C++ Developer Hiring Guide

Hiring Guide for C++ Engineers

Ask the right questions to secure the right C++ talent among an increasingly shrinking pool of talent.

C++ is a high-level, general-purpose programming language, created by Bjarne Stroustrup at Bell Labs in 1979. It was developed as an extension of the C language, with additional features such as classes and objects, supporting the concept of object-oriented programming. C++ has been widely adopted in software engineering and is used for a variety of tasks, including system/software development and game programming. Its efficiency and flexibility have made it one of the most popular languages in the world. The language has been standardized by the International Organization for Standardization (ISO), with its latest version being C++20.

First 20 minutes

General C++ knowledge and experience

The next 20 minutes of the interview should attempt to focus more specifically on the development questions used, and the level of depth and skill the engineer possesses.

What is the purpose of the 'this' pointer in C++?

'This' is a keyword in C++ which is a pointer that points to the object which invokes the member function.

How would you use a function pointer in C++?

A function pointer can be declared and used like this: 'int (*funcPtr)(int,int);' This declares a pointer to a function that takes two integers as argument and returns an integer. You can assign a function to this pointer using 'funcPtr = &func;', where 'func' is a predefined function.

Describe the difference between a class and a structure in C++.

In C++, the primary difference between a class and a structure is the default access level. For a class, members are private by default, while for a structure, they are public.

What are the different types of inheritance in C++?

C++ supports several types of inheritance: single, multiple, multilevel, hierarchical, and hybrid inheritance.

How would you declare a pointer in C++?

You would use the asterisk (*) symbol to declare a pointer in C++. For example, 'int* p;' declares a pointer to an integer.

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What youre looking for early-on

Has the candidate provided examples of past projects or accomplishments that demonstrate their skills and abilities?

This is important because it provides evidence of the candidate's capabilities and gives an insight into how they work on real-world projects.

Does the candidate exhibit a passion for programming and continuous learning?

This is critical because the field of software development is constantly evolving and successful developers need to be able to keep up with new technologies and techniques.

Does the candidate have experience with the tools and technologies commonly used in your organization?

This would be beneficial as it would reduce the amount of training needed and allow the candidate to contribute more quickly.

Is the candidate able to communicate effectively about technical topics?

This is vital because developers often need to collaborate with others and explain their work to non-technical stakeholders.

Has the candidate shown problem-solving skills during the interview?

This is important because programming often involves solving complex problems and the ability to do so effectively is a key skill for a developer.

Does the candidate demonstrate a strong understanding of C++ concepts?

This is essential because the candidate needs to have a deep understanding of the language to be able to design and implement efficient software.

Next 20 minutes

Specific C++ development questions

The next 20 minutes of the interview should attempt to focus more specifically on the development questions used, and the level of depth and skill the engineer possesses.

Describe the difference between the 'delete' and 'free' functions in C++.

'Delete' is an operator in C++ which deallocates memory and calls the destructor for the object, while 'free' is a function in C that just deallocates memory without calling the destructor.

What is a virtual function in C++?

A virtual function is a member function that you expect to be redefined in derived classes. When you refer to a derived class object using a pointer or a reference to the base class, you can call a virtual function for that object and execute the derived class's version of the function.

How would you handle exceptions in C++?

C++ provides a mechanism to detect and handle runtime anomalies or exceptions. You can use the 'try', 'catch', and 'throw' keywords to work with exceptions. You wrap the code that could potentially throw an exception inside a 'try' block, and handle the exception in a 'catch' block.

What are templates in C++?

Templates are a feature of the C++ programming language that allows functions and classes to operate with generic types. This allows a function or class to work on many different data types without being rewritten for each one.

Describe the difference between overloading and overriding in C++.

Overloading refers to having multiple functions with the same name but different parameters, while overriding refers to a subclass providing a different implementation for a function that already exists in its superclass.

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The ideal back-end app developer

What you’re looking to see on the C++ engineer at this point.

A skilled C++ engineer should demonstrate proficiency in understanding and using advanced C++ concepts, problem-solving abilities, and debugging skills. Red flags include over-reliance on libraries without understanding their workings, lack of knowledge about memory management or inability to explain complex algorithms or data structures.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with C++.

What does the following code do?

int x = 10; 
int y = 20; 
int z = x + y;

This code declares three integer variables x, y, and z. It assigns 10 to x and 20 to y. Then it adds x and y and assigns the result to z. So, z will be 30.

What will be the output of the following code?

for(int i = 0; i < 5; ++i) 
    std::cout << i; 

This code will output the numbers 0 through 4. This is because it's a loop that starts at 0 and continues as long as i is less than 5, incrementing i by 1 at the end of each iteration.

What does the following code do?

int arr[5] = {1, 2, 3, 4, 5}; 
int sum = 0; 
for(int i = 0; i < 5; ++i) 
    sum += arr[i]; 

This code calculates the sum of all elements in the array. It initializes an array of 5 integers, then it iterates over the array adding each element to the sum variable. At the end, sum will be the total of all elements in the array.

What does the following code do?

void foo() 
    // do something 
int main() 
    std::thread t(foo); 

This code creates a new thread that executes the function 'foo'. The main thread waits for this new thread to finish execution before it continues. This is done using the 'join' function, which blocks the calling thread until the thread t finishes its execution.

What does the following code do?

class MyClass 
    int x; 
    MyClass(int val) : x(val) {} 
int main() 
    MyClass obj(10); 
    std::cout << obj.x; 

This code defines a class named 'MyClass' with a public integer member 'x'. It also defines a constructor for the class that takes an integer argument and initializes 'x' with it. In the main function, it creates an object of 'MyClass', initializes 'x' with 10, and then prints the value of 'x'.

What will be the output of the following code?

int x = 0; 
    if(x == 0) 
        throw x; 
    x = 1/x; 
catch(int e) 
    std::cout << 'Error'; 

This code will print 'Error'. It checks if x is zero and if so, throws an exception. The exception is caught in the catch block and 'Error' is printed to the console.

Wrap-up questions

Final candidate for C++ role questions

The final few interview questions for a C++ candidate should typically focus on a combination of technical skills, personal goals, growth potential, team dynamics, and company culture.

How would you implement a singleton class in C++?

A singleton class can be implemented by making the constructor private, and creating a static method that creates the instance only if it doesn't already exist. This ensures that only one instance of the class can be created.

Describe the difference between 'new' and 'malloc' in C++.

'New' is an operator in C++ which allocates memory and calls the constructor for the object, while 'malloc' is a function in C that just allocates memory without calling the constructor.

What is a copy constructor in C++?

A copy constructor is a member function which initializes an object using another object of the same class.

How would you implement polymorphism in C++?

Polymorphism in C++ can be implemented through the use of virtual functions. A base class pointer can point to objects of any of its subclasses, and when a virtual function is called through this pointer, the corresponding function in the derived class gets executed.

What is the purpose of namespaces in C++?

Namespaces are used to organize code into logical groups and to prevent name collisions that can occur especially when your code base includes multiple libraries.

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C++ application related

Product Perfect's C++ development capabilities

Beyond hiring for your C++ engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in C++ projects, and can engage in multiple capacities.