C interview questions

Frequently Asked C Interview Questions Answers

Before directly going to the, C Interview Questions and answers, you need to have a faint idea of what C language is. Secondly, you should know how to write the codes for a given problem. The C programming language is basically used in the development of system applications that majorly contributes to operating systems.

The operating system not necessarily has to be Windows, instead, it could be Unix and Linux as well. The language in which UNIX applications along with Operating systems and C compiler is being written is called C language.

With this, you can proceed with the C Interview Questions, but, start from the very basic. Make sure, you have good theoretical knowledge along with practical implementation. The first question in the series of C Interview Questions is as follows.

Read these Python Interview Questions blog that will qualify you for Python Interviews with the most possible questions you are going to be asked in 2020.

Name the different storage class specifiers in C?

To answer this question, one should not take that much of time and promptly answer that the storage class specifiers in C are auto, register, static and extern.

What do you know about the NULL pointer?

You should start by telling that NULL POINTER does not point to any object or function. A developer initializes pointers as a NULL POINTER only if they are not aware of their value at the time of being declared. But, a pointer is actually NULL at the time when memory is being pointed by its deallocation amidst the program.

Explain what is a Dangling pointer

Dangling Pointers do not point to an actual memory location. These pointers appear when an object is deleted or deallocated, without modifying the value of the pointer.

What is a memory leak?

A memory leak occurs when programmers produce a memory in heap and ignore to delete it. Memory leaks are serious problems for programs such as daemons and servers which by definition never stop.

Could you explain Modular Programming?

Modular Programming is nothing but a division of programs into sub-programs or sub-modules or sub-functions. This subdivision helps in achieving the given task and is a modular approach. Generic function definition gives the ability to re-use the functions, like built-in library functions.

You could read more questions like that so that you could prepare yourself for the C Interview Questions that are theory-based. However, practical knowledge and practical implementation are equally important. You should know how to place your codes according to the given query because you are stepping in the world of codes.

Differentiate Source Codes from Object Codes

Source codes are the codes that were addressed by the programmer. They are made up of the commands and other keywords that instruct the computer about what to do. However, computers do not understand source codes.

Consequently, source codes are assembled using a compiler. The resulting outputs become object codes, which are in a format that the computer processor understands.

What is a dynamic data structure?

A dynamic data structure produces a system for collecting data more efficiently into memory. When dynamic memory allocating works, it helps a program in accessing memory spaces as and when needed.

Can we use the “if” function for distinguishing strings?

The “if” command can only be utilized to examine numerical values as well as single character values. To distinguish string values, there is a different function called strcmp that deals especially with strings.

When do we prefer a “switch” statement over an “if” statement?

The switch statement is best practiced when working with selections based on an individual variable or expression. However, switch statements can only estimate integer as well as character data types.

How are Function prototypes declared in C Language?

A function in C language is declared as:

return_type function_name(formal parameter list)




Can a program be compiled without the main() function?

Yes, the compilation is possible, but the execution is not possible.

However, if you use #define, we can execute the program without the need for main().

For instance:

#include <stdio.h>

#define start main

void start() {



Write a loop statement that will show the following output:






This is a little complex process but you could start one by one so that you could execute the program easily.

for (a=1; a&lt;=5; i++) {

for (b=1; b&lt;=a; b++)




Write a simple code fragment that will check if a number is positive or negative.

The code

If (num&gt;=0)

printf(&quot;number is positive&quot;);


printf (&quot;number is negative&quot;);

Write down a simple code fragment that will swap the values of two variables num1 and num2.

The code is as follows:

int temp;

temp = num1;

num1 = num2;

num2 = temp;

How to display the ASCII value of the uppercase character ‘A’ using the concept of implicit type conversion?

The coding for the same is as follows.


int main()


char character = ‘A’;

int number = 0, value;

value = character + number;

printf(“The ASCII value of A is: %d\n”,value);

return 0;


Find the length of a string without using the inbuilt function strlen().

#include <stdio.h>

int main()


printf(“Welcome to DataFlair tutorials!\n\n”);

char String[50];

int count;

printf(“Enter a string: “);

scanf(“%s”, String);

for(count = 0; String[count] != ‘\0’; count++);

printf(“The length of string: %d\n”, count);

return 0;


Write a code snippet that changes a floating point number to an integer with the help of casting.

float f = 1.0;

int i1 = (int) f;

int i2 = * (int *) &f;

printf(“%d\n, i1);

printf(“%d\n, i2);

These questions are really significant and can be asked at an interview. While you are preparing for c interview questions programs, make sure you go through the above questions so that you could get a hint of how to tackle and deal with a query that is placed as a question in front of you.

No matter how good you are on the theoretical part, you can not just ignore the coding structure. Being a developer, you should have proper knowledge of syntax. As a result, the interviewer will judge you upon your practical skills along with the theoretical knowledge. In addition to that, you should revise your chapters daily so that you could prepare yourself in a better way and be in practice so that you do not face anxiety while answering the interviewer.

There are more scopes for C language in the future, so youngsters should go for it without any second thought. Mastering this language will open more opportunities for you and revising the c interview questions will enhance the chances of a company hiring you and giving you the opportunity to use your knowledge of C language efficiently. In other words, you should try to bring out the best in you in terms of placing the codings.

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