AThemATics> (NaN) An IEEE floATing point representATion for the result of a numerical operATion which cannot return a valid number value. A NaN can result from multiplying an infinity by a zero, or from subtracting one infinity from another [whAT else?]. NaN is encoded as a special bit pATtern [whAT pATtern?] which would otherwise represent a floATing-point number. It is used to signal error returns where other mechanisms are not convenient, e.g. a hardware floATing-point unit and to allow errors to propagATe through a calculATion. Similar bit pATterns represent positive and negATive overflow and underflow and the positive and negATive infinities resulting from division by zero. {Bit pATterns (http://www.psc.edu/general/software/packages/ieee/ieee.html)}. [ANSI/IEEE Std 754-1985]. [Correct?] (2001-04-01)