Inform - Welcome - Introduction




2. What does an IF design system do?

Briefly, it translates a textual description of an imaginary world (containing a map of places and stocked with people and items) and rules governing it (such as that, say, the protagonist can't climb to a particular skylight without a ladder) into a computer program which the player can run. This process of translation is called compilation, so the main ingredient of any design system is the compiler.

But such an imaginary world must also be subject to a thousand and one other rules which, while individually obvious, take considerable thought to sort out. For instance: a lighted candle in a glass bottle illuminates the surrounding room but the same candle in a steel box does not; if you put a rucksack in a tea-chest, you can't then put the tea-chest into the rucksack. This web of rules is called the world model. The final game also needs many complex rules to make sense of what the player means by typing something like "put six copper coins in the slot". These semantic rules make up the parser. In the case of Inform, the parser and world model put together run to something like 8,000 lines of textual description, called the library, which the compiler attaches to any game it compiles. Perhaps the major argument for using a design system is that the game designer doesn't have to reinvent these 8,000 wheels each time a new game is to be written.

When the compiler has done its work, the result is a story file or game which is machine-independent in that it can be played essentially identically on a computer of any model (a desktop, a laptop, a mobile device, and so forth). In order to play the story file, the reader needs a fairly simple program called an interpreter. A single interpreter will play all story files ever created with Inform, and also all of the story files published by Infocom, Inc. in the 1980s. Some interpreters can run inside of a webpage, sparing the reader the need to download and install a separate application.

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Last updated 30 March 2002. This site is no longer supported; information may be out of date.
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This page was originally managed by Graham Nelson (graham at gnelson demon co uk) assisted by C Knight.