Downloading and Installing Xcode
The App Store and Developer Program versions of Xcode are different—sometimes significantly different—and they’re installed in different ways. Before you get started with downloading and installation, let’s look at a critical element of Xcode, the SDK (Software Development Kit).
Xcode is a continual work in progress. The versions of iOS it supports change with almost every release, but Apple also varies key features without notice, and delivery and installation options also change. The information that follows is valid for the public release of Xcode 4.3 for iOS 5.1. Don’t be surprised if some of the details have changed again by the time you read this.
Understanding SDKs and betas
Xcode has two main components. The current toolset includes the tools you use to edit, build, test, and distribute apps. Xcode is a fairly mature application now, so these tools change relatively slowly.
As iOS develops, new features are added and old features become obsolete. The other component in Xcode is called the SDK (Software Development Kit), and it manages this information.
Internally, the SDK is a collection of files and supporting documentation that defines all the features in a single version of iOS. Whenever iOS is updated, Apple releases a new version of Xcode with an updated SDK.
This seems simple, but there are complications. Basically, Xcode is always ...