Important: This version of Start Developing iOS Apps Today has been retired. The replacement version provides a new, more streamlined walkthrough of the basics. For information covering the same subject area as this page, please see "iOS Technologies".
An app consists of code that you write and frameworks provided by Apple. A framework contains a library of methods that your app can call. More than one app can access a framework library at the same time.
Any app that you develop links to multiple frameworks. You can take advantage of a framework through its application programming interface (API). The API, published in header files, specifies the available classes, data structures, and protocols. Apple writes frameworks that anticipate the basic features you might want to implement. You should use frameworks both to save time and effort and to make sure your code is efficient and secure. The system frameworks are the only way to access the underlying hardware.
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