In Operating Systems, which of the following is/are CPU scheduling algorithms?

1. First-Come, First-Served (FCFS): This is the simplest CPU scheduling algorithm. In this type, the process that arrives first, gets executed first. If two processes have the same arrival time, then the sequence is decided by their process ID.

2. Shortest-Job-Next (SJN) or Shortest Job First (SJF): This is a non-preemptive scheduling algorithm. The CPU is allocated to the process having the smallest CPU burst time. If two processes have the same CPU burst time, then FCFS is used to break the tie.

3. Priority Scheduling: In this type of scheduling, each process is assigned a priority. The CPU is allocated to the process with the highest priority. Equal-Priority processes are scheduled in FCFS order.

4. Round Robin (RR): This is a preemptive scheduling algorithm. Each process is provided a fix time to execute, it is called a quantum. Once a process is executed for a given time period, it is preempted and other process executes for a given time period.

5. Multilevel Queue Scheduling: This algorithm partitions the ready queue into several separate queues. Each queue has its own scheduling algorithm. For example, system processes can have highest priority.

6. Multilevel Feedback Queue Scheduling: It allows a process to move between queues. The idea is to separate processes according to the characteristics of their CPU bursts. If a process uses too much CPU time, it will be moved to a lower-priority queue.

These are some of the CPU scheduling algorithms used in operating systems.