finding the source codes in order to learn to program

I just installed ubuntu on my PC, and now I wish to browse into some code. As a starting point I wana see the GLCells screen saver source code

How/where can i find the source code of the GLCells. In general, how can i find the source code开发者_Go百科s of the ubuntul OS distribution?

sudo apt-get build-dep xscreensaver  # Install the libraries and the tools needed
apt-get source xscreensaver          # Download the sources
cd xscreensaver-5.10
(make changes to code)
dpkg-buildpackage -rfakeroot         # Build a .deb
sudo gdebi ../xscreensaver*.deb      # Install the package

To avoid having to do a full recompile after every change, follow the instructions here: http://www.debian.org/doc/maint-guide/ch-build.en.html

GLCells is bundled with XScreenSaver, the source can be downloaded here:

http://www.jwz.org/xscreensaver/download.html

The Ubuntu source CD in ISO format is here (complete with CD Burning Guide):

http://cdimages.ubuntu.com/releases/9.10/release/source/

How about the ubuntu repository?