Real time

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The term real-time ( English real-time ) characterizes the operation of information technology systems can deliver the specific outcomes reliably within a predetermined time, for example in a fixed time frame.


The definition of the standard DIN 44300 (information processing), part 9 (processing sequences), which has since been replaced by DIN ISO / IEC 2382, was:

Real-time is understood to mean the operation of a computing system in which programs for processing data are always ready for operation, in such a way that the processing results are available within a specified period of time. Depending on the application, the data can be distributed at random or at predetermined times. "

The hardware and software must ensure that there are no delays which could prevent compliance with this condition. The data does not have to be processed particularly quickly, it just has to be guaranteed to be fast enough for the respective application.

The Duden offers two descriptions for real time , on the one hand as a “given time that certain processes of an electronic computing system may consume in reality” and as “ time running simultaneously with reality ”. The Duden gives the following meaning for real-time operation in EDP: "The way an electronic computer system works, in which the program or data processing runs (almost) simultaneously with the corresponding processes in reality".


reaction time

The term real time says something about the ability of a system to react to an event within a given time frame. The term does not say anything about the speed or processing power of a system. In colloquial language, however, this is often wrongly used instead of the more appropriate terms low- delay or low-delay .

For example, in the case of near -time data from weather satellites such as EUMETSAT , measurements that are hours old are still referred to as real-time data . Real-time is also used in applications such as passenger information systems ( dynamic passenger information ) with further processing of data in the minute range.

Depending on the type of application, this response time can vary within a wide range:

Real time quality

To describe a control and regulation task, however, it is not sufficient to define a real-time via the response time. In order to define the requirements for real-time systems more clearly, the reliability of meeting this response time is often defined. For this purpose, a distinction is usually made between hard real-time and soft real-time :

  • hard real-time guarantees that the defined response time is never exceeded. You can rely on this property when using a hard real-time system , for example when recording the temporal course of the sensor data in a crash test .
  • soft real-time , here a response time is only statistically guaranteed. Such systems typically process all incoming inputs quickly enough, but this is not guaranteed. The response time reaches, for example, an acceptable mean value or another statistical criterion. Exceeding the time requirement does not lead to errors or other technical problems.
  • fixed real time is sometimes used to define a more stringent requirement than hard real time. With the fixed real time, no downward variation is allowed in the response time ( isochronous ). A practical example would be an ADC module, which ideally should work with a fixed clock rate (in reality limited by jitter of the clock).


Applications in real time are for example:

If the recording is done in real time with sensors and high-speed cameras, the recorded data can later be played back more slowly (in slow motion ). On the other hand, some physical models can be calculated much faster than in real time, such as star formation in a gas and dust cloud. Here the playback in fast motion is appropriate for the (scientific) interpretation.

See also


Kaul, Susanne (ed.); Brössel, Stephan (ed.): Realtime in the film. Concepts - Effects - Contexts , Fink 2020, ISBN 978-3-8467-6251-6 .

Web links

Wiktionary: Real-time  - meaning explanations, word origins, synonyms, translations

Individual evidence

  1. Software development of embedded systems: basics, modeling .
  2. Real time in, accessed on June 13, 2013.
  3. Real Time Images (satellite data processed to "real-time images" in the weather observation at EUMETSAT ), accessed on July 29, 2013.
  4. Boris Burger, Ondrej Paulovic, Milos Hasan: Realtime Visualization Methods in the Demoscene ( en ) In: CESCG-2002 . Technical University of Vienna . March 21, 2002. Retrieved March 21, 2011.
  5. Heinz Wörn, Uwe Brinkschulte: Real-time systems. Basics, functions, applications . Springer, Berlin et al. 2005, ISBN 3-540-20588-8 , pp. 321 , doi : 10.1007 / b139050 .