Date   : Fri, 09 Jun 1989 14:17:05 GMT
From   : ima!cfisun!lakart!dg@decvax.dec.com (David Goodenough)
Subject: QTERM's vt100 emulation (was Re: Remote computing terminals)

From article <8906070705.AA29539@ucbvax.Berkeley.EDU>, by GHK@NCCIBM1.BITNET
("Gary Hutchison"):
> 
>        Charles West asks...
> 
>  > I have found qterm as an excellent vt-100 emulator with a few exceptions.

Thanks for the vote of appreciation - if you saw how small it is you'd wonder
:-)

>  > UALR is on a vax,  phone and help use some other form of screen calls
>  > and will not work with the vt100 in qterm, yet kermit vt52 will. Any 
>  > suggestions
>  > Charles West
>  > CHWEST@UALR.BITNET

One query - I thought that VT100 and VT52 were rather different:

       ^[[n;nH

to move on a VT100 (n is a decimal number, printed as ascii chars: '42'),
but:

       ^[Ycc

to move on a VT52 (c is a character).
Could this perhaps be that the VT52 can't do all the neat tricks that a
VT100 can, and so the programs make do (Just guessing - perhaps someone
who is in the know would like to comment).

>     Many of the VAX system these days expect support of the double
>   width and double height characters available in later versions of
>   DEC's terminals without reguard for the user that has older
>   equipment.  Many of the older VT100 emulators as well as REAL VT100   s
>   will NOT support the enhanced character sets.  This leaves many users rs
>   in the cold.

This is exactly the case with QTERM. Here is how my thinking went.

OK. I should put in _SOMETHING_ to emulate a vt100. Now what can I expect
to be able to do on most CP/M machines without going psychotic trying to
do it.

Clear screen and moveto I already have, and they are mandatory.
VT100's clear to end of line and end of screen, and that's about it.

OK, add those features, assuming the terminal I'm working on can do it
(hence the terminal capability bitmap at 0x022f). Now I can't do any sort
of clever widgetry, like true DEC graphics, or double sized characters,
or funky screen modes, so I'll ignore those.

Now, let's see what I have:

It works with vi, rogue, moria, a couple of VT100 games on GEnie, and a
local BBS with a full screen editor that expects a VT100 emulator (i.e.
ANSI.SYS) in a P.C.

And that's how it came to be the way it is.

Minimal, enough to talk to plane jane programs, but don't expect miracles,
because a Kaypro / Osborne / Televideo / Heath-Zenith / Superbrain can't
do them.

Like so many things (e.g. Zmodem) I _COULD_ expand QTERM and add them, but
I doubt I will - as is QTERM.COM is somewhere just under 14K, but it needs
a whopping 52K of memory for full sized operation, the absolute minimum it
can survive in is 44K. Now if you have a Z-system with a bunch of RSX's
installed, it's going to be pretty cosy.
-- 
       dg@lakart.UUCP - David Goodenough               +---+
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