What is Android?
Android is a software stack for mobile devices that includes an operating system, middleware and key applications. The Android SDK provides the tools and APIs necessary to begin developing applications on the Android platform using the Java programming language.
* Application framework enabling reuse and replacement of components
* Dalvik virtual machine optimized for mobile devices
* Integrated browser based on the open source WebKit engine
* Optimized graphics powered by a custom 2D graphics library; 3D graphics based on the OpenGL ES 1.0 specification (hardware acceleration optional)
* SQLite for structured data storage
* Media support for common audio, video, and still image formats (MPEG4, H.264, MP3, AAC, AMR, JPG, PNG, GIF)
* GSM Telephony (hardware dependent)
* Bluetooth, EDGE, 3G, and WiFi (hardware dependent)
* Camera, GPS, compass, and accelerometer (hardware dependent)
* Rich development environment including a device emulator, tools for debugging, memory and performance profiling, and a plugin for the Eclipse IDE
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.
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.
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:
* System C library - a BSD-derived implementation of the standard C system library (libc), tuned for embedded Linux-based devices
* Media Libraries - based on PacketVideo's OpenCORE; the libraries support playback and recording of many popular audio and video formats, as well as static image files, including MPEG4, H.264, MP3, AAC, AMR, JPG, and PNG
* Surface Manager - manages access to the display subsystem and seamlessly composites 2D and 3D graphic layers from multiple applications
* LibWebCore - a modern web browser engine which powers both the Android browser and an embeddable web view
* SGL - the underlying 2D graphics engine
* 3D libraries - an implementation based on OpenGL ES 1.0 APIs; the libraries use either hardware 3D acceleration (where available) or the included, highly optimized 3D software rasterizer
* FreeType - bitmap and vector font rendering
* SQLite - a powerful and lightweight relational database engine available to all applications
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.
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.