title: Unix: what modifier key does "M-" refer to (e.g. M-C)
body: <p>I'm trying to do a case-sensitive search in Nano.  The help menu at the bottom of the screen says I can toggle case-sensitivity by typing <code>M-C</code>.</p>
  
  <pre><code>^G Get Help         ^Y First Line       ^T Go To Line       ^W Beg of Par       M-J FullJstify      M-B Backwards
  ^C Cancel           ^V Last Line        ^R Replace          ^O End of Par       M-C Case Sens       M-R Regexp
  </code></pre>
  
  <p>I'm not sure how to do this.  Does <code>M-</code> refer to a modifier key that should be held while I type <code>C</code>?  Or does <code>M-</code> mean I should press some key or key combination before hitting <code>C</code>?  </p>