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From: toma@tekgvs.TEK.COM (Tom Almy)
Newsgroups: comp.lang.forth
Subject: multi-user Forth
Message-ID: <2496@tekgvs.TEK.COM>
Date: Wed, 29-Jul-87 15:13:21 EDT
Article-I.D.: tekgvs.2496
Posted: Wed Jul 29 15:13:21 1987
Date-Received: Sat, 1-Aug-87 02:07:47 EDT
Reply-To: toma@tekgvs.UUCP (Tom Almy)
Distribution: world
Organization: Tektronix, Inc., Beaverton, OR.
Lines: 44


In the recent deluge of postings, I seem to remember someone asking about
multitasking/multiuser Forths.  I have modified a copy of the public domain
F83 (by Laxen and Perry) for multiuser (it is normally just multitasking).
I will supply it (sources included, of course) to anyone who requests it.

I did the modifications several years ago on the 8080 version 1.0, so anyone
wanting multiuser on the 8086 version will have to examine the sources and
make the appropriate modification to the 8086 version.  I ran the program
with three users on a Lobo MAX-80 (5 Mhz Z-80, 8" DSDD floppies, and 256k
ram disk) with excellent performance.  The program should work on an IBM PC
if UNIDOS is used, with the only necessary mods being serial port access.

Important details:
	The FORTH vocabulary "forks" so that each user additions to FORTH
are private to his/her tasks.  Other vocabularies existing before switching
to multiuser are shared, allowing shared variables between users.
	Sufficient variables have been converted to user variables so that
each user can edit separate screen files, and can have different terminal
definitions.  The editor has been modified for much more efficient display
update (very important when running multiuser or over serial ports).
	A PolyForth "TYPIST" like task is provided.  The typist can be 
considered as another user task which can receive character input from any
user and sends all output to the printer.  To use, type a line "TYPIST: <commands>".
If the typist is busy, you will be told so, and you can wait or hit a key
to abort the (queued) command.  When the typist is ready to accept the
command, your task resumes.  If the typist encounters any error, the error
will be reported back to your terminal!
	A multitasking demo is provided -- Tower of Hanoi using message
passing among a dozen tasks rather than recursion.  This demo can be executed
by all users simultaneously!  (A problem: FORGET needs to be modified so
as to delete any forgotten tasks, currently it leaves them chained in and
the system will soon crash after forgetting).
	(Totally irrelevent to this discussion) the words INSTANCES_OF and
USERS_OF are provided which do entire vocabuary (or all vocabulary) searches
for words which either use a given word or are instances of (i.e. CREATE DOES>)
a given word.  I got the idea for this from the Smalltalk browser.

Reply to me if interested.  I could try emailing it, or can USmail it if sent
a Self Addressed Stamped Mailer and a floppy (IBM PC Format only!!).

Tom Almy
toma@tekgvs.TEK.COM
{most hubs}!tektronix!tekgvs!toma