Android is a Linux-based operatingsystem designed primarilyfor touchscreen mobile devices suchas smartphones and tablet computers.
Android is open source and Google releases thecode under the Apache License. This opensource code and permissive licensing allows thesoftware to be freely modified and distributedby device manufacturers, wireless carriers andenthusiast developers.
Androids user interface is based on directmanipulation, using touch inputs thatloosely correspond to real-world actions, likeswiping, tapping, pinching and reversepinching to manipulate on-screen objects.
Android devices boot to the homescreen, theprimary navigation and information point onthe device, which is similar tothe desktop found on PCs.
Android homescreens are typically made up ofapp icons and widgets; app icons launch theassociated app, whereas widgets display live,auto-updating content such as the weatherforecast, the users email inbox, or a newsticker directly on the homescreen.
Android is developed in private by Google until thelatest changes and updates are ready to be released, atwhich point the source code is made available publicly.
This source code will only run withoutmodification on select devices, usuallythe Nexus series of devices. With manydevices, there are proprietary componentswhich have to be provided by themanufacturer, in order for Android to work.
Android has a growing selection of third partyapplications, which can be acquired by users eitherthrough an app store such as Google Play orthe Amazon Appstore, or by downloading and installingthe applications APK file from a third-party site.
Applications are developed in the Java languageusing the Android software developmentkit (SDK). The SDK includes a comprehensiveset of development tools,includinga debugger, software libraries, ahandset emulator basedon QEMU, documentation, sample code, andtutorials.
In order to work around limitations onreaching Google services due to Internetcensorship in the Peoples Republic of China,Android devices sold in the PRC aregenerally customized to use state approvedservices instead.
Android consists of a kernel based on Linux kernel version 2.6and, from Android 4.0 Ice Cream Sandwich onwards, version3.x, with middleware,libraries and APIs writtenin C, and application software running on an applicationframework which includes Java-compatible libraries basedon Apache Harmony.
Androids linux kernel has further architecture changesby Google outside the typical Linux kernel developmentcycle. Android does not have a nativeX WindowSystem by default nor does it support the full set ofstandard GNU libraries, and this makes it difficult toport existing Linux applications or libraries to Android.
Since Android devices are usually battery-powered, Android is designed to manage memory(RAM) to keep power consumption at a minimum,in contrast to desktop operating systems whichgenerally assume they are connected tounlimited mains electricity.
Android manages the apps stored in memoryautomatically: when memory is low, the systemwill begin killing apps and processes that havebeen inactive for a while, in reverse order sincethey were last used (i.e. oldest first).
Google provides majorupdates, incremental in nature, toAndroid every six to nine months, whichmost devices are capable of receiving overthe air. The latest major update isAndroid 4.2 Jelly Bean.
Research company Canalys estimated in the secondquarter of 2009 that Android had a 2.8% share ofworldwide smartphone shipments. By thefourth quarter of 2010 this had grown to 33% of themarket, becoming the top-selling smartphoneplatform.
Respectfully submittedto Prof. Erwin M. Globio, MSIT http://www.slideshare.net/GlRlAlY