This is my 8 Bit calculator that I made with just redstone. It works by taking an input and bringing over to the RAM modules that store the data even if you unpower one of the inputs. The adders and subtracters take the input and do the calculations. It outputs an 8 bit binary number which gets sent to the binary to BCD converter where is it converted to BCD. That output then travels to the display which displays the answer to your problem. ***IMPORTANT*** subtraction does not work in this version of the calculator but i am not going to fix it because i have moved on to other projects