COMP1562 2021 MAY - exam 2021 PDF

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APPROVED __________________________________________________________EXAMINATION PAPER: ACADEMIC SESSION 2020/Campus Maritime GreenwichFaculty Liberal Arts and SciencesSchool Computing and Mathematical SciencesLevel 5Exam Session May 2021MODULE TITLE Operating SystemsMODULE CODE COMPDuration 2 hoursAn...

Description

APPROVED________________________________________________________ __

EXAMINATION PAPER:

ACADEMIC SESSION 2020/2021

Campus

Maritime Greenwich

Faculty

Liberal Arts and Sciences

School

Computing and Mathematical Sciences

Level

5

Exam Session

May 2021

MODULE TITLE

Operating Systems

MODULE CODE

COMP1562

Duration

2 hours

Answer any TWO of the following THREE questions. Each question is worth 50 marks. If you answer more than two questions, marks will ONLY be awarded for your TWO best answers.

Operating Systems COMP1562

APPROVED__________________________________________________________

1. (a)

With the aid of diagrams compare and contrast the systems with and without interrupts. [10 marks]

(b)

If you were to develop a software driver to support documents printing that would prevent processes from printing at the same time, how you would do it in a systems that support / do not support synchronization mechanisms? Discuss at least TWO potential solutions (one for a system supporting synchronization mechanisms and one for a system that does not support any synchronization mechanisms) and provide a block diagram / pseudocode detailing how ANY of the TWO solutions would need to be implemented in the core part of the driver to prevent processes from printing documents at the same time would look like. [20 marks]

[Up to [10 marks] for a correct processes placement plus up to [20 marks] for correctly drafted program to a maximum of 20 marks]

(c)

You are employed as a senior Linux system administrator in an organisation, and you are going to allow two of the lesser-privileged users to perform selected administration task. Specifically, you would like them to help you with groups / users management. Describe TWO alternative ways of achieving this without revealing the users the administrator (root) password. Wherever possible provide implementation examples. [20 marks]

[Up to [15 marks] for a reasonable explanation and up to [15 marks] for appropriate examples to a maximum of [20 marks]] .

Operating Systems COMP1562

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APPROVED__________________________________________________________ 2. (a)

Compare and contrast internal and external memory partitioning. [10 marks]

(b)

Explain usage of pipelines and streams redirection in Linux operation system. Wherever possible provide implementation examples using real commands and explain in detail what is the effect of provided examples. [20 marks] [up to 15 marks for description and examples showing how to use pipelines, up to 15 marks for description and examples showing how to use stream redirection to a maximum of 20 marks]

(c)

Consider the three processes listed below with their arrival time and service time to be AT and ST respectively. P1: AT=0ms, ST=3ms P2: AT=2ms, ST=7ms P3: AT=4ms, ST=5ms Draw Gantt charts and calculate average waiting time TA and average turnaround time TT for each of the two following scheduling algorithms:

-

Preemptive version of Shortest Job Next Non-preemptive version of Shortest Job Next Based on the performance index Jx expressed as: J x = 0.3TA + 0.7TT

state which of the two scheduling algorithms is more efficient (guarantees better performance meant by lower value of the performance index [20 marks] [up 10 marks for each Gannt chart algorithm and up to 10 marks for calculations to a maximum 20 marks]

Operating Systems COMP1562

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APPROVED__________________________________________________________ 3. (a)

With the aid of diagrams explain race condition problem in the context of concurrent programs. [10 marks]

(b)

In your Linux system you have a user account jellybean. However, the account owner requested that he would like to receive e-mails sent to [email protected] since his real name is John Smith. Describe ANY TWO ways you could achieve this.

Wherever possible use appropriate system commands, configuration files, system files, etc. [20 marks] [up to 8 marks for each method and up to 8 m arks for likely to work examples to a maximum of 20 marks]

(c)

Consider a hypothetical processor with: - 16 bit accumulator AC - 16 bit instruction register IR - 12 bit program counter PC - Instruction format: - 4 bit opcode - 12 bit address The processor works in a typical Von Neumann fetch-execute mode. Draw a diagram showing execution of the following pseudo-program: 1. Loading AC register from memory location 940 (assume current AC value is 0 and 940 memory location stores value 2). 2. Adding to the AC register memory location 941 (assume its current value is 4). 3. Storing the result in the I/O device 001 (assume its current value is 0). 4. Assume program is loaded into memory, beginning from location 300. The opcodes are: 0001 = load AC 0010 = store AC in the I/O device 0100 = add to AC

[20 marks] [Up to [8 marks] marks for each correct step (4 for fetch and 4 for the execute part) to a maximum of 20 marks].

Operating Systems COMP1562

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