This manual page is part of the POSIX Programmer’s Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.

These functions shall break a floating-point number num into
a normalized fraction and an integral power of 2. The
integer exponent shall be stored in the int object pointed to
by exp.

For finite arguments, these functions shall return the value x,
such that x has a magnitude in the interval
[0.5,1) or 0, and num equals x times 2 raised to the power
*exp.

If
num is NaN, a NaN shall be returned, and the value of *exp
is unspecified.

If num is ±0, ±0 shall be returned, and the value of *exp
shall be 0.

If num is ±Inf, num shall be returned, and the value
of *exp is unspecified.

Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .