[GreenKeys] Selectric Printer

[Jones, Douglas W]

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).  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