These days the term Real-Time Operating System (RTOS) is used when referring to an operating system designed for use in embedded microprocessors or controllers. The “Real Time” part refers to the ability to implement applications that can rapidly responding to external events in a deterministic and predictable manner. RTOS-based applications have to meet strict deadline constraints while meeting the requirements of the application. One way of ensuring that urgent operations are handled reliably is to set task priorities on each task and to assign higher priorities to those tasks that need to respond in a more timely manner.