Add a bunch of autogenerated index entries.

[ibg.git] / chapters / 02.rst

====================
 Tools of the trade
====================

.. epigraph::

   | |CENTER| *C was a captain, all covered with lace;*
   | |CENTER| *D was a drunkard, and had a red face.*

.. only:: html

  .. image:: /images/picC.png
     :align: left

|C|\onventional -- static -- fiction can be written using nothing more than
pencil and paper, or typewriter, or word-processor; however, the
requirements for producing IF are a little more extensive, and the creative
process slightly more complex.

* For static fiction, you first write the text, and then you check it by
  reading what you've written.

* For IF, you still have to write all of the text, but you also have to
  establish what text gets displayed when.  Once you have written the
  necessary Inform instructions, you use a :term:`compiler` program to
  convert them into a playable format.  The resulting information is played
  by an :term:`interpreter` program, which permits you to interact with
  your developing world.

With static fiction What You Write Is What You Read, but with IF the format
in which you initially write the game doesn't bear much resemblance to the
text which the interpreter ultimately displays.  For example, the "William
Tell" game, in the form that we wrote it, starts like this:

.. code-block:: inform

    !============================================================================
    Constant Story "William Tell";
    Constant Headline
                "^A simple Inform example
                 ^by Roger Firth and Sonja Kesserich.^";

    Include "Parser";
    Include "VerbLib";

    !============================================================================
    ! Object classes

    Class   Room
      has   light;

    ...

You will never need to look at it in the form produced by the compiler::

    050000012C6C2C2D1EF6010A0C4416900010303230313031004253FEA90C0000
    0000000000000000000000000000168F000000000000010200000000362E3231
    ...

but, as you'll notice from the full transcript in :doc:`/appendices/c`, the
player will see the following::

     The place: Altdorf, in the Swiss canton of Uri.  The year is 1307, at
     which time Switzerland is under rule by the Emperor Albert of
     Habsburg.  His local governor -- the vogt -- is the bullying Hermann
     Gessler, who has placed his hat atop a wooden pole in the centre of
     the town square; everybody who passes through the square must bow to
     this hated symbol of imperial might...

Clearly, there's more to writing IF than just laying down the words in the
right order.  Fortunately, we can make one immediate simplification: the
translated form produced by the Inform compiler -- those cryptic numbers
and letters held in what's known as the :term:`story file` -- is designed
to be read by the interpreter program.  The story file is an example of a
"binary" file, containing data intended for use only by a computer program.
Forget all that unreadable gibberish.

So that leaves just the first form -- the one starting "``Constant Story``"
-- which represents the tale written as a piece of IF.  That's the
:term:`source file` (so called because it contains the game in its
original, source, form) which you create on your computer.  The source file
is a "text" (or "ASCII") file containing words and phrases which can be
read -- admittedly after a little tuition, which is what this guide is all
about -- by humans.

.. Generated by autoindex
.. index::
   single: IBM PC
   pair: NotePad; text editor

How do you create that source file?  Using a third software program: an
:term:`editor`.  However, unlike the compiler and interpreter, this program
isn't dedicated to the Inform system -- or even to IF.  An editor is an
entirely general tool for creating and modifying text files; you've
probably already got a basic one on your computer (an IBM PC running
Windows comes with NotePad, while an Apple Macintosh has SimpleText or
TextEdit), or you can download a better one from the Internet.  An editor
is like a word-processing program such as MS Word, only much less complex;
no fancy formatting features, no bold or italics or font control, no
embedded graphics; it simply enables you to type lines of text, which is
exactly what's needed to create an IF game.

If you look at the game source above, or in :doc:`/appendices/c`, you'll
notice ``Include "Parser";`` and ``Include "VerbLib";`` a few lines down
from the top of the file.  These are instructions to the Inform compiler to
"include" -- that is, to merge in the contents -- of files called
``Parser.h`` and ``VerbLib.h``.  These are not files which you have to
create; they're standard :term:`library files`, part of the Inform system.
All that you have to do is remember to Include them in every game that you
write.  Until you've a fair understanding of how Inform works, you've no
need to worry about what they contain (though you can look if you want to:
they're readable text files, just like the ones this guide will teach you
to write).

