Drupal is a very extensible web platform, and provides many APIs to help you build your application. Conceptual explanations and examples of using the APIs can be found in this part of the handbook, while detailed information about individual functions has its own space:
API Documentation is available from api.drupal.org for:
Drupal uses Doxygen to automatically generate documentation from the latest Drupal sources. This allows us to ensure that documentation is up-to-date and to simultaneously track multiple versions of the documentation.
For guidelines on how to document the code with Doxygen, see Doxygen formatting conventions.
See Your own api.drupal.org site for information on how to set up your own automatically generated API reference site.
Below is a list of API development topics which are discussed in detail.