程序代码：

DATA     SEGMENT
         SQ1     DB  23H
         SQ2     DB  '?'
DATA     ENDS
CODE     SEGMENT
ASSUME   CS:CODE,DS:DATA
START:   MOV  AX,DATA
         MOV  DS,AX
         MOV  AL,SQ1
         CMP  AL,0
         JGE  BQ1
         MOV  SQ2,0FFH
         JMP  DONE
BQ1：     JE   BQ2
         MOV  SQ2,1
         JMP  DONE
BQ2       MOV  SQ2,0
DONE:    MOV  AH,4CH
         INT  21H
CODE     ENDS
END      START