----------------------------------------
Changes:
* inform
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This is a list of systems that can be used to author adventure games.
Information about TADS, ADVSYS, ADL, OASYS, INFORM and ALAN can be
found here.
Where possible, pointers to existing information (such as books,
magazine articles, and ftp sites) are included here, rather than
rehashing that information again.
If you haven't already done so, now is as good a time as any to read
the guide to Net etiquette which is posted to news.announce.newusers
regularly. You should be familiar with acronyms like FAQ, FTP and
IMHO, as well as know about smileys, followups and when to reply by
email to postings.
For more information on interactive fiction in general, pointers to
books and dissertations, and this group's focus, see David Graves'
"Frequently Asked Questions (FAQ)" posting, which appears periodically
in rec.arts.int-fiction.
This FAQ is currently posted to rec.arts.int-fiction and news.answers.
All posts to news.answers are archived, and will then possible to
retrieve the last posted copy via anonymous FTP from
rtfm.mit.edu
as
/pub/usenet/news.answers/games/adventure-systems
Those without FTP access should send e-mail to
mail-server@rtfm.mit.edu
with
"send usenet/news.answers/finding-sources"
in the body to find out how to get archived news.answers posts by
e-mail.
This FAQ was mostly written by Nathan Torkington, with numerous
contributions by readers of rec.arts.int-fiction. Credits appear at
the end. Comments and indications of doubt are enclosed in []s in the
text. Each section begins with forty dashes ("-") on a line of their
own, then the section number. This should make searching for a
specific section easy.
If you suffer loss in any way, shape or form from the use of
information in this file, then Nathan Torkington expressly disclaims
responsibility for it. It's your own damn fool fault if you go broke,
detonate your computer or eat broccoli as a result of anything you
read here.
As a final note, this FAQ should be regarded as volatile. If this
version is more than two months old, you should consider acquiring a
new version. See the instructions above for details of how to do
this.
Contributions, comments and changes should be directed to
Nathan.Torkington@vuw.ac.nz
----------------------------------------
List of Answers
1 What to look for in a system
2 Writing your own adventure
3 TADS
4 ALAN
5 ADVSYS
6 ADL
7 OASYS
8 INFORM
9 Interactive-Fiction FTP Site
Z Credits
----------------------------------------
1 What to look for in a system
--> Sample adventures, written using the system. This will make
learning how to program the system easy. It will also show you the
workarounds for any clumsiness in the language.
--> The ability to handle non-player characters. This means that
players should be capable of being addressed, eg "amy, take the cat"
should be a valid command to type. Players should be capable of
having turns in the background (to allow movement, thieving, etc).
--> The ability to handle events that occur independent of players
actions (often called fuses and daemons). Fuses are scheduled events,
such has having the bomb detonate three turns after the fuse is lit.
Daemons are routines that are called once every move.
--> Documentation. You need, at least, a reference page. Sample
code helps, and a full explanation of the order that routines are
called by the game kernel (eg ADL calls the following for each direct
object: the actor's action, the verb's preaction, the indirect
object's action, the direct object's action, then finally the verb
action. If any one of these procedures returns a true value, then
that procedure is assumed to have completed the command handling for
that direct object, and processing continues for the next direct
object. After all the direct objects are handled this way, the room's
action is called and the kernel continues).
--> Distribution mechanism. Is the game code fully yours to use? Do
you have to pay a fee for commercial distribution? For shareware
distribution? For free distribution? Are you obligated to offer the
source code to the game interpreter as well as your compiled
adventure?
--> Is it object oriented? If so, you will probably have an easier
time of writing your adventure -- text adventure worlds lend
themselves to object orientation better than some other forms of
simulation. Of course, learning the subtleties of the OO method might
be harder than writing your game using a traditional (non-OO) system.
--> Is the game language functional or procedural? That is, does the
language look like LISP (lots of parentheses) or a kind of cross
between BASIC and C (curly braces {} are a dead giveaway for C
lookalikes). You might have to learn a whole new programming style if
you write your adventure in a language style that you are unfamiliar
with.
----------------------------------------
2 Writing your own adventure
Dave Librik posted Dave's Quick Guide To Getting Started with TADS,
which was so good that I've generalised it to cover most adventure
systems.
