How does the alarm clock work on iPhone SDK 3.0? When the app has closed, the alarm clock app still runs and shows and alert message when the alarm is triggered. I know that iOS 3.0 doesn't support multitasking.
iOS 3 did not support multi-tasking it the public API available to 3rd parties. The iOS is (and always has been) a multi-tasking OS, however. Clearly Apple apps (Mail, Clock, etc.) had access to this capability before 3rd parties.