Re: questions about bits and bytes

At 12:00 AM 4/10/96 -0700, Bill Stewart wrote:
>At 09:33 PM 4/8/96 -0400, Jack Mott wrote:
>>This may be a bit of a no brainer, but everything I have read sorta 
>>skips over this point.  a bit is 1 or 0.  8 bits make up a byte (0-255).
>
>Be careful writing code - sometimes a byte is -128 to 127 instead of 0 to 255.
>Also, there are machines (mostly old kinky ones) that use bytes of sizes
>other than 8 bits.

No, Bill, a "byte" has ALWAYS been 8-bits.  One of the main reasons 
the term "byte" was invented was because the term "word" (as in, "word 
length") varied for different computers, especially in the 1960's. (In fact, 
many computers of that era used word lengths other than 8, 16, 32, 64 bits, 
as surprising as this may sound to the current crop of PC and Mac 
afficionados.)  This made it inconvenient to talk about memory capacities 
unless you were referring to the same machine.  The solution was to invent a 
new term, "byte," which conviently had about the same size as an ASCII 
character and was always 8 bits.

On Wed, 10 Apr 1996, jim bell wrote:

> >Be careful writing code - sometimes a byte is -128 to 127 instead of 0
> >to 255. Also, there are machines (mostly old kinky ones) that use
> >bytes of sizes other than 8 bits.
>
> No, Bill, a "byte" has ALWAYS been 8-bits.

Not that it really matters, but you're wrong; if you're talking about an
asynchronous data stream, a byte is however many bits it takes to express
one character. If you're using ASCII, it's 8; if you're using Baudot, it's
5. If you're talking about data in computers, then I think you're right, a
byte is always 8 bits.

-rich

No, bytes are no always 8 bits - some machines use(d) 9-bit bytes. That's 
why we have the word octet.



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Simon Spero writes:
> No, bytes are no always 8 bits - some machines use(d) 9-bit bytes. That's 
> why we have the word octet.

Indeed, machines have come in all flavors of byte size.

Byte size on PDP-6 descended machines, including the PDP-10 and
DECSystem-20, was always variable -- byte pointers could extract any
length from one bit to 36 bits, and byte size was an attribute of
files under several operating systems that ran on that series. I
remember that many of the MIT crowd favored 9 bit Extended ASCII,
using the so called space-cadet keyboards that set the two high bits
when control and meta were hit, and with the area we think of as the
control characters being taken up by other symbols.

"Byte" only came to mean "Eight Bits" consistantly in the last decade
or less. "Octet" is the only really consistant term.

Perry

jim bell <jimbell@pacifier.com> writes:
> >Be careful writing code - sometimes a byte is -128 to 127 instead of 0 to 25
> >Also, there are machines (mostly old kinky ones) that use bytes of sizes
> >other than 8 bits.
>
> No, Bill, a "byte" has ALWAYS been 8-bits.  One of the main reasons
> the term "byte" was invented was because the term "word" (as in, "word
> length") varied for different computers, especially in the 1960's. (In fact,
> many computers of that era used word lengths other than 8, 16, 32, 64 bits,
> as surprising as this may sound to the current crop of PC and Mac
> afficionados.)  This made it inconvenient to talk about memory capacities
> unless you were referring to the same machine.  The solution was to invent a
> new term, "byte," which conviently had about the same size as an ASCII
> character and was always 8 bits.

I used to hack a CDC Cyber box designed by Seymour Cray before he started his
oen company. It had the following curious features:

1 word = 10 _bytes_ = 60 bits
1 _byte_ = 6 bits

Out of respect for Jim, I dug up the dox, which say: "On the 6600, the basic bit
groupings are 6, 12, 15 and 30 bits". The dox consistently refer to the 6-bit
chunks as "characters", never bytes. However I've heard people refer to 6 bits
as bytes and to 3 bits (an octal digit) as nybbles.

Naturally, the character set had only 64 symbols - no lowercase letters.

Both integers and reals were 60 bits.

Addresses in the instructions were 15 bits, but that was an address of a
60-bit word.

Negative numbers were represented with one's compliment (i.e. -X = NOT X).
Hence there were two zeroes: positive and negative.


I believe BESM-6 also had 6-bit bytes. I have the dox for it someplace
(in Russian) but can't find them offhand.

Moral: it's not necessarily redundant to say '8-bit byte'.

---

Dr. Dimitri Vulis
Brighton Beach Boardwalk BBS, Forest Hills, N.Y.: +1-718-261-2013, 14.4Kbps

Dr. Dimitri Vulis writes:
>I used to hack a CDC Cyber box designed by Seymour Cray before he started his
>oen company. It had the following curious features:
>
>1 word = 10 _bytes_ = 60 bits
>1 _byte_ = 6 bits

. . .

>I believe BESM-6 also had 6-bit bytes. I have the dox for it someplace
>(in Russian) but can't find them offhand.
>
>Moral: it's not necessarily redundant to say '8-bit byte'.

Which is precisely the reason the IETF always refers to "bytes" as
"octets".  "Octet" is defined to be eight bits, regardless of local
word sizes.

jim bell writes:

: >At 09:33 PM 4/8/96 -0400, Jack Mott wrote:
: . . . .
: >Also, there are machines (mostly old kinky ones) that use bytes of sizes
: >other than 8 bits.
: 
: No, Bill, a "byte" has ALWAYS been 8-bits.  One of the main reasons 
: the term "byte" was invented was because the term "word" (as in, "word 
: length") varied for different computers, especially in the 1960's. (In fact, 
: many computers of that era used word lengths other than 8, 16, 32, 64 bits, 
: as surprising as this may sound to the current crop of PC and Mac 
: afficionados.)  This made it inconvenient to talk about memory capacities 
: unless you were referring to the same machine.  The solution was to invent a 
: new term, "byte," which conviently had about the same size as an ASCII 
: character and was always 8 bits.

One trouble with this statement was that an ASCII character only has 7
bits.  Another is that when I snuck into the IBM Executive Computer
Concepts Course in the mid-sixties, we [a bunch of high-powered
executives and me] were told, as I recall, that originally the term byte
was used by some to represent 7 bits.  IBM took credit for standardizing
the term on 8 bits.

--
Peter D. Junger--Case Western Reserve University Law School--Cleveland, OH
Internet:  junger@pdj2-ra.f-remote.cwru.edu    junger@samsara.law.cwru.edu