Popular C Programming Interview Questions & Answers

Welcome to our guide on C Programming Interview Questions!

C programming is a general-purpose, procedural programming language that provides low-level access to the system memory. Developed by Dennis Ritchie at Bell Labs in 1972, it has become one of the most widely used programming languages globally.

Hey there, tech enthusiasts and aspiring programmers! If you’ve ever dreamed of acing that crucial programming job interview or just want to brush up on your coding skills, you’re in the right place. Join us on this exciting journey into the world of C programming, where we’ll equip you with essential knowledge and insights to tackle challenging interviews and master the intricacies of this powerful language.”

 1. What is C programming language?

C is a general-purpose, procedural programming language developed by Dennis Ritchie in 1972 at Bell Labs. It is widely used for developing system software, application software, and embedded firmware.

2. What is an array in C?

An array is a collection of elements of the same data type, stored in contiguous memory locations and accessed using an index or a subscript.

3. What is the difference between printf() and scanf()?

printf() is used for output (printing to the console), whereas scanf() is used for input (reading from the console).

4. What is a pointer?

A pointer is a variable that stores the address of another variable in C programming.

5. Explain the concept of dereferencing a pointer.

Dereferencing a pointer means accessing the value stored at the memory address pointed to by the pointer variable.

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

Both functions are used for dynamic memory allocation. malloc() allocates uninitialized memory, while calloc() allocates initialized memory (sets all bits to zero).

7. What is the purpose of the sizeof operator in C?

The size of operator is used to determine the size (in bytes) of a data type or a variable.

8. What is the difference between ++i and i++?

Both ++i and i++ increment the variable i by 1. However, ++i is pre-increment (increments the value before using it in an expression) whereas i++ is post-increment (uses the current value in an expression and then increments it).

9. Explain the const keyword in C.

The const keyword is used to define constants. It specifies that the value of the variable cannot be changed after initialization.

10. What is the difference between =, ==, and ===?

In C, = is the assignment operator used to assign a value to a variable. == is the equality operator used to compare two values for equality. === is not a valid operator in C.

11. Explain the concept of recursion.

Recursion is the process in which a function calls itself directly or indirectly. It is often used for solving problems that can be broken down into smaller subproblems of the same type.

12. What is the difference between break and continue statements?

 The break statement is used to exit the loop prematurely, whereas the continue statement is used to skip the rest of the loop’s code and move to the next iteration.

13. What are the different types of loops in C?

There are three types of loops in C: for loop, while loop, and do-while loop.

14. Explain the switch statement.

The switch statement is used to make decisions based on the value of a variable. It evaluates the expression and matches the value with different case labels. If a match is found, the corresponding block of code is executed.

15. What is the purpose of the #include directive?

The #include directive is used to include the contents of a file in the source code. It is commonly used to include header files in C programs.

16. What is the difference between local and global variables?

Local variables are declared inside a function and are only accessible within that function, whereas global variables are declared outside of any function and can be accessed by any function in the program.

17. Explain the concept of a structure in C.

A structure is a user-defined data type that allows grouping variables of different data types under a single name. It is used to represent a record.

18. What is the purpose of the -> operator in C?

The -> operator is used to access members of a structure through a pointer to that structure.

19. What are the storage classes in C?

C supports four storage classes: auto, register, static, and extern, each with different scopes and lifetimes.

20. Explain the concept of file handling in C.

File handling in C involves operations such as opening, reading, writing, closing, and manipulating files. It is done using FILE pointers and functions like fopen(), fprintf(), fscanf(), fclose(), etc.

21. What is the purpose of the fgets() function?

The fgets() function is used to read a string from a file or the standard input (keyboard) along with newline characters.

22. Explain the concept of dynamic memory allocation in C.

Dynamic memory allocation allows a program to allocate memory at runtime using functions like malloc(), calloc(), and realloc(). It helps in managing memory efficiently.

23. What is the purpose of the typedef keyword?

The typedef keyword is used to create aliases for data types, making it easier to define complex data structures and improving code readability.

24. Explain the concept of bitwise operators in C.

Bitwise operators manipulate individual bits of a variable. The bitwise operators in C are & (AND), | (OR), ^ (XOR), ~ (NOT), << (left shift), and >> (right shift).

25. What is the difference between union and structure?

Both union and structure are used to group variables, but a structure allocates memory for all its variables, whereas a union allocates memory only for the largest variable in it. Thus, union saves memory by allowing the same memory location to be used for different variables at different times.

26. What is the purpose of the const pointer?

A const pointer is a pointer that points to a constant value, and it cannot be used to modify the value it points to.

27. Explain the concept of function pointers.

Function pointers are pointers that point to the address of functions. They can be used to call functions indirectly through the pointer variable.

28. What is the purpose of the assert() function in C?

The assert() function is used for debugging purposes. If the expression passed to assert() evaluates to false, the program terminates and an error message is displayed.

29. Explain the concept of recursion in C.

Recursion is a programming technique where a function calls itself directly or indirectly to solve a problem. It is particularly useful for tasks that can be broken down into smaller, similar subproblems.

30. What is the purpose of the volatile keyword in C?

The volatile keyword is used to indicate to the compiler that a variable’s value can be changed by external factors, such as an interrupt service routine. It prevents the compiler from optimizing away code that uses the variable.

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