Top 25 Interview Questions on C++ Language for 2025
Are you preparing for a C++ interview in 2025? Whether you’re a beginner or an experienced developer, it’s important to be well-prepared with the right set of questions and answers. C++ continues to be one of the most sought-after programming languages due to its efficiency, versatility, and use in developing high-performance applications. In this blog post, we have compiled the Top 25 Interview Questions on C++ Language for 2025 that will help you excel in your next interview.
1. What is the difference between C++ and C?
Answer: C++ is an extension of C that introduces object-oriented programming features such as classes, inheritance, polymorphism, and encapsulation. C is a procedural programming language, while C++ supports both procedural and object-oriented programming.
2. What are the main features of C++?
Answer: C++ is known for its object-oriented features. Key features include:
- Object-Oriented Programming (OOP): Encapsulation, inheritance, polymorphism, and abstraction.
- Templates: For writing generic functions and classes.
- STL (Standard Template Library): Provides various data structures like vectors, stacks, and maps.
- Exception Handling: Allows errors to be managed using
try,catch, andthrow.
3. Explain the concept of pointers in C++.
Answer: Pointers are variables that store memory addresses of other variables. They are used for dynamic memory allocation, passing large data structures efficiently, and for managing arrays.
4. What is the difference between a reference and a pointer in C++?
Answer:
- A pointer is a variable that holds the memory address of another variable and can be changed to point to different objects.
- A reference is an alias for an existing variable, and it must always refer to the same object throughout its lifetime.
5. What is a constructor and a destructor in C++?
Answer:
- A constructor is a special member function used to initialize objects when they are created. It has the same name as the class.
- A destructor is a function called when an object goes out of scope or is explicitly deleted. It is used for cleaning up resources like memory or file handles.
6. Explain the use of the new and delete operators in C++.
Answer:
- The
newoperator dynamically allocates memory on the heap and returns a pointer to the allocated memory. - The
deleteoperator frees dynamically allocated memory, avoiding memory leaks.
7. What is the role of the virtual keyword in C++?
Answer: The virtual keyword is used to allow functions in a base class to be overridden by derived classes. It enables runtime polymorphism, where the function that gets called is determined by the object type, not the pointer type.
8. What is the difference between deep copy and shallow copy in C++?
Answer:
- Shallow copy: Copies the values of objects, but not the dynamically allocated memory.
- Deep copy: Copies both the values and the memory, including any dynamically allocated resources, making the copy independent of the original.
9. What is a static member in C++?
Answer: A static member belongs to the class rather than any instance of the class. Static members are shared across all instances of the class, and they can be accessed without creating an object of the class.
10. What are templates in C++?
Answer: Templates allow you to write generic functions and classes that work with any data type. They provide flexibility and type safety while avoiding code duplication.
11. What is the difference between struct and class in C++?
Answer:
struct: Members are public by default.class: Members are private by default.
12. Explain the concept of multiple inheritance in C++.
Answer: Multiple inheritance occurs when a class derives from more than one base class. C++ supports multiple inheritance, but it can cause ambiguity, which can be resolved using virtual inheritance.
13. What are the different types of polymorphism in C++?
Answer:
- Compile-time polymorphism: Achieved through function overloading and operator overloading.
- Runtime polymorphism: Achieved through inheritance and virtual functions.
14. What is operator overloading in C++?
Answer: Operator overloading allows you to redefine the behavior of operators (e.g., +, -, *) for user-defined types. It enables intuitive use of operators with objects of custom classes.
15. What is the difference between new and malloc in C++?
Answer:
new: Allocates memory and also calls the constructor to initialize objects.malloc: Allocates memory but does not call the constructor, and it returns avoid*pointer, requiring a cast.
16. What is exception handling in C++?
Answer: C++ uses try, catch, and throw to handle exceptions. Code that may throw an exception is placed in a try block, and the exception is caught and handled in the catch block. The throw keyword is used to throw exceptions.
17. What are the types of constructors in C++?
Answer:
- Default Constructor: No arguments are passed.
- Parameterized Constructor: Accepts arguments to initialize an object with specific values.
- Copy Constructor: Initializes an object as a copy of another object.
18. What is the use of the const keyword in C++?
Answer: The const keyword is used to define constants and make variables immutable. It ensures that the value of the variable cannot be changed after initialization.
19. What is the difference between public, private, and protected access specifiers in C++?
Answer:
public: Members are accessible from anywhere.private: Members are accessible only within the class.protected: Members are accessible within the class and derived classes.
20. What is RAII in C++?
Answer: RAII (Resource Acquisition Is Initialization) is a programming idiom where resources like memory or file handles are tied to the lifetime of objects. When an object is destroyed, its resources are automatically released.
21. What is the difference between #include <filename> and #include "filename" in C++?
Answer:
#include <filename>: Searches for the file in system directories or standard library paths.#include "filename": Searches for the file in the current directory first, then in system directories.
22. What is the role of the friend function in C++?
Answer: A friend function is not a member of a class, but it can access the private and protected members of the class. It is used when a function needs to interact with a class but doesn’t logically belong to it.
23. What are smart pointers in C++?
Answer: Smart pointers like unique_ptr, shared_ptr, and weak_ptr are part of C++’s standard library. They automatically manage memory by freeing dynamically allocated memory when it’s no longer in use, preventing memory leaks.
24. What is the inline keyword in C++?
Answer: The inline keyword suggests to the compiler that it should replace the function call with the function’s body to optimize performance by eliminating the overhead of function calls.
25. What is the Standard Template Library (STL) in C++?
Answer: The Standard Template Library (STL) is a collection of template-based classes and functions in C++ that implement commonly used data structures (e.g., vectors, lists, maps) and algorithms (e.g., sorting, searching).
Conclusion:
C++ continues to evolve, and keeping up with the language’s latest features and best practices is crucial for interview success in 2025. By familiarizing yourself with the Top 25 Interview Questions on C++ Language, you’ll be in a better position to showcase your skills to potential employers.