怎么把这个程序变成2个2位数相加的程序啊

DATA SEGMENT
BUF DB 3,?,3 DUP(?)
ORG 10H
BUF1 DB ?,?,'$'
DATA ENDS
CODE SEGMENT
ASSUME CS:CODE,DS:DATA
START:
MOV AX,DATA
MOV DS,AX
MOV DX,OFFSET BUF
MOV AH,0AH
INT 21H
MOV SI,OFFSET BUF
MOV AX,[SI+2]
SUB AX,3030H
ADD AL,AH
DAA
MOV BL,AL
AND AL,0FH
ADD AL,30H
MOV SI,OFFSET BUF1
MOV [SI+1],AL
AND BL,0F0H
MOV CL,4
SAR BL,CL
ADD BL,30H
MOV [SI],BL
MOV DX,OFFSET BUF1
MOV AH,9
INT 21H
MOV AH,4CH
INT 21H
CODE ENDS
END START