All of the core features of the device such as telephony, network, and other important functions are started by the system server, as shown in the following screenshot:

The following are some of the core services that get started in this process:

• Start Power Manager
• Create Activity Manager
• Start Telephony Registry
• Start Package Manager
• Set Activity Manager Service as System Process
• Start Context Manager
• Start System Context Providers
• Start Battery Service
• Start Alarm Manager
• Start Sensor Service
• Start Window Manager
• Start Bluetooth Service
• Start Mount Service

The system sends a broadcast action called ACTION_BOOT_COMPLETED, which informs all the dependent processes that the boot process is complete. After this, the device displays the home screen and is ready to interact with the user.

As explained earlier, several manufacturers use Android operating systems on their devices. Most of these device manufacturers customize the OS based on their hardware and other requirements. When a new version of Android is released, these device manufacturers have to port their custom software and tweaks to the latest version.