Are you a hiring manager, HR manager, or recruiter tasked with recruiting top C developers for your organization? If the answer is yes, this article is for you.
Finding the right developers has never been easy – but as a result of the pandemic, talent shortages are becoming even worse. In 2021 there was a 43% decline in enrollment for Computer and Information Science programs, which means there’s far more competition for great junior developers – and it’s only expected to become stronger.
That’s one of the main reasons why it’s crucial to have a streamlined and objective hiring process enabling you to recruit the best talent quickly and efficiently – and why you must ask the right C interview questions and be able to accurately evaluate applicants’ responses.
It’s also key to use a robust skills testing platform like TestGorilla to help with candidate screening before the interview stage. For example, you can use the C Entry-Level Algorithms test for entry-level developers or C Language-Specific Concepts test for mid-level developers.
Developers and engineers who do well on our C tests have strong skills in C. If C is one of the programming languages your organization is using, hiring the best C developers is instrumental for its growth over the next few years.
Once you’ve used skills tests to identify the best candidates, you need to interview them. Here are 51 C interview questions along with sample answers to help you pick the cream of the crop.
Execution speed is faster with Macro. In function, time is spent passing control from one function call to the next. In macro expression, zero time is spent passing control.
This is a variable that either stores or points to the address of another variable. A normal variable stores the variable value while the pointer variable stores the variable address.
Also known as a double pointer, a pointer to pointer is used to store another pointer’s address. The variable’s address is stored in the first pointer, while the first pointer’s address is stored in the second pointer.
No. C does not allow function overloading in the code.
This is software that sends a source file to be compiled after processing it. It can include line control, header files, conditional compilation, and macro expansions.
C has several key features that make it a powerful programming language. C:
Is very simple, fast, and efficient
Makes use of pointers
Is machine independent/portable
Is a structured, mid-level programming language
Features a comprehensive library of functions
Has dynamic memory management
The key difference between static int and global int declaration is scope. A global variable can be seen everywhere within the program.
There is no difference between char const* p and const char* p. You may choose char const* p over const char* p as the semantics are from right to left. But there is no difference in their function.
C sits between low-level (assembly-level) languages and high-level languages, so it can be used for the programming of systems (such as operating systems) as well as applications (e.g., spreadsheet applications).
C combines the best features of high-level languages with the flexible nature of low-level languages.
You use scanf() to read data from a standard input stream, usually a keyboard. You use printf() to print the display output.
Format specifiers are used for input and output purposes. They allow the compiler to understand the data type in a variable while printing via printf() function and receiving input via scanf() function.
Here are some examples of format specifiers for scanning and printing purposes:
%c is used for scanning and displaying a character value
%d is used for scanning and printing an integer value
%f is used for scanning and displaying a float value
%s is used for scanning and printing a string
Recursion is the repetition of items in a self-similar way. If a program allows a function to call itself, it is known as recursion (or recursive function).
Typecasting is a process where a variable that belongs to one data type is changed into another. Depending on what you want your program to do, the compiler will automatically change one data type to another.
Also known as enum in C, an enumeration is a user-defined data type consisting of constant integers or integrals with user-assigned names. Enum in C makes the entire program easy to understand and maintain.
Built-in functions make developers’ lifes easy by assisting them in doing commonly-used, predefined tasks. Built-in functions are also known as library functions.
Some popular built-in functions are:
You use the #line to reset the filename and line number in the code.
You use the register storage specifier when you’re using a variable regularly. You should declare it with the register storage specifier so that the compiler allocates a CPU register. This will increase the speed of looking up that variable.
Tokens are the smallest single elements you can use when creating a program.
The six token types in C are:
A near pointer is 16 bits in size and can access 64Kb of data at a time. It can’t access an address beyond that particular data segment. An arithmetic operator can increment or decrement the address range.
A far pointer is 32 bits in size and can access all 16 segments. It can store segments and offset addresses. When you increment or decrement a far pointer, you only change the offset part.
A huge pointer is similar to a far pointer as it is 32 bits in size. The main difference is that it can access even bits stored outside of the segment, which isn’t possible with far pointers.
A memory leak happens when you have created memory in a heap but forgot to delete it. The program does not use this memory and it’s reserved for no reason. Too many memory leaks will harm the computer’s performance (e.g., slowing it down, causing crashes in applications, and so on).
