Could someone explain the difference between "fast app switching" and Multitasking as executed in ios4?
When I dbl click Home, are some of the apps still running and some just available for a fast switch? How can you I tell the difference?
Multitasking is when the program continues to run in the background when you switch away from them.
"Fast App Switching" is when an app saves its state, but doesn't continue to run when you switch away from it. Next time you come into it, it quickly loads the previous state, and resumes from where you left it. Peggle is an example. If you switch away in the middle of a round, and come back the following day, you'll be in the exact same place that you were when you switched away. Some programs were able to do this before iOS4, but it took a lot of work for the developer to make that happen. iOS4 makes it really easy, but like GimmeSlack said, apps do need to be modified before they'll be able to do that.
Very few programs can continue to run in the background when you switch away from them. The basic ones are: ones that stream music (like Pandora), ones that use GPS (like RunKeeper), and ones that use VoIP (like Skype).
When you have a GPS app running in the background, you'll see a little compass pointer up by your clock.
When you have a music streaming app running in the background, you'll see a play button up by your clock.
Never used a VoIP app, but I'm sure it'll show some indicator up by the clock as well.
