C Interview Questions and Answers for 5 years experience

1. What is the difference between `malloc` and `new`?

   • Answer: `malloc` allocates raw memory, while `new` allocates memory and calls the constructor of the object being created. `malloc` returns a void pointer, requiring explicit casting, while `new` returns a pointer to the correct type. `new` handles exceptions, while `malloc` doesn't. `new` automatically calls the destructor when the object is deleted using `delete`, while `malloc` requires manual freeing using `free`.

2. Explain the concept of RAII (Resource Acquisition Is Initialization).

   • Answer: RAII is a programming idiom where resource management (like memory, files, network connections) is tied to the object's lifetime. Resources are acquired in the constructor and released in the destructor, ensuring automatic cleanup even in case of exceptions. This improves reliability and reduces memory leaks.

3. What are smart pointers and why are they important?

   • Answer: Smart pointers are classes that act like pointers but automatically manage the memory they point to, preventing memory leaks and dangling pointers. Examples include `unique_ptr` (exclusive ownership), `shared_ptr` (shared ownership), and `weak_ptr` (non-owning pointer). They are crucial for robust memory management in C++.

4. What is the difference between a stack and a heap?

   • Answer: The stack is a LIFO (Last-In, First-Out) data structure used for automatic memory allocation (local variables, function calls). The heap is a region of memory for dynamic memory allocation using `new` and `malloc`. Stack memory is faster to access but has limited size, while heap memory is slower but more flexible in size.

5. Explain polymorphism in C++.

   • Answer: Polymorphism allows objects of different classes to be treated as objects of a common type. It's achieved through virtual functions and inheritance. A virtual function allows derived classes to override the base class implementation, providing flexibility and extensibility.

6. What is a virtual function? Explain its use with inheritance.

   • Answer: A virtual function is a member function declared using the `virtual` keyword in the base class. When a virtual function is called through a pointer or reference to the base class, the actual implementation called depends on the runtime type of the object, not the compile-time type. This enables polymorphism.

7. What is the difference between `const` and `constexpr`?

   • Answer: `const` indicates that a variable's value cannot be changed after initialization. `constexpr` indicates that a variable's value can be evaluated at compile time. A `constexpr` variable must be a `const`, but a `const` variable is not necessarily `constexpr`.

8. Explain the concept of operator overloading.

   • Answer: Operator overloading allows you to redefine the behavior of operators (like +, -, *, /, ==) for user-defined types. This makes code more intuitive and readable by using familiar operators with custom classes.

9. What are templates in C++?

   • Answer: Templates allow you to write generic code that can work with different data types without being explicitly written for each type. They are a powerful tool for code reusability and reducing code duplication.

10. Explain the difference between function overloading and function overriding.

    • Answer: Function overloading is having multiple functions with the same name but different parameters in the same scope. Function overriding is when a derived class provides a specific implementation for a virtual function defined in its base class.

11. Describe your experience with multithreading in C++.

    • Answer: [Detailed description of experience with threading libraries like pthreads, std::thread, etc., including specifics on synchronization mechanisms like mutexes, semaphores, condition variables, and atomic operations. Mention specific projects and challenges overcome.]

12. Explain your understanding of exception handling in C++.

    • Answer: [Detailed explanation of `try`, `catch`, `throw`, exception specifications, and best practices for exception handling. Discussion of different exception types and when to use them.]

13. How familiar are you with design patterns? Give examples.

    • Answer: [Discussion of design patterns like Singleton, Factory, Observer, Strategy, etc., with real-world examples of their application in previous projects.]

14. What are move semantics and how do they improve performance?

    • Answer: [Explanation of move constructors and move assignment operators. How they avoid unnecessary copying and improve efficiency, especially with large objects.]

15. How would you approach debugging a complex C++ program?

    • Answer: [Description of debugging strategies, including using debuggers (gdb, Visual Studio debugger), logging, assertions, and static analysis tools.]

16. Explain your experience with unit testing in C++.

    • Answer: [Discussion of experience with unit testing frameworks like Google Test, Catch2, etc. Importance of test-driven development (TDD).]

17. What are some common C++ coding best practices you follow?

    • Answer: [List of best practices, such as consistent coding style, meaningful variable names, proper commenting, error handling, avoiding memory leaks, using smart pointers, etc.]

18. Describe your experience with working in a team environment.

    • Answer: [Discussion of teamwork experiences, collaborative tools used, and conflict resolution strategies.]

19. How do you stay updated with the latest advancements in C++?

    • Answer: [Mention resources like online courses, conferences, blogs, books, and communities followed to stay updated.]

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