underflow

underflow
floating point underflow
floating underflow

   <programming> (or "floating point underflow", "floating
   underflow", after "{overflow}") A condition that can occur
   when the result of a {floating-point} operation would be
   smaller in magnitude (closer to zero, either positive or
   negative) than the smallest quantity representable.  Underflow
   is actually (negative) {overflow} of the {exponent} of the
   {floating point} quantity.  For example, an eight-bit {twos
   complement} exponent can represent multipliers of 2^-128 to
   2^127.  A result less than 2^-128 would cause underflow.

   Depending on the {processor}, the programming language and the
   {run-time system}, underflow may set a status bit, raise an
   {exception} or generate a {hardware} {interrupt} or some
   combination of these effects.  Alternatively, it may just be
   ignored and zero substituted for the unrepresentable value,
   though this might lead to a later {divide by zero} error which
   cannot be so easily ignored.

   (2006-11-09)