Above all else, the key to learning how to write adventures is to
start writing one. Practice not only makes perfect, but
trial-and-error makes passable too. You will need the following:
--> a language/kernel reference manual for your adventure system.
You might have to register your system to get this.
--> printouts of sample adventures. Staple each printout, so the
printouts won't get lost or confused. Also print out any
standard libraries that the system comes with (eg adv.t in TADS
or standard.adl in ADL).
Now:
--> familiarise yourself with the basics of the language. Subtleties
(syntax details, daemons, fuses) should be left for later -- just
the basic ideas of objects, inheritance (if your language is OO),
printing text. It might help if you already knew a language in
the same style (procedural or functional) as the language you
will have to program in.
--> read the sample adventures. Get a feel for how items and rooms
are defined. This step is fairly important -- you will write
most of your adventures by strategically stealing the way someone
else has written theirs (software professionals call this "code
reuse" -- we call it laziness).
--> make a copy of one of the simpler sample adventures. Take out
all the stuff specific to that adventure (rooms, players,
objects, etc) and just leave the verbs, the initialisation code,
and the definition of the player's character. Now start writing
your own adventure. Start simple -- a couple of rooms and some
objects to take.
--> add more complicated things. For ideas of things to add, it
helps to have played some adventures. Try adding code for doors,
containers, other actors, new verbs, fancy verbs that need
indirect objects. Use the sample adventures that came with the
system as a reference for using things.
--> if the sample adventure you modified included standard code for
players or startup (std.t in TADS), then include those libraries
and customise them to your taste (you should have no trouble
reading and understanding the code by now). Add any of your own
initialisation code to this.
--> when you want to start making significant changes to the
behaviour of the adventure, you will have to change any standard
libraries that your adventures includes (standard.adl in ADL,
adv.t in TADS). Whenever you make a change, comment at the top
of the file why you make the change, and exactly what you
changed. This is so that when your later adventures need any of
the features you have added, it will be easy to add them. It
also helps when newer releases of the adventure system arrive --
you can make the changes to the new standard library with minimal
hassle.
--> now realise that what you have written is a practice game. It
probably wasn't well laid out, or well planned, or even
consistent. To write your Real Adventure, you will have to go
through some serious Design and Implementation.
The classic Colossal Cave adventure has been rewritten in TADS by Dave
Baggett <dmb@ai.mit.edu> and is available in source from the IF
archive (see Section 9) in the directory
if-archive/games/adventions/others/ccr.tar.Z
There is also an INFORM version which Graham Nelson derived from the
TADS sources.
The documentation to INFORM (see section 8) contains a wealth of
material relevant to designing adventure games under any system. This
is highly recommended for those wishing to write their own games.
----------------------------------------
3 TADS
TADS stands for "Text Adventure Development System". It is available
for MSDOS, Atari ST, Macintosh, Sun, SGI, Linux, DEC/MIPS, and NeXT
computers at the moment. It is available via anonymous FTP as
ftp.gmd.de:if-archive/programming/tads/
The latest version, TADS 2.1, features virtual memory, expanded C-like
syntax, improved documentation and an improved debugger.
TADS is released by High Energy Software, and is shareware. Shareware
games can (and have) been written using TADS, and commercial
distribution of games written using TADS seems allowable. TADS
consists of a compiler (which converts the source code to adventures
into TADS game code) and an interpreter (which reads the TADS game
code produced by the compiler and lets users play the game).
Registered users get a form of the interpreter which can be combined
with the game code file to form a single executable for distribution.
The interpreter is licensed for shareware use, you don't have to pay a
penny if you distribute your games via shareware. If you plan to sell
it commercially, contact Mike Roberts for information on getting the
rights.
The TADS language is declarative and object-oriented. It appears very
C-like, and the syntax shouldn't be too difficult to learn by people
who know C or Pascal. The language provides a basic syntax, some text
manipulation and support for object-oriented programming. The
interpreter provides parsing, question-and-response I/O format, and
activation of the appropriate methods in objects depending on what the
player types. The language has support for actors, fuses and daemons.
TADS comes with the source to a trivial adventure, and source to an
Infocom quality game ("Ditch-Day Drifter"). On registration of the
package, a manual can be obtained. The manual for v1.* is very good
(although it doesn't explain well the contents of the standard library
file, adv.t). The v2.1 manual is apparently twice the size of v1.
