Adding to previous post....
There are some advantages to the sequence
of...

  MOV  A, R4
  CLR  C
  SUBB A, R5

..because you can follow it with any one
of the following jump styles to test
for the comditions like I show to the
right...

  JNZ  SomePlace     ; jump for R4 != R5
 or
  JZ   SomePlace     ; jump for R4 == R5
 or
  JC   SomePlace     ; jump for R4 < R5
 or 
  JNC  SomePlace     ; jump for R4 >= R5

Hope this helps
Mike Karas