title: setq and defvar in Lisp
body: <p>I see that the <a href="http://www.gigamonkeys.com/book/" rel="noreferrer">Practical Common Lisp</a> uses <code>(defvar *db* nil)</code> for setting up a <em>global variable</em>. Isn't it OK to use <code>setq</code> for the same purpose?</p>
  
  <p>What are the advantages/disadvantages of using <code>defvar</code> vs. <code>setq</code>?</p>