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10 C Programming Interview Questions and Answers

If you’re aiming for a cool tech job, it’s crucial to get ready for a C Programming job interview. If you’ve got an interview soon, this guide can make it super easy for you.

We’ve provided a list of 10  important questions on the C language that you might be asked in your interview.

We’ve also got the answers to help you reach your dream of becoming a software engineer or developer at your favourite IT/Tech company.

10 Important C Programming Questions and Answers

Q1. What do you mean by C language?

The interviewer is trying to assess your basic understanding of the language here. You need to articulate your answer well. A good answer would be that C is a procedural or structured programming language where large programs are systematically broken down into smaller modules that use structured code. An extremely useful language, C is largely a technique that minimises the chances of error and misinterpretation.

Q2. Explain the different features offered by the C programming language.

Make sure that you mention the most important features here including:

# C is a simple yet structured programming language with a rich set of operators and a fundamental flow control construction.

# It has 32 keywords only with several predefined functions.

# It is a highly portable programming language that permits mixed-mode operations as well as all data conversions.

#C features an extensive variety of data types such as structures, arrays, pointers, and unions.

# This is a language where a recursive function is possible.

Q3. Why is C programming known as the mother language?

It is known as the mother language since most of the JVMs and compilers are written in C programming. Furthermore, most of the other technical languages such as C++, JavaScript, Python, Rust, etc. borrow heavily from C language.

Q4. Explain the basic data types associated with C.

Here, you need to talk about the most important ones including Int – that represents a number (integer), Float – which represents a number with a fraction part, Double –that represents double-precision floating point value, Char – which represents a single character, and Void – that represent special purpose type without any value.

Q5. What do you mean by NULL pointer?

The NULL pointer does not refer to any address of value but NULL. In an ideal situation, if we assign a ‘0’ value to a pointer of any type, it becomes a Null pointer. In simpler words, explain that the Null is a special reserved value of a pointer in C.

Q6. Define a pointer in C language.

This is one of the common questions asked at C interview. You need to explain here that a pointer is a variable that refers to the address of a value to make the code optimised and perform faster.

E.g.: Data type *p; the syntax here tells that p is a pointer variable that holds the address number of a given data type value.

Q7. Explain the use of the function in C language.

Here, you’re required to explain the main ones such as C functions can be called any number of times from any place, they are used to avoid rewriting the same code again, and C function breaks bigger tasks into smaller tasks to make the language more understandable

Q8. Explain an array in C.

A good answer would be an array is a group of similar types of elements that have a contiguous memory location. Arrays are of 2 different types’ one-dimensional array and multidimensional array and it makes the code optimized as well as easy to sort.

Q9. What is recursion in C language?

The process when a function calls itself is known as recursion and the function that calls itself is known as a recursive function. The recursive function comes in two phases, namely the winding phase and the unwinding phase.

Q10. Explain structure in C language.

Here, you need to explain that the structure in C programming is a user-defined data type that allows storing multiple types of data in a single unit. It is also important to mention that the structure members can be accessed only through structure variables.

C Programming Intermediate Interview Questions

 1. Specify different types of decision control statements.

 2. What is an r-value and l-value?

 3. What is the difference between malloc() and calloc()?

 4. What is the difference between struct and union in C?

 5. What is called by reference in functions?

 6. What is a pass by reference in functions?

 7. What is a memory leak? How to avoid it?

 8. What is Dynamic memory allocation in C? Name the dynamic allocation functions.

 9. What is typedef?

 10. Why is it usually a bad idea to use gets()? Suggest a workaround.

 11. What is the difference between #include “…” and #include <…>?

 12. What are dangling pointers? How are dangling pointers different from memory leaks?

 13. What is the difference between ‘g’ and “g” in C?

 14. What is a near pointer and a far pointer in C?

 15. Which structure is used to link the program and the operating system?

 16. Suppose a global variable and a local variable have the same name. Is it possible to access a global variable from a block where local variables are defined?

