ucos-ii periodic sporadic
I think uCos-ii not really a rtos. Just a multitasking system.
A rtos is a round-robin/ preemptive task scheduler. Tasks has higher priority is scheduled to round-robin switching and next round-robin circle for lower priority tasks.
A simple rtos is a round-robin scheduler.
There are two type of tasks in rtos: periodic and sporadic. Periodic is switched every real-time clock, and sporadic is switched when a event (interrupt) occured.
In a rtos, there is a single-list called run queue, that is a single-list sorted follow task's priority. When a task come to suspend, it's drop from runqueue to wait queue....
In a true rtos, time-tisk controlled from a realtime clock (Freq=32,768KHz) for task.