So, we've now introduced all of the bits and pieces which you need in order to
write an Inform adventure game:

* a text :term:`editor` program which can create and modify the
  :term:`source file` containing the descriptions and definitions of your
  game.  Although it's not recommended, you can even use a word-processing
  program to do this, but you have to remember to save your game in Text
  File format;

* some Inform :term:`library files` which you Include in your own game
  source file in order to provide the :term:`model world` -- a basic game
  environment and lots of useful standard definitions;

* the Inform :term:`compiler` program, which reads your source file (and
  the library files) and translates your descriptions and definitions into
  another format -- the :term:`story file` -- intended only for...

* an Inform :term:`interpreter` program, which is what players of your game
  use.  A player doesn't require the source file, library files or compiler
  program, just the interpreter and the game in compiled format (which,
  because it's a binary file not meaningful to human eyes, neatly
  discourages players from cheating).

.. Generated by autoindex
.. index::
   single: IF Archive

All of those, apart from the editor, can be downloaded for free from the IF
Archive.  One approach is to fetch them individually, following the
guidance on Graham's page: visit http://www.inform-fiction.org/ and look
for the "Software" section.  However, if you're using a PC or a Mac, you'll
find it easier to download a complete package containing everything that
you need to get started.

.. _inform-windows:

Inform on an IBM PC (running Microsoft Windows)
===============================================

Although the Windows operating system is upgraded on a fairly regular
basis, its basic capabilities and ways of working have remained
more-or-less consistent for many years.  The information here applies to
PCs running Windows 95 onwards.

.. rubric:: Installing and testing Inform

Follow these steps:

1. Download http://www.firthworks.com/roger/downloads/inform_pc_env.zip to
   a temporary location on your PC.

2. Use a tool like WinZip to unzip the downloaded file, giving you a new
   ``Inform`` folder.  Move this folder (and its contents) to a suitable
   location on your PC -- a good place would be ``C:\My Documents\Inform``,
   but you could also use ``C:\Documents and Settings\yourname\My
   Documents\Inform``, ``C:\Inform`` or ``C:\Program Files\Inform``.  You
   should now have this set of folders:

   .. image:: /images/inform_pc_env.*
      :align: center

   In order to make the download small and fast, these folders include just
   enough to get you started as an Inform designer -- the compiler and
   interpreter programs, the library files, the ``Ruins.inf`` example file
   from the |DM4|, and a template for your own first game.  A few other
   folders are included as placeholders where you could later download
   additional components, if you wanted them.  As soon as possible, you
   should download the |DM4| into the ``Inform\Doc`` folder -- it's an
   essential document to have, and has been omitted from this download only
   because of its 3MB size.

3. To verify that the downloaded files work properly, use Windows Explorer
   to display the contents of the ``Inform\Games\MyGame1`` folder: you will
   see the two files ``MyGame1.bat`` and ``MyGame1.inf``:

   .. image:: /images/filelist1.*
      :align: center

   ``MyGame1.inf`` is a tiny skeleton game in Inform source format.  By
   convention, all Inform source files have an extension of .inf; Windows
   has an inbuilt definition for ``.inf`` files, and so shows its Type as
   "Setup Information", but this doesn't seem to matter.  If you
   double-click the file, it should open in NotePad so that you can see how
   it's written, though it probably won't mean much -- yet.

4. ``MyGame1.bat`` is an MS-DOS batch file (an old kind of text-only
   computer program, from the days before point-and-click interfaces) which
   runs the Inform compiler.  Double-click it; a DOS window opens as the
   game compiles, and you'll see this::

        C:\My Documents\Inform\Games\MyGame1>..\..\Lib\Base\Inform MyGame1
        +include_path=.\,..\..\Lib\Base,..\..\Lib\Contrib | more

        Inform 6.30 for Win32 (27th Feb 2004)

        C:\My Documents\Inform\Games\MyGame1>pause "at end of compilation"
        Press any key to continue . . .

   Press the space bar, then close the DOS window.

   .. note::

      On Windows NT, 2000 and XP, the DOS window closes of its own accord
      when you press the space bar.

5. A story file ``MyGame1.z5`` has appeared in the folder; this is the
   compiled game, which you can play using an interpreter:

   .. image:: /images/filelist2.*
      :align: center

   The extension of ``.z5`` signifies that the story file contains a
   Z-machine game in Version 5 (today's standard) format.

6. Use Windows Explorer to display the contents of the ``Inform\Bin\Frotz``
   folder, and double-click ``Frotz.exe``; the interpreter presents an
   ``Open a Z-code Game`` dialog box.

