Calculates the yth power of x.
double __far pow(double x, double y);
If x < 0 and y is a non-integer or if x = 0 and y <= 0, pow returns a Not-a-Number (NaN) and sets the macro EDOM for the global variable errno.
If an overflow occurs, pow returns ±∞ and sets the macro ERANGE for errno.
If an underflow occurs, pow returns a denormal number and sets the macro ERANGE for errno.