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From: Keith Thompson <kst-u@mib.org>
Newsgroups: sci.math,comp.lang.c,comp.lang.fortran,comp.lang.pl1,comp.lang.ada
Subject: Re: KISS4691, a potentially top-ranked RNG.
Date: Fri, 29 Apr 2011 08:13:23 -0700
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Date: 2011-04-29T08:13:23-07:00
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glen herrmannsfeldt <gah@ugcs.caltech.edu> writes:
> In comp.lang.fortran David Bernier <david250@videotron.ca> wrote:
[...]
>> AFAIK, sizeof(unsigned long) can be relied upon to give the size
>> in 8-bit bytes of a C "unsigned long".
>
> No.  You need CHAR_BIT to tell how many bits are in a char.
> It has been known to get to 64 on word addressed 64 bit machines.
> It must be at least 8, but can be more.

Certainly CHAR_BIT *could* be 64 (or even more), but I've never heard
of a 64-bit system with CHAR_BIT==64.  Such an implementation would
have trouble dealing with octet-oriented data from other systems.
Some DSPs (digital signal processors) do have CHAR_BIT > 8.
There have been systems with, for example, 9-bit bytes, but they
had pretty much become obsolete by the time C was standardized.

C defines two kinds of implementations, hosted and freestanding.
Hosted implementations must support the full standard library
(stdio and so forth); freestanding implementations are typically for
systems where the program doesn't run under an operating system,
such as embedded systems and OS kernels.  I've never heard of a
hosted implementation with CHAR_BIT > 8.

Do you know of such a system?

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Nokia
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"