CSE4001 Operating Systems Exam Review

A set of vocabulary flashcards covering memory management, CPU scheduling, page-replacement algorithms, and locality principles based on the CSE4001 Spring 2026 exam transcript.

Which of the following is the main purpose of memory management in an operating system?

A. To provide security for the system

B. To allocate memory to processes efficiently

C. To control the CPU usage

D. To manage input and output devices

B. To allocate memory to processes efficiently

In a paging system, the logical address space is divided into fixed-size blocks called:

A. Segments

B. Pages

C. Frames

D. Blocks

B. Pages

Which of the following is true regarding the concept of ”Thrashing”?

A. Thrashing occurs when the system spends most of its time swapping data between RAM and disk, causing a severe degradation in performance.

B. Thrashing refers to the process of loading the operating system into memory during startup.

C. Thrashing is a result of insufficient memory for a process’s execution and does not impact

overall system performance.

D. Thrashing only occurs when the CPU is heavily loaded, regardless of memory usage.

A. Thrashing occurs when the system spends most of its time swapping data between RAM and disk, causing a severe degradation in performance.

What is the primary advantage of using virtual memory in an operating system?

A. It increases the system’s security by preventing unauthorized access to memory.

B. It allows programs to run without being restricted by the physical memory size.

C. It ensures faster execution of processes by reducing disk I/O operations.

D. It prevents memory fragmentation by using a unified memory model.

B. It allows programs to run without being restricted by the physical memory size.

Which of the following is the main disadvantage of using paging in memory management?

A. It can lead to internal fragmentation.

B. It requires a large amount of CPU overhead due to address translation.

C. It does not support virtual memory.

D. It limits the maximum size of the process.

A. It can lead to internal fragmentation.

Which of the following best describes the “Working Set Model”?

A. It is used to track the number of pages a process uses, adjusting the number of frames based on the pages in use.

B. It refers to the allocation of memory in contiguous blocks to avoid fragmentation.

C. It is a paging algorithm used to decide which page should be swapped out.

D. It describes how segments are distributed across the system’s physical memory.

A. It is used to track the number of pages a process uses, adjusting the number of frames based on the pages in use.

What is the purpose of a page table in a paged memory system?

A. To store the actual data of the process in memory

B. To map virtual addresses to physical addresses

C. To store the execution instructions for processes

D. To manage I/O operations for processes in memory

B. To map virtual addresses to physical addresses

What is the primary goal of a CPU scheduling algorithm in an operating system?

A. To maximize the throughput of processes

B. To minimize the waiting time of processes

C. To ensure fair allocation of CPU time to processes

D. To eliminate the occurrence of deadlock

A. To maximize the throughput of processes

Which of the following scheduling algorithms is preemptive?

A. Round Robin (RR)

B. First-Come, First-Served (FCFS)

C. Shortest Job Next (SJN)

D. Priority Scheduling (Non-preemptive)

A. Round Robin (RR)

In the context of CPU scheduling, what does “starvation” refer to?

A. A situation where the CPU is idle for long periods

B. A situation where low-priority processes get indefinitely scheduled over high-priority processes

C. A situation where low-priority processes may never get executed

D. A condition where processes are stuck in an infinite loop

C. A situation where low-priority processes may never get executed

Which of the following is an advantage of the Shortest Job First (SJF) scheduling algorithm?

A. It always minimizes response time

B. It minimizes average waiting time for a set of processes

C. It is always preemptive

D. It provides equal CPU time to all processes

B. It minimizes average waiting time for a set of processes

The “Convoy Effect” happens when a long-running process takes up the CPU for a long time, shorter processes waiting behind it experience significant delays, leading to a slowdown in the overall system performance. Which of the following scheduling algorithms suffers from the Convoy Effect?

A. Round Robin (RR)

B. First-Come, First-Served (FCFS)

C. Shortest Job Next (SJN)

D. Priority Scheduling

B. First-Come, First-Served (FCFS)

What is the main disadvantage of the Round Robin (RR) scheduling algorithm?

A. It has a high average turnaround time

B. It is difficult to implement in real-time systems

C. It leads to higher waiting times for short processes

D. It may lead to poor performance if the time quantum is not properly chosen

D. It may lead to poor performance if the time quantum is not properly chosen

Which of the following scheduling policies is non-preemptive?

