The impact of C programming is visible in every corner of the modern tech world. Numerous applications, including Microsoft Windows, run on C. Python, a highly popular language, owes its foundation to C. While modern applications showcase features developed in high-level languages, it’s the underlying strength of C that supports their core functionalities.
Due to its important role in system-level programming, performance optimisation, and embedded systems development, C programming continues to be highly relevant today
In India, the demand for skilled C programmers remains high. One major reason is that most leading global software companies have their backend operations set up in India and they still actively require professionals well-versed in C.
Overall, while the competition is high, the Indian job market offers many opportunities for skilled and passionate C programmers who can demonstrate their expertise.
The main factor for getting selected would be to ace the technical round and make a solid impression at the technical level.
So, to help you prepare for your next job interview, let’s explore some commonly asked C programming questions (along with their answers) that are asked at interviews and technical rounds.
What do Interviewers Focus During C Programmers Interview?
But before we get to the actual questions, it is important to understand another important part of these interviews.
When recruiters ask questions about C programming, they want to know how much you know and understand about the C programming language. Here are some things they might ask about:
1. Syntax and language basics
Recruiters might ask you about the basic rules of C programming, like how to declare variables, use loops and conditionals, define functions, and work with different types of data.
2. Memory management
In C, you manually handle memory. Interviewers might ask you about allocating and freeing memory dynamically, avoiding memory leaks, and using pointers effectively.
3. Algorithmic thinking
C is often used for tasks that require efficient performance. You may be asked about designing algorithms, using data structures effectively, and optimising code for better performance.
4. Error handling and debugging
C involves dealing with low-level details and finding and fixing errors. You could be asked questions on how to handle errors, debugging techniques, and your familiarity with debugging tools.
5. Standard libraries and APIs
C has a set of libraries and functions that are commonly used. Recruiters might ask you about these libraries and how you use them in your code.
6. Coding style
C has its own style conventions and best practices. Interviewers sometimes ask about things like how to name variables, organise your code, and make it readable and maintainable.
7. Real-world experience
Recruiters might ask you about your past experiences working on C projects, both in school and at work. They might want to know about the complexity of the projects, your role in them, and any challenges you faced.
Remember that the specific questions asked can vary depending on the job level, company requirements, and role responsibilities. It’s important to be well-prepared and have a good understanding of C programming and related concepts before your interviews.
Basic C Programming Interview Questions
Here are some basic C programming interview questions along with their answers:
1. What is the difference between printf() and scanf() functions?
printf() is used to print formatted output to the console, while scanf() is used to read formatted input from the user.
2. What is the difference between while and do-while loops?
The while loop checks the condition at the beginning and executes the loop body only if the condition is true. The do-while loop executes the loop body first and then checks the condition. It ensures that the loop body executes at least once.
3. Explain the concept of conditional statements in C.
Conditional statements allow you to control the flow of a program based on certain conditions. In C, the if-else statement is used to execute a block of code if a condition is true, and the switch statement is used to select one of many code blocks to be executed.
4. What is the difference between = and == operators in C?
The = operator is the assignment operator used to assign a value to a variable. The == operator is the equality operator used to compare two values for equality.
5. How do you swap the values of two variables without using a temporary variable?
You can swap the values of two variables without a temporary variable using the XOR bitwise operator. Here’s an example:
int a = 5, b = 10;
a = a ^ b;
b = a ^ b;
a = a ^ b;
6. What are the different storage classes in C?
C provides four storage classes: auto, static, extern, and register.
Auto is the default storage class for local variables and is automatically allocated and deallocated.
Static variables have a lifetime throughout the program execution and retain their values between function calls.
Extern is used to declare variables that are defined in other files.
Register suggests that a variable should be stored in a register for faster access.
7. What is the purpose of the break statement in C?
The break statement is used to terminate the execution of a loop or switch statement. It is typically used to exit a loop prematurely when a certain condition is met.
