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AppleScript and Scriptable Applications

AppleScript is a scripting language that makes possible direct control of scriptable applications and scriptable parts of the Mac OS (such as the Finder). The AppleScript language doesn’t supply an exhaustive or a task-specific terminology. Instead, it defines common commands, such as get, set, make, and delete, which can be applied to a wide variety of objects or their properties in a scriptable application. Scriptable applications define additional terms as needed for their unique operations.

A scriptable application is one that makes its operations and data available in response to AppleScript messages, called Apple events. An Apple event is a kind of interprocess message that can specify complex operations and data. Apple events make it possible to encapsulate a high-level task in a single package that can be passed across process boundaries, performed, and responded to with a reply event.

A scriptable application specifies the set of scripting terms it understands and provides information that AppleScript uses to compile scripts that use those terms. When a user executes a script that targets the application, Apple events are sent to the application. Apple events can also be sent by other applications and by the Mac OS.

Applications handle Apple events by registering with the Apple Event Manager for the events they expect to receive and by supplying handler routines to process the events. Cocoa scripting simplifies this process by automatically registering and responding to Apple events your application can handle, based on the scriptability information you supply. That means you don't need to write low-level code to interact with Apple events and the Apple Event Manager.

AppleScript and Apple events are built on the Open Scripting Architecture (OSA), which is described in Open Scripting Architecture in AppleScript Overview.

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