title: how to make vim show ^M and substitute it
body: <p>my vim show tab as --->, but does not show windows ^M character.</p>
  
  <p>And , how substitute it in vim.</p>
  
  <p>renew ============</p>
  
  <p>I check my vimrc it is  set fileformat=unix
  but when I open a dos file set ff is dos</p>