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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Examinations 2007/
Module Title: Operating Systems
Module Code: OPSY S
School: Computing & Mathematics
Programme Title: Higher Certificate in Science in Computing (ACCS) – Year 2
Programme Code: KCOME_6_Y
External Examiner(s): Ms. Mairead Meagher Ms. Anna Brown Internal Examiner(s): Mr. Paul Rothwell
Instructions: Answer any FOUR questions. All questions carry equal marks.
Duration: 3 HOURS
Sitting: Winter 2007
Requirements for this examination: N/A
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.
- (a) The three major goals of an operating system are: convenience of use, efficiency
and fairness, and expandability. Briefly discuss, each of these goals with the help of examples drawn from any aspect of operating systems. [6 marks]
With the aid of an example, comment on (^) the significance of the logical/physical divide from the point of view of the programmer. [4 marks]
(b) Briefly outline the role of the process control block (PCB). [3 marks] Summarise (^) the typical contents of a PCB. [4 marks]
(c) List and briefly explain^ the steps involved in a process switch. [5 marks] Briefly distinuish (^) between a process switch and a context switch. [3 marks] [Total: 25 marks]
- (a) Briefly define the notion of deadlock using an everyday example. [2 mark] Distinguish between deadlock avoidance, deadlock prevention, and deadlock detection. [6 marks]
(b) Write pseudocode to fully describe^ the Banker’s algorithm (and its associated ‘safety’ algorithm) for deadlock avoidance. [7 marks] Fully explain the meaning of the following terms in this algorithm: Allocation, Max, Available, Need. [4 marks]
(c) Based on the following information, show and explain how the banker’s algorithm you described can be used to determine if the following resource request from process 2 is granted: request 2 = (0,1,0) [6 marks]
Process Allocation Max Available type => X Y Z X Y Z X Y Z 0 0 0 1 0 0 1 2 1 0 1 2 3 0 2 6 5 2 0 0 3 6 6 5 3 2 3 5 4 3 5
[Total: 25 marks]
- (a) With reference to the paging scheme of memory management, use diagrams, examples, and definitions to give full descriptions of : (i) the efficiency of use of physical memory; [3 marks] (ii) address mapping; [6 marks]
(b) Fully explain^ the following terms with respect to resident set management: (i) fixed allocation, local scope; (ii) variable allocation, global scope; (iii) variable allocation, local scope. [3 marks] Briefly explain and comment upon each of the following characteristics that may be taken into account in the choice of a victim page when replacing a page in virtual memory management: recency, age, frequency, modify/dirty bit. [8 marks]
(c) Assuming memory is managed using a paged virtual memory management scheme, outline the notion of a page fault. [2 marks] List and briefly describe the steps involved in the page fault handling routine. [3 marks] [Total: 25 marks]
- (a) Explain the following terms^ in the context of CPU scheduling: (i) Pre-emptive and non-pre-emptive scheduling algorithms; (ii) CPU-bound and I/O bound processes. [4 marks] Indicate broadly the importance of each of these notions for CPU scheduling. [4 marks] (b) Given the following set of process information, for ONE of the following scheduling algorithms briefly characterise the algorithm and complete the table below: (i) Round Robin (time slice = 4); (ii) Highest Response Ratio Next; (iii) Shortest remaining time. [5 marks] Fully explain how you got your answer with the help of a table on graph paper. [5 marks] Proc arrival time service time wait time Turnaround NTT Ratio 0 0 6 1 1 8 2 3 2 (c) Fully explain a typical Multi-level Feedback scheduling arrangement. [7 marks] [Total: 25 marks]
