The Symbian OS is used for cell phone/smart phone manufactures such as Nokia and Sony Ericsson. In 2005, Canalys estimated that the Symbian OS had a 72% market share. In comparison, Microsoft PocketPC and MS Smartphone had a mere 8% market share. RIM also had an 8% share, while PalmSource and Linux had a mere 6 and 5% respectively.
According to Red Five Labs, there are currently there are a wide variety of languages available for the Symbian OS. These include Java, Python, Ruby and Adobe Flash, though "the most powerful and likely language used is the Symbian C++ language".
Red Five Labs is currently in the process of bringing the .NET Compact Framework to the Symbian OS under the name Net60. If they are successful, it opens a huge market for .NET developers wishing to target mobile devices.
As the name implies, Red Five Labs are currently targeting S60 3rd Edition devices. S60 3rd Edition is Nokia's user interface SDK for Symbian 9.1. In 1995, the S60 series alone accounted for 58% of the entire market share, with the other 14% being split among the Series 80/90, UIQ, and MOAP SDKs.
A beta of Net60 is currently available by contacting Red Five Labs.