rn as much as you should from this
lesson. After each <strong>DRAW</strong> command, additional beams may
be traced and drawn on the same plots.</p>

<h2>Lesson #13 - NSS (non-sequential systems)</h2>

<p>From the program main CMD level, type <strong>NSSREST</strong>
which will retrieve a simple non-sequential system stored in the
NSSDIR sub-directory and named TEST.NSS. Typing
<strong>NSSTRACE</strong> will trace a single ray through the
system. Typing:</p>

<p><strong>
    PLOT NEW<br>
    PLOT LOOK , 1 ,