1. Interruption steps: ① Identify the interrupt source ② Save the scene ③ Lead to the interrupt handler
2. Processor scheduling algorithm:
①First come first served algorithm (FCFS)
Turnaround time = Completion time – Arrival time
Turnaround time with rights = turnaround time/service time
| process |
Time of arrival |
service hours |
Starting time |
Complete time |
Turnaround time |
Rights turnaround time |
| A |
0 |
4 |
0 |
4 |
4 |
1 |
| B |
1 |
5 |
4 |
9 |
8 |
1.6 |
| C |
2 |
2 |
9 |
11 |
9 |
4.5 |
| D |
3 |
4 |
11 |
15 |
12 |
3 |
Average turnaround time = 8.25
Average weighted turnaround time = 2.525
Draw the processing timeline as follows:
② Shortest job first algorithm (SJF)
| process |
Time of arrival |
service hours |
| A |
0 |
3 |
| B |
0 |
5 |
| C |
0 |
3 |
| D |
0 |
4 |
| E |
8 |
3 |
Ⅰ. Non-preemptive (jobs with short service time first)
Ⅱ. Preemptive type
a.Based on the shortest service time
b.Based on the shortest remaining service time
③Highest response ratio priority algorithm (HRN)
Priority=1+waiting time/service time
| process |
Time of arrival |
service hours |
9:40 priority during scheduling |
Priority during scheduling at 10:40 |
| J1 |
8：00 |
2h |
1+ |
1+ |
| J2 |
8：30 |
1h |
1+ |
|
| J3 |
9：30 |
0.25h |
1+ |
1+ |
Processing starts at 9:40, and the scheduling order of the three processes is J2, J3, and J1.
④Highest priority number first algorithm
| process |
Time of arrival |
service hours |
priority |
| A |
0 |
2 |
4 |
| B |
0 |
4 |
2 |
| C |
0 |
7 |
1 |
| D |
0 |
2 |
3 |
⑤Cycle rotation algorithm (time slice rotation)
Waiting queue: original existing process + newly added process + previous unfinished process
| process |
Time of arrival |
operation hours |
| P1 |
0 |
12 |
| P2 |
0 |
4 |
| P3 |
0 |
7 |
| P4 |
0 |
3 |
Assuming that the time slice length is q=2, the scheduling sequence is as follows:
