HP Integrity NonStop H-Series - Manual (Page 245)

round_style rounding style for type
For the float data type, the value in field radix, which represents the base of the exponential
representation, is equivalent to the symbolic constant FLT_RADIX.
For the types float, double and long double the value of epsilon is also available as
FLT_EPSILON, DBL_EPSILON, and LDBL_EPSILON.
A NaN is a "Not a Number." It is a representable value that nevertheless does not correspond to
any numeric quantity. Many numeric algorithms manipulate such values.
The IEC 559 standard is a standard approved by the International Electrotechnical Commission.
It is the same as the IEEE standard 754.
Value returned by the function round_style() is one of the following: round_indeterminate,
round_toward_zero, round_to_nearest, round_toward_infinity, or round_toward_neg_infinity.