(1) A simulated file folder on disk. Programs and data for each application are typically kept in a separate directory (spreadsheets, word processing, etc.). Directories create the illusion of compartments, but are actually indexes to the files which may be scattered all over the disk. Unix and DOS use the term directory, while the Mac and Windows use the term "folder."

(2) A database of users, hardware devices and applications in a network. See DSML, directory service and metadirectory.

(3) A Web search engine that catalogs Web sites by subject and also manually indexes the site, providing a brief description of its content. Yahoo! was a directory site in its early days, but then added search bots to automatically index pages as the Web grew too large to manually index. See Web search engines, metasearch sites and Yahoo!.