7. Browse to display the ``Inform\Games\MyGame1`` folder, and select
   ``MyGame1.z5``.  Click ``Open``.  The game starts running in the Windows
   Frotz 2002 window.

8. When you tire of "playing" the game -- which won't take long -- you can
   type the QUIT command, you can select ``File > Exit``, or you can simply
   close the Frotz window.

9. Using the same techniques, you can compile and play ``Ruins.inf``, which
   is held in the ``Inform\Games\Download`` folder.  RUINS is the game used
   as an example throughout the |DM4|.

.. rubric:: Setting file associations

The business of first starting the interpreter, and then locating the story
file that you want to play, is clumsy and inconvenient.  Fortunately, when
you first run the Frotz interpreter, it automatically creates an
association with story files whose extension is ``.z5``.  From now on,
you'll be able to play a game simply by double-clicking its story file.  If
some any reason this doesn't work, you can set up the association yourself:

1. Double-click ``MyGame1.z5``; Windows asks you to select the program
   which is to open it:

   * type ``Z-code V5 Adventure`` as the "``Description for...``"
   * click to select "``Always use this program...``"
   * click ``Other...``

2. Browse to display the ``Inform\Bin\Frotz`` folder, and select
   ``Frotz.exe``.  Click ``Open``.

.. rubric:: Changing the Windows icon

If the Windows icon that's displayed alongside ``MyGame1.z5`` doesn't look
right, you can change it.

1. In Windows Explorer, either select ``View > Options...`` and click
   ``File Types``, or select ``Tools > Folder Options...`` and click ``File
   Types``:

   * select the game file type in the list, which is in order either of
     application (Frotz) or of extension (Z5)
   * click ``Edit...``

2. In the ``Edit File Type`` dialog, click ``Change Icon``.

3. In the ``Change Icon`` dialog, ensure that the file name is
   ``Inform\Bin\Frotz\Frotz.exe``, and select one of the displayed icons.
   Click ``OK`` to close all the dialogs.  The files in the folder should
   now look like this:

   .. image:: /images/filelist3.*
      :align: center

.. rubric:: Compiling using a batch file

You can view -- and of course change -- the contents of ``MyGame1.bat``,
the batch file which you double-click to run the compiler, using any text
editor.  You'll see two lines, something like this (the first chunk is all
on one long line, with a space between the ``MyGame1`` and the
``+include_path``)::

     ..\..\Lib\Base\Inform MyGame1
                 +include_path=.\,..\..\Lib\Base,..\..\Lib\Contrib | more
     pause "at end of compilation"

These long strings of text are command lines -- a powerful interface method
predating the icons and menus that most computer users know.  You won't
need to master the command line interface in order to start using Inform,
but this section will tell you what these particular command lines are
doing.  There are four parts to the first line:

1. ``Inform`` refers to the compiler program, and ``..\..\Lib\Base`` is the
   name of the folder which contains it (addressed relative to *this*
   folder, the one which holds the source file).  Double-dots stand for "go
   to the parent folder".

2. ``MyGame1`` is the name of the Inform source file; you don't need to
   mention its extension of ``.inf`` if you don't want to.

3. ``+include_path=.\,..\..\Lib\Base,..\..\Lib\Contrib`` tells the compiler
   where to look for files like ``Parser`` and ``VerbLib`` which you've
   Included.  Three locations are suggested: this folder, which holds the
   source file (``.\``); the folder holding the standard library files
   (``..\..\Lib\Base``); the folder holding useful bits and pieces
   contributed by the Inform community (``..\..\Lib\Contrib``).  The three
   locations are searched in that order.

   .. note::

      On the command line, you sometimes also see a compiler :term:`switch`
      such as :option:`-S`, used for controlling detailed aspects of how
      the compiler operates.  Rather than do that here, we find it more
      convenient to place any necessary switches at the very top of the
      source file, as we'll explain in the next chapter.

4. ``| more`` causes the compiler to pause if it finds more mistakes than
   it can tell you about on a single screen, rather than have them scroll
   off the top of the MS-DOS window.  Press the space bar to continue the
   compilation.

The second line -- ``pause "at end of compilation"`` -- just prevents the
window from closing before you can read its contents, as it otherwise would
on Windows NT, 2000 and XP.

