[GreenKeys] [External] Re: Two wire recorders available... anyone interested?

[Jones, Douglas W]

From: Nick England [navy.radio at gmail.com] -- Friday, August 19, 2022 5:01 AM

> Memories. Back in the late 1960s, our college newspaper had one of those IBM mag tape composer systems.

That was the predecessor of the IBM Mag-Card Selectric, a machine I remember well but not fondly.  I wrote a bit about my experience interfacing with this monster at the end of this:
-- https://homepage.cs.uiowa.edu/~jones/plato/#printing

The problem?  These machines didn't use a standard character set, they stored text in terms of tilt and rotate codes for Selectric typeballs.  The ball had 4 rows of 22 characters, giving 88 printable characters.  The coding was 2 bits for row select, and 5 bits for how to rotate the ball before hammering the paper.  They may well have used an 8th bit to distinguish between control codes and printing codes.  If I recall correctly, the printing characters on the typeball were arranged exactly like the 4 rows of the keyboard, in QUERTY order.

And then, they added a communications option to the @#$%^& thing to make it speak what they called IBM Word Processing EBCDIC.  That used EBCDIC coding for printing characters and control codes, except that you had to constantly be aware of what typeball you had mounted because only 88 of the printing characters were legal at any time, and how they printed depended on what typeball you had mounted.

             Doug Jones
             jones at cs.uiowa.edu