10 Sample C++ Interview Questions and Answers

Since 1983, C++ has stood the test of time in the IT world—many web developers and software engineers still use it to this day. When it comes to landing an IT job, C++ proficiency is part of the equation. How can you prove to hiring managers that you have the right skills in C++? Prepare thoughtful and thorough answers to common C++ interview questions.

Easier said than done. But on the plus side, if you land a developer job, you’ll get to be a part of a fast-growing industry with tons of job security. Here’s the Bureau of Labor Statistics’ 10-year outlook for IT jobs:

• Web developer jobs – 23% growth
• Software developer jobs - 25% growth

Ready to get started? Learn how to ace these C++ interview questions to make the best first impression on the hiring manager.

C++ Interview Questions

1. What Is C++ and How Does It Compare to C?
2. What Are the Key Benefits of Using C++?
3. Describe the Data Types Used in C++.
4. Describe the Auto Keyword and When It’s Used in C++.
5. Explain What Operator Overloading Is in C++.
6. Explain the Difference Between a Struct and a Class in C++.
7. What Is a Constructor in C++?
8. Describe a Friend Class and a Friend Function in C++.
9. What Is Polymorphism and How Does It Work in C++?
10. Explain the Difference Between Compile Time Polymorphism and Runtime Polymorphism.

Basic C++ Interview Questions and Answers

The first half of these sample C++ interview questions and answers will focus on the basics of C++, including how to describe C++’s benefits, data types, the auto keyword, and operator overloading.

Question #1: What Is C++ and How Does It Compare to C?

C++ is a superset of the C programming language, but the two programming languages differ in some key ways. Include the following in your answer:

• A brief definition of C++.
• How C++ and C are similar.
• The key differences between C++ and C.

How You Could Answer

“C++ is a high-level programming language and an extension of the C language. Like C, C++ is a compiled language, which means that the source code is transformed into machine code before it gets executed on a computer.

One of the key differences between C++ and C is that C++ supports object-oriented programming, which allows for the creation of reusable blocks of code. C, on the other hand, is a procedural programming language that focuses on the sequence of instructions that need to be executed to complete a task.”

Question #2: What Are the Key Benefits of Using C++?

When you answer C++ interview questions about its benefits, include:

• Speed and performance.
• Memory manipulation.
• Data types and structures.

How You Could Answer

“One of the main benefits of using C++ is its high speed and performance. This makes it an ideal language for developing applications that require fast processing, such as operating systems and video games. It also allows for low-level memory manipulation, which is particularly useful in developing software that must interact directly with hardware.

C++ also has a wide range of data types and structures, making it a versatile language that developers can use for many different applications. It comes with built-in functions and libraries that can help simplify programming. C++ is also platform independent and can be used on Windows, Mac, and Linux.”

Question #3: Describe the Data Types Used in C++.

Data types in C++ help define the data held in variables and the operations that can be performed on that data. When answering C++ interview questions about data types, include the following details:

• The four types of data in C++.
• The purpose of each data type.

How You Could Answer

“C++ uses four data types:

• Primitive or basic data types: These include integer types, floating-point types, character types, boolean types, and void types.
• Derived data types: Also called “composite data types,” derived data types are built by using one or more primitive data types. These typically include arrays, structures, unions, and pointers.
• Enumeration: This data type assigns names to integer constants or defines sets of related constants that have a unique name.
• User-defined data types: These allow programmers to create new data types such as objects that encapsulate data and functionality. Since these data types are not built into C++, they must be defined by a programmer.”

Question #4: Describe the Auto Keyword and When It’s Used in C++.

The auto keyword in C++ helps simplify code, improve code readability, save time, and reduce the chances of an error when declaring variables. When potential employers ask C++ interview questions about the auto keyword, create your answer with these details in mind:

• What the auto keyword does.
• How it determines data types.
• The benefits of using the auto keyword.

How You Could Answer

“In C++, the auto keyword automatically declares variables where the initialized expression of them involves pointers to functions, pointers to members, and templates. This allows for more concise and readable code since programmers don’t need to explicitly define the data type of a variable.

When using the auto keyword, the compiler will determine the data type based on the value assigned to the variable. The resulting data will be substituted for the auto keyword. The auto keyword can only be used for local variables, not for function return types or class members.”

Question #5: Explain What Operator Overloading Is in C++.

Operator overloading helps programmers write more concise and readable code. Here’s how to explain what operator overloading is in C++:

• A brief description of an operator.
• What operator overloading in C++ entails.
• The key benefits of operator overloading.

How You Could Answer

“An operator in C++ is a symbol or set of symbols—such as +,-,*, and /—that perform operations on variables and values. Operator overloading is the process of defining new meanings for existing operators in C++. This means defining how an operator should behave when it’s applied to a data type. When you use operator overloading, operators can work with both built-in and user-defined data types.

