At a high level, the process for creating an iPhone application is similar to that for creating a Mac OS X application. Both use the same tools and many of the same basic libraries. Despite the similarities, there are also significant differences. An iPhone is not a desktop computer; it has a different purpose and requires a very different design approach. That approach needs to take advantage of the strengths of iOS and forego features that might be irrelevant or impractical in a mobile environment. The smaller size of the iPhone and iPod touch screens also means that your application’s user interface should be well organized and always focused on the information the user needs most.

iOS lets users interact with iPhone and iPod touch devices in ways that you cannot interact with desktop applications. The Multi-Touch interface reports on each separate finger that touches the screen and making it possible to handle multifinger gestures and other complex input easily. In addition, built-in hardware features such as the accelerometers, although present in some desktop systems, are used more extensively in iOS to track the screen’s current orientation and adjust your content accordingly. Understanding how you can use these features in your applications will help you focus on a design that is right for your users.