 - alphanumeric characters</li>
<li><tt>alpha</tt> - alphabetic characters</li>
<li><tt>blank</tt> - blank characters</li>
<li><tt>cntrl</tt> - control characters</li>
<li><tt>digit</tt> - decimal digits (0 through 9)</li>
<li><tt>graph</tt> - all printable characters except space</li>
<li><tt>lower</tt> - lower-case letters</li>
<li><tt>print</tt> - printable characters including space</li>
<li><tt>punct</tt> - printable characters not space or alphanumeric</li>
<li><tt>space</tt> - white-space characters<