C++ Interview Question Answers

Here you get a free C++ Interview Question which helps you to Give Correct Answer of the Question in the Interview. It also helps you for you college exams Preparation.

Basics and Syntax

1. Explain the difference between #include and #include “file.h”.
2. How does the preprocessor handle #define macros, and what are the risks of using them?
3. Discuss the significance of the constexpr keyword in C++.
4. Explain the use of decltype in C++11 and provide an example of its use.
5. What is the difference between const, constexpr, and volatile in C++?
6. Can you overload the sizeof operator in C++? Why or why not?
7. Why does C++ allow default arguments in functions, and how are they resolved at runtime?
8. How do inline namespaces work in C++?
9. What happens if you define a variable in a header file but do not use the extern keyword?

Object-Oriented Programming (OOP)

1. What is the difference between public, private, and protected inheritance?
2. How does dynamic dispatch work in the context of virtual functions?
3. Explain the concept of polymorphism with examples.
4. Why can’t we have constructors in interfaces (pure virtual classes)?
5. How does the compiler implement multiple inheritance?
6. What is object slicing, and how can it be avoided?
7. Explain the significance of the override and final specifiers in C++11.
8. Can a constructor of a class call a virtual function of the same class? Justify.
9. What is the diamond problem in inheritance, and how does C++ solve it?
10. Explain the differences between abstract classes and interfaces in C++.
11. Why is it recommended to use smart pointers for handling dynamic memory in OOP designs?
12. How does the Rule of Five impact class design in modern C++?
13. Write a program to demonstrate function hiding in C++ inheritance.
14. How is the size of a derived class calculated in C++?
15. What happens when a virtual destructor is not declared in a base class?

Templates and Generic Programming

1. What is template specialization, and when would you use it?
2. How are variadic templates different from regular templates?
3. Explain the difference between typename and class in a template declaration.
4. How does SFINAE (Substitution Failure Is Not An Error) work in templates?
5. What are non-type template parameters? Provide an example.
6. Write a program to implement a custom type-trait using templates.
7. How can you restrict a template to accept only numeric types?
8. What are the implications of templates on compilation time and binary size?
9. Explain the concept of CRTP (Curiously Recurring Template Pattern) with examples.
10. How do you use std::enable_if for conditional compilation in templates?
11. What is the difference between static polymorphism and dynamic polymorphism in the context of templates?
12. Demonstrate how to create a metaprogram using C++ templates.
13. Why do templates increase code bloat, and how can it be mitigated?
14. How does template instantiation work in C++?
15. What are the limitations of templates in comparison to concepts introduced in C++20?

Memory Management

1. Explain the difference between new and malloc in C++.
2. What happens when a memory leak occurs, and how can it be detected?
3. How does the delete operator know the size of the object it is deleting?
4. What is a dangling pointer, and how can it be avoided?
5. Explain the use of placement new in C++.
6. What is the difference between stack and heap memory?
7. How does std::shared_ptr manage memory in a multi-threaded environment?
8. Write a program to implement a custom memory pool in C++.
9. Why is it recommended to avoid manual memory management in modern C++?
10. How does std::unique_ptr differ from std::shared_ptr?
11. What is the effect of calling delete on a nullptr?
12. Explain the importance of RAII (Resource Acquisition Is Initialization) in memory management.
13. What is memory fragmentation, and how can it be mitigated in C++ applications?
14. Demonstrate the use of weak references (std::weak_ptr) in C++.
15. How does the smart pointer’s reference counting mechanism work internally?

Advanced STL and Algorithms

1. How is std::map implemented internally in C++?
2. What is the difference between std::vector and std::deque in terms of performance?
3. Explain how std::unordered_map resolves hash collisions.
4. Write a program to implement a custom comparator for std::priority_queue.
5. How can std::set be used to solve problems involving unique elements?
6. Explain the difference between std::array and std::vector.
7. How do you use std::transform for functional-style programming in C++?
8. What are the differences between std::lower_bound and std::upper_bound?
9. Explain the difference between std::partition and std::stable_partition.
10. How does the implementation of std::list differ from std::vector?
11. Why does std::vector reserve extra capacity during dynamic allocation?
12. How can std::accumulate be used to calculate custom aggregates in containers?
13. Demonstrate the use of std::any, std::optional, and std::variant.
14. What are the advantages of using std::span in modern C++?
15. Explain the importance of std::execution policies in parallel algorithms.

Concurrency and Multithreading

1. What is the difference between std::thread and std::async in C++?
2. How does the C++ memory model ensure thread safety?
3. What is a deadlock, and how can it be avoided in multithreaded programs?
4. Explain the significance of std::mutex and std::unique_lock.
5. How does std::condition_variable work, and when should it be used?
6. What is a race condition, and how can it be prevented?
7. How does std::atomic differ from std::mutex in ensuring thread safety?
8. Demonstrate the producer-consumer problem using C++ threads.
9. Explain the concept of thread-local storage in C++.
10. How do coroutines differ from traditional threads in C++20?
11. Write a program to demonstrate the use of std::call_once and std::once_flag.
12. How do you measure the performance of a multithreaded program in C++?
13. What are the advantages of std::future and std::promise in asynchronous programming?
14. Explain the concept of lock-free programming and its challenges.
15. How does the fork-join model work in parallel programming?

Miscellaneous Advanced Concepts

1. What are the advantages of constexpr functions over regular functions?
2. How do std::move and std::forward improve performance in C++?
3. Explain the significance of the noexcept specifier.
4. How does dynamic casting differ from static casting?
5. What are the advantages of using lambda expressions in modern C++?
6. Demonstrate the use of C++ ranges and pipelines with examples.
7. How is a function object different from a regular function pointer?
8. Explain the purpose of the std::filesystem library in C++17.
9. How can C++ exceptions be caught across threads?
10. What are the advantages of using C++ modules over traditional headers?
11. What are the challenges of writing C++ code for embedded systems?
12. How does the C++20 concepts feature simplify template programming?
13. Explain the purpose of std::align in memory alignment.
14. What are the best practices for debugging large C++ applications?
15. How does C++ achieve interoperability with C and other languages?