{"id":3238,"date":"2025-06-07T14:19:07","date_gmt":"2025-06-07T14:19:07","guid":{"rendered":"https:\/\/diznr.com\/?p=3238"},"modified":"2025-06-07T14:19:07","modified_gmt":"2025-06-07T14:19:07","slug":"day-02part-04-operating-system-for-gate-computer-first-come-first-serve-basic-fcfs-algorithms","status":"publish","type":"post","link":"https:\/\/www.reilsolar.com\/pdf\/day-02part-04-operating-system-for-gate-computer-first-come-first-serve-basic-fcfs-algorithms\/","title":{"rendered":"Day 02Part 04 – Operating system for gate computer – First come first serve basic algorithms (FCFS)"},"content":{"rendered":"

Day 02Part 04 – Operating system for gate computer – First come first serve basic algorithms (FCFS)<\/p>\n

[fvplayer id=”317″]<\/p>\n

First Come First Serve (FCFS) Scheduling Algorithm<\/strong><\/h3>\n

Introduction<\/strong><\/h4>\n

First Come First Serve (FCFS)<\/strong> is the simplest<\/strong> CPU scheduling algorithm, where the process that arrives first<\/strong> in the ready queue gets executed first<\/strong>. It follows the FIFO (First In, First Out)<\/strong> principle.<\/p>\n

Characteristics of FCFS:<\/strong><\/h4>\n

Non-Preemptive:<\/strong> Once a process starts execution, it cannot be stopped until it completes.
Simple and Easy:<\/strong> The implementation is straightforward using a queue.
Fairness:<\/strong> Every process gets CPU time based on arrival order.
Not Optimal:<\/strong> High waiting time due to the Convoy Effect<\/strong> (slower processes delay faster ones).<\/p>\n

Example of FCFS Scheduling:<\/strong><\/h4>\n

Let’s consider 3 processes<\/strong> with the following arrival and burst times:<\/p>\n

\n\n\n\n\n\n\n\n
Process<\/th>\nArrival Time<\/th>\nBurst Time<\/th>\n<\/tr>\n<\/thead>\n
P1<\/td>\n0 ms<\/td>\n5 ms<\/td>\n<\/tr>\n
P2<\/td>\n1 ms<\/td>\n3 ms<\/td>\n<\/tr>\n
P3<\/td>\n2 ms<\/td>\n8 ms<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

Step-by-Step Execution Order (Gantt Chart):<\/strong><\/p>\n

\n
| P1 | P2 | P3 |
\n0 5 8 16
\n<\/code><\/div>\n<\/div>\n

Calculations in FCFS:<\/strong><\/h4>\n

1. Completion Time (CT):<\/strong><\/p>\n