Quiz
CS1550 Final Prep - definitions
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Questions in this quiz (120)
1
If the working set is defined as the set of pages used by the 3 most recent memory access(es), what is the working set size right after the last reference in the following reference string?
Reference string: 0, 1, 2, 3, 0, 1, 4, 0, 1, 2, 3, 4, 5, 6, 3, 2, 1, 0.- A2
- B3
- C0
- D1
2The page offset in virtual addresses is the same size (number of bits) as the page offset in physical addresses.
- ATrue
- BFalse
3A page replacement algorithm typically involves the cooperation of the following components:
- AOS code that runs every page fault
- BMMU processing (in hardware) that occurs every memory access
- COS code that runs every memory access
- DOS code that runs every clock interrupt
4Virtual addresses must be the same size (number of bits) as physical addresses.
- ATrue
- BFalse
5How many entries does a conventional page table contain assuming a 32-bit logical address with an 8 KB page size?
- A2^19
- B2^13
- C2^20
- D2^32
6Fragmentation (both internal and external) does not occur in a paging memory system.
- ATrue
- BFalse
7All addresses inside page table entries of a two-level page table are physical addresses.
- ATrue
- BFalse
8The page offset in virtual addresses is the same size (number of bits) as the page offset in physical addresses.
- ATrue
- BFalse
9Smaller page size leads to:
- Afewer page faults
- Bless internal fragmentation
- Clikely more TLB misses
- Dreduced paging I/O throughput
- Esmaller page tables
10Right after writing to the virtual address 0xFFFAABBB, which of the following must be true? (Assume the page size is 4 KB.)
- Avalid[0xFFFAA] = 1
- Bmodified[0xFFFAABBB] = 1
- Cvalid[0xFFFAABBB] = 1
- Dmodified[0xFFFAA] = 1
11Virtual addresses must be the same size (number of bits) as physical addresses.
- ATrue
- BFalse
12
Imagine a virtual memory system with a page size equal to 4 KB. Assume that the first 5 entries in the inverted page table contain the following (process id, virtual page number) pairs:
(10, 4), (30, 6), (20, 2), (30, 1), (10, 7).
(Numbering of virtual pages and physical frames both start at 0.)
To which physical address will the virtual address 0x1200 accessed by process 30 translate?- A0x1200
- B0x300
- CPage Fault
- D0x3200
13
Imagine a virtual memory system with a page size equal to 4 KB. Assume that the first 5 entries in the inverted page table contain the following (process id, virtual page number) pairs:
(10, 4), (30, 6), (20, 2), (30, 1), (10, 7).
(Numbering of virtual pages and physical frames both start at 0.)
To which virtual address (if any) in the address space of Process 10 does the physical address 0x4500 correspond?- A0x7500
- B0x700
- C0x4500
- DThe physical address 0x4500 doesn't belong to Process 10
14A logical block number is a block index relative to the first block of the file.
- ATrue
- BFalse
15The blocks of a file are returned to the list of free blocks when:
- AThe link count inside the file's i-node reaches 0
- BThe file's owner deletes the file
- CThe file's permissions are changed so that even the file's owner cannot access the file
- DThe file's owner changes the file name
16Linked allocation may suffer from:
- AExternal Fragmentation
- BInternal Fragmentation
17Random block access is O(1) in the following disk block allocation techniques:
- AFile Allocation Table (FAT)
- Blinked allocation
- CIndexed allocation
- Dcontiguous allocation
18In modern magnetic disk drives, outer tracks have more sectors than inner tracks.
- ATrue
- BFalse
19When checking a file system for consistency, the list of used blocks and the list of free blocks are both populated from a single source, namely the i-nodes.
- ATrue
- BFalse
20Disk scheduling is important since it tries to decrease:
- Athe rotational delay
- Bthe polling time
- Cthe seek time
- Dthe transfer time
21In modern magnetic disk drives, outer tracks have more sectors than inner tracks.
- ATrue
- BFalse
22In the Unix file system, Access Control Lists (ACLs) apply to both files and directories, whereas in the Andrew File System (AFS), they only apply to directories.
