Android continues to lead the market of Smartphones in worldwide. In 2011, the number of Android OS devices sold was about 76 million units in worldwide.
From Android developer website, “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.” . Android has some features as follows: 1) Application framework 2) Dalvik virtual machine 3) Integrated browser 4) Optimized graphics 5) SQLite 6) Media support 7) GSM telephony 8) Bluetooth, EDGE, 3G, and Wi-Fi 9) Camera, GPS, compass, and acceleromenter 10) Rich development environment.
Figure above shows the major component of the Android operating system. All application in Android is written using Java programming language. Underlying all application is a set of services and systems which is also referred as application framework. As we can see from figure 15, it includes activity manager, window manager, content providers, view system, package manager, telephony manager, resource manager, location manager, and notification manager. Android includes a set of C or C++ libraries that is exposed to developers through the Android application framework. Some of the core libraries are 1) Surface manager 2) Media framework 3) SQLite 4) OpenGL ES 5) FreeType 6) WebKit 7) SGL 8) SSL 9) libc. Android includes a set of core libraries and Dalvik virtual machine. Core libraries provide most of the functionality available for java programming language. The
Dalvik virtual machine is register-based, and it executes files in the Dalvik executable format (.dex). It relies on the Linux kernel. The Linux is used for core system services, and the kernel acts as an abstraction layer between the hardware and the software stack.