FCFS CPU Scheduling Algorithm Explained

Full transcript

In any computer system, multiple processes are constantly ready and waiting to be executed. However, the CPU can only run one process at a time, so we need a way to manage them. This is where process scheduling comes in. The operating system uses scheduling algorithms to decide the exact order in which processes receive access to the CPU for execution. One of the simplest and most intuitive scheduling algorithms is called First Come First Serve, or FCFS. The rule is straightforward: whichever process arrives first simply gets the CPU first. FCFS is also a non-preemptive algorithm, which means once a process starts running on the CPU, it will continue running until it completely finishes — no interruptions allowed. Let us look at a concrete example. Process P1 arrives at time zero with a burst time of eight units. P2 arrives at time one with a burst time of two, and P3 arrives at time two needing three units. Following FCFS order, P1 executes from zero to eight, then P2 runs from eight to ten, and finally P3 runs from ten to thirteen. The execution order is simply P1, then P2, then P3.