FCFS

FCFS stands for First-Come, First-Served. It is a fundamental scheduling algorithm used in operating systems, logistics, and various service-oriented industries.

Core Concept

The principle of FCFS is straightforward: the first entity (process, person, or vehicle) to arrive or request service is the first one to be served.

• In Operating Systems: FCFS is a CPU scheduling algorithm where the process that arrives in the "ready queue" first is allocated the CPU first. It is typically managed using a FIFO (First-In, First-Out) queue. It is almost always non-preemptive, meaning that once a process begins execution, it continues until it completes its task or voluntarily yields the CPU.
• In Logistics and Services: It is a common queuing method (e.g., at a supermarket checkout or a loading dock) where no specific appointment system is used; service is provided strictly in the order of arrival.

Key Characteristics

• Simplicity: It is easy to understand and implement because it requires no complex calculations or priority tracking.
• Fairness: It is considered "fair" in the sense that every task gets a turn in the exact order it arrived.
• Performance Drawbacks:

* High Wait Time: If a process with a very long burst time arrives first, all subsequent, potentially shorter processes must wait, leading to a phenomenon where small tasks suffer behind larger ones.

* Starvation: While not "starvation" in the technical sense of priority-based systems, the extended wait times can make the system feel unresponsive for shorter tasks.

Summary Comparison