Embedded Prep

Reverse a Hex Number in C : If you are learning C programming, working with hexadecimal numbers is an important skill. One common task is to reverse a hex number – that means flipping its digits from last to first.Master the art of reversing a hexadecimal number with this beginner-friendly guide covering C++, Python, and Java. Learn what hex numbers are, how reversal works, and explore simple, step-by-step programs for each language. Perfect for students and programmers looking to practice string manipulation, number system basics, and improve problem-solving skills with real coding examples.
In this tutorial, we will explain what a hex number is, how reversing works, and how to write C code to reverse a hexadecimal number step-by-step.

What is a Hex Number?

A hexadecimal number (or hex number) is a number system with base 16.
It uses digits 0-9 and letters A-F:

Hex: 0, 1, 2, ..., 9, A, B, C, D, E, F
Decimal: 0, 1, 2, ..., 9, 10, 11, 12, 13, 14, 15

Example:

• Hex 1A3F in decimal is 6719.

What Does “Reverse a Hex Number” Mean?

Reversing a hex number means reading its hexadecimal digits from right to left.

Example:

Original: 1A3F  
Reversed: F3A1

Steps to Reverse a Hex Number in C

We can reverse a hex number by:

1. Reading the number as a string (so letters and numbers are preserved).
2. Reversing the string by swapping characters.
3. Printing the reversed hex number.

1.C Program to Reverse a Hex Number

#include <stdio.h>
#include <string.h>

int main() {
    char hex[100]; // To store hex number as string
    int length, i;
    char temp;

    // Step 1: Input hex number
    printf("Enter a hexadecimal number: ");
    scanf("%s", hex);

    // Step 2: Find length
    length = strlen(hex);

    // Step 3: Reverse the string
    for (i = 0; i < length / 2; i++) {
        temp = hex[i];
        hex[i] = hex[length - i - 1];
        hex[length - i - 1] = temp;
    }

    // Step 4: Output the reversed hex number
    printf("Reversed hexadecimal number: %s\n", hex);

    return 0;
}

Example Output

Enter a hexadecimal number: 1A3F
Reversed hexadecimal number: F3A1

How Reverse a Hex Number Code Works

• We store the hex number as a string to preserve both numbers and letters.
• strlen() helps us find how many characters are in the input.
• A loop swaps characters from start and end until the middle is reached.
• Finally, we print the reversed result.

Key Points of Reverse a Hex Number

• Use char[] to store hex numbers with letters.
• Always handle input as a string, not as an integer, when reversing.
• Works for both uppercase (A-F) and lowercase (a-f) hex letters.

2. Reverse a Hex Number in C++

#include <iostream>
#include <string>
#include <algorithm>
using namespace std;

int main() {
    string hexNum;

    // Step 1: Input hex number
    cout << "Enter a hexadecimal number: ";
    cin >> hexNum;

    // Step 2: Reverse the string
    reverse(hexNum.begin(), hexNum.end());

    // Step 3: Output reversed hex
    cout << "Reversed hexadecimal number: " << hexNum << endl;

    return 0;
}

Explanation:

• We use string to store the hex value.
• The reverse() function from <algorithm> quickly reverses the characters.
• Works for both uppercase and lowercase letters.

3. Reverse a Hex Number in Python

# Step 1: Input hex number
hex_num = input("Enter a hexadecimal number: ")

# Step 2: Reverse the string using slicing
reversed_hex = hex_num[::-1]

# Step 3: Output result
print("Reversed hexadecimal number:", reversed_hex)

Explanation:

• Python treats strings as sequences, so slicing [::-1] reverses the string easily.
• This method is the shortest and beginner-friendly.

4. Reverse a Hex Number in Java

import java.util.Scanner;

public class ReverseHex {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        // Step 1: Input hex number
        System.out.print("Enter a hexadecimal number: ");
        String hexNum = sc.next();

        // Step 2: Reverse using StringBuilder
        String reversedHex = new StringBuilder(hexNum).reverse().toString();

        // Step 3: Output result
        System.out.println("Reversed hexadecimal number: " + reversedHex);

        sc.close();
    }
}

Explanation:

• Java’s StringBuilder class has a built-in reverse() method.
• Using toString() converts the reversed object back into a string.

Example Run for Reverse a Hex Number in all Languages

Enter a hexadecimal number: 1A3F
Reversed hexadecimal number: F3A1

Key Takeaways

• Always store hex numbers as strings when reversing.
• C++ uses reverse() from <algorithm>.
• Python uses slicing [::-1].
• Java uses StringBuilder.reverse().

FAQ : Reverse a Hex Number in C

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