You'll need to have a new batch file like this to match each new source
file which you create.  The only item which will differ in the new file is
the name of the Inform source file -- ``MyGame1`` in this example.  You
must change this to match the name of the new source file; everything else
can stay the same in each ``.bat`` file that you create.

.. rubric:: Getting a better editor

.. Generated by autoindex
.. index::
   pair: NotePad; text editor

Although NotePad is adequate when you're getting started, you'll find life
much easier if you obtain a more powerful editor program.  We recommend
TextPad, available as shareware from http://www.textpad.com/; in addition,
there are some detailed instructions at
http://www.onyxring.com/informguide.aspx?article=14 on how to improve the
way that TextPad works with Inform.  The biggest single improvement, the
one that will make game development dramatically simpler, is being able to
compile your source file *from within* the editor.  No need to save the
file, switch to another window and double-click the batch file (and indeed,
no further need for the batch file itself): just press a key while editing
the file -- and it compiles there and then.  You can also run the
interpreter with similar ease.  The convenience of doing this far outweighs
the small amount of time needed to obtain and configure TextPad.

.. index::
   single: Apple Macintosh

.. _inform-apple:

Inform on an Apple Macintosh (running OS X)
===========================================

Whereas our instructions for using Inform on a PC apply to just about all
versions of Windows, on the Macintosh we need to be more precise.  Our
guidance here is specifically for Mac OS X, rather than for its predecessor
OS 9, and it may be helpful if we first mention a few relevant differences.

Mac OS X is a robust system constructed around -- or on top of -- BSD
[#bsd]_ UNIX.  There are several kinds of applications that will run on
your Mac OS X:

* Aqua: specifically designed for the Graphical User Interface of Mac OS X,
  and taking advantage of its underlying technologies.  Broadly, there
  are two types of Aqua application:

  * Cocoa: built with programming tools designed for Mac OS X.

  * Carbon: built with the programming tools designed for Mac OS 9 and
    earlier versions, but "translated" to take advantage of OS X.

* Classic: designed to work on Mac OS 9 and earlier versions.  They need to
  run in the Classic environment of OS X; roughly speaking, Classic is an
  emulation of the older Mac systems.

* X11: based on a windowing system designed for the UNIX/Linux world.  They
  need an X-Windows server to run, and their appearance and functionality
  may seem a lot different to what the Aqua user expects.

* UNIX: most UNIX programs (including Linux) will run on your Mac OS X, but
  they usually have to be accessed (or configured) from the UNIX core of
  your Mac, through the Terminal utility.

These differences may be significant, since some of the tools designed to
develop and run IF on a Mac system (for example, ones you'll find in the
Archive) have been built by programmers working in different environments
with varying technologies.  We have tried to select tools that will make
your life easy as a beginner, but in time you may want to investigate
alternative approaches.

.. rubric:: Installing and testing Inform

Follow these steps:

1. Download http://www.firthworks.com/roger/downloads/inform_macosx_env.sit
   to a temporary location on your Mac.

2. Use a tool like StuffIt Expander to unpack the downloaded file (if your
   system configuration is standard, a mere double-click will make it
   self-extract at the current location, if it hasn't already expanded all
   by itself).  You'll now have a new ``Inform`` folder.  Move this folder
   (and its contents) to a suitable location in your Mac.

   .. note::

      It is a good idea for now to place it in your home directory;
      otherwise, a few pre-configured items may not work as explained.
      Once you learn the basics of the configuration, you may move the
      Inform folder to a different location and hack all the defaults like
      the professionals do.

   You should now have this set of folders:

   .. image:: /images/inform_mac_env.*
      :align: center

   In order to make the download small and fast, these folders include just
   enough to get you started as an Inform designer -- the compiler and
   interpreter programs, the library files, the ``Ruins.inf`` example from
   the |DM4|, and a template for your own first game, which you may copy
   and rename each time you begin a new Inform project.  A few other
   folders are included as placeholders where you could later download
   additional components, if you wanted them.  As soon as possible, you
   should download the |DM4| into the ``Inform/Doc`` folder -- it's an
   essential document to have, and has been omitted from this download only
   because of its 3MB size.

