Drupal's major subsystems
In the previous section we took a birds-eye view of Drupal's architecture. Now we are going to refine our perspective a bit. We are going to walk through the major subsystems that Drupal 7 has to offer.
The responsibility of theming a given piece of data is spread out over the Drupal core, the modules, and the applied theme itself. While we don't modify the Drupal core code, it is important for developers to be able to understand that both module code and theme code can manipulate the look and feel of data.
In this book, ...