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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 31 (Page No. 335)
Consider Fig. $4-27.$ Is it possible that for some particular block number the counters in both lists have the value $2?$ How should this problem be corrected?
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 30 (Page No. 335)
It has been suggested that the first part of each UNIX file be kept in the same disk block as its i-node. What good would this do?
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 29 (Page No. 335)
Suppose that file $21$ in Fig. $4-25$ was not modified since the last dump. In what way would the four bitmaps of Fig. $4-26$ be different?
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 28 (Page No. 335)
We discussed making incremental dumps in some detail in the text. In Windows it is easy to tell when to dump a file because every file has an archive bit. This ... missing in $UNIX.$ How do $UNIX$ backup programs know which files to dump?
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 27 (Page No. 335)
Oliver Owl's night job at the university computing center is to change the tapes used for overnight data backups. While waiting for each tape to complete, he ... that is the only one they have. Is there a problem with this arrangement?
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 26 (Page No. 334)
What would happen if the bitmap or free list containing the information about free disk blocks was completely lost due to a crash? Is there any way to recover ... Discuss your answers for $UNIX$ and the $FAT -16$ file system separately.
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 25 (Page No. 334)
The beginning of a free-space bitmap looks like this after the disk partition is first formatted$:\: 1000\: 0000\: 0000\: 0000$ (the first block is used by the ... $C$ is written, using eight blocks.File $B$ is deleted.
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 24 (Page No. 334)
Free disk space can be kept track of using a free list or a bitmap. Disk addresses require $D$ bits. For a disk with $B$ blocks, $F$ of which are free, ... $16$ bits, express your answer as a percentage of the disk space that must be free.
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 23 (Page No. 334)
Consider a $4-TB$ disk that uses $4-KB$ blocks and the free-list method. How many block addresses can be stored in one block?
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 22 (Page No. 334)
Explain how hard links and soft links differ with respective to i-node allocations.
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 21 (Page No. 334)
Name one advantage of hard links over symbolic links and one advantage of symbolic links over hard links.
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 20 (Page No. 334)
Two computer science students, Carolyn and Elinor, are having a discussion about i-nodes. Carolyn maintains that memories have gotten so large and so cheap that when ... table to see if it is already there. Elinor disagrees. Who is right?
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 19 (Page No. 334)
It has been suggested that efficiency could be improved and disk space saved by storing the data of a short file within the i-node. For the i-node of Fig. $4-13,$ how many bytes of data could be stored inside the i-node?
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 18 (Page No. 334)
Consider a file whose size varies between $4\: KB$ and $4\: MB$ during its lifetime. Which of the three allocation schemes (contiguous, linked and table/indexed) will be most appropriate?
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 17 (Page No. 334)
For a given class, the student records are stored in a file. The records are randomly accessed and updated. Assume that each student's record is ... three allocation schemes (contiguous, linked and table/indexed) will be most appropriate?
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 16 (Page No. 334)
Consider the $i\text{-node}$ shown in Fig. $4-13.$ If it contains $10$ direct addresses and these were $8$ bytes each and all disk blocks were $1024\: KB,$ what would the largest possible file be?
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 15 (Page No. 333)
Some digital consumer devices need to store data, for example as files. Name a modern device that requires file storage and for which contiguous allocation would be a fine idea.
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 14 (Page No. 333)
In light of the answer to the previous question, does compacting the disk ever make any sense?
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 13 (Page No. 333)
One way to use contiguous allocation of the disk and not suffer from holes is to compact the disk every time a file is removed. Since all files are contiguous, copying ... numbers, how long would it take to compact half of a $16-GB$ disk?
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 12 (Page No. 333)
Describe the effects of a corrupted data block for a given file for:contiguous,linked, andindexed (or table based).
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 11 (Page No. 333)
Contiguous allocation of files leads to disk fragmentation, as mentioned in the text, because some space in the last disk block will be wasted in ... external fragmentation? Make an analogy with something discussed in the previous chapter.
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 10 (Page No. 333)
Consider the directory tree of Fig. $4-8.$ If /usr/jim is the working directory, what is the absolute path name for the file whose relative path name is ../ast/x?
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 9 (Page No. 333)
In UNIX and Windows, random access is done by having a special system call that moves the current position'' pointer associated with a file to a ... file. Propose an alternative way to do random access without having this system call.
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 8 (Page No. 333)
A simple operating system supports only a single directory but allows it to have arbitrarily many files with arbitrarily long file names. Can something approximating a hierarchical file system be simulated? How?
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 7 (Page No. 333)
In some systems it is possible to map part of a file into memory. What restrictions must such systems impose? How is this partial mapping implemented?
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 6 (Page No. 333)
Some operating systems provide a system call rename to give a file a new name. Is there any difference at all between using this call to rename a file and just ... file to a new file with the new name, followed by deleting the old one?
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 5 (Page No. 333)
Systems that support sequential files always have an operation to rewind files. Do systems that support random-access files need this, too?
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 4 (Page No. 333)
Is the open system call in $UNIX$ absolutely essential? What would the consequences be of not having it?
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 3 (Page No. 333)
In early UNIX systems, executable files (a.out files) began with a very specific magic number, not one chosen at random. These files began with a header, ... other file types had a more-or-less random magic number as the first word?
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Andrew S. Tanenbaum (OS) Edition 4 Exercise 4 Question 2 (Page No. 332)
In Windows, when a user double clicks on a file listed by Windows Explorer, a program is run and given that file as a parameter. List two different ways the operating system could know which program to run.
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