isnormal —
test for normal value
Standard C Library (libc, -lc)
#include <math.h>
int
  
  isnormal(real-floating
    x);
The isnormal() macro determines whether its argument
  x has a normal value. An argument represented in a
  format wider than its semantic type is converted to its semantic type first.
  The determination is then based on the type of the argument.
It is determined whether the value of x is normal, and
  neither zero, subnormal, infinite nor NaN.
It is determined whether the value of x is finite, and
  neither true zero, dirty zero nor ROP.
The isnormal() macro returns a non-zero value if the
  value of x is finite. Otherwise 0 is returned.
The isnormal() macro conforms to
  ISO/IEC 9899:1999 (“ISO C99”).