Oct 22, 2017 Java Program for First Come First Serve (FCFS) Scheduling Algorithm In this article we are going to learn about first come first serve (fcfs) scheduling in Java with program example. FCFS strategy will be helpful in many situations especially in tie breaking situations. OS FCFS with overhead with Definition and functions, OS Tutorial, Types of OS, Process Management Introduction, Attributes of a Process, Process Schedulers, CPU Scheduling, SJF Scheduling, FCFS with overhead, FCFS Scheduling etc.
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Given n processes with their burst times, the task is to find average waiting time and average turn around time using FCFS scheduling algorithm.First in, first out (FIFO), also known as first come, first served (FCFS), is the simplest scheduling algorithm. FIFO simply queues processes in the order that they arrive in the ready queue.In this, the process that comes first will be executed first and next process starts only after the previous gets fully executed.Here we are considering that arrival time for all processes is 0.How to compute below times in Round Robin using a program?.
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Completion Time: Time at which process completes its execution. Turn Around Time: Time Difference between completion time and arrival time. Turn Around Time = Completion Time – Arrival Time.
Waiting Time(W.T): Time Difference between turn around time and burst time.Waiting Time = Turn Around Time – Burst TimeIn this post, we have assumed arrival times as 0, so turn around and completion times are same.Implementation: 1- Input the processes along with their burst time (bt).2- Find waiting time (wt) for all processes.3- As first process that comes need not to wait sowaiting time for process 1 will be 0 i.e. Wt0 = 0.4- Find waiting time for all other processes i.e. Forprocess i -wti = bti-1 + wti-1.5- Find turnaround time = waitingtime + bursttimefor all processes.6- Find average waiting time =totalwaitingtime / noofprocesses.7- Similarly, find average turnaround time =totalturnaroundtime / noofprocesses. # by ChitraNayalOutput:Processes Burst time Waiting time Turn around time1 10 0 102 5 10 153 8 15 23Average waiting time = 8.33333Average turn around time = 16Important Points:. Non-preemptive. Average Waiting Time is not optimal.
Cannot utilize resources in parallel: Results in Convoy effect (Consider a situation when many IO bound processes are there and one CPU bound process. The IO bound processes have to wait for CPU bound process when CPU bound process acquires CPU. The IO bound process could have better taken CPU for some time, then used IO devices).Source:In we will be discussing the processes with different arrival time.Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
First Come First Serve (FCFS) is a method of load balancing to achieve the quality of service. The thread which comes first into the Process queue is served first. You can also think of this as First in First out (FIFO). The process which comes first is served first regardless of its burst time.
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For example: If there are three processes namely p1, p2 and p3 having burst times 10, 14, 5 respectively and they arrive in the order p2, p1, p3. First p2(0) is served then p1(14) and then p3(14+10) is served i.e., p3 is served after 24 units.
FCFS Java Program
Output:
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