|(mathematics)||Not-a-Number - (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
NaN is encoded as a special bit 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.
[ANSI/IEEE Std 754-1985].