HUGE_VAL, _HUGE
#include <math.h>
Remarks
HUGE_VAL is the largest representable double value. This value is returned by many run-time math functions when an error occurs. For some functions, –HUGE_VAL is returned. HUGE_VAL is defined as _HUGE, but run-time math functions return HUGE_VAL. You should also use HUGE_VAL in your code for consistency.