Thank you, Sinoteq.

Nicely stated.

I guess I understood their function, I just wondered why PicBasic (or whoever) hadn't created the functions in a symmetrical manner. But I guess you have a point in that, they may have tried to make them symmetrical but then "NCD 0001" and "NCD 0000" would have had the same answer (0). So they wouldn't have had a way to indicate when NO bits where set.

More advanced languages allow for -1 as an answer to a function, which might have given them room to make the 2 functions symmetrical.

oh well.
Thanks.

-Andrew