Top 30 Most Common C++ Viva Questions You Should Prepare For
Written by
James Miller, Career Coach
Navigating a technical interview can feel like traversing complex code. For C++ roles, expect questions that probe your foundational knowledge, object-oriented programming understanding, and grasp of advanced concepts. These c++ viva questions are designed not just to test recall but to evaluate your problem-solving approach, your coding style, and your ability to articulate technical ideas clearly. Mastering these common queries is a critical step in demonstrating your readiness for a C++ development position and can significantly boost your confidence during the interview process. Preparing for common c++ viva questions allows you to anticipate the interviewer's line of questioning, enabling you to structure your thoughts and deliver concise, accurate responses. This preparation helps showcase not just what you know, but how well you can explain it. Familiarity with typical c++ viva questions also helps manage interview anxiety, letting your technical skills shine through without being overshadowed by nervousness. By focusing on these core areas, you build a solid base for tackling more complex or specialized questions that might arise. Investing time in practicing answers to these c++ viva questions is an investment in your career growth.
What Are c++ viva questions?
c++ viva questions, often referred to as interview questions or technical queries, are questions posed by interviewers to assess a candidate's proficiency in the C++ programming language. They cover a wide spectrum of topics, ranging from fundamental syntax and data types to intricate concepts like memory management, object-oriented principles, templates, and the Standard Template Library (STL). These questions are part of a technical interview, which might also include coding challenges or system design problems. The viva format encourages interactive discussion, allowing the interviewer to delve deeper into a candidate's understanding. Unlike written tests, c++ viva questions require candidates to verbally explain concepts and justify their approaches. They serve as a dynamic way to gauge the depth of knowledge and clarity of thought process. Preparing specifically for common c++ viva questions helps candidates structure their knowledge effectively for verbal articulation.
Why Do Interviewers Ask c++ viva questions?
Interviewers ask c++ viva questions for several key reasons. Firstly, they want to verify the foundational knowledge stated on a candidate's resume. Knowing basic syntax and principles is essential for any C++ developer. Secondly, these questions assess understanding of core C++ paradigms, especially object-oriented programming (OOP), which is central to modern C++ development. Concepts like inheritance, polymorphism, and encapsulation are critical. Thirdly, c++ viva questions often explore how a candidate handles complex topics like memory management, threading, and exception handling, revealing their attention to detail and awareness of potential pitfalls. They also evaluate problem-solving skills and the ability to think critically about design choices. Finally, and perhaps most importantly, viva questions test a candidate's communication skills – the ability to explain complex technical ideas simply and logically is vital for collaboration within a team. Preparing for common c++ viva questions helps candidates practice concise and effective communication.
Preview List
What is C++?
What are the basic data types in C++?
What is the difference between while and for loops?
What are pointers in C++?
What is dynamic memory allocation in C++?
What is the difference between malloc and calloc in C++?
How do you free memory in C++?
What is recursion in C++?
What are classes and objects in C++?
What is inheritance in C++?
What is polymorphism in C++?
What is operator overloading in C++?
What are static members and static member functions in C++?
What is a friend function in C++?
What are templates in C++?
What is a namespace in C++?
What is the Standard Template Library (STL) in C++?
What are smart pointers in C++?
What is a lambda expression in C++?
What is a copy constructor in C++?
What is a move constructor and move assignment operator in C++?
What is exception handling in C++?
What is the difference between deep copy and shallow copy in C++?
What are the differences between const and volatile keywords in C++?
What is multithreading in C++?
How do you handle memory leaks in C++?
What is the role of the scope resolution operator (::)?
What is a union in C++?
What is a linked list in C++?
What is an enum in C++?
1. What is C++?
Why you might get asked this:
This is a fundamental c++ viva question to gauge your basic understanding and how you define the language you claim expertise in. It checks if you know its origin and core purpose.
How to answer:
Define C++ as an extension of C, mention its high-performance nature, general-purpose use, and key features like OOP support.
Example answer:
C++ is a powerful, compiled, general-purpose language developed as an extension of C by Bjarne Stroustrup. It's known for performance, system programming, games, and supports both procedural and object-oriented paradigms.
2. What are the basic data types in C++?
Why you might get asked this:
Interviewers ask this to ensure you know the fundamental building blocks for storing data, a basic requirement for any C++ developer tackling c++ viva questions.
How to answer:
List the standard built-in types and briefly mention what they represent (integers, characters, floating-point numbers, booleans).
Example answer:
Basic data types include int (integers), char (single characters), float and double (single and double-precision floating-point numbers), and bool (boolean values, true or false).
3. What is the difference between while and for loops?
Why you might get asked this:
This c++ viva question assesses your grasp of control flow statements and when to use each type of loop effectively based on the situation.
How to answer:
Explain that while is for indefinite iteration based on a condition, while for is typically used when the number of iterations is known beforehand.
Example answer:
A while loop repeats as long as a condition is true, without needing a known number of iterations. A for loop is best when you know the number of repetitions, often used for iterating over sequences with initialization, condition, and iteration step.
4. What are pointers in C++?
Why you might get asked this:
Pointers are core to C++ memory manipulation. This c++ viva question tests your understanding of direct memory access and address handling, crucial for low-level programming.
How to answer:
Define pointers as variables holding memory addresses and explain their use in accessing/manipulating data indirectly.
Example answer:
Pointers are variables that store the memory address of another variable. They allow direct memory access, enabling efficient data manipulation and dynamic memory allocation, but require careful handling to avoid errors.
5. What is dynamic memory allocation in C++?
Why you might get asked this:
This c++ viva question checks if you understand managing memory size and lifetime at runtime, essential for flexible data structures and resource management.
How to answer:
Describe dynamic memory allocation as allocating memory during program execution, often using new and delete operators.
Example answer:
Dynamic memory allocation is the process of allocating memory during program runtime, rather than at compile time. C++ uses new to allocate memory on the heap and delete to free it, providing flexibility for variable-sized data.
6. What is the difference between malloc and calloc in C++?
Why you might get asked this:
This c++ viva question, though C functions, is common as C++ evolved from C and often interfaces with C libraries. It tests your knowledge of C-style memory management.
How to answer:
Explain that malloc allocates memory without initialization, while calloc allocates memory for an array and initializes all bytes to zero.
Example answer:
malloc allocates a block of memory of a specified size, but the content is uninitialized (garbage values). calloc allocates memory for an array of a specified number of elements and initializes all bytes in the allocated space to zero.
7. How do you free memory in C++?
Why you might get asked this:
Understanding memory deallocation is crucial to prevent memory leaks. This c++ viva question directly assesses your knowledge of freeing dynamically allocated memory.
How to answer:
Specify using the delete operator for single objects allocated with new and delete[] for arrays allocated with new[].
Example answer:
Memory allocated with new for a single object is freed using the delete operator. For memory allocated with new[] for an array, you must use delete[] to correctly free all elements.
8. What is recursion in C++?
Why you might get asked this:
Recursion demonstrates understanding of function calls, stack usage, and problem-solving by breaking down issues into smaller, self-similar parts, a common c++ viva question topic.
How to answer:
Define recursion as a function calling itself and mention the necessity of a base case to prevent infinite loops.
Example answer:
Recursion is a technique where a function calls itself to solve a problem. Each recursive call solves a smaller part of the problem until a base case is reached, which stops the recursion and allows results to propagate back.
9. What are classes and objects in C++?
Why you might get asked this:
This is a core OOP c++ viva question. It checks if you understand the fundamental concepts of building blocks for object-oriented design.
How to answer:
Define a class as a blueprint defining data (attributes) and behavior (methods), and an object as an instance of that class.
Example answer:
A class is a user-defined blueprint or template for creating objects, defining their properties (member variables) and behaviors (member functions). An object is an instance of a class, a concrete entity created based on the class blueprint.
10. What is inheritance in C++?
Why you might get asked this:
Inheritance is a key OOP pillar for code reuse and establishing relationships between types. This c++ viva question tests your understanding of creating derived classes.
How to answer:
Explain inheritance as a mechanism where one class (derived) acquires properties and behavior from another class (base), promoting code reuse and creating 'is-a' relationships.
Example answer:
Inheritance allows a new class (derived class) to inherit members (data and methods) from an existing class (base class). This facilitates code reuse and establishes a hierarchical relationship where the derived class is a specialized version of the base class.
