What is First Come First Served (FCFS) ? Definition, Scheduling and More

FCFS Definition or Meaning

FCFS (First Come First Served) is the modest scheduling algorithm, FIFO queues processes in the order that they reach in the ready queue. Since context switches only occur upon process termination and no reorganization of the process queue requires, scheduling overhead is minimal.

• The scheduling of FCFS is fair in the formal or human sense of fairness. But also, it is unfair in the mind that long jobs make small jobs wait, and unimportant tasks make relevant jobs remain.
• First Come First Served is more predictable than most of the other schemes since it offers time.
• The plan of FCFS is not useful in scheduling interactive users because it cannot guarantee a good response time.
• First Come First Served scheduling code is easy to write and understand.

What is FCFS Scheduling?

Here we are going to focus on FCFS scheduling. FCFS Scheduling helps in to organize the processes in an efficient way for the processor.

The planning algorithms are responsible for ensuring that a process does not monopolize the processor. A process is a program that is running. This process can be in 3 different states “Ready” “Blocked” and “Running”. The processes are stored in a list along with the information that indicates the state of the process, the time the CPU has used, etc.

How does the FCFS algorithm works?

The acronym [FCFS] means First to arrive, First to be Served, within the CPU Planning algorithms, this is the easiest.

The workload processes in order of arrival. And also by not taking into account the state of the system or the resource needs of the individual processes, First Come First Served planning can lead to poor returns.

This algorithm has a high response time of the CPU because the process does not leave the CPU until it finishes because it is an algorithm Without Eviction (Not Appropriate). First Come First Served planning eliminates the notion of process priorities.

To choose the process to which the CPU will be assigned, the one that takes the most time ready (first in the queue) is preferred.

The execution of the process only yields the CPU for two reasons:

• To be voluntarily blocked pending an event (Printer, file, etc.)
• When its execution ends.

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What are the Advantages of First Come First Served [FCFS]?

It is easy to understand and easy to program. It is also fair. Track of all ready processes keeps a single linked list. Picking a process to run requires removing one from the front of the queue. Adding a new job or unblocked process requires attaching it to the end of the line.

What are the Disadvantages of First Come First Served?

• Since long processes can hog the CPU throughput can be low.
• Waiting time, response time, and turnaround time can be short for the same reasons above.
• The processing time of each job must be known in advance. Suitable only for the batch process.
• The average time is often quite long, which is one of the significant drawbacks of this scheme.

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