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Wednesday, December 14, 2011

What's Symbian?(operating system)

Symbian is a mobile operating system (OS) and computing platform designed for smartphones and currently maintained by Accenture. The Symbian platform is the successor to Symbian OS and Nokia Series 60; unlike Symbian OS, which needed an additional user interface system, Symbian includes a user interface component based on S60 5th Edition. The latest version, Symbian^3, was officially released in Q4 2010, first used in the Nokia N8. In May 2011 an update, Symbian Anna, was officially announced, followed by Symbian Belle in August 2011.

Symbian OS was originally developed by Symbian Ltd. It is a descendant of Psion's EPOC and runs exclusively on ARM processors, although an unreleased x86 port existed.

Some estimates indicate that the cumulative number of mobile devices shipped with the Symbian OS up to the end of Q2 2010 is 385 million.

By April 5, 2011, Nokia released Symbian under a new license and converted to a proprietary shared-source model as opposed to an open source project.

On February 11, 2011, Nokia announced that it would migrate away from Symbian to Windows Phone 7. Nokia CEO Stephen Elop announced Nokia's first ever Windows Phones in the Nokia World 2011, the Lumia 800 and Lumia 710. These phones were launched on November 14, 2011. In June 22, 2011 Nokia has made an agreement with Accenture as an outsourcing program. Accenture will provide Symbian based software development and support services to Nokia through 2016 and about 2,800 Nokia employees will be Accenture employees at early October 2011. The transfer was completed on September 30, 2011

The Symbian platform was created by merging and integrating software assets contributed by Nokia, NTT DoCoMo, Sony Ericsson and Symbian Ltd., including Symbian OS assets at its core, the S60 platform, and parts of the UIQ and MOAP(S) user interfaces.

In December 2008, Nokia bought Symbian Ltd., the company behind Symbian OS; consequently, Nokia became the major contributor to Symbian's code, since it then possessed the development resources for both the Symbian OS core and the user interface. Since then Nokia has been maintaining its own code repository for the platform development, regularly releasing its development to the public repository. Symbian was intended to be developed by a community led by the Symbian Foundation, which was first announced in June 2008 and which officially launched in April 2009. Its objective was to publish the source code for the entire Symbian platform under the OSI- and FSF-approved Eclipse Public License (EPL). The code was published under EPL on 4 February 2010; Symbian Foundation reported this event to be the largest codebase transitioned to Open Source in history.

However, some important components within Symbian OS were licensed from third parties, which prevented the foundation from publishing the full source under EPL immediately; instead much of the source was published under a more restrictive Symbian Foundation License (SFL) and access to the full source code was limited to member companies only, although membership was open to any organisation.

In November 2010, the Symbian Foundation announced that due to a lack of support from funding members, it would transition to a licensing-only organisation; Nokia announced it would take over the stewardship of the Symbian platform. Symbian Foundation will remain the trademark holder and licensing entity and will only have non-executive directors involved.

On February 11, 2011, Nokia announced a partnership with Microsoft which would see it adopt Windows Phone 7 for smartphones, reducing the number of devices running Symbian over the coming two years. As a consequence, the use of the Symbian platform for building mobile applications dropped rapidly. A June 2011 research indicated that over 39% of mobile developers using Symbian at the time of publication, were planning to abandon the platform.

By April 5, 2011, Nokia ceased to open source any portion of the Symbian software and reduced its collaboration to a small group of pre-selected partners in Japan. Source code released under the EPL remains available in third party repositories.

Operating System:
The All over Model contains the following layers, from top to bottom:

UI Framework Layer
Application Services Layer
Java ME
OS Services Layer
generic OS services
communications services
multimedia and graphics services
connectivity services
Base Services Layer
Kernel Services & Hardware Interface Layer
The Base Services Layer is the lowest level reachable by user-side operations; it includes the File Server and User Library, a Plug-In Framework which manages all plug-ins, Store, Central Repository, DBMS and cryptographic services. It also includes the Text Window Server and the Text Shell: the two basic services from which a completely functional port can be created without the need for any higher layer services.

Symbian has a microkernel architecture, which means that the minimum necessary is within the kernel to maximise robustness, availability and responsiveness. It contains a scheduler, memory management and device drivers, but other services like networking, telephony and filesystem support are placed in the OS Services Layer or the Base Services Layer. The inclusion of device drivers means the kernel is not a true microkernel. The EKA2 real-time kernel, which has been termed a nanokernel, contains only the most basic primitives and requires an extended kernel to implement any other abstractions.

Symbian is designed to emphasise compatibility with other devices, especially removable media file systems. Early development of EPOC led to adopting FAT as the internal file system, and this remains, but an object-oriented persistence model was placed over the underlying FAT to provide a POSIX-style interface and a streaming model. The internal data formats rely on using the same APIs that create the data to run all file manipulations. This has resulted in data-dependence and associated difficulties with changes and data migration.

There is a large networking and communication subsystem, which has three main servers called: ETEL (EPOC telephony), ESOCK (EPOC sockets) and C32 (responsible for serial communication). Each of these has a plug-in scheme. For example, ESOCK allows different ".PRT" protocol modules to implement various networking protocol schemes. The subsystem also contains code that supports short-range communication links, such as Bluetooth, IrDA and USB.

There is also a large volume of user interface (UI) Code. Only the base classes and substructure were contained in Symbian OS, while most of the actual user interfaces were maintained by third parties. This is no longer the case. The three major UIs — S60, UIQ and MOAP — were contributed to Symbian in 2009. Symbian also contains graphics, text layout and font rendering libraries.

All native Symbian C++ applications are built up from three framework classes defined by the application architecture: an application class, a document class and an application user interface class. These classes create the fundamental application behaviour. The remaining needed functions, the application view, data model and data interface, are created independently and interact solely through their APIs with the other classes.

Many other things do not yet fit into this model — for example, SyncML, Java ME providing another set of APIs on top of most of the OS and multimedia. Many of these are frameworks, and vendors are expected to supply plug-ins to these frameworks from third parties (for example, Helix Player for multimedia codecs). This has the advantage that the APIs to such areas of functionality are the same on many phone models, and that vendors get a lot of flexibility. But it means that phone vendors needed to do a great deal of integration work to make a Symbian OS phone.

Symbian includes a reference user-interface called "TechView." It provides a basis for starting customisation and is the environment in which much Symbian test and example code runs. It is very similar to the user interface from the Psion Series 5 personal organiser and is not used for any production phone user interface

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