\section{ISHANDLE Test for Graphics Handle}

\subsection{Usage}

Given a constant, this routine will test to see if the
constant is a valid graphics handle or not.  The syntax
for its use is
\begin{verbatim}
  y = ishandle(h,type)
\end{verbatim}
and returns a logical \verb|1| if \verb|x| is a handle of type \verb|type|
and a logical \verb|0| if not.  
