Android operating system

The Android operating system was designed by the Open Handset Alliance (led primarily by Google) and was developed for Android smartphones and tablet computers. Whereas iOS is designed to run on Apple mobile devices and is close-sourced, Android runs on a variety of mobile platforms and is open-sourced, partly explaining its rapid rise in popularity. The structure of Android appears in Figure.

Android is similar to iOS in that it is a layered stack of software that provides a rich set of frameworks for developing mobile applications. At the bottom of this software, the stack is the Linux kernel, although it has been modified by Google and is currently outside the normal distribution of Linux releases.

Linux is used primarily for process, memory, and device-driver support for hardware and has been expanded to include power management. The Android runtime environment includes a core set of libraries as well as the Dalvik virtual machine. Software designers for Android devices develop applications in the Java language. However, rather than using the standard Java API, Google has designed a separate Android API for Java development. The Java class files are first compiled to Java bytecode and then translated into an executable file that runs on the Dalvik virtual machine. The Dalvik virtual machine was designed for Android and is optimized for mobile devices with limited memory and CPU processing capabilities.

The set of libraries available for Android applications includes frameworks for developing web browsers (WebKit), database support (SQLite), and multi-media. The libc library is similar to the standard C library but is much smaller and has been designed for the slower CPUs that characterize mobile devices.