周期性和非周期性实时任务的区别

1. 周期性实时任务：
在一定时间间隔后重复执行的实时任务称为周期性实时任务。基本上，周期性实时任务由时钟中断控制。因此，周期性的实时任务也称为时钟驱动任务。任务重复自身的时间间隔称为任务周期。

例如，当雷达检测到飞行时，直到雷达存在，雷达信号区就是周期性实时任务的一个例子。

2. 非周期性实时任务：
在任何随机时间发生的实时任务称为非周期性实时任务。在两个非周期性实时任务之间，时间间隔甚至可能为零。软实时任务通常是非周期性的实时任务。也有可能这些任务经常发生，或者两个非周期性的实时任务之间可能有很大的时间间隔。

例如，在键盘上打字是一项非周期性的实时任务。

周期性和非周期性实时任务的区别：

PERIODIC TASK	APERIODIC TASK
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.