Arithmetic, iii


Subtraction: X - Y is the same as X + (-Y)

We have to resolve incorrect answers again by monitoring overflow


  0000 0010 -    002
  1111 1111        1
  _________      ___

 10000 0001        1 


  1111 1111 -    255
  0000 0010      254
  _________      ___

 10000 0001        1


  0000 0001 -      1
  1111 1110        2
  _________      ___

0 1111 1111       -1



  1111 1110 -    254
  0000 0001      255
  _________      ___

0 1111 1111       -1