How to convert a decimal number to hexadecimal in C

A decimal is a term that describes the base- $10$ number system; for example, $(47)_{10}$

A hexadecimal is a term that describes the base- $16$ number system.

The digits used in hexadecimal are $0–9$ , followed by $A–F$ , where $A$ represents the decimal number $10$ , $B$ represents $11$ , and so on up to $F$ representing $15$ .

Decimal to hexadecimal conversion

Step 1: Start by entering the decimal number provided.

Step 2: Divide the decimal value by $16$ .

Step 3: Convert the remainder obtained in Step 2 to the equivalent hexadecimal digit. If the remaining is less than $10$ , the remainder should be used as the hexadecimal digit. Use the matching letter $A-F$ instead, where $A$ represents $10$ , $B$ represents $11$ , and so on.

Step 4: Add the hexadecimal digit received to the front of the result.

Step 5: Steps 2–4 must be repeated until the decimal number reaches zero.

Step 6: The hexadecimal representation of the original decimal number is obtained as a result.

Example: Convert the decimal number $1000_{10}$ into hexadecimal.

#include <stdio.h>
void decToHex(int decimal) 
{
    if (decimal == 0) 
    {
        printf("Hexadecimal: 0\n");
        return;
    }
    char hexadecimal[100];
    int indx = 0;
    while (decimal > 0) 
    {
        int remainder = decimal % 16;
        if (remainder < 10)
            hexadecimal[indx++] = remainder + '0';
        else
            hexadecimal[indx++] = remainder + 'A' - 10;
        decimal /= 16;
    }
    printf("Hexadecimal number is: ");
    for (int i = indx - 1; i >= 0; i--)
        printf("%c", hexadecimal[i]);
    printf("\n");
}
int main() 
{
    int decimalNum = 27;
    decToHex(decimalNum);
    return 0;
}

Code explanation

Lines 5–9: The if condition determines whether the input decimal is equal to zero. If it is, the hexadecimal representation is also zero, and the function outputs "Hexadecimal: 0" and returns.
Lines 18–21: The if-else condition determines whether the remainder is less than $10$ . If it is, the remainder is in the $0–9$ range, and the matching hexadecimal digit may be derived by adding the remainder to the ASCII value '0'. If the remainder is more than or equal to $10$ , the hexadecimal digits are $A–F$ . In this situation, the remainder is calculated by subtracting 10 and adding it to the ASCII value 'A'.
Lines 28–29: The for loop iterates through the hexadecimal array in reverse order, beginning at the highest index indx - 1 and ending at 0. The format specifier %c is used to print each hexadecimal digit.
Lines 34–39: The main function assigns the value 27 to the integer variable decimalNum. It then runs the decToHex method with the input decimalNum to convert it into hexadecimal.

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How to convert a decimal number to hexadecimal in C

Decimal to hexadecimal conversion

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