lines(0); /// set old_style on ; /// @@prerequisite affectations  \sleftarrow{\normalfont switching to old style }
xbasc(); /// @@prerequisite \sleftarrow {\begin{minipage}[t]{6cm}{\nf{}\verb+xbasc+\index{xbasc@\texttt{xbasc}} clears the current graphic window and recorded graphic statements }\end{minipage}}
t=linspace(-20*%pi,20*%pi,2000); 
param3d1(sin(t),t.*cos(t)/max(t),t/100) /// \sleftarrow{\normalfont an \( \R\sp{3}\) curve (Figure~\ref{f:gr1})}\index{param3d1@\texttt{param3d1}}
 xs2ps(0,'fig1'); /// @@prerequisite affectations 
unix(SCI+'/bin/BEpsf fig1'); /// @@prerequisite affectations  /// \sleftarrow{\normalfont calling a Unix script}