Graphics in DOS

[William Echard <WECHARD@VM2.YorkU.CA>]

     I'm a musicology grad student, and I'm experimenting with representing
and manipulating phrase-structres as trees in Lisp.  I want to write a
program to display the trees on the screen, and I would prefer to do it in
graphics mode.  Right now I'm limited to using Clisp under DOS, in text mode
only.  Are there extensions that I can get that will make it fairly easy to
switch into graphics mode and draw on the screen?  I could write something in
another language, but I'd like to try and do it all in Lisp if possible.
     Also, if anyone has code for parsing, analyzing, comparing, displaying,
or doing anything else to trees that will work under Clisp, I'd like to know
about it.  Thanks in advance----William