汇编语言编程题，急！

        CODE  SEGMENT
              ASSUME    CS:CODE
              ORG       100H
      START:
         @0:
              MOV       AH,1
              INT       21H
              CMP       AL,'1'
              JB        @0
              CMP       AL,'9'
              JA        @0
              AND       AL,0FH
              MOV       CL,AL
              XOR       CH,CH
         @1:
              MOV       AH,2
              MOV       DL,7
              INT       21H
              LOOP      @1
              JMP       @0
              MOV       AH,4CH
              INT       21H
        CODE  ENDS
              END       START