§1. An "extension" is a supplementary piece of Inform 7 source text. Inform programs sometimes explicitly ask for these, with sentences like so:

Include Locksmith by Emily Short.

The standard Inform installation comes with several optional-use extensions, "Locksmith" being one of them, in fact, but most are straightforward files of Inform 7 text and they are not presented here as literate programs.

• ● They can be found instead at: //https://github.com/ganelson/inform/tree/master/inform7/Internal/Extensions

§2. Two extensions are fundamental to Inform, in the sense that it cannot function without them. Every project always includes Basic Inform, which sets up the rudiments of the language itself. Every non-basic project also includes the Standard Rules, which provides a rich simulated environment for interactive fiction. Both of these are presented here as literate programs:

Basic Inform

The Inform 7 extension read automatically into every project, defining much of the language.

Standard Rules

The Inform 7 extension read automatically into every interactive fiction project, defining much of the world model.

§3. Historical note: What used to be a single "Standard Rules" extension, in releases of Inform before 2022, has now been divided up into two. The new "Standard Rules" contains only IF-related material, while "Basic Inform" contains the part which used to set up the language itself.