I'm making an ARAY/FILT based computer, but I need a design for an adder/subtractor and for multiplier/divider.  Forgive me, but I'm a noob at this stuff.  I promise I'll give credit.  Here's what I have so far:

I have looked, but finding ones the are 1 byte, compatible with my counter, and easy to reverse engineer is harder than I thought.

I've built a 1 byte adder/subtractor based on logic gate and module diagrams I found on the internet.  But I'm unsure how to make it subtract.

EDIT:  Nevermind, I cancelled the project because no one would help me.  I guess I was in over my head.