A. Round Robin (RR)

B. First-Come, First-Served (FCFS)

C. Multilevel Queue Scheduling

D. Shortest Job First (SJF)

B. First-Come, First-Served (FCFS)

In a Multilevel Queue Scheduling system, processes are divided into queues based on:

A. Their memory usage

B. Their arrival time

C. Their priority and/or type

D. Their CPU burst time

C. Their priority and/or type

Which of the following conditions can lead to a deadlock in a scheduling algorithm?

A. Prioritization of long jobs

B. Mutual exclusion, hold and wait, no preemption, and circular wait

C. Limited access to CPU resources

D. Prioritization of short jobs

B. Mutual exclusion, hold and wait, no preemption, and circular wait

Which scheduling algorithm would likely perform best in a system where all processes have similar lengths?

A. Shortest Job First (SJF)

B. Round Robin (RR)

C. First-Come, First-Served (FCFS)

D. Priority Scheduling

C. First-Come, First-Served (FCFS)

What is the main objective of a page-replacement policy in an operating system?

A. To minimize the number of page faults

B. To increase the process execution time

C. To decide which pages to swap out when a page fault occurs

D. To maximize the physical memory usage

A. To minimize the number of page faults

Which of the following page-replacement algorithms is known for its simplicity but poor performance in certain scenarios?

A. FIFO (First-In-First-Out)

B. LRU (Least Recently Used)

C. Optimal Page Replacement

D. Clock

A. FIFO (First-In-First-Out)

Which page-replacement algorithm replaces the page that will not be used for the longest time in the

future?

A. FIFO (First-In-First-Out)

B. LRU (Least Recently Used)

C. Optimal Page Replacement (OPT)

D. Clock

C. Optimal Page Replacement (OPT)

In the context of the Least Recently Used (LRU) page-replacement policy, which page is replaced when a new page must be loaded?

A. The page that has been in memory the longest

B. The page that has not been used for the longest period of time

C. The page that is currently not being used by any process

D. The page with the smallest size

B. The page that has not been used for the longest period of time

Which of the following page-replacement policies is considered the most optimal but also impractical to

implement in real-world systems?

A. FIFO (First-In-First-Out)

B. Optimal Page Replacement

C. LRU (Least Recently Used)

D. Clock

B. Optimal Page Replacement

The clock page-replacement algorithm is considered a practical approximation of which other algorithm?

A. FIFO (First-In-First-Out)

B. Optimal Page Replacement

C. Least Recently Used (LRU)

D. Least Frequently Used (LFU)

C. Least Recently Used (LRU)

In the FIFO (First-In-First-Out) page-replacement algorithm, which page is replaced when a new page

needs to be loaded?

A. The page with the least recent usage

B. The page with the smallest size

C. The page that has been in memory the longest

D. The page that is accessed next

C. The page that has been in memory the longest

In which of the following scenarios would FIFO page-replacement perform poorly?

A. When the memory access pattern has a high degree of locality

B. When processes are memory-intensive and perform sequential access

C. When the page access pattern is random

D. When the number of processes is minimal

A. When the memory access pattern has a high degree of locality

The LRU (Least Recently Used) algorithm suffers from which of the following practical limitations?

A. It requires too much memory to maintain a counter for every page

B. It requires maintaining a history of page accesses, which can be expensive in terms of time complexity

C. It is too simple and doesn’t provide efficient results

D. It only works well when the process access pattern is uniform

B. It requires maintaining a history of page accesses, which can be expensive in terms of time complexity

In the Optimal page-replacement algorithm, how does the operating system decide which page to replace?

A. It replaces the page that has been in memory the longest

B. It replaces the page that has not been used for the longest period of time

C. It replaces the page that will not be used for the longest period of time in the future

D. It replaces the page with the smallest memory footprint

C. It replaces the page that will not be used for the longest period of time in the future

What is a key advantage of the Clock page-replacement algorithm over FIFO?

A. It is simpler to implement than FIFO

B. It guarantees a lower page fault rate than FIFO

C. It approximates LRU with less overhead compared to maintaining an entire access history

D. It is less prone to the Belady’s anomaly compared to FIFO

C. It approximates LRU with less overhead compared to maintaining an entire access history

Given the access string sequence: 7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3. Assuming that we have 3 frames in memory, how many page faults will occur using the FIFO (First-In-First-Out) page-replacement algorithm?

