DEC VT102

From: Allison J Parent <allisonp_at_world.std.com>
Date: Mon Nov 23 07:09:20 1998

< - The manual is usually ambiguous, or doesn't tell you
< what happens in all cases under all conditions. I have

Ever read the Vt100 technical manual?

< a copy of the VT220 programmer's pocket guide, and I've seen
< the VT100 and VT220 user's manuals, and this is true of them
By time vt220 started manuals were being trimmed but there was a tech
manual for that one too.

< - The manual doesn't tell you about undocumented behavior.
< If you were writing a complete emulator, you would want all
< the undocumented behavior. (e.g., the VT100 "turn on the bell
< and never turn it off" sequence) Otherwise, you might want some
< of it.

Generally UDOCO is outside spec. forexample a line of 123 chars and what
happens when you switch to Dwide Dheight.

Then again why get mad if the pathological cases are handled wrong when
the basic stuff is poor at best?

To me while in EDT hitting Gold Command and getting the wrong action on
a PC terminal emulator is broken! or hitting ctrlZ to send an exit
to an app gets the procomm help screen. Or worse mapping those keys to
something unresonable for a vt220 (LK201/401 is similar to PC keyboard)
is bizzare.

< - The manual doesn't tell you how the terminal is implemented.
< How many pixels on the screen? How are video attributes stored?
< This isn't usually applicable to behavior, but it could be
< (in some rare circumstance which I don't know about). And it is
< important if you want to write a complete emulator.

Considering the prints for Vt100, technical specs and all were available
NONE of those were secret! If all else fails you could crank up the
Vheight and Hwidth and count them!

< It's easy to claim that your emulator emulates a particular terminal. T
< vtWeb plug-in supposedly emulates VT125. Well, sheesh, they simply see
< VT125 as a slight variation on the VT100, while my reason for getting a
< emulator is to see ReGIS graphics. (No, the plug-in doesn't do ReGIS.
< still looking for a VT125 or Gigi emulator!) But only a description wil
< me find out for certain.

Vt125 is a big variation. The board to do it was a seperate 8085 and
ran it's video in parallel with VT100 base logic (yes chars and graphics).
The GIGI was obscure and uncommon enough to not be a viable reference.
most of the later terminals (Vt330/340) did however do regis.

Allison
Received on Mon Nov 23 1998 - 07:09:20 GMT