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From: mcdonald@uxe.cso.uiuc.edu.UUCP
Newsgroups: comp.lang.c
Subject: Re: Printing binary (was: Re: Why colle
Message-ID: <47000021@uxe.cso.uiuc.edu>
Date: Tue, 27-Oct-87 12:23:00 EST
Article-I.D.: uxe.47000021
Posted: Tue Oct 27 12:23:00 1987
Date-Received: Sat, 31-Oct-87 01:45:17 EST
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Nf-From: uxe.cso.uiuc.edu!mcdonald    Oct 27 11:23:00 1987


********this is a repost*****
********the notes system bounced this with a message about "network
congestion"   has this happened to you?***********
>#include "stdio.h"

>void bprint(n, fp)
>/* print n in binary to given fp */
>int	n;
>FILE	*fp;
>{
>    static char *nybbles =
>
>    {
>	"0000", "0001", "0010", "0011",	"0100", "0101", "0110", "0111",
>	"1000", "1001", "1010", "1011",	"1100", "1101", "1110", "1111",
>    };
>    static char hexdigits = "0123456789abcdef";
>
>    char foobuf[BUFSIZ], *cp;	/* BUFSIZ from stdio.h */
>
>    (void) sprintf(cp = foobuf, "%x", n);
>    while (*cp)
>	(void) fputs(nybbles[strchr(hexdigits, *cp++) - hexdigits], fp);
>}

Arrgh gasp complicated!

perhaps (going to stdout, and for longs, but you get the idea):


#include <stdio.h>

bprint(number)
long number;
{
   unsigned long mask;
   for (mask = ~( (~(unsigned long)1l) >> 1); mask != 0 ; mask >>= 1)
       putchar((((unsigned long)number & mask) != 0l) + '0');
}

On paper this even works on 1's complements machines, although I haven't tried 
it except on 2's complement. Note that nowhere is the word size explicitly 
needed.

Doug McDonald