Write a subroutine cmp in assembly which compares two bytes. Namely, write
a segment of assembly code in the form of:
CMP: ...
...
...
RET
? Assume the two byte to be compared are already stored in register B and
C when the subroutine cmp is called.
? The return value is one of 0, 1, or 2. If the two bytes are equal, then
return 0. If first byte is less than the second, then return 1. Otherwise,
return 2.
? The return value is to be stored in register D.

CMP A,B
JE MOV #0,D
JB MOV #1,D
JA MOV #2,D
RET

CMP: cmp A,B
        JE equal
        JB less
        JA more
equal: MOV #0,D
less: MOV #1,D
more MOV #2,D
        RET

CMP A,B

MOV #0,D

JE MOV #0,D