fabs
and fabsf
calculate 
x,
the absolute value (magnitude) of the argument, x,
by direct manipulation of the bit representation of x.
fabs,
fabsf
[absolute value
(magnitude)]
SYNOPSIS
#include <math.h>
double fabs(double x);
float fabsf(float x);
DESCRIPTION
fabs
and fabsf
calculate x,
the absolute value (magnitude) of the argument, x,
by direct manipulation of the bit representation of x.
RETURNS
The calculated value is returned.
No errors are detected.
COMPLIANCE
fabs
is ANSI. fabsf
is an extension.