First‐Come‐First‐Served - TarisMajor/5143-OpSystems GitHub Wiki

program-for-first-come-first-serve-scheduling

First-Come, First-Served (FCFS) is one of the simplest disk scheduling algorithms. In FCFS scheduling, requests are processed in the order they arrive, without consideration for their specific requirements or characteristics. This approach is straightforward but may not always be the most efficient, especially in terms of reducing seek time and improving overall system performance.

Key Characteristics of FCFS Scheduling

  1. Order of Arrival: Requests are attended to in the exact sequence they arrive. This means the first request in the queue is the first to be serviced, followed by the next, and so on.
  2. Non-Preemptive: Once a request is started, it runs to completion before the next request is serviced. There is no interruption or preemption.

Advantages of FCFS Scheduling

  1. Simplicity: FCFS is simple to implement and understand. It requires minimal overhead in terms of bookkeeping and scheduling logic.
  2. Fairness: Every request gets a chance to be serviced in the order it arrives, ensuring that no request is starved for service.

Disadvantages of FCFS Scheduling

  1. Long Wait Times: Requests may experience long wait times, especially if a large request is processed first, causing subsequent requests to be delayed.
  2. Inefficiency: FCFS does not consider the physical location of data on the disk, leading to inefficient use of the disk's seek capability. This can result in higher overall seek times and reduced throughput.
  3. Convoy Effect: Smaller or quick requests can be delayed by larger, time-consuming requests, creating a bottleneck effect.

Use Cases for FCFS Scheduling

  1. Simple Systems: Suitable for simple, single-user systems or environments where fairness is more important than performance.
  2. Batch Processing: Effective in batch processing systems where the order of job completion is less critical.
  3. Non-Critical Applications: Suitable for non-critical applications where processing order and efficiency are not paramount.

Sources for Further Reading