strdomn.asm

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DSEG          SEGMENT      ;为什么在DOS 中不显示呢?
STRING        DB        'How ARE yOU',0
DSEG          ENDS      
CSEG          SEGMENT
              ASSUME    CS:CSEG ,DS:DSEG
              
START:        MOV       AX,DSEG 
              MOV       DS,AX
              MOV       SI,OFFSET STRING
AGAIN:        MOV       AL,[SI]
              OR        AL,AL
              JZ        OK
              CMP       AL,'A'
              JB        NEXT
              CMP       AL,'Z'
              JA        NEXT
              ADD        AL,20H
              MOV       [SI],AL
NEXT:         ADD       SI,1
              JMP       AGAIN
OK:           MOV       AX,4C00H
              INT       21H
CSEG           ENDS      
                END       START