Top C++ Interview Questions & Answers for Freshers and Experienced Developers

C++ is one of the most powerful and widely used programming languages in the world. It combines the efficiency of low-level programming with the flexibility of object-oriented design, making it a popular choice for system programming, game development, embedded systems, and high-performance applications.

For job seekers, C++ remains an important skill, and interviewers often test both theoretical knowledge and practical coding abilities. In this blog, we’ll explore the top **C++ interview questions and answers for both freshers and experienced developers.

1. What is C++?

Answer:
C++ is a general-purpose programming language developed by Bjarne Stroustrup as an extension of C. It supports procedural, object-oriented, and generic programming, making it highly versatile.

** 2. What are the key features of C++?
**
Answer:

• Object-oriented programming (OOP) support.
• Low-level memory manipulation using pointers.
• Rich library support with STL (Standard Template Library).
• Compile-time and run-time polymorphism.
• Portability and efficiency.

1. What are classes and objects in C++?

Answer:
A class is a user-defined blueprint for creating objects. An object is an instance of a class.
Example:

class Car {
public:
    string brand;
    void show() {
        cout << "Brand: " << brand << endl;
    }
};
Car c;
c.brand = "Tesla";
c.show();

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

Answer:

• C is a procedural language, while C++ supports OOP.
• C++ provides function overloading, operator overloading, and inheritance, which are not in C.
• C++ has STL for data structures and algorithms.

1. What is a constructor and destructor?

Answer:

• Constructor: A special function automatically called when an object is created.
• Destructor: A special function automatically called when an object is destroyed.

class Test {
public:
    Test() { cout << "Constructor called"; }
    ~Test() { cout << "Destructor called"; }
};

1. What is function overloading?

Answer:
Function overloading allows multiple functions with the same name but different parameter lists.

int add(int a, int b) { return a + b; }
double add(double a, double b) { return a + b; }

1. What is operator overloading?

Answer:
Operator overloading allows developers to redefine operators for user-defined types.

class Complex {
    int real, imag;
public:
    Complex(int r, int i) : real(r), imag(i) {}
    Complex operator + (Complex const &obj) {
        return Complex(real + obj.real, imag + obj.imag);
    }
};

1. Explain inheritance in C++.

Answer:
Inheritance allows one class (child) to acquire the properties and methods of another class (parent).
Types:

• Single
• Multiple
• Multilevel
• Hierarchical
• Hybrid

1. What is polymorphism in C++?

Answer:
Polymorphism means one name, many forms.

• Compile-time (static): Function overloading, operator overloading.
• Run-time (dynamic): Achieved through virtual functions.

1. What are virtual functions?

Answer:
A virtual function is a function declared in a base class using the virtual keyword. It ensures dynamic binding, so the derived class function is executed at runtime.

1. What is the difference between compile-time and run-time polymorphism?

Answer:

Compile-time: Resolved during compilation (function/operator overloading).
Run-time: Resolved at execution (virtual functions).

** 12. What is a pure virtual function?
**
Answer:
A pure virtual function has no definition in the base class and is declared with = 0. It makes a class abstract.

class Shape {
public:
    virtual void draw() = 0;
};

1. What is the Standard Template Library (STL)?

Answer:
STL is a collection of template-based classes and functions for data structures and algorithms.
Components:

Containers (vector, map, set).
Algorithms (sort, search).
Iterators (to traverse containers).

1. What are pointers in C++?

Answer:
Pointers are variables that store memory addresses of other variables.

int x = 10;
int *p = &x;
cout << *p; // prints 10

1. What are smart pointers?

Answer:
Smart pointers are part of C++11 that automatically manage memory. Types include:

unique_ptr – owns object exclusively.
shared_ptr – allows multiple ownership.
weak_ptr – avoids circular references.

1. What are the differences between malloc/free and new/delete?

Answer:

• malloc/free: C-style, doesn’t call constructors/destructors.
• new/delete: C++ style, calls constructors/destructors automatically.

1. What is the difference between pass by value and pass by reference? Answer:

Pass by value: A copy of the variable is passed (changes don’t affect original).
Pass by reference: The actual address is passed (changes affect original).

** 18. What is the difference between stack and heap memory?
**
Answer:

Stack: Stores local variables, memory managed automatically, faster access.
Heap: Stores dynamically allocated memory, managed manually, slower access.

1. What is the difference between struct and class in C++?

Answer:

• In struct, members are public by default.
• In class, members are private by default.
• Otherwise, both can have functions, constructors, and inheritance in C++.

1. Why is C++ still popular?

Answer:
C++ remains popular because:

• It offers high performance.
• It’s widely used in system programming, gaming, and embedded systems.
• Legacy codebases in C++ still exist in industries.
• Modern updates (C++11, C++17, C++20) keep it relevant.

Conclusion

C++ is a powerful language that blends low-level efficiency with high-level abstraction. Preparing for interviews requires not only knowledge of concepts like OOP, pointers, STL, and memory management, but also the ability to write optimized and clean code.

By practicing these C++ interview questions and answers, both freshers and experienced developers can build confidence and crack technical interviews with ease.