![]() ![]() When working in pre-emptive mode, the task chosen to execute is the highest priority task that is able to execute. The faster the required response, the higher the priority level assigned. In a pre-emptive system each Task is given an individual priority value. ![]() However, to provide a responsive system most RTOS’s use a pre-emptive scheduling algorithm. There are several scheduling algorithms available, including Round Robin, Co-operative and Hybrid scheduling. When switching between Tasks the RTOS has to choose the most appropriate task to load next. The difference between the two can be highlighted through examples – compare, for example, the editing of a document on a PC to the operation of a precision motor control. ![]() An RTOS differs in that it typically provides a hard real time response, providing a fast, highly deterministic reaction to external events. ![]() OS’s typically provide a non-deterministic, soft real time response, where there are no guarantees as to when each task will complete, but they will try to stay responsive to the user. The difference between an OS (Operating System) such as Windows or Unix and an RTOS (Real Time Operating System) found in embedded systems, is the response time to external events. ![]()
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