Drupal6 Updates

Here is the Drupal6 features from Changelog.txt

- New, faster and better menu system.
- New watchdog as a hook functionality.
* New hook_watchdog that can be implemented by any module to route log
messages to various destinations.
* Expands the severity levels from 3 (Error, Warning, Notice) to the 8
levels defined in RFC 3164.
* The watchdog module is now called dblog, and is optional, but enabled by
default in the default install profile.
* Extended the database log module so log messages can be filtered.
* Added syslog module: useful for monitoring large Drupal installations.
- Added optional e-mail notifications when users are approved, blocked, or
deleted.
- Drupal works with error reporting set to E_ALL.
- Added scripts/drupal.sh to execute Drupal code from the command line. Useful
to use Drupal as a framework to build command-line tools.
- Made signature support optional and made it possible to theme signatures.
- Made it possible to filter the URL aliases on the URL alias administration
screen.
- Language system improvements:
* Support for right to left languages.
* Language detection based on parts of the URL.
* Browser based language detection.
* Made it possible to specify a node's language.
* Support for translating posts on the site to different languages.
* Language dependent path aliases.
* Automatically import translations when adding a new language.
* JavaScript interface translation.
* Automatically import a module's translation upon enabling that module.
- Moved "PHP input filter" to a standalone module so it can be deleted for
security reasons.
- Usability:
* Improved handling of teasers in posts.
* Added sticky table headers.
* Check for clean URL support automatically with JavaScript.
* Removed default/settings.php. Instead the installer will create it from
default.settings.php.
* Made it possible to configure your own date formats.
* Remember anonymous comment posters.
* Only allow modules and themes to be enabled that have explicitly been
ported to the correct core API version.
* Can now specify the minimum PHP version required for a module within the
.info file.
* Drupal core no longer requires CREATE TEMPORARY TABLES or LOCK TABLES
database rights.
* Dynamically check password strength and confirmation.
* Refactored poll administration.
* Implemented drag-and-drop positioning for blocks, menu items, taxonomy
vocabularies and terms, forums, profile fields, and input format filters.
- Theme system:
* Added .info files to themes and made it easier to specify regions and
features.
* Added theme registry: modules can directly provide .tpl.php files for
their themes without having to create theme_ functions.
* Used the Garland theme for the installation and maintenance pages.
* Added theme preprocess functions for themes that are templates.
* Added support for themeable functions in JavaScript.
- Refactored update.php to a generic batch API to be able to run time-consuming
operations in multiple subsequent HTTP requests.
- Installer:
* Themed the installer with the Garland theme.
* Added form to provide initial site information during installation.
* Added ability to provide extra installation steps programmatically.
* Made it possible to import interface translations at install time.
- Added the HTML corrector filter:
* Fixes faulty and chopped off HTML in postings.
* Tags are now automatically closed at the end of the teaser.
- Performance:
* Made it easier to conditionally load .include files and split up many core
modules.
* Added a JavaScript aggregator.
* Added block-level caching, improving performance for both authenticated
and anonymous users.
* Made Drupal work correctly when running behind a reverse proxy like
Squid or Pound.
- File handling improvements:
* Entries in the files table are now keyed to a user instead of a node.
* Added reusable validation functions to check for uploaded file sizes,
extensions, and image resolution.
* Added ability to create and remove temporary files during a cron job.
- Forum improvements:
* Any node type may now be posted in a forum.
- Taxonomy improvements:
* Descriptions for terms are now shown on taxonomy/term pages as well
as RSS feeds.
* Added versioning support to categories by associating them with node
revisions.
- Added support for OpenID.
- Added support for triggering configurable actions.
- Added the Update status module to automatically check for available updates
and warn sites if they are missing security updates or newer versions.
Sites deploying from CVS should use http://drupal.org/project/cvs_deploy.
Advanced settings provided by http://drupal.org/project/update_advanced.
- Upgraded the core JavaScript library to jQuery version 1.2.3.
- Added a new Schema API, which provides built-in support for core and
contributed modules to work with databases other than MySQL.
- Removed drupal.module. The functionality lives on as the Site network
contributed module (http://drupal.org/project/site_network).
- Removed old system updates. Updates from Drupal versions prior to 5.x will
require upgrading to 5.x before upgrading to 6.x.

- Better performance because of better caching and the ability to split modules in separate files to reduce memory on runtime
- Improved menu and forms API
- Built-in module update tracker

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HOOKS
Drupal's module system is based on the concept of "hooks". A hook is a PHP function that is named foo_bar(), where "foo" is the name of the module (whose filename is thus foo.module) and "bar" is the name of the hook. Each hook has a defined set of parameters and a specified result type.

To extend Drupal, a module need simply implement a hook. When Drupal wishes to allow intervention from modules, it determines which modules implement a hook and call that hook in all enabled modules that implement it.