STACK     SEGMENT     PARA STACK
          DW          100 DUP(?)
STACK     ENDS

DATA      SEGMENT     PARA
BUFF      DB          "12345",00H                        ;長度未知的字符串
DATA      ENDS

CODE      SEGMENT
          ASSUME      CS:CODE, DS:DATA, ES:DATA, SS:STACK
          
MAIN      PROC   FAR
          MOV    AX,STACK
          MOV    SS,AX
          MOV    AX,DATA
          MOV    DS,AX
          MOV    ES,AX
          
          MOV    SI,OFFSET BUFF                         ;字符串原始地址
          MOV    BX,0
          MOV    AL,00H
          
L1:       CMP    [SI][BX],AL
          JZ     L2
          INC    BX                                     ;BX存放偏移位
          JMP    L1
          
L2:       MOV    DI,OFFSET BUFF
          ADD    DI,4
          
L3:       MOV    AL,[SI][BX]                            ;后移4字節(jié)
          MOV    [DI][BX],AL
          DEC    BX
          JNZ    L3
          MOV    AL,[SI][BX]
          MOV    [DI][BX],AL
          
EXIT:   	MOV		AX,4C00H
          INT		21H
MAIN      ENDP
CODE      ENDS
          END     MAIN