- ATrue
- BFalse
23An access/protection matrix is generally dense.
- ATrue
- BFalse
24In Discretionary Access Control, the owner of a file cannot change the file's permissions.
- ATrue
- BFalse
25Cryptography must be unbreakable to be useful.
- ATrue
- BFalse
26The one-time pad algorithm is an example of unbreakable cryptography (i.e., it provides perfect secrecy).
- ATrue
- BFalse
27The one-time pad algorithm is an example of security by obscurity.
- ATrue
- BFalse
28In an access control matrix, the __________ right allows a process to change the entries in a row.
- Acopy
- Bcontrol/modify
- Cswitch/enter
29Which of the following is(are) necessary to protect against unauthorized modification of the access control policy of a system?
- ACryptographically-secured capabilities must be stored in kernel space
- BModifying and checking Access Control Lists is done via system calls
- CAccess Control Lists must be stored in kernel space
30An object with a high-security level in the Bell-La Padula multi-level security model may have a low integrity level in the Biba multi-level integrity level.
- ATrue
- BFalse
31Modern symmetric-key encryption is usually broken by brute-force.
- ATrue
- BFalse
32In a system that uses password salts, which of the following is stored inside the password file assuming h(.) is a cryptographically secure one-way hash function and || is the concatenation operation?
- Ah(password || salt) and salt
- Bh(password) and salt
- Cpassword and h(salt)
- Dh(password || salt) and h(salt)
33Which of the following is/are the advantage(s) of increasing the disk block size in a file system? (Choose all correct answers.)
- AIncreased disk read and write throughput
- BReduced disk block transfer delay
- CIncreased maximum file size for indexed allocation policy
- DIncreased disk space utilization
34In a file system, if all files are exactly 12KB, and the block size is 4KB, what is the percentage of disk space lost in internal fragmentation inside the file data blocks?
- Aroughly 30%
- B0%
- C100%
- D50%
35In a disk quota record, the number of block warnings left is initially equal to the soft block limit minus the hard block limit.
- ATrue
- BFalse
36Because modern systems have larger memory, disk write requests are mostly served from the disk block cache, and most requests that reach the disk are reads.
- ATrue
- BFalse
37In NAND solid-state disks, pages can be individually overwritten.
- ATrue
- BFalse
38An address generated by a CPU is referred to as a _________
- Aphysical address
- Blogical address
- Cpost relocation register address
- DMemory-Management Unit (MMU) generated address
39In the figure below, a logical address of 0x2002 will cause an error.
- ATrue
- BFalse
40Which page will be evicted next?
- AA
- BB
- CC
- DE
- EF
- FG
- GH
41In the previous example, which page will be selected by the Aging Replacement Algorithm right after Tick 4?
- APage 0
- BPage 1
- CPage 2
- DPage 3
- EPage 4
- FPage 5
42Given the logical address 0xAEF9 (in hexadecimal) with a page size of 256 bytes, what is the page offset?
- A0xAE
- B0xA
- C0xF9
- D0xF900
43Consider a logical address with 18 bits used to represent an entry in a conventional page table. How many entries are in the conventional page table?
- A262144
- B1024
- C1048576
- D18
44For a 32-bit architecture machine with a physical memory of 4GB, a page frame size of 4KB, what is the number of the Page Table Entries in the conventional PT?
- A1M (2^20)
- B4G (2^32)
- C2^12 (4K)
- DNot enough info
45Without a mechanism such as an address-space identifier, the TLB must be flushed during a context switch.
- ATrue
- BFalse
46When the page-fault rate goes above A in the following graph, the OS should try to ....
- AAllocate more frames to the process
- BAllocate less frames to the process
47After it is determined that a desired piece of data is not in memory, the following occurs:
- Acache miss
- Bvalid bit is set to 0
- Creference bit is set to 0
- Dpage fault
48[trick question] Before going to main memory, the desired data is searched in (mark all that apply)
- Acache (any caches)
- BMMU
- CTLB
- Dpage table
49In the following logical-to-physical mapping for contiguous file allocation, the block size is ______.
