Understanding CPU Scheduling Algorithms

CPU scheduling is a process where the operating system decides which process gets to use the CPU next and for how long. The goal is to improve system performance by utilizing the CPU efficiently and providing good response times for users. There are many different CPU scheduling algorithms, each with its own advantages and disadvantages.

Let's look at the options provided and determine which one is not a CPU scheduling algorithm.

Analyzing the Given Options

• C-SCAN: This stands for Circular SCAN. C-SCAN is a disk scheduling algorithm, not a CPU scheduling algorithm. Disk scheduling algorithms determine the order in which disk I/O requests are serviced to minimize the seek time and improve overall disk access performance. C-SCAN moves the disk head in one direction, servicing requests until it reaches the end of the disk or the last request in that direction, then it jumps back to the beginning of the disk without servicing any requests on the return trip and starts moving again in the same direction.
• FCFS: This stands for First-Come, First-Served. FCFS is a CPU scheduling algorithm. It is the simplest scheduling algorithm, where processes are executed in the order they arrive in the ready queue.
• SJF: This stands for Shortest Job First. SJF is a CPU scheduling algorithm. It schedules processes based on the length of their next CPU burst. The process with the smallest next CPU burst is executed first.
• SJN: This stands for Shortest Job Next. SJN is another name for the Shortest Job First (SJF) CPU scheduling algorithm. It operates on the same principle as SJF.

Distinguishing CPU Scheduling vs. Disk Scheduling

It's important to differentiate between CPU scheduling and disk scheduling, as they address different resources and goals:

Based on the analysis, FCFS, SJF, and SJN (which is SJF) are all well-known CPU scheduling algorithms. C-SCAN, however, belongs to the category of disk scheduling algorithms.

Conclusion

Therefore, C-SCAN is the option that is not a CPU scheduling algorithm.

Revision Table: Scheduling Algorithms

Additional Information: Types of CPU Scheduling

CPU scheduling can be broadly categorized into two types:

• Preemptive Scheduling: In this type, a running process can be interrupted and moved back to the ready queue if a higher priority process arrives or if its time slice expires. Examples include Round Robin, Priority Scheduling (preemptive), SJF (preemptive).
• Non-Preemptive Scheduling: In this type, once a process starts executing, it continues until it completes its CPU burst or blocks for I/O. It cannot be interrupted by other processes. Examples include FCFS, SJF (non-preemptive), Priority Scheduling (non-preemptive).

Disk scheduling algorithms like C-SCAN are designed specifically for managing the movement of the disk head to access data blocks, minimizing the time spent seeking different tracks on the disk platter.