The Accounts framework provides access to user accounts stored in the Accounts database. An account stores the login credentials of a particular service, such as Twitter, that can be used as authentication for the service. By implementing the Accounts framework into your app, you do not need to be responsible for storing account logins yourself. Instead, the user can grant access for your app to use their account login credentials, bypassing the need to type their username and password. If no account for a particular service exists in the user’s Accounts database, you can let them create and save an account from within your app.

The Address Book framework provides access to a centralized contacts database, called the Address Book database, that stores a user’s contacts. Applications such as Mail and Messages use this database to present information about known and unknown persons.

The Core Location framework lets you determine the current location or heading associated with a device. The framework uses the available hardware to determine the user’s position and heading. You use the classes and protocols in this framework to configure and schedule the delivery of location and heading events. You can also use it to define geographic regions and monitor when the user crosses the boundaries of those regions. In iOS, you can also define a region around a Bluetooth beacon.

The Core Bluetooth framework provides the classes needed for your iOS and Mac apps to communicate with devices that are equipped with Bluetooth low energy wireless technology.

The Message UI framework provides specialized view controllers for presenting standard composition interfaces for email and SMS (Short Messaging Service) text messages. Use these interfaces to add message delivery capabilities without requiring the user to leave your app.

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StoreKit enables users to embed a store in their app. It also process financial transactions associated with the purchase of content and services.

The UIKit framework (UIKit.framework) provides the crucial infrastructure needed to construct and manage iOS apps. This framework provides the window and view architecture needed to manage an app’s user interface, the event handling infrastructure needed to respond to user input, and the app model needed to drive the main run loop and interact with the system.

The iOS SDK provides Facebook Platform support for iOS apps

The Map Kit framework provides an interface for embedding maps directly into your own windows and views. This framework also provides support for annotating the map, adding overlays, and performing reverse-geocoding lookups to determine placemark information for a given map coordinate.