Basic C Interview Questions

These are few basic Interview questions in C .....

1)How do we check whether a linked list is circular?

2)What is the output of this program?

typedef union
int a;
char b[10];
float c;

Struct x,y = {100};
x.a = 50;
x.c = 21.50;

printf("Union x : %d %s %f \n",x.a,x.b,x.c );
printf("Union y : %d %s %f \n",y.a,y.b,y.c);

3)What is a Null object?

4)Name some pure object oriented languages.

5)What is a container class? What are the different types of container classes?

6)What will be the output of the following program:

7)What are the major differences between C and C++?

8)What is an incomplete type?

9)What are printf and scanf, call by reference or call by value?

10)What is a const pointer?

11)When should a type cast be used and when should it not be used?

12)Which is the easiest sorting method?

13)Which is the quickest sorting method?

14)Which are the best sorting algorithms to sort a linked list?

15)What is a preprocessor and what will it do for a program?

16)How can a string be converted into a number?

17)How can a number be converted into a string?

18)What is a heap?

19)Why does n++ execute much faster than n+1?

20)What is modular Programming?

21)Which expression always returns true and which expression always returns false?

22)What is the difference between "malloc" and "calloc"?

23)Is C
a)A low level language
b)A middle level language
c)A high level language ?

24)Why doesn't C support function overloading?

25)What is the difference between global int & static int declaration?

Click here for the solutions


  1. Hello. Could you please clear the 19th Question. The question asks difference between n++ and n+1, but the solution gives the explanation for n++ and ++n .

    But i hope the question really meant d/b n++ and ++n , coz i was asked the same question in an interview, n i gave this same answer.! fingers crossed.

    Thank you again.

    1. +n is faster than n++ is faster than n=n+1
      Machine usually have increment x as well as add const to x

      In case of n++, you will have 2 memory access only (read n, inc n, write n )
      In case of n=n+1, you will have 3 memory access (read n, read const, add n and const, write n)

  2. Thank you very much. Your blog is well presented and easy to navigate. But try to use blockquotes for codes to differentiate them from paragraphs.

    Content found here are quite different and educative.

  3. questios are very logical for basics
    answeers should b beside the questions

  4. 2nd question:
    how y.b value is d?

  5. give the answer for that questions

  6. please give ans to the ques

  7. C Interview Questions and Answers for campus placement preparation at

  8. amzing qestions...fully satisfied with answrs.....

  9. plz give me answer of these questions

  10. I enjoy this 25 questions on c interview questions, but I want some basic c interview questions along with answer like website

  11. here i can improve my knowledge about c...this is very useful questions..thank you for the author...can u send me more questions and puzzles?

  12. plz give me answer for those questions


  14. Hey, could you provide the answers to these question. Here is another site, with some interesting C interview questions along with their answers,

  15. its simply nice

    Frequently Asked C Language Interview Questions and answers

  16. This comment has been removed by the author.

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  18. Hi.frnds I want to learn C program easily ...please help me

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  21. Great work. Also check out the video on C Interview Questions. C Interview Questions - Video Guide

  22. Tks very much for your post.

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