汇编语言——动态显示时间

; 在屏幕的左上角动态显示时间，期间，按下Home键后，能显示“Home”，按下End键后，退出程序。
assume cs:code, ss:stack, ds:data
stack segment stack
     db 128 dup (0)
stack ends
data segment
           dw 0,0
      home db 'Home',0dh,0ah,'$'
data ends
code segment
start:
      mov ax,stack
      mov ss,ax
      mov sp,128
      mov ax,data
      mov ds,ax
 
      ; 改中断例程入口地址
      mov ax,0
      mov es,ax
      push es:[9*4]
      pop ds:[0]
      push es:[9*4+2]
      pop ds:[2]
      mov word ptr es:[9*4],offset int9
      mov es:[9*4+2],cs
 
      ; 显示时间
show: mov al,2    ;分
      out 70h,al
      in al,71h
      mov ah,al
      mov cl,4
      shr ah,cl
      and al,00001111b
      add ah,30h
      add al,30h
      mov bx,0b800h
      mov es,bx
      mov byte ptr es:[0],ah
      mov byte ptr es:[1],01001111b
      mov byte ptr es:[2],al
      mov byte ptr es:[3],01001111b
 
      mov byte ptr es:[4],':'
      mov byte ptr es:[5],01001111b
 
      mov al,0    ;秒
      out 70h,al
      in  al,71h
      mov ah,al
      mov cl,4
      shr ah,cl
      and al,00001111b
      add ah,30h
      add al,30h
      mov bx,0b800h
      mov es,bx
      mov byte ptr es:[6],ah
      mov byte ptr es:[7],01001111b
      mov byte ptr es:[8],al
      mov byte ptr es:[9],01001111b
      jmp show
 
      ; 定义中断例程
int9: push ax
      push bx
      push dx
      push es
      in al,60h
      pushf
      pushf
      pop bx
      and bh,11111100b
      push bx
      popf
      call dword ptr ds:[0]
 
      mov bl, al ;保存al
      cmp al,47h ; 47h是HOME键的扫描码
      jne ifend
      
      ;处理HOME
      lea dx, home
      mov ah,9
      int 21h
      jmp int9ret
 
ifend:
      cmp bl, 4Fh ;4Fh是end键的扫描码
      jne int9ret
      
      ;处理END，使程序结束，注意在此要恢复中断向量
      mov ax,0
      mov es,ax
 
      push ds:[0]
      pop es:[9*4]
      push ds:[2]
      pop es:[9*4+2]
 
      mov ax,4c00h
      int 21h
 
int9ret:
      pop es
      pop dx
      pop bx
      pop ax
      iret
 
code ends
end start