Introduction

This document provides information about features that were introduced in different versions of iOS and that affect the development of iOS apps. This document describes only features that affect the development of iOS apps. It does not include user-level features unless there is an aspect of the feature that affects app development. It also does not specifically address minor OS updates that include only bug fixes (and no new features). For additional information about a specific release, you should also see the corresponding release notes.

In addition to describing the new features for each iOS release, this document attempts to provide insight as to how and when you might use those features in your own software. Wherever possible, this document also provides links to other Apple conceptual and reference documentation for that feature. For a complete list of features you can use in your iOS apps, see iOS Technology Overview.

Organization of This Document

This document includes the following articles:

• “iOS 6.1” describes the new and updated features in iOS 6.1.

• “iOS 6.0” describes the new and updated features in iOS 6.0.

• “iOS 5.1” describes the new and updated features in iOS 5.1.

• “iOS 5.0” describes the new and updated features in iOS 5.0.

• “iOS 4.3” describes the new and updated features in iOS 4.3.

• “iOS 4.2” describes the new and updated features in iOS 4.2.

• “iOS 4.1” describes the new and updated features in iOS 4.1.

• “iOS 4.0” describes the new and updated features in iOS 4.0.