 17. Which is better #define or enum?

C Programming Interview Questions For Experienced

 1. How can you remove duplicates in an array?

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

 3. Write a program to get the higher and lower nibble of a byte without using the shift operator.

 4. How do you override a defined macro?

 5. Write a C program to check if it is a palindrome number or not using a recursive method.

 6. C program to check if the given number format is in binary or not.

 7. C Program to find a sum of digits of a number using recursion.

 8. Can you tell me how to check whether a linked list is circular?

 Algorithm to find whether the given linked list is circular

 9. What is the use of a semicolon (;) at the end of every program statement?

 10. How to call a function before main()?

 11. Differentiate between the macros and the functions.

 12. Differentiate Source Codes from Object Codes

 13. What are header files and what are its uses in C programming?

 14. When is the “void” keyword used in a function

 15. What is dynamic data structure?

 16. Add Two Numbers Without Using the Addition Operator

 17. Subtract Two Number Without Using Subtraction Operator

 18. Multiply an Integer Number by 2 Without Using Multiplication Operator

 19. Check whether the number is EVEN or ODD, without using any arithmetic or relational operators

 20. Reverse the Linked List. Input: 1->2->3->4->5->NULL Output: 5->4->3->2->1->NULL

 21. Check for Balanced Parentheses using Stack

 22. Program to find nth Fibonacci number

 23. Write a program to find the node at which the intersection of two singly linked lists begins.

24. Merge Two sorted Linked List

Other important questions that you can expect at your c programming interview include:

a. Can you explain the concept of the dangling pointer in C?

b. What is the main difference between abs () and fabs () functions?

c. What is a header file and what is its usage in C programming?

d. Explain the difference between FOR and WHILE loop.

e. What is your explanation for the prototype function in C?

f. What is your understanding of stack in C?

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Advanced C Programming Interview Questions

Some of the advanced questions that you can be asked at the C language interview may include:

a. Explain the difference between ++x and x++.

b. Explain the meaning of sequential access file.

c. How do you explain the difference between static and dynamic library linking?

d. Explain the difference between the = symbol and == symbol?

e. What are the different data types associated with programming Language C?

f. Talk about the difference between call by reference and call by value in C language.

What to do When you get a Coding Question

Many candidates begin coding the moment they hear the question. That is usually a major mistake. First, take a moment to repeat the question back to the interviewer to ensure you understand it. If you misinterpret a question, the interviewer can clarify it.

Even if you believe the question is obvious, you should always ask for clarification. You might find that you missed something. It also communicates to the interviewer that you pay attention to detail.

Top IT businesses evaluate candidates based on four primary criteria: communication, problem-solving, technical competency, and testing. To demonstrate behaviours that meet these requirements, here are the best practices cheat sheet detailing what you should do before, during, and after coding interviews.

Consider asking the following questions.

  • How big is the size of the input?
  • How big is the range of values?
  • What kind of values are there? Are there negative numbers? Floating points? Will there be empty inputs?
  • Are there duplicates within the input?
  • What are some extreme cases of the input?
  • How is the input stored? If you are given a dictionary of words, is it a list of strings or a trie?

After you’ve properly specified the scope and goal of the challenge, explain your high-level strategy to the interviewer, even if it’s a naive one. If you’re stuck, brainstorm different ways and explain why they could or might not work. 

This is frequently the most challenging section of the interview. In general, look for repetitive tasks and try to optimise them by possibly caching the calculated results elsewhere. Instead of recalculating it, save it for later use.

Only begin coding until you and your interviewer have agreed on a strategy and you receive the green light.

Starting to code

When writing your code, use the proper style. Your goal is to help your interviewer understand your code so that they can quickly determine whether it accomplishes what it is supposed to and solves a particular problem.

Use simple variable names and avoid single-letter names, unless they are for iteration. However, if you’re coding on a whiteboard, avoid using long variable names. This decreases the amount of writing you’ll need to perform.

When copying and pasting code, assess whether it is necessary. It is sometimes true, but not always. If you find yourself copying and pasting a significant block of code across numerous lines, you can likely rearrange the code by isolating those lines into a function. If you only copied one line, it is mostly fine.

However, remember to change the respective variables in your copied line of code where relevant. Copying and pasting errors are a common source of bugs, even in day-to-day coding!

After coding

After you’ve completed coding, don’t tell the interviewer right away. In most circumstances, your code is not ideal. It may include flaws or syntax errors. What you should do is review your code.

First, go over your code from beginning to end. Consider it as if it were written by someone else and you were reading it for the first time, attempting to find flaws in it. This is exactly what your interviewer will be doing. Review and correct any problems you discover.

Next, create short test cases and run them through the code (not your algorithm) using the sample input.

Using this guide to accompany practice ensures that you cultivate good habits and muscle memory about interviews right from the beginning.

Remember that facing a technical interview is not only about showcasing your knowledge to the interviewer.

It is equally important to be comfortable and confident during the process. Taking care of small things like positive body language, speaking in an active voice, and managing the overall attitude during the interview can reflect your willingness to work and increase your chances of selection.

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