There are a few strategies to avoid memory leaks; for example, you can:
Use a counter that monitors the allocation of memory
Write the free function after every calloc or malloc
Don’t work on the original pointer and instead work on a copy of the pointer
Make sure you write proper comments in every code section
Free memory from child to parent (and not vice versa) to avoid orphaning memory
By default, it is called by value.
Both are memory allocation functions. Calloc() can take two arguments, while malloc() can only take one argument (the number of bytes).
This is impossible in C. The local variable always gets preference.
Dangling pointers point to memory that is already freed. There is no allocation of storage anymore. It may cause a segmental fault if you try to access it.
A dangling pointer points to memory that has been deallocated, whereas a memory leak is when you’ve forgotten to deallocate memory.
You can use this keyword to define synonyms or aliases for an existing type. Typedef can shorten code, whether it’s a simple integer or a complex structure declaration.
There are three main types of decision control statements in C, which are:
Enum is usually better than #define because of its:
Better debugging capabilities
Improved program readability
This is the process of allocating memory during run time or execution time.
Dynamic memory allocation (DMA) is ideal:
When you don’t know how much memory you need before executing a program
When you want efficient memory use
When you want a data structure with no upper memory space limit
For easy dynamically created list insertions and deletions
When you want to use the concept of structures and linked lists
The four dynamic memory allocation library functions are:
L-value is short for locator value. It represents an object that takes up memory space and has an identified location (in other words, an address).
R-value is an expression that doesn’t represent an object that takes up memory space and therefore does not have an identified location.
To link a program with the OS, you use the file structure. The standard input/output header file defines the file with information such as memory location, current size, and so on. It will point to the character you are currently opening via a character pointer. A link is established between the program and OS when opening a file.
A struct allows the simultaneous accessibility of all complex data structures because it allocates separate memory locations of each structure stored in the memory block. In union, the same location is used.
When using #include <…>, the preprocessor will first look for the filename in a predefined system directories list. After that, it will look at directories as instructed by the user.
When using #include “…”, the preprocessor will first look for the filename in the same directory as the file that contains the directive. It will then follow the search path you’ve defined for the #include <…> form.
‘G’ and “g” are different in the following way:
‘g’ refers to variables identified as character
“g” refers to variables identified as string
The problem with gets() is that it will not check if the variable size is under the maximum data type size. This can mean that input is written into memory where it shouldn’t be. It could also leave the system susceptible to buffer overflow.
They can operate on ints and chars.
A dynamic data structure (DDS) is a collection or organization of data stored in memory that can shrink or grow in size. This allows you to control how much memory is used.
DDS can change size by allocating or deallocating memory from the heap as and when needed. DDS gives you the flexibility to adjust how much memory is consumed by software programs.
To check if a linked list is circular, you need to traverse the linked list. The list is circular if you verify that the node points to the head.
You need to use the #undef preprocessor, which will undefine (i.e., override) a macro that’s been previously defined.
A semicolon (;) will act as a border between two sets of statements. It aids in how the compiler parses/reads the code and how well it breaks down the code into sets of statements.
Source codes are instructions written using human-readable programming language, whereas object codes are sequences of statements in machine language.
Header files contain macro, data type definitions, function definitions, and more. These definitions can be imported via the #include directive to the source code.
Hiring managers face a complex challenge: There’s a general shortage of skilled developers. At the same time, demand for specific coding languages, such as C, is increasing.
Despite being around since the early 70s, the C programming language is still in high demand because it combines low-level and high-level language features, which makes C very flexible.
Therefore, attracting the best C developers and engineers is crucial to the success of your organization.
One way to identify and hire the best talent is to ask good C interview questions at the interview stage. Combine this with skills tests prior to interviews, and you’ll see your time to hire drop significantly.
With TestGorilla, not only can you test your candidates for particular coding languages such as C, but you can also test for knowledge of the basic principles of software engineering with the Software Engineer test, or also assess applicants’ soft skills or cognitive abilities.
With TestGorilla by your side, you’ll be sure to hire the most talented C developers and engineers to beat the competition. Try it for free.
1. The 2021 Software Developer Shortage Is Coming. Communications of the ACM. Retrieved September 14, 2022
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