A. 6

B. 7

C. 8

D. 10

D. 10

Given the access string sequence: 7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3. Assuming that we have 3 frames in memory, how many page faults will occur using the LRU (Least Recently Used) page-replacement algorithm?

A. 5

B. 6

C. 7

D. 9

D. 9

Given the access string sequence: 7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3. Assuming that we have 3 frames in memory, how many page faults will occur using the Optimal (OPT) page-replacement algorithm?

A. 5

B. 6

C. 7

D. 8

C. 7

Given the following access string: 1, 2, 3, 1, 4, 2, 1, 5, 6, 4, 3, 5. What will be the page fault count when using FIFO with 4 frames?

A. 6

B. 7

C. 8

D. 9

A. 6

Consider the access string: 1, 2, 3, 4, 5, 6, 7, 1, 2, 3. If we are using LRU with 3 frames, how many page faults will occur?

A. 5

B. 6

C. 7

D. 10

D. 10

Given the access string: 1, 2, 3, 1, 2, 4, 5, 6, 7, 4, 5. Assuming 3 frames, how many page faults occur using the Optimal (OPT) page-replacement algorithm?

A. 6

B. 7

C. 8

D. 9

B. 7

Consider the following access string: 7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3. How many page faults will occur if we use Clock with 3 frames?

A. 6

B. 7

C. 8

D. 9

D. 9

For the access string: 1, 2, 3, 1, 4, 2, 5, 6, 7, 1, 2, 4, 5, 6. How many page faults will occur when using

FIFO with 4 frames?

A. 8

B. 9

C. 10

D. 12

D. 12

Given the access string: 7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3, and 4 frames. How many page faults occur using LRU?

A. 6

B. 8

C. 9

D. 10

A. 6

If the access string is: 3, 2, 1, 4, 2, 3, 1, 5, 6, 4, and you use the Optimal (OPT) page-replacement algorithm with 3 frames, how many page faults will occur?

A. 5

B. 6

C. 7

D. 8

C. 7

What is the page fault rate in a virtual memory system?

A. The percentage of memory accesses that result in a page fault

B. The number of page faults divided by the total number of memory accesses

C. The ratio of pages that are loaded into memory at any given time

D. The number of pages swapped out of memory during execution

B. The number of page faults divided by the total number of memory accesses

Spatial locality refers to the tendency of a program to access:

A. A small set of pages frequently over time

B. Pages that are located near each other in memory

C. Memory locations that are close to one another in address space

D. Memory locations that are far apart in address space

C. Memory locations that are close to one another in address space

If a program exhibits temporal locality, it means that:

A. It frequently accesses the same memory locations within a short time period

B. It accesses memory locations that are close to each other in address space

C. It accesses memory locations that are scattered throughout the entire address space

D. It uses a small amount of memory over a long period of time

A. It frequently accesses the same memory locations within a short time period

Which of the following actions can reduce the page fault rate?

A. Increasing the page size indefinitely

B. Reducing the number of frames allocated to a process

C. Decreasing the number of processes running on the system

D. Increasing the number of frames allocated to a process (within reasonable limits)

D. Increasing the number of frames allocated to a process (within reasonable limits)

The working set of a program refers to:

A. The pages that are currently loaded in memory

B. The set of pages that a process is actively using within a given time window

C. The set of pages that have not been swapped out recently

D. The set of pages that have been accessed at least once during program execution

B. The set of pages that a process is actively using within a given time window

If a program exhibits poor locality of reference, it means that:

A. The program is accessing memory in a sequential or predictable manner

B. The program is accessing a small number of memory locations repeatedly

C. The program is accessing memory locations in an unpredictable or scattered manner

D. The program is using memory only for short periods of time

C. The program is accessing memory locations in an unpredictable or scattered manner

Which of the following is true for spatial locality?

A. It typically occurs when a program accesses the same data structure repeatedly

B. It suggests that a program will access the same set of memory locations over a long period of time

C. It suggests that when a program accesses a memory location, it is likely to access nearby locations soon after

D. It leads to increased cache misses and page faults

C. It suggests that when a program accesses a memory location, it is likely to access nearby locations soon after

How does temporal locality relate to the design of page-replacement algorithms?

A. Temporal locality encourages page-replacement algorithms that replace pages that are frequently accessed

B. Temporal locality suggests that pages accessed once will never be accessed again

C. Temporal locality encourages page-replacement algorithms to keep recently accessed pages in memory longer

D. Temporal locality has little impact on page-replacement algorithms

C. Temporal locality encourages page-replacement algorithms to keep recently accessed pages in memory longer

Which of the following will increase the page fault rate?

