Question 1

Given the reference string of page accesses: 1 2 3 4 2 3 4 1 2 1 1 3 1 4 and a system with three page frames, what is the final configuration of the three frames after the LRU algorithm is applied?
A) 1, 3, 4
B) 3, 1, 4
C) 4, 1, 2
D) 1, 2, 3

Accepted Answer

The LRU (Least Recently Used) algorithm replaces the page that has not been used for the longest period of time.

Initially, all three page frames are empty.

1 is accessed and loaded into the first frame:

| 1 |   |   |

2 is accessed and loaded into the second frame:

| 1 | 2 |   |

3 is accessed and loaded into the third frame:

| 1 | 2 | 3 |

4 is accessed and replaces the least recently used page, which is 1:

| 4 | 2 | 3 |

2 is already in a page frame, so no replacement is needed:

| 4 | 2 | 3 |

3 is already in a page frame, so no replacement is needed:

| 4 | 2 | 3 |

1 is accessed and replaces the least recently used page, which is 4:

| 1 | 2 | 3 |

2 is already in a page frame, so no replacement is needed:

| 1 | 2 | 3 |

1 is already in a page frame, so no replacement is needed:

| 1 | 2 | 3 |

1 is already in a page frame, so no replacement is needed:

| 1 | 2 | 3 |

3 is already in a page frame, so no replacement is needed:

| 1 | 2 | 3 |

1 is already in a page frame, so no replacement is needed:

| 1 | 2 | 3 |

4 is accessed and replaces the least recently used page, which is 2:

| 1 | 4 | 3 |

Therefore, the final configuration of the three frames after the LRU algorithm is applied is 1, 4, 3, which corresponds to choice B.

Question 2

The most preferred method of swapping a process is
A) to swap using the file system.
B) to copy an entire file to swap space at process startup and then perform demand paging from the swap space.
C) to demand-page from the file system initially but to write the pages to swap space as they are replaced.
D) None of the above.

Accepted Answer

Demand-paging from the file system initially allows for efficient memory usage, but writing pages to swap space as they are replaced ensures that the system has enough space to perform other tasks. Swapping using the file system (A) can be slower and less efficient, while copying an entire file to swap space (B) may waste resources and take up unnecessary space.

Question 3

_____ is the algorithm implemented on most systems.
A) FIFO
B) Least frequently used
C) Most frequently used
D) LRU

Accepted Answer

LRU (Least Recently Used) algorithm is the commonly used algorithm in most systems to manage the cache memory. It removes the least recently used item from the cache memory when it is full and a new item needs space. This algorithm is efficient and ensures that the most recently used items are kept in the cache memory for faster access.

Question 4

The Second-Chance algorithm
A) is same as FIFO algorithm if all pages in memory have been referenced at least once since the last page fault.
B) is same as FIFO algorithm if none of the pages in memory have been referenced since the last page fault.
C) is same as LRU algorithm if all pages in memory have been referenced at least once since the last page fault.
D) is same as LRU algorithm if none of the pages in memory have been referenced since the last page fault.

Accepted Answer

The Second-Chance algorithm is similar to the FIFO algorithm, but it gives a second chance to a page that is about to be replaced. If the page has been referenced since the last page fault, it is moved to the end of the queue and is not replaced.

Question 5

The dirty (modify) bit identifies
A) a page that has been corrupted.
B) a page that needs to be reloaded when accessed.
C) a page that is shared by multiple processes.
D) a page that has been modified since it was loaded.

Accepted Answer

The dirty bit in the page table of an operating system identifies a page that has been modified since it was loaded into memory. This helps the operating system to know which pages need to be written back to disk when memory is needed for other processes. It is not related to corruption or sharing, and it does not indicate that the page needs to be reloaded when accessed.

Question 6

Given the reference string of page accesses: 1 2 3 4 2 3 4 1 2 1 1 3 1 3 and a system with three page frames, what is the final configuration of the three frames after the OPT algorithm is applied?
A) 1, 3, 4
B) 1, 2, 3
C) 2, 3, 4
D) 1, 2, 1

Accepted Answer

The answer of Given the reference string of page accesses:...

Question 7

In demand paging,
A) a page loaded in memory may never be accessed.
B) all pages that a program will access during execution are loaded in memory in the beginning.
C) a page is loaded in memory only when it is needed during execution.
D) a page is loaded in memory just before it is needed.

Accepted Answer

In demand paging, pages are loaded in memory only when they are needed during execution. This is done to optimize memory usage and avoid unnecessary loading of pages that may never be accessed during the execution of the program.

