the glass tty model of human-computer interaction

[Richard Uhtenwoldt <ru@river.org>]

I'm not blind, just interested in making my software blind friendly.

In the Seventies before the personal computer became popular a lot of
interaction with computers occured via the so-called hardcopy terminal,
like the DECwriter and the Teletype Model 33 before that, which is
essentially a keyboard connected to a printer.  at the end of the session,
you have a long piece of paper that is essentially a transcript of
everything you wrote and everything the computer wrote in reply.

there was also the dumb terminal, also called the glass tty, which differed
from a vt100 in that its cursor was not addressible.  the only way the
computer could update a glass tty was by writing a line of text at the
bottom of the screen and having whatever was on the screen scroll up one
line.  cursor-addressible terminals were also called smart terminals.  now
we may laugh at the idea, but in the Seventies a smart terminal cost
thousands of dollars, hence the market for dumb terminals as a lower-cost
solution.

you could not use vi or Emacs on a hardcopy terminal or a glass tty.  what
you used instead was what I will call a "line editor" which had commands
like "delete the next 5 lines" and "print the next 5 lines".  the Unix
command "ed" and I think also "ex" are line editors.  sighted users came to
prefer so-called visual editors like vi and Emacs in which most of the
display is devoted to an alway-up-to-date view of the thing being edited.
it occurs to me, tho, that if I were a blind user using text-to-speech
hardware or a braille output device, I would prefer a line editor.  but the
Linux Access Howto mentions Emacspeak but does not mention any line
editors.

so, if you are blind and have used a line editor, please tell me whether
you prefer line editors or visual editors.