he editor you you have designated with the "EDITOR" command described
in the reference manual. Modify the lens as you desire and then file
the lens. The program will return from the editor to the CMD
level. Then type:</p>

<p><strong>INPUT ED</strong></p>

<p>Your full screen edit modified lens is now the current lens. This
  is the end of lesson 2.</p>

<h2>Lesson #3 - Paraxial Rays and 3<sup>rd</sup>, 5<sup>th</sup>, and
7<sup>th</sup> Order Aberrations</h2>

<p>To make this lesson easier, turn on full he