C++?
20. Explain the difference between equal to (==) and assignment operator(=).

1. What is C++?

C++ is an object-oriented programming language created by Bjarne Stroustrup. It was released in 1985.
C++ is a superset of C with the major addition of classes to the C language.
Initially, Stroustrup called the new language “C with classes”. However, after some time it was renamed to C++. The idea of C++ comes from the C increment operator ++.

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2. What are the features of C++?

Following are some of the features of C++:

  • Compiler-based language
  • Fast and powerful
  • Object-Oriented Programming (OOP) language
  • Dynamic memory allocation
  • Extensible
  • Multi-Dimensional language
  • Rich library
  • Highly portable

3. What is the difference between C and C++?

Following are the differences between C and C++:

CC++
C program is a structured programming language.C++ supports both structural and object-oriented programming language.
C supports neither function nor operator overloading.C++ supports both function and operator overloading.
C language does not support the virtual and friend functions.C++ supports both virtual and friend functions.
In C, scanf() and printf() are mainly used for input/output.C++ mainly uses stream cin and cout to perform input and output operations.
C does not support the data hiding. Therefore, the data can be used by the outside world.C++ supports data hiding. Therefore, the data cannot be accessed by the outside world.

4. What are access modifiers in C++?

Access modifiers are used to define how to access class members from outside the class. It defines how functions and variables can be accessed outside the class scope.

There are three types of access modifiers in C++:

  • Private – The functions and variables can be accessed only within the same class.
  • Public – The functions and variables can be accessed from anywhere.
  • Protected – Functions and variables cannot be accessed outside the class except a child class.

5. Explain what is C++ objects?

The class gives the blueprint for the object, so basically an object is created from a class or in other words an object is an instance of a class. Data and functions are bundled together as a self-contained unit called an object. Here, in the example A and B are objects.

Class Student
{
Public:
Int rollno;
String name;
} A, B;

6. What is Encapsulation in C++?

Encapsulation is the process of wrapping together data and the functions that use them into a single unit. Since it bundles related data and functions together, it makes the code cleaner and easier to read.

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There are three types of Encapsulation in C++:

  • Member Variable Encapsulation – All the data members are declared as private.
  • Function Encapsulation – Some member functions are declared as private.
  • Class Encapsulation – All a class is declared as private.

7. Define token in C++.

A token in C++ can be a keyword, identifier, literal, constant and symbol.


8. What is Object Oriented Programming (OOP)?

OOP is a methodology or paradigm that provides a number of concepts. The basic concepts of object oriented programming are given below:

  • Classes and Objects: Classes are used to specify the structure of data. They define the data type. You can create any number of objects from a class. Objects are examples of classes.
  • Encapsulation: Encapsulation is a mechanism that binds data and related operations together and thus hides the data from the outside world. Encapsulation is also known as data hiding. In C++, this is achieved by using access specifiers, i.e., public, private and protected.
  • Abstraction: Abstraction is used to hide the internal implementation and expose only essential details to the outside world. Data abstraction is implemented in C++ using interfaces and abstract classes.
  • Inheritance: Inheritance is used to inherit the properties of one class from another class. It provides you the facility to define one class in term of another class.

9. How to export a function from a DLL?

There are two ways to export a function from a DLL:

  • By using the DLL’s type library.
  • Taking a reference to the function from the DLL instance.

10. What is a virtual function?

Virtual functions are used to replace the implementation provided by the base class. Substitution is always called when the object in question is actually of a derived class, even if the object is accessed by a base pointer rather than a derived pointer. When a function is made virtual, C++ determines at run-time which function to call based on the type of the object pointed to by the base class pointer. Thus, by making the base class pointer to point to different objects, we can execute different versions of virtual functions.

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11. What is the size of the int data type in C++?

The size of the int data type in C++ is 4 bytes.


12. What is an overflow error?

This is a type of arithmetic error. This occurs when the result of an arithmetic operation takes up more than the actual space provided by the system.


13. What is function overriding?

If you inherit a class in a derived class and inside the derived class again provide a definition for one of the functions of the base class, then this function is called an overridden function, and this mechanism is known as function overriding. Known as


14. What is upcasting in C++?

Upcasting is the act of changing a sub class reference or pointer to its super class reference or pointer is called upcasting.


15. What is a constructor?

A constructor is a special method that initializes an object. Its name should be the same as the class name.


16. What is a class template?

A class template is used to create a family of classes and functions. For example, we can create a template of an Array class that will enable us to create an array of different types such as int, float, char, etc. Similarly, we can create a template for a function, let’s say we have a function add(), so we can create multiple versions of add().


17. How to find the length of an array in C++?

We use the sizeof() function to find the length of an array in C++:

#include <iostream>

using namespace std;

int main() {

  int arr[] = {
    5,
    10,
    15,
    20,
    25,
    30
  };

  int arrSize = sizeof(arr) / sizeof(arr[0]);

  cout << “Size of the array is: ” << arrSize;

  return 0;

}

Output

Size of the array is: 6

18. What is the difference between delete and delete[]?

Delete [] is used to release the array of allocated memory which was allocated using new [] whereas delete is used to release one chunk of memory which was allocated using new.


19. What is the full form of STL in C++?

STL stands for Standard Template Library.


20. Explain the difference between equal to (==) and assignment operator(=).

The equals or == operator is used to determine whether two values are equal. If the values are equal, it will return true. If they are not equal, it will return false. On the other hand, assignment or = operator is used to assign the value on the right side of the variable present on the left side.


We hope these C++ Interview Questions help you in cracking your next job Interview easily.

All The Best!

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