What is the difference between C and C++ interview questions?

C and C++ interview questions differ primarily due to the unique features and capabilities of each language. While both languages share similarities, especially since C++ is derived from C, the nature of the questions you might encounter in an interview will vary depending on the language’s specific features. Here’s how they differ:

1. Programming Paradigm

• C Interview Questions: C is a procedural programming language, so interview questions focus on procedural programming concepts like functions, loops, and arrays. Common questions include:

  • How do you use pointers in C?
  • Explain how memory allocation works with malloc and free.
  • What is the difference between struct and union in C?
  • How do you implement data structures like linked lists and stacks in C?

• C++ Interview Questions: C++ supports both procedural and object-oriented programming (OOP), so the questions are broader and include OOP concepts. C++ interview questions often focus on:

  • What is the difference between class and struct in C++?
  • Explain the principles of Object-Oriented Programming: inheritance, polymorphism, and encapsulation.
  • How do you implement operator overloading and function overloading?
  • What is a virtual function and how is it used for achieving runtime polymorphism?
  • Explain the diamond problem in multiple inheritance and how C++ solves it.

Source: GeeksforGeeks: Differences Between C and C++

2. Memory Management

• C Interview Questions: Since C uses manual memory management, questions in a C interview focus heavily on:

  • How to allocate and deallocate memory using malloc, calloc, realloc, and free.
  • Explain the use of pointers and pointer arithmetic.
  • How do you handle memory leaks and segmentation faults?

• C++ Interview Questions: In addition to manual memory management, C++ introduces constructors, destructors, and smart pointers for memory management, so questions may include:

  • Explain the role of constructors and destructors in memory management.
  • What are smart pointers (unique_ptr, shared_ptr), and how do they help in memory management?
  • What is RAII (Resource Acquisition Is Initialization)?

Source: FreeCodeCamp: C++ Memory Management

3. Data Structures and Standard Libraries

• C Interview Questions: In C, you’ll often be asked to implement common data structures from scratch since C lacks built-in libraries for things like dynamic arrays, stacks, or queues.

  • How do you implement a linked list in C?
  • Can you write a function to reverse a string in place using pointers?

• C++ Interview Questions: C++ offers the Standard Template Library (STL), so interviewers may ask about using STL for data structures like vectors, sets, maps, and algorithms:

  • What is the difference between std::vector and std::array?
  • How does std::map work under the hood?
  • How do you sort a collection using STL algorithms?

Source: GeeksforGeeks: C++ STL

4. Object-Oriented Programming

• C Interview Questions: Since C is a procedural language, there’s no focus on object-oriented concepts. However, you might still be asked how you would implement OOP concepts like inheritance or polymorphism using structures and function pointers.

  • How can you mimic inheritance in C using struct?
  • How can function pointers be used to achieve polymorphism?

• C++ Interview Questions: C++ is object-oriented, so you’ll be asked to demonstrate knowledge of OOP principles:

  • What is the difference between static and dynamic polymorphism in C++?
  • How does C++ handle multiple inheritance and what problems can arise from it?
  • Explain the use of access specifiers (public, protected, private) in C++ classes.

Source: GFG: OOP Concepts in C++

5. Templates and Generic Programming (C++)

• C Interview Questions: C does not support templates or generic programming, so you won’t see questions related to this.

• C++ Interview Questions: C++ offers templates for generic programming, and interviewers often test your understanding of this powerful feature:

  • How do you implement a function template in C++?
  • What are template specializations?
  • What is the difference between class templates and function templates?

Conclusion

While both C and C++ interviews test your understanding of core programming concepts, C++ interviews will dive deeper into object-oriented programming, memory management with constructors and destructors, templates, and the Standard Template Library (STL). C interviews, on the other hand, focus more on procedural programming, manual memory management, and low-level system interactions.