On Fri, 25 Jul 2003 05:18:07 -0400, Vtrous <byte@fiber.cable> had a
scratch and wrote:
>In article <eeca89762d2dde854e135f38de891a20@rebleep>, soja@oblivion.net
>says...
>> Well, since it looks as if the dust has settled on the challenge,
>> I'll provide my answer before the original post expires on your
>> NNTP servers... The essential question regards the choice of byte
>> size: why was it (in practical terms) 12 bits early on and why did
>> it switch to 8 bits later?
>>
>> The first question is easier. The original size of the byte was
>> dictated by the permanent storage medium of the day. The use of 12
>> bit data fragments came from the IBM punch card, which was laid out
>> in 80 columns of 12 rows. Why that size? It was the result of the
>> Hollerith code, devised by Herman Hollerith (who also founded the
>> company that became IBM) for the representation of alphanumeric data
>> on punch cards, in an era when "computer" referred to people, not
>> machines. In the Hollerith code, 12 positions were needed to
>> represent the characters found on a typewriter keyboard. And, no,
>> that wasn't the only choice possible
>> (see http://www.fourmilab.ch/documents/univac/cards.html for an
>> alternative) but it came to dominate the market in a scenario eerily
>> similar to M$'s dominance of the software biz today. For those who
>> might ask why punch cards were used at all, the answer lies in part
>> in the 19th Century introduction of the Jacquard loom, which used
>> punched cards to automate the movement of the loom [see "The
>> Difference Engine" by Sterling and Gibson for a fictionalized description].
>>
>> So, in the 1960s we see a change in the popular size of the byte from
>> 12 bits to 6 bits. Why? The answer is two pronged (at the very
>> least), resulting from the (gradual) transition from punch cards to
>> magnetic and paper tapes as the dominant permanent storage media of
>> the day and the adoption of the ASCII code. Obviously, there's
>> nothing instrinsic to these other media that required the abandonment
>> of 12-bit bytes, but it stimulated a rethinking of the appropriate
>> size of a "byte" (though that term wasn't coined until later). So,
>> why 8 bits? Well, the folks developing the ASCII code found that
>> they needed to represent a minimum of 75 characters (upper/lower case,
>> numbers and the punctuation found on a typewriter keyboard), so that
>> meant 7 bits. So, why not a 7 bit byte? The answer to that is in part
>> again IBM. Just like M$ today, they were always trying to develop
>> their own de facto standard, so they came up with an alternate code,
>> EBCDIC, for the binary encoding of alphanumeric data. EBCDIC, in
>> contrast to ASCII, was an 8-bit code. So, when IBM introduced its new
>> 360 series computer, it used 8-bit bytes. As one of the dominant
>> computer manufacturers of its day, IBM was able to command a lot of
>> attention from the people making peripherals like tape drives,
>> so magtape was devised to be 8-track (there were also 7-track drives
>> made, but like Beta VCRs they are now dust). Other manufacturers soon
>> found a use for the extra bit, using it as a parity bit for error
>> checking, since magnetic media were subject to transcription errors.
>> That was the final straw, meaning that the de facto standard for
>> magtape and paper tape was 8-bit, leading to the universal adoption of
>> 8-bit bytes.
>
>I have a question: Who gives a shit?
>
More to the point - the author is too fucking stupid to actually know
that the definition of a byte is not 8 bits. They've mistaken a
convention of architecture for some sort of defined standard.
I challenge them to quote the relevant standard (it does exist, btw)
that defines byte size.
--
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