A Google developer, formerly on the Android team, provides a detailed, fair, and clear explanation of how iPhone OS 4 multitasking will work. Robert Love explains the difference between true background application multitasking and Apple's limited set of APIs that let certain processes continue to operate in the background. He also differentiates serialization (quitting an app while preserving its state precisely) and true background operations. follow link
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Google Developer Explains iPhone OS 4 Multitasking