The cat is finally out of the bag as Apple announced the iPhone OS 4.0 update, here we have a list of most important new features and updates introduced in the Apple mobile OS platform complete with a video walk-through.

Apple iPhone OS 4.0 Features :

• Multitasking - The most wanted feature is finally here, allowing users to simultaneously run multiple applications the functionality requires user to double tap the Home button which brings up a task switcher. Select your app of choice and it pops in foreground.
• App Folders - Again a much needed feature to group those applications and game icons category-wise, stores upto 2,000 apps.
• iAd advertising - Apple's very own mobile advertising platform.
• iBooks - Now, read iBooks on your iPhone's and iPod's.
• Fast app switching - A new concept in background app switching, instead of having everything running in background a state is saved so you can quickly and easily switch back to it.
• Game center - Centralized gaming service letting users connect to others wanting to play games.
• Local Notifications - system for allowing background applications to communicate with user.
• Updated mail app - Now supports multiple Exchange accounts and threaded messages.
• 5x digital zoom - Digital zoom from your camera.
• Spell Check
• User-defined wallpaper
• Playlist creation and nested playlists.
• Enterprise features, including remote device management and wireless app distribution.
• 1,500 new APIs for developers.
• Background audio support
• In-app SMS support.

Sadly, not all features of the new iPhone OS 4.0 will be supported by every model - only iPhone 3GS and iPod touch 3rd generation will support everything most notably multitasking.

Information and Image Credits To : Gizmodo and Endgadget