Given a logical byte number of 2000:
physical_block_num = (2000 / 1024) + 5 = 6
offset_in_block = 2000 % 1024 = 976- A512 bytes
- B1 KB
- C1000 bytes
50In the logical to physical mapping equations for linked allocation, if the next pointer is stored in the beginning of the block, which of the following calculations has (have) to change?
struct disk_block block
blockNo = start
effective_block_size = block_size – sizeof(uint)
logical_block_num = pos / effective_block_size
offset_in_block = pos % effective_block_size
for (j = 0; j < logical_block_num; j++) {
read disk block no. blockNo into block
blockNo = block.next_block
}- AOffset calculation only
- Bthe for loop
- Cboth offset calculation and the for loop
51Seek time is the time it takes the
- Asector to reach the disk head
- Bdisk arm to reach the requested track
- Cdisk arm to reach the requested sector
- Dsector to reach the requested track
52Mark all that apply for IntelliSeek in Hard Drives
- Aattempts to make seek delay = rotational delay
- Breduces power consumption in hard drives
- Cincreases noise in hard drives
- Dincreases delay in an attempt to reduce noise
53For a 32-bit architecture machine with a physical memory of 4GB, a page frame size of 4KB, a 1-level paging system, what is the size of the page table (IN BITS), where each entry has the physical frame number, a valid bit, a reference bit, a dirty bit, and a protection bit.
- A2^20
- B2^32
- C24*2^20
54Mark all correct statements about Contiguous Disk Block Allocation for a multi-block file
- AReduces overall transfer delay as compared to Linked Allocation
- BReduces overall seek delay as compared to Indexed Allocation
- CResults in inefficient disk utilization when files are allowed to grow arbitrarily
- DReduces overall rotational delay as compared to FAT Allocation
55Which i-node structure allow for unlimited (i.e., only limited by partition size) file sizes?
- Ai-node with double-indirect links
- Bi-node with triple indirect links
- Ci-node with start block number (contiguous allocation)
- Di-node with start and end block numbers (linked allocation)
- Ei-node with start and end block numbers (File Allocation Table)
56In the following pseudo-code, how many hardware interrupts are needed to transfer the buffer to the printer?
- Acount
- Bcount -1
- Ccount + 1
57Assume the page frame and disk block are the same size. A large disk block will cause
- Aa larger average rotational delay
- Ba larger minimum seek delay
- Ca larger page transfer delay
- Dmore internal fragmentation in physical memory
- Ea smaller page table
58The elevator algorithm and the shortest-seek-time-first algorithm have in common
- AThey both minimize seek delay
- BThey both minimize rotational delay
- CThey both minimize transfer delay
- DNone of the above
59Using the following access matrix, can a process running in Domain 3 write into both File 3 and File 2?
- Ayes
- Bno
60In the technique described in the previous slide (covert channel using file locking), a process wants to covertly send data one byte at a time into another process. How many files are needed?
- A8
- B9
- C7
61m is a message, {m}K is the message encrypted with a public key K, and [m]K−1 is the message mangled then decrypted by a private key K−1.
Given an active adversary who can read, modify, block, and replay messages, which security service(s) is(are) provided in the following scenario?
Alice sends ["Alice" ∣∣ R ∣∣ m]KA−1 to Bob, where R is a random number that was never used by Alice before and "Alice" ∣∣ R ∣∣ m is the concatenation of the string "Alice" with the number R and the message m.- AConfidentiality (i.e., no one other than Alice and Bob can see the contents of the message m)
- BSource Authentication (i.e., Bob's assurance that Alice and no one else has sent the message)
- CIntegrity (i.e., no one other than Alice and Bob can modify the contents of the message m)
- DAvailability
62How many page faults are needed to crack a password of length 10 characters using the TENEX password attack?
[blank_start]____[blank_end]- A10
63At 1 bit per 2^5 KB chunk, how many bytes of bitmap are needed per 1 GB of memory?
