title: How can I create a global variable in Common LISP?
body: <p>I tried using <code>setf</code> in the "toplevel" of my program:</p>
  
  <pre><code>(setf x 17)
  </code></pre>
  
  <p>But SBCL version 1.3.1 gives me an error message:</p>
  
  <pre><code>; in: SETF X
  ;     (SETF X 17)
  ; ==&gt;
  ;   (SETQ X 17)
  ; 
  ; caught WARNING:
  ;   undefined variable: X
  ; 
  ; compilation unit finished
  ;   Undefined variable:
  ;     X
  ;   caught 1 WARNING condition
  </code></pre>
  
  <p>It sounds like I should have declared <code>x</code> somewhere but I don't know how to do that.</p>