## SYNOPSIS

`
#include <math.h>
`

`
double logb(double x)
`

`
float logbf(float x)
`

## DESCRIPTION

The ` logb()` function computes exponent of

*x*, which is the integral part of

`log`, as a signed floating point value, for a non-zero

_{r}|*x*|*x*, where

*r*is the radix of the machine's floating-point arithmetic.

The ` logbf()` is a single-precision version of the

`function.`logb()

## PARAMETERS

## RETURN VALUES

If successful, ` logb()` returns the exponent
of

*x*.

If *x* is `NaN`, `NaN` is returned.

If *x* is 0.0, `-HUGE_VAL` is returned.

## CONFORMANCE

UNIX 98.

## MULTITHREAD SAFETY LEVEL

MT-Safe.

## PORTING ISSUES

None.

## AVAILABILITY

PTC MKS Toolkit for Professional Developers

PTC MKS Toolkit for Enterprise Developers

PTC MKS Toolkit for Enterprise Developers 64-Bit Edition

## SEE ALSO

PTC MKS Toolkit 9.6 Documentation Build 9.