# Realtime Operating System - Task - Arrival time, deadline, computation time - Periodic vs aperiodic - Types - Hard - missing deadline is catastrophic - Soft - Zero value after deadline - Decreasing value after deadline ## Scheduling - RMS - Rate Monotonic Scheduling - Shorter period = higher priority - Tasks that are not done in time can be preempted. - Easy to implement, fixed priority, not always full utilization - EDF - Earliest Deadline First - Earliest deadline = higher priority - Fairly simple, full utilization - LLF - Least Laxity First - Don't start if there is not enough time! - Shorter period = higher priority