Hi,
Since PBP doesn't do floating point math the SIN operator returns a value between 0 and 255 representing -1 to +1 in two's complement.
From the manual:
SIN returns the 8-bit sine of a value. The result is in two's complement form (i.e. -127 to 127). It uses a quarter-wave lookup table to find the result. Sine starts with a value in binary radians, 0 to 255, as opposed to the usual 0 to 359 degrees
HTH
/Henrik.