What private frameworks or functions are providing multitasking?

What private frameworks or functions are providing multitasking? I want to create a background process in 开发者_JS百科my app.I'm using sdk 3.0 I know it can be implemented because maybe everybody used an alarm clock on your Iphone.

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The iOS security sandbox, on stock OS devices, will prohibit or kill any background process that an app attempts to create.

Alarm apps usually stay in the foreground, or depend on notifications to the user (not the app).