1.2 Processor Scheduling

Question 1

What are interrupts?

Answer 1

A signal to the CPU to change the process it is completing.

Question 2

Explain the steps of interrupt process.
(4 points)

Answer 2

• Interrupt signal of higher priority received.
• Stores values of registers for current task.
• Completes interrupt service routine.
• Restores previous task.

Question 3

What are some examples of why interrupts happen?

Answer 3

• Power failure
• Clock (scheduled) interrupt
• Input / Output requests

Question 4

What is Processor Scheduling ?

Answer 4

Assigning different tasks to a CPU at different
times to give the appearance of multi-tasking.

Question 5

How should Hardware be kept ?

Answer 5

As busy as possible

Question 6

What are the 5 types of Processor Scheduling methods ?

Answer 6

• First come First Served,
• Shortest Remaining Time
• Shortest Job First
• Round robin,
• Multi-level feedback queues,

Question 7

How does first come first served work?

Answer 7

do the task that started first first.

Question 8

How does Shortest remaining time/job first work? (2 points)

Answer 8

Do the task with the Shortest remaining time/job first.
An issue with this is that longer tasks may never be completed.
Another issue is that processing power is used to work out which task has the shortest remaining time/ job first.

Question 9

How does Round robin work?

Answer 9

Cycle through all processes using a consistent time slice.

Question 10

How do Multi-level feedback queues work?

Answer 10

Manage multiple priority queues of jobs based on resources they use