Android operating system file system

Documentation of Operating Systems and Developers

Android operating system

Android OS

The android platform was founded by Google and offers on the base the Linux kernel 2.6 a uniform interface for mobile equipment and programmes. Through this it is easily to port and is programmed in Java. After the conversion into the own binary program format Dalvik (.dex) it is not compatible to Java any more. Advantage is the faster execution and the lower memory footprint of programmes than in pure Java. Every Dalvik application is executed in a Dalvik VM of its own. Applications can access all equipment functions. This makes it possible for the programmer to make innovative programmes which offers the user high value by the combination of all sorts of data sources with the equipment functions.

The Eclipse IDE with an official plugin is used for the development. The operating system Android for Smartphones is supported by the Open Handset Alliance. Including more than 30 communication provider, equipment and semiconductor manufacturers as well as software companies. Because Android is an open platform in the meaning of the software and product development the source code shall be available completely at a later time and is in opposite with the market leading closed operating systems Symbian, Palm OS and Windows Mobile.

Android include C/C++ function libraries used by different parts of the operating system.

• Surface manager for 2D and 3D even overlay display
• System C library, specialized for Linux-based devices (BSD implementation)
• SGL, 2D graphic system
• 3D libraries, based on OpenGL ES 1.0 APIs with hardware or software accelerated 3D display
• Media libraries for playback and record of audio, graphic and video formats (MPEG4, H.264, MP3, AAC, AMR, JPG, PNG)
• LibWebCore, Android internet browser
• FreeType, for representing of bitmap and vector fonds
• SQLite, an efficient and slim relational database for all applications

The Android SDK is available for Linux, MacOS and Windows. It contains an emulator with the surface of Android to try applications. After unpacking the SDK the emulator can be found in the subdirectory » oolsemulator.exe» that shows a HTC Smartphone with keyboard.
Standard programs for e-mail, SMS, contacts, calendar, road maps, internet browser and others are preinstalled.

The first Google Android Developer Challenge (ADC) started in April 2008 for engaged programmers to realize and present ideas. Approximately 1,800 programmes were submitted and 20 honoured with a price money under the best 50. Part of the best applications are for example cab4me by combination of Google Maps, GPS signal and a database to send a taxi in the simplest mode by click to the current position on the map. Or GoCart which reads the bar code of goods with the mobile telephone camera and looks over onlineshops and registered shops in the circumference for the best price.

Google creates a sales platform for Smarthone applications with Android Market. At first the market place is provided free of charge. The first Android mobile telephone cames from the taiwanese manufacturer HTC with the T-Mobile G1 smartphone starting at October 22nd, 2008 in the USA and at the beginning of 2009 in Germany. The Android Market was renamed in Google Play on 6th March 2012.

The market research group Gartner, Inc. released a press news about the worldwide market share of smartphone ventors and operating systems on 19th August 2016. In the 2nd quarter 2016, 296.9 million Android units have been sold, this represents a market share of 86.2%. The Android operating system increased his share, in 2nd quarter 2015 the market share was 82.2% with 271.6 million units sold.

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What is Android operating system? A beginners read!

Today, the name Android operating system has become synonymous with a handheld device that can show movies, allow one to talk to another person, send messages, pictures, emails, play games and let you stay in touch with everybody.

Android operating system

Android is perhaps one of the most used Operating System plus framework available for what we call smartphones today. And it is poised to become an all-encompassing framework that will be used not only on a simple handheld device like smartphones but its uses will also be on HDTV’s, Automotive Infotainment systems. Any system which will require a simple, elegant, and easy to develop User Interface might be built on the Android framework.

What is Android?

Android is a Mobile Operating System, developed By Android Inc. and now, marketed by Google. Google and other members of Open Handset Alliance collaborated on Android development and release. Its software stack and framework is built on Linux kernel, which has been very instrumental in its seamless acceptance as an OS of choice in Mobile phones. Android OS consists of over 12 million lines of code written in C / C++ / Java and XML.

Android can be visualized basically as a framework of C C++ and Java libraries based on a Linux kernel. Because of this and the fact that Java apps can be effortlessly built through SDK’s the applications are portable on all mobile devices.

The Android system consists of 3 layered stacks:

1. An application built in Java running on Dalvik Runtime Engine
2. System Library is written in C and C++
3. Kernel-based on Linux

Application Layer

Java language was chosen as the development language. There are a lot of mobile developers who are well versed in Java and hence can have a seamless transition to writing Mobile apps and widgets on Android-powered Smartphones

Java is a proven technology, portable on different software and hardware platform. Java is already available on the majority of mobile phones. Current Java on mobile (J2ME) has a lot of limitations, so major mobile phone companies add in their own extension to the Java library, this makes portability of Java application on mobile more difficult. Normally Java was used to create Java games on mobile; many other applications are still built on the native OS and not on the Java layer.

Sun has been pushing Java technology on mobiles for years, it was successfully deployed on most of the mobile phones, but lack of standardization made it difficult to reach the depths of the Mobile phone market.

Android has a very reach and standardized set of API’s and libraries, developers can use those API to develop games and applications, integrate well into mobile phones, and Java will make Android application portable on all (Android) mobile phones.

