---
name: "frexp"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/frexp"
---

# frexp(3)

convert floating-point number to fractional and integral components

## NAME

frexp, frexpf, frexpl - convert floating-point number to fractional and integral components

## LIBRARY

Math library (*libm*, *-lm*)

## SYNOPSIS

```
#include <math.h>
```

**double frexp(double** *x***, int \****e***);** **float frexpf(float** *x***, int \****e***);** **long double frexpl(long double** *x***, int \****e***);**

Feature Test Macro Requirements for glibc (see [**feature\_test\_macros**(7)](/feature_test_macros/7.md)):

**frexpf**(), **frexpl**():

```
    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
```

## DESCRIPTION

These functions are used to split the number *x* into a normalized fraction and an exponent which is stored in *e*.

## RETURN VALUE

These functions return the normalized fraction. If the argument *x* is not zero, the normalized fraction is *x* times a power of two, and its absolute value is always in the range 1/2 (inclusive) to 1 (exclusive), that is, \[0.5,1).

If *x* is zero, then the normalized fraction is zero and zero is stored in *e*.

If *x* is a NaN, a NaN is returned, and the value of *\*e* is unspecified.

If *x* is positive infinity (negative infinity), positive infinity (negative infinity) is returned, and the value of *\*e* is unspecified.

## ERRORS

No errors occur.

## ATTRIBUTES

For an explanation of the terms used in this section, see [**attributes**(7)](/attributes/7.md).

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **frexp**(), **frexpf**(), **frexpl**() | Thread safety | MT-Safe |

## STANDARDS

C11, POSIX.1-2008.

## HISTORY

C99, POSIX.1-2001.

The variant returning *double* also conforms to SVr4, 4.3BSD, C89.

## EXAMPLES

The program below produces results such as the following:

```
$ ./a.out 2560
frexp(2560, &e) = 0.625: 0.625 * 2^12 = 2560
$ ./a.out -4
frexp(-4, &e) = -0.5: -0.5 * 2^3 = -4
```

### Program source

```
#include <float.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
int
main(int argc, char *argv[])
{
    double x, r;
    int e;
    x = strtod(argv[1], NULL);
    r = frexp(x, &e);
    printf("frexp(%g, &e) = %g: %g * %d^%d = %g\n", x, r, r, 2, e, x);
    exit(EXIT_SUCCESS);
}
```

## SEE ALSO

[**ldexp**(3)](/ldexp/3.md), [**modf**(3)](/modf/3.md)