Cracking a C++ OOPs interview requires a solid grasp of key concepts like classes, objects, inheritance, and polymorphism. To make your preparation easier, we’ve compiled 20 commonly asked C++ OOPs interview questions along with detailed answers.
This guide will help you understand both theoretical and practical aspects, making sure you are ready for any challenge.
Fun Fact: In India, C developers with up to 5 years of experience earn between ₹2 lakh and ₹14.5 lakh per year.
Basic C++ OOPs Interview Questions
Here is a list of basic C++ OOPs interview questions and answers:
- What is Object-Oriented Programming (OOP) in C++?
OOP in C++ is a programming paradigm that uses objects and classes to structure software. It emphasizes concepts like encapsulation, inheritance, polymorphism, and abstraction to model complex systems.
- How do classes and objects differ in C++?
A class is a blueprint defining the structure and behaviour (data members and functions) that objects of the class will have. An object is an instance of a class, representing a specific entity with the attributes and behaviours defined by the class.
- What are the four main principles of OOP?
The four main principles are:
- Encapsulation: Bundling data and methods that operate on the data within a single unit, or class.
- Abstraction: Hiding complex implementation details and showing only the necessary features of an object.
- Inheritance: Allowing a new class to inherit properties and behaviours from an existing class.
- Polymorphism: Enabling entities to take on multiple forms, allowing for methods to perform differently based on the object they are acting upon.
- What is inheritance, and how is it implemented in C++?
Inheritance allows a class (derived class) to inherit attributes and methods from another class (base class). In C++, it’s implemented using a colon followed by the access specifier and the base class name:
class DerivedClass : public BaseClass {
// class members
};
OOPs Concepts in C++ Interview Questions
These are some commonly-asked concepts in OOPs interview questions C++:
- What is polymorphism in C++, and what are its types?
Polymorphism allows functions or methods to process objects differently based on their data type or class. The two types are:
- Compile-time (static) polymorphism: Achieved through function overloading and operator overloading.
- Runtime (dynamic) polymorphism: Achieved through inheritance and virtual functions.
- How does abstraction differ from encapsulation?
Abstraction focuses on hiding the complex implementation details and showing only the essential features of an object. Encapsulation, on the other hand, involves bundling the data and methods that operate on the data within a single unit and restricting access to some of the object’s components.
- What are access specifiers in C++, and why are they important?
Access specifiers define the accessibility of class members. The three types are:
- Public: Members are accessible from outside the class.
- Protected: Members are accessible within the class and by derived class(es).
- Private: Members are accessible only within the class.
They are important for implementing encapsulation and controlling how data is accessed or modified.
- Can you explain the concept of constructors and destructors?
A constructor is a special member function that initializes objects of a class. It has the same name as the class and no return type. A destructor is a special member function that is executed when an object is destroyed, having the same name as the class preceded by a tilde (~) and no return type.
OOPs Interview Questions C++ for Freshers
Let’s go through the important C++ Object Oriented interview questions and answers:
- What is the difference between a class and a struct in C++?
In C++, the primary difference is the default access level:
- Class: Members are private by default.
- Struct: Members are public by default.
Otherwise, both can have member functions, inheritance, and access specifiers.
- How does method overloading differ from method overriding?
Method overloading allows multiple functions with the same name but different parameters within the same scope. Method overriding allows a derived class to provide a specific implementation of a function that is already defined in its base class.
- What is a virtual function, and why is it used?
A virtual function is a member function in a base class that can be overridden in a derived class. It is declared using the virtual keyword. Virtual functions enable runtime polymorphism, allowing the program to decide at runtime which function to invoke based on the object type.
- Can you explain the concept of friend functions in C++?
A friend function is a function that has access to the private and protected members of a class while not being a member of that class itself. It is declared using the friend keyword inside the class definition.
C++ Object Oriented Interview Questions for Experienced
Here are some common Object Oriented Programming C++ interview questions and answers for experienced candidates:
- What are abstract classes, and how are they implemented in C++?
An abstract class in C++ is a class that contains at least one pure virtual function. It cannot be instantiated and serves as a base class for derived classes.
Example:
class Shape {
public:
virtual void draw() = 0; // Pure virtual function
};
- How does C++ achieve runtime polymorphism?
C++ achieves runtime polymorphism through virtual functions. When a base class has a virtual function, a derived class can override it, and the function call is resolved at runtime based on the actual object type.
- What is multiple inheritance, and what are its potential issues?
Multiple inheritance allows a derived class to inherit from more than one base class. The main issue is the diamond problem, where ambiguity arises due to multiple copies of the same base class members.
- What is the role of the virtual destructor in base classes?
A virtual destructor guarantees that when a base class pointer pointing to a derived class object is deleted, the derived class destructor is also called.
Example:
class Base {
public:
virtual ~Base() { std::cout << “Base Destructor”; }
};
Advanced OOPs Interview Questions in C++
You might also come across advanced Object Oriented Programming C++ interview questions like these:
- What is the diamond problem in C++, and how can it be resolved?
The diamond problem occurs in multiple inheritance when two derived classes inherit from the same base class, and a third class inherits from both. This results in ambiguity. It is resolved using virtual inheritance:
class A { public: void show() { std::cout << “A”; }};
class B : virtual public A {};
class C : virtual public A {};
class D : public B, public C {};
- How do smart pointers in C++11 relate to OOP principles?
Smart pointers (unique_ptr, shared_ptr, weak_ptr) improve encapsulation and resource management by automatically handling memory allocation and deallocation.
Example:
std::unique_ptr<int> ptr = std::make_unique<int>(10);
- Can you explain the concept of RAII (Resource Acquisition Is Initialization)?
RAII is a C++ design principle where resource allocation and deallocation are tied to object lifetime. When an object goes out of scope, its destructor releases resources automatically, preventing memory leaks.
- How does C++ handle dynamic casting, and when should it be used?
dynamic_cast is used for safely converting pointers or references of polymorphic classes. It is mainly used in downcasting.
Example:
Base* basePtr = new Derived();
Derived* derivedPtr = dynamic_cast<Derived*>(basePtr);
If the cast is invalid, dynamic_cast returns nullptr.
Also Read - Top 30+ C# OOPs Interview Questions and Answers
Tips to Answer CPP OOPs Interview Questions
Here are some helpful tips for answering OOPs in C++ interview questions:
- Be clear on encapsulation, inheritance, polymorphism, and abstraction.
- Explain concepts with short, relevant C++ code snippets.
- Answer directly without unnecessary details.
- If unsure, ask for clarification.
Also Read - Top 20 PHP OOPs Interview Questions and Answers
Wrapping Up
And this wraps up the 20 most important C++ OOPs interview questions and answers for 2025. Understanding these concepts will help you approach technical interviews with confidence. Looking for top C++ jobs in India? Hirist is the go-to job portal for tech professionals. Find the best opportunities today!
