/* hex2.c  convert number to hexadecimal string
 * Author: Lin Jensen
 * Date:   2 February 2016 (Groundhog Day)
 * 
 * Example of using shift and bitwise logic instructions
 * 
 * This program divides 32 bits into 8 4-bit nibbles, then calls a function
 * to convert each nibble to a corresponding character 
 * it fills a string "backwards" to form the usual representation of a number
 * 
 * See also hex.a by John Waldron, which goes left to right
 * 	    hex1.a by Lin, which goes right to left, like this one
 * C operators	bitwise	logical
 * 	and	&	&&
 * 	or	|	||
 * 	not	~	!
 * 	xor	^	(none)
 * 	shift	<< (left), >> (right)

*/
#include	<stdio.h>

/* function to make (rightmost) 4 bits of a 32-bit integer
 * into an ascii character which represents it as a hexadecimal digit
 * example:   1011 becomes 'B' or 01000010
 * */
char  bin2hc( int number)
{  char hex;
   hex = number & 0xf;	// isolate rightmost 4 bits (nibble)
   hex = hex | 0x30;	// make into ascii code for a digit
   if (hex > '9')	// but if over '9' skip
      hex =hex + 7;	// the 7 chars between 9 and A
   return hex;
}

int main() {
    char digits[9] = "        ";	// fill with "hex" characters
    int num, count;
    printf("Type a number: ");
    scanf ("%d", &num);		// get user input as a number, typed in base 10
    count = 8;			// do loop for 8 nibbles
    while (count--)
    {	digits[count] = bin2hc(num);	// store character representation
	num = num >> 4;			// shift right 4 bits to move
    }					// all nibbles to the right
    printf ("In hex this is %s\n", digits);	// print resulting string
    return 0;
}