Definitions

personal organiser

Symbian OS

Symbian OS is an open operating system, designed for mobile devices, with associated libraries, user interface frameworks and reference implementations of common tools, produced by Symbian Ltd. It is a descendant of Psion's EPOC and runs exclusively on ARM processors.

On 24 June 1998, Symbian Ltd. was formed as a partnership between Ericsson, Nokia, Motorola and Psion, to exploit the convergence between PDAs and mobile phones. Symbian was previously owned by Nokia (56.3%), Ericsson (15.6%), Sony Ericsson (13.1%), Panasonic (10.5%) and Samsung (4.5%). Ten years to the day later, on 24 June 2008, Nokia announced that they intended to acquire all shares that they did not already own. The acquisition was of €264 million, or $410 million.

On 24 June 2008 the Symbian Foundation was announced with the aim to "provide royalty-free software and accelerate innovation".

Design

Symbian OS, with its roots in Psion Software's EPOC, is structured like many desktop operating systems with pre-emptive multitasking and memory protection. EPOC was inspired by an OpenVMS-like approach to multitasking with server-based asynchronous serialised access based on events.

Symbian OS was built to follow three design rules: the integrity and security of user data is paramount, user time must not be wasted, and all resources are scarce. This led to a continuation of the use of servers, a microkernel, a request and callback approach to all services, an absolute division of user interfaces from system or application services, reuse and openness, extensibility, and robust management and resource recovery to support extended always-on operation. For hardware the OS is optimised for low-power battery-based devices and for ROM-based systems (e.g. features like XIP and re-entrancy in shared libraries). Applications, and the OS, follow an object-oriented design, MVC.

Later OS iterations diluted this approach in response to market demands, notably the introduction of a real-time kernel and a platform security model in versions 8 and 9.

There is a strong emphasis on conserving resources, using Symbian-specific programming idioms such as descriptors and a cleanup stack. There are similar techniques for conserving disk space (though the disks on Symbian devices are usually flash memory). Furthermore, all Symbian OS programming is event-based, and the CPU is switched off when applications are not directly dealing with an event. This is achieved through a programming idiom called active objects. Similarly the OS approach to threads vs. processes is driven by reducing overheads.

Symbian OS EKA2 supports sufficiently-fast real-time response such that it is possible to build a single-core phone around it—that is, a phone in which a single processor core executes both the user applications and the signalling stack. This is a feature which is not available in Linux. This has allowed SymbianOS EKA2 phones to become smaller, cheaper and more power efficient.

Competition

Symbian OS is the leading OS in the "smart mobile device" market. Statistics published February 2007 showed that Symbian OS had a 67% share of the smart mobile device market, with Microsoft having 13% (through Windows CE and Windows Mobile) and RIM having 10%. Other competitors include Palm OS, iPhone OS, Qualcomm's BREW, Google Android, SavaJe and MontaVista Software.

Structure

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

Symbian OS is designed to emphasize 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 in the Symbian OS but an object-oriented persistence model has been placed over the underlying FAT, providing a POSIX-style interface and a streaming model. The internal data formats rely on using the same API that create the data to run all file manipulations - this has created the problems of data-dependence and associated difficulties with changes and data migration.

There is a large networking and communication subsystem, which has three main servers: 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, implementing different types of networking protocol scheme. The subsystem also contains code that pertains to 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 are contained in Symbian OS, while most of the actual user interfaces are maintained by third parties. This component is known as UIKON. The OS also contains the graphics, text layout, and font rendering libraries.

All Symbian applications are built up from three 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 required functions, the application view, data model, and data interface, are created independently and interact solely through their APIs with the other classes. UIQ and S60 both extend this approach, in two different ways.

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 need to do a great deal of integration work to make a Symbian OS phone.

Symbian OS device manufacturers also get supplied with an example user-interface layer called "TechView". It provides a basis to start customisation and is also the environment in which much Symbian OS test code and example code runs. It is very similar to the user interface from a Psion Series 5 personal organiser, so it is not used for any given phone user interface.

History

Psion

In 1980, Psion was founded by David Potter.

EPOC16

After the failure of the MC400 Psion released its Series 3 devices from 1991 to 1998 which also used the EPOC16 OS, also known as SIBO, which supported a simple programming language called OPL and an IDE called OVAL.

EPOC OS Releases 1–3

Work started on the from-scratch 32-bit version in late 1994. The Series 5 device, released in June 1997, used the first iterations of the EPOC32 OS, codenamed "Protea" and developed from scratch in 3.5 years, and the "Eikon" GUI.

EPOC Release 4

Oregon Scientific Osaris

EPOC Release 5

The Psion Series 5mx, Series 7, Psion Revo, Diamond Mako, Psion Netbook, netPad, GeoFox One, and Ericsson MC218 were released in 1999 using ER5. A phone project was announced at CeBIT, the Phillips Illium/Accent, but did not achieve a commercial release. This release has been retrospectively dubbed Symbian OS 5; it was never called that at the time.

