Chuck F. wrote
Oh. That would be silly.
Indeed (though there will always be plenty of believers in silver
bullets). However, Doxygen will serve as a decent source browser
when run against unannotated source; some people find that useful,
though it has little to do with creating documentation.
I find doxygen (and similar tools) to be handy for developing
"man page" type documentation for specific functions, most
usefully with library interfaces.
More generally, source code annotation - except perhaps at the
literate-programming fringe - seems inherently better suited to
producing reference material than introductions, guides, and the
like; it inevitably incorporates some of the structure of the code.
(Literate programming only avoids this problem, if it does at all,
by subordinating the structure of the code to that of the document;
it's debatable whether that's a better trade-off.)
But Doxygen isn't limited to generating documentation from annotated
source code; it can incorporate documentation from separate files,
and there's no reason why you can't use it to prepare non-reference
documentation.
Doxygen is a documentation-preparation system that can derive some
information from source code - no more and no less.
