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 10^-128 to 10^127.
A result less than 10^-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.
