Re: [USMA:38926] Re: Discussion on the metric systemHi Bill et al:
Sounds like you and I came from the same era (circa 1958) of punched cards.
I was on the US federal advisory committee for standardizing on the eight-bit
ASCII code. We selected the eight-bit ASCII code as the base even though IBM
wanted a BCD-based system.
At the time, the whole world used the five-bit baudot code in
communications and Digital Equipment Corporation computers used an extension of
it (ASCII) internal to their computers. It meant that the conversion would be
less stressful, less complex and more compatible by expanding the five-bit
baudot code to the eight-bit ASCII code for various reasons Including the
accommodation of international and special characters for both communications
and computers. Eight bits became a byte in computers now used today while six
bits were used to represent characters in early machines of IBM etc.
Regards, Stan Doore
----- Original Message -----
From: Bill Potts
To: U.S. Metric Association
Sent: Saturday, July 21, 2007 4:20 PM
Subject: [USMA:39118] Re: Discussion on the metric system (off topic -- of
course)
Stan:
Please excuse the delayed response. I only visit this list occasionally these
days.
Although this business of codes is obviously somewhat off-topic, it's
interesting, especially to those of us concerned with the niceties of the
metric system and therefore of the view (probably, but not necessarily) that
there's no such thing as an uninteresting number (or, apparently, code).
The interesting thing about EBCDIC is that, as with the old 6-bit BCD,
there's a direct correspondence between the encoding of any given character and
its representation, as punch holes, on the now-obsolete punch cards. Every one
of the 256 values has a corresponding set of punch holes. And, of course, as
the punch card came first, EBCDIC code points are based on that, rather than
the other way around.
Used to the maximum, the 12 rows of a punch card column could, of course,
accommodate 4096 unique values. IBM's "scientific" 7000 series computers used
row binary to take advantage of that, with the first 72 columns of one card
being able to store the contents of twenty-four 36-bit words.
However, although looking back is fun, I'm glad technology has moved on. I've
never missed those days of humping ten-thousand-card cartons of punch cards
around the computer room (or the card jams or the dropped cards).
Bill
----------------------------------------------------------------------------
From: G Stanley Doore [mailto:[EMAIL PROTECTED]
Sent: Wednesday, June 20, 2007 10:20
To: [EMAIL PROTECTED]; U.S. Metric Association
Subject: Re: [USMA:38932] Re: Discussion on the metric system
Thanks Bill for the correction and further explanation.
EBCDIC was invented to use the full 8 bits for expanded representations.
Stan Doore
----- Original Message -----
From: Bill Potts
To: U.S. Metric Association
Sent: Tuesday, June 19, 2007 4:33 PM
Subject: [USMA:38932] Re: Discussion on the metric system
Stan Doore wrote: "IBM invented the hexadecimal to provide for all types
of international characters and many special symbols."
Not quite. For that purpose, they invented and introduced EBCDIC
(Extended Binary Coded Decimal Interchange Code), for which the unit was/is the
byte, defined as a group of 8 bits. Because the three-bit grouping of the octal
notation was potentially awkward, they introduced four-bit [half byte]
hexadecimal notation, which already existed conceptually, but had no practical
application in the days of computers with 36-bit word sizes (e.g., the IBM
7090). Any EBCDIC value was thus expressible as 2 hexadecimal digits (as was,
eventually, any 8-bit ISO 646 [ASCII in the US] value).
Of course, it was still awkward, in that we all had to learn to use A
through F for the six four-bit groupings beyond the one expressed as 9.
Code points in today's 16-bit Unicode are, of course, expressible as
strings of four hexadecimal digits.
Bill Potts
(whose first experience with a computer was on the Burroughs E101 Desk
Size Engineering Computer, with its 256 10-digit decimal words on a drum,
plugboard programming, and a contemporary accounting-machine numerals-only
print mechanism).
