math.h

The math.h header file contains macro declarations for use with floating-point support:

No feature test macro is required.

Object-like Macros: The definitions are as follows.
HUGE_VAL
A very large positive number that expands to a double expression.
HUGE_VALF
A very large positive number that expands to a float expression.
HUGE_VALL
A very large positive number that expands to a long double expression.
INFINITY
A constant expression of type float representing positive infinity.
NAN
A constant expression of type float representing a quiet NaN.