DATA    SEGMENT
OFF_0   DW       ?                  ;中斷向量偏移地址
SEG_0   DW       ?                  ;中斷向量段地址
MASK_I  DB       ?                  ;系統(tǒng)原始中斷屏蔽字
TN      DB       '0 ' ,'s'                ;延時常數(shù)，已給定，1秒為18次
CONT    db       0
OK      DB  'How are you?$',0DH,0AH
DATA    ENDS
STACK   SEGMENT
        DW  50 DUP(0)
STACK   ENDS
CODE    SEGMENT
        ASSUME  CS:CODE,DS:DATA,SS:stack
start:  MOV     AX,DATA         ;Initial 
        MOV     DS,AX
        MOV     AX,STACK
        MOV     SS,AX             
        MOV     AX,50
        MOV     SP,AX                
       ;取原IR0中斷向量
        MOV     AX,351CH       ;取原中斷向量
        INT     21H
        MOV     SEG_0,ES       ;保存原中斷向量
        MOV     OFF_0,BX
       ;設置新中斷向量
        CLI
        PUSH    DS
        MOV     DX,OFFSET NEWINT
        MOV     AX,SEG NEWINT 
        MOV     DS,AX
        MOV     AH,25H
        MOV     AL,1CH 
        INT     21H
        POP     DS
        STI
        mov     DX,offset OK
        MOV     AH,09H
        INT     21H      
   W1:  MOV     DL,TN
        MOV     AH,2
        INT     21H
        MOV     AH,0BH          ;有鍵按下?
        int      21H
        CMP      AL,00H          ;無鍵按下,轉(zhuǎn)W1,否則,調(diào)用1S延時子程序 
        JZ       W1     
        MOV      AH,08H          ;有鍵,讀鍵值AL
        INT      21H
        CMP      AL,1BH          ;是ESC鍵?
        JNZ      W1             ;是,退出,否,轉(zhuǎn)W1                  
      ;恢復原中斷
            cli
            MOV     DX,OFF_0
            PUSH    DS
            MOV     DS,SEG_0
            MOV     AX,251CH
            INT     21H
            POP     DS
            STI            
            MOV     AX,4C00H              ;返回DOS
            INT     21H             
;----------------------------
        ;新中斷服務程序
     NEWINT    PROC  FAR                   ;新IRQ0中服程序
               PUSH  AX              ;保護現(xiàn)場
               MOV   AX,DATA
               MOV   DS,AX
        ASSUME DS:DATA
               INC    CONT                 ;1/18S,+1
               CMP    CONT,18              ;滿1秒?,否,繼續(xù)累計
               JB     L1
               MOV    CONT,0
               INC    TN
               CMP    TN,'9'
               JBE     L1
               MOV    TN,'0'
      L1:      POP    AX
               IRET
      NEWINT   ENDP
;--------------------------------
   DISP    PROC      NEAR               ;入口:TN=DL=字符
             PUSH    AX 
             MOV     DL,TN
             MOV     AH,02H            ;DOS調(diào)用,顯示一個字符
             INT     21H        
             INC     TN
             CMP     TN,'9'
             JBE      EXIT 
             MOV     TN,'0'
    EXIT:   POP     AX
             RET 
     DISP    ENDP  
    CODE    ENDS
            END START