Header File 

float.h 

Category 

Math Routines 

Prototype 

double _logb(double d); 

long double _logbl(long double ld); 

Description 

Extracts the exponential value of a double-precision floating-point argument. If the argument is denormalized, it is treated as if it were normalized. 

_logbl is the long double version; it takes a long double argument and returns a long double result. 

Return Value 

Returns the unbiased exponent of the value passed in. 

Portability