Note: If you're using Drupal 7, see Module Development for Drupal 7 or search using the Drupal 7 filter.
The various APIs and subsystems outlined below are critical systems and in most cases you'll need to know how some or all of these work in order to make use of Drupal's higher level developer APIs. This series is a collection of all of our Drupal Module Development tutorials - essential information for anyone developing Drupal modules or working on Drupal core.
