Basic C Interview Questions You Need to Know for Your First Interview

As per Statista, C is used by more than 19% of all developers worldwide, which makes it an excellent choice for those who want to work as software developers.

C, one of the earliest languages, is widely regarded as the basis for all modern programming languages.

Hence, learning C helps to clear up many essential programming concepts for learners that prepare them for their jobs to solve real-world problems. Before that, you must crack the technical rounds of interviews first.

Read on if you are looking for some basic C interview questions to understand your grasp of the language and nail those interviews.

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C Interview Questions That Everyone Must Know:

1. Is C known as a mid-level programming language? Why?

C possesses traits of both lower-level (assembly level) and higher-level modern languages. Hence, C is frequently referred to as a middle-level language. A user may develop an operating system or a video game using the C language.

2. Describe some features of the C language that make it unique.

C is simple, efficient, portable, and machine independent. Known as a mid-level & structured Programming Language, it is extensible, has a function-rich library & dynamic memory management, and allows the use of pointers.

3. What is a token in C? How many types of tokens available in C?

A token is the most fundamental building block in the C language. Just like we cannot create words without alphabets, we cannot write C programs without using tokens. Six different types of tokens are available in C- Identifiers, Keywords, Constants, Operators, Special Characters, and Strings.

4. What is the use of printf() and scanf() functions and format specifiers?

printf(), as the name suggests, is used to print or display the program’s output. scanf() is used to get inputs from the user via the keyboard during or before a program’s execution.

Format specifiers are used to defining a specific type of input or output value. Some examples are %d (integers), %s (string), %c (character), %f (float).

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5. Explain the output of the expression 5[“abxdef”].

The correct answer would be ‘f’, as the string ‘abxdef’ is an array, and the expression asks the output of the element in the fifth place of the variety. Since C starts counting the elements from Zero instead of One, ‘a’ is the zeroth element, ‘b’ is the first, ‘x’ is the second, and so on… which means ‘f’ is the fifth element, and hence listed as the result.

6. What do you mean by a ‘built-in function’ in C?

Built-in functions, also known as library functions in C, are provided by default within the language to assist the developer in coding specific repeated tasks by using these functions instead of writing the whole code for each task separately.

Some examples of built-in functions in C are scanf(), printf(), strcpy, strlwr, strcmp, strlen, strcat, etc.

7. Why doesn’t C support function overloading?

After code in C is compiled, the symbol and function names need to be intact in the object code. Introducing function overloading can result in function name clashes, resulting in program execution failure. One way to avoid this is by using the name mangling as a preventive measure.

8. What is the difference between global int and static int declaration?

The scope is the difference here. A genuinely global variable will have a global scope and be accessible anywhere in the program; however, if you’d like it to be visible in other modules, you will need to use ‘extern int global_temp’ in different source files in case of a multi-file project.

Whereas a static variable has a local scope, its contents are not segmented within the memory stack. This means it can have less visibility than the global scope; however, it is still located in the ‘.bss’ segment of the compiled binary.

9. What do you mean by a ‘pointer’ in C?

As the name suggests, a pointer is simply a variable that stores the address of another variable and points to it. The variable’s value is stored within the variable, whereas the address can be stored in the pointer variable and used in multiple places throughout the program.

10. Out of n++ and n+1, which will execute faster and why?

The answer is n++ since it is a unary operation and needs just one variable, whereas n+1 is a binary operation and adds logical calculation overhead, which takes more time and delays program execution.

However, in modern machines, many factors such as processor speed, compiler efficiency, and code compaction can play a considerable role in execution. They will usually result in similar execution times for both operations.

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In The End

The C interview questions listed above cover some of the essential but important aspects of the C language, which may very well be asked in a C interview to test the candidate’s knowledge. We recommend you focus on understanding the concepts rather than memorising the answers. The interviewers want to know about your understanding of the subject after all.

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