Switch the logic button at the bottom for Subtraction. ^^ the integers are placed like a normal calculator: 7 8 9
4 5 6
1 2 3
... there is no reset... and I'm new to digital circuits... so I have NO IDEA of memory and so on... Basically ít's a 4 Bit Adder, but one of the inputs is connected to a... these multiplexers but just with 2 inputs. So when the logic switch is switched, the multiplexer output is the other one(the input bút inversed). And ít adds one 'bit' so ít turn into the 2 complement, and the circuit functions as a subtractor. I hope at least someone found it helpful.. xD.
