What are the features of iphone OS4?

iphone iOS 4 brings a handful of crucial features, like multitasking and aunified e-mail in-box, that Apple's products have lacked for far too long .

Your primary access point is a multitasking menu that's accessible by double tapping the Home button. Once there, you'll see a list of currently running applications along the bottom of the display that you can scroll through using a sideways finger swipe.

The pop-up menu shows only four apps at a time, toopen a running app, scroll though the menu and tap its icon once. When you're ready to end an app, first use a long press on the related icon and then click the tiny delete icon in the top left corner.

To get the full knowledge about its 100+ features I think you should look it on the following websites as I can not mention all of the 100 here. The websites names are: reviews.cnet, gizmodo, apple and tuaw.