Wondering how Drupal manages hooks outside of the core in modules. Seems like parsing the code in modules would add a lot of overhead, and that it's more likely that the code is doing something else to manage the calls; for example, indexing or compiling the code when Drupal boots for the first time.
If there's a difference between how 6 and 7 handles this, please explain how each handles it, or clearly state which version you've explained.