Last Come First Served

What is LCFS?

Last-Come,First-Served (LCFS) scheduling means that the last (latest) process data to be added to the ready queue will be the first process to be served when the CPU is free.

One example of it is a crowded elevator, when the elevator reaches its destination, the last people to get on are typically the first to get off.

What is the difference between LCFS with Arrival Time to LCFS without Arrival Time ?

In LCFS with Arrival Time, the waiting time of it needs the value of how long does process wait before it was executed while the LCFS without AT doesn't need it.

Terms Used:

Arrival Time (AT) -

Burst Time (BT)- time taken to complete one operation or task

Waiting Time (WT)- time for which the process remains in the ready queue.

Turnaround Time (TaT)- amount of time from submission to completion of a task.

Process Arrival Time Burst Time

P1 1 2

P2 5 1

P3 3 3

P4 7 4

Process Waiting Time Turnaround Time

P1 8 10

P2 4 5

P3 5 8

P4 0 4

WT/ # of Process

4.25

Average TaT

6.75