# frexp man page

## 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.

frexp, frexpf, frexpl — extract mantissa and exponent from a double precision number

## Synopsis

```
#include <math.h>
double frexp(double
```*num*, int **exp*);
float frexpf(float *num*, int **exp*);
long double frexpl(long double *num*, 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.1‐2008 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.*

## See Also

*isnan()*, *ldexp()*, *modf()*

The Base Definitions volume of POSIX.1‐2008, **<math.h>**

## Copyright

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .