Example: Decimal to Hexadecimal Converter using Custom Function in C

// Decimal to Hexadecimal Converter using Custom Function
    #include <stdio.h> // For printf
    #include <string.h> // For string manipulation (optional for manual reverse)

    // Function to convert a decimal number to hexadecimal string
    // Stores the result in the provided char array 'hexResult'
    void decimalToHex(int decimalNum, char hexResult[]) {
        int i = 0;
        // Handle the case where the decimal number is 0 separately
        if (decimalNum == 0) {
            hexResult[i++] = '0';
            hexResult[i] = '\0';
            return;
        }

        while (decimalNum > 0) {
            int remainder = decimalNum % 16;
            if (remainder < 10) {
                // Convert 0-9 to ASCII '0'-'9'
                hexResult[i++] = remainder + '0';
            } else {
                // Convert 10-15 to ASCII 'A'-'F'
                hexResult[i++] = remainder + 'A' - 10;
            }
            decimalNum /= 16; // Divide by 16 for the next digit
        }
        hexResult[i] = '\0'; // Null-terminate the string

        // The hexadecimal digits are accumulated in reverse order
        // (least significant digit first), so we need to reverse the string.
        int start = 0;
        int end = i - 1;
        while (start < end) {
            char temp = hexResult[start];
            hexResult[start] = hexResult[end];
            hexResult[end] = temp;
            start++;
            end--;
        }
    }

    int main() {
        int decimal1 = 255;
        char hexResult1[100]; // Buffer to store the hexadecimal string
        decimalToHex(decimal1, hexResult1);
        printf("Decimal %d -> Hexadecimal %s\n", decimal1, hexResult1);

        int decimal2 = 10;
        char hexResult2[100];
        decimalToHex(decimal2, hexResult2);
        printf("Decimal %d -> Hexadecimal %s\n", decimal2, hexResult2);

        int decimal3 = 256;
        char hexResult3[100];
        decimalToHex(decimal3, hexResult3);
        printf("Decimal %d -> Hexadecimal %s\n", decimal3, hexResult3);

        int decimal4 = 0;
        char hexResult4[100];
        decimalToHex(decimal4, hexResult4);
        printf("Decimal %d -> Hexadecimal %s\n", decimal4, hexResult4);

        int decimal5 = 4096;
        char hexResult5[100];
        decimalToHex(decimal5, hexResult5);
        printf("Decimal %d -> Hexadecimal %s\n", decimal5, hexResult5);

        return 0;
    }