Determines whether its argument value is normal (neither zero, subnormal, infinite, nor NaN).
int isnormal(real-floating x); (C99)
If the argument is a normal number, a value other than 0 is returned.
If the argument is 0, a subnormal number, infinite, or NaN, 0 is returned.
This macro determines whether its argument value is normal (neither zero, subnormal, infinite, nor NaN).
If a type other than the floating-point type is passed to the argument, correct operation is not guaranteed.