[GreenKeys] More Teletypes with Mainframes

[Ed Sharpe]

Many thanks Jim!!!!

Wonderful history!!

Yes, we apreicate all of this!

Jim Haynes <jhhaynes at earthlink.net> wrote:

>On Tue, 16 Jul 2013, George B. Hutchison wrote:
>
>> Hmmmmmm.
>>
>> No one seems to remember the Model 29.
>>
>> It looked like a 28, smelled like a 28, had parts that were
>> interchangeable with a model 28,
>>
>> But was in fact a machine that responded to some variant of EBCDIC.
>>
>Seems like I keep getting moved into telling Long Stories, without
>knowing if anybody is all that interested.
>
>Model 29 started out in life, I'm told, as a 28-line replacement for
>the Model 20 up/low case six-level machine used on Teletypesetter
>circuits.  Trouble was, nobody wanted an up/low 28; they apparently had
>all the Model 20s they needed.
>
>Now in the computer biz at the time there were a bunch of six-level
>codes, generally called something BCD meaning binary-coded decimal
>meaning the decimal digits were represented by their binary
>equivalents.
>Each computer manufacturer had its own variant of BCD, and some like
>IBM
>had several different codes based on BCD.  These codes were more or
>less
>easy to translate into Hollerith punched card code.  A funny bug or 
>feature of Hollerith is that the alphabetical characters have breaks in
>the alphabet.  This will come up later.
>
>Western Electric and probably some of the Bell operating companies
>saw it would be useful to have Teletype equipment operating with BCD
>code for their computerized applications, so the Model 29 was recoded
>for BCD.  The most often seen variant was an ASR set called the IDP
>ASR set for Integrated Data Processing, one of the buzzwords of the
>period.  There would have been a large market for this kind of
>equipment
>in the business world, but AT&T didn't want to appear to be favoring
>IBM over the other computer companies, and didn't want to have to make
>a dozen variations of the set for all the different computer companies'
>BCD codes.  Univac had an odd one called excess-three.  The decimal
>digits
>instead of being represented by binary codes were represented by binary
>codes with three added.  This is convenient for doing decimal
>arithmetic.
>
>So the Model 29s, officially called the Model 28 IDP ASR sets, were 
>supposed to be for Bell System internal use only.  However it happened
>I know some escaped.  When I worked for G.E. in 1966 there was a man
>whose job was converting Model 29 typing units to Model 35.  Later
>there was a surplus store near the Oakland airport that had the remains
>of an RCA computer system and that included a bunch of Model 29 RO
>machines.  One of my friends bought a number of those, converted them
>to Model 35, and sold them to a dealer in that kind of stuff.
>
>The military was unhappy about all the varieties of BCD, and proposed
>a code called Fieldata that was to be the military standard.  Fieldata
>had its own set of problems, so there was the big effort that led to
>what
>we know as ASCII.  Much has been written about this so I won't go into
>it.  AT&T and the military backed ASCII, and most of the computer 
>companies decided they could live with it, but not IBM.  The sticking
>point was that ASCII had the whole alphabet in a contiguous set of
>codes, while IBM wanted to hold out for the code with breaks in the
>alphabet but easy to translate to Hollerith.  The end result was that
>IBM quit objecting to ASCII and just went off in its own direction with
>a new code called EBCDIC - Extended Binary Coded Decimal Interchange
>Code.  Which had breaks in the alphabet.  Presumably IBM thought their
>market power was such that they could bury ASCII; but they were up
>against
>AT&T and the federal government.
>
>I know Teletype built a limited number of ASR keyboards for Fieldata;
>presumably there were printers as well, and presumably they were also
>considered Model 29.  It doesn't really matter because the numbered
>models are a Bell System thing and Bell never offered the Fieldata
>machines to the public.
>
>I believe EBCDIC was announced in 1964 concurrently with the System/360
>announcement.  Some computer manufacturers felt they had to support
>EBCDIC or they couldn't compete against IBM.  IBM made some CRT
>terminals
>that used EBCDIC.  Their hard copy terminals were based on the
>Selectric
>typewriter and they had quite a zoo of codes for those.
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-- 
Sent from my Android phone with K-9 Mail. Please excuse my brevity.
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