isnan, isnanf, isinf, isinff, finite, finitef
[test for exceptional numbers]

SYNOPSIS
#include <ieeefp.h> 
int isnan(double arg); 
int isinf(double arg); 
int finite(double arg); 
int isnanf(float arg); 
int isinff(float arg); 
int finitef(float arg);

DESCRIPTION
These functions provide information on the floating point argument supplied.

The following are five major number formats.

• zero

A number which contains all zero bits.
• subnormal

Used to represent number with a zero exponent, but a non-zero fraction.
• normal

A number with an exponent, and a fraction.
• infinity

A number with an all 1’s exponent and a zero fraction.
• NAN

A number with an all 1’s exponent and a non-zero fraction.

isinf returns 1 if the argument is infinity.

finite returns 1 if the argument is zero, subnormal or normal.

The isnanf, isinff and finitef perform the same operations as their isnan, isinf and finite counterparts, but on single precision floating point numbers.