Symbian OS Layers

Symbian OS can be run on devices with different screen sizes. The majority of the features of the OS are screen size independent and also user input (touchscreen, pen, keypad, etc.) independent. All these features amount to 80% of the OS and are known as the Symbian Platform or Generic Technology (GT). Symbian is wholly responsible for these parts of the system.

The breakdown of the Symbian Platform layers is as follows:

• Symbian Application Engines (20%) - These allow access to built in functionality such as contacts, calender information, agenda, etc. Engines concern themselves with the data only and now with how it will be presented.
• Symbian System Layer (55%) - This layer contains the bulk of the OS APIs and provides functionality from string handling to event scheduling within an application such as telephony server, socket server, DBMS server, etc.
• Kernel (5%) - This layer is not directly accessible from the user programs. This layer contains the kernel, device drivers, file server, etc. Ekern.exe is the kernel along with Euser.lib and Euser.dll. Device drivers maybe the logical device drivers (LDD) or the physical device drivers (PDD).

The remaining 20% of the Symbian OS is concerned with the UI design. This can be very specific to a perticular device, examples of which are shown on the slide. Either Symbian or the licensee can be responsible for this layer.

This modular approach facilitates porting between different Symbian OS device types. For a given Symbian Platform version, only the UI and the base (kernel and device driver) layers be ported.