[blank_start]_____[blank_end]- A4096
64In contiguous allocation, the physical block number is the same as the logical block number.
- ATrue
- BFalse
65The disk blocks allocated to a file are returned to the list of free blocks when:
- AThe file's owner deletes the file
- BThe file's owner changes the file name
- CThe file's permissions are changed so that even the file's owner cannot access the file
- DThe link count inside the file's i-node reaches 0
66In a file system, if all files are exactly 32KB, and the block size is 4KB, what is the percentage of disk space lost in internal fragmentation inside the file data blocks?
- A0%
- Broughly 30%
- C50%
- D100%
67The Direct Memory Access (DMA) controller has to interrupt the CPU after every block transfer.
- ATrue
- BFalse
68Linked allocation suffers from external fragmentation.
- ATrue
- BFalse
69In a file system that uses 16-bit block numbers, what is the maximum partition size given that the block size is 8 KB.
- A128 MB
- B256 MB
- C512 MB
- D1024 MB
70Multi-level queues scheduling with ageing:
- Ais a fair scheduling policy
- Bis more general than multi-level queues with feedback
- Cmay cause starvation of some processes
- Dfavors long jobs
71In the Not Frequently Used page-replacement algorithm, which of the following ordered pairs (Reference bit, Dirty bit) represents a page that would be the worst choice for replacement?
- A(0,0)
- B(0,1)
- C(1,0)
- D(1,1)
72Optimal page replacement
- Ais the page-replacement algorithm most often implemented
- Bis used for comparison with other page-replacement schemes
- Ccan suffer from Belady's anomaly
- Drequires that the system keep track of previously used pages
73The page offset in virtual addresses is the same size (number of bits) as the page offset in physical addresses.
- ATrue
- BFalse
74A page replacement algorithm typically involves the cooperation of the following components:
- AMMU processing (in hardware) that occurs every memory access
- BOS code that runs every memory access
- COS code that runs every clock interrupt
- DOS code that runs every page fault
75All addresses inside page table entries of a two-level page table are physical addresses.
- ATrue
- BFalse
76In Project 3, right after writing to the virtual address 0xFFFAABBB, which of the following need(s) to be true? (Assume the page size is 4 KB.)
- Avalid[0xFFFAA] = 1
- Bmodified[0xFFFAA] = 1
- Cmodified[0xFFFAABBB] = 1
- Dvalid[0xFFFAABBB] = 1
77In modern magnetic disk drives, outer tracks have more sectors than inner tracks.
- ATrue
- BFalse
78A disk scheduler that assigns higher priority to the CPU-bound processes than the I/O-bound processes causes:
- AHigh CPU utilization and high I/O utilization
- BHigh CPU utilization and low I/O utilization
- CLow CPU utilization and high I/O utilization
- DLow CPU utilization and low I/O utilization
79Virtual addresses must be the same size (number of bits) as physical addresses.
- ATrue
- BFalse
80The working set is defined as the set of pages used by the 4 most recent memory accesses, what is the working set size right after the last reference in the following reference string?
Reference string: 0, 1, 2, 3, 0, 1, 4, 0, 1, 2, 3, 4, 5, 6, 3, 2, 1, 0.
[blank_start]______[blank_end]- A4
81When checking a file system for consistency, the list of used blocks and the list of free blocks are both populated from a single source, namely the free-block list.
- ATrue
- BFalse
82The Direct Memory Access (DMA) controller doesn't interrupt the CPU at all.
- ATrue
- BFalse
83Disk scheduling is important since it tries to decrease:
- AThe seek time
- BThe polling time
- CThe rotational delay
- DThe transfer time
84In a disk quota record, the number of files warnings left is initially equal to the soft block limit minus the hard block limit.
- ATrue
- BFalse
85External fragmentation does not occur in a paging memory system.
- ATrue
- BFalse
86Match each of the following file system inconsistency situations to the most accurate reason that caused the inconsistency.
