Apple released updates to the two branches of its mobile operating system, addressing the way signal bars are displayed on the iPhone and fixing bugs on the iPad. iOS 4.0.1 for iPhone, and iOS 3.2.1 for iPad are both available now.

iOS 4.0.1 for iPhone -- iOS 4.0.1 primarily modifies the formula used to determine cellular signal strength. Apple promised this update at the beginning of the month in response to reception problems caused by bridging the iPhone 4's external antennas when holding the phone (see "iPhone Signal Strength Sets Bars Too High," 2 July 2010). The change doesn't address the signal issue; instead, it allegedly reports the signal strength more accurately. Apple did, however, increase the size of the first three bars to make them more prominent (and, no doubt, to make people feel better about the reduced reception).

The update also quietly addresses sync issues with Exchange ActiveSync Mail, Contacts, or Calendars that may cause syncing to fail or go slowly. Some Exchange Server administrators may also notice their systems running more slowly due to this problem. The update resolves these issues by installing a new configuration file that increases the amount of time an iOS 4 device will wait for a sync request response from the Exchange Server.

Apple has released a beta of iOS 4.1 to developers, and held a special iPhone 4 press conference to address the signal concerns that have gained significant media attention (see "Apple Responds to iPhone 4 Antenna Issue," 16 July 2010). Even a United States Senator, Charles Schumer (D-NY), weighed in.

The update works with the iPhone 4, iPhone 3GS, and iPhone 3G. The original iPhone is not capable of running iOS 4, and the iPod touch remains at version 4.0.

iOS 3.2.1 Software Update for iPad -- Both models of the iPad (Wi-Fi and 3G) gain a handful of fixes in iOS 3.2.1, which Apple calls out as follows:

• Improved Wi-Fi connectivity
• Fixed an issue that could prevent copy and paste of single-page PDF attachments in Mail
• Addressed an issue that could cause video playback to freeze
• Improved reliability of video-out when using iPad Dock Connector to VGA Adapter
• Added Bing as an option for Safari's search field

Both updates are available from within iTunes: connect your device, select it in the sidebar, and click the Check for Update button. iOS 4.0.1 is a 579.3 MB download; iOS 3.2.1 is a 456.9 MB download. (The updates are full images of the iOS, not just patches needed to update the operating system, which explains their large sizes. This approach enables easy restoration of the software within iTunes in case something goes wrong with the device.)