iOS 4.0.1 for iPhone、iOS 3.2.1 for iPad 釋出
Apple 釋出了iPhone 3G、iPhone 3GS 和 iPhone 4 適用的 iOS 4.0.1 Software Update 軟體更新，以及 iPad 適用的 iOS 3.2.1。
針對 iPhone 適用的 iOS 4.0.1 Software Update 軟體更新，Apple 並未有詳細的釋出事項，僅提供下列說明：
Improves the formula to determine how many bars of signal strength to display
關於訊號列顯示調整的部分，AnandTech 有一篇詳細的報導 (英文)。簡單來說，iOS 4.1 (或 iOS 4.0.1) 對於各訊號列有較佳的等寬表現。
(圖片來源：AnandTech)
The results are conclusive - Apple has dramatically changed the signal strength to signal bar mapping in iOS 4.0.1 and the iOS 4.1 beta, making the dynamic range not only much broader, but the range values for each bar much wider. The range of signals that correspond to bars three and four are the same width, and bar two is only slightly less.The cutoff value for two bars to one bar remains the same, but every other value has increased. The result is that the worst case drop of 24 dBm no longer makes all the signal bars disappear, but rather two.
還有其他適用於 iOS 3.2.1 for iPad 的修復與改善：
iOS 3.2.1 Software Update for iPad
This iOS software update for iPad contains bug fixes and improvements, including the following:
- 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
iOS 4.0.1 與 iOS 3.2.1 可透過 iTunes 取得。
