30 C Programming Interview Questions and Answered for Fresher

Introduction

C programming is a fundamental skill for any aspiring software developer. Whether you are a fresh graduate or preparing for your first job interview, having a strong grasp of C programming concepts is crucial. In this blog, we will cover the top C programming interview questions that are commonly asked in interviews. These questions are designed to test your understanding of basic to advanced concepts in C programming. So, let’s dive in and start preparing for your C programming interview!

1. What is C programming?

C programming is a general-purpose, procedural programming language developed by Dennis Ritchie at Bell Labs in 1972. It is widely used for system programming and creating operating systems, compilers, and embedded systems.

2 Explain the basic structure of a C program.?

A basic C program consists of the following components:

Preprocessor directives
Global declarations
Main function
Function definitions

3. What are the different data types in C?

There are 5 basic data types in C::

- - int: cc
  - float: Stores a decimal number
  - double: Stores a decimal number with the highest precision
  - char: Stores a single character
  - void: Stores no value

4. The main differences between scanf() and gets() ?

The main difference between them is:

scanf() reads input until it encounters whitespace, newline or End Of File(EOF) whereas gets() reads input until it encounters newline or End Of File(EOF), gets() does not stop reading input when it encounters whitespace instead it takes whitespace as a string.
scanf can read multiple values of different data types whereas gets() will only get character string data.

5. What are the main uses of pointers in C programming?

The main difference between them is:

1. 1. To pass arguments by reference
  2. For accessing array elements
  3. To return multiple values
  4. Dynamic memory allocation
  5. To implement data structures
  6. To do system-level programming where memory addresses are useful

6. How are arrays defined and used in C?

An array is a collection of similar types of data items at a contiguous memory location. However, the size of the array is fixed, and you need to allot its size at the time of declaration.

Arrays are used to store a large set of similar data items in a contiguous memory blocks. Let us check the advantages of the array in c.

- - With the help of an array we can store a large amount of data in a contiguous memory location.
  - Random access to any elements is possible inside our array using their index.
  - We can easily traverse our array using any loops available.
  - As the elements are stored in a contiguous memory location, there are no overhead costs involved. Hence, they are memory efficient.

7. What is a function in C and how do you define one?

In C programming, a function is a reusable block of code that performs a specific task. It allows you to organize your code into manageable sections, making it easier to read, maintain, and debug.

To define a function in C, you need to specify the return type, the function name, and any parameters it takes. Here’s the basic syntax:

return_type function_name(parameter_list) {

// Function body

}

For example, to define a function that adds two integers and returns the result, you would write:

int add(int x, int y) {

return x + y;

}

In this example:

- - - - int is the return type, indicating that the function returns an integer.
      - add is the function name.
      - int x and int y are parameters, representing the integers to be added.

You can then call this function from your main function or any other part of your program like this:

int main() {

int result = add(10, 20);

printf(“The sum is %d\n”, result);

return 0;

}

This code will output: “The sum is 30”.

8. Explain the concept of recursion with an example.?

The idea is to represent a problem in terms of one or more smaller problems, and add one or more base conditions that stop the recursion. For example, we compute factorial n if we know the factorial of (n-1). The base case for factorial would be n = 0. We return 1 when n = 0.

9. What is dynamic memory allocation in C?

C Dynamic Memory Allocation can be defined as a procedure in which the size of a data structure (like Array) is changed during the runtime.

C provides some functions to achieve these tasks. There are 4 library functions provided by C defined under <stdlib.h> header file to facilitate dynamic memory allocation in C programming. They are:

malloc()
calloc()
free()
realloc()

10. Difference Between Direct and Indirect Recursion ?

Direct Recursion: In direct recursion, a function calls itself directly within its own body. This type of recursion is straightforward and easy to follow, as the function repeatedly calls itself until a base condition is met.

Indirect Recursion: In indirect recursion, a function calls another function, which in turn calls the original function. This involves at least two functions calling each other, creating a loop of function calls.

11. What are structures and unions in C?

The tag_identifier gives a name to the type. If you do not provide a tag name, you must put all variable definitions that refer to the type within the declaration of the type, as described in Structure and union type and variable definitions in a single statement. Similarly, you cannot use a type qualifier with a structure or union definition; type qualifiers placed in front of the struct or union keyword can only apply to variables that are declared within the type definition.

