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From Palm OS to Symbian OS: Making the Switch, Part 1 : Page 3

Thinking about switching from Palm OS to Symbian OS? The proliferation of smartphones has made it necessary to build many wireless applications from the operating system on up and Symbian OS seems to have this market cornered. This two part series outlines the differences between developing for Palm OS and for Symbian OS. So if you do decide to switch, you'll know what to expect.


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User Interface
Both operating systems provide developers with basic GUI components like check boxes, radio buttons, lists, scrollbars, and other components.

One important difference is that in Symbian OS the GUI framework enables developers to create applications to run on screens with different form factors, with minimal code changes.

For now, Palm OS has the more mature UI development tools such as Metrowerks IDE, CodeWarrior. Similar tools from Metrowerks for Symbian OS are being developed for both Java and C++ programmers.



UI for Quartz
Symbian OS's standard UI framework and interface is UI for Quartz (UIQ) or Thin Quartz. It provides a standard look-and-feel across all UIQ-based devices. Specifically, UIQ is meant for devices with screen sizes of 240x320 pixels (1/4 VGA), or 208x320 pixels.

Palm and Symbian's UIs look alike with a menu bar and an application space. The UIQ also has a status bar, a button bar and an application picker that is similar to Palm OS' Home. With both, only one application at a time can be on screen. With Palm OS, only one application can be active at a time. With UIQ multiple applications can run but with only one having screen control at a time.

"The real differences between Symbian OS and Palm OS' screen management come in how the applications behind the screen are constructed."

In both platforms, the UI run in an Application Space, the screen space between the Menu bar and the Status bar. In Palm OS, this space is controlled by 'Forms,' while in UIQ 'Views' are used. For a user, the two look and act the same with similar interface components like checkboxes, scrollbars, and text fields.

Superficially, they also look the same from a programmer's viewpoint. For example, user interface events are handled by the event command handler, HandleCommandL(). This is similar in concept to Palm OS' event handlers. The real differences between Symbian OS and Palm OS' screen management come in how the applications behind the screen are constructed.

Multitasking
Unlike Palm OS, Symbian OS is a multitasking operating system with multi-threading support. Every Symbian OS process can have one or more threads. These are co-coordinated by the system scheduler, which allocates thread processor access by prioritized, pre-emptive multitasking.

In smartphones, multitasking is especially valuable since users will frequently want to do such things such as downloading e-mail while talking or looking at a Web site. As 2.5G and 3G network packet data services become more common, multitasking smartphone applications will become a must.

Symbian OS also enables you to use interprocess and application communications to enable multiple processes and programs to work together. With Palm OS, this is essentially impossible.



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