ER5u

The first phone, the Ericsson R380 was released using ER5u in November 2000. It was not an 'open' phone – software could not be installed. Notably, a number of never-released Psion prototypes for next generation PDAs, including a Bluetooth Revo successor codenamed Conan were using ER5u. The 'u' in the name refers to the fact that it supported Unicode.

Symbian OS v6.0 and 6.1

The OS was renamed Symbian OS and was envisioned as the base for a new range of smartphones. This release sometime is called ER6. Psion gave 130 key staff to the new company and retained a 31% shareholding in the spun-out business.

The first 'open' Symbian OS phone, the Nokia 9210 Communicator, was released in June 2001. Bluetooth support added. Almost 500,000 Symbian phones were shipped in 2001, rising to 2.1 million the following year.

Development of different UIs was made generic with a "reference design strategy" for either 'smartphone' or 'communicator' devices, subdivided further into keyboard- or tablet-based designs. Two reference UIs (DFRDs or Device Family Reference Designs) were shipped - Quartz and Crystal. The former was merged with Ericsson's 'Ronneby' design and became the basis for the UIQ interface, the latter reached the market as the Nokia Series 80 UI.

Later DFRDs were Sapphire, Ruby, and Emerald. Only Sapphire came to market, evolving into the Pearl DFRD and finally the Nokia Series 60 UI, a keypad-based 'square' UI for the first true smartphones. The first one of them was the Nokia 7650 smartphone (featuring Symbian OS 6.1), which was also the first with a built-in camera, with VGA (0.3 Mpx = 640*480) resolution.

Despite these efforts to be generic the UI was clearly split between competing companies, Crystal or Sapphire was Nokia, Quartz was Ericsson. DFRD was abandoned by Symbian in late 2002, as part of an active retreat from UI development in favour of 'headless' delivery. Pearl was given to Nokia, Quartz development was spun-off as UIQ Technology AB, and work with Japanese firms was quickly folded into the MOAP standard.

Symbian OS 7.0 and 7.0s

First shipped in 2003. This is an important Symbian release which appeared with all contemporary user interfaces including UIQ (Sony Ericsson P800, P900, P910, Motorola A925, A1000), Series 80 (Nokia 9300, 9500), Series 90 (Nokia 7710), Series 60 (Nokia 3230, 6260, 6600, 7310) as well as several FOMA phones in Japan. It also added EDGE support and IPv6. Java support was changed from pJava and JavaPhone to one based on the Java ME standard.

One million Symbian phones were shipped in Q1 2003, with the rate increasing to one million a month by the end of 2003.

Symbian OS 7.0s was a version of 7.0 special adapted to have greater backwards compatibility with Symbian OS 6.x, partly for compatibility between the Communicator 9500 and its predecessor the Communicator 9210.

In 2004, Psion sold its stake in Symbian. The same year, the first worm for mobile phones using Symbian OS, Cabir, was developed, which used Bluetooth to spread itself to nearby phones. See Cabir and Symbian OS threats.

Symbian OS 8.0

First shipped in 2004, one of its advantages would have been a choice of two different kernels (EKA1 or EKA2). However, the EKA2 kernel version did not ship until Symbian OS 8.1b. The kernels behave more or less identically from user-side, but are internally very different. EKA1 was chosen by some manufacturers to maintain compatibility with old device drivers, while EKA2 was a real-time kernel. 8.0b was deproductized in 2003.

Also included were new APIs to support CDMA, 3G, two-way data streaming, DVB-H, and OpenGL ES with vector graphics and direct screen access.

Symbian OS 8.1

Basically a cleaned-up version of 8.0, this was available in 8.1a and 8.1b versions, with EKA1 and EKA2 kernels respectively. The 8.1b version, with EKA2's single-chip phone support but no additional security layer, was popular among Japanese phone companies desiring the real-time support but not allowing open application installation. The first and maybe the most famous smartphone featuring Symbian OS 8.1a was Nokia N90 in 2005, Nokia's first in Nseries. It comes with Carl-Zeiss Tessar optics and a 2 Mpx (1600*1200) camera with video capabilities to take VHS quality (352×288) videos and a huge screen resolution (at the time) of 352*416 pixels.

Symbian OS 9.0

This version was used for internal Symbian purposes only. It was de-productised in 2004. 9.0 marked the end of the road for EKA1. 8.1a is the final EKA1 version of Symbian OS.

Symbian OS has generally maintained reasonable binary compatibility. In theory the OS was BC from ER1-ER5, then from 6.0 to 8.1b. Substantial changes were needed for 9.0, related to tools and security, but this should be a one-off event. The move from requiring ARMv4 to requiring ARMv5 did not break backwards compatibility.