3. To verify that the downloaded files work properly, use the Finder to
   display the contents of the ``Inform/Games/MyGame1`` folder: you will see
   the files ``MyGame1.command`` and ``MyGame1.inf``:

   .. image:: /images/mac_filelist1.*
      :align: center

   ``MyGame1.inf`` is a tiny skeleton game in Inform source format.  By
   convention, all Inform source files have an extension of ``.inf``.
   However, Mac OS X may show its Kind as "FUJI BAS IMG document", and try
   to open it with GraphicConverter.  If you're not a regular user of FUJI
   BAS IMG documents, you'll probably want to change this.  Either:

   * right-click on the file (or Ctrl-click)

   * select ``Open with`` and choose ``Other...``

   * in the ``Open with`` dialog, go to the ``Applications`` folder and
     select TextEdit.

   * click to select "``Always open with``"

   * click ``Open``.

   or:

   * right-click on the file (or Ctrl-click)

   * press Option, select ``Always open with`` and choose ``Other...``

   * in the ``Open with`` dialog, go to the ``Applications`` folder and
     select TextEdit.

   * click ``Open``.

   Now, if you double-click the file, it should open in TextEdit so that
   you can see how it's written, though it probably won't mean much -- yet.

   .. note::

      The above process may affect only this specific file.  To change 
      the program that opens by default *all* ``.inf`` files, try this:

      * right-click on the file (or Ctrl-click)

      * select ``Get Info``

      * in the ``Open with`` tab, select TextEdit as the application

      * click the ``Change All...`` button, and confirm the change when asked.

4. ``MyGame1.command`` is a Terminal Shell Script (a UNIX executable
   command-line file, a kind of text-only computer program from the days
   before point-and-click interfaces) which runs the Inform compiler.
   Double-click it; a UNIX window opens as the game compiles, and you'll
   see something like this (the working path will reflect your folder
   hierarchy)::

         Last login: Sat Jul 3 03:07:51 on ttyp1
         Welcome to Darwin!
         /Users/Dave/Inform/Games/MyGame1/MyGame1.command; [Hal:~] Dave%
                /Users/Dave/Inform/Games/MyGame1/MyGame1.command; exit
         Inform 6.30 (27th Feb 2004)
         logout
         [Process completed]

   .. todo::

      Verify this output.  It's what's in the PDF, but the command prompt
      looks like it's in the wrong place.

5. A story file ``MyGame1.z5`` has appeared in the folder; this is the
   compiled game, which you can play using an interpreter:

   .. image:: /images/mac_filelist2.*
      :align: center

   The extension of ``.z5`` signifies that the story file contains a
   Z-machine game in Version 5 (today's standard) format.

6. Use the Finder to display the contents of the ``Inform/Bin/Zoom``
   folder, and double-click ``Zoom``; the interpreter presents an ``Open``
   dialog box.

7. Browse to display the ``Inform/Games/MyGame1`` folder, and select
   ``MyGame1.z5``.  Click ``Open``.  The game starts running in the Zoom
   window.

8. When you tire of "playing" the game -- which won't take long -- you can
   type the QUIT command, you can select ``Zoom > Quit Zoom``, or you can
   simply close the Zoom window.

.. rubric:: Setting file associations

.. Generated by autoindex
.. index::
   single: Infocom

The business of first starting the interpreter, and then locating the story
file that you want to play, is clumsy and inconvenient.  Fortunately, when
the system first "sees" the Zoom interpreter (which is a nice Aqua
application) it automatically creates an association with story files whose
extension is ``.z5`` (and with other Infocom formats).  From now on, you'll
be able to play a game simply by double-clicking its story file.

The files in the folder should now look like this:

.. image:: /images/mac_filelist3.*
   :align: center

.. rubric:: Compiling using a command-line file

If you have followed these instructions to configure your system, every
time that you need to compile your source code you just have to
double-click on the file ``MyGame1.command``.  However, this file is good
only for this folder and for ``MyGame1.inf``.

If you want to start coding another game, you may copy the folder
``MyGame1`` with all its contents and rename it as you please (for example,
``MyGame2`` or something more appropriate).  Inside the folder, you'll also
want to rename the relevant files:

    ``MyGame1.inf`` might become ``MyGame2.inf``, or ``MobyDick.inf``,
    or...

    ``MyGame1.command`` would change to match: ``MyGame2.command``, or
    ``MobyDick.command``.

