[GreenKeys] Selectric Printer

[Dave G4UGM]

> -----Original Message-----
> From: GreenKeys [mailto:greenkeys-bounces at mailman.qth.net] On Behalf
> Of Jones, Douglas W
> Sent: 24 November 2014 17:12
> To: Greenkeys GreenKeys
> Subject: Re: [GreenKeys] Selectric Printer
> 
> On Nov 23, 2014, at 10:16 PM, Clay Archer wrote:
> 
> > I worked for the Byte shop back in '76-'79 and one project we worked
> > on was interfacing a Selectric Typewriter to an Imsai 8080.  I wrote a
> > program to translate ASCII to the IBM Tilt & Rotate code and extra
> > control lines to control the typewriter with lots of software delay
> > loops for timing.
> 
> That's not a knife, this is a knife:
> 
> Back in the late 1970s, I worked on the PLATO IV system
> -- https://en.wikipedia.org/wiki/PLATO_(computer_system)
> 
> That system ran on a CDC mainframe that used a 6-bit character code (with
> 128 printing characters, thanks to shift codes).
> The code did not resemble ASCII in any way.
> 
> We had PLATO V intelligent terminals that had 8080 microprocessor in them,
> and we had access to an IBM Office System 6 ink-jet printer.  The question
> was, how to print PLATO files on that nice new printer.
> 
> The answer?  A communicating Mag Card Selectric, speaking IBM's Bisync
> synchronous data protocol and IBM's Word Processing EBCDIC (which was
> not entirely the same as EBCDIC). 

There used to be a document in IBM that described the differences between
the different character sets used in IBM as "Office Systems", mid range and
mainframes all used a slightly different  rang of characters. 
The only problem was that whilst it was viewable, it was virtually
un-printable. I seem to remember the tables in the end had descriptions of
the character that should appear , but wouldn't....


 I wrote the software on the PLATO IV
> mainframe and on the PLATO V terminal to move files to the Mag Card
> Selectric and store them on cards.  The Selectric only had 88 printable
> characters, so Word Processing EBCDIC only had 88 printable characters.
> Many of the extra characters we needed were available on the Symbol
> typeball, so our Mag Card Selectric output included stop codes to change
the
> typeball as needed to access the other characters.
> 
> The PLATO V terminal had a USART in it an an aux serial port, and while
> almost everyone ignored the S in USART, treating it as a UART, it could
handle
> synchronous data.
> 
> (How are typeballs relevant on an ink-jet printer?  Well, it was a virtual
> selectric.  You had to include stop codes in the data and include a
special
> "typeball selection card" in the deck of cards in order to escape from the
88
> character
> straightjacket.)
> 
> Then, we hand carried the mag cards from the Mag Card Selectric to the
> word-processing center where the ink jet printer was.
> That's how I printed my PhD thesis.
> 
> 		Doug Jones
> 		jones at cs.uiowa.edu
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