Symbian OS is one of Nokia‘s mobile operating systems for mobile devices and low-end smartphones, with associated libraries, user interface, frameworks and reference implementations of common tools, 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.
In 2008, the former Symbian Software Limited was acquired by Nokia and a new independent non-profit organisation called the Symbian Foundation was established. Symbian OS and its associated user interfaces S60, UIQ and MOAP(S) were contributed by their owners to the foundation with the objective of creating the Symbian platform as a royalty-free, open source software. The platform has been designated as the successor to Symbian OS, following the official launch of the Symbian Foundation in April 2009. The Symbian platform was officially made available as open source code in February 2010.
Devices based on Symbian OS accounted for 43.5% of worldwide smartphone sales in 2010 Q2. 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.
Symbian features pre-emptive multitasking and memory protection, like other operating systems (especially those created for use on desktop computers). EPOC’s approach to multitasking was inspired by VMS and is based on asynchronous server-based events.
Symbian OS was created with three systems design principles in mind:
- the integrity and security of user data is paramount,
- user time must not be wasted, and
- all resources are scarce.
To best follow these principles, Symbian uses a microkernel, has a request-and-callback approach to services, and maintains separation between user interface and engine. 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 itself, follow an object-oriented design: Model-view-controller (MVC).
Later OS iterations diluted this approach in response to market demands, notably with 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 which is exemplified by Symbian-specific programming idioms like 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 programming is event-based, and the CPU is switched into a low power mode when applications are not directly dealing with an event. This is achieved through a programming idiom called active objects. Similarly the Symbian approach to threads and processes is driven by reducing overheads.
The Symbian kernel (EKA2) supports sufficiently-fast real-time response 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 has allowed Symbian EKA2 phones to become smaller, cheaper and more power efficient than their predecessors.
In the number of “smart mobile device” sales, Symbian devices are the market leaders. Statistics published for the second quarter of 2010 showed that Symbian devices comprised a 41.2% share of smart mobile devices sold, with RIM having 18.2%, Android having 17.2%, and Apple having 15.1% (through iPhone OS) 
Previous reports on device shipments as published in February 2010 showed that the Symbian devices comprised a 47.2% share of the smart mobile devices shipped in 2009, with RIM having 20.8%, Apple having 15.1% (through iPhone OS), Microsoft having 8.8% (through Windows CE and Windows Mobile) and Android having 4.7%. Other competitors include webOS, Qualcomm‘s BREW, SavaJe, Linux and MontaVista Software.
Although the share of the global smartphone market dropped from 52.4% in 2008 to 47.2% in 2009, the shipment volume of Symbian devices grew 4.8%, from 74.9 million units to 78.5 million units. From Q2 2009 to Q2 2010, the shipment volume of Symbian devices grew 41.5%, by 8.0 million units, from 19,178,910 units to 27,129,340; compared with an increase of 9.6 million units for Android, but 3.3 million units for RIM and 3.2 million units for Apple.
Improvement to symbian^3
2011 is a big year for Nokia and for Symbian OS, 4-5 improvements are planned for the Popular OS Including: a UI re-haul, New HTML 5 browser also a new QWERTY keyboard is expected, according to Nokia’s own information this is all expected in the year 2011, improvements in hardware are also expected for example: dual core processors by late 2011 at the earliest also mid way through 2011 1GHZ processors will come into the market with Nokia and also more graphics memory and the new Meego OS in the first half of 2011. Please note this is only for Symbian^3 only.
The Symbian System Model contains the following layers, from top to bottom:
- UI Framework Layer
- Application Services Layer
- 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 required 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.
EPOC is a family of graphical operating systems developed by Psion for portable devices, primarily PDAs. EPOC came from epoch, the beginning of an era, but was backfitted by the engineers to “Electronic Piece Of Cheese”.
EPOC16, originally simply named EPOC, was the operating system developed by Psion in the late 1980s and early 1990s for Psion’s “SIBO” (SIxteen Bit Organisers) devices. All EPOC16 devices featured an 8086-family processor and a 16-bit architecture. EPOC16 was a single-user pre-emptive multitasking operating system, written in Intel 8086 assembler language and C and designed to be delivered in ROM. It supported a simple programming language called Open Programming Language (OPL) and an integrated development environment (IDE) called OVAL. SIBO devices included the: MC200, MC400, Series 3 (1991–98), Series 3a, Series 3c, Series 3mx, Siena, Workabout and Workabout mx. The MC400 and MC200, the first EPOC16 devices, shipped in 1989.
In the late 1990s, the operating system was referred to as EPOC16 to distinguish it from Psion’s then-new EPOC32 OS.
The first version of EPOC32, Release 1 appeared on the Psion Series 5 ROM v1.0 in 1997. Later, ROM v1.1 featured Release 3 (Release 2 was never publicly available.) These were followed by the Psion Series 5mx, Revo / Revo plus, Psion Series 7 / netBook and netPad (which all featured Release 5).
