The Underflow is an error condition that occurs in floating-point arithmetic when the result of a calculation is a number that is closer to zero than the smallest value that can be represented by the floating-point format. It is the opposite of an overflow, which occurs when a number is too large. Every floating-point data type (like a 32-bit single-precision float) has a limited range and precision. There is a specific, smallest positive number that it can represent. If a calculation produces a result that is smaller than this limit (but still greater than zero), an underflow occurs. When this happens, the system typically handles it by "flushing to zero," meaning the result is simply replaced with zero. While this may seem harmless, it can be a problem in certain scientific and engineering calculations where the small, non-zero result is significant.
The underflow causes a loss of information, as the distinction between a true zero and a very small non-zero number is erased. In the context of processing sensitive measurement data, a programmer should be aware that underflow is a possibility, although it is generally a much less common problem in practice than overflow or precision loss.