11. What is polymorphism in C++?
Why you might get asked this:
Polymorphism is a cornerstone of OOP, allowing flexibility and extensibility. This c++ viva question assesses your understanding of using a single interface for different underlying types.
How to answer:
Define polymorphism as the ability of an object to take on multiple forms, often achieved through method overriding (runtime) and method overloading (compile time).
Example answer:
Polymorphism means "many forms". In C++, it allows objects of different classes to be treated as objects of a common base class. This is typically achieved via virtual functions (runtime polymorphism) or function/operator overloading (compile-time polymorphism).
12. What is operator overloading in C++?
Why you might get asked this:
Operator overloading is a C++ feature that allows operators to have context-specific meanings, important for making user-defined types behave more like built-in types.
How to answer:
Explain operator overloading as giving operators new meanings when applied to user-defined data types (objects of a class).
Example answer:
Operator overloading allows you to redefine the meaning of standard C++ operators (like +, -, *, ==) when they are used with objects of your own classes. This can make code involving class objects more intuitive and readable.
13. What are static members and static member functions in C++?
Why you might get asked this:
Static members and functions represent data/behavior belonging to the class itself, not individual objects. This c++ viva question checks your understanding of class-level attributes.
How to answer:
Define static members as shared by all objects of a class and static member functions as functions callable using the class name without an object instance.
Example answer:
Static members belong to the class, not any specific object instance. All objects of the class share a single copy. Static member functions can access only static members and can be called directly using the class name, without needing an object.
14. What is a friend function in C++?
Why you might get asked this:
Friend functions break encapsulation slightly but can be necessary for certain design patterns or operator overloading. This c++ viva question tests your knowledge of access control mechanisms.
How to answer:
Explain that a friend function is declared within a class as friend and can access that class's private and protected members, despite not being a member function.
Example answer:
A friend function is a non-member function that is granted access to the private and protected members of a class by declaring it as a 'friend' inside the class definition. It is often used for operator overloading or utility functions needing internal access.
15. What are templates in C++?
Why you might get asked this:
Templates enable generic programming, a powerful C++ feature for writing code that works with different data types. This c++ viva question assesses your understanding of type-agnostic code.
How to answer:
Define templates as a way to write generic functions or classes that can operate on different data types, allowing type-safety without code duplication.
Example answer:
Templates provide a way for generic programming in C++. They allow you to define functions or classes that work with any data type, specified as parameters. This avoids repeating the same code for different types and promotes code reuse and type safety.
16. What is a namespace in C++?
Why you might get asked this:
Namespaces help prevent naming conflicts in large projects or when using external libraries. This c++ viva question tests your understanding of scope management.
How to answer:
Explain that a namespace is a declarative region used to scope identifiers (like variables, functions, classes) to prevent name clashes.
Example answer:
A namespace is a mechanism used to group related entities like classes, objects, and functions under a unique name. It helps prevent name collisions, particularly in large projects or when combining code from multiple libraries (e.g., std::).
17. What is the Standard Template Library (STL) in C++?
Why you might get asked this:
The STL is a fundamental part of modern C++ development, providing ready-to-use data structures and algorithms. This c++ viva question checks your familiarity with this essential library.
How to answer:
Describe the STL as a library providing generic containers, algorithms, and iterators that work with various data types using templates.
Example answer:
The STL is a library of template classes and functions providing common data structures (containers like vector, list, map), algorithms (sort, find), and iterators. It promotes code reusability and efficiency through generic programming.
18. What are smart pointers in C++?
Why you might get asked this:
Smart pointers are crucial for modern C++ memory management, mitigating issues like memory leaks and dangling pointers. This c++ viva question assesses your knowledge of safe resource handling.
How to answer:
Define smart pointers as wrappers around raw pointers that automatically manage the memory they point to, typically using RAII (Resource Acquisition Is Initialization).
Example answer:
Smart pointers are objects that act like pointers but manage memory automatically. They use RAII to ensure that dynamically allocated memory is properly deallocated when the smart pointer goes out of scope, preventing memory leaks (e.g., std::uniqueptr, std::sharedptr).
19. What is a lambda expression in C++?
Why you might get asked this:
Lambda expressions provide a concise way to create anonymous function objects, useful for algorithms or short callbacks. This c++ viva question tests your knowledge of modern C++ features.
