## NAME

`fpclassify`

,
`isfinite`

, `isinf`

,
`isnan`

, `isnormal`

,
`signbit`

, `finite`

,
`finitef`

, `isinff`

,
`isnanf`

—
classify a floating-point
number

## SYNOPSIS

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

`int`

`fpclassify`

(`real-floating
x`);

`int`

`isfinite`

(`real-floating
x`);

`int`

`isinf`

(`real-floating
x`);

`int`

`isnan`

(`real-floating
x`);

`int`

`isnormal`

(`real-floating
x`);

`int`

`signbit`

(`real-floating
x`);

## DESCRIPTION

The
`fpclassify`

()
macro takes an argument of `x` and returns one of the
following manifest constants:

`FP_INFINITE`

- Indicates that
`x`is an infinite number. `FP_NAN`

- Indicates that
`x`is not a number (NaN). `FP_NORMAL`

- Indicates that
`x`is a normalized number. `FP_SUBNORMAL`

- Indicates that
`x`is a denormalized number. `FP_ZERO`

- Indicates that
`x`is zero (0 or -0).

The
`isfinite`

()
macro returns a non-zero value if and only if its argument has a finite
(zero, subnormal, or normal) value.

The
`isinf`

(),
`isnan`

(),
and
`isnormal`

()
macros return non-zero if and only if `x` is an
infinity, NaN, or a non-zero normalized number, respectively.

The
`signbit`

()
macro takes an argument of `x` and returns non-zero if
the value of its sign is negative, otherwise 0.

## SEE ALSO

## STANDARDS

The `fpclassify`

(),
`isfinite`

(), `isinf`

(),
`isnan`

(), `isnormal`

(), and
`signbit`

() macros conform to ISO/IEC
9899:1999 (“ISO C99”).

The symbols `isinff`

(), and
`isnanf`

() are provided as compatibility aliases to
`isinf`

(), and `isnan`

(),
respectively, and their uses are deprecated. Similarly,
`finite`

() and `finitef`

() are
deprecated versions of `isfinite`

().

## HISTORY

The `fpclassify`

(),
`isfinite`

(), `isinf`

(),
`isnan`

(), `isnormal`

(), and
`signbit`

() macros were added in
OpenBSD 4.4. 3BSD introduced
`isinf`

() and `isnan`

()
functions, which accepted `double` arguments; these have
been superseded by the macros described above.