Top 50 C Programming Interview Questions You Need to Master in 2024

Table of Contents

C programming interview questions are scary and spine-chilling for many. Yes, Friends! But a little prep can make you have vibes of repose and self-confidence.

Are you pondering how to answer C programming interview questions?

No Worries.

Indeed, you have landed on the correct page. Assuredly, this article will navigate you on how to master the C programming interview questions.

Probably by now, you might have completed scouring job portals for openings, polishing your resumes, penning the covering letters, and hence passed the first round of job hunting. Finally, it is time to face the difficult task: Y’all’s Job Interview.

Positively, get ready and scroll down to learn how to present yourself most professionally when you embark on your interview.

Hang in there and Break a Leg!

All about C Programming

C is the most popular computer programming language, considered the mother language of programming languages.

Though its origin dates back to the early 1970s, C is still the most preferred language as it is a procedure-oriented program.

All most all MNC companies use the C language due to its ease and flexibility.

On the other hand, it has expertise in low-level and high-level languages. While low-level languages construct system programming, high-level languages are necessary for application programming.

Moreover, C language supports various data structures, operators, constructors, and loop constructs.

Additionally, the C program has numerous features and helps to write other applications. For this reason, even after the invention of several new languages, the C language towers above all and remains versatile.

So why wait? Let us learn how to answer the questions bombarded by the interviewer.

Basic C Programming Interview Questions for Novices

Q6. Why is C Language known as the mother of all Programming Languages?

Ans: Dennis Ritchie invented the C language in 1972 to overcome the problems confronted by BASIC, B, and BPCL languages. By 1980, this became the most used language for mainframes, micro, and minicomputers. Further, many languages are designed based on C Language. Hence, it is known as the mother of all languages.

Q7. Name the four categories of C programming language.

Ans. The categories are –

Basic data types – Further divided into integer and floating-point types
Derived data types – defines variables and assigns discrete integer values only
Void data types – no value is available for this date type
Enumerated data types -Array types, pointer types, union types, function, and structure.

Q8. What is a stack?

Ans. A stack is a type of data structure where data is stored in stacks using the First In Last Out (FILO) approach. Only the top of the stack is accessible at any given instance. To retrieve the data, extract the upper part of the data first. Then the data stow inside the stack can be retrieved later.

Q9. What do you mean by PUSH and POP?

Ans. Storing data in a stack is referred to as a PUSH. While retrieving the data is referred to as a POP.

Q10. How do you insert quote characters (‘ and “) into the output screen in C programming?

Ans. Explicitly, quotes are a part of a printf statement. To insert the quote character into the output, use the format specifiers ‘ and ” for single and double quotes pro rata. It is a common problem faced by the fresher.

Q11. What is the difference between the = symbol and == symbol?

Ans. Mathematical operations often use the = symbol. To assign a value to a given variable, we use the = symbol. Alternatively, the == symbol is a relational operator that compares two values. = and == are familiarly known as “equal to” or “equivalent to.”

Q12. What is the modulus operator?

Ans. The modulus operator opens the remainder of a division which uses the percentage (%) symbol. For example, 17 % 4 = 1, meaning when you divide 17 by 4, the remainder is 1.

Q13. Do you know the function of s++ and ++s?

Ans. s++ is a single machine instruction that augments the value of s by 1, Post increment. However, we use ++s to carry out pre-increment.

Q14. What do you understand by calloc()?

Ans. In memory allocation calloc() is a dynamic function. It loads all the memory locations assigned to it with 0 value.

Q15. What is a token?

Tokens are the individual elements of a program. There are Six types of tokens in the C language. They are as follows:

Identifiers
Keywords
Operators
Constants
Strings, and
Special Characters

Q16. What is a C language’s built-in function?

Ans. Most commonly known as library functions, the C language provides the Built-functions to ease the programmers’ work by assisting them in doing some regular predefined tasks.

