title: What does it really mean that a programming language is stackless?
body: <p>According to this answer </p>
  
  <p><a href="https://stackoverflow.com/questions/551950/what-stackless-programming-languages-are-available/671296#671296">https://stackoverflow.com/questions/551950/what-stackless-programming-languages-are-available/671296#671296</a></p>
  
  <p>all of these programming languages are stackless</p>
  
  <ul>
  <li>Stackless Python</li>
  <li>PyPy</li>
  <li>Lisp</li>
  <li>Scheme</li>
  <li>Tcl</li>
  <li>Lua</li>
  <li>Parrot VM</li>
  </ul>
  
  <p>What does it really mean for them to be stackless? Does it mean they don't use a call stack? If they don't use a call stack, what do they use?</p>