From: magnus@thep.lu.se (Magnus Olsson)
Subject: Zork/Dungeon (was Re: MDL)
Organization: Theoretical Physics, Lund University, Sweden
Date: Wed, 30 Sep 1992 10:47:00 GMT

In article <1992Sep30.074947.148@news.columbia.edu> lasner@watsun.cc.columbia.edu (Charles Lasner) writes:

>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.

IMHO, these "borrowings" are more in the nature of a homage to Advent
than plagiarism - the Zork authors were far too creative in the
"original" portions of Zork for them to have to "steal" any ideas. 

Nowadays, lots of adventure authors (me included) just automatically
include mazes of "twisty little passages, all alike", trolls guarding
bridges, and so on (but preferably with new twists to the plot!) since
they've become part of the interactive fiction mindset, as it were.
Maybe some oldtimer could enlighten me as to whether Advent was such a
classic already when Zork was written for this to be applicable?


It should also be stressed that while Advent didn't have a real
parser, and could only understand two-word "sentences" ("TAKE FOOD",
"KILL DRAGON"), Zork/Dungeon made a really good attempt at
natural-language processing. In fact, many modern games have parsers
that are far inferior to the one in Zork.

>Eventually, Infocon hired some of the MIT students and also Bob Subnik.  

Didn't these people *found* Infocom?

>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. 

This version is available from the comp.sources.games archives, I
think. A few years ago, somebody undertook the huge, thankless task of
translating the source (several hundred kB of spaghetti FORTRAN 66)
into C, and they did a very good job of it! This C version has been
ported to about every conceivable platform, including Macintosh. In
fact even in the Mac version, the leaflet in the letterbox still says
"No DECsystem should be without one" :-)

>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

I found at least one important enhancement: Zork II (the Infocom version) allows you
to say "enter bucket" (any seasoned player knows why you would want to
do that!), but the Fortran version barfs on that - I was totally
baffled, having played the Infocom version first, and had to ask for
help - it turned out the earlier parser only recognized "embark" or
something like that, which is not evry logical.

>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.  

I think the requirement was without *disk* swapping - even after the
breakup, the program uses overlays (don't know if it's of code or of
data). Probably, the full game wouldn't have fit on one floppy disk on
those early CP/M systems.

>This "proscribes" parts of the game, and enforces where
>you start at part 2 and part 3, etc.

That's not very nice, no. But on the other hand, the original Zork
cave is almost too big to be playable...

>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.)

But IMHO at least one of the additions was great: The puzzle with the
demon and the coloured glass spheres in Zork II is really beautiul -
IF at its very best! (I could go into details to motivate this, but I
see no reason to review Zork II so long after its release :-)).

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

For those of you reading this in alt.folklore.computers, ZIL was used
for all the later Infocom text adventures as well.

>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.

On the other hand, nowadays you can buy the "Lost Treasures of
Infocom" for ~$40, which contains Zork I/II/III and 17 other Infocom
games, with no copy protection whatsoever.

>Again, the 64K restriction was applied, so the
>PC versions are "compatible" with the CP/M ones.

Actually, all they ported was the Z-code (the code emitted by the ZIL
compiler) interpreter. The data files are identical for CP/M, MSDOS
and other platforms. 

>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.  

I beg to disagree. Most of the puzzles are identical, as are the parts
of the cave that weren't butchered when the game was split into three.

>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.

A, yes, that's the one I was referring to above.

>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.  

I may be but an inexperienced newbie, but this is actually the first
time I've ever heard this criticism. It seems more or less "everybody
else" (I suppose everybody who didn't first play the MDL version) tend
to view the Infocom Zork trilogy as great classics of IF.

>Since the files were taken, MIT
>did obtain a copyright on the program to prevent further misuse.

A copyright on which version? I'm asking because the Fortran sources
floating around on the net are all "(c) Infocom". And isn't "misuse" a
rather strong term - I've always thought the original authors of Zork
were involved in starting up Infocom and doing what they did to the
game. 

Magnus Olsson                   | \e+      /_
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