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CORK INSTITUTE OF TECHNOLOGY INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Semester 2 Examinations 2009/10
Module Title: Operating Systems Fundamentals
Module Code: SOFT 6003 School: Science Programme Title: B.Sc. (Honours) in Software Development and Computer Networking
Higher Certificate in Science in Information Technology Support Programme Code: KITMN_8_Y1 KITSU_7_Y1 KDNET_8_Y1 KITSM_6_Y1
External Examiner(s): Mr. Ken Carroll Internal Examiner(s): Mr Ger MacSweeney Ms Helen Fagan
Instructions: Answer four questions. Show all work. Duration: 2 hours Sitting: Summer 2010 Requirements for this examination: Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination paper. If in doubt please contact an Invigilator.
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Q1 i) What are the main goals of a modern Operating System? List four of the main modules found
in an Operating System. [5 marks]
ii) What is an interrupt and why is this mechanism used by the CPU? [5 marks]
iii) With the aid of a diagram, describe the ‘fetch-execute’ cycle indicating when interrupts are handled.
[3 marks] iv) Explain in detail the steps that are followed when an interrupt occurs.
i) Draw a 5 state Process Transition Diagram naming all states and illustrating the transitions between these states.
ii) Apart from normal completion, suggest three reasons why a process might terminate.
iii) Consider the following set of processes with arrival times and service times given in milliseconds.
Process Name Arrival
Time Service Time
A 0 2 B 2 6 C 4 3 D 5 1
Draw a timeline to show the execution of each of these processes for the following scheduling algorithms:
• Round Robin - time slice (quantum) = 1. OR • Shortest Remaining Time Calculate the turnaround and the normalised turnaround time for each process. [12 Marks]
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Q3 i) Describe how Fixed Partitioning and Dynamic Partitioning may be used to manage
memory. Explain when or if internal and external fragmentation occur in each case. [10 Marks]
ii) Explain how a program is loaded into memory when a paging scheme is used for memory management. Why is paging a better memory management solution than Dynamic Partitioning?
iii) Convert the following 16-bit logical address into the 16-bit physical given the 6-bit page number and 10-but offset and using the supplied process page table
0001010111000101 Process Page Table Page Frame
Q4 i) With the aid of a diagram, briefly describe the structure of a hard disk and explain the terms
seek time, latency, and transfer time. [6 marks]
ii) What are the main differences between the C-Scan and SSTF algorithms used in Disk Scheduling?
[6 marks] iii) For the following track request queue, calculate the head movement for the SSTF and the C-Scan algorithm.
Assume that the head starts at track 152 and is moving toward track 199. Also assume that the drive has 200 tracks numbered 0-199. Request queue: 86, 147, 91, 177, 94, 150, 102, 175, 130 [6 marks]
iv) Explain what is meant by I/O Buffering . What is the advantage of Double Buffering over Single Buffering.
0 000101 1 000110 2 011001 3 010101 4 001100 5 010001
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Q5 i) Name three ways a disk management system might keep track of free space.
ii) With the aid of a diagram, describe the UNIX block addressing scheme. In your answer, explain what is meant by:
• An i-node • Single indirect addressing • Double indirect addressing • Triple indirect addressing
iii) Why is the scheme suitable for both large and small file?
[2 marks] iv) If the length of a block is 1Kbyte and each block that acts as an index block can hold 256
block addresses calculate the maximum size of a file. Show how you derived your answer.