第十三章答案一

 ;**********************************************
;编写并安装int 7ch中断例程,功能为显示一个用0
;结束的字符串,中断例程安装在0:200处
;**********************************************
assume cs:code

code segment
start:
     mov ax,cs
     mov ds,ax
     mov si,offset display
    
     mov ax,0
     mov es,ax
     mov di,200h
     mov cx,offset displayend-offset display
     cld
     rep movsb
 
     mov ax,0
     mov es,ax
     mov word ptr es:[7ch*4],200h
     mov word ptr es:[7ch*4+2],0
  
  
     mov ax,4c00h
     int 21h
    
 
display:
        push cx
        push ax
 push bx
 push dx
 push bp
 push es
        push di
  
      mov ax,0b800h
      mov es,ax
      mov ah,0
      mov al,dh
      mov bl,160
      mul bl
      mov bp,ax
      mov dh,0
      add dl,dl
      mov di,dx
     
     
     
      mov al,cl
     
    s:
      mov cl,ds:[si]
      mov ch,0
      jcxz next
      mov es:[bp+di],cl
      mov es:[bp+di+1],al
      inc si
      add di,2
      jmp short s
  next:
        pop di
 pop es
 pop bp
 pop dx
 pop bx
 pop ax
        pop cx
        iret
displayend:nop
     

 

code ends
     end start