ons</h4>

    A "LOOP" form of iteration repeatedly executes its component
    statement sequence.  The only way to exit a "LOOP" is using an
    exit statement or return statement.<p>

      An iteration of the form

<pre>
WHILE <em>e</em> DO <em>s</em> END
</pre>

    is identical in meaning to the iteration

<pre>
LOOP IF ~ <em>e</em> THEN EXIT END; <em>s</em> END
</pre>

    An iteration of the form

<pre>
FOR <em>id</em> := <em>e1</em> TO <em>e2</em> DO <em>s</em> END
</pre>

    requires that <em>id</