AMCAT Operating Systems Fundamentals 2

Question 1

Which page replacement algorithm is known as the optimal algorithm but is impractical for real-time use?

Accepted Answer

Optimal Page Replacement (OPT/Belady's)

Answer

The Optimal Page Replacement algorithm (also known as Belady's algorithm) replaces the page that will not be used for the longest time in the future. While it produces the minimum number of page faults, it requires future knowledge of memory references, making it impractical for real systems. It is used as a benchmark to evaluate other algorithms.

Question 2

What is the main advantage of a multilevel feedback queue scheduling algorithm?

Accepted Answer

It can adapt to the behavior of processes by moving them between queues of different priorities

Answer

A multilevel feedback queue scheduler dynamically adjusts process priorities based on their behavior. CPU-bound processes that use their full time quantum are moved to lower-priority queues, while I/O-bound processes that release the CPU early stay in higher-priority queues. This adaptability makes it versatile.

Question 3

In a system using demand paging, when is a page loaded into memory?

Accepted Answer

Only when the page is actually accessed and causes a page fault

Answer

Demand paging is a lazy loading strategy where pages are loaded into physical memory only when they are actually needed (demanded) by the process. When a process accesses a page not in memory, a page fault occurs, and the OS loads that specific page from disk.

Question 4

What is the Banker's Algorithm used for in operating systems?

Accepted Answer

Deadlock avoidance by determining if resource allocation will leave the system in a safe state

Answer

The Banker's Algorithm, proposed by Dijkstra, is a deadlock avoidance strategy. Before granting a resource request, it simulates the allocation to check if the system would remain in a 'safe state' — meaning all processes can still complete. If the allocation would lead to an unsafe state, the request is denied.

Question 5

Which of the following best describes thrashing in an operating system?

Accepted Answer

The system spending most of its time swapping pages in and out of memory rather than executing processes

Answer

Thrashing occurs when the system is overcommitted on memory, causing processes to continuously generate page faults. The OS spends almost all its time swapping pages between RAM and disk, and very little time doing actual useful computation. CPU utilization drops drastically during thrashing.

AMCAT Practice Test

AMCAT Practice Test

AMCAT Operating Systems Fundamentals 2