\documentclass[fleqn,leqno]{article}
\usepackage{hypertlabook}
\pdftitle{ASCII Text}
\fixverbatim
\begin{popup}
\begin{verbatim*}
--algorithm Clock {
   variable b \in {0, 1}; 
   { while (TRUE) { if (b = 0) b := 1 else b := 0
                  }
   }
 }
\end{verbatim*}
\end{popup}
\makeasciipopup