# frexp(3) — Linux manual page

```frexp(3)                Library Functions Manual                frexp(3)
```

## NAME         top

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

## LIBRARY         top

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

## SYNOPSIS         top

```       #include <math.h>

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

Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):

frexpf(), frexpl():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
```

## DESCRIPTION         top

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

## RETURN VALUE         top

```       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 exp.

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

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

## ERRORS         top

```       No errors occur.
```

## ATTRIBUTES         top

```       For an explanation of the terms used in this section, see
attributes(7).
┌─────────────────────────────────────┬───────────────┬─────────┐
│ Interface                           │ Attribute     │ Value   │
├─────────────────────────────────────┼───────────────┼─────────┤
│ frexp(), frexpf(), frexpl()         │ Thread safety │ MT-Safe │
└─────────────────────────────────────┴───────────────┴─────────┘
```

## STANDARDS         top

```       C11, POSIX.1-2008.
```

## HISTORY         top

```       C99, POSIX.1-2001.

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

## EXAMPLES         top

```       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 exp;

x = strtod(argv[1], NULL);
r = frexp(x, &exp);

printf("frexp(%g, &e) = %g: %g * %d^%d = %g\n",
x, r, r, FLT_RADIX, exp, x);
exit(EXIT_SUCCESS);
}
```

```       ldexp(3), modf(3)