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Now that you have seen the basics of Objective-C and its use with object-oriented programming, you can start to write code. As noted previously, today the overwhelming majority of Objective-C programs are written for use on Mac OS X and iOS; most of them are written using Xcode, Apple’s development tool.
The simplest way to get Xcode is from the Mac App Store. The price is right (free), and the development tool is automatically installed right after it’s downloaded. Xcode and its supporting files are installed by default in a new root-level folder called Developer on your hard disk. This means that they are available to all users on your computer. Each user’s files are stored separately in their own directory or on a shared server, as you find out later in this hour.