How to answer:
Describe a lambda expression as an anonymous inline function object, often used with algorithms or where a small function is needed temporarily.
Example answer:
A lambda expression is a short, anonymous function object that can be defined inline, often used with algorithms or in contexts where a function is needed temporarily. They can capture variables from their surrounding scope using a capture clause [].
20. What is a copy constructor in C++?
Why you might get asked this:
Copy constructors are vital for correctly creating copies of objects, especially those managing resources like dynamic memory. This c++ viva question checks your understanding of object copying.
How to answer:
Define a copy constructor as a special constructor called when a new object is created as a copy of an existing object of the same class.
Example answer:
A copy constructor is a special member function that is automatically called when an object is initialized with another object of the same class. It defines how a copy of an object should be created, which is crucial for objects managing resources.
21. What is a move constructor and move assignment operator in C++?
Why you might get asked this:
Move semantics (C++11 onwards) are essential for performance optimization by avoiding unnecessary copies when transferring resources. This c++ viva question tests your understanding of modern C++ efficiency features.
How to answer:
Explain move constructor/assignment as mechanisms to transfer ownership of resources from a temporary (rvalue) object to a new or existing object, avoiding deep copies.
Example answer:
The move constructor and move assignment operator transfer resource ownership from a temporary object (an rvalue) instead of copying. This is much more efficient for objects holding large resources like dynamic memory, preventing expensive deep copies.
22. What is exception handling in C++?
Why you might get asked this:
Exception handling is the standard C++ way to manage runtime errors gracefully without abrupt program termination. This c++ viva question assesses your approach to robust error management.
How to answer:
Describe exception handling using try, throw, and catch blocks to detect, signal, and handle runtime errors or exceptional conditions.
Example answer:
Exception handling is a mechanism using try, throw, and catch blocks to deal with runtime errors or exceptional situations that can occur during program execution. It allows separating error-handling code from the main logic, making the program more robust.
23. What is the difference between deep copy and shallow copy in C++?
Why you might get asked this:
This c++ viva question is critical when dealing with objects containing pointers or dynamic memory, demonstrating your understanding of resource management during copying.
How to answer:
Explain that shallow copy copies only the pointer or reference, while deep copy creates a new instance of the pointed-to data.
Example answer:
Shallow copy copies the pointer or reference to the original data, so both objects share the same underlying resource. Deep copy creates a completely new copy of the data pointed to by the pointer, ensuring each object has its own independent resource.
24. What are the differences between const and volatile keywords in C++?
Why you might get asked this:
These keywords relate to compiler optimizations and special memory types (like hardware registers). This c++ viva question probes your understanding of how qualifiers affect variable access.
How to answer:
Define const as indicating a value cannot be changed by the program and volatile as indicating a value can change unexpectedly by external factors.
Example answer:
const guarantees that a variable's value won't be changed by the program itself. volatile tells the compiler that a variable's value might change unexpectedly by external means (like hardware), preventing aggressive optimizations that assume the value is constant.
25. What is multithreading in C++?
Why you might get asked this:
Multithreading is essential for concurrent programming and leveraging multi-core processors. This c++ viva question checks your knowledge of designing concurrent applications.
How to answer:
Describe multithreading as executing multiple threads concurrently within a single process, allowing parallel execution of tasks.
Example answer:
Multithreading is the execution of multiple sequences of instructions (threads) within a single program concurrently. It allows a program to perform multiple tasks seemingly at the same time, often improving responsiveness and performance on multi-core systems.
26. How do you handle memory leaks in C++?
Why you might get asked this:
Preventing memory leaks is paramount in C++. This c++ viva question directly asks about your strategies for ensuring memory is freed correctly.
How to answer:
Mention using smart pointers (std::uniqueptr, std::sharedptr), following RAII principles, and carefully pairing new with delete (or new[] with delete[]).
Example answer:
Handling memory leaks involves ensuring every allocation is matched by a deallocation. Modern C++ uses smart pointers (uniqueptr, sharedptr) and RAII (Resource Acquisition Is Initialization) to automate this. Careful manual new/delete pairing is needed in older code or specific scenarios.
