| Name | Description |
|---|---|
| Database abstraction layer | Allow the use of different database servers using the same code base. |
| File interface | Common file handling functions. |
| Form generation | Functions to enable output of HTML forms and form elements. |
| Formatting | Functions to format numbers, strings, dates, etc. |
| Hooks | Allow modules to interact with the Drupal core. |
| Input validation | Functions to validate user input. |
| Menu system | Define the navigation menus, and route page requests to code based on URLs. |
| Node access rights | The node access system determines who can do what to which nodes. |
| Search interface | The Drupal search interface manages a global search mechanism. |
| Themeable functions | Functions that display HTML, and which can be customized by themes. |
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