Slide 6.12: Palm OS Developer Suite (cont.)   Slide 6.14: Application startup and stop   Home

Palm OS Programming Concepts

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Palm OS applications are generally single-threaded, event-driven programs. Only one program runs at a time.

1. Application Startup and Stop
Each application has a PilotMain function that is equivalent to main in C programs. To launch an application, the system calls PilotMain and sends it a launch code. The launch code may specify that the application is to become active and display its user interface (called a normal launch), or it may specify that the application should simply perform a small task and exit without displaying its user interface.

2. Event Loop
Palm OS is an event-based operating system, so Palm OS applications contain an event loop; however, this event loop is only started in response to the normal launch. Your application may perform work outside the event loop in response to other launch codes.

3. User Interface
Most Palm OS applications contain a user interface made up of forms, which are analogous to windows in a desktop application. The user interface may contain both predefined UI elements and custom UI elements.

4. Memory and Files and Databases
All applications should use the memory and data management facilities provided by the system.

5. Managers
You implement an application's features by calling Palm OS functions. Palm OS consists of several managers, which are groups of functions that work together to implement a feature. As a rule, all functions that belong to one manager use the same prefix and work together to implement a certain aspect of functionality. Managers are available to, for example, generate sounds.