I have implemented a (very) simple unix operating system using C.  I am
wondering if there is any way that I can write a graphic user interface for
it? What language (if not C) and what libraries or tools should I be looking
at? Also, is there any book teach me how to write gui programs in C?

thanks,
-tc

Sure.  Write a mmap()able device driver for the OS that gives access to
a linear framebuffer.  Write a program to draw stuff on said device.

Straight C/C++ is fine.

Most books of this sort you'd find are likely to be aimed at writing
programs for some specific windowing system... which, unless you've got
X or something running on this, you need to write. :-)

More useful would be a general book on computer graphics; you probably
won't find an appropriate book at your local bookstore (though you
might); try searching amazon.com (or a similar site) for books on
computer graphics.

--
Scott Wood      http://darkflame.ml.org/
"In your case, a few 'find / -uid 1000 rm {} \;' are very healthy
as well... for this newsgroup, I mean..."