The xfig program is a popular, public-domain (i.e. freely copyable)
drawing program, intended to be similar to Mac Draw.  Following is
a very brief introduction on how to use it:

invocation:

   xfig [filename.fig]

drawing segmented lines:

   click on the segmented-line icon at the left edge of the xfig
   window

   draw your line, clicking the left mouse button at each corner,
   and when done, click the middle mouse button to "save" the line

drawing circles, etc.:

   click on the appropriate icon, then draw

writing text:

   click on the "T" icon, position the mouse where you want the
   text, and then type the text

saving your picture to a .fig file"

   click on File and then use the dialog box which pops up

saving your picture to an Encapsulated Postscript file (good for LaTeX):

   click on Export, and then use the dialog box (note the choice
   of Landscape vs. Portrait orientation)

creating complex objects:

   you can "glue" several individual objects into one complex one
   (good for copying, etc.):

   click on the icon consisting of S, T, a rectangle and an oval,
   all surrounded by a dark rectangular box

   click the left mouse button on a small rectangle marking each
   object to be glued

   click the right mouse button

   you will now see little rectangles marking the overall boundaries
   of the glued object; use one of these when moving, copying or
   deleting

moving/copying/deleting objects:


   click on the corresponding icon