From: lasner@watsun.cc.columbia.edu (Charles Lasner)
Subject: Re: MDL
Reply-To: lasner@watsun.cc.columbia.edu (Charles Lasner)
Organization: Columbia University
Date: Wed, 30 Sep 1992 07:49:47 GMT

In article <8em6K2C00YV9A1kfYt@andrew.cmu.edu> Samuel Roy Helwig <sh4j+@andrew.cmu.edu> writes:
>
>    Does anyone in this group remember MDL (muddle)?  I was told that
>the original Adventure was written in it.  It seems that it was an
>interactive fiction game language.  Is this true?  Also, I was told that
>the Infocom text-based games were written in a language based on a
>subset of MDL.  Finally, if anyone has the original Adventure source (in
>MDL) or anything else in MDL, I'd like to look at it.
>
>                        thanx,
>                        Sam

Adventure was written in PDP-10 Fortran.  Later it was bastardized down to
run on the PDP-11 Fortran.  Later still, the -11 version was made to run
in 32K on the PDP-8.  (I believe that certain features of the original
source would have been better to migrate than the -11 version when bringing
it to the -8 because both the -10 and -8 version support 36 bit variables.)
The -8 version is now available for the DECmate II, III, III+.

The -11 (and indirectly the -8) version port was done by Bob Subnik, originally
of DEC.

Various MIT students wrote MDL and the game ZORK in it.  It was their "answer"
to Adventure, and is somewhat more complex and difficult, and has some
sections that are clearly "borrowed" from Adventure.  For example, Adventure
has a section where the room names are unique, but so similar, you can easily
get lost.  You are in a twisty little maze of passages, all different is
*not* quite the same as you are in a little twisty maze of passages, all 
different, etc.  Zork has a similar region requiring the same fortitude to
get through.  However, it also has another area where they have a similar
name, but are literally identical to trick you.  Also, there is another
section described nonuniquely as a nondescript portion of a coal mine.  Still
another region is laid out mostly as a mirror image of another section.  Some
rooms have random exits, and the exit conditions change as a function of the
state of the game.

Eventually, Infocon hired some of the MIT students and also Bob Subnik.  There
is some confusion regarding the exact chronology of who had/took various
files from MIT but in any case, there was at one point a Fortran-based ZORK
that was known to be a hacked-up Adventure game with data taken from the
MDL version, but the commands were simplified because Adventure's command
parser is feeble by comparison to ZORK, even from the beginning.  The game
scoring of ZORK is such that there are some semi-critical paths in the sense
that you have to get through regions of the game in a reasonable number of
moves, or you lose sources of light.  Some of the counting of said moves
involve using some of the more compound usages of the commands such as 
TAKE ALL VALUABLES.  The stupid Adventure parser needs for you to do commands
like that in several moves.  Thus, when you can't type THROW AXE AT DWARF
and instead have to type THROW AXE, and be asked at what? and answer AT DWARF
you take more turns.  As such, that version had to relax certain mechanisms
of the game to make it playable in this distorted form.  Eventually, a version
that was much smarter appeared in DECUS replacing the hacked-up one that had
a better parser.  This version has even been ported to MS-DOS.  As far as
I understand, it is fairly faithful to a popular "vintage" of the -10-based
MDL version, but not the latest version available there.  Apparently more
features were added, and you have to do more work to be reincarnated, although
this allows a "ghost" mode, and there are more points to earn to win a
maximum score.  Does anyone know if the MS-DOS version supports a "Real"
version of the endgame?

There has also been published a piece of artwork that is a map to the
original version.  It is "creative" enough to avoid certain minor details,
such as one I noticed in the -20 version vs that hacked-up version that I
played on VMS version 1.0: There is a direction out of one of the
twisty maze rooms to connect to another room.  The specific direction is 
something like SE, while in the hacked-up version which MIT never authorized,
it is SW.  The map can be used regardless due to clever drawing.  I believe
it was done by Steve Roy of DEC, and was published by the DEC Professional
people (possibly called RSTS Professional back then?).

Infocon changed the game in ways that are offensive to any seasoned player:

They continued to enhance the parser in likely not-very-important ways, which
isn't problematic, but they *broke* the game up into 3 parts merely to
satisfy the requirement that each part could fit into a 64K CP/M system
without swapping.  This "proscribes" parts of the game, and enforces where
you start at part 2 and part 3, etc.  Moreover, they changed the game
somewhat, adding and deleting features that where specific to the original
and replacing them with features that in some people's opinions aren't
consistent with the prose-style of the original Adventure and ZORK.  (Both
are similar in style, not particulars.)

I understand that they continued development on a PDP-10 for these games,
and that the development language became known as ZIL, later DDL.

Eventually, they brought out MS-DOS versions of these games, but they ran
from paranoidly copy-protected disks with disk copy counts (you can't copy
a copy, and an original can only be copied twice), not from a true
MS-DOS system disk.  Again, the 64K restriction was applied, so the
PC versions are "compatible" with the CP/M ones.

Various people have broken into these disks, and floating around internet
are MS-DOS files that run directly under MS-DOS of the three files in the
"Zork Trilogy" as they call it, including solve files for all three.  Looking
at the solve files, I see that there is only faint resemblance to the
faithful ZORK version which is also floating around the net, possibly in
source form.  It would derive from the version in DECUS for the VAX and -11,
which points out that Bob Subnik is the latest author, and that it's the last
non-commercial version that will be available.  As far as I know, the
MDL version with the extended features is the only complete version with
the extended scoring and full end-game capabilities.  (I think the DECUS
and previous MDL versions can be identified by the max score of 585 and
the newest features are the Bank of Zork with the Gnome of Zurich, and
the large tree with the songbird, while the last MDL-only version scores
something like 616 points and has the ghost mode and complicated 
reincarnation plus additional features.  An expert player who solved the
DECUS submission to the full 585 points wasn't able to get any higher with
the last ZORK version, although he had little time to attempt to find more
features.  In his opinion, all added was upward compatible, because he
found nothing different as he acquired his full score, yet not enough
to fully "win" the game.)

I assume that some of the people with KS20 systems at home can run this
more advanced MDL version; perhaps they can fill us in on the additional
features and scoring points, etc.

Floating around the net is also a C-based version of Adventure that the
authors were extremely careful to be faithful to the original.  They point
out a few bugs in the original, but in all other ways it's the same.  There
are even compatibility switches to handle certain quirks to be as compatible
as anyone would want, etc.

Had the Infocon version of Zork been as faithful, more people would be
complaining less about it.  As it stands, it is perceived as a sleazy way
to make money off of a college hack.  Since the files were taken, MIT
did obtain a copyright on the program to prevent further misuse.

cjl

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