Real-Time Computing: Difference between revisions

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* https://en.wikipedia.org/wiki/Real-time_computing
* https://en.wikipedia.org/wiki/Real-time_computing
* Real-Time Computing: A New Discipline of Computer Science and Engineering https://kabru.eecs.umich.edu/papers/publications/1994/ramanathan-shin-ieee-proceedings.pdf


=Internal=
=Internal=
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Formally, a system is said of be real-time if the correctness of an operation depends not only upon its logical correctness, but also upon the time in which the operation is performed. Real-time systems are classified by the consequences of missing a deadline:
Formally, a system is said of be real-time if the correctness of an operation depends not only upon its logical correctness, but also upon the time in which the operation is performed. Real-time systems are classified by the consequences of missing a deadline:
* <span id='Hard'></span>'''Hard''' Real-Time System - missing a deadline is a total system failure.
* <span id='Hard'></span>'''Hard''' Real-time System - missing a [[#Deadline|deadline]] is a total system failure.
* <span id='Firm'></span>'''Firm''' Real-Time System - infrequent deadline misses are tolerable, but may degrade the system's quality of service. The usefulness of a result is zero after its deadline.
* <span id='Firm'></span>'''Firm''' Real-time System - infrequent [[#Deadline|deadline]] misses are tolerable, but may degrade the system's quality of service. The usefulness of a result is zero after its [[#Deadline|deadline]].
* <span id='Soft'></span>'''Soft''' Real-time System - the usefulness of a result degrades after its deadline, degrading the system's quality of service.


=Real-time Operating System=
=Real-time Operating System=
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An operating system intended to serve real-time applications that process data as it comes, without [[#Buffer_Delay|buffer delays]]. The system attempts to insure [[#Real-time_Constraint|the guaranteed response time]], possibly at the expense of the throughput.
An operating system intended to serve real-time applications that process data as it comes, without [[#Buffer_Delay|buffer delays]]. The system attempts to insure [[#Real-time_Constraint|the guaranteed response time]], possibly at the expense of the throughput.


=Real-time Constraint=
=<span id='Deadline'></span>Real-time Constraint=


A ''real-time constraint'' is a guaranteed response within a specified time constraint between event to system response. Real-time constraints are also referred to as "deadlines". Deadlines must always be met, regardless of system load. For [[#Hard|hard]] and [[#Firm|firm]] real-time systems, the usefulness of a result is zero after its deadline.
A ''real-time constraint'' is a guaranteed response within a specified time constraint between event to system response. Real-time constraints are also referred to as "deadlines". Deadlines must always be met, regardless of system load. For [[#Hard|hard]] and [[#Firm|firm]] real-time systems, the usefulness of a result is zero after its deadline.
=Near real-time=


=Buffer Delay=
=Buffer Delay=


=Jitter=
=Jitter=

Latest revision as of 00:52, 19 April 2018

External

Internal

Overview

A real-time system is subject to a "real-time constraint" - a guaranteed response within a specified time constraint between event to system response. Real-time systems control an environment by receiving data, processing it, and returning the results sufficiently quickly to affect the environment at that time.

Formally, a system is said of be real-time if the correctness of an operation depends not only upon its logical correctness, but also upon the time in which the operation is performed. Real-time systems are classified by the consequences of missing a deadline:

  • Hard Real-time System - missing a deadline is a total system failure.
  • Firm Real-time System - infrequent deadline misses are tolerable, but may degrade the system's quality of service. The usefulness of a result is zero after its deadline.
  • Soft Real-time System - the usefulness of a result degrades after its deadline, degrading the system's quality of service.

Real-time Operating System

https://en.wikipedia.org/wiki/Real-time_operating_system

An operating system intended to serve real-time applications that process data as it comes, without buffer delays. The system attempts to insure the guaranteed response time, possibly at the expense of the throughput.

Real-time Constraint

A real-time constraint is a guaranteed response within a specified time constraint between event to system response. Real-time constraints are also referred to as "deadlines". Deadlines must always be met, regardless of system load. For hard and firm real-time systems, the usefulness of a result is zero after its deadline.

Near real-time

Buffer Delay

Jitter