Power up your iTunes 9.2 and you will be prompted for an update. Here is a list of changes provided by Apple

iOS 4 Software Update

This update contains over 100 new features, including the following:

• Multitasking support for third-party apps*
  – Multitasking user interface to quickly move between
     apps
  – Support for audio apps to play in the background
  – VoIP apps can receive and maintain calls in the
     background or when device is asleep
  – Apps can monitor location and take action while
     running in the background
  – Alerts and messages can be pushed to apps using
     push and local notifications
  – Apps can complete tasks in the background
• Folders to better organize and access apps
• Home screen Wallpaper*
• Mail improvements
  – Unified inbox to view emails from all accounts in one
     place
  – Fast inbox switching to quickly switch between
     different email accounts
  – Threaded messages to view multiple emails from the
     same conversation
  – Attachments can be opened with compatible third-
     party apps
  – Search results can now be filed or deleted
  – Option to select size of photo attachments
  – Messages in the Outbox can be edited or deleted
• Support for iBooks and iBookstore (available from the
   App Store)
• Photo and Camera improvements
  – 5x digital zoom when taking a photo**
  – Tap to focus during video recording**
  – Ability to sync Faces from iPhoto
  – Geo-tagged photos appear on a map in Photos
• Ability to create and edit playlists on device
• Calendar invitations can be sent and accepted wirelessly
   with supported CalDAV servers
• Support for MobileMe calendar sharing
• Suggestions and recent searches appear during a web
   search
• Searchable SMS/MMS messages**
• Spotlight search can be continued on web and Wikipedia
• Enhanced location privacy
  – New Location Services icon in the status bar
  – Indication of which apps have requested your location
     in the last 24 hours
  – Location Services can be toggled on or off for
     individual apps
• Automatic spellcheck
• Support for Bluetooth keyboards*
• iPod out to navigate music, podcasts and audiobooks
   through an iPod interface with compatible cars
• Support for iTunes gifting of apps
• Wireless notes syncing with IMAP-based mail accounts
• Persistent WiFi connection to receive push notifications*
• New setting for turning on/off cellular data only**
• Option to display the character count while composing
   new SMS/MMS**
• Visual Voicemail messages can be kept locally even if
   they have been deleted from the server**
• Control to lock portrait orientation*
• Audio playback controls for iPod and third-party audio
   apps*
• New languages, dictionaries and keyboards
• Accessibility enhancements*
• Bluetooth improvements
• Better data protection using the device passcode as an
   encryption key* (Requires full restore.)
• Support for third-party Mobile Device Management
   solutions
• Enables wireless distribution of enterprise applications
• Exchange Server 2010 compatibility
• Support for multiple Exchange ActiveSync accounts
• Support for Juniper Junos Pulse and Cisco AnyConnect
   SSL VPN apps (available from the App Store)
• More than 1,500 new developer APIs
• Bug fixes

Products compatible with this software update:
• iPhone 3G
• iPhone 3GS
• iPhone 4
• iPod touch 2nd generation
• iPod touch 3rd generation (late 2009 models with 32GB
   or 64GB)

* Requires iPhone 3GS, iPhone 4, and iPod touch 3rd generation.
** Requires iPhone 3G, iPhone 3GS, and iPhone 4. SMS/MMS messaging and Visual Voicemail require support from your wireless carrier.

For feature descriptions and complete instructions, see the user guides for iPhone and iPod touch at:
 <http://support.apple.com/manuals/iphone>
 <http://support.apple.com/manuals/ipodtouch>

For more information about iPhone and iPod touch, go to:
 <http://www.apple.com/iphone>
 <http://www.apple.com/ipodtouch>

To troubleshoot your iPhone or iPod touch, or to view additional support information go to:
 <http://www.apple.com/support/iphone>
 <http://www.apple.com/support/ipodtouch>

For information on the security content of this update, please visit this website: 
 <http://support.apple.com/kb/HT1222>

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