COMP25111
Two hours
Question A1 and Question B1 are COMPULSORY
UNIVERSITY OF MANCHESTER
SCHOOL OF COMPUTER SCIENCE
Operating Systems
Date: Monday 18th January 2016
Time: 14:00 - 16:00
Please answer Questions A1 and B1
and
TWO other Questions from A2, B2 or B3
Use a SEPARATE answerbook for each SECTION
This is a CLOSED book examination
The use of electronic calculators is NOT permitted
[PTO]
, COMP25111
Section A
Please note that Question A1 is
worth half the marks of the other question in this Section
A1. Compulsory
a) A web browser in the UK accesses a database in New Zealand. How long does
it take for the data to arrive back in the UK after the user presses the ‘access’
key on the web page? For simplicity, assume that: (1) the times to process the
browser key, to retrieve the data from the database, and to send and receive
messages are all negligible; and (2) the round trip data transfer takes the same
time as light to travel round the circumference of the Earth (a distance of
40,000 kilometres at a speed of metres/second). Assume the computer
running the browser has a clock rate of 3GHz and can execute one instruction
per clock cycle. How many instructions could that computer execute while
waiting for the response from the database? (2 marks)
b) Explain briefly the actions that must occur when a context switch happens in
an operating system. (2 marks)
c) What does the term deadlock mean? How may deadlock occur? (2 marks)
d) What is the key difference between a system call and a call to a library
routine? Briefly explain why this is important. (2 marks)
e) In Linux, how does a shell implement a pipe between commands? (2 marks)
Page 2 of 7
Two hours
Question A1 and Question B1 are COMPULSORY
UNIVERSITY OF MANCHESTER
SCHOOL OF COMPUTER SCIENCE
Operating Systems
Date: Monday 18th January 2016
Time: 14:00 - 16:00
Please answer Questions A1 and B1
and
TWO other Questions from A2, B2 or B3
Use a SEPARATE answerbook for each SECTION
This is a CLOSED book examination
The use of electronic calculators is NOT permitted
[PTO]
, COMP25111
Section A
Please note that Question A1 is
worth half the marks of the other question in this Section
A1. Compulsory
a) A web browser in the UK accesses a database in New Zealand. How long does
it take for the data to arrive back in the UK after the user presses the ‘access’
key on the web page? For simplicity, assume that: (1) the times to process the
browser key, to retrieve the data from the database, and to send and receive
messages are all negligible; and (2) the round trip data transfer takes the same
time as light to travel round the circumference of the Earth (a distance of
40,000 kilometres at a speed of metres/second). Assume the computer
running the browser has a clock rate of 3GHz and can execute one instruction
per clock cycle. How many instructions could that computer execute while
waiting for the response from the database? (2 marks)
b) Explain briefly the actions that must occur when a context switch happens in
an operating system. (2 marks)
c) What does the term deadlock mean? How may deadlock occur? (2 marks)
d) What is the key difference between a system call and a call to a library
routine? Briefly explain why this is important. (2 marks)
e) In Linux, how does a shell implement a pipe between commands? (2 marks)
Page 2 of 7
