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Symbian OsSymbian OS is an operating system with associated libraries, user interface frameworks and reference implementations of common tools, produced by Symbian. It is a descendent of Psion's EPOC. Symbian is owned by Ericsson, Panasonic, Nokia, Samsung, Siemens and Sony Ericsson. There are multiple user interface flavours that use the Symbian OS, such as UIQ and Nokia's Series 60. The adaptability of the user interface enables the use of Symbian OS on various form-factors of hand-held devices: clam-shell or tablet, keyboard and/or pen, PDA or mobile phone, and others. Symbian OS is structured like many desktop operating systems, with pre-emptive multitasking, multithreading and memory protection. Symbian OS's major advantage is the fact that it was built for handheld devices with limited resources that may be running for months or years. There is a strong emphasis on conserving memory, using Symbian-specific programming idioms such as descriptors and a cleanup stack. Together with other techniques, these keep memory usage low and memory leaks rare. 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. Without using these techniques properly, an application can wear down the battery of a phone in just a couple of hours; with them, the battery lasts for a week. All of this makes Symbian OS's flavour of C++ very specialised, and difficult to program. However, Symbian OS devices can also be programmed in OPL, Python, Visual Basic, Simkin and Perl - together with the J2ME and Personal Java flavours of Java. The current Symbian OS is derived from the EPOC32 operating system, which was used in Psion Series 5, Revo, Sienna, and NetBook PDAs and originally developed by Psion Software. The Symbian OS has since gone though many revisions. In 2004 the first worm for mobile phones using Symbian OS, Cabir, was developed, which used Bluetooth to spread itself to nearby phones. Devices that have used the Symbian OS External links
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