What is FCFS Scheduling Full Form? - Characteristics, Limitations and Benefits of FCFS

By Anjnee Bhatnagar|Updated : May 26th, 2022

FCFS Scheduling Full Form: The full form of FCFS is First Come First Serve. It is one of the CPU scheduling algorithms used by the mid-term scheduler. FCFS scheduling full form is the simplest and one of the easiest scheduling algorithms. It uses a FIFO queue (FIFO Full Form: First In First Out) to execute processes.

In this article, we will learn about the various scheduling algorithms available along with the full form, the characteristics of FCFS scheduling full form, and the benefits and the limitations of FCFS in comparison to other available algorithms.

Table of Content

Characteristics of FCFS Scheduling Full Form

The very first scheduling algorithm that one learns in the operating system is FCFS Scheduling. Among the different scheduling algorithms, FCFC scheduling full form is the simplest and easiest to implement. Let us see the characteristics of FCFS scheduling:

  • It executes all the processes on a first-come, first-serve basis.
  • Not complicated to implement.
  • It takes arrival time as the criteria to select processes.
  • It follows a non-preemptive approach.
  • Feasible to use.

CPU Scheduling Algorithm

It is defined as a process of selecting and assigning processes to the CPU for execution. Whenever the CPU is idle, the scheduler selects a process from the ready queue and assigns it to the CPU for execution. Scheduling of the process is done by a mid-term scheduler.

A mid-term scheduler selects one of the processes from the ready queue and assigns it to the CPU. It uses various scheduling algorithms to select processes. These scheduling algorithms are further divided into two categories:

  • Preemptive: Preemptive algorithms are one in which the execution can be preempted forcefully or due to the lack of resources. There are various preemptive scheduling algorithms, such as preemptive priority scheduling, SRTF, LRTF, etc.
  • Non-preemptive: In non-preemptive algorithms, the process terminates only after the complete execution. It will not be interrupted or preempted for any reason. Non-preemptive algorithms are FCFC, HRRN, SJF, and LJF.

Benefits of FCFS Scheduling 

Having discussed the implementation process and the characteristics of FCFS, we will now learn about the benefits attached to this particular scheduling algorithm. The benefits are as follows:

  • There is no starvation in the case of FCFS.
  • It is a fair algorithm as no priority of the processes is involved.
  • Easy and simple implementation.
  • It follows the FIFO queue to assign processes.

Limitations of FCFS Scheduling 

The FCFS scheduling full form is simple and easy to implement, which makes it hassle-free for the scheduler to select any process from the ready queue. However, there are some the setbacks to using the FCFS scheduling algorithm, which are as follows:

  • It leads to a convoy effect, which is undesirable.
  • It does not lead to increased throughput.
  • It is not compatible with the time-sharing systems.

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FAQs on FCFS Scheduling Full Form

  • The FCFS scheduling full form is First Come, First Serve. The operating systems and networks use the FCFS scheduling method to efficiently and automatically execute queued tasks, processes, and requests in the order of their arrival.

  • The condition of the convoy effect is observed in the FCFS algorithm. It is defined as the condition in which the longer jobs arrive first and start their execution, then the waiting time of the shorter jobs increases drastically, thus leading to the increased waiting time and decreased throughput of the system.

  • A mid-term scheduler is responsible for scheduling processes to the CPU for execution. Whenever the CPU is idle, a process from the ready queue is selected by the mid-term scheduler and assigned to the CPU for its execution.

  • Scheduling algorithms are of two types: Preemptive and Non-preemptive. A non-preemptive algorithm is one in which the process terminates after executing all its tasks; that is, it executes in one go. There are various non-preemptive algorithms available such as FCFS Scheduling Full Form, HRRN, SJF, etc.

  • There are advantages as well as disadvantages of using FCFS Scheduling Full Form. The advantage is that it is simple to implement and easy to understand, while the disadvantages are that it leads to convoy effect, low CPU utilization, and increased average waiting time.

  • The FCFS scheduling full form uses arrival time as its criterion to pick a process from the ready queue for execution in the CPU. FCFS serves the processes on a first-come, first-serve basis. It is a non-preemptive scheduling algorithm that is the simplest to implement.

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