ALAN

Although they are officially versions of the same piece of software, there are, in effect, 3 separate interactive fiction systems with the name ALAN:


 * Version 1, apparently written in 1985, which is known only from occasional references (e.g., page 116, section "VERSION 2.0")
 * Version 2, originally written ca. 1993, which uses source files with the extensions .alan, .ala, and .i, and compiles them to a multi-file format with the extensions .acd and .dat
 * Version 3, first publicly released ca. 2002, which uses source files with the extension .alan and compiles them to a format with the extension .a3c