Icons for most recent program usage?

Apple iPhone - Icons for most recent program usage?

iPhone 3GS Software 4.2.1

I know there is a way to slide the four icons at the bottom of the home screen to show icons for the most recently used programs. Can anyone tell me how to do this?

iPhone Apps
Double click the Home button.

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Double click the home button should raise up the allthe "open app"

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Double click the home button. The last opened apps with appear at the bottom. You can scroll to see which others are "open" as well.

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Double-click the home button. Then the multi-tasking bar appears.

:) :) :)