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Process scheduling algorithms are methods used by operating systems to manage the execution of multiple tasks. They determine which process runs at any given time, aiming to optimize performance and resource utilization. Using real-world examples can help clarify how these algorithms function in practical scenarios.
First-Come, First-Served (FCFS)
This algorithm schedules processes in the order they arrive. It is simple and easy to implement but can lead to long wait times for shorter tasks if longer tasks arrive first.
For example, in a grocery store checkout line, customers are served in the order they arrive, regardless of the number of items they have. This can cause delays for customers with fewer items if someone with many items joins the line first.
Round Robin (RR)
This algorithm assigns each process a fixed time slice or quantum. Processes are cycled through in a queue, ensuring fair CPU time distribution.
Imagine a group of people sharing a single computer, each taking turns for a set period. If a person doesn’t finish within their time, they go to the back of the line for another turn. This approach prevents any process from monopolizing the CPU.
Shortest Job Next (SJN)
This algorithm selects the process with the shortest expected execution time. It minimizes average waiting time but requires prior knowledge of process durations.
Consider a customer service center where quick questions are prioritized over lengthy issues. This ensures faster resolution for simple tasks but can cause longer wait times for complex cases.
Priority Scheduling
Processes are assigned priorities, and the scheduler selects the highest-priority process to run. This can be preemptive or non-preemptive.
In a hospital, emergency cases are treated before routine check-ups. High-priority tasks are addressed promptly, but lower-priority tasks may experience delays.
- Fairness
- Efficiency
- Responsiveness
- Complexity