Xyzzy is a magic word from the Colossal Cave Adventure computer game.
In computing, the word is sometimes used as a metasyntactic variable or as a video game cheat code, the canonical "magic word". In mathematics, the word is used as a mnemonic for the cross product.
Modern usage derives primarily from one of the earliest computer games, Colossal Cave Adventure, in which the idea is to explore an underground cave with many rooms, collecting the treasures found there. By typing "xyzzy" at the appropriate time, the player could move instantly between two otherwise distant points. As Colossal Cave Adventure was both the first adventure game and the first interactive fiction, hundreds of later interactive fiction games included responses to the command "xyzzy" in tribute.
The origin of the word has been the subject of debate. Rick Adams pointed out that the mnemonic "XYZZY" has long been taught by math teachers to remember the process for performing cross products (as a mnemonic that lists the order of subscripts to be multiplied first). Crowther, author of Colossal Cave Adventure, states that he was unaware of the mnemonic, and that he "made it up from whole cloth" when writing the game.
Xyzzy has actually been implemented as an undocumented no-op command on several operating systems; in Data General's AOS, for example, it would typically respond "Nothing happens", just as the game did if the magic was invoked at the wrong spot or before a player had performed the action that enabled the word. The 32-bit version, AOS/VS, would respond "Twice as much happens". On several computer systems from Sun Microsystems, the command "xyzzy" is used to enter the interactive shell of the u-boot bootloader.
The low-traffic Usenet newsgroup alt.xyzzy is used for test messages, to which other readers (if there are any) customarily respond, "Nothing happens" as a note that the test message was successfully received. The Google IMAP service documents a CAPABILITY called XYZZY when the CAPABILITY command is issued. If the command XYZZY is given, the server responds "OK Nothing happens."; in mIRC and Pidgin, entering the command /xyzzy will display the response "Nothing happens".
A "deluxe chatting program" for DIGITAL's VAX/VMS written by David Bolen in 1987 and distributed via BITNET took the name xyzzy. It enabled users on the same system or on linked DECnet nodes to communicate via text in real time. There was a compatible program with the same name for IBM's VM/CMS.
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