# _logb

Visual Studio 2008

Extracts an exponential value of a double-precision floating-point argument.

```double _logb(
double x
);
```

## Parameters

x

Double-precision floating-point value.

## Return Value

_logb returns the unbiased exponential value of x.

## Remarks

The _logb function extracts the exponential value of its double-precision floating-point argument x, as though x were represented with infinite range. If the argument x is denormalized, it is treated as if it were normalized.

Input

SEH exception

Matherr exception

± QNAN,IND

None

_DOMAIN

± 0

ZERODIVIDE

_SING

## Requirements

Routine

_logb

<float.h>

For more compatibility information, see Compatibility in the Introduction.

### Libraries

All versions of the C run-time libraries.

## .NET Framework Equivalent

Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.