Event (computing)

In computing, an event is an action or occurrence recognised by software that may be handled by the software. Computer events can be generated or triggered by the system, by the user or in other ways. Typically, events are handled synchronously with the program flow, that is, the software may have one or more dedicated places where events are handled, frequently an event loop. A source of events includes the user, who may interact with the software by way of, for example, keystrokes on the keyboard. Another source is a hardware device such as a timer. Software can also trigger its own set of events into the event loop, e.g. to communicate the completion of a task. Software that changes its behavior in response to events is said to be event-driven, often with the goal of being interactive.

Description

Event driven systems are typically used when there is some asynchronous external activity that needs to be handled by a program; for example, a user who presses a button on his mouse. An event driven system typically runs an event loop, that keeps waiting for such activities, e.g. input from devices or internal alarms. When one of these occurs, it collects data about the event and dispatches the event to the event handler software that will deal with it.