Sp04 midterm 1-solutions - Page 1/13 University of...

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Unformatted text preview: Page 1/13 University of California, Berkeley College of Engineering Computer Science Division EECS Spring 2004 Anthony D. Joseph Midterm Exam Solutions March 18, 2004 CS162 Operating Systems Your Name: SID AND 162 Login: TA: Discussion Section: General Information: This is a closed book and notes examination. You have 120 minutes to answer as many questions as possible. The number in parentheses at the beginning of each question indicates the number of points given to the question; there are 100 points in all. You should read all of the questions before starting the exam, as some of the questions are substantially more time consuming. Write all of your answers directly on this paper. Make your answers as concise as possible. If there is something in a question that you believe is open to interpretation, then please ask us about it! Good Luck!! Problem Possible Score 1 17 2 16 3 27 4 22 5 18 Total 100 CS 162 Spring 2004 Midterm Exam March 18, 2004 Solutions Page 2/13 1. (17 points total) Short answer questions: a. (12 points) True/False and Why? i) (4 points) Because of the overhead of context switching, programs that use threads will always take longer to execute than programs that do not use threads. TRUE FALSE Why? FALSE . Threading allows I/O to be overlapped with computation which can provide substantial performance improvements. 4 points for each. 2 points for partial answers. ii) (4 points) Protection and isolation between applications and between applications and the operating system can be provided without hardware support. TRUE FALSE Why? TRUE . Using strong typing or software fault isolation can provide the same protection and isolation capabilities as hardware. iii) (4 points) After a UNIX fork operation, the parent and new child process are identical in all respects. TRUE FALSE Why? FALSE . One register is different between the parent and child, and is used to determine which process is the parent and which is the child.. b. (5 points) Consider a system with a mixture of I/O bound processes and CPU bound processes i) (3 points) Explain how this mixture of processes maximizes system utilization: We want to keep all parts of the system busy by overlapping I/O operations with CPU operations. Overall, if we have some processes using the CPU while others are waiting on I/O, then the system will be more utilized. CS 162 Spring 2004 Midterm Exam March 18, 2004 Solutions Page 3/13 ii) (2 points) Explain why this combination is more important in batch systems than it is on most computers sitting around in our department: In general, our systems are underutilized (there are a lot of wasted cycles both on I/O devices as well as CPU), and user interaction is more important. Batch systems were expensive systems that were busy all the time....
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Sp04 midterm 1-solutions - Page 1/13 University of...

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