There is a difference in how some bits are interpreted to determine status of the arithmetic operation, like overflow. If you don't care about that, you can use excactly the same routine.???????????????????????????????????????????????? Sorry, can someone explain what this means to me please? I can't just add too 16 bit 2's comp values together and get the correct 2's comp answer can I? Thanks Graham _________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu