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Quiz 3
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Questions in this quiz (162)
1Some systems used multiple queues of jobs waiting to be executed, one for each memory partition. In this scheme, how are incoming (new) jobs assigned to queues?
- AA new job was placed in the first queue after the one into which the previous job was placed, cycling back to the first queue after a job was placed in the last queue.
- BA new job was placed in a queue associated with a partition that was large enough to satisfy the job's memory requirements
2In a system that uses a single queue of jobs waiting to be executed, it is common for the job at the head of the queue to be placed in the first partition to become unused (because of the completion of the job that was running there). What other condition is necessary for the job at the head of the queue to be assigned to the first available memory partition?
- AThe job had to have a priority greater than the job that had just been using the memory partition
- BThe job's memory requirements had to be no larger than the size of the memory partition
3Another problem with running jobs in different memory partitions is that the job must be prepared to execute in the range of addresses associated with the partition. Which of the following techniques cannot be used to accomplish this?
- AAllowing the program to dynamically modify itself at execution time to execute in the memory partition where it was loaded.
- BShifting each of the addresses generated by the program during its execution left by the number of bits corresponding to its partition number (1, 2, ...)
4The term used for modifying the addresses used with a program depending on where in physical memory it will execute is called
- Arelocation
- Bmagic
5In the IBM System/360, a base register is
- Aa special-purpose register that can be controlled by the process.
- Bone of the general-purpose registers explicitly used by a program
6When a system includes a special-purpose register to solve the relocation problem, it is common for that register
- Ato contain the address of the lowest, or first location used by a user program
- Bto be set by the user program at the beginning of its execution
7When the CPU is switched from executing one user program to another in a system with multiple programs resident, and a system using a single relocation register
- Athe operating system must modify the contents of the relocation register as part of each context switch operation.
- Bthe contents of the relocation register need not be altered
8The term memory protection is used to describe the techniques used to
- Aprevent an executing user program from modifying and/or accessing regions of memory not assigned to that program.
- Bprevent an executing program from modifying values in the stack associated with the program
9A common approach to memory protection uses a register that is frequently called
- Athe authority register
- Bthe limits register
10Suppose a system uses a limits register as part of its memory protection scheme. When an address generated by the program exceeds the value in the limits register,
- Athe address is left-shifted by the number of bits sufficient to ensure the resulting address is less than or equal to the value in the limits register.
- Ba memory protection fault is generated
11The term swapping is used to describe
- Athe process of copying all of the memory contents associated with a program to a reserved region on disk, and then copying all of the information on disk for another program into the primary memory just vacated
- Bexchanging the contents of a region of memory with the contents of a different region of memory belong to a different process.
12The IBM operating system called OS/MVT differs from OS/MFT in what major way?
- AThe size of the memory partitions in OS/MVT was variable, while they were fixed in OS/MFT
- Bit could only run on later models of the System/360 processor.
13After a system using variable partition sizes has been in operating for some time, the available free memory
- Atends to be grouped together into two regions, one at the bottom of the physical memory and one at the top of the physical memory.
- Bbecomes fragmented into small regions between the allocations made for running programs
14Suppose there are numerous small regions of unused memory in a system, each of which is too small to load a program for execution. The process of moving programs in memory so these small fragments are grouped together in a larger region is generally termed
- Acompacting the memory
- Breducing the memory.
15What is the CPU doing while the small unused regions of memory resulting from variable-size partitions are being moved so they form a larger region?
- Anothing; it is running the idle process
- Bmoving the contents of partitions to new locations, and possibly relocating programs
16Which of the following schemes will probably waste the least amount of memory, given a sufficient collection of work to be processed?
- AOS/MVT
- Bswapping
17What program/process property must be accurately specified if partitioned memory management is to be used effectively?
- Aindication of whether the process will request additional memory during execution
- Bthe size of the memory region required for the program's execution
18What is the heap?
- Aa region of memory used to satisfy dynamic memory allocation requests
- Ba region of memory used during sorting
19Suppose the memory available for execution of a process in a partitioned memory organization is sufficient to begin execution, but insufficient to complete execution because of increases in the size of the stack and/or the heap. Which of the following events is used to identify this condition?
- AThe memory allocated to the stack and the memory allocated to the text (code) region collide
- BThe memory allocated to the heap and the memory allocated to the stack collide
20There are several major techniques used to keep track of the status (allocated or free) and size of each block of contiguous physical memory in a system. What are two of these?
- Abits maps and linked lists
- Bbit maps and red-black trees
21Suppose a bit map is used to record the status of memory blocks. Which of the following tasks is relatively difficult to perform using the bit map approach? That is, which task is likely to require the most execution time to complete?
- Aallocating a memory region with N contiguous blocks
- Bfreeing (deallocating) a memory region with N contiguous blocks
22Suppose a linked list is used to record the location and size of each unused block of memory in a system. Further assume the list is ordered by the size of each free region, from the smallest region (at the front of the list) to the largest region (at the end of the list). Which of the following requests is most difficult to perform, in general, with this scheme?
- Aallocating a block of memory with an arbitrary specified size
- Bcoalescing all regions of memory that are physically adjacent
23Suppose a linked list is used to record the location and size of each unused block of memory in a system. Further assume the list is ordered by the location of each free region, from the region with the smallest address (at the front of the list) to the region with the largest address
(at the end of the list). Which of the following requests is easiest to perform, in general, with this scheme?- Aidentifying the largest unused block of physical memory in the system
- Bcoalescing all regions of memory that are physically adjacent
24When the first fit algorithm finds an unused region of memory that is sufficient to satisfy a memory allocation request, what happens if the region is larger than the requested size?
- AThe region's node on the list is saved and the search continues. If no other unused memory region fits the request better, then the region identified by the save node is used
- BThe region is split, and the region containing the excess memory is placed back on the list of free/unused regions.
25How does the next fit algorithm differ from the first fit algorithm?
- AFirst fit always finds the first unused memory region that satisfies an allocation request. Next fit always finds the second unused memory region that satisfies the same request
- BFirst fit always starts with the first node in the linked list of nodes identifying free memory regions. The next fit algorithm begins where the search for the last request ended.
26Suppose the address of a block of memory being managed by the buddy system is 01101111000 (binary). What is the binary address of its buddy if the block is of size 4, and if the block is of size 16?
- A01101101000, 01110001000
- B01101101000, 01101101000
27Suppose the buddy system is used to manage the available regions of unallocated memory. What is unique about the size of unused memory regions in this algorithm?
- AEach unused region has a size equal to a power of 2.
- BEach unused region must be paired with another unused region (itsbuddy) to satisfy anymemory allocation request
28Which of the following pairs of schemes for managing memory provide reasonably efficient techniques for deallocation?
- Athe buddy system and unordered linked lists
- Bthe buddy system and bit maps
29To what does the term fragmentation refer when applied to memory allocation in a computer system?
- Athe creation of areas in memory that are not used, or are not usable, by programs
- Bthe need to use two memory regions that are not physically contiguous because no single contiguous region with a sufficient size can be found
30External fragmentation results in small regions of unallocated memory located
- Ain the memory allocated to the stack of a program
- Boutside the allocations belonging to any program
31Internal fragmentation results in small regions of unused memory located
- Abetween a region of read-only memory and the top (upper limit) of the physical address space.
- Bin regions that have been allocated to programs.
32Knuth's fifty percent rule says that, averaged over time,
- Athere will be fifty percent as many holes in memory as there are processes
- Bthe size of holes will be fifty percent as large as the average size of a process
33The unused memory rule for partitioned memory is a rather astounding result. If the average size of a hole (i.e. a small unused memory region) is k times the average amount of memory associated with a process, then the fractional part of memory occupied by holes is given by
- Ak / (k + 2)
- B(k + 1) / (k + 2)
34Suppose the buddy system is used to manage memory allocation and deallocation of a system that does not divide memory into blocks smaller than 1K. When a process requests a 40K block, how large a block will it receive if the allocation request is successful?
- A52K
- B64K
35Suppose a system has the following unused blocks of memory: 10K at location 15K, 15K atlocation 35K, and 10K at location 55K. A process relinquishes 5K of memory at location 30K. What unused blocks of memory will exist after the deallocation is performed?
- A10K at location 15K, 20K at location 30K, and 10K at location 55K
- B10K at location 15K, 15K at location 35K, 10K at location 55K, and 5K at location 30K
36A worst fit memory allocation technique might make sense because
- Ait would justify the purchase of additional memory.
- Bit would leave the largest unused region of memory available to satisfy future allocations.
37The memory technique called overlays is possible because of what property of some functions and procedures in a program?
- AThey have variable sizes. That is, the amount of memory they require varies based on which program or process is using them
- BThey are used independently of other functions and procedures with the same property. As a result, two such functions need not be in physical memory at the same time
38If the overlay memory technique can be successfully used for a program, what is the most likely positive effect?
- AThe program will be able to execute faster than if overlaying was not used.
- BThe program will be able to execute using a smaller amount of memory than if overlaying was not used.
39When using overlays, the overlay structure -- that is, the information describing whichregions of a program will occupy the same memory locations -- is determined by
- Athe virtual memory system.
- Bthe user.
40In paged memory systems, the memory required by a program is broken into several pieces. The size of each piece is
- Athe same as every other piece.
- Bbased on the size of the logical components of the program (e.g. functions, subroutines,arrays).
41In segmented memory systems, the memory required by a program is broken into several pieces. The size of each piece is
- Aequal to the size of the largest logical component of the program
- Bbased on the size of the logical components of the program (e.g. functions, subroutines,arrays).
42Suppose we wish to use paging with a program that requires 22,000 bytes. Suppose the sizeof a page is 5,000 bytes. How many bytes will be unused in this case?
- A1,000 bytes
- B3,000 bytes
43Suppose we wish to use paging with a program that requires 22,000 bytes. Suppose the size of a page is 5,000 bytes. Some storage will be unused in this case. This is an example of
- Apoor planning.
- Binternal fragmentation
44Which of the following is a major task of the memory management unit (MMU) in modern processors?
- Aread as much as possible from physical memory into a processor cache each time an access is made
- Btranslate virtual addresses to the corresponding physical addresses
45Which hardware component of a modern computer system generates virtual addresses?
- Athe CPU
- Bthe MMU
46The size of an address space on a system is determined by
- Athe width of the system bus, in bits
- Bthe number of bits in an address
47What is the relation between the size of the virtual address space on a computer and the size of the physical address space?
- AThe physical address space is always at least as large as the virtual address space.
- BThere is not necessarily any relation between the sizes of these address spaces, other than that each is usually a power of two
48The term page frame refers to
- Aan area in the physical memory of a computer system used to store, or frame information being moved between virtual and physical memory
- Bone of the fixed-sized regions into which the physical memory of a computer system supporting paging is divided.
49The term page refers to
- Aone of the fixed-sized regions into which the physical memory of a computer system supporting paging is divided.
- Bone of the fixed-sized regions into which a program is divided so it can be used on a system supporting paging
50How much external fragmentation occurs when a system uses paged memory management?
- AThe amount of external fragmentation depends on the particular programs being executed
- BNo external fragment occurs in this case
51Suppose a system uses paged memory management, and pages of programs are not brought into memory until they are actually referenced. This technique is commonly called
- Ademand paging
- Bin-response paging.
52Suppose a system uses paged memory management, and some pages of programs are brought into memory before they are actually needed. This technique is commonly called
- Aprepaging
- Bjust-in-time paging
53A virtual address in a particular paged computer system is divided into two pieces, a page number and an offset. The system uses 4096 byte pages. How many bits are in the offset portion of a virtual address for this system?
- A8 bits
- B12 bits
54When the MMU (memory management unit) translates a virtual address to a physical address on a paged computer system, which part of the virtual address is not modified?
- Athe offset
- Bthe high-order bits
55Assume a system using paged memory management divides each virtual address into a page number and an offset. To what does the MMU translate a page number, assuming the translation is possible?
- Aa different offset
- Ba page frame number
56Translation of page numbers to page frame numbers is done by the MMU (memory management unit). What data structure does the MMU use to accomplish this translation?
- Athe page table
- Bthe segment table
57Each entry in the data structure that can be successfully used by the memory management unit (MMU) in a paged virtual memory system contains
- Aa page size.
- Ba page frame number
58The data structure used by the MMU (memory management unit) in a system using paged memory management is essentially
- Aa queue
- Ban array
59Which component of a virtual address is used by the MMU (memory management unit) to select an entry from the data structure used by the MMU?
- Athe number of bits in the virtual address
- Bthe page number
60Because of the manner in which the MMU (memory management unit) selects entries from a page table, the data structure that represents the page table
- Amust be logically contiguous
- Bcan never be modified during the lifetime of the process
61Where, on most systems, is the entire page table stored?
- Ain a special secondary storage device that has a slower access time, but larger transfer rate, than primary memory
- Bin primary memory
62Assume that page table entries are stored only in primary memory. How many references to primary memory would then be required to access an instruction or an instruction's operand?
- Atwo
- Bfour
63Suppose we do not require that each page of a program be present in primary memory at all times. In order to know which pages are present, and which ones aren't, systems use a special bit called the presence bit. This bit is located
- Ain each page of the program
- Bin each page table entry
64The presence bit was called the translation not valid bit on the VAX-11 computer system. This name was appropriate because
- Athe reference to the page by the program was not allowed
- Bthe page frame number field in the page table entry was not correct if the page was not present in primary memory
65What event occurs when a process attempts to access a page of virtual memory which has a page table entry indicating that page is not present in physical memory?
- Aan AGP fault
- Ba page fault
66When a context switch occurs (when the processor switches from executing instructions for one process to instructions for another), how is the page table used by the MMU (memory management unit) affected by a context switch?
- AA different page table, the one for the process to which the processor is being switched, must be used.
- BA different page table is used if the process to which the processor is being switched is not a child of the process that was previously being executed.
67Which of the following techniques is commonly used to eliminate the need for a region of contiguous memory larger than a page to be used for a page table?
- Aa larger physical address space
- Ba multi-level page table, like that used in the Intel x86 architecture
68Many systems include bits in addition to the page frame number field in their page table entries. Which of the following is not such a bit?
- Athe presence bit
- Bthe recursive bit
69What is the principle of locality?
- AThe set of page table entries used to map the virtual addresses used by a program changes membership slowly
- BA program that uses a small, localized region of virtual memory will execute more efficiently than a program that uses several different regions of virtual memory
70If the principle of locality holds (as it does for virtually all well-behaved programs), how is the set of actively referenced page table entries (for a single program) affected?
- AThe set of page table entries continues to grow smaller
- BThe set of page table entries changes membership slowly
71A relatively small set of the page table entries for a program that are accessed frequently are normally stored in a special type of memory. This type of memory is called
- Atranslator memory
- Bassociative memory
72Translation Lookaside Buffer (TLB) is the name often given to the memory in which frequently-used page table entries are stored. Entries in the TLB are not ordered in the same way as entries in the page table. Instead, these entries are
- Astored by increasing virtual address so a binary search can be used in mapping a virtual address
- Ball searched in parallel for the proper entry to use in mapping a virtual address.
73Since the memory used for a TLB is much more expensive than normal physical memory, TLBs are usually much smaller than physical memories. What precaution must be taken with the TLB entries when a context switch occurs?
- AThe entries that are not appropriate for the process to which the processor is being switched must be replaced, or at least invalidated.
- BThe entries must be changed all at once, since the access time to the TLB is relatively long.
74The concept of a Content Addressable Memory was invented by
- AMaurice Wilkes.
- BDonald Knuth
75The key used in a lookup in the associative memory used for a Translation Lookaside Bufferis
- Aa process identification number.
- Ba virtual page number
76One alternative to the traditional MMU organization is to use only a cache of page table entries. If the desired page table entry is not in the cache of such entries,
- Athe cache entry that was least recently access is replaced (by the hardware) with the page table entry for the needed page
- Ba page fault is generated and system software must make the page present and update the cache
77An inverted page table is indexed by page frame number, and not by virtual page number.Accessed only when the cache lookup for a virtual page number fails, it is appropriate for use
- Awhen a system has a very large virtual address space.
- Bwhen a system has very slow physical memory
78When a page fault occurs because a needed page of a program is not present in physical memory, that page must be made present, usually by copying it from secondary storage (e.g.disk) into an available empty page frame. The system obtains an empty page frame
- Aby selecting the page frame most recently accessed by a program, and preserving its contents if they were modified
- Bfrom a pool of such empty page frames, or by evicting a page from a filled page frame to make an empty page frame
79Which of the following pages is a likely candidate for removal from primary memory in order to make a page frame available for use?
- Aa page that will never be accessed again by the process that previously needed it
- Bthe page that contained the instruction that was just executed.
80The algorithm used to identify page frames that are candidates for becoming empty page frames is called
- Athe EPF identification algorithm
- Ba page replacement algorithm
81Once a page has been selected for use as an empty page frame
- Aits contents are set to random values
- Bits contents must be preserved (e.g. on disk) if it has been modified.
82The OPT, or optimal page replacement algorithm, is guaranteed to yield the best performance of any such algorithms. Why, therefore, is this algorithm not used in real operating systems?
- AIt is protected by copyrights, and the licensing fees are very large
- BIt requires knowledge of the future.
83If the OPT page replacement algorithm is not used in real operating systems, then of what value is it?
- AAlthough it is not used in its pure form, with small modifications the NOPT (nearly optimal) algorithm can be used.
- BIt indicates the best possible performance of any page replacement algorithm, and can be used as a yardstick against which the performance of other page replacement algorithms can be measured
84The modified bit in a page table entry is also frequently called
- Athe rewrite bit
- Bthe dirty bit
85The Not Recently Used page replacement algorithm classifies each present page as being in one of four categories based on the value of the expression _______, where R is the value of the referenced bit for the page and M is the value of the modified bit for the page
- AR * 2 + M
- BR * 4 + M
86The Not Used Recently page replacement algorithm classifies each present page as being in one of four numbered categories. When it selects one or more pages for replacement, they are selected from which of the numbered categories (that is not empty)?
- Athe lowest numbered category
- Bthe highest numbered category
87The FIFO page replacement algorithm attempts to replace those pages that have been in memory the longest, and are therefore the least likely to be needed in the future.Unfortunately, these pages may also have been in memory a long time because they are needed frequently. What modification of FIFO is used to adjust for this problem?
- Athe second chance algorithm
- Bthe second time around algorithm
88How is a page's referenced(R) bit used by the modification of the FIFO algorithm that attempts to allow frequently referenced pages to remain in memory longer?
- AIf the R bit is 0 when the page reaches the head of the FIFO queue it is set to 1 and thepage is moved to the end of the queue. If it was already 1, then the page is replaced
- BEach time a page reaches the head of the FIFO queue, the R bit is examined. If it is 0, the page is replaced. Otherwise, the R bit is set to 0 and the page is placed at the end of the list.
89What is the clock algorithm?
- AIt is a variant of the FIFO algorithm that uses a circular queue
- BIt is a variant of the OPT algorithm that predicts the next time a page will be referenced based on the length of time between the last two references.
90What is the name of the page replacement algorithm that selects pages that have not been used for the longest time of any pages in memory?
- Athe second life algorithm
- BNone of the other answer choices is correct
91The FIFO page replacement algorithm can exhibit an interesting behavior. We normally expect that when a program is allowed to use a larger number of page frames that the number of page faults will go down, or at least not increase. This is not always the case with the FIFO algorithm. This behavior is called _____.
- Athe Bremsstrahlung effect.
- BBelady's anomaly.
92Page replacement algorithms that can be provably shown to never generate more page faults when the number of page frames they are allowed to use increases are called ___________algorithms.
- Astack
- Bqueue
93The set of pages being actively used by a process is called its
- Arecalcified set
- Bworking set.
94Assume a program must fill each byte in a large two-dimensional array with some value.Which of the following approaches to that task will probably result in the largest working set size? Assume arrays are stored in row-major order (that is, all the elements of the first row of the array are stored together in memory just before the elements of the second row,and so forth).
- AFill each of the array elements in the first column, then the second column, and so forth
- BNone of the other answer choices is correct.
95What is the working set principle?
- AA program will run most efficiently if all of the pages in its working set are in contiguous page frames in physical memory.
- BA program must not be run unless its entire working set can be made resident in primary memory
96When a system is said to be thrashing, it is spending most of its time
- Awaiting for pages to be moved between primary and secondary memory.
- Bexecuting the page replacement algorithm
97To what do the terms global page replacement and local page replacement refer?
- Awhether all of the pages that are in a contiguous region around the last referenced page of the current process are considered as candidates for replacement, or all pages in the process.
- Bwhether pages selected for replacement are chosen from all processes, or just from the pages belonging to the process needing additional pages
98We may determine that a program is in need of additional page frames when
- Athe rate at which it generates page faults is relatively high
- Bthe rate at which it generates page faults is relatively low.
99Which of the following is an advantage of a large page size?
- APage tables will be smaller.
- BThere will be more external fragmentation.
100In a segmented virtual memory system, virtual memory addresses have two components. One of these components is _____.
- Aa unique integer assigned to the segment whose address is being specified
- Bthe address of the highest-numbered physical address in the segment
101What type of fragmentation, if any, is exhibited by pure segmented virtual memory systems?
