Difference between First Come First Served (FCFS) and Round Robin (RR) Scheduling Algorithm

First Come First Served Scheduling Algorithm: 
First Come First Served (FCFS) is the simplest and non-preemptive scheduling algorithm. In First Come First Served (FCFS), the process is allocated to the CPU in the order of their arrival. A queue data structure is used to implement the FCFS scheduling algorithm. The process which is at the head of the ready queue is allocated to the CPU, when CPU is free. Then the process which is running is removed from the queue. When a new process enters into the ready queue, it is placed onto the tail of the ready queue. 

Round Robin Scheduling Algorithm: 
Round Robin (RR) Scheduling Algorithm is design for the time sharing system. This algorithm is the preemptive scheduling algorithm. In Round Robin Scheduling Algorithm a small unit of time called as time quantum or time slice for which the CPU is provided to each job. CPU is allocated to the each job for the duration equal to the time quantum in cyclic order. This time quantum, time slice or time interval is generally of the order of 10 to 100 milliseconds. Ready queue in the Round Robin Scheduling Algorithm is treated as the circular queue. 

The difference between First Come First Served (FCFS) and Round Robin(RR) scheduling algorithm are as follows: 

 

S.No. First Come First Served (FCFS) Round Robin(RR)
1. First Come First Served (FCFS) is the non-preemptive scheduling algorithm. Round Robin(RR) is the non-preemptive scheduling algorithm.
2. FCFS has the minimal overhead. While RR has small overhead as it is necessary to record the time elapsed and then switch the process which causes an overhead.
3. First Come First Served Scheduling Algorithm provides high response time for the processes. In Round Robin Scheduling Algorithm, for the short processes there is very low response time.
3. FCFS is inconvenient to use in the time sharing system. It is mainly designed for the time sharing system and hence convenient to use.
5. Average waiting time is generally not minimal in First Come First Served Scheduling Algorithm.  In Round Robin Scheduling Algorithm average waiting time is minimal. 
6. The process is simply processed in the order of their arrival in FCFS. It is similar like FCFS in processing but uses time quantum.

 

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