HP-UX Floating-Point Guide

Glossary 231
Glossary
performance tuning The
process of refining a program to
make it run faster.
precision The number of bits or
digits in which a value can be
represented. The precision of a
value indicates how close a
floating-point approximation
can be to the exact numeric value
being represented.
QNaN See quiet NaN (QNaN).
quad-precision The HP-UX
implementation of the IEEE
double-extended precision
floating-point format, in which a
value occupies 128 bits: 1 bit for
the sign, 15 bits for the exponent,
and 112 bits for the fraction. See
also single-precision, double-
precision.
quiet NaN (QNaN) A NaN (Not-
a-Number) that usually does not
generate an exception; instead, it
silently propagates unmodified
through an operation. On HP 9000
systems, a QNaN has the most
significant bit of the fraction set
to 0. See also signaling NaN
(SNaN).
range errors Errors generated
by math library routines when
they underflow or overflow. See
also domain errors.
remainder One of the basic
operations defined by the IEEE
standard.
round to nearest The default
IEEE rounding mode, which
specifies that the result of an
operation should be the
representable value closest to the
true value. If two representable
values are equally close to the true
value, the result is the one whose
least significant bit is 0 (that is,
whose last digit is even).
round to nearest integral
value One of the basic operations
defined by the IEEE standard.
round toward +INFINITY The
IEEE rounding mode that
specifies that the result of an
operation should be the
representable value closest to
positive infinity (that is, the
algebraically greater value).
round toward −INFINITY The
IEEE rounding mode that
specifies that the result of an
operation should be the