C++ stands as a robust and versatile programming language, catering to a wide spectrum of applications, spanning from computer games and operating systems to databases and web browsers, developed by Bjarne Stroustrup at Bell Labs. Despite its enduring presence since the 80s, C++ maintains its relevance and remains among the most sought-after programming languages in the contemporary landscape.

Recognized for its complexity, C++ poses a formidable challenge for learners, making it imperative for hiring managers to approach the recruitment of C++ software developers with diligence and expertise. To facilitate this process, we have curated a set of interview questions to assist you in navigating the recruitment process/technical interview rounds.

After subjecting applicants to an initial programming skills assessment, such as the C++ (Coding): Language-specific Concepts test or C++ (Coding): Entry-level Algorithms test, and identifying the top candidates for an interview, you can enhance your question list with the inclusion of our C++ interview questions outlined below.

The questions are organized into three segments, tailored to different experience levels. Additionally, we've mentioned sample responses for each question, enabling you to assess your candidates' proficiency, even if you lack a professional programming background. Also, you can practise a set of similar questions found in the article below, on our platform now.

Top 10 beginners’ level C++ interview questions

These are specifically crafted for entry-level or junior C++ positions, targeting candidates with foundational knowledge of the programming language.

1. Mention the primary characteristics of C++ as a programming language.

C++ operates as a versatile programming language, showcasing support for a diverse range of applications across various domains. Additionally, it holds the status of a multi-paradigm programming language, accommodating object-oriented, procedural, functional, and generic programming frameworks.

Highlighted features also include its portability, potency, and intricacy, contributing to its reputation as one of the more challenging programming languages for learners.

2. Outline the key distinctions between C and C++.

While C and C++ share similarities in syntax, compilation, and basic memory attributes, several notable differences set them apart:

3. Identify the strengths of C++.

C++ boasts various strengths, including:

• Portability: C++ programs can seamlessly run across different operating systems.

• Multi-paradigm Flexibility: C++ provides extensive programming flexibility by accommodating object-oriented, generic, and procedural programming frameworks.

• Scalability: Recognized as a potent programming language, C++ excels in crafting resource-intensive programs and simpler, low-level applications alike.

4. Explain the concepts of class and object in C++.

A class in C++ is a user-defined data type comprising both data members and member functions. The data members represent the variables, while the member functions are designed to perform operations on these variables.

An object, on the other hand, is an instance of a class. As a class is a user-defined data type, an object can also be referred to as a variable of that specific data type.

In C++, a class is formally defined as -

5. Discuss the distinctions between structure and class in C++.

In C++, a structure shares similarities with a class, with a few distinctions, particularly regarding security. The key differences between a struct and a class are outlined below:

6. Elaborate on the concept of operator overloading.

Operator overloading plays a crucial role in manipulating operations for user-defined data types. Through operator overloading, the default meanings of operators such as +, -, *, /, <=, etc., can be customized.

For instance -

The subsequent code demonstrates the addition of two complex numbers using operator overloading -

7. Explain the concepts of call by value and call by reference.

In the call by value approach, a copy of the parameter is transmitted to the function. This involves assigning new memory for the duplicated values, and any modifications to these values do not impact the variable in the main function.

Conversely, in the call by reference approach, the address of the variable is passed, enabling access to the actual argument used in the function call. Consequently, modifications made to the parameter directly affect the corresponding argument passed during the function call.

8. Define Inheritance.

Inheritance is the mechanism for creating new classes, referred to as derived classes, by leveraging existing classes known as base classes. Derived classes inherit all the functionalities of the base class while having the capability to introduce new features and enhancements.

9. Outline the C++ Access Specifiers.

In C++, the access specifiers include:

• Public: Enables accessibility to all data members and member functions from outside the class.

• Protected: Grants access to data members and member functions within the class and to the derived class.

• Private: Restricts access to data members and member functions exclusively within the class, rendering them inaccessible from outside the class.

10. Understanding Constructors in C++

In C++, a constructor is a member function that is automatically executed whenever an object is instantiated. Constructors share the same name as the class to which they belong, allowing the compiler to recognize them as constructors. Notably, constructors do not have a return type.

In this example, the class A is defined with both a one-argument constructor and a zero-argument constructor. The main function demonstrates the instantiation of an object a using the one-argument constructor, passing the value 3 to initialize the object.

Top 10 intermediate level C++ questions for interviews

1. What do you understand by Copy Constructors

A copy constructor is a member function responsible for initializing an object by leveraging the attributes of another object belonging to the same class.

In this example, a custom copy constructor is defined for the class A to demonstrate the user-defined copy constructor. If a copy constructor is not explicitly defined, the default copy constructor is automatically invoked.

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

3. If class D is derived from a base class B. When creating an object of type D in what order would the constructors of these classes get called?

When creating an object of type D, derived from base class B, the constructors of these classes are invoked in a specific order. C++ constructs derived objects in phases, starting with the most-base class (at the top of the inheritance tree) and progressing to the most-child class. Consequently, the constructor of class B is called first, followed by the constructor of class D.

During destruction, the process is reversed. The destructor starts at the most-derived class and works its way down to the base class. Thus, the destructor of class D is called first, followed by the destructor of class B.

4. Is it possible to call a virtual function from a constructor? 

Indeed, calling a virtual function from a constructor is permissible. However, there is a nuanced difference in behavior in this scenario. When a virtual function is invoked, the virtual call is resolved at runtime, and it is the member function of the current class that gets executed. Therefore, the virtual machine doesn't operate within the constructor.

5. How does C++ handle memory management?

In C++, memory management is performed manually by the user since the language supports dynamic memory. Allocation and deallocation of memory are accomplished using the 'new' and 'delete' operators, respectively.

