3 D F 6
         -  2 5 9 A   (10+6-A)h = (16+6-10)d = 12d = Ch
(-borrow) 0 0 0 1     (   F-9-1)h = (15-9-1)d = 5d = 5h
         __________   (   D-5)h = (13-5)d = 8d = 8h
            1 8 5 C
Zero:off
Carry:off
Sign:off (1(h)= 0001(b))
Overflow:off (subtracting 2 positives; always OK)



            8 C 0 B
          - B 8 E 7
(-borrow) 1 0 1 0 
          _________
            D 3 2 4
Zero:off
Carry:on
Sign:on
Overflow:off (subtracting 2 negatives; always OK)




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