C program to find reverse of a number

Reversing the digits of a number is a fundamental problem in programming that helps in understanding basic arithmetic operations and loops. This article will guide you through writing a C program to reverse the digits of a given number, providing a detailed explanation and sample code.

Steps to Find the Reverse of a Number

To solve this problem, follow these steps:

1. Input the Number: Read the number from the user.
2. Extract Each Digit: Use a loop to extract each digit of the number.
3. Construct the Reverse: Build the reversed number by appending the extracted digits.
4. Print the Result: Output the reversed number to the console.

Write a C program to find reverse of a number

Here's a C program to reverse the digits of a number:

#include <stdio.h>

int main() {
    int number, digit, reverse = 0;

    // Input the number
    printf("Enter an integer: ");
    scanf("%d", &number);

    // Calculate the reverse of the number
    while (number != 0) {
        digit = number % 10;      // Extract the last digit
        reverse = reverse * 10 + digit;  // Append the digit to the reversed number
        number /= 10;             // Remove the last digit
    }

    // Print the result
    printf("Reversed number: %d", reverse);

    return 0;
}

Output

Enter an integer: 1234
Reversed number: 4321

Explanation

1. Input the Number: The program prompts the user to enter an integer. The scanf function reads the input number and stores it in the variable number.
2. Extract Each Digit:
   • The while loop continues as long as number is not equal to 0.
   • The last digit is extracted using the modulus operator (%). For example, if number is 1234, digit = 1234 % 10 will result in digit = 4.
3. Construct the Reverse:
   • The extracted digit is appended to the reverse variable by multiplying reverse by 10 and adding the digit. For the initial iteration, reverse = 0 * 10 + 4 results in reverse = 4.
   • The last digit is removed from number using integer division (/). For example, number = 1234 / 10 results in number = 123.
4. Repeat: The loop continues, extracting and appending each digit until number is 0.
5. Print the Result: The program prints the reversed number to the console using the printf function.

Detailed Steps

• Step 1: Input the Number
  • Use printf to prompt the user for input.
  • Use scanf to read the number from the user.
• Step 2: Extract Each Digit
  • Use a while loop to continue processing as long as number is not zero.
  • Use the modulus operator (%) to get the last digit of the number.
• Step 3: Construct the Reverse
  • Multiply the reverse variable by 10 and add the extracted digit.
  • Remove the last digit from the number using integer division (/).
• Step 4: Print the Result
  • Use printf to display the reversed number.

Example

For an input of 1234, the program will:

• Extract 4 and append it to reverse (reverse = 4).
• Extract 3 and append it to reverse (reverse = 43).
• Extract 2 and append it to reverse (reverse = 432).
• Extract 1 and append it to reverse (reverse = 4321).

The output will be Reversed number: 4321.