Example: Decimal to Hexadecimal using Manual Algorithm in C

// Decimal to Hexadecimal using Manual Algorithm
#include <stdio.h> // Required for printf and scanf

int main() {
    // Step 1: Declare variables
    long int decimalNum; // Use long int for potentially larger numbers
    int remainder;
    char hexChars[17] = "0123456789ABCDEF"; // Maps remainder to hex char
    char hexResult[100]; // Buffer to store the hexadecimal string (reversed initially)
    int i = 0; // Index for hexResult array
    int j;

    // Step 2: Prompt user for input
    printf("Enter a decimal number: ");
    scanf("%ld", &decimalNum);

    // Step 3: Handle the special case of decimal 0
    if (decimalNum == 0) {
        printf("Decimal 0 is Hexadecimal 0\n");
        return 0;
    }

    // Step 4: Convert decimal to hexadecimal using division and modulo
    // Loop until the decimal number becomes 0
    while (decimalNum > 0) {
        remainder = decimalNum % 16; // Get the remainder
        hexResult[i] = hexChars[remainder]; // Map remainder to hex character
        decimalNum = decimalNum / 16; // Divide the number by 16
        i++; // Move to the next position in the hexResult array
    }
    hexResult[i] = '\0'; // Null-terminate the string

    // Step 5: Print the hexadecimal result (in reverse order)
    printf("Hexadecimal equivalent is: ");
    for (j = i - 1; j >= 0; j--) {
        printf("%c", hexResult[j]);
    }
    printf("\n");

    return 0;
}