# frexp - Man Page

extract mantissa and exponent from a double precision number

## Prolog

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.

## Synopsis

#include <math.h> double frexp(doublenum, int *exp); float frexpf(floatnum, int *exp); long double frexpl(long doublenum, int *exp);

## Description

The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2017 defers to the ISO C standard.

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*.

## Return Value

For finite arguments, these functions shall return the value *x*, such that *x* has a magnitude in the interval [½,1) 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.

## Errors

No errors are defined.

*The following sections are informative.*

## Examples

None.

## Application Usage

None.

## Rationale

None.

## Future Directions

None.

## See Also

The Base Definitions volume of POSIX.1-2017, <math.h>

## Copyright

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

## Referenced By

ldexp(3p), math.h(0p), modf(3p).