- Arecursive fragmentation
- Bexternal fragmentation
102One task that must be performed during virtual to physical address translation in a segmented system that is not required in a paged system is
- Averifying that the offset in the segment is not larger than the segment size
- Bupdating the modified bit if the hardware uses it.
103With respect to memory in a computer system, the term persistent means
- Athe ability of a memory type to retain its contents even after its power source has been removed
- BNone of the other answer choices is correct.
104Assume a disk device can be read by a user application, and further assume that this disk contains files belonging to many users. What prevents the user application from reading files belonging to other users?
- AThe disk controller, which must be given the user ID of the owner of each block that is to be read
- BThe file system, which verifies that each disk access is to a block containing information that can be legally read by the user owning the application process
105Many storage devices used by filesystems in modern computer systems are removable, like floppy disks, CDs and DVDs, and flash RAM. Why is it usually necessary to inform the operating system before physically removing one of these devices from the system?
- AThe operating system usually buffers data (in RAM) that is to be written to removable devices, so the writing is not necessarily complete as soon as a write or close system call is completed. Telling the system you want to remove the device tells it to write all modified data in buffers to the device before indicating it is safe to remove the device.
- BNone of the other answer choices is correct.
106Suppose multiple distinct file systems are stored on a single physical disk. The storage region in which each of these file systems is located is usually called a ________ .
- Apartition
- Bcylinder set
107In a file system, the unit of information to which protection is applied is called a
- Afile
- Bbyte
108The extension-- the part of a file name that usually appears at the end of a file name after a period -- usually indicates _____
- Athe type of information contained in the file
- Bwhich version, or generation, of the information this particular file represents
109Obviously applications depend on the content of files conforming to certain expectations. Is the structure of a file's content imposed by the operating system? And if so, why?
- AYes, because the size of each file must always be an exactly multiple of the size of a logical disk block (for example, a multiple of 4K bytes)
- BIt depends on the operating system and the file type whether any particular structure is imposed.
110In UNIX systems, regular files contain _____
- Auser information (text files, source code, data and executable programs)
- Binformation that is accessed on a scheduled basis
111A keyed file is one which _____
- Aeach record has a unique identifier that can be used in search operations
- Beach record is encrypted and the unencrypted version of the record can only be obtained by supplying the proper key to the decryption algorithm
112In UNIX, a character special file is
- Aa file which, when accessed, results in input/output operations on a device which is accessed one byte at a time
- Ba file that contains a single character such that any access triggers special security actions by the system.
113Suppose a UNIX file has multiple names (that is, multiple physical links). When is the file's content actually deleted?
- AWhen any of the links to the file are deleted.
- BWhen each of the links to the file has been deleted.
114What are the principal purposes of the open system call?
- Aprepare the open data structures used during the file's access
- Breturn a unique descriptor which is then used in other calls to access the open file
- CAll of the other answers are correct
115In most systems (certainly in UNIX), all files opened by a process are closed when the process terminates. Why, then, is there a separate system call that allows a user to explicitly close a file?
- AOpen files consume system resources, and there is a limit on the number of files a process may have open at the same time. Thus closing a file frees resources and allows additional files to be opened
- BIf the process wants to open the same file a second (or later) time with different access permissions (perhaps to write the file, when the first open was for read only), then the first open instance of the file must be closed
116When a UNIX file is open, there is a unique position associated with the file that indicates where the next read or write operation will commence. A system call is provided that allows a process to arbitrarily change this position. That system call is named _____
- Alseek
- Bgoto
117When a UNIX file is open, there is a unique position associated with the file that indicates where the next read or write operation will commence. After a read or write, how is that position altered?
- AIt is incremented by 1
- BIt is incremented by the number of bytes read or written
118A directory (sometimes called a folder) contains information about a collection of files. In UNIX systems the entries in a directory contain a file's name and _____
- Athe access rights for the file
- Bthe number of an i-node
119The size of a file is an important file attribute. In the CP/M operating system, what was interesting about file size attribute?
- AIt was only updated after the file was closed
- BIt was reported as the number of 128-byte sectors contained in the file.
120Most users usually say things like "this directory contains that file." What's technically incorrect about such statements?
- ADirectories don't contain files, but only information about files.
- BThe directory only contains the first logical block of the file; the remainder is stored elsewhere
121A user process may be allowed to read a directory, but never to write it. Why?
