|A version of the iOS operating system|
iOS 4 running on an iPhone 4.
|Closed, with open source components|
|June 21, 2010; 7 years ago (2010-06-21)|
|Proprietary EULA except for open-source components|
|iPhone OS 3|
|iOS 4 at the Wayback Machine (archived June 30, 2010)|
Limited third party application support only (4.2.1 and later)
iOS 4 is the fourth major release of the iOS mobile operating system developed by Apple Inc., being the successor to iPhone OS 3. It was announced at the company's Worldwide Developers Conference on June 7, 2010, and was released on June 21, 2010. iOS 4 is the first iOS version issued under the "iOS" rebranding, dropping the "iPhone OS" naming convention of previous versions. It was succeeded by iOS 5 on October 12, 2011.
iOS 4 introduced folders on the home screen, significantly increasing the number of apps that can be displayed. Support for custom wallpapers was also added, although limited to newer devices due to animation performance requirements. The operating system also added a multitasking feature, letting apps dealing with Internet calling, location and audio playback function in the background, whereas a similar but more restricted "Fast App Switching" technology enabled any app to be left inactive in the background while users switch to other apps. iOS 4 also added a system-wide spell checking feature, enabled iBooks on iPhone, unified the Mail inbox to combine content from different email providers, and introduced both Game Center for social gaming and FaceTime for video calling.
The iOS 4 update introduced performance and battery problems on iPhone 3G devices, with Apple investigating the matter and promising then-upcoming updates. However, the company became the subject of a lawsuit from an unsatisfied customer over the issues. Around the same time, the release of iPhone 4 and its subsequent antenna problems made Apple focus on unsuccessfully attempting to patch the issues with software updates.
Introduction and initial release
iOS 4 was introduced at the Apple Worldwide Developers Conference keynote address on June 7, 2010. Notably, it was the first iOS release to be named simply "iOS", having ditched the "iPhone OS" naming pattern of previous versions.
iOS 4 was officially released on June 21, 2010.
iOS 4.0.1 was released on July 15, 2010, as the first update to iOS 4. The update changed the method of calculating carrier signal strength for improved accuracy.
iOS 4.0.2 was released on August 11, 2010, with a fix for an exploit taking advantage of PDF file format vulnerabilities.
iOS 4.1 was released on September 8, 2010. The update included high dynamic range (HDR) technology for improved quality on photos captured with the iPhone 4, added the Game Center social gaming network, and the ability to upload high definition videos captured on the iPhone 4 to YouTube and MobileMe. It also featured bug fixes and performance improvements.
iOS 4.2.1 was released on November 22, 2010. It was the first version to bring all major iOS 4 features introduced on iPhone to iPad. Although iOS 4.2 was released to developers for testing purposes, bugs were discovered, and it was replaced by 4.2.1 for consumer release.
iOS 4.3.1 was released on March 25, 2011, with a fix for iPod Touch screen glitches, along with stability improvements for cellular connectivity on iPhone models.
iOS 4.3.2 was released on April 14, 2011, with fixes for frozen calls on FaceTime and connectivity issues on cellular models of iPad.
iOS 4.3.3 was released on May 4, 2011, to fix location bugs.
iOS 4.3.4 was released on July 15, 2011, fixing security vulnerabilities.
iOS 4.3.5 was released on July 25, 2011, with a security update to fix certificate validation.
iOS 4 raised the maximum number of home screen apps from 180 to 2,160 due to the addition of folders. These folders would automatically be named based on the containing apps' respective App Store category. The ability to add custom wallpapers to the home screen was also added, though the feature was notably absent from iPhone 3G and second-generation iPod Touch due to poor performance of icon animations.
iOS 4 introduced multitasking. The feature allowed users to switch between apps instantly by double-clicking the home button. It was implemented in such a way that did not cause excessive battery drain. Multitasking was limited to apps dealing with Internet calling, location, and audio playback, while a similar "Fast App Switching" technology meant users could leave an app and enter another, with the original app remaining in the background until the user returns.
iOS 4 introduced a spell checking feature that underlined misspelled words in red. Tapping on the word would provide a pop-up with a recommended replacement.
The Camera app could take pictures with 5 times digital zoom.
The Mail app featured a unified inbox on iOS 4, allowing users to see messages from all of their email accounts displayed together in a single inbox. It also gained support for MobileMe e-mail aliases and multiple Exchange accounts for business users.
iOS 4.1 added a new app called Game Center, an online multiplayer social gaming network, which allows users to invite friends to play games and to compare their scores on a leaderboard. It was not available on the iPhone 3G.
On iOS 4.2, specific words or phrases on a page can searched.
iPhone 3G users reported performance and battery issues after upgrading to iOS 4. Apple started an investigation of the matter in July 2010. In November, Apple was sued for the issues, with an unsatisfied customer alleging "violating the Consumer Legal Remedies Act, unfair business practices, and false and deceptive advertising", with further allegations that Apple knew its software would cause problems on older models. Apple hasn't responded to the allegations, but wrote in a reply to another unsatisfied customer in August that updates were "coming soon".
Upon its release, some iPhone 4 users reported having technical problems with the phone's antennas. Apple attempted to fix the issue with iOS 4.0.1, but failed to do so.
iPhone OS 3