A Symbian developer proclaims that porting from Symbian 8.x to Symbian 9.x is a more daunting process than Symbian says.

Symbian OS 9.1

Released early 2005. It includes many new security related features, particularly a controversial platform security module facilitating mandatory code signing. Symbian argues that applications and content, and therefore a developers investment, are better protected than ever, however others contend that the requirement that every application be signed (and thus approved) violates the rights of the end-user, the owner of the phone, and limits the amount of free software available. The new ARM EABI binary model means developers need to retool and the security changes mean they may have to recode. S60 platform 3rd Edition phones have Symbian OS 9.1. Sony Ericsson is shipping the M600 and P990 based on Symbian OS 9.1. The earlier versions had a fatal defect where the phone hangs temporarily after the owner sent hundreds of SMS'es. However, on 13 September 2006, Nokia released a small program to fix this defect.

Support for Bluetooth 2.0 (was 1.2)

Symbian OS 9.2

Released Q1 2006. Support for OMA Device Management 1.2 (was 1.1.2). S60 3rd Edition Feature Pack 1 phones have Symbian OS 9.2. Nokia phones with Symbian OS 9.2 OS: Nokia E90, Nokia E66, Nokia E71, Nokia E51, Nokia N95, Nokia N82, Nokia N81, Nokia 6290, Nokia 6120 classic, Nokia 5700.

Symbian OS 9.3

Released on 12 July 2006. Upgrades include improved memory management and native support for Wifi 802.11, HSDPA, Vietnamese language support. The Nokia N96 as well as the Nokia N78 feature Symbian OS 9.3. As of Q2 2008, OS 9.3 has just entered new devices.

Symbian OS 9.4

Announced in March 2007. Provides the concept of demand paging which is available from v9.3 onwards. Applications should launch up to 75% faster. Additionally, SQL support is provided by SQLite. Ships with the Nokia 5800.

Symbian OS 9.5

Native support for mobile digital television broadcasts in DVB-H and ISDB-T formats and also location services.

Open source software for Symbian 9.1

The following open source software has been rewritten for Symbian 9.1:

Utilities

Game emulation

Multimedia

  • OggPlay – Audio player with ogg vorbis audio format support

Symbian has announced PIPS (PIPS Is POSIX on Symbian) which may increase the number of open source projects written for Symbian 9.1.

Security and malware

Symbian OS has been subject to a variety of viruses, the best known of which is Cabir. Usually these send themselves from phone to phone by Bluetooth. So far, none have taken advantage of any flaws in Symbian OS – instead, they have all asked the user whether they would like to install the software, with somewhat prominent warnings that it can't be trusted.

However, with a view that the average mobile phone user shouldn't have to worry about security, Symbian OS 9.x has adopted a capability model. Installed software will theoretically be unable to do damaging things (such as costing the user money by sending network data) without being digitally signed – thus making it traceable. Commercial developers who can afford the cost can apply to have their software signed via the Symbian Signed program. Currently, developers also have the option of self-signing their programs. However, the set of available features is smaller, and certain operators have opted on fully disabling certificates other than the Symbian Signed certificates.

Some other hostile programs are listed below, but all of them still require the input of the user to run.

  • Drever. A is a malicious SIS file trojan that attempts to disable the automatic startup from Simworks and Kaspersky Symbian Anti-Virus applications.
  • Locknut. B is a malicious SIS file trojan that pretends to be patch for Symbian S60 mobile phones. When installed, it drops a binary that will crash a critical system service component. This will prevent any application from being launched in the phone.
  • Mabir. A is basically Cabir with added MMS functionality. The two are written by the same author, and the code shares many similarities. It spreads using Bluetooth via the same routine as early variants of Cabir. As Mabir. A activates it will search for the first phone it finds, and starts sending copies of itself to that phone.
  • Fontal. A is an SIS file trojan that installs a corrupted file which causes the phone to fail at reboot. If the user tries to reboot the infected phone, it will be permanently stick on the reboot, and cannot be used without disinfection – that is, the use of the reformat key combination which causes the phone to lose all data. Being a trojan, Frontal. A cannot spread by itself – the most likely way for the user to get infected would be to acquire the file from untrusted sources, and then install it to the phone, inadvertently or otherwise.

Devices that have used the Symbian OS

On 16 November 2006, the 100 millionth smartphone running the OS was shipped.

Developing on Symbian OS

The native language of the Symbian OS is C++, although it is not a standard implementation. There are multiple platforms based upon Symbian OS that provide an SDK for application developers wishing to target a Symbian OS device – the main ones being UIQ and S60. Individual phone products, or families, often have SDKs or SDK extensions downloadable from the manufacturer's website too. The SDKs contain documentation, the header files and library files required to build Symbian OS software, and a Windows-based emulator ("WINS"). Up until Symbian OS version 8, the SDKs also included a version of the GCC compiler (a cross-compiler) required to build software to work on the device.

