Event-driven programming: Difference between revisions
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#REDIRECT [[:Category:Programming paradigm/Event-driven]] |
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[[Category:Programming Paradigms]]'''Event-driven programming''' is a programming paradigm or else a system architecture which decomposes the program into a set of event handlers. The primary source of the events is the hardware I/O. This includes timer events as well. The secondary source is the events signaled by the software. |
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The opposite to event-driven is polling architecture. Though both actually respond to an event in order to handle it, "event-driven" usually refers to the apparently asynchronous way the handler is called and to an encapsulation of the handler in the code, usually in the form of a subprogram. |
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The paradigm mixes [[declarative programming|declarative]] and [[imperative programming|imperative]] approaches on the event handler and emitter sides correspondingly. |
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Event-driven programming does not necessarily imply [[concurrent programming]]. In fact, very often events are handled synchronously on the context of a single [[task]]. Furthermore event-driven architectures were used in the past as a substitute for proper multitasking support, for example in [[Windows]] and MS-DOS prior to 95 and NT. |
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In a truly multitasking environment event-driven programming is exposed to serious problems, especially to deadlocks. To other problems belong: |
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* unpredictable, often poor, behavior with respect to the response time and stack memory use; |
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* complexity of the arguments and results passing, especially between multiple tasks; |
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* handlers composition. Though some event-driven systems provide tools for routing, filtering events, chaining handlers etc; |
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* low abstraction level. (This is usually alleviate when an even-driven architecture is wrapped into an [[object-oriented programming|OO model]]). |
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Event-driven programming is quite popular in [[GUI]] design. Many [[GUI]] widget libraries have event-driven architecture. It is also used in database programming in the form of [http://en.wikipedia.org/wiki/Database_trigger triggers]. In systems programming hardware communication is predominantly event-driven per hardware nature. |
Latest revision as of 19:46, 17 August 2009
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