8. Explain the concept of recursion in C.
Recursion is a technique where a function calls itself directly or indirectly. It allows solving complex problems by breaking them down into smaller, simpler instances. Recursion requires a base case to terminate the recursive calls.
9. How can you find the length of a string in C?
The length of a string can be determined using the strlen() function from the standard library. It returns the number of characters in a string, excluding the null character.
10. What is a constant in C?
A constant is an identifier whose value cannot be changed during the program execution. In C, constants are defined using the const keyword and provide a way to make program logic more readable and maintainable.
Common C Programming Technical Questions
Here are some commonly asked C programming technical questions along with their answers:
1. What is the difference between malloc() and calloc() functions?
malloc() is used to allocate a single block of memory of the specified size, while calloc() is used to allocate multiple blocks of memory initialised to zero.
2. Explain the concept of pointers in C.
Pointers are variables that store memory addresses. They allow indirect access to data in memory. Pointers are used for dynamic memory allocation, passing arguments by reference, and creating complex data structures.
3. What is the difference between an array and a pointer in C?
An array is a collection of elements of the same data type stored in contiguous memory locations. A pointer, on the other hand, is a variable that stores the memory address of another variable. An array name can be used as a pointer to the first element of the array.
4. What is the difference between ++i and i++?
++i is the pre-increment operator, which increments the value of i and returns the incremented value. i++ is the post-increment operator, which increments the value of i but returns the original value before incrementing.
5. What is the const keyword in C?
The const keyword is used to declare variables as constants, meaning their values cannot be changed once assigned. It is a good practice to use const to indicate that a variable should not be modified.
6. Explain the difference between strcpy() and strncpy() functions.
strcpy() is used to copy a string from one memory location to another until it encounters a null character. strncpy() is used to copy a specified number of characters from one memory location to another, even if a null character is not present.
7. What is the purpose of the volatile keyword in C?
The volatile keyword is used to indicate that a variable can be modified by external entities that are not part of the program. It tells the compiler not to optimise or cache the variable, ensuring that any changes made to it are always reflected.
8. What are function pointers in C?
Function pointers are pointers that store the memory addresses of functions. They allow functions to be passed as arguments to other functions or stored in data structures. Function pointers are often used for implementing callback mechanisms and dynamic dispatch.
9. What is the role of the sizeof() operator in C?
The sizeof() operator is used to determine the size, in bytes, of a variable or a data type. It is commonly used when allocating memory dynamically, calculating array sizes, or iterating over data structures.
10. How is memory allocated/deallocated in C?
Memory can be dynamically allocated using the malloc(), calloc(), or realloc() functions. Once the allocated memory is no longer needed, it should be deallocated using the free() function to release the memory back to the system.
In conclusion, C programming continues to be a crucial component in the tech world. In India, the demand for skilled C programmers continues to remain high. Interviews about C programming are designed to gauge your technical knowledge, adaptability, and real-world experience to recruiters.
Basic and technical interview questions cover key concepts such as functions, loops, conditional statements, pointers, memory allocation, and string manipulation. By thoroughly preparing for these interviews, individuals can position themselves as standout candidates in the competitive job market.
FAQs on C Programming Interview Questions
Q1. What is C language?
Ans: C language is a high-level programming language originally developed for writing system software. It is widely used for its simplicity, efficiency, and portability, making it a popular choice for various applications.
Q2. What are the features of the C language?
Ans: C language features simplicity, efficiency, portability, and support for modular programming, making it widely used and suitable for various applications.
Q3. When was C language developed?
Ans: C language was developed in the early 1970s. It was initially designed by Dennis Ritchie at Bell Laboratories between 1969 and 1973.
Q4. Why is C called a mid-level programming language?
Ans: C is called a mid-level programming language because it combines elements of both low-level and high-level languages.
It offers control over hardware resources like low-level languages, while providing higher-level abstractions for easier programming like high-level languages. This balance makes it suitable for system-level programming and close-to-hardware operations.
Q5. What is the difference between C and C++?
Ans: C is a procedural programming language, while C++ is an extension of C that introduces object-oriented programming features.
