help with tags

["Javier Oviedo" <email_joviedo@yahoo.com>]

Hello all:

I want to create some sort of C-project that lets me jump to
function/variable/#define/structure definitions from within c-code. I know
that this must be an incredibly common request.

I've looked at tags in the emacs manual. It says to use etags to accomplish
this. I guess that  I would have to run this on every directory manually and
update it when I modify files.

Is there some utility that will let me automatically create this kind of
tag/project system given some path? Ideally it would support the following
functionality:

1. Given a root dir, it would add all sub-directories(and files within) to
this project.
2. It would auto-update tags tables when/if a file is modified.

I'm not sure if this is asking too much, but please let me know if there is
anything that performs some or all of these features. Thanks in advance!

--
Javier