Explain First-Come-First-Serve (FCFS) scheduling.

FCFS is the simplest CPU scheduling algorithm where processes are executed in arrival order using a FIFO queue. It's non-preemptive - once a process starts, it runs to completion. Advantages: simple, fair. Disadvantages: convoy effect (short processes stuck behind long ones), poor average waiting time, not suitable for interactive systems. Example: if P1(24ms), P2(3ms), P3(3ms) arrive together, average waiting = (0+24+27)/3 = 17ms vs optimal 3ms.