X /X/ n.
1. Used in various speech and writing contexts (also in lowercase) in roughly its algebraic sense of `unknown within a set defined by context' (compare N). Thus, the abbreviation 680x0 stands for 68000, 68010, 68020, 68030, or 68040, and 80x86 stands for 80186, 80286, 80386, 80486, 80586 or 80686 (note that a Unix hacker might write these as 680[0-6]0 and 80[1-6]86 or 680?0 and 80?86 respectively; see glob). 2. [after the name of an earlier window system called `W'] An over-sized, over-featured, over-engineered and incredibly over-complicated window system developed at MIT and widely used on Unix systems.
XEROX PARC /zee'roks park'/ n.
The famed Palo Alto Research Center. For more than a decade, from the early 1970s into the mid-1980s, PARC yielded an astonishing volume of groundbreaking hardware and software innovations. The modern mice, windows, and icons style of software interface was invented there. So was the laser printer and the local-area network; and PARC's series of D machines anticipated the powerful personal computers of the 1980s by a decade. Sadly, the prophets at PARC were without honor in their own company, so much so that it became a standard joke to describe PARC as a place that specialized in developing brilliant ideas for everyone else.
The stunning shortsightedness and obtusity of XEROX's top-level suits has been well anatomized in "Fumbling The Future: How XEROX Invented, Then Ignored, the First Personal Computer" by Douglas K. Smith and Robert C. Alexander (William Morrow & Co., 1988, ISBN 0-688-09511-9).
XOFF /X-of/ n.
Syn. control-S.
XON /X-on/ n.
Syn. control-Q.
xor /X'or/, /kzor/ conj.
Exclusive or. `A xor B' means `A or B, but not both'. "I want to get cherry pie xor a banana split." This derives from the technical use of the term as a function on truth-values that is true if exactly one of its two arguments is true.
xref /X'ref/ v.,n.
Hackish standard abbreviation for `cross-reference'.
XXX /X-X-X/ n.
A marker that attention is needed. Commonly used in program comments to indicate areas that are kluged up or need to be. Some hackers liken `XXX' to the notional heavy-porn movie rating. Compare FIXME.
xyzzy /X-Y-Z-Z-Y/, /X-Y-ziz'ee/, /ziz'ee/, or /ik-ziz'ee/ adj.
[from the ADVENT game] The canonical `magic word'. This comes from ADVENT, in which the idea is to explore an underground cave with many rooms and to collect the treasures you find there. If you type `xyzzy' at the appropriate time, you can move instantly between two otherwise distant points. If, therefore, you encounter some bit of magic, you might remark on this quite succinctly by saying simply "Xyzzy!" "Ordinarily you can't look at someone else's screen if he has protected it, but if you type quadruple-bucky-clear the system will let you do it anyway." "Xyzzy!" It's traditional for xyzzy to be an Easter egg in games with text interfaces.
Xyzzy has actually been implemented as an undocumented no-op command on several OSes; in Data General's AOS/VS, for example, it would typically respond "Nothing happens", just as ADVENT did if the magic was invoked at the wrong spot or before a player had performed the action that enabled the word. In more recent 32-bit versions, by the way, AOS/VS responds "Twice as much happens".
Early versions of the popular `minesweeper' game under Microsoft Windows had a cheat mode triggered by the command `xyzzy<enter><right-shift>' that turns the top-left pixel of the screen different colors depending on whether or not the cursor is over a bomb. This feature temporarily diasappeared in Windows 98, but reappeared in Windows 2000.
The following passage from "The Wonderful Wizard of Oz" by L. Frank Baum, suggesting a possible pre-ADVENT origin, has recently come to light:
"Ziz-zy, zuz-zy, zik!" said Dorothy, who was now standing on both feet. This ended the saying of the charm, and they heard a great chattering and flapping of wings, as the band of Winged Monkeys flew up to them.
The text can be viewed at Project Gutenberg.
Another possible pre-ADVENT origin is discussed at the XYZZY page.