Interview Questions

Frequently Asked C Interview Questions Answers6 min read

January 6, 2020 4 min read
C interview questions


Frequently Asked C Interview Questions Answers6 min read

Read­ing Time: 4 min­utes

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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Gunjan Rawat is a literature graduate who shows keen interest in Java, SQL and Marketing as well.