The circuit is a dual-function half adder and half subtractor.
AgMd = Augend/Minuend Input
AdSd = Addend/Subtrahend Input
COh = (Half Adder) Carry Output
SUMhDIFh = (Half Adder) Sum / (Half Subtractor) Difference Output
BOh = (Half Subtractor) Borrow Output
The result of adding the values at AgMd (treated as augend) and AdSd (treated as addend) can be obtained from SUMhDIFh (treated as half adder sum) and COh (half adder carry output) pair.
The result of subtracting the values at AgMd (treated as minuend) and AdSd (treated as subtrahend) can be obtained from SUMhDIFh (treated as half subtractor difference) and BOh (half subtractor borrow output) pair.
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