For instance, for print output or want of a programming terminal, we use printf() in the C program.

Most commonly used built-in functions in C are printf(), sacnf(), strcat, strcpy, strlwr, strcmp, strlen, strlwr, etc.

Q17. Tell me about the Header Files.

Ans. Indeed, C programming provides some standard header files. The function of Header files is to do mathematical or logical calculations or even print the output to the console or files. For example, the stdio.h header file has the relevant code for printing the output to the console or its associated code. Hence, stdio.h code has to be incorporated upfront in the program for its execution.

Q18. Is there any difference between text files and binary files?

Ans. The Text files contain data that humans can easily understand, such as numbers, letters, and other characters. Whereas, binary files contain language that only computers can interpret such as 1s and 0s.

Q19. What is Dangling Pointer Variable in C Programming?

Ans: A Pointer points to the memory location of an existing variable in C Programming. Explicitly, a Dangling Pointer Variable is the Pointer that points to the same memory location even after it got deleted.

Q20. What are the valid places for Break Control Statement application?

Ans: The places valid for the Break Control statement application are Switch Control Statements and inside a loop.

Intermediate C programming Interview Questions

Q21. Can you compile or execute a C program in the absence of a main()?

Ans: Notably, a program can be compiled but cannot be executed. To execute any C program, main() is required without fail.

Q22. Define <stdio.h>.

Ans. Stdio.h is a header file in C that contains prototypes and definitions of commands such as scanf and printf.

Q23. State the features of C Programming Language.

Ans: C programming is a top-notch language with bounteous built-in functions and operators to write variegated programs that are efficient and fast. The following are the features of the C language.

Q24. Mention different types of decision control statements.

Ans. In C language, decision control statements are if, if else, and nested if. There are three types of decision-making control statements in the C language. They are,

if statements
If….else statements
nested if statements

The following table explains the Syntax for each C decision control statement.

Decision control statements	Syntax & Description
If statement	Syntax: if (condition) { Statements; } Description: Here, if condition is true, then the respective block of code is executed.
if…else statement	Syntax: if (condition) { Statement1; Statement2; } else { Statement3; Statement4; } Description: Here when the condition is true, a group of statements is executed. Else part statements are executed if condition is false.
nested if statement	Syntax: if (condition1){ Statement1; } else_if(condition2) { Statement2; } else Statement 3; Description: Here, if condition 1 is false, then condition 2 is checked and statements are executed if it is true. If condition 2 as well gets failure, then else part is executed.

Decision Control Statements in C Programming

Q25. What are an r-value and l-value?

Ans.

A data value stored in memory at a given address is “r-value”, which is an expression with no value assigned to it. Hence, it exists only on the right side of an assignment operator(=).
“l-value” frequently referred to as an identifier, is a memory location used to identify an object, and it exists on either the right or left side of an assignment operator(=).

Q26. Explain the difference between ‘g’ and “g” in C.

Ans. In C programming language, single-quoted variables are termed as the character, while double-quotes variables are termed as a string. The string variables end with a null terminator. So this makes it a two-character array.

Q27. What is a File structure?

Ans. The file structure links the operating system and a program. The header file “stdio.h” defines the file and contains information about the file in use like its current size, memory location, and a character pointer to point the character that is currently in use. Thus, when we open a file it establishes a link between the program and the operating system.

Q28. Explain enum with an example.

Ans. An enum is a short form of “enumerations” which means “specifically listed.”

Being a special “class” Enum represents a group of constants (final variables which are unchangeable variables). Instead of class or interface, use the enum keyword to create it, also use a comma to separate constants, and notably, constants should be in uppercase letters.

Example:

Use Dot syntax to access enum constants:

Level myVar = Level.MEDIUM;

Q29. How to declare a Function in C Language?

Ans: Declaring a function in C language is as follows,

1 return_type function_name(formal parameter list)

2 {

3 Function_Body;

4 }

Q30. What is toupper()? Explain with an example.

