Symbian is both a pioneer among the smartphone operating systems and a product without a clear future. Finland’s Nokia, the world’s leading mobile phone maker, has announced plans to move away from its own Symbian system as the primary software for its smartphones.

The company will instead be marketing devices using Windows Phone from Microsoft. During the transition phase, though, Nokia is still hoping to sell more than 150 million Symbian smartphones.

The current range of models reflects Nokia’s desire to appeal to a range of target audiences. The N8 is the company’s multimedia flagship, with a 12-megapixel camera and HDMI output for direct connection to an HDTV. The C7 is the convenient do-it-all device, with a touchscreen and few physical buttons.

Then there are two models aimed at business customers: the E7 with its slide-out QWERTY keyboard and the E6 with a keyboard directly under the monitor. The X7 is aimed at a younger audience, with better game playing on the larger monitor (4 inches) and quick access to the online network.

Nokia is also betting on its free navigation software as a powerful draw. The company’s devices come preloaded with maps for up to 200 countries, showing routes for drivers and pedestrians. Nokia also recently added in 3D views as well. The acquisition of mapmaking specialists Navteq, a transaction costing millions, ensured that the Finns have all the components for navigation in-house.

Symbian mobiles are also designed to allow users to compose their own start page, with widgets displaying new email messages and social media posts. Unlike competitor Apple, Nokia promises compatibility with Flash videos as well. The devices come in a solid metal housing that sits well in the hand.

But one question remains: Why have Nokia’s Symbian telephones sold so poorly in recent years? After all, new company CEO Stephen Elop felt it necessary to change horses midstream and switch to the Microsoft software.

Industry experts have repeatedly distilled the problem down to a simple formula: Nokia has solidly built devices — and software that can’t keep up with competitors like Apple’s iOS software for the iPhone and iPad or Google’s Android operating system. The rise of Android phones was the straw that broke the camel’s back for Nokia’s smartphone strategy.

The weaknesses of Symbian become clear to customers when they try to type in a Google search or WLAN access codes on the virtual phone keyboard, or when they try to search through menus that sometimes seem to have no rhyme or reason. “There are too many settings in too many different places,” says industry watcher Michael Gartenberg.

The decision to move to Windows Phone doesn’t mean a sudden death for Symbian though. Nokia has in fact pledged to continue developing it. The current Symbian update includes better controls for the touchscreen and the ability to run multiple apps at once. In total some 250 new functions are included.

Users can acquire apps from Nokia’s proprietary Ovi platform, which sees more than five million downloads each day, the company reports. That said, it has significantly fewer programs available than Apple’s App Store or the Android market. That is considered a central competitive disadvantage for the Symbian platform.

The strengths and weaknesses of Symbian are ultimately also rooted in the past. The operating system traces its ancestry to EPOC, developed by British PDA pioneer Psion in 1997 for devices with a mini—keyboard and stylus control on the screen.

The system was robust, could handle multitasking (the ability to run multiple applications in parallel at once), and the exchanging of data using a clipboard. A simple programming language called OPL supported the development of a variety of small applications, although they were not yet known as apps.

The Symbian Group was founded in 1998 to oversee the further development of EPOC, with the goal of creating a system for devices that combine the functionality of handheld computers and mobile telephones — the central tenet of today’s smartphones.