procedure TForm2.Button4Click(Sender: TObject);
var
  FS:TFileStream;
  Ch:Char;
begin
  FS:=TFileStream.Create('D:\test.txt',fmOpenReadWrite);
  try
    while FS.Position    
久病成良医--多试
千人之诺诺,不如一士之谔谔--兼听