Interpreter

An interpreter (or terp, for short) is an application program ("app") which reads a story file and presents the game contained inside that file to the player. The interpreter itself is not part of the game, although it may provide shortcuts to make the playing more convenient. Many interpreters allow the player to enter commands (i.e., LOOK or GO NORTH) by pressing a single key combination (a "hotkey"). In addition, some interpreters allow the player to tweak display options to his liking (i.e., fonts and colors).

The interpreter's function in interactive fiction is akin to that of a movie projector in motion pictures. It translates the "raw material" of the work into a more palatable format for humans.

Technically, interpreters are usually virtual machines. They don't care about the higher-level language used to create the compiled code that is run on them. The Z-machine, for example, is usually programmed with Inform, but Infocom, who created it, used a compiler and language called ZIL. Glulx is similar to the Z-Machine, but designed to remove some limitations of that design, and also is typically programmed with Inform.

Interpreters by Platform

One of the advantages to the Virtual Machine concept is cross-platform compatibility. A story-file only needs to be written once and can be run on any computer on which an interpreter exists for similar story files. This makes the interpreter the only piece of software that needs to be written for a specific platform.

There are interpreters for nearly every modern (and many not so modern) computing platforms.

Some interpreters are usable for most formats of interactive fiction.

• For Mac OS X there is Lectrote and Spatterlight
• For Unix systems there is Gargoyle and Lectrote
• For Windows there is Lectrote
• For Android and iPhone/iPad there are many choices Mobile apps for downloading or playing IF
• For Ubuntu Touch there is Gelek Vanilla

You can find a popular interpreter for your platform and IF format in the following table:

	Zcode	TADS1	Glulx	Hugo	ADRIFT	Alan2	Alan3
Story File Extension	.z5, .z8,.z3,.zblorb .zlb (other .z# or .dat, rarely)	.gam, .t3	.ulx, .blb, .gblorb .glb	.hex	.taf	.acd/.dat	.a3c/.a3r
Android	Fabularium, JFrotz, Incant, Son of Hunky Punk, Text Fiction, Thunderword, Twisty, ZMPP	Fabularium, Son of Hunky Punk, Thunderword	AndroidIF, Fabularium, Incant, Thunderword	Fabularium, Thunderword	Fabularium	Fabularium, Thunderword	Fabularium, Thunderword
DOS	DOS Frotz	DOS TADS	Git for Dos	Hugo	SCARE	ARun, Glk ARun	(none)
Linux	Gargoyle, Frotz (redhat binary RPM), Lectrote	Gargoyle, QTads	Gargoyle, Lectrote, Zag	Gargoyle, Hugo wxGTK, Hugor, Lectrote	Gargoyle, SCARE	Gargoyle, Glk Arun	ARun in Full Distr, Gargoyle
Mac OS 10.12 Sierra	Gargoyle (unofficial build for MacOS 10.12), Lectrote	Gargoyle (unofficial build for MacOS 10.12)	Lectrote	Lectrote	?	(none)	?
Mac OS X	Gargoyle, Lectrote, Spatterlight, Zoom	CocoaTADS, Gargoyle, HyperTADS2, Spatterlight, QTads	Lectrote, Spatterlight, Zag	Spatterlight, Hugo, Hugor, Lectrote	Spatterlight, SCARE	(none)	Arun in Full Distr, Spatterlight
Mac System 9	MaxZip, Nitfol	HyperTADS	Glulxe for Mac	Hugo	(none)	ARun, Glk ARun	(none)
Palm	Frobnitz	(none)	CellarDoor	Hugo Palm	(none)	(none)	(none)
PocketPC	Pocket Frotz	Pocket TADS	Git PocketPC	Hugo WinCE	(none)	(none)	(none)
RISC OS	Frotz, Zip2000	AcornTADS	(none)	AcornHugo	(none)	(none)	(none)
Symbian	Frotz 1.08 uiq	?	?	?	?	?	(none)
Java	ZPlet	?	Zag	?	JAsea	?	(none)
Windows	Filfre, Windows Frotz, Lectrote	Gargoyle, HTML TADS Playkit, QTads,	Filfre, Git, Glulxe, Lectrote, Zag	Hugo Multimedia Interpreter, Hugor, Lectrote	ADRIFT Runner	ARun, Gargoyle, Glk Arun	Gargoyle, WinARun

¹ As of April 2012, only QTads is compatible with TADS 3.1 games. Other TADS interpreters are compatible with TADS 3.0 games, but may not support HTML TADS graphic and sound features.

² HyperTADS isn't native to MacOS X yet, but runs in the Classic compatibility environment.

These are not all the interpreters available, just some of the most popular ones for the most popular platforms. The IF Archive has a fairly comprehensive, if not exactly friendly, list of interpreters that you can download:

• http://www.ifarchive.org/indexes/if-archiveXinfocomXinterpreters.html

Also see Websites for downloading or playing IF, and Mobile apps for downloading or playing IF.

Types of Interpreters

• Z-machine
  This is the one that Infocom invented in the late 1970s.
• Glulx
  This is something of a redesign of the Z-Machine with many new features.
• TADS
  This is a system designed by Mike Roberts in the late 1980s. TADS2 is well established and TADS3 is a redesign.
• Hugo
  This is a system designed by Kent Tessman, somewhat inspired by Inform and TADS but designed to be easier to work with.