From: Dan Harmon <harmon@tenet.edu>
Date: Sat, 13 Apr 1996 17:13:12 +0800
To: "Dr. Dimitri Vulis" <dlv@bwalk.dm.com>
Subject: Re: Answer about bits and bytes
In-Reply-To: <kTuamD31w165w@bwalk.dm.com>
Message-ID: <Pine.OSF.3.91.960413012249.6873A-100000@beall.tenet.edu>
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Just a note, Jim's attribution dates seem to be older than yours. Not 
that it matters a whole hill of beans.

Dan

P.S. DEC referred to memory size on the 11 series prior to the 11/70  in 
16 bit words, not 8 bit bytes. 

On Fri, 12 Apr 1996, Dr. Dimitri Vulis wrote:

> Jim Gillogly <jim@ACM.ORG> writes:
> > jim bell <jimbell@pacifier.com> writes:
> > >See, I do not challenge the fact that there were plenty of data objects of
> > >length other than 8-bits.  The issue is whether or not the people back then
> > >actually believed that a correct, official usage of the term "byte" included
> > >lengths other than 8.
> >
> > Reading from the PDP-10 Reference Handbook (DEC, 1971) page 2-30, we read:
> >
> > 	To conserve memory, it is useful to store data in less than full
> > 	36-bit words.  Bytes of any length, from 1 to 36 bits, may be
> > 	entered using a BYTE statement.
> >
> > 		BYTE (N) X,X,X
> ...
> 
> _The Programmer's Guide to the 1802_ (Tom Swan, Hayden Books, 1981) says the
> following on p. 19:
> 
>     The eight binary digits or bits represented in Fig. 2-1 are commonly
>     given the name _byte, and in this book, one byte will always equal
>     eight bits. (This is a rather common convention in microcomputing, but
>     a byte does not always equal eight bits in much of the published
>     literature.) Some books also refer to computer "words," but, since a
>     "word" is even more loosely defined than a "byte," we will refrain from
>     using it as a label for binary numbers. In addition, to make things
>     come out right for eight-bit computers, leading zeros are usually
>     written in front of binary numbers so all numbers come out to even
>     multiples of eight-bit bytes.
> 
> _Assembler Reference Manual for the Sub Workstation, Version 1.0 of
> 30th November 1982_ (we're talking the Motorola 68K Sun 1 here!) says:
> 
>     Many MC68000 machine instructions can operate upon byte (8-bit), word
>     (16-bit), or long word (32-bit) data.
> 
> They felt it necessary to specify this in a number of places.
> 
> A very important book that anyone who programs computers should read --
> Donald Knuth, _The Art of Computer Programming_ (Addison Wesley, 1973), v. 1,
> p. 120, says the following about the MIX language:
> 
>     Words. The basic unit of information is a _byte. Each byte contains an
>     _unspecified amount of information, but it must be capable of holding
>     at least 64 distinct values. That is, we know that any number between 0
>     and 63, inclusive, can be contained in one byte. Furthermore, each byte
>     contains _at _most 100 distinct values. On a binary computer a byte
>     must therefore be composed of six bits; on a decimal computer we have
>     two digits per byte.
> 
>     Programs written in the MIX language should be written so that no more
>     than sixty-four values are ever assumed for a byte. If we wish to treat
>     the number 80, we should always leave two adjacent bytes for expressing
>     it, even though one byte is sufficient on a decimal computer. _An
>     _algorithm _in _MIX _should _work _properly _regardless _of _how _big
>     _a _byte _is. Although it's quite possible to write programs which
>     depend on the byte size, this is an illegal act which will not be
>     tolerated; the only legitimate programs are those which would give
>     correct results with all byte sizes. It is usually not hard to abide by
>     these ground rule, and we will thereby find that programming a decimal
>     computer isn't so different from programming a binary one after all.
> 
>     ...
> 
>     _A _computer _word _is _five _bytes _plus _a _sign. The sign position
>     has only two possible values, + and -.
> 
> Give it up, Jim -- I have more ancient writings than you can shake a dynamite
> stick at. :-)
> 
> ---
> 
> Dr. Dimitri Vulis
> Brighton Beach Boardwalk BBS, Forest Hills, N.Y.: +1-718-261-2013, 14.4Kbps
>