Question 8

If an instruction modifies several different locations, a page fault can be handled by
A) using temporary registers to hold the values of overwritten locations.
B) loading multiple pages in advance.
C) incorporating special hardware.
D) terminating the process.

Accepted Answer

Using temporary registers to hold the values of overwritten locations allows the instruction to complete without the need for additional pages to be loaded or special hardware. Terminating the process would not be desirable as it would result in loss of data and user frustration. Loading multiple pages in advance would be wasteful in terms of memory usage and may not always be practical. Incorporating special hardware would be a more complex and costly solution than using temporary registers.

Question 9

A drawback of equal or proportional allocation is that
A) they are very expensive to compute.
B) the processes that arrive earlier get more pages than the processes arriving later.
C) the allocation varies according to the degree of multiprogramming.
D) a high-priority process is treated the same as a low-priority process.

Accepted Answer

Equal or proportional allocation methods do not differentiate between processes based on their priority. Every process is allocated memory based on equality or proportionality without considering its priority, leading to a situation where high-priority processes are treated the same as low-priority processes.

Question 10

Counting based page replacement algorithms are not commonly used, because
A) they only approximate LRU.
B) they are expensive to implement, even though they incur the least number of page faults.
C)they do not approximate OPT replacement very well and their implementation is expensive.
D) they do not approximate OPT replacement very well, even though they are easy to implement.

Accepted Answer

Counting based page replacement algorithms are not commonly used because they do not approximate the optimal (OPT) replacement strategy well and their implementation is expensive.

Question 11

Optimal page replacement ____.
A) is the page-replacement algorithm most often implemented
B) is used mostly for comparison with other page-replacement schemes
C) can suffer from Belady's anomaly
D) requires that the system keep track of previously used pages

Accepted Answer

Optimal page replacement is primarily used as a benchmark for comparing the efficiency of other page replacement algorithms because it has the lowest possible page fault rate. It is theoretical and requires future knowledge of the reference string, which is not possible in practical systems.

Question 12

Suppose we have the following page accesses: 1 2 3 4 2 3 4 1 2 1 1 3 1 4 and that there are three frames within our system. Using the FIFO replacement algorithm, what is the number of page faults for the given reference string?
A) 14
B) 8
C) 13
D) 10

Accepted Answer

FIFO (First-In, First-Out) page replacement algorithm removes the oldest page in memory that was brought in first. For the given reference string and 3 frames, the process of page replacement goes as follows:1. Start with empty frames.2. Access pages in the order given: 1, 2, 3, 4, 2, 3, 4, 1, 2, 1, 1, 3, 1, 4.3. Each time a page needs to be loaded that isn't already in one of the frames, it's a page fault.- Initially, 1, 2, 3 are loaded into the frames (3 page faults).- 4 replaces 1 (1 page fault).- 2 and 3 are already in the frames, so no page faults occur.- 4 is already in the frame, so no page fault occurs.- 1 replaces 2 (1 page fault).- 2 replaces 3 (1 page fault).- 1 is already in the frame, so no page fault occurs.- 3 replaces 4 (1 page fault).- 1 is already in the frame, so no page fault occurs.- 4 replaces 2 (1 page fault).Total page faults = 3 (initial) + 1 (for 4) + 1 (for 1) + 1 (for 2) + 1 (for 3) + 1 (for 4) = 8.

Question 13

In Additional-Reference-Bits algorithm,
A) the least-recently used page is identified very efficiently on a page fault.
B) a group of pages that have not been used recently are efficiently identified.
C) a page that has been referenced most recently is identified.
D) None of the above.

Accepted Answer

Additional-Reference-Bits algorithm uses a reference bit for each page to keep track of when the page was last accessed. When a page fault occurs, the algorithm scans through all the pages to find a group of pages that have not been accessed recently based on their reference bit value, and selects one from the group to be replaced. Therefore, option B is correct as it identifies a group of pages efficiently. Option A and C are incorrect as they do not accurately describe the functionality of the algorithm.

Question 14

If an architecture has a move instruction with more than one word and at most one of the two operands may be an indirect memory reference, the minimum number of frames needed to run a process on this architecture is
A) 3
B) 4
C) 5
D) 6

Accepted Answer

In this architecture, we need 3 frames for the instruction to be executed:
1. Instruction Fetch
2. Operand Fetch (if one of the operands is a memory reference)
3. Execute

If we consider the process, we need two additional frames:
4. Memory Access (if an indirect memory reference is used)
5. Write back

Therefore, a minimum of 5 frames are needed to run a process on this architecture.