- AThe format of directory entries must be carefully preserved, so writing a directory is only indirectly possible by using system calls like read, write, delete, and rename
- BWriting a directory is not permitted because it may cause the size of a file to be reduced, which is not allowed
122Which of the following facts are used to construct a hierarchical file system?
- AThe number of entries in a directory is variable
- BA directory is similar to a regular file, but is uniquely identified as a directory by the filesystem
- Call of the other choices are correct
123A path for a file system is _____ .
- Aa sequence of directory and file names separated by a unique separator character
- Ba linked list of directory names
124A relative path does not begin with the root directory of a file system. Instead it begins with
- Athe home directory for the user who owns the process performing the access
- Bthe current working directory
125One of the advantages of using a relative path to a file instead of the corresponding complete(or absolute) path to the file is
- Ait is always shorter than the corresponding absolute path
- Bit is often more convenient
126In UNIX file systems, the directory named '.' is
- Aa link to the youngest (newest) subdirectory of the current directory.
- Ba link to the current directory
127Suppose a disk has tracks that contain 30 blocks each, and there are 6 tracks per cylinder. If the first block on the first track of the first cylinder is given the block number 1, then where would block number 217 be located?
- A2nd cylinder, 2nd track, 7th block
- B3rd cylinder, 2nd track, 7th block
128A contiguous region on a disk is
- Aa region that contains only tracks from the same cylinder.
- Bregion that includes only blocks with consecutive block numbers
129In UNIX, a set of structures is used to record the disk block numbers for those blocks belonging to a file. Suppose the first of these structures, an array with say 20 entries, records the disk block numbers of the first 20 blocks of the file. What happens if the file require smore than 20 disk blocks?
- AIf there are only 20 entries for disk block numbers then the file cannot become larger than that.
- BAn additional structure, called an indirect block, is used to hold additional disk block numbers for the file
130Some file systems use a linked structure to record the numbers of disk blocks used for each file (like the FAT file systems, for example). Which of the following operations is likely to be much more time consuming with such a scheme as compared with an indexed block number scheme (like that used by UNIX)?
- Areading the 100 bytes of a file following the last bytes read.
- Breading the last 100 bytes of a file
131Suppose a file system allocates only complete disk blocks to files, and further each disk block holds 4096 bytes. Assuming random file sizes, what is the size and type of fragmentation present in the file system?
- AThere is internal fragmentation of 2048 bytes average for each file.
- BThere is insufficient information available to answer the question.
132Which of the following is an advantage of using a logical block size that is larger than a disk's physical block size?
- AThe physical blocks belonging to a file will be grouped more closely, possibly resulting in less disk head movement.
- BFewer entries are required in the structure that maps file locations to disk block numbers
- CAll of the other answer choices are correct
133There are two common ways used to keep track of the unused (available for allocation) diskblocks in a file system. These are
- Abit maps and linked lists
- Bheaps and linked lists.
134Which of the following actions might occur when a failing disk block is detected?
- AAn alternate good block is used instead of the failing disk block.
- BThe read or write of the disk block is repeated to deal with transient errors
- CAll of the other answer choices are correct
135An image backup of a file system
- Acopies each block of the file system to the backup media without regard to the type of information it contains.
- Bcopies all the image files (e.g. JPG files) to the backup media
136Which type of file system backup can be used to defragment a file system?
- Aa backup of all files and directories sorted by disk block address
- Ba file-by-file backup.
137An incremental backup of a file system contains
- Aonly those files that have been created or changed since the last backup.
- Ba backup that uses multiple backup volumes, such as multiple CDs, DVDs, or magnetic tapes.
138When the contents of a disk block are needed by a user program, the system first
- Alooks for the block in a RAM disk
- Blooks for the block in the file system cache
139One approach to improving the performance of UNIX file systems that has been used in the past is to
- Aplace the block containing the i-node close to the blocks containing the file's data
- Bplace each logical block of the file's data on separate cylinders
140Which of the following decisions are likely to be mechanisms as opposed to policies?
- Ahow a process is represented
- Bwhat type of file system is available
141In a microkernel-based operating system
- Aonly a small number of mechanisms are provided in the kernel
- Bthere is little or no reliance on message-passing mechanisms found in the kernel
142A joe password is one which is identical to a username. For example, if a username is xy123, then the joe password is also xy123. Requiring users to avoid the use of such passwords is
- Anot something that is enforced by the operating system
- Ba policy
143Which of the following might be characterized as a denial of service attack on a system?
