The Real-Time Operating System (RTOS) support applications that meet deadlines, in addition to provide logically correct its outcome. In multi-tasking operating system for the applications request to meeting of time deadlines and functioning in proper real time constraints, to meet the real-time constraints; in real-time system for scheduling the task, different scheduling algorithms used. Most of the real-time systems are designed using priority based pre-emptive scheduling algorithm, worst case execution time estimates to guarantee the execution of high priority tasks.