6. What are the five inheritance types in C++?

C++ features five distinct types of inheritance, each exhibiting its unique characteristics:

• Single inheritance: The derived class inherits from only one base class.

• Multiple inheritance: The derived class inherits from two or more base classes.

• Multilevel inheritance: The derived class is inherited from another derived class.

• Hybrid inheritance: Two or more different types of inheritance are combined.

• Hierarchical inheritance: Two or more derived classes stem from a single base class.

  
  

  
  

  7. What are the various variable types in C++?

In C++, variable types play a crucial role in determining the size and layout of the variable's memory, the permissible values within that memory, and the applicable operations. Here are some of the primary variable types in C++:

• char: stores single characters

• int: stores integers

• float: stores floating-point values

• double: stores floating-point values with twice the precision of float

• void: signifies the absence of a type

• bool: stores a value that is either 'true' or 'false'

8. What distinctions exist between a shallow copy and a deep copy in C++?

Both shallow copies and deep copies capture information about an object, but a deep copy provides a more detailed replication. While a shallow copy merely duplicates pointers, a deep copy includes a duplicate of any data structure present in the original object.

9. What purpose does the 'friend' function serve in C++?

The 'friend' function in C++ is utilized to access private and protected data of class members, even when declared outside that class. It proves beneficial when private data of a class needs to be accessed without using objects within the class.

10. What constitutes function overriding in C++?

Function overriding in C++ is the process by which a derived class is endowed with the same function as its corresponding base class. This exemplifies compile-time polymorphism, contributing to memory efficiency and enhancing code reusability.

11. Distinguish between an external iterator and an internal iterator in C++.

Iterators, serving as objects pointing to elements within a container, come in two forms in C++. External iterators are associated with objects from a distinct class, while internal iterators are implemented through member functions within the object's class.

Top 10 expert level C++ questions for interviews

1. How can C++ programs undergo optimization?

Optimizing C++ programs involves employing various techniques, including:

1. Utilizing superior algorithms

2. Reducing memory allocation

3. Employing advanced compilers

4. Choosing optimal data structures

5. Implementing multithreading

2. What is the 'diamond problem' associated with multiple inheritance in C++?

The 'diamond problem' arises in multiple inheritance when two parent classes inherit from the same grandparent class, and both of those parent classes are then inherited by a single child class, forming a diamond-shaped hierarchy. This configuration introduces ambiguities during compile-time.

To resolve the diamond problem, virtual inheritance can be employed. By declaring the base classes as virtual, issues related to incorrect copying during inheritance can be mitigated.

3. How is exception handling executed in C++?

Exception handling in C++ involves segregating code that deals with exceptional circumstances from the rest of the program. This is achieved using three keywords, typically used in tandem:

• try: Identifies a block of code where specific exceptions may occur.

• catch: Handles and catches exceptions within the code.

• throw: Throws an exception when a problem is detected.

4. What are the diverse methods for passing parameters to functions in C++?

In C++, various parameter passing techniques exist, with two primary methods:

1. Pass by value: Changes to the parameter do not affect data in the calling function.

2. Pass by reference: Changes to the parameter also apply to the original variable.

5. What is a virtual destructor in C++?

Virtual destructors in C++ ensure orderly memory deallocation when deleting derived subclasses. They are particularly useful when deleting an instance of a derived class through a pointer to the base class. Virtual destructors aid in freeing up memory space and preventing memory leaks.

6. What is type erasure in C++ and how is it implemented?

Type erasure in C++ involves concealing various concrete types behind a unified, generic user interface. Common methods for type erasure in C++ include:

1. Function pointers

2. Virtual functions

3. void*

7. What are the diverse types of preprocessor directives in C++?

Preprocessor directives offer instructions to the compiler for processing information before compilation begins. Three common preprocessor directives are:

• #define: Creates a macro.

• #undef: Undefines existing macros.

• #pragma: Turns on or off specific special-purpose features.

8. How is multithreading achieved in C++?

To initiate a new thread in C++, users must first include the <thread> header for access to the std::thread object. Then, a callback mechanism is attached to the original thread for creating the new thread. This establishes the relationship between the threads, and the available callback mechanisms include:

1. Function pointer

2. Function object

3. Lambda function

9. What distinguishes variable declaration from variable definition in C++?

Declaration in C++ offers the compiler basic information about a variable's name and value type, while definition provides complete information, including fields, methods, and storage location. Definition involves memory allocation, unlike declaration. Variables and functions can be declared multiple times but defined only once.

10. What are the pros and cons of recursion in C++?

Recursion, involving a function calling itself, offers advantages such as reduced coding effort, enhanced clarity, and effective problem-solving, especially for tree traversal. However, it comes with disadvantages, including increased memory usage and relatively slower execution.

11. What are the main distinctions between a list and a vector in C++?

While lists and vectors are both sequential containers in C++, they differ in several aspects:

1. Vectors store elements in contiguous memory locations, whereas lists use non-contiguous memory locations.

2. Vectors provide random access, while lists do not.

3. Vectors are thread-safe, whereas lists are not.

4. Vectors require more memory storage compared to lists.

How can Redrob help you?

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The platform not only offers an extensive repository of questions covering various aspects of C++, but it also provides a realistic interview experience to enhance your problem-solving abilities and boost your confidence. Additionally, Redrob serves as a bridge between your preparation and dream job aspirations, offering a seamless application process to apply for your desired positions directly through the platform. Elevate your C++ proficiency, sharpen your interview skills, and take a significant step towards securing your dream job by exploring all that Redrob has to offer.