The Java program doesn’t run directly on Android; it is converted into Dalvik byte code. Basically Android can make any app run as long as it can be converted to Dalvik byte code.

The System Libraries

The system libraries on Android mainly built on C and C++, so they are fast and efficient. Since the library runs on top of the Linux kernel, there are a lot of drivers and libraries available which can be customized as per the vendor’s requirement.

The Linux Kernel

The Linux kernel was chosen because it was proven to be stable and powerful. Linux has good memory management, process management and already built in with many other functions like TCP/IP networking which is necessary for an operating system (especially you need it to connect to data network on your mobile).

For a new hardware mobile manufacturer, the first thing to do for building an Android platform is to build the device driver on the Linux kernel; there should be a lot of developers around who have the know-how to build the software stack from scratch or customize it from the available software.

There were a lot of companies trying to build a mobile phone operating system based on Linux kernel before Android did, but have not been very successful.

Even Motorola and Nokia had released some mobile and internet devices which run on the Linux operating system, but they were not very successful as well, like the Motorola A series phone started with A760. Nokia has an Internet Table device (N770) which was built using the Linux operating system too. From a technical point of view, Android using Java over Linux is a smart move. Both Java and Linux are proven the technology and provide portability for mobile applications on the Android platform.

Date: January 12, 2017 Tags: Android, Open Source

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Nitin Agarwal is an MVP alumni and a Pro Blogger. He was awarded as Most Valuable Professional for 3 times by Microsoft in Windows Expert — Consumer category. He is immensely inspired by Bill Gates, Steve Jobs and APJ Abdul Kalam.

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Android File System And Directory Structure Explained

Last Updated: November 7, 2014

Most people are familiar with the file layout on Windows and are happy navigating the Windows file System.

Windows uses a drive letter for each physical drive or partition.e.g. C: drive

Note: A Physical drive will have at least 1 partition but can have more than one. This is true for both Windows and Android.

[outline style=”yellow”]What is a Disk Partition? – Disks can be subdivided into smaller disks called partitions. Partitions appear and can be used as if they were separate physical disks. [/outline]

If you insert a USB drive into your windows machine in shows up as a disk with an assigned drive letter.

Although windows shows a disk icon the disks could be partitions of a single physical disk.

Each disk partition has a root directory which contains files and folders (directories).

The root of the C drive is C:\ and of the F drive is F:\ etc

Android File System Structure

Android uses the Linux file system structure which has a single root .

The diagram below shows the structure

The system partitions and directories are protected and unless your device is rooted you don’t normally have access to these although some file managers will display them.

Physical disks and partitions appear under the root as a directories , and do not have a drive letter as in Windows.

Android doesn’t normally come with a default file manager, and so you will need to install a file manager App like Astro file manager, to locate and manage files and folders.

The sdcard and ext-sdcard Partitions

The sdcard partition is the main storage area for user data and files. It also contains App settings and data.

The sdcard partition exists even though you may not have an external sd card.

It is the internal partition.

If you open the sdcard directory you will see something like this:

Note: partial listing only

These files and directories contain your pictures,films,downloads etc as well as App data and settings.

You can view these files from your PC by connecting your device to a PC using a USB cable.

The ext-sdcard partition will only be visible if your device supports external storage, usually using a microSD slot.

External sd cards use either the FAT,FAT32 or exFAT file system formats.

Most devices support FAT and FAT32, but support for exFAT is limited.

The choice of file system is governed by the partition size as follows:

Card Type

Card Type File System

Max Capacity

SD FAT 2GB SDHC FAT32 32GB see Note SDXC exFAT 2TB

Note: Windows format size limit of 32GB. Can be larger but need to format using external tools. Windows XP could fomat FAT32 Volumes upto 128 GB

Android File Associations

Just as with other operating systems like Windows, Android will use an App to open a particular file type,denoted by the extension.

For example if you try to open a pdf file it will normally use Adobe reader (if installed) to open the file.

To open a file you will normally need to located the file using a file manager.

Just press the file to open it.

If the file type doesn’t already have an App associated with it you should be prompted to choose between the available Apps.

The option to always use that App sets it as the default App for that file type.

If you set it as the default App you will not be prompted again unless you remove the association.

To remove an association you need to remove it from the App itself.

So if the pdf files open with adobe reader and you want to change that:

1. Go to Settings>Apps>Select Adobe reader,
2. Then go to the Launch by default section
3. and Clear defaults

The next time you try to open a pdf file you will be promoted to choose an App.

Android File Managers

If you search the Google play store you will find many file managers.

Which App is the most suitable depends on what you want to do. You should bear in mind that more features/functionality isn’t always better.

File managers like ESF have lots of functionality including:

• Built in FTP client
• Task Manager
• Cloud storage client
• etc

However for many this is a bit of an overkill, and so you might consider installing one of the simpler file managers like file manager and Astro file manager.

File Downloads

When you download a file using Google chrome or another browser App the file it is stored in the download directory.

You can access the directory contents through a shortcut in the Apps folder (if provided).

You can also use a file manager to locate it the folder called download. It is under your primary storage (called sdcard)

Summary

Android uses the Linux File and Directory Structure which consists of a single root.

All drives and partitions are displayed as directories in this tree like structure.

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