Top 31 C Programming Interview Questions and Programs

Top 31 C Programming Interview Questions and Programs

Top 30 C Programming Interview Questions: From Basics to Advanced

If you’re preparing for technical interviews, mastering C programming interview questions is a must. These questions cover a wide range of topics, from basic syntax to tricky advanced-level concepts, ensuring you’re well-prepared for your next opportunity.In this guide, we’ll explore 30 frequently asked C programming interview questions, with clear explanations and examples. Whether you’re a beginner or brushing up on advanced concepts, this resource will help you ace your interview.

Table of Contents

  1. Key Features of C Programming
  2. Compilation Process in C
  3. Use of Header Files
  4. Basic Data Types and Variables
  5. Static vs Dynamic Memory Allocation
  6. Pointers and Arrays
  7. C Interview Programs
  8. Practice Problems

Key Features of C Programming

  1. Platform-Dependent: Programs written in C can run only on the platform for which they are compiled.
  2. Modular Design: Large programs can be divided into smaller, manageable modules.
  3. System-Level Programming: C supports low-level programming for developing system software.
  4. Efficient Compilation and Execution: Compared to high-level languages, C offers faster performance.

Compilation Process in C

When you compile a C program, it undergoes multiple stages:
  1. Preprocessing: Handles macros and includes header files.
  2. Compilation: Translates the code into assembly language.
  3. Assembly: Converts assembly code into machine code.
  4. Linking: Combines multiple object files into a single executable.
 

Use of Header Files

Header files in C store definitions and rules for functions. For instance:
  • #include <stdio.h> is required for using printf() and scanf().
  • Including a header file multiple times can cause redundancy, but include guards (#ifndef) prevent this.
Example:
c
#ifndef HEADER_FILE #define HEADER_FILE // Code here #endif

Basic Data Types and Variables

C supports the following basic data types:
  • int: For integers.
  • float: For decimal numbers.
  • double: For high-precision decimals.
  • char: For single characters.
  • void: For functions with no return value.
Interview Tip: Be prepared for tricky questions, like storing values outside the range of an int by using long int or unsigned int.

Static vs Dynamic Memory Allocation

  1. Static Memory Allocation
    • Happens at compile-time.
    • Memory size is fixed.
    • Used for arrays.
  2. Dynamic Memory Allocation
    • Happens at runtime.
    • Memory size can be modified.
    • Used for linked lists via functions like malloc() and calloc().

Pointers and Arrays

Difference Between Arrays and Pointers

FeatureArraysPointers
DefinitionCollection of similar data types.Variable storing memory addresses.
InitializationAt definition.Cannot initialize directly.
SizeFixed.Dynamic.
Example: Pointer to Pointer
c
int main() { int a = 10; int *p = &a; // Pointer to int int **pp = &p; // Pointer to pointer printf("Value of a: %d\n", **pp); return 0; }
 

C Interview Programs

1. Print “Hello, World!” Without Using a Semicolon

c
#include <stdio.h> void main() { if (printf("Hello, World!")) {} }

2. Swap Two Numbers Without a Third Variable

c
#include <stdio.h> int main() { int a = 5, b = 10; a = a + b; // a becomes 15 b = a - b; // b becomes 5 a = a - b; // a becomes 10 printf("After Swap: a = %d, b = %d", a, b); return 0; }

Practice Problems

  1. Write a program to reverse a number.
  2. Print the Fibonacci series up to n.
  3. Check if a number is an Armstrong number.
  4. Print a pyramid pattern using stars:
markdown
* *** ***** *******
  1. Replace all 0s in an integer with 1.

Conclusion

Mastering these C programming interview questions is a significant step in cracking technical interviews. From basic concepts to advanced programming techniques, these questions will help you build confidence and perform well in your interviews.Click Here to know more our program! Top 31 C Programming Interview Questions and Programs