\documentclass{article}
%\usepackage{graphpap}
\begin{document}

\section{Basic}
Math: $a=b$
\begin{picture}(100,100)
\put(0,0){\line(1,0){100}}
\end{picture}
%\end{document}

\section{Pictures}
\paragraph{Lines:} using integers, scaling with floats, \LaTeX counters, TeX counters.
All should be the same.
\par
\begin{picture}(100,100)
\put(0,0){\line(1,0){100}}
\put(0,0){\line(1,1){50}}
\put(0,0){\line(0,1){100}}
\end{picture}
{\unitlength=100pt\relax
\begin{picture}(1.0,1.0)
\put(0,0){\line(1,0){1.0}}
\put(0,0){\line(1,1){0.5}}
\put(0,0){\line(0,1){1.0}}
\end{picture}
}

\newcounter{foo}
\setcounter{foo}{50}
\begin{picture}(100,100)
\put(0,0){\line(1,0){100}}
%\put(0,0){\line(1,1){100}}
\put(0,0){\line(1,1){\value{foo}}}
\put(0,0){\line(0,1){100}}
\end{picture}
\newcount\ffoo\ffoo=50\relax
\begin{picture}(100,100)
\put(0,0){\line(1,0){100}}
%\put(0,0){\line(1,1){100}}
\put(0,0){\line(1,1){\ffoo}}
\put(0,0){\line(0,1){100}}
\end{picture}
%\end{document}

\paragraph{Vectors:}
\begin{picture}(100,100)(-100,-100)
\put(0,0){\vector(-1, 0){100}}
\put(0,0){\vector(-1,-1){100}}
\put(0,0){\vector( 0,-1){100}}
\end{picture}

\paragraph{Boxes;}
\begin{picture}(100,100)
\put(0,0){\bf A}
\put(15,15){\framebox(15,15){A}}
\put(30,30){\framebox(15,15){\bf A}}
\put(45,45){\framebox(15,15){A}}
\put(60,20){\frame{\shortstack{A\\B\\\bf C\\D}}}
\put(75,20){\framebox(15,80){\shortstack{A\\\bf B\\C\\D}}}
\end{picture}

\paragraph{Circles:}
\begin{picture}(100,100)
\put(30,30){\circle{30}\vector(0,1){15}\circle*{5}}
\put(70,70){\oval(60,30)}
\end{picture}

\vskip 1em

\paragraph{Curves:}
\begin{picture}(100,100)
\qbezier(40,80)(80,120)(100,80)
\qbezier[50](40,89)(80,129)(100,89)
\end{picture}

\paragraph{Repeats:}
\begin{picture}(100,100)
\multiput(0,0)(10,10){11}{a}
\end{picture}

\begin{picture}(100,100)
\put(10,10){\circle{5}}
\put(20,20){\framebox(10,10){\circle{5}}}
\put(30,30){\framebox(10,10)[l]{\circle{5}}}
\put(40,40){\framebox(10,10)[r]{\circle{5}}}
\put(50,50){\framebox(10,10)[t]{\circle{5}}}
\put(60,60){\framebox(10,10)[b]{\circle{5}}}
\end{picture}

\end{document}