August
1997 QUESTION 2 Total Marks: 20 Marks |
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questions
SUGGESTED SOLUTIONS |
| 2. | (a) Describe the technique of spooling output to a printer. | [4] | |
| Four marks are available for a good description. One mark should be awarded for using the term 'spooling directory;; a further mark should be awarded for an acceptable elaboration. One mark should also be awarded for mentioning the term 'daemon service'; again, a further mark should be awarded for an acceptable elaboration. | |||
| (b) Discuss two benefits of spooling in a multiprogramming environment. | [4] | ||
| One mark should be awarded for each correct benefit named and a further mark should be awarded for an acceptable elaboration (up to a maximum of four marks). Examples of benefits include the following: | |||
| better CPU utilization | |||
| better system performance. | |||
| the printer is made sharable. | |||
| (c) With the aid of an example, show how deadlock can occur when two processes are competing for resources. | [4] | ||
| Two marks should be awarded for an example which illustrates deadlock; if the example does not include a deadlock, then no marks should be awarded. If no example is given, then no marks should be awarded for this part of the answer. | |||
| Two marks should be awarded for an explanation of how deadlock occurs only a further mark should be awarded if a definition of deadlock is given, instead of an explanation of how it occurs. A diagram would be acceptable here (or a graph). | |||
| (d) Using your example from Part (c), name and describe a suitable method for | [8] | ||
| (i) deadlock avoidance | |||
| Banker's algorithm. One mark should be awarded for using the term; one mark should be awarded for demonstrating understanding of the technique; two marks should be awarded for successfully applying the technique to the example. If no example has been presented, then only two marks can be awarded here. | |||
| (ii) deadlock detection and recovery | |||
| Recovery through pre-emption / recovery through rollback / recovery through killing processes. One mark should be awarded for using any of these terms; one mark should be awarded for demonstrating understanding of the named technique; two marks should be awarded for successfully applying the technique to the example. If no example has been presented, then only two marks can be awarded here. | |||
| In each case, show how the method could be applied to your example. | |||