This document discusses CPU non-preemptive scheduling algorithms including first come first serve (FCFS), shortest job first (SJF), and priority scheduling. FCFS schedules processes in the order that they arrive without preemption. SJF selects the process with the shortest CPU burst time from the ready queue without preemption. Priority scheduling executes the highest priority process first among processes with equal priority being served in order of arrival. Examples are provided to calculate waiting times and turnaround times for each algorithm.

1. CPU Non-Preemptive
Scheduling

2. Member
 Mahmudullah 151-15-5073
 M. Munem Mostaqem 151-15-4873
 Md. Fardin Hassan 152-15-5532
 Mehedi Hasan Ratul 152-15-5711
 Md Jahid Hasan 152-15-5787
 Mohammad Shakhawat Hossain 151-15-4727

3. Definition
• Preemptive Scheduling.
- SRTF, Priority, Round Robin, etc.
 Non-preemptive Scheduling.
-FCFS, SJF, Priority, etc.

4. FCFS
Process:
 Non-preemptive scheduling algorithm.
 Follow first in first out (FIFO) method.

5. FCFS
Example 1: (Without Arrival time)

6. FCFS
TotalWaitTime=
AverageWaitingTime =
TotalTurn AroundTime=
AverageTurn Around time =

7. FCFS
Example 2: ( with ArrivalTime)

8. FCFS
TotalWaitTime=
AverageWaitingTime =
TotalTurn AroundTime=
AverageTurn Around time =

9. SJF
Process:
 once CPU given to the process it cannot be preempted until
completes its CPU burst
 Ready queue is treated as a priority queue based on smallest CPU
time requirement.

10. SJF
Example 1: (Without arrival time)

11. SJF
TotalWaitTime
6 + 0 + 3 = 9 ms
AverageWaitingTime = (TotalWaitTime) / (Total number of
processes)
9/3 = 3 ms
TotalTurn AroundTime
30 + 3 + 6 = 39 ms
AverageTurn Around time = (TotalTurn AroundTime) / (Total
number of processes)
39 / 3 = 13 ms

12. SJF
Example 2: (With ArrivalTime)

13. SJF
TotalWaitTime= 0 + 7 + 15 + 9 = 31 ms
AverageWaitingTime = 31/4 = 7.75 ms
TotalTurn AroundTime = 8+11+ 14+24= 57
AverageTurn Around time = 57/4 = 14.25 ms

14. Priority
Process:
 Each process is assigned a priority. Process with highest priority is
to be executed first and so on.
 Processes with same priority are executed on first come first
served basis.

15. Priority
Example: (With Arrival time)
Gantt chart

16. Priority
Average Wait Time : (9+5+12+0) / 4 = 6.5

17. Priority
Gantt chart:
Example 2: (without Arrival time)

18. Priority

19. Question?

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