Here is a 4bit ripple carry adder only using 'and', 'xor', 'nand' and 'not' gates. There is a full-adder in every layer. This full-adders are constructed by two half-adders. And these half-adders are made by an 'and'-gate and a 'xor'-gate. The half-adders are connected by an 'or'-gate. The 'or'-gate...