NetNews Usenet Archive 1992 #20/NN_1992_20.iso/spool/comp/std/c/2583

Internet Message Format | 1992-09-08 | 1.5 KB

Path: sparky!uunet!mcsun!uknet!acorn!ixi!clive
From: [e-mail] (Clive Feather)
Newsgroups: comp.std.c
Subject: Re: space optimization involving enum
Message-ID: <[e-mail]>
Date: 7 Sep 92 10:31:32 GMT
References: <[e-mail]> <[e-mail]> <[e-mail]>
Organization: IXI Limited, Cambridge, UK
Lines: 20

In article <[e-mail]> [e-mail] (Mark Brader) writes:
>>> ... The representation of [decimal] 10000 has to use the bit
>>> sequence 10011100010000.
>> As I read it, wrong.  Nothing I see prevents use of 2's complement,
>> 1's complement, or excess-2**(n-1) (the sign bit being reversed from
>> 2's complement).
> These systems are indeed all permissible.  But they also all use the
> bit sequence 10011100010000 in the representation of decimal 10000.

Both wrong. Excess-2**(n-1) is not a permitted system, because the
representation of decimal 10000 is not binary 10011100010000. The
standard requires that the representation of integers be a "pure-binary"
system, except for the sign bit, and that unsigned and signed integers
use the same representation for numbers where their ranges overlap.

--
Clive D.W. Feather     | IXI Limited         | If you lie to the compiler,
[e-mail]          | 62-74 Burleigh St.  | it will get its revenge.
Phone: [phone] | Cambridge   CB1 1OJ |   - Henry Spencer
Fax:   [phone] | United Kingdom      |