Question 15

Stack algorithms are a class of page replacement algorithms that
A) are implemented using stacks.
B) are guaranteed to incur the least number of page faults.
C) do not suffer from Belady's anomaly.
D) are guaranteed to incur no more page faults than FIFO page replacement algorithm.

Accepted Answer

Stack algorithms are designed to avoid Belady's anomaly, where adding more physical memory can result in more page faults. They achieve this by treating memory accesses as a stack, where the most recently accessed page is at the top. When a page fault occurs, the bottom of the stack is removed, and the new page is added to the top. This approach ensures that frequently accessed pages remain at the top of the stack and are less likely to be replaced. Therefore, stack algorithms are guaranteed to incur no more page faults than FIFO page replacement algorithm.

Question 16

Suppose we have the following page accesses: 1 2 3 4 2 3 4 1 2 1 1 3 1 4 and that there are three frames within our system. Using the FIFO replacement algorithm, what will be the final configuration of the three frames following the execution of the given reference string?
A) 4, 1, 3
B) 3, 1, 4
C) 4, 2, 3
D) 3, 4, 2

Accepted Answer

The answer of Suppose we have the following page accesses:...

Question 17

Which of the following is FALSE about reapers?
A) They may swap out a page from a process even when that process is not running.
B) They may use any page replacement algorithm to swap out pages.
C) They may swap out pages event when there are ample free frames available.
D) They implement a global page replacement policy.

Accepted Answer

Reapers typically swap out pages to manage memory efficiently, not when there are ample free frames available. Their role is to ensure that the system makes the best use of available memory, which includes keeping a buffer of free frames for immediate use, rather than swapping out pages unnecessarily.

Question 18

A free-frame list
A) is a set of all frames that are filled with all zeros.
B) is a set of all frames that are currently unallocated to any process.
C) is a set of all frames that are currently being shared by at least two processes.
D) is a set of all frames that are used for stack and heap memory.

Accepted Answer

A free-frame list is a list of all frames that are currently unallocated to any process. This list is used by the operating system to allocate frames to processes as needed.

Question 19

An advantage of virtual memory is that
A) a program can be much larger than the size of physical memory.
B) the programmers can concentrate programming the problem instead of worrying about the amount of physical memory available.
C) it provides a way to execute a program that is only partially loaded in memory.
D) All of the above.

Accepted Answer

Virtual memory allows a program to be much larger than the size of physical memory, and programmers can concentrate on programming the problem instead of worrying about the amount of physical memory available. It also provides a way to execute a program that is only partially loaded in memory. Therefore, all of the above choices are advantages of virtual memory.

Question 20

Anonymous memory of a process refers to
A) the pages not associated with the binary executable file of the process.
B) the pages associated with the binary executable file of the process.
C) the pages associated with the static data of the process.
D) the pages that cannot be swapped out of the physical memory.

Accepted Answer

Anonymous memory is memory that is not associated with any specific file, such as memory used for dynamically allocated data or program stack. Therefore, it refers to pages not associated with the binary executable file of the process.

Quiz 10: Virtual Memory

Given the reference string of page accesses: 1 2 3 4 2 3 4 1 2 1 1 3 1 4 and a system with three page frames, what is the final configuration of the three frames after the LRU algorithm is applied?

The most preferred method of swapping a process is

_____ is the algorithm implemented on most systems.

The Second-Chance algorithm

The dirty (modify) bit identifies

Given the reference string of page accesses: 1 2 3 4 2 3 4 1 2 1 1 3 1 3 and a system with three page frames, what is the final configuration of the three frames after the OPT algorithm is applied?

In demand paging,

If an instruction modifies several different locations, a page fault can be handled by

A drawback of equal or proportional allocation is that

Counting based page replacement algorithms are not commonly used, because

Optimal page replacement ____.

Suppose we have the following page accesses: 1 2 3 4 2 3 4 1 2 1 1 3 1 4 and that there are three frames within our system. Using the FIFO replacement algorithm, what is the number of page faults for the given reference string?

In Additional-Reference-Bits algorithm,

If an architecture has a move instruction with more than one word and at most one of the two operands may be an indirect memory reference, the minimum number of frames needed to run a process on this architecture is

Stack algorithms are a class of page replacement algorithms that

Suppose we have the following page accesses: 1 2 3 4 2 3 4 1 2 1 1 3 1 4 and that there are three frames within our system. Using the FIFO replacement algorithm, what will be the final configuration of the three frames following the execution of the given reference string?

Which of the following is FALSE about reapers?

A free-frame list

An advantage of virtual memory is that

Anonymous memory of a process refers to