The document describes three designs for a reversible 8-bit parallel binary adder/subtractor circuit. Design I uses F and FG reversible gates, with a quantum cost of 12 for the half adder/subtractor and 21 for the full adder/subtractor. Design II uses FG and TR gates for the half adder/subtractor with a cost of 8, and TR and FG gates for the full adder/subtractor. Design III is proposed to be more efficient but is not described. The performance of the different designs is analyzed based on the number of gates, garbage inputs/outputs, and quantum cost.