Difference between Periodic and Aperiodic Real-time Tasks
1. Periodic Real-time Tasks :
The real-time task that is repeated after a certain time interval is known as periodic real-time task. Basically the periodic real-time tasks are controlled by the clock interrupts. Therefore, the periodic real-time tasks are also called clock-driven tasks. The time interval after which the task repeats itself is known as period of the task.
For example, when a flight is detected by the radar and until the radar exists, the radar signal zone is an example of periodic real-time task.
2. Aperiodic real-time Tasks :
The real-time task that occurs at any random time is known as aperiodic real-time task. Between two aperiodic real-time tasks the time interval may be even zero. Soft real-time tasks are generally aperiodic real-time tasks. It is also possible that these tasks may occur frequently or there might be a large time interval between two aperiodic real-time tasks.
For example, typing on the key-board is an aperiodic real-time task.
Difference between Periodic and Aperiodic Real-time Tasks:
|It repeats itself after a certain time interval.
|It can occur at random instants.
|These tasks are controlled by clock interrupts.
|These tasks are not controlled by clock interrupts.
|The time interval between occurrence of two consecutive tasks can’t be zero.
|The time interval between occurrence of two consecutive tasks can be zero.
|Periodic tasks generally include soft and hard real-time tasks both.
|Aperodic tasks generally include soft real-time tasks.
|Deadline of all instances of periodic task can be meet easily.
|To meet deadline of all instances of an aperodic task is quite difficult.
|It includes vast majority of internal tasks.
|It includes interactive task with users.
|Example: Taking information from sensor at a time interval.
|Example: Logging task in a distributed system.
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