Some of the benefits of operator overloading include code readability and reusability, custom functionality, and simplified expressions.”

C++ Coding Interview Questions

The remaining interview questions on C++ will cover structs, classes, constructors, friend classes, friend functions, and polymorphism.

Question #6: Explain the Difference Between a Struct and a Class in C++.

Structs and classes can both create objects, but they differ in important ways. Include the following in your answer.

• How a struct and a class are similar.
• The purpose of a struct and a class.
• Which ones contain public or private data members.

How You Could Answer

“Both structs and classes can be used to define user-defined data types and create objects. However, a struct is a simple data type that is used to group related data elements, while a class is more complex and usually includes data elements and member functions.

In a struct, all data members are public by default, which makes it more suitable for holding data that needs to be accessed by different parts of a program. Data members in classes are typically private and are used for more complex data structures that require encapsulation.”

Question #7: What Is a Constructor in C++?

Programmers use constructors in C++ to initialize class data members, create reusable objects, and handle exceptions during object creation. Include these details in your answer to C++ interview questions about constructors:

• What a constructor does in C++.
• The two types of constructors in C++.
• The benefits of using constructors.

How You Could Answer

“A constructor in C++ is a special member function that is called automatically when an object of a class is created. There are two types of constructors: default constructors that don’t take any arguments (or values declared within a function), and parameterized constructors that take arguments to initialize objects.

Constructors are responsible for initializing the data members of the object to their default values or the values passed by the client code. They share the same names as classes and don’t have any return types, not even void.

Programmers use constructors to create objects of a class without repeating the initialization code every time. This reduces the need for code duplication, makes the code more modular, and saves programmers time.”

Question #8: Describe a Friend Class and a Friend Function in C++.

When you work with C++, you’ll use friend classes and friend functions to access private and protected classes and implement data structures that require special access. Describe both a friend class and a friend function with the following details:

• What a friend class and a friend function do in C++.
• The benefits of using both.

How You Could Answer

“A friend class in C++ is a class that is granted access to the private and protected members of another class. This is done by declaring the other class as a friend in the first class’s declaration. Once a friend class is created, it can access the private and protected members of another class as if they were its own members.

This allows for more flexible and complex programming, but I would only use it sparingly since it can lead to tight coupling and reduce code maintainability.

A friend function is a function that is allowed to access the private and protected members of a class. It’s declared inside a class using the friend keyword but is not a member function of a class. It can be a standalone function, a member function of another class, or a global function.

A friend function is useful when programmers need to access a private data member of a class without using the object of that class.”

Question #9: What Is Polymorphism and How Does It Work in C++?

Polymorphism is one of the key C++ features and is a fundamental application development concept. When employers ask C# interview questions about polymorphism, demonstrate your knowledge by describing:

• Why C++ uses polymorphism.
• How programmers use polymorphism to write generic code.
• The benefits of polymorphism in C++.

How You Could Answer

“Polymorphism is a feature of C++ that allows different types of objects to be treated as instances of a single type. Programmers often use it to write generic code that works with various objects through inheritance and virtual functions. When programmers define virtual functions in a base class, derived classes can override those functions to provide their own implementation.

Once a function is called on an object, the virtual table of that object is consulted to determine which implementation to use. This allows for dynamic binding, which means that the appropriate function is chosen at runtime based on the object type, rather than at compile time based on the variable type.

Polymorphism also allows programmers to reuse code without having to rewrite it for each instance or specific use case. It also allows for flexible and adaptable code and simplified code maintenance.”

Question #10: Explain the Difference Between Compile Time Polymorphism and Runtime Polymorphism.

Employers may ask C++ interview questions that gauge your knowledge of compile time polymorphism and runtime polymorphism. Both polymorphisms share the ability to use the same code for different input types. However, they each work differently in C++. Differentiate between the two polymorphisms in your answer with these details:

• When each polymorphism occurs in a program.
• How each polymorphism is achieved.
• A key benefit of each polymorphism.

How You Could Answer

“Also known as static polymorphism, compile time polymorphism occurs during a program’s compilation. It’s typically achieved through functional overloading when multiple functions have the same name but contain different parameters or data types. The compile determines which function to execute based on the arguments passed to it. This can also be achieved through operator overloading.

Compile time polymorphism has a much faster execution rate than runtime polymorphism since it calls all methods during compile time.

Runtime polymorphism, on the other hand, occurs during a program’s runtime. It’s usually achieved through virtual functions, where a base class can define a function that’s overridden by its derived class. The executed function is determined at runtime based on the dynamic type of the object.

Runtime polymorphism provides more flexibility to programmers since everything is executed during runtime.”

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With preparation and practice, you’ll be able to develop your own answers to these C++ interview questions. In the meantime, upload your resume to Monster to connect hiring managers and find jobs that match your C++ skills quickly and efficiently. Then, browse our career advice articles on job search strategies, resume building, and much more.