CS 111.002: CONCEPTS OF COMPUTER SCIENCE
SPRING 2008
HOMEWORK #5: CPU SCHEDULING
DUE DATE: WEDNESDAY, MARCH 26, 2008 AT 2:00 PM
NAME: ______________________________________
A CPU finishes processing a job, only to find that six new jobs have arrived, ready to be
processed:
Job:
Order of Arrival:
1
2
3
4
5
6
Time to Process
(in microseconds):
750
2000
500
4500
250
1000
Priority:
High
Medium
Low
High
Medium
Low
If the operating system utilizes a first-come-first-served CPU scheduling strategy, then the
jobs will each finish according to the following timetable:
Job:
Total Time to Finish
(in microseconds):
750
2750
3250
7750
8000
9000
This yields an average completion time of (750 + 2750 + 3250 + 7750 + 8000 + 9000)/6 =
5250 microseconds. Since these jobs have an average processing time of 1500 microse-
conds, there is a 250% average delay factor (i.e., (5250-1500)/1500).
1. (2 points) Fill in the individual completion times, the average completion time, and the
average delay factor for these jobs if the operating system utilizes a shortest-job-first
CPU scheduling strategy.
Job:
Total Time to Finish
(in microseconds):
Average Completion Time: __________ microseconds
Average Delay Factor: __________ %
