bootstrap.inc (2,700 lines) includes functions that are available on EVERY Drupal request.
Here are some highlights :
Constants
- Minimum PHP and MySQL versions, minimum memory
- Logging levels
- Bootstrap phase definitions
- Human language initializations
Functions
- Micro timer functions
- Establish configuration directory
- Initialize Drupal settings (including setup of globals)
- drupal_get_filename (modules, themes etc.)
- Get and set persistent variables
- Page caching mechanism
- Include files thru drupal_load
- Setup HTTP headers. Authenticated users always get 'no-cache' headers
