Difference between Periodic and Sporadic Real-time Tasks

Prerequisite – Tasks in Real Time systems

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.
For example, in a chemical plant temperatures, pressure and other attribute are measured periodically and all information is passed to controller.

2. Sporadic Real-time Tasks :
The real-time task that reoccurs at random instant is known as sporadic real-time task. Sporadic real-time task has some similarity to aperiodic real-time task but it is different from aperiodic real-time task. Basically all the high critical tasks are sporadic tasks.
For example, fire handling task in industry is sporadic task.

Difference between Periodic and Sporadic Real-time Tasks :

PERIODIC TASK	SPORADIC TASK
It reoccurs after a certain period of time.	It reoccurs at random instant.
It is controlled by clock interrupts.	It is not controlled by clock interrupts.
Time of occurrence of periodic tasks can be predicted.	Time of occurrence of sporadic tasks can’t be predicted.
It includes moderate critical or low critical tasks.	It includes highly critical tasks.
It includes normal system tasks.	It includes tasks that may lead to system failure.
It can be easily scheduled by cyclic scheduler.	It is complex to schedule sporadic tasks by cyclic scheduler.
Periodic tasks are allotted time frame in generalized task scheduler.	Sporadic tasks are allotted slack time in generalized task scheduler.
Example: Measuring of temperature and pressure at a time interval.	Example: Emergency message arrivals in the system.