Here you can
understand two things :
-
How
Android works ?
-
What
are layers in Android OS ?
Figure: Architecture of Android
The Android
OS is roughly divided into five sections in four main layers :
Red Layer :
Linux kernel:- This is the kernel on which Android
is based. This layer contains all the low- level device drivers for the various
hardware components of an Android device.
Green Layer :
Libraries:-
These contain all the code that provides the main features of an Android OS.
For example, the SQLite library provides database support so that an
application can use it for data storage. The WebKit library provides
functionalities for web browsing.
Android runtime:- At the same layer as the libraries,
the Android runtime provides a set of core libraries that enable developers to
write Android apps using the Java programming language. The Android runtime
also includes the Dalvik virtual machine, which enables every Android
application to run in its own process, with its own instance of the Dalvik
virtual machine (Android applications are compiled into the Dalvik
executables). Dalvik is a specialized virtual machine designed specifically for
Android and optimized for battery-powered mobile devices with limited memory
and CPU.
Blue Layer :
Application framework:- Exposes the various capabilities of
the Android OS to application developers so that they can make use of them in
their applications.
Applications:- At this top layer, you will find
applications that ship with the Android device (such as Phone, Contacts,
Browser, etc.), as well as applications that you download and install from the
Android Market. Any applications that you write are located at this layer.
