[Simh] going back to the VAX console with CTRL P

[Mark Pizzolato]

On Tuesday, August 6, 2019 at 11:28 AM, Nelson H. F. Beebe wrote:
> List discussions today have commented on the default of Ctl-E (ASCII
> 005) as the SIMH escape character, to return from a guest O/S to SIMH itself.
> 
> That character is commonly used in the emacs editor family, and in Unix and
> TOPS-20 shells, usually to move to end of line.  I was long ago sufficiently
> unhappy with the SIMH choice, that I patched local code before building it with
> a change like this one:
> 
> % diff $S/simh/gnu-linux-ia32/simhv36-0/sim_console.c sim_console.c
> 92c92
> < int32 sim_int_char = 005;                               /* interrupt character */
> ---
> > int32 sim_int_char = 036;                               /* interrupt character */
> 
> [From a 2006-vintage diff in my records].
> 
> I don't recall whether, at the time, there was any facility for redefining it in the
> SIMH startup scripts, avoiding the need to make a trivial tweak to the SIMH
> source code.

Well, the change that added the SET CONSOLE WRU=nnn command was added 
in 2004, so that specific patch wasn't really needed then.

> My 036 choice corresponds to Ctl-^ (caret), a character unused by either
> command shells, or the emacs family (although the latter can, of course, be
> easily configured or programmed to do so, because their input model is that
> EVERY character runs a command, even if most just insert themselves in the
> buffer).
> 
> The ssh and Kermit intercomputer communications systems both use two-
> character escape sequences, because that is an even better choice:
> such escapes are rare events, and having to type an extra character is of
> neglible human overhead.  Otherwise, keyboard input to the remote system
> works much as expected, and all keyboard characters can be input without
> interference.
> 
> Those of us who run virtual machines on emulation software where the
> console is implemented in a Web browser window are continually impacted by
> some characters being grabbed by the browser before the VM console can
> even see them.  We had similar problems in Denmark, where THREE essential
> vowels (Danish has nine such) are missing from the US-layout keyboards that
> we then had.

All are reasonable points and of real concern when the simh control activities 
are done in the same session as the simulator's console port.

The simulator's console port can be separated from the control activites of 
the simulator when it is connected to a TELNET session with the command:

          sim> SET CONSOLE TELNET=listenportnumber

A telnet session to localhost:listenportnumber will have all characters passed 
without any unexpected interactions affecting operating the simulator.