You typed <br>
<font color=green> plot '< henon -B0 -Aa -l5000 | delay' with
dots</font><br>
in gnuplot and see nothing? <br>
a)  You followed the instruction too literally
and forgot to replace <font color=green> a</font> in <font
color=green> -Aa</font> by a real number between 0 and 2. <br>
b) You have chosen an inappropriate value for <font color=green>
a</font>: either outside the interval [0,2] or one for which the
trajectory settles down on a fixed point, which you overlooked in your
plot.<br>
c) If you plotted something else before, you perhaps adjusted by hand
a range for x or y outside the range of the Henon data. Use 
<font color=green>set autoscale</font> to undo this setting.