Question

Computer Architectures
I Just wants a example of the adder and subtraction ckts (circuit) with AND, OR, and NOT gates, and a MUX using 4 bits binary (in logisim or explaination in subtraction and adder). reply asap and thankl you so much

Answer 1

Start with making a diagram of your adder/subtractor in terms of full- and half adders, then translate the FAs and HAs into and/or/not/mux gates.

Answer 2

this is what i got so far but i don't know where to use the FA

Answer 3

You're on your way to the answer already. Good :)

One thing that I don't see in your diagram yet is the carry (well, the carry is there, but it's only used for overflow detection).

SUppose I want to add 7 and 16 (in decimal) I first add 7 and 6, which results in 3 and a carry of 1. I have to 'carry the one' and add that to the 1 of the 16. So the result will be 23.

That carry is where the FA comes in. Where a HA can add two bits and give it's result in two bits, a FA can take three bits (usually two from the operands and one carry bit) and produce a two bit result (one of which will be a carry).

Answer 4

just adding to it - place FA for all input bit pairs except LSB cuz u dont have a carryin as input.

Answer 5

I already found the problem now is working fine