Final answer:
The traditional UNIX scheduler used in SVR3 and 4.3 BSD systems divides processes into fixed queues of priority levels, using a preemptive, priority-based scheduling algorithm.
Step-by-step explanation:
The traditional UNIX scheduler, such as those used in SVR3 (System V Release 3) and 4.3 BSD (Berkeley Software Distribution) UNIX systems, divides processes into fixed queues of priority levels. These systems implement a preemptive, priority-based scheduling algorithm where each process is assigned a priority. Processes with higher priority are scheduled to run before those with lower priority. When a process uses up its time slice as determined by the scheduler, it is placed at the end of the queue for its priority level. If there are no processes of higher priority ready to run, the scheduler runs the process at the front of the highest-priority non-empty queue.
In this scheduling pattern, the ready processes are organized into multiple queues, each representing a different priority level. Processes in higher priority queues run for shorter time slices, allowing for quick response time, but potentially leading to starvation of lower-priority processes if not managed carefully. Correction mechanisms such as priority aging can be used to gradually increase the priority of waiting processes to ensure that they eventually receive CPU time.