title: Is there any character that is never used (in ASCII or Unicode)
body: <p>I just need one character that I can set in character arrays indicating that a particular location or a series of locations are free and available for storing data.</p>
  
  <p>I need this because I am making a simple memory pool and need to reset freed blocks and indicate them as free.</p>
  
  <p>Any help would be appreciated.</p>