bootstrap.inc in core/includes/bootstrap.inc

Functions that need to be loaded on every Backdrop request.

drupal.inc in core/includes/drupal.inc

Contains constants and function wrappers for Drupal 7.x compatibility.

hook_requirements in core/modules/system/system.api.php

Check installation requirements and do status reporting.

install_profile_info in core/includes/install.inc

Retrieves information about an installation profile from its .info file.

system_requirements in core/modules/system/system.install

Implements hook_requirements().

update_module_add_to_system in core/includes/update.inc

Adds modules to the system table in a Backdrop core update.

_system_rebuild_module_data in core/modules/system/system.module

Helper function to scan and collect module .info data.

_system_rebuild_theme_data in core/modules/system/system.module

Helper function to scan and collect theme .info data and their engines.