The prices for versions < 2.0 are:
TADS shareware fee: 25.00
Includes printed TADS Author's Manual, the
current TADS software on specified media,
plus the source code for "Ditch Day
Drifter," a complete sample game.
Deep Space Drifter: 10.00
Includes "Deep Space Drifter" on the disk
media specified above, plus a complete map
of the game and the DSD Hint Book.
California residents please add 7ales tax.
The price of v2.1 is US$40 (+ California sales tax for California
residents, $3 for shipping and handling within the US and Canada, or
$8 for international air mail). If you register "Deep Space Drifter"
at the same time, the total is only US$50 (plus sales and shipping).
For more information, contact:
--> BBS: 415 493 2420 (set modem to 14400-N-8-1)
--> CompuServe: 73737,417
--> GEnie: M.ROBERTS10
--> Internet: 73737.417@compuserve.com
--> US Mail: High Energy Software, PO Box 50422, Palo Alto, CA
94303.
Dave Baggett has placed his WorldClass library, a free TADS class
library which entirely replaces ADV.T, on the IF archive (see section
9) as
ftp.gmd.de:/if-archive/programming/tads/worldclass
This library is about three times the size of ADV.T and is
correspondingly more powerful.
----------------------------------------
4 ALAN
The Alan System is a special purpose language for creating interactive
fiction or text adventures. It consists of a compiler which compiles
Alan source to an intermediate form and an interpreter that interprets
such an intermediate form.
The Alan language was designed to give the maximum functionality from
as little code-writing as possible. This means:
--> the system provides default behaviour for many things (which the
author can override).
--> the system directly supports locations, objects, actors and
other concepts natural to the domain of interactive fiction.
--> the author can extend the allowable input of the player, and
connect actions to that input.
It is also a safe language in the sense that extensive compile-time
checking makes it nearly impossible to produce a game that crashes or
behaves inconsistently.
The language is declarative and very close to English. It supports
fuses and daemons by use of events, and is object-inspired (all
declarations are local to entities, but no inheritance).
The Alan System is request-ware. The complete system is available
without charge through electronic mail. Send a message with a single
line:
SEND INFO
to
alan-request@softlab.se
for more information.
The complete distribution includes the compiler, the documentation, a
100+ page manual in plain text and postscript versions, some examples
and the interpreter with debugging support. The interpreter can be
redistributed with your games, so this seems to open the way for
commercial and shareware release.
The manual is available from the IF archive (see Section 9) in the
directory
if-archive/programming/alan/manual.zip
The current version of Alan is 2.4 which runs on Sun/UNIX, Amigas, PCs
(MSDOS and OS/2) and VAX/VMS. A major revision of the manual is
planned, and a larger game is also being worked on for release.
The authors may be contacted at:
alan-request@softlab.se pseudo-mail-server for deliveries
thoni@softlab.se
gorfo@ida.liu.se
----------------------------------------
5 ADVSYS
ADVSYS (ADVenture SYStem) was written by David Betz, and the latest
version (1.3) is based on the 1986 release of 1.2 which seems more
prolific. This package consists of LaTeX and ASCII documentation, C
source code for the compiler and interpreter, and the source code for
several sample adventures (as well as a demonstration library). It
was written up in Byte magazine [reference here].
The language is LISP-like, and object-oriented. The game has no
knowledge of the difference between actors, objects, locations, etc --
all this must be present in the game code. As such, the runtime
library is rather more complex than might be desired. Actors, fuses
and daemons can all be implemented easily.
There is [somewhere] a library of code developed by the (now-defunct)
ADVSYS mailing list. This provides rather better code than the
library distributed with ADVSYS, and includes containers and limits to
containment.
The documentation says "Permission is hereby granted for unrestricted
non-commercial use". You might have to contact David Betz to ask
about commercial and shareware distribution.
ADVSYS was posted to comp.sources.games, and appeared in volume 2. It
can, therefore, be found on any FTP site that archives it. Two such
FTP sites are:
ftp.uu.net:/usenet/comp.sources.games/volume2/advsys
wuarchive.wustl.edu:/usenet/comp.sources.games/volume02/advsys
An ANSI C version is available, on the IF Archive site (see section 9).
----------------------------------------
6 ADL
ADL (Adventure Design Language) was written by Ross Cunniff and Tim
Brengle. The package posted to comp.sources.games consists of plain
ASCII documentation, C source for a compiler, interpreter and
debugger, and several sample adventures (ranging from the complex to
the very simple) which illustrate the various features of ADL.
