1)用键盘输入文件名,若输入的字符串为空,则程序运行结束;
2)若输入的文件名存在,则显示内容,否则,显示文件不存在的信息;
.model samll
.stack 256
.data
  fname db 30,?,30 dup(?),0
  fail db "no find",10,13,"$"
  buff db 128 dup(?)
.code
  .startup
again:
      mov ah,0ah
      lea dx,fname
      int 21h
      mov bl,fname+1
      cmp bl,0
      jz over
      xor bh,bh
      mov fname[bx+1],0
      mov dx,offset fname+2
      mov al,0h
      mov ah,3dh
      int 21h
      jnc succ
      lea dx,fail
      mov ah,09h
      int 21h
      jmp again
succ:
     mov bx,ax
read:
     lea dx,buff
     mov cx,128
     mov ah,3fh
     int 21h
     cmp ax,0
     jz close
     jc close
     push bx
     mov dx,ofset buff
     mov cx,ax
     mov bx,1
     mov ah,40h
     int 21h
     pop bx
     jmp read
close:
      mov ah,3eh
      int 21h
      jmp again
over:
     .exit 0
     end

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