The EPOC32 operating system, at the time simply referred to as EPOC, was later renamed Symbian OS. Adding to the confusion with names, before the change to Symbian, EPOC16 was often referred to as SIBO to distinguish it from the “new” EPOC. Despite the similarity of the names, EPOC32 and EPOC16 were completely different operating systems, EPOC32 being written in C++ from a new codebase with development beginning during the mid 1990s.
EPOC32 was a pre-emptive multitasking, single user operating system with memory protection, which encourages the application developer to separate their program into an engine and an interface. The Psion line of PDAs come with a graphical user interface called EIKON which is specifically tailored for handheld machines with a keyboard (thus looking perhaps more similar to desktop GUIs than palmtop GUIs ). However, one of EPOC’s characteristics is the ease with which new GUIs can be developed based on a core set of GUI classes, a feature which has been widely explored from Ericsson R380 and onwards.
EPOC32 was originally developed for the ARM family of processors, including the ARM7, ARM9, StrongARM and Intel’s XScale, but can be compiled towards target devices using several other processor types.
During the development of EPOC32, Psion planned to license EPOC to third-party device manufacturers, and spin off its software division as Psion Software. One of the first licensees was the short-lived Geofox, which halted production with less than 1,000 units sold. Ericsson marketed a rebranded Psion Series 5mx called the MC218, and later created the EPOC Release 5.1 based smartphone, the R380. Oregon Scientific also released a budget EPOC device, the Osaris (notable as the only EPOC device to ship with Release 4).
EPOC OS Releases 1–5
Work started on the 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 the “Eikon” graphical user interface.
The Oregon Scientific Osaris was the only PDA to use the ER4.
The Psion Series 5mx, Psion Series 7, Psion Revo, Diamond Mako, Psion netBook 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.
The first phone using ER5u, the Ericsson R380 was released 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 6.0 and 6.1
The OS was renamed Symbian OS and was envisioned as the base for a new range of smartphones. This release is sometimes 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 was 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, 6670, 7610) as well as several FOMA phones in Japan and Siemens SX1(VGA Camera, MMC card, Bluetooth, Infraport, radio) – the first and the last symbian phone from Siemens. 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 backward 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 deproductised in 2003.
Symbian OS 8.1
An improved 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.
Symbian OS 9
Symbian OS 9.0 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 code 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.
Symbian OS 9.1 and open source development
Released early 2005. It includes many new security related features, including platform security module facilitating mandatory code signing. 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 defect where the phone hangs temporarily after the owner sent a large number of SMS’es. However, on 13 September 2006, Nokia released a small program to fix this defect. Support for Bluetooth 2.0 was also added.
Symbian 9.1 introduced capabilities and a Platform Security framework. To access certain APIs, developers have to sign their application with a digital signature. Basic capabilities are user-grantable and developers can self-sign them, while more advanced capabilities require certification and signing via the Symbian Signed program, which uses independent ‘test houses’ and phone manufacturers for approval. For example, file writing is a user-grantable capability while access to Multimedia Device Drivers require phone manufacturer approval. A TC TrustCenter ACS Publisher ID certificate is required by the developer for signing applications.
Symbian OS 9.2
Released Q1 2006. Support for OMA Device Management 1.2 (was 1.1.2). Vietnamese language support. S60 3rd Edition Feature Pack 1 phones have Symbian OS 9.2. Nokia phones with Symbian OS 9.2 OS include the Nokia E71, Nokia E90, Nokia N95, Nokia N82, Nokia N81 and Nokia 5700.
Symbian OS 9.3
Released on 12 July 2006. Upgrades include improved memory management and native support for Wifi 802.11, HSDPA. The Nokia E72, Nokia 5730 XpressMusic, Nokia N79, Nokia N96, Nokia E52, Nokia E75, Nokia 5320 XpressMusic, Sony Ericsson P1 and others feature Symbian OS 9.3.
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 Samsung i8910 Omnia HD, Nokia N97, Nokia N97 mini, Nokia 5800 XpressMusic, Nokia 5530 XpressMusic, Nokia 5228, Nokia 5230, Nokia 5233, Nokia 5235, Nokia C6-00, Nokia X6, Sony Ericsson Satio, Sony Ericsson Vivaz and Sony Ericsson Vivaz Pro. Used as the basis for Symbian^1, the first Symbian platform release. The release is also better known as S60 5th edition, as it is the bundled interface for the OS.
Symbian OS 9.5
Released as Free and Open Source Software
The Symbian Foundation was announced in June 2008 and came into existence in 2009. Its objective was to publish the source for the entire Symbian platform, including Symbian OS and Series 60 platform, under the OSI– and FSF-approved Eclipse Public License (EPL). The release of the Symbian platform deprecated Symbian OS as a standalone product.
Symbian Ltd. was purchased by Nokia in December 2008, transitioning principal OS and user interface development to Nokia.
Symbian^3 is a big improvement over previous S60 5th Edition and features single touch menus in the user interface, as well as new Symbian OS kernel with hardware-accelerated graphics; further improvements will come in the first half of 2011 including portrait qwerty keyboard, a new browser and split-screen text input. Nokia announced that updates to Symbian^3 interface based on Qt framework will be delivered gradually, as they are available; Symbian^4, the previously planned major release, is now discontinued.