A disk block is neither marked as free nor used by any i-node. [blank_start]________[blank_end]
A disk block is both marked as free and as used by an i-node. [blank_start]_________[blank_end]
A disk block is marked as used by two different i-nodes. [blank_start]___________[blank_end]
A disk block appears twice in the free-block list. [blank_start]_________[blank_end]
A. A system crash occurred right after removing the block from the free-list and before adding it to the i-node
B. The disk block was marked as used by two different i-nodes.
C. The disk block was both marked as free and as used by an i-node.
D. A system crash occurred right after adding the block to the free-list and before removing it from the i-node- AA
- BB
- CC
- DD
- EA
- FB
- GC
- HD
- IA
- JB
- KC
- LD
- MA
- NB
- OC
- PD
87The indexed allocation technique of disk blocks suffers from external fragmentation.
- ATrue
- BFalse
88Multi-level queues scheduling with aging:
- Ais a fair scheduling policy
- Bfavors long jobs
- Cmay cause starvation of some processes
- Dis more general than multi-level queues with feeback
89In the Not Frequently Used page-replacement algorithm, which of the following ordered pairs (Reference bit, Dirty bit) represents a page that would be the best choice for replacement?
- A(0,0)
- B(0,1)
- C(1,0)
- D(1,1)
90Mark all correct statements about the optimal page replacement algorithm (OPT)
- Ais the page-replacement algorithm most often implemented
- Bis used for comparison with other page-replacement schemes
- Ccan suffer from Belady's anomaly
- Drequires that the system keep track of previously used pages
- Eis a stack page replacement algorithm
91All addresses inside inverted page table entries are physical addresses.
- ATrue
- BFalse
92In memory paging systems, virtual pages and physical frames have the same size.
- ATrue
- BFalse
93Smaller page size leads to:
- Asmaller page tables
- Bmore TLB misses
- Cfewer page faults
- Dreduced paging I/O throughput
- Eless internal fragmentation
94(Mark all correct answers.) In Project 3, right after reading from the virtual address 0xFFFAABBB, which of the following need(s) to be true? (Assume the page size is 4 KB.)
- Avalid[0xFFFAA] = 1
- Bmodified[0xFFFAA] = 1
- Cmodified[0xFFFAABBB] = 1
- Dvalid[0xFFFAABBB] = 1
95In modern magnetic disk drives, outer tracks have more sectors than inner tracks.
- ATrue
- BFalse
96In virtual memory paging systems, the virtual address space and the physical address space have to be the same size.
- ATrue
- BFalse
97The difference between the Not Recently Used (NRU) page-replacement algorithm and the Not Frequently Used (NFU) algorithm is that in NRU the counter inside each Page Table Entry is incremented every memory access, whereas in NFU it is incremented every clock interrupt.
- ATrue
- BFalse
98Virtual memory is not feasible to implement on 64-bit machines because the page table size is too large to fit in main memory.
- ATrue
- BFalse
99In a three-level page table architecture, the second-level and third-level page tables are paged in and out of main memory like normal pages.
- ATrue
- BFalse
100The i-nodes for directories are stored on the heap, whereas the i-nodes for files are stored in the file allocation table
- ATrue
- BFalse
101To get notified when a page is accessed, an operating system may set the valid bit of the Page Table Entry (PTE) to false even though the page is in memory.
- ATrue
- BFalse
102The optimal page replacement algorithm (OPT) is a stack page-replacement policy.
- ATrue
- BFalse
103In magnetic hard disks that use the IntelliSeek technology, the rotational delay and the transfer delay are overlapped; the sector rotates to the head, and at the same time, the head rotates to reach the sector.
- ATrue
- BFalse
104The read and write throughput of a Solid State Disk (SSD) degrades as the disk fills up with data.
- ATrue
- BFalse
105Two directories, dirA and dirB, link to a file named fileA. After the file is deleted from dirA, but not from dirB, the blocks of the file are returned to the free-block list
- ATrue
- BFalse
106A disk block is neither in the free-block list not used by an i-node. What are possible reasons for that situation?
