First Come First Serve is the full form of FCFS. It is the easiest and most simple CPU scheduling algorithm. In this type of algorithm, the process which requests the CPU gets the CPU allocation first.The process which arrives first in the ready queue is firstly assigned the CPU. In case of a tie, process with smaller process id is executed first. This scheduling method can be managed with a FIFO queue.
As the process enters the ready queue, its PCB (Process Control Block) is linked with the tail of the queue. So, when CPU becomes free, it should be assigned to the process at the beginning of the queue. It is always non-preemptive in nature.