Xyzzy
xyzzy or XYZZY may refer to:
See also
Cross product
In mathematics and vector calculus, the cross product or vector product (occasionally directed area product to emphasize the geometric significance) is a binary operation on two vectors in three-dimensional space (R3) and is denoted by the symbol ×. Given two linearly independent vectors a and b, the cross product, a × b, is a vector that is perpendicular to both and therefore normal to the plane containing them. It has many applications in mathematics, physics, engineering, and computer programming. It should not be confused with dot product (projection product).
If two vectors have the same direction (or have the exact opposite direction from one another, i.e. are not linearly independent) or if either one has zero length, then their cross product is zero. More generally, the magnitude of the product equals the area of a parallelogram with the vectors for sides; in particular, the magnitude of the product of two perpendicular vectors is the product of their lengths. The cross product is anticommutative (i.e. a × b = −b × a) and is distributive over addition (i.e. a × (b + c) = a × b + a × c). The space R3 together with the cross product is an algebra over the real numbers, which is neither commutative nor associative, but is a Lie algebra with the cross product being the Lie bracket.
Xyzzy (computing)
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".
Origin
Modern usage is 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. According to Rick Adams, the sequence of letters "XYZZY" has been used as a mnemonic to remember the process for computing cross products.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.
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