Convert a decimal number to hexadecimal in C without Modulus

In this Answer, we will convert a decimal number (numbers having the base 10) to hexadecimal numbers (numbers having the base 16) in C language.

For example, we have a decimal number 28, and we want to convert it to its hexadecimal equivalent, 1C; there are several approaches we can take in C language to do so, but we will be discussing two of them.

Approach 1: Through modulus division

This approach uses the modulus division operator to convert the decimal number to hexadecimal. We take the modulus with 16 and keep on storing it in a character array after either adding it with 48 or 55 for hexadecimal character conversion. This decision is based on whether or not the result of the modulus operation is greater than or equal to 10, as the hexadecimal numbers greater than 9, ranging from 10–15 are represented by A, B, C, D, E, and F, respectively. This continues until the decimal number's division by 16 reaches 0.

Code

Following is the code for this approach:

#include <stdio.h>
int main(){
  
  // taking the decimal number input
  int n;
  scanf("%d", &n);  
  // printing the decimal number
  printf("Decimal number: %d\n", n);
  // x is the index of hex_array[]
  // z stores the modulus value in each iteration
  int x = 1, z;
  char hex_array[100];
  // while the decimal number n is not equal to zero upon division
  while (n != 0){
    
    // storing the modulus with 16 in the variable z
    z = n % 16;
    // converting to hex equivalent based on the value of z
    if (z >= 10){
      z = z + 55;
    }
    else {
      z = z + 48;
    }
    // storing the hexadecimal equivalent in hex_array[]
    hex_array[x++] = z;
    // dividing the decimal number n by 16
    n = n / 16;
  }
  // printing hex_array[] in hexadecimal number format
  printf("The number in hexadecimal is: ");
  
  for (int y = x - 1; y > 0; y--){
    printf("%c", hex_array[y]);
  }
  
  return 0;
}

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Code input area

Explanation

In the code provided above, we perform the following steps:

Lines 5–10: We read and print the input value n, a decimal number provided by the user, to be converted.
Lines 14–15: We create a char array to store the hexadecimal equivalent of the decimal number where the variable x keeps track of the array's index in all iterations and z is an integer used to store the modulus value of n.
Lines 20–32: We take the modulus of the decimal number n with 16 and store it in the variable z.
- To convert the number to its hexadecimal equivalent, we add z with 55 if z >= 10 to convert into its char form since numbers greater than 9 in hexadecimal are represented by A, B, C, D, E and F.
- Otherwise, the number z is added with 48 to store the char equivalent of the range 0-9 in the array, hex_array[].
Line 35: We divide the number n by 16 to enter the next iteration of conversion to check whether or not it is greater than 0.
Lines 39–43: We print the char array hex_array[] to display the hexadecimal output.

Approach 2: Through format specifier

In this approach, we use the simple built-in format specifier in C for hexadecimal numbers. It is indicated by %X.Through

Code

Here is the code for this approach:

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