csc2404 Assignment 3
Instructions
Clear Layout
Semester 2, 2019
Due Date: 11:59pm 16 October 2019, AEST
This assignment consists of 4 questions, each of equal value. Please answer the questions in your own words. At most, you should only require about a page to answer each question.
It is vitally important that your assignment is clearly laid out with questions and parts of questions clearly defined. It must be a straight forward matter for the examiner to determine that you have completed each exercise satisfactorily. We want quality not quantity. Poorly organised submissions will be rejected or receive a poor mark.
A PDFA document typeset using vanilla LATEX is preferred over a document produced by a wordprocessor. If you must use Microsoft Word or LibreOffice please export your document as PDFA1 not PDF.
Late Submission of Assignments2
Students can apply for an extension of time to submit an assign ment at any time up to the deadline. Students are advised to make a request for an extension as soon as their need becomes apparent. Delay in making a request involves the risk of losing marks if the request is refused.
The Examiner may grant a short extension of the deadline for submission of an assignment. Extensions are usually granted only in cases of Compassionate and Compelling Circumstances in ac cordance with the assessment of Compassionate and Compelling
1 PDFA is an archival format of PDF that embeds all fonts used in the doc ument within the PDF file. To ensure PDFA format in Word checkISO 19005compliant PDFAunderOptionswhen saving a file as PDF.
2 The full assessment rules and regulations can be found at http:policy. usq.edu.audocuments.php?id14749PL
Circumstances Procedure. Generally, extensions will be limited to a maximum of five University Business Days. A Student requiring an extension for a period of time in excess of this should consider applying for a Deferred Assessment as per Section 4.4 of the as sessment procedure.
Applications for extensions must be made via email or USQAs sist to the Examiner together with accompanying documentation as specified in the Assessment of Compassionate and Compelling Circumstances Procedure.
An Assignment submitted after the deadline without an approved extension of time will be penalised. The penalty for late submis sion without a preapproved extension is a reduction by 5 of the maximum mark applicable for the assignment, for each University business day or part business day that the assignment is late. An assignment submitted more than ten University business days after the deadline will have a mark of zero recorded for that assignment.
The Examiner may refuse to accept assignments for assessment purposes after marked assignments andor feedback have been re leased.
Nonsubmission of Assignments and Passing Grades3
Student Responsibilities
To be assured of receiving a passing grade a student must obtain at least 50 of the total weighted marks available for the course i.e. the Primary Hurdle, and have satisfied the Secondary Hurdle Supervised, i.e. the end of semester examination by achieving at least 40 of the marks available for that assessment item.
Supplementary assessment may be offered where a student has undertaken all of the required summative assessment items and has passed the Primary Hurdle but failed to satisfy the Secondary Hurdle Supervised, or has satisfied the Secondary Hurdle Super vised but failed to achieve a passing Final Grade by 5 or less of the total weighted Marks.
To be awarded a passing grade for a supplementary assessment item if applicable, a student must achieve at least 50 of the available marks for the supplementary assessment item as per the Assessment Procedure point 4.4.2.
The offer of Supplementary Assessment normally will only be made if the Student has undertaken all possible Summative Assessment Items for the Course i.e. the assignments.
The Assessment Procedure Section 4.2.2, also outlines the following student responsibilities:
3 See the University Assessment Procedure policy document
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Academic Misconduct
If requested, Students must be capable of providing a copy of Assignments submitted. Copies should be dispatched to the University within 24 hours of receipt of a request being made.
Students are responsible for submitting the correct Assign ment.
Assignment submissions must contain evidence of student ef fort to address the requirements of the Assignment. In the absence of evidence of Student effort to address the require ments of the assignment, no Mark will be recorded for that Assessment Item.
A Student may resubmit an Assignment at any time up to the deadline. A request to resubmit after the deadline is dealt with in accordance with section 4.4Deferred, Supple mentary and Varied Assessment and Special Considerationof these procedures.
Academic misconduct is unacceptable and includes plagiarism, col lusion and cheating:
plagiarism : cheating :
collusion :
involves the use of another person s work without full and clear referencing and acknowledgement;
involves presenting another student s work as your own;
is a specific type of cheating, that occurs when two or more students fail to abide by directions from the examiner regard ing the permitted level of collaboration on an assessment.
All are seen by the University as acts of misconduct for which you can be penalised. For further details go to the Library s site on Plagiarism.
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Question 1 marks 20 10 marks
Answer the following questions:
a. Consider the following page reference string:
3, 1, 4, 1, 2, 3, 5, 3, 2, 1, 2, 5, 4, 3, 5, 2, 4, 2, 5, 3
Using the above page reference string display the contents of the frames after each page reference, marking when a page fault occurs cf. Figures 9.12, 9.14, or 9.15 of the text book, either edition.
Assume 3 frames and use the following algorithms LRU replacement
FIFO replacement
Optimal replacement
Repeat using 4 frames.
Remember that all frames are initially empty, so the first unique pages will cost one fault each.
b. The VAXVMS system used a FIFO replacement algorithm for resident pages and a freeframe pool of recently used pages. Assume that the freeframe pool is managed using the least recently used LRU replacement policy. Answer the following questions:
i If a page fault occurs and if the page does not exist in the freeframe pool, how is free space generated for the newly requested page?
ii If a page fault occurs and if the page exists in the free frame pool, how is the resident page set and the free frame pool managed to make space for the requested page?
iii What does the system s paging algorithm reduce to if the number of resident pages is set to one?
iv What does the system s paging algorithm reduce to if the number of pages in the freeframe pool is zero?
10 marks
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Question 2 marks 25 10 marks
8 marks
7 marks
Question 3 marks 30
Question 4 marks 25 13 marks
12 marks
Answer the following questions:
a. Unix has the concept of ahard linkand asoft link . Ex plain how a Unix filesystem implements each type of link.
b. Based on the filesystem implementation discussed above ex plain why Unix does not allow ahard linkto a directory but will allow asoft linkto a directory.
c. When copying a file to a USB flash drive on a Unix system it is extremely important to unmount the flash drive before removing the device. Explain why.
If the USB flash drive is removed before unmounting then the copied file will normally appear on the flash drive s file system have a directory entry and an inode but will be empty. Explain why the file meta data is copied synchronously but the file data is copied asynchronously.
What are the steps required to be performed by the Ext2 file system subsystem to delete a file of size 72KiB? Assume you know and have in memory a copy of the inode of the directory the file is in and the inode of the file to be deleted. Also assume the block size is 1024 bytes. Either list the steps required or use a flowchart. See the week11 practical for information on the Ext2 file system and examples of listing the required steps or writing a flowchart
Answer the following questions:
a. In most multiprogramming systems, user programs access memory through virtual addresses, while the operating sys tem and DMA controllers use raw physical addresses to ac cess memory. What are the implications of this design on the initiation of IO operations by the user program and their ex ecution by the operating system?
b. An openfile table is used to maintain information about files that are currently being accessed by a process. Should the operating system maintain a separate table for each process or just maintain one table that contains references to files that are being accessed by all processes at the current time, or use both types of tables? Justify your answer.
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