The ALU is a 4-bit ripple-carry adder/subtractor, with plans for a comparison unit that will be responsible for JMP.

[Phillip] wanted to play with the C preprocessor. He decided to do that by creating a 4 bit full adder. We know this is pretty useless in everyday life, but it was a great learning experience. The … ...

This paper focuses on the implementation and simulation of 4-bit, 8-bit and 16-bit carry look-ahead adder based on Verilog code and compared for their performance in Xilinx.

Using the reconfigurable logic of multi-input floating gate MOSFETs, 4-bit full adder has been designed for 1.1V operation.