ADL is a declarative, semi-object-oriented language. It has the
concept of methods (procedures that are attached to objects) but not
inheritance. This means that an object-oriented style of programming
will be rather inhibited.
The language recognises actors, locations and objects as being
distinct. Fuses and daemons are supported in the language. A
standard library comes with the package, that gives a firm foundation
to write games on.
The documentation is very close to being excellent, and contains a
full language reference. The documentation doesn't appear to contain
any guide to distribution of anything but the source code. Therefore
it may be legal to distribute the compiled interpreter with your game.
For more information, you should contact the authors at:
USMAIL: Ross Cunniff
636 La Grande, #7
Sunnyvale, CA 94087
----------------------------------------
7 OASYS
OASYS stands for Object-Oriented Adventure System. It was distributed
in comp.binaries.ibm.pc in 1992, and is available from any FTP site
which archives cbipc. It was written by Russell Wallace, who is
reachable via e-mail as RWALLACE@vax1.tcd.ie.
The package has documentation, two sample adventures, C source for the
compiler and interpreter, and MS-DOS binaries for the compiler and
interpreter. The source is missing an include file (Russell will
provide it on request) and shouldn't be very difficult to port to non
MS-DOS systems.
The language is declarative, and (not really) object-oriented. The
major limitation of the parser is that it forces the player to type
the adjectives along with the noun ("ceramic key" must be typed, even
if there are no other keys accessable). This may be fixed later.
Actor support is provided, and players can issue commands to other
actors. [fuses? daemons?]
There don't appear to be any legal restrictions, so you can probably
distributed compiled interpreters with your commercial/shareware/free
games.
----------------------------------------
8 INFORM
INFORM was written by Graham Nelson at Oxford University, UK. It is a
compiler that produces Infocom story files. There are many
public-domain interpreters for these files, available from the
Interactive Fiction archive site.
The compiler is written in ANSI C, and is freely available (but not
public domain). It produces version-3 files from a fairly C-like
source language, and can produce version-5 files as well (an important
innovation since they are twice as large --- Trinity-sized instead of
Zork-1-sized).
The manuals have been hugely improved for Inform 5.4, and are now
divided into four:
The Inform Designer's Manual
- entirely rewritten as a tutorial with detailed appendices for
reference, many exercises with solutions provided and an index;
The Inform Technical Manual
- low-level features, porting notes, modification history;
The Specification of the Z-Machine
- everything currently known about Infocom's run-time format, which
we believe is now completely deciphered, and Inform assembly language;
The Craft of Adventure
- a short book about writing adventure games, and not about any system.
A new edition of the last of these is still being revised, but the
first three are available in both TeX and PostScript form (properly
typeset and coming to about 105, 20, 40 pages respectively). The
Designer's Manual also comes in a plain ASCII text version.
There are now four example games: Advent (the Colossal Cave port,
which is quite large); Adventureland (an easy example, the Scott Adams
classic); Toyshop (a game with few rooms but very many exotic objects,
to demonstrate unusual features and programming tricks), and Balances
(a pastiche of Infocom's "Enchanter" trilogy, which demonstrates how
to program the parser in cunning ways). These all come with source.
INFORM is genuinely free, and the rights to a game it produces belong
to the author of the game.
----------------------------------------
9 Interactive-Fiction FTP Site
The FTP site ftp.gmd.de:/if-archive contains most, if not all,
of the software mentioned here as well as interpreters for Infocom
games, source and binaries for many other games and sundry information
files too numerous to mention.
ftp.gmd.de:/if-archive is mirrored in
wuarchive.wustl.edu:/doc/misc/if-archive.
The latest FAQ is stored here as
if-archive/info/authoring-systems.FAQ and as
if-archive/programming/general-discussion/authoring-systems.FAQ
----------------------------------------
Z Credits
Nathan Torkington <Nathan.Torkington@vuw.ac.nz>, David Librik
<librik@cory.Berkeley.EDU>, Dave Baggett <dmb@case.ai.mit.edu>, Thomas
Nilsson <thoni@ida.liu.se>, Graham Nelson <nelson@vax.ox.ac.uk>,
Volker Blasius <blasius@gmd.de> and the documentation for the various
systems mentioned here.