Symbian Designs
Symbian OS is an operating
system with associated libraries, user interface frameworks and reference
implementations of common tools, produced by Symbian Ltd.. It is a descendant of
Psion's EPOC.
A D V E R T I S E M E N T
Symbian is currently owned by
BenQ, Ericsson, Panasonic, Nokia, Siemens AG and Sony Ericsson.
Design
There are a number of smartphone user interface platforms based on Symbian
OS, including open platforms UIQ, Nokia's Series 60, Series 80 and Series 90 and
closed platforms such as that developed for NTT DoCoMo's FOMA handsets. This
adaptability allows Symbian OS to be used on smartphones with a variety of form
factors (e.g. clam-shell or "monoblock"/"candybar", keypad- or pen-driven).
Symbian OS, with its roots in Psion Software's EPOC (which itself had
similarities to the internals of VMS, a grown-up POSIX compatible operating
system for mini-computers in the 1980s) 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. Correct use of these
techniques helps ensure longer battery life.
All of this makes Symbian OS's flavour of C++ very specialised, with a steep
learning curve. However, many 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.
Competition Symbian OS competes with other mobile operating systems, such as Windows
Mobile, Palm OS, and Linux. It also competes with the embedded operating systems
used on lower-end phones, such as NOS and OSE, which tend to be maintained by
the phone companies themselves. Symbian OS' major advantage over these embedded
operating systems is its modularity - there is runtime linking between
dynamically linked shared libraries (DLLs, see dynamic linking) on the device,
and an emphasis on plug-in architectures. This makes complex phones quicker to
develop, though this is sometimes offset by the complexity of Symbian OS C++ and
the awkwardness of going to another company for an OS (instead of doing it
in-house).
The advantages over other 'open' OS competitors (such as Linux and Windows
Mobile, the last one is not Open Source) are more debatable. Phone vendors and
network operators like the customisability of Symbian OS relative to Windows.
This customisability, though, makes integrating a Symbian OS phone more
difficult. It's possible that Linux goes too far in the other direction, and is
simply too hard to make a phone from at the moment. Symbian OS's ground-up
design for mobile devices should make it more power- and memory-efficient, as
well as being flexible.
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, of course, the average mobile phone user shouldn't have to worry
about such things, so Symbian OS 9 is adopting 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. Developers can apply to have their software signed via the
Symbian Signed program.
Openness A common question is whether Symbian OS is "open". It is not open in the
sense of Open Source software - the source code is not publicly available.
However, nearly all the source code is provided to Symbian OS phone
manufacturers and many other partners. Moreover, the APIs are publicly
documented and anyone can develop software for Symbian OS. This contrasts with
traditional embedded phone operating systems, which typically cannot accept any
aftermarket software except Java applications.
Symbian is also open in terms of the Open Standards it supports.
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