12. How do you handle errors in C programming?

C that can prevent errors or exceptions from abruptly terminating the program. However, a programmer can use other functions for error handling.

You can use errno for efficient error handling in C. Additionally other functions that can be used for error handling include perror, strerror, ferror, and clearererr

13. Write a program to reverse a string in C?

Reversing a string is the technique that reverses or changes the order of a given string so that the last character of the string becomes the first character of the string and so on. Furthermore, we can also check the Palindrome of the given string by reversing the original string.

For example, we enter a string “APPLE”, and then use the reverse algorithm. The reverse algorithm returns the string “ELPPA” which is completely reverse of the original string.

14. Write a program to find the factorial of a number using recursion?

Logic To Find The Factorial Of A Number Using Recursion:

Get the input from the user, by using the entered value the fact() is called,

The n-1 value is passed to fact() from the function,

Every time the function is called the n value is decremented by 1,

Once the value of n is 1, the recursive function will be stopped and send the value to the main() function.

15. What are reserved keywords and how many are there?

Words that are restricted for general use while writing a program, i.e., for use as a name for a variable, function, structure, etc., are called reserved keywords. Reserved keywords, also called reserved names, have special meanings, i.e., they are already defined for something.

The C programming language has the following 32 reserved keywords:

- - auto
  - break
  - case
  - char
  - const
  - continue
  - default
  - do
  - double
  - else
  - enum
  - extern
  - float
  - for
  - goto
  - if
  - int
  - long
  - register
  - short
  - signed
  - sizeof
  - static
  - struct
  - switch
  - typedef
  - union
  - unsigned
  - void
  - volatile
  - while

16. How are global variables different from static variables?

Global variables are variables with global scope, i.e., they are accessible throughout the program, unless shadowed. These variables are defined outside a function or code block.

Static variables are variables allocated statically, i.e., their value can’t be changed. It is fixed for the entire run of a program. They can be defined outside as well as inside functions. Moreover, they can be accessed from anywhere inside the program.

17. What are memory leaks? Why should it be addressed?

A memory leak happens when a memory created in a heap remains undeleted. This can lead to additional memory usage and, thus, affect the performance of a program. This is exactly why the issue of memory leaks must be addressed.

18. What is the role of a protected access specifier?

The privacy of a protected keyword lies somewhere between the keywords private and public. If a class is marked as protected, it can be accessed by its member functions, classes derived with public or protected access, privately derived classes, and friends of the class that declared these members.

19. What is the difference between prefix increment and postfix increment?

In prefix increment, the value of the variable is incremented before the program execution. The variable is incremented post the program execution in postfix increment.

++a <- Prefix increment

a++ <- Postfix increment

20. When is the register keyword used?

The register storage specifier, i.e., the register keyword, is used for storing a variable in the machine register. This is typically used for heavily-used variables to the likes of a loop control variable. The intent behind using the register keyword is to speed-up the program by minimizing variable access time.

21. What is recursion?

Recursion is the process when a function calls itself, directly or indirectly. Such a function is called a recursive function. There are two phases involved with a recursive function:

Winding phase: It starts when the recursive function calls itself and ends once the condition is reached.

Unwinding phase: Starts when the condition is reached, i.e., when the winding phase ends, and ends when the control returns to the original call.

22. How can we store a negative integer?

To store a negative integer, we need to follow the following steps. Calculate the two’s complement of the same positive integer.

Eg: 1011 (-5)

Step-1 − One’s complement of 5: 1010

Step-2 − Add 1 to above, giving 1011, which is -5

23. What is the auto keyword?

Auto is the default storage class of all the variables declared inside a code block or function. Local variables can also be referred to as automatic or auto variables. If no value is stored in an auto variable, then it gets a garbage value. Auto variables are called so because these variables allocate and deallocate memory upon entering and exiting the code block or function in which they are declared, respectively. Typically, there is no need to mention the auto keyword explicitly.

Example:

24. What is Preprocessor?

A Preprocessor Directive is considered as a built-in predefined function or macro that acts as a directive to the compiler and it gets executed before the actual C Program is executed.