A. Increasing the number of frames allocated to each process

B. Using a large page size

C. Running too many processes that exceed the available memory

D. Optimizing the memory access pattern of a process

C. Running too many processes that exceed the available memory

The page fault rate is most strongly affected by:

A. The speed of the disk storage

B. The size of the cache memory

C. The size of the virtual memory address space

D. The locality of reference in the program’s memory access pattern

D. The locality of reference in the program’s memory access pattern

A program with a high page fault rate typically:

A. Has a small working set of memory pages

B. Accesses memory locations in a predictable, localized manner

C. Frequently accesses memory pages that are not currently in memory

D. Utilizes memory more efficiently by keeping pages in memory longer

C. Frequently accesses memory pages that are not currently in memory

The locality of reference is a concept that:

A. Refers to the amount of memory that is allocated to a program at runtime

B. Describes the pattern of memory accesses (whether they are concentrated or scattered over time and space)

C. Refers to the total number of page faults a program generates

D. Is unrelated to the performance of page-replacement algorithms

B. Describes the pattern of memory accesses (whether they are concentrated or scattered over time and space)

What is a common cause of thrashing in a system?

A. A high degree of spatial locality in memory accesses

B. Insufficient frame allocation to processes relative to their working set

C. Too many processes competing for a limited number of frames, leading to excessive page faults

D. Proper allocation of memory to processes with a large working set

C. Too many processes competing for a limited number of frames, leading to excessive page faults

How can thrashing be detected in a system?

A. By observing a significant decrease in the page fault rate

B. By monitoring the number of context switches that occur between processes

C. By monitoring the system’s CPU utilization and noticing that it is low while disk I/O (page swapping) is high

D. By tracking the average memory access time of all processes in the system

C. By monitoring the system’s CPU utilization and noticing that it is low while disk I/O (page swapping) is high

Which of the following is NOT a common symptom of thrashing?

A. High page fault rate

B. Low CPU utilization

C. High disk I/O activity due to frequent page swapping

D. Efficient use of CPU resources

D. Efficient use of CPU resources

Which of the following techniques can help reduce thrashing?

A. Increasing the degree of multiprogramming

B. Decreasing the size of each process’s working set

C. Allocating a sufficient number of frames to each process to match its working set

D. Using a non-preemptive scheduling algorithm

C. Allocating a sufficient number of frames to each process to match its working set

Which of the following scenarios is most likely to lead to thrashing?

A. A system with high CPU utilization and low disk activity

B. A system where most processes are accessing memory sequentially

C. A system with too many processes and not enough physical memory to hold their working sets

D. A system with a large amount of available physical memory and an optimal page-replacement algorithm

C. A system with too many processes and not enough physical memory to hold their working sets

How does thrashing impact the performance of an operating system?

A. It leads to increased CPU time and better throughput for processes

B. It improves the system’s ability to handle memory-intensive workloads

C. It causes a significant slowdown, as the system spends more time swapping pages than executing processes

D. It leads to more efficient use of disk storage

C. It causes a significant slowdown, as the system spends more time swapping pages than executing processes

One method to avoid thrashing is to:

A. Decrease the page size to reduce the number of page faults

B. Increase the number of processes running on the system

C. Control the degree of multiprogramming to ensure that the system does not overload physical memory

D. Increase the frequency of context switching between processes

C. Control the degree of multiprogramming to ensure that the system does not overload physical memory

Which of the following is a consequence of over-allocating memory to a process?

A. It may result in underutilization of memory, reducing the performance of other processes

B. It can increase the likelihood of thrashing, especially when multiple processes are running simultaneously

C. It will prevent thrashing by ensuring that the system has enough memory for all processes

D. It will always lead to better system performance as more memory is allocated to processes

A. It may result in underutilization of memory, reducing the performance of other processes

Adaptive replacement algorithms, such as Working Set Model, are designed to:

A. Decrease the memory footprint of processes to avoid thrashing

B. Optimize the CPU scheduling policy to prevent thrashing

C. Adjust the number of frames allocated to a process dynamically to match its changing working set

D. Increase the degree of multiprogramming to better utilize system resources

C. Adjust the number of frames allocated to a process dynamically to match its changing working set