You can view -- and of course change -- the contents of
``MyGame2.command``, the command file which you double-click to run the
compiler, using any text editor.  You'll see two lines, something like this
(the second chunk is all on one long line, with a space between the
``MyGame1`` and the ``+include_path``)::

    cd ~/Inform/Games/MyGame1/
    ../../Lib/Base/inform630_macosx MyGame1
                      +include_path=./,../../Lib/Base,../../Lib/Contrib

These long strings of text are command lines -- a powerful interface method
predating the icons and menus that most computer users know.  You won't
need to master the command line interface in order to start using Inform,
but this section will introduce you to a few basic concepts to get your
bearings.  The first line changes the working directory to
``~/Inform/Games/MyGame1/``.  The command ``cd`` (also known as ``chdir``,
short for "Change Directory to") lets you travel to the desired folder,
specified by the path, in this case: ``~/Inform/Games/MyGame1/``.  The
``~`` symbol stands for your home directory.  That is, if your user name
were Dave, the above path is equal to::

     /Users/Dave/Inform/Games/MyGame1/

You want to change that line so that it reads: ``cd
~/Inform/Games/MyGame2/``

There are three parts to the second line:

1. ``inform630_macosx`` refers to the compiler program, and
   ``../../Lib/Base`` is the name of the folder which contains it
   (addressed relative to *this* folder, the one which holds the source
   file).  Double-dots stand for "go to the parent folder".

2. ``MyGame1`` is the name of the Inform source file; you don't need to
   mention its extension of ``.inf`` if you don't want to.  You'll want to
   change this to match the name of your new file: ``MyGame2``.

3. ``+include_path=./,../../Lib/Base,../../Lib/Contrib`` tells the compiler
   where to look for files like ``Parser`` and ``VerbLib`` which you've
   Included in the source file (this may sound confusing now, but it will
   make a lot of sense after you've delved a bit deeper into this Guide).
   Three locations are suggested, separated by commas: this folder, which
   holds the source file (``./``); the folder holding the standard library
   files (``../../Lib/Base``); the folder holding useful bits and pieces
   contributed by the Inform community (``../../Lib/Contrib``).  The three
   locations are searched in that order.

   .. note::

      On the command line, you sometimes also see a compiler :term:`switch`
      such as :option:`-S`, used for controlling detailed aspects of how
      the compiler operates.  Rather than do that here, we find it more
      convenient to place any necessary switches at the very top of the
      source file, as we'll explain in the next chapter.

Once you've finished editing those lines, ``Save`` the file (not
``SaveAs``), overwriting the original, and make sure that your text editor
doesn't append an extension like ``.txt`` (TextEdit, the default editor
that comes with OS X, is polite enough to ask you about this).

You'll need to have a new command file like this to match each new source
file which you create.  The only item which will differ in the new file is
the name of the Inform source file -- ``MyGameN``.  You must change this to
match the name of the new source file; everything else can stay the same in
each ``.command`` file that you create.

.. rubric:: Making your own command-line file

There are two peculiarities by which your system understands that
``MyGame1.command`` is a Terminal Shell Script.  One is the extension
``.command``, and the other is an attribute of the file which marks it as
"executable" (the "executable bits").  If it doesn't meet both conditions,
``MyGame1.command`` won't run as it should.  You have to be careful when
editing this file: if you were, for instance, to open it in a text editor
and save it to a different location with a different name, the executable
bits might get lost, and when you double-click it, you would see:

.. image:: /images/mac_exec_error.*
   :align: center

To make a command file from scratch (also, to fix this problem) you can
follow these steps:

1. Open any text editor and write (using your own path)::

        cd ~/Inform/Games/MyGameN/
        ../../Lib/Base/inform630_macosx MyGameN
                      +include_path=./,../../Lib/Base,../../Lib/Contrib

   where ``MyGameN`` stands for the name you have chosen for your Inform
   project.

2. Save the file in the folder ``MyGameN`` and call it ``MyGameN.command``.
   Make sure that the text editor doesn't append a ``.txt`` extension; if
   it does, rename the file manually.

3. Go to ``Applications > Utilities`` and double-click on ``Terminal``.
   This opens the utility which provides you with a set of windows to
   access the UNIX command line.  Supposing the computer is named Hal, and
   the user Dave, you should see something like this::

        Last login: Wed Jun 30 18:05:55 on ttyp1
        Welcome to Darwin!
        [Hal:~] Dave%

4. Every time that you open a Terminal window, you're at your home
   directory (as noted by the tilde after the computer's name).  You can
   travel to your working folder by typing::

        cd Inform/Games/MyGameN

   You'll see how the path changes::

        [Hal:~/Inform/Games/MyGameN] Dave%

   Now you can make the command file executable with::

        chmod 777 MyGameN.command

5. Alternatively, you can omit the cd command if you give the full path to
   ``chmod``::

          chmod 777 ~/Inform/Games/MyGameN/MyGameN.command

   This sets the executable bits for the file ``MyGameN.command``.

