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华南理工大学期末考试
《操作系统》试卷B
注意事项：1. 考前请将密封线内填写清楚； 2. 所有答案请答在答题纸上； 3．考试形式：闭卷；
4. 本试卷共 三 大题，满分100分， 考试时间120分钟。 题 号 一 得 分 评卷人 二 三 总分 一、单项选择题 (20pts total, 2pts each)
1. ( ) What is the main advantage of multiprogramming?
A. Efficient use of the CPU C. Efficient use of disk
B. Fast response
D. Short Turnaround time
2. ( ) Mutex is used for mutual exclusion problem. For 2 parallel processes, the value of mutex cannot be______. A. 1 B. 0 C. -1 D. -2 3. ( ) It is provable that _____ scheduling algorithm is optimal if all the jobs are available simultaneously.
A. First Come First Served (FCFS) C. Shortest Remaining Time Next (SRTN) B. Shortest Job First (SJF) D. Priority 4. ( ) Suppose that the operating system is running a non-preemptive scheduler and that process p is currently running. A context switch can occur . A. when p terminates or blocks B. when another process unblocks C. when another process enters D. when the time quantum is exhausted 5. ( ) Which of the following statements is true?
A. The use of a TLB for a paging memory system eliminates the need for keeping a
page table in memory.
B. External fragmentation can be prevented by frequent use of compaction, but the
cost would be too high for most systems.
C. The first fit allocation algorithm often creates small holes that can't be used. D. More page frames always have fewer page faults 6. ( ) The file-reference count is used for .
A. counting number of bytes read from the file B. counting number of open files
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_____________ ________ 姓名 学号 C. counting number of links pointing to a file D. counting number of process accessing a file
7. As for Unix system, the attributes of file are stored in .
A. file B. directory C. i-node D. directory entry 8. ( ) “Device independence” means .
A. that devices are accessed dependent of their model and types of physical device. B. systems that have one set of calls for writing on a file and the console (terminal)
exhibit device independence.
C. that files and devices are accessed the same way, independent of their physical
nature.
D. none of the above 9. ( ) How much cylinder skew is needed for a 10000-rpm disk with a
track-to-track seek time of 800us? Assuming that the disk has 300 sectors of 512 bytes each on each track. A. 24 B. 48 C. 20 D. 40 10. ( ) In a system, all resource requests must be made in numerical order. This is a method for preventing deadlock to attack the condition. A. mutual exclusion C. no preemption B. hold and wait D. circular wait
二、简答题(20pts total, 5pts each)
1. (5 pts) What is the biggest advantage of implementing threads in user space? What is
the biggest disadvantage?
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2. (5pts) In a virtual memory system, does a TLB miss imply a disk operation will
follow? Why or why not?
3. (5 pts) How does MS-DOS implement random access to files?
4. (5pts) A system has p processes each needing a maximum of m resources and a total
of r resources available. What condition must hold to make the system deadlock free?
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三、综合题(60pts total)
1. (10pts) Men and women share a bathroom. But when a women is in the bathroom,
other women may enter, but no men, and vice versa. Please use semaphores to solve this problem.
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2. (10 pts) Suppose two processes enter the ready queue with the following properties:
(1) Process 1 has a total of 8 units of work to perform, but after every 2 units of
work, it must perform 1 unit of I/O (so the minimum completion time of this process is 12 units). Assume that there is no work to be done following the last I/O operation.
(2) Process 2 has a total of 20 units of work to perform. This process arrives just
behind P1.
Show the resulting schedule for the Shortest-Job-First (preemptive) and the Round-Robin algorithms. Assume a time slice of 4 units for RR. What is the completion time of each process under each algorithm?
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