Underflow happen, approximately speaking, after outcome of an arithmetic operation is really so smallest this can not be kept in their designated destination format without pain a rounding mistake definitely larger than normal.
TABLE 2-11 indicates the underflow thresholds for unmarried, double, and double-extended preciseness.
The good subnormal number are the types numbers involving the most minor regular amounts and zero. Subtracting two (favorable) little quantities which can be at the minuscule standard wide variety might generate a subnormal amount. Or, separating the smallest good regular numbers by two creates a subnormal influence.
The existence of subnormal numbers provides greater precision to floating-point calculations that involve small rates, even though subnormal quantities on their own has far fewer items of precision than usual numbers. Making subnormal rates (than going back the response zero) as soon as the mathematically proper consequence keeps magnitude about the tiniest beneficial regular quantity is known as slow underflow.