S> (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)