Easytolearn

   Round Robin ·          Round robin Scheduling is similar to FCFS but preemption is addede to switch between processes. ·          In RR scheduling, processes are dispatched in FIFO but given a small amount of CPU time. This small amount of CPU time this small amount of time is known as time quantum or time slice. A time quantum is generally from 10 to 100 milliseconds ·          If a process does not complete before its time slice expires, the CPU is time slice and is given to the next waiting process in ready queue. ·          The preempted process in then places at the   tail of the ready queue. ·          If a process is completed before its time slice expires, the process itself release the CPU. The scheduler then proceeds to the next process in ready queue. ·          Whenever any new process arrives in the system it is added at the tail of the ready queue. ·          Round robin scheduling is effective in timesharing environment in which the system need to guaran

Priority scheduling           In priority scheduling , a priority is associated with all processes.            Process are executed in sequence according to their priority.           The CPU time is allocated to the process with highest priority.           If the priority of two or more processes are equal than the process that has been inserted first   into   the ready queue is selected for execution. In other words, FCFS scheduling is performed when wo or more processes have same priority.           The priorities are implemented as affixed range of numbers such as 0to 7 or 0 to 4,095.           In other system, a low number indicates a high priority . in that case,a process with priority 0 is executed first.           Priorities can be defined in two ways : internal or externall.           Priority scheduling can be preemptive or non preemptive.           In preemptive priority scheduling , scheduler allocates the CPU to the new process if the priority of new proce

  Shortest Job First Scheduling (SJF) ·          SJF ia also known as shortest-job-next(SJN) algorithm and is faster than FCFS. ·          In SJF, the process with the least estimated execution time is selected from the ready queue for   execution. ·          For this, SJF algorithm associates with each process, the length of its next CPU burst. When the CPU is available, it is assigned to the process that has the smallest next CPU burst. ·          If tow processes have the same length of next CPU burst ,FCFS scheduling algorithm is used to break the tie. ·          SJF algorithm can be preemptive or non-preemptive.     Non-preeptive SJF ·          In non-preemptive SJF, scheduling, CPU is always assigned to the process with least CPU burst time and the process keeps CPU with it until it terminates. ·          The main advantages of SJF scheduling is that it give minimum average waiting time for a given set of processes. By moving a short process before a long proc