27. What is the role of the scope resolution operator (::)?
Why you might get asked this:
The scope resolution operator is fundamental for accessing members of namespaces or classes, or global variables. This c++ viva question tests your understanding of scoping rules.
How to answer:
Explain its use to specify the scope from which an identifier (variable, function, class) should be accessed, particularly to distinguish it from similarly named identifiers in different scopes.
Example answer:
The scope resolution operator :: is used to define or access a member of a class or namespace, or to access global scope variables when they are hidden by local ones. For example, ClassName::member or namespaceName::function.
28. What is a union in C++?
Why you might get asked this:
Unions are C-style data structures still available in C++, useful for saving memory by allowing different types to share the same memory location. This c++ viva question checks your knowledge of data packing.
How to answer:
Define a union as a special data type that allows multiple members to occupy the same memory location; only one member can hold a value at any given time.
Example answer:
A union is a composite data type where all members share the same memory location. It can hold different data types but only one member's value can be active at a time. Unions are used to save memory when you know only one piece of data is needed at any point.
29. What is a linked list in C++?
Why you might get asked this:
Linked lists are a basic dynamic data structure. This c++ viva question assesses your understanding of node-based data structures and dynamic memory usage beyond arrays.
How to answer:
Describe a linked list as a linear data structure where elements (nodes) are not stored contiguously. Each node contains data and a pointer to the next node.
Example answer:
A linked list is a dynamic data structure composed of nodes. Each node contains data and a pointer (or link) to the next node in the sequence. This structure allows for efficient insertions and deletions compared to arrays, though access is sequential.
30. What is an enum in C++?
Why you might get asked this:
Enums provide a way to create a set of named integer constants, improving code readability and maintainability. This c++ viva question checks your knowledge of creating custom literal types.
How to answer:
Define an enum as a user-defined data type consisting of a set of named integer constants, used for making code more readable and less error-prone than using raw integers.
Example answer:
An enum (enumeration) is a user-defined data type that assigns names to integer values. It provides a way to create a set of discrete, named values for a type, making code more readable and self-documenting compared to using magic numbers.
Other Tips to Prepare for a c++ viva questions
Excelling in c++ viva questions goes beyond memorizing answers. Practice articulating your thoughts clearly and concisely. Think about common patterns like memory management, RAII, and the core principles of OOP. Don't just state facts; explain why something works or when you would use a particular feature. As Bjarne Stroustrup, the creator of C++, aptly puts it, "The most important single aspect of software development is to be clear about what you are trying to build." This clarity should extend to your technical explanations. Consider using tools like Verve AI Interview Copilot (https://vervecopilot.com) to practice answering technical questions and receive feedback on your responses. Verve AI Interview Copilot can simulate interview scenarios, helping you refine your explanations for c++ viva questions. Review your past projects and be ready to discuss the C++ features you used and the challenges you overcame. Engaging with a tool like Verve AI Interview Copilot specifically for c++ viva questions can highlight areas where your verbal explanations might need improvement. Mock interviews, whether with peers or AI, are invaluable. Remember, confidence often stems from preparation. Utilize resources like Verve AI Interview Copilot to build that confidence by practicing your responses to common c++ viva questions in a simulated environment.
Frequently Asked Questions
Q1: How deep should my answers be for c++ viva questions?
A1: Be concise but demonstrate understanding; define the concept, briefly explain its purpose, and perhaps mention a key use case or related pitfall.
Q2: Should I provide code examples during a viva?
A2: Briefly mentioning syntax or pseudo-code is helpful, but detailed coding is usually reserved for separate coding challenges, unless asked.
Q3: What if I don't know an answer?
A3: Be honest. State you don't know the exact answer but try to reason about related concepts or how you might find the solution.
Q4: Are there C++ version-specific viva questions?
A4: Yes, modern C++ (C++11/14/17/20) features like smart pointers, lambdas, and move semantics are common topics.
Q5: How important is explaining 'why' in c++ viva questions?
A5: Very important. Explaining the rationale behind features or design choices shows deeper understanding than just reciting definitions.
Q6: Can using Verve AI Interview Copilot help with c++ viva questions?
A6: Yes, it offers practice and feedback on technical explanations, which is directly relevant to preparing for c++ viva questions.
