Explain multilevel queue and multilevel feedback queue scheduling.

Multilevel Queue: separate queues for different process types (foreground/background), each with own algorithm. Fixed priority between queues or time slicing. Processes stay in assigned queue. Multilevel Feedback Queue (MLFQ): processes can move between queues based on behavior. CPU-bound processes drop to lower priority; I/O-bound stay high. New processes start high. Addresses issue of unknown burst times. Used in most modern OS schedulers.