FOR FREE YEAR SOLVED

First Come First Serve (FCFS):

 

FCFS process and examples

The process that requests the CPU first is allocated the CPU first

 

Criteria: Arrival Time

Decision mode: Non-preemptive 

Data-Structure: Queue

 

 

Example:

 

 

First we design a Gantt Chart according to arrival time and burst time to follow FCFS.

 

 

Now calculate Completion Time (CT) from Gantt Chart

 

 

Now we calculate Turn Around Time (TAT) and as per the formula we know   

 

Turn Around Time (TAT)= Completion Time (CT)  – Arrival Time (AT)

We can also calculate Wait Time (WT) using the formula:

 

TAT = WT +  BT

 

WT = TAT - BT

 

 

In the case of Non-Preemptive waiting time and first Response Time (RT) is same.