Symbian OS 9 uses a new ABI and so requires a new compiler – a choice of compilers is available including a new version of GCC (see external links below). In terms of SDKs, UIQ Technology now provides a simplified framework so that the single UIQ SDK forms the basis for developing on all UIQ 3 devices, such as the Sony Ericsson P990 and Sony Ericsson M600.

Unfortunately, Symbian C++ programming has a steep learning curve, as Symbian requires the use of special techniques such as descriptors and the cleanup stack. This can make even relatively simple programs harder to implement than in other environments. Moreover, it is questionable whether Symbian's techniques e.g. the memory management paradigm are actually so beneficial. It is possible that the techniques, developed for the much more restricted mobile hardware of the 1990s, do cause unnecessary complexity in source code; programmers are required to concentrate on bug-prone low-level routines instead of truly application-specific features. It is difficult, however, to make a move towards a more high-level and modern programming paradigm in Symbian, because the platform is so tightly bound to semi-obsolete thinking models about mobile software development.

Symbian C++ programming is commonly done with an IDE. For previous versions of Symbian OS, the commercial IDE CodeWarrior for Symbian OS was favoured. The CodeWarrior tools were replaced during 2006 by Carbide.c++, an Eclipse-based IDE developed by Nokia. Carbide.c++ is offered in 4 different versions: Express, Developer, Professional, and OEM, with increasing levels of capability. Full featured software can be created and released with the Express edition, which is free. Features such as UI design, crash debugging etc. are available in the other charged for editions. Microsoft Visual Studio 2003 and 2005 are also supported through the Carbide.vs plugin.

Symbian OS's flavour of C++ is very specialised. However, many Symbian OS devices can also be programmed in OPL, Python, Visual Basic, Simkin, and Perl – together with the Java ME and PersonalJava flavours of Java.

Visual Basic programmers can use NS Basic to develop apps for S60 3rd Edition and UIQ 3 devices.

In the past, Visual Basic, VB.NET, and C# development for Symbian were possible through AppForge Crossfire, a plugin for Microsoft Visual Studio. March 13, 2007 AppForge ceased operations, Oracle purchased the intellectual property, but announced that they do not plan to sell or provide support for former AppForge products.

There is also a version of a Borland IDE for Symbian OS. Symbian OS development is also possible on Linux and Mac OS X using tools and techniques developed by the community, partly enabled by Symbian releasing the source code for key tools. A plugin that allows development of Symbian OS applications in Apple's Xcode IDE for Mac OS X is available.

Once developed, Symbian OS applications need to find a route to customers' mobile phones. They are packaged in SIS files which may be installed over-the-air, via PC connect or in some cases via Bluetooth or memory cards. An alternative is to partner with a phone manufacturer to have the software included on the phone itself. The SIS file route is more difficult for Symbian OS 9.x, because any application wishing to have any capabilities beyond the bare minimum must be signed via the Symbian Signed program. There are however various hacks, which allow installing unsigned programs with any capabilities to Symbian OS 9.x.

Introduction of the Symbian Signed system in which application developers need to pay in order to use some of the more attractive smartphone features (as contrasted to platforms like Palm OS and Windows Mobile) is making it an increasingly unpopular platform for Open Source projects, independent developers and small startups. This situation is worsened by the fragmentation of user interface systems (UIQ vs S60 vs MOAP), meaning that developers need to build and maintain multiple incompatible versions of their software if they want to target multiple devices which use the same underlying Symbian OS version.

Java ME applications for Symbian OS are developed using standard techniques and tools such as the Sun Java Wireless Toolkit (formerly the J2ME Wireless Toolkit). They are packaged as JAR (and possibly JAD) files. Both CLDC and CDC applications can be created with NetBeans. Other tools include SuperWaba, which can be used to build Symbian 7.0 and 7.0s programs using Java.

Nokia S60 phones can also run python scripts when the interpreter is installed, with a custom made API that allows for Bluetooth support and such. There is also an interactive console to allow the user to write python scripts directly from the phone.

Hacking Symbian

S60 version 3 (OS 9.1, 9.2 & 9.3) devices can be hacked to remove the platform security introduced in OS 9.1 onwards thus allowing users to install "unsigned" files (files without certificates validated by Symbian) and allowing access to previously locked system files.This allows changing of how the operating system works, allowing hidden applications etc. to be viewable and possibly increases the threat posed by mobile viruses as the operating system files are now exposed..

See also

Notes and references

  • Morris, Ben The Symbian OS architecture sourcebook : design and evolution of a mobile phone OS, John Wiley & Sons (2007), ISBN-13: 978-0-470-01846-0.

External links

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