打表法：

DATA SEGMENT
ASCII DB 30H,31H,32H,33H,34H,35H,36H,37H,38H,39H
      DB 41H,42H,43H,44H,45H,46H
HEX DB 0BH
DATA ENDS
CODE SEGMENT
   ASSUME CS:CODE,DS:DATA
START: MOV AX,DATA
       MOV DS,AX
       MOV BX,OFFSET ASCII
       MOV AL,HEX
       AND AL,0FH
       XLAT
       MOV DL,AL
       MOV AH,2
       INT 21H
       MOV AX,4C00H
       INT 21H
CODE ENDS
     END START

 

直接转换：

DATA SEGMENT
HEX DB 0BH
DATA ENDS
CODE SEGMENT
   ASSUME CS:CODE,DS:DATA
START: MOV AX,DATA
       MOV DS,AX
       MOV DL,HEX
       AND DL,0FH
       OR DL,30H
       CMP DL,39H
       JBE AD1
       ADD DL,7
AD1:   MOV AH,2
       INT 21H
       MOV AX,4C00H
       INT 21H
CODE ENDS
     END START