Modern computers are capable of doing many tasks at the same time. You can listen to music, browse the internet, download files, and type a document simultaneously without your computer freezing. To users, this multitasking ability feels completely natural. However, behind the scenes, the operating system must constantly decide which program gets access to the processor first.

This decision-making process is known as CPU scheduling.

Today, operating systems use highly advanced scheduling systems that can intelligently manage thousands of tasks every second. However, long before modern AI-driven schedulers existed, computer scientists relied on a much simpler method called the First Come First Serve (FCFS) algorithm.

FCFS is one of the oldest and most important scheduling algorithms in computer science history. Even though modern systems rarely use it as their primary scheduler anymore, it still forms the foundation for understanding how CPU scheduling works. For students learning operating systems, FCFS is usually the very first scheduling algorithm introduced because it clearly demonstrates the core principles of process management.

What Is the First Come First Serve Algorithm?

The First Come First Serve algorithm is the simplest type of CPU scheduling technique used in operating systems.

As the name suggests, the process that arrives first gets executed first. The operating system processes tasks strictly in the order they enter the queue, without considering how large, important, or complex the tasks are.

A simple real-world example is standing in a supermarket checkout line. The customer who arrives first is served first, regardless of how many items they are buying. Someone with only one item still has to wait behind a customer with a full shopping cart.

FCFS applies the exact same idea to computer processes.

When a process requests CPU access:

• it joins the ready queue
• the process at the front gets CPU access first
• all other processes must wait for their turn

This straightforward behavior makes FCFS incredibly easy to understand and implement.

The Historical Background of FCFS

To understand why FCFS became important, we need to look back at the early days of computing during the 1960s. At that time, personal computers did not exist. Instead, organizations used massive mainframe computers that filled entire rooms. These systems were extremely expensive and mainly used by universities, research centers, and governments.

One famous example was the IBM 7094 mainframe system introduced in 1962.

Users did not interact directly with these computers through keyboards and

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