Devices that use Symbian OS
- The Ericsson R380, in 2000, was the first commercially available phone based on Symbian OS. As with the modern “FOMA” phones, this device was closed, and the user could not install new C++ applications. Unlike those, however, the R380 could not even run Java applications, and for this reason, some have questioned whether it can properly be termed a ‘smartphone’.
- The UIQ interface was used for PDAs such as Sony Ericsson P800, P900, P1, W950 and the RIZR Z8 and RIZR Z10.
- The Nokia S60 interface is used in various phones, the first being the Nokia 7650. The Nokia N-Gage and Nokia N-Gage QD gaming/smartphone combos are also S60 platform devices. It was also used on other manufacturers’ phones such as the Siemens SX1 and Samsung SGH-Z600. Recently, more advanced devices using S60 include the Nokia 6xxx, the Nseries (except Nokia N8xx and N9xx), the Eseries and some models of the Nokia XpressMusic mobiles.
- The same phone as the Nokia 6600 was Siemens SX1 with Symbian s60 but it has had FM radio, an special keyboard around the display from both left and right side. It was the best of Siemens for a long time.
- The Nokia 9210, 9300 and 9500 Communicator smartphones used the Nokia Series 80 interface.
- The Nokia 7710 is the only device currently using the Nokia Series 90 interface.
- Fujitsu, Mitsubishi, Sony Ericsson and Sharp developed phones for NTT DoCoMo in Japan, using an interface developed specifically for DoCoMo’s FOMA “Freedom of Mobile Access” network brand. This UI platform is called MOAP “Mobile Oriented Applications Platform” and is based on the UI from earlier Fujitsu FOMA models.
Symbian OS was 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 adopted a UNIX-style capability model (permissions per process, not per object). Installed software is theoretically 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. Developers also have the option of self-signing their programs. However, the set of available features does not include access to Bluetooth, IrDA, GSM CellID, voice calls, GPS and few others. Some operators have opted to disable all 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 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.
Bypassing Platform Security
Symbian OS 9.x devices can be hacked to remove the platform security introduced in OS 9.1 onwards, allowing users to execute unsigned code. This allows alteration of system files, and access to previously locked areas of the OS. The hack was criticised by Nokia for potentially increasing the threat posed by mobile viruses as unsigned code can be executed.
Developing on Symbian OS
As of 2010, the SDK for Symbian is standard C++, using Qt. It can be used with either Qt Creator, or Carbide (the older IDE previously used for Symbian development). A phone simulator allows testing of Qt apps. Apps compiled for the simulator are compiled to native code for the development platform, rather than having to be emulated.
It is also possible to develop using Symbian C++, although it is not a standard implementation. Prior to the release of the Qt SDK, this was the standard development environment. There were multiple platforms based upon Symbian OS that provided SDKs for application developers wishing to target Symbian OS devices – the main ones being UIQ and S60. Individual phone products, or families, often had 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 and the Symbian platform use a new ABI and required a different compiler – a choice of compilers is available including a newer version of GCC (see external links below).
Unfortunately, Symbian C++ programming has a steep learning curve, as Symbian C++ requires the use of special techniques such as descriptors, active objects and the cleanup stack. This can make even relatively simple programs harder to implement than in other environments. Moreover, it was questionable whether these techniques, such as the memory management paradigm, were actually beneficial. It is possible that the techniques, developed for the much more restricted mobile hardware of the 1990s, simply caused unnecessary complexity in source code because programmers are required to concentrate on low-level routines instead of more application-specific features. These issues however are no longer the case when using standard C++, with the Qt SDK.
Symbian C++ programming is commonly done with an IDE. For earlier 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 four different versions: Express, Developer, Professional, and OEM, with increasing levels of capability. Fully 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.
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. On 13 March 2007 AppForge ceased operations; Oracle purchased the intellectual property, but announced that they did not plan to sell or provide support for former AppForge products. Net60, a .NET compact framework for Symbian, which is developed by redFIVElabs, is sold as a commercial product. With Net60, VB.NET and C# (and other) source code is compiled into an intermediate language (IL) which is executed within the Symbian OS using a just-in-time compiler. (As of 18/1/10 RedFiveLabs has ceased development of Net60 with this announcement on their landing page: ”At this stage we are pursuing some options to sell the IP so that Net60 may continue to have a future”.)
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 was available.
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 S60i phones can also run Python scripts when the interpreter Python for S60 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.
Once developed, Symbian 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, Bluetooth or on a memory card. An alternative is to partner with a phone manufacturer and have the software included on the phone itself. Applications must be Symbian Signed for Symbian OS 9.x in order to make use of certain capabilities (system capabilities, restricted capabilities and device manufacturer capabilities). Applications not using these capabilities (including only requiring user capabilities) can instead be self-signed for free. There are various hacks, which allow installing unsigned programs with any capabilities to Symbian OS 9.x. Nokia also plan to reduce the cost for Symbian Signed to zero.
Resource : en.wikipedia.org/wiki/Symbian_OS