6. Close the Terminal window.

Now, every time you need to compile your game, you can just double-click on
``MyGameN.command`` from the Finder.

.. rubric:: Getting a better editor

Although TextEdit is adequate when you're getting started, you'll find life
much easier if you obtain a more powerful editor program.  We'd really like
to recommend one -- there's an exciting list of possibilities at
http://osx.hyperjeff.net/Apps/apps.php?sub=5 -- but at the time of writing
none of them seems outstandingly suited to IF authorship.  If you find one
that works really well, please let us know.

.. rubric:: More about the editor

As well as the ones that we recommend, other good text editors are listed
at http://www.firthworks.com/roger/editors/.  One feature that's well worth
looking out for is "hotkey compilation" -- being able to run the compiler
from *within* the editor.  Another is "syntax colouring", where the editor
understands enough of Inform's syntax rules to colour-code your source
file; for example: red for brackets, braces and parentheses ``[ ]`` ``{ }``
and ``( )``, blue for reserved words like ``Object`` and ``print``, green
for items in quotes like '...'  and "...", and so on.  Syntax colouring is
of great assistance in getting your source file correct and thus avoiding
silly compilation errors.

.. rubric:: More about the compiler

The Inform compiler is a powerful but undramatic software tool; it does an
awful lot of work, but it does it all at once, without stopping to ask you
any questions.  Its input is a readable text source file; the output is a
story file, also sometimes known as a :term:`Z-code file` (because it
contains the game translated into code for the Z-machine, which we describe
in the next section).

If you're lucky, the compiler will translate your source file into Z-code;
perhaps surprisingly, it doesn't display any form of "success" message when
it succeeds.  Often, however, it fails, because of mistakes which you've
made when writing the game.  Inform defines a set of rules -- a capital
letter here, a comma there, these words only in a certain order, those
words spelled just so -- about which the compiler is extremely fussy.  If
you accidentally break the rules, the compiler complains: it refuses to
write a Z-code file.  *Do not worry about this*: the rules are easy to
learn, but just as easy to break, and all Inform designers inadvertently do
so on a regular basis.  There's some additional information about dealing
with these mistakes, and about controlling how the compiler behaves, in
:doc:`15`.

.. rubric:: More about the interpreter

.. Generated by autoindex
.. index::
   single: Infocom

One of the big advantages of the way Inform works is that a compiled game
-- the Z-code story file -- is portable between different computers.
That's not just from one PC to another: exactly the same story file will
run on a PC, a Mac, an Amiga, UNIX workstations, IBM mainframes, PalmOS
hand-helds, and on dozens of other past, present and future computers.  The
magic that makes this happen is the interpreter program, a software tool
which pretends to be a simple computer called a :term:`Z-machine`.  The
Z-machine is an imaginary (or "virtual") computer, but its design has been
very carefully specified, so that an expert programmer can quite easily
build one.  And that's exactly what has happened: a Macintosh guru has
built an Inform interpreter which runs on Apple Macs, a UNIX wizard has
built one for UNIX workstations, and so on.  Sometimes, you even get a
choice; for popular machines like the PC and the Mac there are several
interpreters available.  And the wonderful thing is: each of those
interpreters, on each of those computers, is able to play every Inform game
that's ever been written *and*, as a surprise bonus, all of the classic
1980s Infocom games like "Zork" and "The Hitchhiker's Guide to the Galaxy"
as well!

(Actually, that last sentence is a slight exaggeration; a few games are
very large, or have pictures included within them, and not all interpreters
can handle this.  However, with that small pinch of salt, it's pretty
accurate.)

That's enough waffling: let's get started!  It's time to begin designing
our first game.

.. rubric:: Footnotes

.. [#bsd]
   "BSD" stands for Berkeley Software Distribution, the name of the UNIX
   derivative distributed in the 1970s from the University of California,
   Berkeley, and used collectively for the modern descendants of those
   distributions.