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Realtime

Realtime applications are those that need to respond in a timely fashion to input. Frequently, such input comes from an external sensor or a specialized input device, and output takes the form of controlling some external hardware. Examples of applications with realtime response requirements include automated assembly lines, bank ATMs, and aircraft navigation systems.

Although many realtime applications require rapid responses to input, the defining factor is that the response is guaranteed to be delivered within a certain deadline time after the triggering event.

The provision of realtime responsiveness, especially where short response times are demanded, requires support from the underlying operating system. Most operating systems don’t natively provide such support because the requirements of realtime responsiveness can conflict with the requirements of multiuser time-sharing operating systems. Traditional UNIX implementations are not realtime operating systems, although realtime variants have been devised. Realtime variants of Linux have also been created, and recent Linux kernels are moving toward full native support for realtime applications.


  

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