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Fraser Speirs - Blog - Misconceptions About iOS Multitasking

Let me wrap this up by giving you a quick summary:

  1. If someone tells you that all the apps in the multitasking bar are running, using up memory or sucking power, they are wrong.
  2. When you hit the home button, an app moves from Active to Background and quickly to the Suspended state where it no longer uses CPU time or drains power.
  3. An app may request an additional 10 minutes of Background running to complete a big task before becoming Suspended.
  4. If memory is becoming scarce, iOS will automatically move Suspended apps into the Not Running state and reclaim their memory.
  5. Five classes of apps - audio, GPS, VOIP, Newsstand and accessory apps - and some built-in apps such as Mail may run indefinitely in the background until they complete their task.

Great post explaining iOS background processing and why you don’t need to go around removing apps from the multitasking bar.