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C Programming Interview Questions (Simple Guide for 2024)

Updated On: May 29, 2024

C Programming Interview Questions

C programming remains one of the most foundational languages in computer science. Whether you’re an experienced developer or a newbie just starting, knowing your way around C can open up numerous opportunities. Are you prepping for a C programming interview? Don’t worry! We’ve collected a comprehensive list of questions and answers to help you ace your interview. Ready to dive in? Let’s get started!

Basic C Programming Interview Questions

What is C Programming?

C is a general-purpose, procedural programming language developed by Dennis Ritchie at Bell Labs in 1972. It has since become one of the most widely used languages, forming the foundation for many modern languages like C++, Java, and Python.

What are the key features of C?

  • Simplicity: C is a straightforward language with a small set of keywords.
  • Efficiency: Programs written in C are highly efficient and fast.
  • Portability: C programs can run on various machines with minimal or no modification.
  • Flexibility: C offers a range of data types and powerful operators.
  • Modularity: C allows the breaking down of a program into smaller functions.

What are the basic data types in C?

  • int: Integer type
  • float: Floating-point type
  • double: Double-precision floating-point type
  • char: Character type

What is a pointer in C?

A pointer is a variable that stores the memory address of another variable. It is a powerful feature in C that enables dynamic memory allocation, efficient array handling, and more.

int *ptr;
char *str;

What is the use of the ‘&’ and ‘*’ operators?

&: Address-of operator. It gives the memory address of a variable. *: Dereference operator. It gives the value stored at the address pointed by the pointer.

What are arrays in C?

Arrays are collections of elements of the same type stored in contiguous memory locations. They are used to store multiple values in a single variable.

How do you declare and initialize an array?

int arr[5]; // Declaration
int arr[5] = {1, 2, 3, 4, 5}; // Initialization

What is a function in C?

A function is a block of code that performs a specific task. Functions promote modularity and code reusability.

How do you declare a function?

return_type function_name(parameters);

What is the difference between call by value and call by reference?

  • Call by value: A copy of the actual parameter is passed to the function. Changes made to the parameter inside the function do not affect the actual parameter.
  • Call by reference: The actual parameter is passed to the function. Changes made to the parameter inside the function affect the actual parameter.

Intermediate C Programming Questions

What are storage classes in C?

Storage classes define the scope, visibility, and lifetime of variables or functions. They include:

  • auto: Default storage class for local variables.
  • register: Requests the variable to be stored in a CPU register.
  • static: Retains the value of a variable between function calls.
  • extern: Declares a variable defined in another file or scope.

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

  • malloc(): Allocates a single block of memory.
  • calloc(): Allocates multiple blocks of memory and initializes them to zero.

What is a structure in C?

A structure is a user-defined data type that allows the grouping of variables of different types under a single name.

How do you declare and initialize a structure?

struct Person {
    char name[50];
    int age;

struct Person person1 = {"John Doe", 30};

What is a union in C?

A union is similar to a structure but uses a single shared memory location for all its members. This means only one member can hold a value at any given time.

What is the difference between a structure and a union?

  • Structure: All members have their own memory locations.
  • Union: All members share the same memory location.

What are bitwise operators?

Bitwise operators perform operations on binary representations of integers. They include AND (&), OR (|), XOR (^), NOT (~), left shift (<<), and right shift (>>).

What is a preprocessor directive?

Preprocessor directives are instructions executed by the preprocessor before the actual compilation starts. Examples include #include, #define, and #if.

How do you use the #define directive?

The #define directive is used to define constant values or macros.

#define PI 3.14
#define SQUARE(x) (x * x)

Advanced C Programming Questions

What are dynamic memory allocation functions in C?

Dynamic memory allocation functions include malloc(), calloc(), realloc(), and free().

What is a linked list?

A linked list is a data structure where each element (node) contains a data part and a pointer to the next node.

How do you implement a linked list in C?

struct Node {
    int data;
    struct Node* next;

struct Node* head = NULL;

What is recursion?

Recursion is a programming technique where a function calls itself to solve smaller instances of the same problem.

What is a stack?

A stack is a linear data structure that follows the Last In, First Out (LIFO) principle. It supports operations like push, pop, and peek.

How do you implement a stack in C?

#define MAX 100

int stack[MAX];
int top = -1;

void push(int x) {
    if (top < MAX - 1) {
        stack[++top] = x;

int pop() {
    if (top >= 0) {
        return stack[top--];
    return -1; // Stack is empty

What is a queue?

A queue is a linear data structure that follows the First In, First Out (FIFO) principle. It supports operations like enqueue and dequeue.

How do you implement a queue in C?

#define MAX 100

int queue[MAX];
int front = -1;
int rear = -1;

void enqueue(int x) {
    if (rear < MAX - 1) {
        queue[++rear] = x;
        if (front == -1) {
            front = 0;

int dequeue() {
    if (front <= rear && front != -1) {
        return queue[front++];
    return -1; // Queue is empty

What is a binary tree?

A binary tree is a hierarchical data structure where each node has at most two children, referred to as the left child and the right child.

How do you implement a binary tree in C?

struct Node {
    int data;
    struct Node* left;
    struct Node* right;

struct Node* createNode(int data) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    newNode->data = data;
    newNode->left = NULL;
    newNode->right = NULL;
    return newNode;

What is a graph?

A graph is a data structure consisting of nodes (vertices) and edges (connections between nodes). Graphs can be directed or undirected.

How do you implement a graph in C?

#define MAX 100

int graph[MAX][MAX];

void addEdge(int u, int v) {
    graph[u][v] = 1;
    graph[v][u] = 1; // For undirected graph


Mastering these C programming questions will give you a significant edge in your next interview. Whether it’s understanding basic concepts or diving into advanced topics, being well-prepared will boost your confidence and impress your interviewer. Keep practicing, and good luck!


What is the best way to prepare for a C programming questions interview?

The best way to prepare is to practice coding regularly, review common interview questions, and understand the fundamental concepts deeply.

What are some common mistakes to avoid during a C programming questions interview?

Avoid common mistakes like syntax errors, not testing edge cases, and failing to explain your thought process clearly to the interviewer.

How important is it to understand pointers in C?

Understanding pointers is crucial in C as they are widely used for memory management, data structures, and function arguments.

Can you explain the difference between an array and a linked list?

An array is a collection of elements stored in contiguous memory locations, while a linked list is a collection of nodes where each node points to the next node, allowing for dynamic memory allocation.

What is the use of the static keyword in C?

The static keyword can be used to retain the value of a variable between function calls and to restrict the scope of a variable or function to the file

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