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From: roy@phri.UUCP (Roy Smith)
Newsgroups: comp.unix.wizards
Subject: Re: Size of SysV "block" (really: byte != 8 bits)
Message-ID: <2792@phri.UUCP>
Date: Tue, 14-Jul-87 22:40:56 EDT
Article-I.D.: phri.2792
Posted: Tue Jul 14 22:40:56 1987
Date-Received: Fri, 17-Jul-87 01:44:34 EDT
References: <218@astra.necisa.oz> <142700010@tiger.UUCP>
Reply-To: roy@phri.UUCP (Roy Smith)
Organization: Public Health Research Inst. (NY, NY)
Lines: 25

In article <142700010@tiger.UUCP> rjd@tiger.UUCP writes:
> O.K., I'll byte.  (oops, pun initially unintended.)   A byte IS eight bits!!!
> Maybe you are thinking of a word??  And a nibble is four bits, and a gulp is
> sixteen bits (or was this a mouthful?), etc....

	No, no, no, a thousand times NO!  A byte is NOT NECESSARILY 8 bits!
Granted, on most of the popular machines you are likely to see today (Vax,
PDP-11, 680x0, 320xx, 80x86, Pyramid, etc, a byte is 8 bits, but that
doesn't mean it has to be.  A byte is simply some collection of contigious
bits taken as a unit.  Often a byte is that number of bits which most
comfortably holds a single character in the machine's native character
code, but not always.  Often the number of bits in a byte is dictated by
the underlying machine architecture, but that's not a hard and fast rule
either.  I could write a program on a Vax to read a file in 7-bit bytes if
I wanted to.  In fact, if I wanted to read DEC-10 tapes I would have to
write just such a program (and I once did).

	On a DEC-10/20, for example, a byte can reasonably be anything from
1 (0?) to 36 (35?) bits; 6, 7, and 9 bit bytes are all quite common and if
anything, I would say an 8-bit byte on a DEC-10/20 is a mite strange.  I'm
not sure byte even has a real meaning on a machine like a Cray.
-- 
Roy Smith, {allegra,cmcl2,philabs}!phri!roy
System Administrator, Public Health Research Institute
455 First Avenue, New York, NY 10016