questions about bits and bytes

[Dr. Dimitri Vulis]

jim bell <jimbell at 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'.

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