- Aflooding a system with requests
- Battempting to obtain a copy of the encrypted password file for a system
144Countermeasures are
- Asystem features designed to identify or eliminate the possibility of a security attack.
- Bautomatic logoff actions taken if a user does not utilize a system within a certain period of time.
145An access control list(ACL) is
- Aa list of pairs, each pair containing identification of a domain and a user.
- Ba list of users that are allowed to use a system
146An access control list (ACL) is associated with
- Aan object to which the ACL is to be applied
- Beach active process table entry
147A capability is
- Aa list of pairs, each pair containing identification of a protection domain and a user
- Ba pair containing an object identification and a set of access rights
148In a computer system characterized as having a tagged architecture,
- Aeach object in memory has a field identifying its data type
- Beach object in memory has a tag that is essentially a password that must be matched by a password associated with the process attempting to access the object
149Libraries of functions for most operating systems include facilities to open a directory, scan the directory sequentially or locate files with names matching a pattern, and to close the directory. Why are such functions provided?
- ASince the format of directory entries is usually complex and varies depending on the type of filesystem, it is convenient to be able to process all directories, regardless of the filesystem type, using one set of functions
- BAlthough a user can use the open, close, and read system calls on directory files, there isadditional information associated with a directory that can only be accessed using thesespecial library functions
150It is clear that reading from a disk is different than reading from a keyboard or a serial port. Some early operating systems used different system calls to read different devices, but UNIX systems have always provided a single read system call. How is this possible?
- AThe filesystem identifies the device being accessed, and when necessary, invokes the appropriate entry point in the device driver for the device, making the read system call device independent.
- BThe open system call determines the device type to be processed, and there are then multiple read function implementations, one for each device type.
151The acronym FAT stands for _____ .
- AFile Allocation Table
- BFormat And Test
152The principal difference between FAT-12, FAT-16, and FAT-32 is _____ .
- Athe number of bits in the maximum file size supported
- Bthe number of bits in each entry in the FAT
153The term metadata refers to _____
- Adata which uses more than one byte to represent a single character (e.g. UNICODE)
- Binformation about a file (e.g. the date and time a file was created)
154The block cache holds
- Aat most one copy of each disk block that has been accessed
- Ba copy of each directory block used in the absolute path to every open file
155When an additional block must be added to the block cache, and no unused block cache entries are available
- Athe entire block cache is cleared (after writing any blocks with modified content to disk).
- Bthe least recently used entry in the block cache is removed, writing it back to disk if it was modified, to provide an unused entry.
156A drawback of using linked allocation of the blocks belonging to a file is that
- Ait causes significant internal fragmentation of the disk space.
- Baccessing an arbitrary block of the file requires accessing each of the preceding blocks
157A drawback of using static allocation of the blocks belonging to a file is that
- Ait introduces significant external fragmentation of the disk space.
- Bif the initial allocation is too small, then the entire file cannot be written
158A common filesystem type that uses linked allocation with the indices (links) stored in a separate structure is
- Aa FAT filesystem.
- Ba log-structured filesystem.
159The CP/M operating system only recorded a file's size as the number of 128-byte physical sectors in the file. To identify the end of file in a text file, what did CP/M do?
- AIt padded the last sector of the file with blanks
- BIt stored a special character (control-Z) after the last character in the file
160ECC is an acronym referring to _____ .
- Aa technique used to dynamically extend the size of directory entries
- Ban error correcting code used with disks
161What does the UNIX sync program do?
- AIt periodically schedules the writing of all modified blocks in the cache to disk to limit the extent of damage caused by a system failure.
- BIt updates the last access time in a directory entry for all disk files to the time the file was last accessed
162A UNIX disk file F is opened by process A in a manner such that the first read from F will commence with the first byte of the file. Process A then creates a child process B. Process B then reads 100 bytes from file F, then process A reads 100 bytes from file F. What is the relationship between the 100 bytes read by B and the 100 bytes read by A?
- ABoth A and B obtain the first 100 bytes of the file
- BB's read obtains the first 100 bytes of the file, and A's read obtains the second 100 bytes of the file.
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- Quiz on Quiz 3, created by Myles Allbee on 04/05/2016.
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- Myles Allbee
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