Linux Kernel:
Android
relies on Linux version 2.6 for core system services such as security, memory
management, process management, network stack, and driver model. The kernel
also acts as an abstraction layer between the hardware and the rest of the
software stack.
Android Runtime:
Android includes a set of core libraries that
provides most of the functionality available in the core libraries of the Java
programming language.
Every Android application runs in its own
process, with its own instance of the Dalvik virtual machine. Dalvik has been
written so that a device can run multiple VMs efficiently. The Dalvik VM
executes files in the Dalvik Executable (.dex) format which is optimized for
minimal memory footprint. The VM is register-based, and runs classes compiled
by a Java language compiler that have been transformed into the .dex format by
the included "dx" tool.
The Dalvik VM relies on the Linux kernel for
underlying functionality such as threading and low-level memory management.
Libraries:
Android includes a set of C/C++ libraries used
by various components of the Android system. These capabilities are exposed to
developers through the Android application framework. Some of the core
libraries are listed below:
· Free Type: This library supports bitmap and vector font rendering.
· Libc:
This library is a BSD-derived implementation of standard c system library,
tuned for embedded linux-based devices.
· LibWebCare:
This library offers a modern and fast web browser engine that powers the
Android browser and an embedded web view . Its based on WebKit and is also used
by the Google Chrome and Apple Safari browsers.
· Media Framework:
These libraries ,which are based on packet video’s OpenCORE , support the
playback and recording of many popular
audio and video formats, as well as working with static image files.
· OpenGL/ES:
These 3D Graphics libraries provide an OpenGL implementation based on OpenGL/ES
1.0 APIs.
· SGL:
This library provides the underlying 2D Graphics engine.
· SQLite:
This library provides a powerful and lightweight relational database engine
that’s available for all app’s and also used by Mozilla Firefox and Apple’s
iPhone for persistent storage.
· SSL: This library provides secure
sockets layer-based (SSL-based) security for network communication.
· Surface Manager: This
library manages access to the display subsystem , and seamlessly composites 2D
and 3D graphic layers from multiple apps.
Application Framework:
By providing an open development platform,
Android offers developers the ability to build extremely rich and innovative
applications. Developers are free to take advantage of the device hardware,
access location information, run background services, set alarms, add
notifications to the status bar, and much, much more.Developers have full
access to the same framework APIs used by the core applications. The
application architecture is designed to simplify the reuse of components; any
application can publish its capabilities and any other application may then
make use of those capabilities (subject to security constraints enforced by the
framework). This same mechanism allows components to be replaced by the user.
Underlying all applications is a set of
services and systems, including:
·
A rich and extensible
set of Views that can be used to
build an application, including lists, grids, text boxes, buttons, and even an
embeddable web browser
·
Content Providers that
enable applications to access data from other applications (such as Contacts),
or to share their own data
·
A Resource Manager, providing access to non-code resources such as localized
strings, graphics, and layout files
·
An Activity Manager that
manages the lifecycle of applications and provides a common navigation
backstack
Applications:
Android
will ship with a set of core applications including an email client, SMS
program, calendar, maps, browser, contacts, and others. All applications are written
using the Java programming language.
where its display
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