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10 C++ Interview Questions to Practice

C++ is a programming language that was developed by Bjarne Stroustrup at Bell Labs in 1982 as an extension to the C programming language. Anything you can do in C, you can also do in C++ and then some.

One reason developers love to use C++ is because it uses object-oriented features, which gives more flexibility while building applications.

C++ is used for many types of development projects, including game development, machine learning, operating systems, GUI applications, smart devices, database development, embedded systems, and much more. And, if you’re pursuing a job in any of these areas, you’ll probably be expected to know C++.

An interview for a C++ developer job will have a few parts to it. There may even be multiple interviews. The first interview is just to get to know you. It may be with a recruiter, and there’ll be few (if any) technical questions. After you and the recruiter decide the job might be a good fit for you, the next step is the technical interview.

In this article, we’ll cover the types of technical questions you may be asked during a C++ interview.

Since there’s a wide variety of questions that could be asked at the interview, you might not run into these exact questions, but they’ll give you a good idea of what to prepare for. Studying them will also give you confidence that you can answer whatever the interviewer has in store for you.

1. What are some differences between C and C++?

If you’re asked this question during your interview, here are some concepts to cover in your response. Keep in mind that there are quite a few other differences, but these are the main ones.

C++ is a superset of C. Most C programs will run in C++. C is only a procedural language, and C++ is both procedural and object-oriented.

C++ also supports exception handling at the language level, while in C, you have to use conditionals to handle errors. C++ supports references and C does not.

2. What are the differences between references and pointers in C++?

References and pointers are similar because both can be used to change the local variables of one function from inside another function. Both can make programming more efficient by saving the memory needed to copy an object and create another variable.

But there are differences. A reference can’t be changed later to reference another object, while a pointer can. References also can’t have a NULL value, while pointers can. And, references must be initialized when declared, while pointers do not.

3. What is a namespace in C++?

C++ added namespaces that C doesn’t have. Namespaces give you another level of hierarchy in your code beyond classes and methods.

You can assign classes to namespaces in your C++ code to organize your code into modules. When you use namespaces, classes within a namespace can have the same name as classes within other namespaces without causing errors or name clashes.

4. What is meant by the std namespace in C++?

The std namespace is where all the standard libraries that come with C++ are stored. To use methods in the C++ standard library, you can either add namespace std; to your C++ files or prefix all the methods you want to use from the C++ standard library with the std namespace like std::string.

5. What is a constructor in C++?

A constructor is a method in a C++ class that has the same name as the class. This method is automatically called when an object of this class is created. Programmers put the functionality needed to instantiate the object in the class, like setting class variables and configuration values.

6. What is a destructor in C++?

A destructor is a method in a C++ class similar to a constructor, except it’s called whenever the object will be destroyed. This method has the same name of the class with a ~ symbol in front of it.

So, in a String class, the name of its destructor would be ~String. This is where a C++ developer deallocates the memory used in the object and does other cleanup tasks.

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

In C++, a struct and class are similar but have some differences. Members of a struct are public by default, and members of a class are private by default.

When deriving a struct from a struct or class, the default access specifier for a base class or struct is public. When you derive a class, it’s private.

8. What is a virtual function in C++?

A virtual function is a member function of a base class that can be redefined in a class derived from it. Virtual functions are declared with the virtual keyword. With virtual functions, C++ determines which function should be invoked based on the type of object that’s pointed to by the base class pointer.

9. What is an inline function in C++?

When you create an inline function in C++, the compiler puts a copy of the function wherever it‘ll be called in your program instead of referring to the function definition. This feature can add performance to your program by reducing the overhead involved in traditional function calls.

10. What is the difference between a call by value and a call by reference?

If a C++ method is called by value, then the parameters are passed to the function by their value and not by a reference to the original variable. If the value is changed in the method, the original variable doesn’t change.

If a C++ method is called by reference, then we pass a reference to the original value into the method, and when that’s modified within the method, the original variable is modified.

Learn more about C++

Technical interviews have many parts and take some preparation. To prepare for the technical questions in a C++ interview, it’s a good practice to review as many questions as you can before the day of the interview. We hope the questions above will help you get started.

Another thing you can do to prepare is to practice C++ coding challenges. If you feel you need a refresher after reviewing these interview questions or trying some of the coding challenges, then we can help out with that. Our Learn C++ course will teach you the fundamentals of this powerful programming language so you can ace that interview.And, if you still need more tips for passing technical interviews, check out our Career Center.

C++ Courses & Tutorials | Codecademy
C++ is a very popular language for performance-critical applications that rely on speed and efficient memory management. It’s used in a wide range of industries including software and game development, VR, robotics, and scientific computing.

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Stephan Miller

Stephan Miller

Stephan Miller has been a full-stack, mobile, and machine learning developer for two decades and has written code for companies both big and small, both startups and established businesses.

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10 C++ Interview Questions to Practice
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