To design, build and verify binary adder circuits using logic gates and full adder blocks:

• a 1-bit half adder using an XOR gate and an AND gate,
• a 1-bit full adder using XOR, AND and OR gates,
• a 4-bit ripple carry adder by cascading four 1-bit full adders, and
• a 4-bit adder-subtractor by combining four full adders with XOR gates to perform subtraction using the 2's complement method,

and to verify the working of each circuit by simulating it and comparing its outputs with the expected truth table.