First Come First Served (FCFS)

FCFS stands for First Come First Serve. In the FCFS arrangement procedure, the job that arrived first in the ready queue is assigned to the CPU and then the job that came second and so on.

First Come First Serve

We can say that the ready queue acts as a FIFO (First in First Out) queue thus the arriving jobs/processes are placed at the end of the queue.

What Does First Come, First Served (FCFS) Mean?

First come First Serve (FCFS) is a functioning system process setting up a set of rules and a network directing management apparatus that automatically performs lined up requests and processes by the order of their arrival.

FCFS

With first come, first served, what comes first is handled first; the next request in line will be executed once the one before it is complete.

Characteristics

  • It follows the non-preemptive method that is once a process has control over the CPU it will not anticipate until it terminates.
  • The criteria for collection of processes are arrival time. The sender selects the first job in the ready queue and this job runs to achievement of its CPU burst.
  • The regular waiting time is very high so not ideal and thus gives poor performance.

Advantages

  • FCFS algorithm is simple, easy to implement and understand.
  • Better for processes with large burst time as there is no context switch involved between processes.
  • It is a fair algorithm as priority is not involved, processes that arrive first get served first.

Disadvantages

  • Convoy effect occurs that is all small processes have to wait for one large process to get off the CPU.
  • It is non-preemptive; the process will not release the CPU until it finishes its finishes its task and terminates.
  • It is non appropriate for interactive systems as it cannot guarantee short response time.
  • Average waiting time is high and the turnaround time is unpredictable which leads to poor performance.

That’s it.

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