Heads up : the simulation will surely be slow!
I slightly modified my Hexadecimal Addition Calculator so that it does substractions instead!
The leftmost number is A and next to it is B. The result will be A-B.
Note that it also works for negative answers. When an hexadecimal number is negative, the leftmost 7 segment display at the top will be 'F'.
Exemple :
0A (10) - 0F (15) = FB (-5)
This is what is known as "signed" numbers.
You can see in detail how to make a bitwise substraction here : http://everycircuit.com/circuit/5128571346223104