- AThe block was allocated to two different i-nodes then a system crash occurred
- BA system crash occurred after the block was removed from the free-block list but before it was allocated to an i-node
- CA system crash occurred after the block was allocated to an i-node but before it was removed from the free-block list
- DA system crash occurred after the block was removed from an i-node but before it was returned back to the free-block list
107In a virtual memory system that uses two-level page tables, which part of the virtual address is copied verbatim to the corresponding physical address?
- Apage offset
- Bfirst-level page number
- Cframe number
- Dsecond-level page number
108In the Working Set Clock (WS-CLOCK) page replacement algorithm, if the counter of a page is 10000000 right after clock tick X and the page has been referenced between clock ticks X and X+1, what is the value of the page’s age (global counter - local counter) right after clock tick X+1? Assume that the global counter has the value 1110001110
- A01000000
- B10000000
- C1110001110
- D0
109(Mark all that apply) In a virtual memory system with two-level page tables, when might a page fault occur?
- Aa requested page is not in memory
- Ba TLB hit occurs and the first-level page table is not in memory
- Ca TLB miss occurs and a second-level page table is not in memory
- Da TLB hit occurs and a second-level page table is not in memory
110Which of the following is a side effect of having a large disk block cache?
- AThe disk sees more reads than writes
- BThe disk sees more writes than reads
- CThe SCAN disk scheduling algorithm outperforms FIFO
- DThe average page fault rate decreases
111The page fault rate of a process increased after increasing the number of physical frames assigned to the process. Select all possible reasons for that behavior.
- AThe working set of the process increased
- BThe system used FIFO page-replacement and suffered from Belady’s anomaly
- CA global page replacement policy was used
- DThe system used an inverted page table
112The average disk read time of a process decreased when it was run concurrently with other processes. Select all possible reasons for that behavior.
- AMore dirty pages were written to disk
- BMore disk reads were served from the disk block cache
- CContext switching overhead decreased
- DPage locking happened more frequently
113The following code snippet represents logical to physical mapping in a file system. pos is the logical byte number and index block is an index block.
logical_block_no = pos / 4096;
offset_in_block = pos % 4096;
physical_block_no = index_block[logical_block_no];
What is the block size in the file system?- A1024 bytes
- B4096 bytes
- Cindex.block[logical_block_no]
- Dnot enough info
114The following code snippet represents logical to physical mapping in a file system. pos is the logical byte number and index block is an index block.
logical_block_no = pos / 4096;
offset_in_block = pos % 4096;
physical_block_no = index_block[logical_block_no];
How many levels of indexing are used for that file?- A0
- B1
- C2
- D3
115The following code snippet represents logical to physical mapping in a file system. pos is the logical byte number and index block is an index block.
logical_block_no = pos / 4096;
offset_in_block = pos % 4096;
physical_block_no = index_block[logical_block_no];
Assuming that a block number takes 32 bits, what is the maximum file size?- A1MB
- B2MB
- C4MB
- D16MB
116The two main approaches for keeping track of free disk blocks are:
- ABuffering and polling
- BBitmap and linked list of free blocks
- CParity and RAID
- Di-node and File Allocation Table
117The FAT-32 file system has 28-bit block numbers and 32-bit sector number. Given that the sector size is 512 bytes and the block size is 64 sectors, what is the maximum partition size?
- A1 TB
- B2 TB
- C4 TB
- D8 TB
118(Mark all that apply). Which of the following items is/are stored in the global open-file table?
- Ai-node number
- Bfile access mode (e.g. read-only)
- Ccurrent position in file
- Dquota pointer
119Consider a file system with 20-byte disk blocks. A linked list is used to keep track of the free blocks. How many blocks would the linked list take when there are 10 free blocks? Assume that the block number takes four bytes and that each node in the list is one disk block and contains a pointer to the next node.
Linked-list size = [blank_start]________[blank_end] blocks- A3
120Consider an i-node that contains nine direct entries, two single indirect entries, and four double indirect entries. Assume the block size is 512 bytes and that the block number takes four bytes. How many index blocks are needed when the file is at its maximum size?
Number of index blocks = [blank_start]______[blank_end] blocks- A518
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