[GreenKeys] [External] Re: ASCII

[Jones, Douglas W]

From: WAYNE [teletypeparts at comcast.net] -- Friday, April 2, 2021 2:08 PM

> My ALT key prints right bracket } when hit.

That matches my memory of what ALT was.  The ALT key made use of a code that was unused at the time because the lower case part of ASCII had yet to be standardized.  I think they anticipated using the lower case letters from the very start, but the punctuation codes above lower case z were still not obviously needed, so ALT was up there, just 2 code points away from RUBOUT.

I have the feeling that some early timesharing systems used ALT as a prefix code much like ESCAPE.  So you'd type control sequences that began with ALT followed by a printing letter to get the computer do do odd things.  I don't think I ever used a system that did this.  My experience on 1960' era timesharing systems was on the SDS-940 running the Berkeley Time-Sharing System (AKA Com-Share's Commander I operating system).  There, we used the QED text editor (ancestor of UNIX ed and vi), which had no need for funny control characters or escape sequences for editing.

Some of the teletypes I saw back in the day had an ALT key, but I never recall needing to press it for anything.

         Doug Jones
         jones at cs.uiowa.edu