VT220 COMPOSE Key Question

From: Jerome Fine <jhfine_at_idirect.com>
Date: Wed Apr 4 10:59:03 2001

>Bill Pechter wrote:

> Like the field service manager who was told in the login.com
> to replace his vt220-sh (southern hemisphere) with a -nh
> in order to eliminate the upside down character set. (the downloadable
> characters were a vt2xx goodie and not available to the rest of us
> field circus types with vt52's and 100's.

Jerome Fine replies:

I would appreciate some help with the COMPOSE key on a VT220 LK201
keyboard, more specifically what it can do with the VT220 and the details
of how it can be done.

My actual problem is when I run an old PDP-11 operating system (RT-11),
one of the application keypad keys (the keypad zero key - "<ESC>Op")
sends out the same characters as the <GOLD> key ("<ESC>OP") except
that the last character is upper/lower case. While the SL: (Single Line Editor) is
running and the TTLC$ bit is on in the JSW (Job Status Word), it is possible
to distinguish between both keys, but when an application program runs which
turns off the TTLC$ bit, both keys look the same to the SL: if type ahead
is used while the application program is running.

Is it possible to change the <GOLD> key to output a different sequence of
characters, or more specifically, either change the last character to "I" or
have the <GOLD> key produce "<ESC>[36~" so it in effect becomes
F22. I would then make the ENTER key = F21, PF1= F22 (as I just
said), PF2=F23, PF3=F24 and PF4=F25. Alternatively, I would consider
any other solution - probably even modifying RT-11 so that after an
SS3 ("<ESC>O" sequence), the third character is not modified if the
TANSI$ bit is on (a bit reserved for TECO) which could be a new
command: "SET TT: [NO]ANSI".

Note that when using RT-11 under Ersatz-11 from John Wilson,
it is almost trivial to modify the ENTER, PF1, PF2, PF3, PF4 keys.
So even if the temporary solution is to make these changes to the
characters generated by these 5 keys, at least under Ersatz-11 it
will work very well. Probably, such changes could be controlled
via a FLAGn variable so that they could easily be toggled on and off.

Note that

Any comments would be appreciated.

Sincerely yours,

Jerome Fine
Received on Wed Apr 04 2001 - 10:59:03 BST