It can multiply, add, and subtract 4 bit numbers and display the answer on a 7 segment display. The first thing that happens is the encoder. It takes the decimal number and puts it into binary. The binary number or then goes to a separator which will send it to either add, subtract, or multiply. The adder will take the 2 numbers, and add them, digit by digit. If there is 2 of the same digit, it sends it up a digit. The subtractor will subtract numbers by inverting the subtracted number, and then adding them together, and then inverting the result. The multiplier will multiply each digit of the binary number by each digit of the other binary number and produce four binary numbers. It then adds those together to get the final result. Each operation is decoded and then separated into digits. This is so all the tens digits go to the tens 7 seg and the ones go to the ones 7 seg.
Each lever represents a number. When subtracting, its the top minus the bottom. Flip which lever you would like to add/subtract/multiply,
Wait a couple seconds and your answer will be on the 7 seg boards