C++ interview questions and answers (Part-A)

Here are some commonly asked C++ interview questions along with their answers:

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

• C++ is an extension of the C language, and it includes all features of C with additional object-oriented programming capabilities. C++ introduces classes, inheritance, polymorphism, and other OOP features.

2. Explain the concept of Object-Oriented Programming (OOP).

• Object-Oriented Programming is a programming paradigm that revolves around the concept of objects. An object is a self-contained unit that encapsulates data and behavior. It allows for the organization of code into reusable and modular components, leading to more maintainable and scalable software.

3. What are the access specifiers in C++?

• C++ provides three access specifiers: public, private, and protected.
• public: Members declared as public are accessible from anywhere in the program.
• private: Members declared as private are accessible only within the class.
• protected: Members declared as protected are accessible within the class and its subclasses.

4. What are constructors and destructors?

• Constructors are special member functions that are automatically called when an object is created. They initialize object data members.
• Destructors are special member functions that are automatically called when an object goes out of scope or is explicitly deleted. They clean up resources allocated by the object.

5. What is the difference between new and malloc in C++?

• new is an operator in C++ that is used to allocate memory for objects on the heap and calls the constructor for the object.
• malloc is a function from C that allocates memory on the heap but does not call the constructor for objects. It is not recommended to use malloc with C++ objects.

6. Explain the Rule of Three in C++.

• The Rule of Three states that if a class needs to have a custom implementation of one of the following functions, it likely needs to have custom implementations of all three:
  • Destructor: To free dynamically allocated resources.
  • Copy Constructor: To create a deep copy of the object when copied.
  • Copy Assignment Operator: To perform proper assignment when copying objects.

7. What is the difference between deep copy and shallow copy?

• Shallow copy copies the memory addresses of the data members, resulting in multiple objects pointing to the same memory locations. Changes in one object will affect others.
• Deep copy creates a new copy of the data, so each object has its own independent memory. Changes in one object will not affect others.

8. What are the differences between function overloading and operator overloading?

• Function overloading allows multiple functions with the same name but different parameters. The functions are differentiated by the number or types of arguments.
• Operator overloading allows the definition of custom behaviors for operators when used with objects of a class.

9. Explain RAII (Resource Acquisition Is Initialization).

• RAII is a programming idiom where resource management is tied to object lifetime. Resources (like memory, files, etc.) are acquired in the constructor and released in the destructor of an object. This ensures that resources are properly released when the object goes out of scope.

10. What are smart pointers in C++?

• Smart pointers are objects that behave like pointers but provide automatic memory management. They automatically delete the memory they point to when the last smart pointer referencing it goes out of scope, helping to prevent memory leaks.