IOS 4

iOS 4 (codenamed "Apex") was the 4th major release of iOS designed and developed by Apple for the iPhone, iPod touch and iPad, being the successor to iPhone OS 3
==Features==
===New features===
iOS 4 was developed for the iPhone 3G, 2nd-generation iPod touch, and 1st-generation iPad and later. The update was free and included a multitude of new features. The features included, but were not limited to:
*Multitasking
*Folder organization
*Multiple mail boxes
*iBooks
*Support for iMovie (available in the App Store)
*Creation of music playlists
*5x digital zoom for camera (iPhone 4 and iPod touch (4th gen) only)
*LED flash (iPhone 4 only)
*Tap-focus for video
*Picture identification
*Home screen wallpaper
*Ability to "gift" apps
*Spell checking
*Bluetooth keypad
*Ability to rent movies
*Game Center
*FaceTime (iPhone 4 and iPod touch (4th gen) only)
*Personal hotspot (iPhone 4 only) 
==Support==
*The 1st and 2nd-generation iPads, 3rd and 4th-generation iPod touches, iPhone 3GS, and iPhone 4 were fully supported.
*The iPhone 3G and 2nd-generation iPod touch had limited support, which was discontinued after version 4.2.1.
*The 1st-generation iPhone and iPod touch were no longer supported by any version of iOS 4.
===Limitations on older models===
Some features were disabled on older models due to hardware limitations, eventually leading Apple to stop supporting them entirely after version 4.2.1:iOS 4.3 Drops Support For iPhone 3G & Second Generation iPod Touch by Mr. EX, iPhone in Canada. 2011-01-12.
*Compass (unavailable for iPhone 3G and 2nd-generation iPod touch)
*Game Center (unavailable for iPhone 3G)
*Home screen wallpaper (unavailable for iPhone 3G and 2nd-generation iPod touch)Steve Jobs on Lack of Custom Wallpapers in iOS 4 for iPhone 3G, by Eric Slivka, MacRumors, 2010-06-22
*Multitasking (unavailable for iPhone 3G and 2nd-generation iPod touch)
*Nike + iPod (unavailable for iPhone 3G)
*Voice Control (unavailable for iPhone 3G and 2nd-generation iPod touch)
===Release history===
Version	Build 	Release date	Notes
4.0 	8A293 	2010-06-21 	First release for iPhone 4 (GSM).
4.0.1 	8A306 	2010-07-15 	Signal bar calculation adjusted to account for "Death grip" issues.
4.0.2 	8A400 	2010-08-11 	Security fix for PDF vulnerability.
4.1 	8B1178B118 	2010-09-08 	First release for 4th-generation iPod touch.
4.1.1 	8B119 	 	
4.2 	8C134 	2010-11-01 	Golden master only released to developers.iOS 4.2 GM Download Available Now by Manish Patel, OS X Daily. 2010-11-01.Apple Releases iOS 4.2.1 Golden Master to Developers by Eric Slivka, MacRumors. 2010-11-18.
4.2.1 	8C1488C148a	2010-11-22 	First version to support iPads.Last update for iPhone 3G and iPod touch (2nd gen).
4.2.2 	8C150 	2010-11-22 	Builds used for 2nd-generation Apple TV.
4.2.3 	8C152 	 	Builds used for 2nd-generation Apple TV.
4.2.4 	8C154 	2010-12-14 	Builds used for 2nd-generation Apple TV.
4.2.5 	8E128 	2011-01-11 	First release for iPhone 4 (CDMA) with Wi-Fi hotspot support.
4.2.6 	8E200 	2011-01-31 	Wi-Fi hotspot bug fixes for iPhone 4 (CDMA).
4.2.7 	8E303 	2011-04-14 	FaceTime and cellular bug fixes for iPhone 4 (CDMA).
4.2.8 	8E401 	2011-05-04 	Location bug fixes for iPhone 4 (CDMA).
4.2.9 	8E501 	2011-07-15 	Security update for iPhone 4 (CDMA).
4.2.10 	8E600 	2011-07-25 	Security certificate update for iPhone 4 (CDMA).
4.3 	8F1908F191 	2011-03-04 	Added Wi-Fi hotspot and iTunes home sharing.First release for iPad 2.
4.3.1 	8G4 	2011-03-25 	Bug fixes for iPhone and iPod touch models.
4.3.2 	8H78H8 	2011-04-14 	FaceTime and cellular bug fixes for iPad 2.FaceTime and cellular bug fixes for iPad 2 (CDMA).
4.3.3 	8J2 	2011-05-04 	Location bug fixes for iPhone 3GS, iPhone 4 (GSM), iPod touch (3rd and 4th gen), iPad (1st and 2nd gen).
4.3.4 	8K2 	2011-07-15 	Security update for iPhone 3GS, iPhone 4 (GSM), iPod touch (3rd and 4th gen), iPad (1st and 2nd gen).
4.3.5 	8L1 	2011-07-25 	Security certificate update for iPhone 3GS, iPhone 4 (GSM), iPod touch (3rd and 4th gen), iPad (1st and 2nd gen).
===End of support===
With the announcement of iOS 5 on June 6 at the 2011 Worldwide Developers Conference, owners of the iPhone 3GS, iPhone 4, iPod touch (4th generation), and iPad 2 were concerned about the level of support that their devices would continue to receive (see List of unsupported firmware). The final updates were released on July 25, 2011.
iOS 4 continued to be supported until October 12, 2011, when it was superseded by the release of iOS 5.0, which introduced iCloud services.
==Trivia==
* This was the first major release to drop support for some devices.
* This is the first iOS to introduce the home screen wallpaper.
* This is the first iOS to to use multitasking.
* This is the last iOS to feature the iPod app.
* This is the last iOS to have the Mona Lisa wallpaper on Settings.
==References==
==External links==
*iOS 4 Software Update at Apple (archived 2010-06-25)
*iOS 4 at the BetaWiki
*Firmware Keys/4.x at The iPhone Wiki
* at Wikipedia
Category:2010 introductions
Category:Discontinued Apple software