Ans. toupper() is a function that converts lowercase words/characters into upper case.

1 #include<stdio,h&gt

2 #include<ctype

3 Int main()

4 {

5 Char c;

6 c=a;

7 Printf(“%c after conversions %c”,c, toupper/base

8 c=B

9 Printf(“%c after conversions %c”, c, toupper(c));

//Example

//Output:

a after conversions A

b after conversions B

Q31. Give an example of a type of entry and exit controlled loop in C programming.

Ans. – We check Entry controlled loop condition at the beginning. Example: For loop.

– On the contrary, the check for the Exit Controlled loop is at the end. Example: do-while loop.

Here the loop runs at least once.

Q32. What are the applications that are written in C language?

Ans. C language helps to write numerous applications like system programming, application programming, operating systems, compilers, development of interpreters, graphics, general utilities, etc.

Q33. Summarize data types.

Ans. Data types are the ways and means how the language programmers enter, store, and engineer the data in the program. Uniquely, C has a variety of data types, mainly classified into three types.

Primary data types – Eg: int, char, float, and void
Derived data types – Eg: arrays, functions, and C-pointers
User-defined data types – usually a combination of data types or heterogeneous data types

Q34. Name the operators in C.

Ans. Generally speaking, Operators in C are the symbols that do mathematical or logical operations on data. Different categories of operators present in C are:

Arithmetic Operators
Logical Operators
Relational Operators
Bitwise Operators
Assignment Operators, and
Ternary or Conditional Operators

Q35. What are Constants in C?

Ans. In C language, the Constants are entities or values whose value does not change during the course of the program. Constants can be classified as – primary and secondary constants that can further be divided into subtypes as shown in the figure below:

Q36. What is recursion in C?

Ans. Recursion or recursive function is where a function calls itself.

Q37. What are Preprocessors in C?

Ans. The programs that process the input data taken from another program, produce output, and send it to the compiler are known as Preprocessors. The C preprocessor is also known as CPP and is a macro preprocessor.

Advanced C programming Interview Questions

The following are the C programming interview questions for the aspirers with advanced C program knowledge. Check them out!

Q38. What is the stack area?

Ans. Arguments and local variables of a method are stored in a stack area. Until terminated it stays in memory.

Q39. Can we compile a program without a main() function?

Ans. Yes, using Macro we can compile a program without the main() function.

Example: #include<studio.h>

#define abc main

int abc ()

{

printf(“Hello World “);

return 0;

}

Q40. What are the Keywords in C?

Ans. Keywords in C are the reserved words that cannot be used as a constant name, variable name, etc. Explicitly, there are only 32 keywords in the C language that are as follows:

auto	Break	case	char	const	continue	default	do
double	else	enum	extern	float	for	goto	if
int	long	register	return	short	signed	sizeof	static
struct	switch	typedef	union	unsigned	void	volatile	while

KEYWORDS IN C

Q41. What are literals in C?

Ans. In general, Literals represent fixed values that are not modifiable. They are the constant values assigned to the constant variables.

For instance, const int =8; is a constant integer expression in which 8 is an integer literal.

There are four types of literals in C. They are as follows:

Integer literal
Float literal
Character literal
String literal

Q42. What is the acronym for ANSI?

Ans. The acronym ANSI stands for “American National Standard Institute.” This organization maintains an array of disciplines like computer languages, photographic film, data encoding, safety, mechanical parts, and more.

Q43. What is typecasting?

Ans: The process of converting one data type into another data type is known as typecasting. To store the floating type value to an int type explicitly requires converting the data type into another data type.

Syntax:

1 (type name) expression;

TYPECASTING

Q44. How can you print a string with the symbol % in it?

1 printf(&ldquo;there are90%%chances of rain tonight&rdquo;);

STRING WITH THE SYMBOL %

Ans: In C for the symbol % there is no escape sequence provided. So, to print % we should use ‘%%’ as depicted below:

Q45. What is a union?