In case you are facing any challenges with these C Programming Interview Questions, please write your problems in the comment section below.

25. What is the main difference between the Compiler and the Interpreter?

Compiler is used in C Language and it translates the complete code into the Machine Code in one shot. On the other hand, Interpreter is used in Java Programming Langauge and other high-end programming languages. It is designed to compile code in line by line fashion.

26. What do you mean by Dangling Pointer Variable in C Programming?

A Pointer in C Programming is used to point the memory location of an existing variable. In case if that particular variable is deleted and the Pointer is still pointing to the same memory location, then that particular pointer variable is called as a Dangling Pointer Variable.

27. What is segmentation fault in C?

A segmentation fault in c is a fault that happens when someone tries to access a forbiden memory location or makes use of a technique that is forbidden in the system on which they are working on.

28. What are the features of the C language?

Simplicity: Simple to understand and use.
Portability: Code can be executed on different machines with minimal modification.
Efficiency: Generates efficient and fast-executing programs.
Structured Programming: Supports functions and modular programming.
Rich Library: Comes with a rich set of built-in functions.
Memory Management: Allows dynamic memory allocation.
Extensibility: Functions can be defined and extended.
Low-Level Access: Provides low-level access to memory through pointers.

29. What is the usage of the pointer in C?

Pointers in C are a fundamental concept that allows you to store memory addresses of other variables. They are essentially special variables that hold memory locations rather than data values themselves. This ability to manipulate memory addresses directly gives programmers a powerful tool for various purposes, including:

Memory Management: Pointers enable you to allocate memory dynamically during program execution using functions like malloc and free. This is essential for creating data structures like linked lists, trees, and graphs, which require memory allocation to grow or shrink based on the program’s needs.
Function Arguments: Pointers can be passed as arguments to functions, allowing you to modify the original variable within the function’s scope. This is in contrast to passing by value, where a copy of the variable is passed, and changes made inside the function don’t affect the original variable.
Array Manipulation: Arrays in C essentially decay to pointers to the first element. This allows you to perform pointer arithmetic to access different elements of the array efficiently.
Low-Level Programming: Pointers grant fine-grained control over memory access, enabling interaction with hardware components or memory-mapped I/O.

Here’s an example to illustrate the concept:

30. What is a token?

The Token is an identifier. It can be constant, keyword, string literal, etc. A token is the smallest individual unit in a program. C has the following tokens:

Identifiers: Identifiers refer to the name of the variables.

Keywords: Keywords are the predefined words that are explained by the compiler.

Constants: Constants are the fixed values that cannot be changed during the execution of a program.

Operators: An operator is a symbol that performs the particular operation.

Special characters: All the characters except alphabets and digits are treated as special characters.

Conclusion

In this blog, we have covered a comprehensive list of essential C programming interview questions and answers that are commonly asked during interviews for freshers. Here’s a quick recap of the key points discussed

Understanding C Programming: We began with the basics of C programming, including its definition, basic structure, and various data types.
Functions and Arrays: We explored the concepts of functions and arrays, highlighting their definitions, usage, and importance in C programming.
Advanced Concepts: Topics such as recursion, dynamic memory allocation, structures, unions, and pointers were discussed to provide a deeper understanding of advanced C programming concepts.
Practical Applications: Examples of reversing a string, finding the factorial of a number, and error handling were provided to illustrate the practical applications of C programming.
Key Features and Memory Management: We delved into the features of C language, memory management, and the significance of handling memory leaks and segmentation faults.
Additional Important Topics: The blog also covered various topics like the auto keyword, preprocessor directives, compilers vs. interpreters, and tokens in C programming.

By going through these questions and answers, you have gained a solid foundation in C programming that will help you perform well in interviews. However, theory alone is not enough. It is crucial to practice coding regularly and implement these concepts in real-world scenarios to enhance your problem-solving skills and coding proficiency.

For more detailed insights and resources, visit Anubhav Programming Institute.

Encouragement: As you prepare for your C programming interviews, remember that consistent practice and a thorough understanding of the concepts are key to success. Try solving various coding challenges, participate in coding competitions, and work on projects to apply your knowledge. Good luck with your interview preparation, and may you succeed in landing your desired job!