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The C programming language is a high-level, general-purpose coding language first developed at Bell Labs in the early 1970s by Dennis Ritchie. It has since become one of the most widely used programming languages, providing the foundation for other languages such as C++, C#, and Objective-C. Its popularity stems from its efficiency and flexibility, as it can be used for a variety of tasks including systems software, game development, and web applications. The UNIX operating system was notably written in C. As per IEEE Spectrum's annual rankings (2021), it remains one of the top programming languages due to its relevance and adaptability.

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

First 20 minutes

General C app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in C application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

How would you declare a pointer in C?

To declare a pointer in C, you would use the following syntax: 'type *pointerName;'. For example, 'int *p;' declares a pointer to an integer.

What are the different types of storage classes in C?

The different types of storage classes in C are auto, register, static, and extern.

Describe the difference between a struct and a union in C.

The main difference between a struct and a union in C is that a struct allows for multiple members to be stored at the same time, while a union only allows for one member to be stored at a time.

How would you use a function pointer in C?

A function pointer in C can be used to call a function or to pass a function as a parameter. It is declared like a normal pointer, but with a function signature.

What are the different types of loops in C?

The different types of loops in C are the for loop, the while loop, and the do-while loop.

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What you’re looking for early on

Does the candidate demonstrate a solid understanding of C language fundamentals?

Has the candidate shown proficiency in problem-solving?

Is the candidate able to communicate effectively about technical concepts?

Has the candidate demonstrated knowledge of memory management in C?

Next 20 minutes

Specific C development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

Describe the difference between malloc() and calloc() in C.

The main difference between malloc() and calloc() in C is that malloc() allocates a block of memory without initializing it, while calloc() allocates a block of memory and initializes it to zero.

How would you handle errors in C?

Errors in C can be handled using various techniques such as returning special values, setting a global error code, or using exceptions with setjmp and longjmp functions.

What are the different types of operators in C?

The different types of operators in C are arithmetic operators, relational operators, logical operators, bitwise operators, assignment operators, and special operators.

Describe the difference between a linked list and an array in C.

The main difference between a linked list and an array in C is that an array is a static data structure, while a linked list is a dynamic data structure.

How would you implement a stack in C?

A stack in C can be implemented using an array or a linked list. The stack has two main operations: push, which adds an element to the top of the stack, and pop, which removes an element from the top of the stack.

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At this point, a skilled C engineer should demonstrate strong problem-solving abilities, proficiency in C programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

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

What does the following code do?
#include 

int main() {
    printf("Hello, World!\n");
    return 0;
}
This code prints the string 'Hello, World!' to the console.
What does the following code do?
#include 

int main() {
    int a = 5;
    int b = 10;
    int c = a + b;
    printf("%d", c);
    return 0;
}
This code declares two integer variables 'a' and 'b', assigns them the values 5 and 10 respectively, adds them together, assigns the result to a third integer variable 'c', and then prints the value of 'c', which is 15.
What will be the output of the following code?
#include 

int main() {
    int arr[5] = {1, 2, 3, 4, 5};
    for(int i = 0; i < 5; i++) {
        printf("%d ", arr[i]);
    }
    return 0;
}
This code will print the numbers 1 to 5, each followed by a space.
What does the following code do?
#include 
#include 

void *printHello(void *threadid) {
    printf("Hello from thread %d\n", threadid);
    pthread_exit(NULL);
}

int main() {
    pthread_t thread;
    int rc = pthread_create(&thread, NULL, printHello, (void *)1);
    if (rc) {
        printf("Error:unable to create thread, %d\n", rc);
        exit(-1);
    }
    pthread_exit(NULL);
    return 0;
}
This code creates a new thread and runs the 'printHello' function in that thread. The function prints a message that includes the thread ID, which is passed as an argument when the thread is created.

Wrap-up questions

Final candidate for C Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle C application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What are the different types of file operations in C?

The different types of file operations in C are file open, file read, file write, and file close.

Describe the difference between a preprocessor directive and a function in C.

The main difference between a preprocessor directive and a function in C is that a preprocessor directive is processed before the compilation of the program, while a function is processed during the execution of the program.

How would you implement recursion in C?

Recursion in C can be implemented by having a function call itself within its own definition. The base case is the condition that stops the recursion.

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.

C Consultive assessments

C Application Conversion Assessment C Application Integration Assessment C Data & Database Integration Assessment

Custom C development projects

Custom C App Conversion C Custom App Development Process App UI Design for C Facelifts

Hiring guide for C Engineers

C Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

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

C Consultive assessments

Custom C development projects