Ans. The union is a user-defined data type. It allows storing myriad types of data in a solitary unit. However, it holds the memory of the largest member only. In a union, as all the members are allocated one common space, one can access only one variable at a time.

Syntax:

union union_name

{

Member_variable1;

Member_variable2;

Member_variable n;

}[union variables];

Q46. Explain the # pragma directive.

Ans: The Pragma Directive is a preprocessor directive used to turn on or off certain features. Types –

#pragma startup- helps to specify functions called upon program startup.
#pragma exit allows specifying functions called upon program exit.
#pragma warn warns the computer to suppress any warning or not.

Q47. What is Bubble Sort Algorithm?

Ans: A simple sorting algorithm called Bubble sort algorithm that repeatedly passes through the list until the list is sorted. While passing it compares adjacent elements and swaps them if found in the wrong order.

Q48. What is an infinite loop?

Ans. As the name indicates the loop runs continuously for an indefinite number of times.

Infinite for Loop:

for(;;){
//code to be executed
}

Infinite While Loop:

while(1){
//code to be executed
}

Infinite Do-While Loop:

do{
//code to be executed
}while(1);

Q49. Assume that in a certain block global variable and local variable had the same names. Now, can you access a global variable from that block where local variables are defined?

Ans. No. As the local variable always gets preference it is not possible in C to access global variable.

Q50. How to override a defined macro?

Ans. We can use #ifdef and #undef preprocessors to override a defined macro. It is as follows:

#ifdef A
#undef A
#endif
#define A 10

If macro A is defined, it will be first undefined using undef and later defined again using define.

Ah! This sums up our interview questions.

Intend to step-up your C skills? Or wish to learn C?

If your answer is yes, then join the best institutes that coach you to become a C professional.

Here are the Top institutes of India.

Henry Harvin
Udemy
Coursera
Codeacademy
Codingninjas
Vector Institution
Shiksha
C++ Institute
Besant Technologies
Koeing Solutions

Let’s Wind Up

Well, with this we sum up the Top 50 C Programming interview questions that you need to master. I hope these C Programming interview questions indeed helps you to face your upcoming interview with confidence. Further, if you want to polish yourself and abreast your knowledge, you may join the renowned institutes that teach the C language, attend or watch online tutorials and take some mock interview sessions.

Float a trial-balloon; make a dry run because there is always a light at the end of each tunnel.

FAQs

Q.1. What are the prerequisites of a job interview?

Ans. The Pre-requisites of an interview include-

Firstly, research the company to learn its values, mission & vision, benefits,
the hiring process, etc.
Dress professionally, decently, and impressively!
Never over-talk or under-talk,
Have honest conversations, honor the agreements that you make,
Be on time and ask questions, if any,
Remit a thank you note if it is all accomplished.

Q.2. What is a C Program?

Ans. Though its origin dates back to the early 1970s, C is still the most preferred language as it is a procedure-oriented program. Most MNC companies use the C language due to its ease and flexibility. On the other hand, it has expertise in low-level and high-level languages. While low-level languages construct system programming, high-level languages are necessary for application programming.

Q.3. Why C is considered the Mother of all programming languages?

Ans. C is the most popular computer programming language, considered the mother language of programming languages. C language supports various data structures, operators, constructors, and loop constructs. The C program has numerous features and helps to write other applications. For this reason, even after the invention of several new languages, the C language towers above all and remains versatile.

Q.4. Why learn C Program?

Ans. For many programming languages, ‘C’ is the foundation language. Surely, learning ‘C’ as the main language simplifies the learning of other programming languages. It shares the same concepts and can be used widely in various applications. Being a simple language it provides faster execution. The avenues for a ‘C’ developer in the current market are high. Hence, the C language is worth learning.

Top 50 C Programming Interview Questions You Need to Master in 2025

All about C Programming