Decimal to hexadecimal in C

In this post, you will learn how to convert decimal to hexadecimal using C programming language.

A decimal number is a base-10 number system where the range of numbers is 0,1,2,3,4,5,6,7,8,9. The main advantages of Decimal Number System are easy-to-read, used by humans and easy to manipulate. But there are some disadvantages, like wastage of space and time.

Hexadecimal describes a base-16 number system. Hexadecimal Number System is generally used in computer programming and Microprocessors. It is also helpful to describe colours on web pages. The main advantage of a Hexadecimal Number is that it is exceptionally compact and by utilizing a base of 16 means that the number of digits used to address a given number is normally less than in binary or decimal.

Convert decimal to hexadecimal in C using Loop

For converting a decimal to hexadecimal, the standard mathematical approach is to divide the number by 16 until it reduces to zero. The sequence of remainders from last to first in a hex structure is the hexadecimal number system of the given decimal number. The following example demonstrates this -

#include <stdio.h>
int main() {
    long int decimalnum, quotient;
    int a = 1 , b , num;
    char hexadecimal[ 100 ];
    printf("Please enter decimal number: ");
    scanf("%ld" , &decimalnum);
    quotient = decimalnum ;
    while( quotient != 0 ) {
        num = quotient % 16 ;
        if( num < 10 )
        num = num + 48 ;
        else
        num = num + 55 ;
        hexadecimal[a++]= num;
        quotient = quotient / 16;
    }
    printf("Decimal to hexadecimal: ");
    for(b = a -1 ; b > 0 ; b-- )
        printf( "%c" , hexadecimal[ b ] );
        return 0 ;
}

Please enter decimal number: 88
Decimal to hexadecimal: 58

Please enter decimal number: 66
Decimal to hexadecimal: 42

Convert decimal to hexadecimal in C using switch

In the given C program, we have used the switch statement to convert a decimal to hexadecimal number.

#include <stdio.h>
int main()
{
int decimalnum, temp, x;
char hex [32];
printf("Please enter the decimal number: ") ;
scanf("%d", &decimalnum) ;
temp = 0 ;
while(decimalnum > 0)
{
    switch(decimalnum % 16)
    {
        case 10 :
        hex [temp] = 'A' ; break;
        case 11 :
        hex [temp] = 'B'; break;
        case 12 :
        hex [temp] = 'C' ; break;
        case 13 :
        hex [temp] = 'D'; break;
        case 14 :
        hex [temp] = 'E' ; break;
        case 15 :
        hex [temp] = 'F'; break;
        default :
        hex [temp] = (decimalnum%16) + 0x30;
    }
decimalnum = decimalnum / 16;
temp++ ;
}
printf("Decimal to hexadecimal: ");
for( x = (temp-1) ; x >= 0 ; x--)
    printf("%c" , hex[x]);
    return 0;
}

Please enter the decimal number: 66
Decimal to hexadecimal: 42

Please enter the decimal number: 88
Decimal to hexadecimal: 58

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