16-bit comparisons

Doing comparisons on extended precision values is about the same as doing them on 8-bit values, but you have to have the value you test in memory, since it won't fit in the accumulator all at once. You don't have to store the values back anywhere, either, since all you care about is the final state of the flags. For example, here's a signed comparison, branching to label if the value in $C100-1 is less than 1000 ($03E8):

  SEC
  LDA $C100
  SBC #$E8
  LDA $C101    ; We only need the carry bit from that subtract
  SBC #$03
  BMI label

All the commentary on signed and unsigned compares holds for 16-bit (or higher) integers just as it does for the 8-bit ones.