C Program to Reverse a Number

This program takes an integer input from the user and reverses its digits using basic arithmetic operations.

Concept Overview

To reverse a number, we repeatedly extract its last digit using the modulus operator (%) and build the reversed number step by step by multiplying the current reversed number by 10 and adding the last digit.

Program

#include <stdio.h>

int main() {
    int num, reverse = 0, remainder;

    // Input number from user
    printf("Enter a number: ");
    scanf("%d", &num);

    // Reverse logic
    while (num != 0) {
        remainder = num % 10;
        reverse = reverse * 10 + remainder;
        num = num / 10;
    }

    // Display reversed number
    printf("Reversed number = %d\n", reverse);

    return 0;
}

Sample Output

Enter a number: 12345
Reversed number = 54321

Explanation

• The last digit of the number is obtained using `num % 10`.
• The reversed number is built as `reverse = reverse * 10 + remainder`.
• The original number is reduced each iteration using `num = num / 10`.
• The process repeats until the number becomes 0.