5 May
2020
5 May
'20
10:55 p.m.
On May 5, 2020, at 2:18 PM, Johnny Billquist <bqt
at softjar.se> wrote:
Hi. More stuff to comment on. Fun!
On 2020-05-05 04:13, Thomas DeBellis wrote:
VMS had a pre-CTERM protocol, similar in style to RSX (in other words, roughly an RPC
version of $QIO) but with VMS QIO semantics instead of RSX ones. RSTS supports that one.
The original concept of CTERM is that it's a two layer system, which is why there are
two specs. The foundation layer provides the common machinery, then CTERM (command
terminal) is an operating mode for carrying command line style terminal interaction. The
idea was that other modes would be created for screen editing (EDT style) and forms (like
what FMS-11 supports). I don't think that ever happened, so we're left with a
very heavy protocol to do only a piece of what was originally contemplated.
At one point DEC built a PDP-11 based terminal server that speaks CTERM. It worked, after
a fashion, but it was so large, expensive, and slow, that Bruce Mann decided to see how
quickly he could do better. That's how LAT came into existence. The resulting turf
war was quite spectacular.
Let me clarify this a bit. Leaving LAT aside,
Tops-10 and Tops-20 implement two remote terminal protocols for DECnet. The Digital
common one is CTERM, which runs on all (or most) platforms. Unfortunately, there are some
minor problems with the current Tops-20 CTERM implementation that are annoying. For
example, you can't use space as an un-pause character, which I've been doing since
about 1978. Fixing it (if possible) means I've got to wade into the monitor and that
could mean months before I come back up for air.
Right. And RSTS/E had its own protocol, as did RSX. And they were all sortof optimal for
each system.
The VMS came with CTERM, and everyone was expected to do that one, and it's more akin
to an RPC-based system than some kind of terminal. But, ugly as it is, it's the closest to some kind
of lingua franca. But I think CTERM have issues on every system except VMS (I don't
know, they might have problems even with VMS only, who knows? CTERM is ugly.)
I suppose, though quite possibly the old VMS-specific NRT would have worked just as well
as a lingua franca. That wasn't done because the goal was to do something much
bigger.
It's a bit like the long data packet headers in DECnet Phase IV -- there is lots of
cruft in there that anticipates a whole lot of features that were never created, or even
specified.
But RSX ships with the system specific remote terminal
clients as well, so I have a client for talking to TOPS-20 using that protocol, and a
client for talking to RSTS/E using that protocol...
RSTS does a bit of connect-time magic to allow all four modes to be packaged into a single
client program. So if you install the "unsupported" version, the "set
host" command just magically works no matter wich host you're dealing with, so
long as it has a server installed for the old protocol.
paul