htod1.asm

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 DSEG  SEGMENT
   XX  DB 4
   YY  DB ?
 DSEG  ENDS
 CSEG  SEGMENT
        ASSUME CS:CSEG ,DS:DSEG
 START:MOV AX,DSEG
       MOV DS,AX
       MOV AL,XX
       AND AL,0FH
       CMP AL,9
       JA  LAB1	
       ADD AL,30H
       JMP LAB2
 LAB1: ADD AL,37H
 LAB2: MOV YY,AL
       MOV AH,4CH
       INT 21H
CSEG   ENDS
       END START