8bit hex number to binary number

8bithexbin.c

/* This code converts a 8bit hex number to a string representation of a binary number */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// variables to convert hex to binary in reverse order
int number;
int data[9] = {1,2,4,8,16,32,64,128,255}; // in the future (perhaps) use 2 ^ n - 1 , I need to allocate a buffer for this...
int count;
int dummy;
char *ptrb, *pb;

int main ( void )
{

       // read in a hex number here...
       printf("enter a hexidecimal number in the form XxXX\n");
       scanf("%X", &number);
       // this needs to have error checking

       dummy = number;

       ptrb = ( char * ) malloc(12 * sizeof(char));

       if ( ptrb == NULL)
        {
                printf( "Not enough memory to allocate buffer\n");
                return 1;
        }

        pb = ptrb;

        *pb++ = '0';
        *pb++ = 'b';

      // the count needs to be tied to the memory length ?
       for(count=7; count >= 0; count--) {

               if((data[count] - dummy) > 0 ) {
                   *pb++ = '0';
                  // add a line of code to push 0 to the string
               } else {
                  dummy = dummy - data[count];
                  *pb++ = '1';
                  // add a line of code to push 1 to the string
               }
       }

       *pb = '\0';

       printf("number in decimal is: %d\n",number);

       printf("the number in hex is: %x\n",number);

       printf("the number in binary is: %s\n",ptrb);

       return 0;

}