1.最短作业优先(SJF)：
最短作业优先 (SJF) 调度算法基于进程的突发时间。这些进程根据它们的突发时间被放入就绪队列。在该算法中，最先处理突发时间最少的进程。仅比较在该时间之前存在或已经到达的那些进程的突发时间。它本质上也是非抢占式的。它的抢占式版本称为最短剩余时间优先 (SRTF) 算法。
该算法的主要优点是它为给定的一组进程提供了最短的等待时间，从而减少了平均等待时间。该算法的缺点是系统可能永远不会处理长进程，并且可能会在队列中停留很长时间，导致进程饥饿。
笔记 –
如果两个进程具有相同的突发时间，则使用 FCFS 打破平局，即首先处理最先到达的进程。
2.循环(RR)：
循环 (RR) 调度算法是专门为分时系统设计的。进程被放入就绪队列中，在这种情况下它是一个循环队列。在这种情况下，定义了一个称为时间量的小时间单位。该算法从队列中选择第一个进程并在时间片定义的时间内执行它。如果进程的突发时间小于时间片，则 CPU 执行下一个进程，但如果它的突发时间大于时间片，则该过程被中断，并在相同的时间片内执行下一个进程。如果进程被中断，则会发生上下文切换，并将进程放回队列的尾部。它本质上是先发制人的。
该算法主要依赖于时间量程。非常大的时间量使 RR 与 FCFS 相同，而非常小的时间量会导致开销，因为上下文切换将在非常小的间隔后一次又一次地发生。
该算法的主要优点是所有进程都一个接一个执行，这不会导致进程饥饿或进程等待很长时间才能执行。 Shortest Job First(SJF)和Round-Robin(RR)调度算法的区别如下：
| Shortest Job First (SJF) | Round-Robin (RR) |
|---|---|
| Shortest Job First (SJF) executes the processes based upon their burst time i.e. in ascending order of their burst times. | Round-Robin (RR) executes the processes based upon the time quantum defined i.e. each process is executed for a fixed amount of time. |
| SJF is also non-preemptive but its preemptive version is also there called Shortest Remaining Time First (SRTF) algorithm. | Round-Robin (RR) is preemptive in nature. |
| The average waiting time for given set of processes is minimum. | The average waiting time for given set of processes is quite small and depends on the time quantum. |
| The real difficulty with SJF is knowing the length of the next CPU request or burst. | It is quite easy to implement RR. |
| A long process may never get executed and the system may keep executing the short processes. | Each process is executed and every user feels that his work is being done as the CPU gives equal amount of time to each process. |
| In case of SJF, elapsed time should be recorded, results in more overhead on the processor. | In case of RR, if the time quantum is very small then context switch takes place again and again after very short intervals of time which leads to overhead. |