title: What are the file/group/record/unit separator control characters and their usage?
body: <p>Unicode defines several control characters from ASCII. <a href="http://www.unicode.org/charts/PDF/U0000.pdf" rel="noreferrer">http://www.unicode.org/charts/PDF/U0000.pdf</a></p>
  <p>I see many control characters are widely used but I really don't see where &quot;information separators&quot; are used. (U+001C~U+001F)</p>
  <p>What are they? What's their history? What were they used for?</p>