Q.1 Which of the following is the primary goal of disk scheduling algorithms?
Minimize memory usage
Reduce CPU load
Minimize seek time
Increase cache size
Explanation - Disk scheduling algorithms aim to minimize seek time, which is the time taken by the disk arm to move to the desired cylinder.
Correct answer is: Minimize seek time
Q.2 In the FCFS disk scheduling algorithm, requests are served:
Based on priority
In the order they arrive
From nearest to farthest
By shortest seek time
Explanation - First-Come, First-Served serves disk requests in the sequence they enter the queue.
Correct answer is: In the order they arrive
Q.3 Which disk scheduling algorithm can lead to starvation?
FCFS
SSTF
C-SCAN
LOOK
Explanation - SSTF (Shortest Seek Time First) favors requests nearest to the current head position, which can cause far-off requests to starve.
Correct answer is: SSTF
Q.4 The C-SCAN scheduling algorithm treats the disk as:
A circular list
A linear array
A binary tree
A linked list
Explanation - C-SCAN scans in one direction and jumps back to the beginning, treating the disk as circular.
Correct answer is: A circular list
Q.5 Which algorithm is considered a variant of SCAN?
LOOK
FCFS
SSTF
FIFO
Explanation - LOOK is a variant of SCAN where the head moves only as far as the last request in each direction before reversing.
Correct answer is: LOOK
Q.6 Which disk parameter contributes most to access time?
Seek time
Rotational delay
Transfer time
Cache access
Explanation - Seek time, the time to move the read/write head, is the dominant factor in disk access time.
Correct answer is: Seek time
Q.7 Rotational latency is defined as:
Time to locate the cylinder
Time for the sector to rotate under the head
Time to read data from cache
Time to load the OS
Explanation - Rotational latency is the delay waiting for the desired sector to rotate under the disk head.
Correct answer is: Time for the sector to rotate under the head
Q.8 What does SSTF stand for?
Shortest Seek Time First
Shortest Service Time First
Smallest Seek Time File
Secondary Storage Task File
Explanation - SSTF stands for Shortest Seek Time First, serving the request closest to the current head position.
Correct answer is: Shortest Seek Time First
Q.9 Which of the following reduces variance in response time?
FCFS
SCAN
SSTF
Random scheduling
Explanation - SCAN moves the head in one direction fulfilling requests, reducing variance in response time compared to SSTF.
Correct answer is: SCAN
Q.10 Which disk scheduling algorithm is also called the elevator algorithm?
LOOK
SSTF
SCAN
FCFS
Explanation - SCAN is often referred to as the elevator algorithm since it moves like an elevator across disk tracks.
Correct answer is: SCAN
Q.11 In C-LOOK scheduling, the head:
Moves only within requested cylinders
Moves across all cylinders
Always scans linearly
Ignores cylinder positions
Explanation - C-LOOK is a variant of C-SCAN where the head only goes as far as the last request before wrapping around.
Correct answer is: Moves only within requested cylinders
Q.12 Disk storage is generally considered a type of:
Primary storage
Volatile storage
Secondary storage
Cache memory
Explanation - Disk storage is secondary storage because it is non-volatile and slower than main memory.
Correct answer is: Secondary storage
Q.13 Which factor does not affect disk access time?
Seek time
Rotational latency
Transfer time
Cache size of CPU
Explanation - CPU cache size does not affect disk access time, which is determined by disk parameters.
Correct answer is: Cache size of CPU
Q.14 What is the unit of disk transfer rate?
MB/s
MHz
ms
GHz
Explanation - Disk transfer rates are measured in megabytes per second (MB/s).
Correct answer is: MB/s
Q.15 Which scheduling algorithm provides the most uniform wait time?
FCFS
SCAN
C-SCAN
SSTF
Explanation - C-SCAN provides uniform wait time by treating the disk as circular and servicing requests evenly.
Correct answer is: C-SCAN
Q.16 Which part of the disk is accessed first?
Outer track
Inner track
Middle track
Random track
Explanation - By default, disks often start with the outermost track as it offers higher data transfer rates.
Correct answer is: Outer track
Q.17 Which disk scheduling algorithm is simplest but inefficient?
FCFS
SCAN
SSTF
LOOK
Explanation - FCFS is simple to implement but may result in long average seek times compared to others.
Correct answer is: FCFS
Q.18 Disk arm movement is minimized in which algorithm?
FCFS
SSTF
SCAN
C-LOOK
Explanation - SSTF minimizes arm movement by always choosing the nearest request to current head position.
Correct answer is: SSTF
Q.19 Which metric evaluates disk scheduling performance?
CPU utilization
Average seek time
Cache hit ratio
Instruction throughput
Explanation - Disk scheduling algorithms are mainly evaluated by average seek time and response time.
Correct answer is: Average seek time
Q.20 Which scheduling is best for systems requiring fairness?
SSTF
SCAN
C-SCAN
FCFS
Explanation - FCFS ensures fairness by servicing requests in the order they arrive, avoiding starvation.
Correct answer is: FCFS
Q.21 Which scheduling algorithm can be thought of as a circular SCAN?
C-SCAN
LOOK
SSTF
FIFO
Explanation - C-SCAN is a circular version of SCAN where the head jumps back after reaching the end.
Correct answer is: C-SCAN
Q.22 What is disk fragmentation?
Data stored contiguously
Data scattered across disk
Data stored in cache
Data compressed on disk
Explanation - Fragmentation occurs when files are stored in non-contiguous blocks, increasing access time.
Correct answer is: Data scattered across disk
Q.23 Which disk structure stores metadata about files?
Superblock
Inode
Sector
Cylinder
Explanation - Inodes store metadata like file size, ownership, and block locations in Unix-like systems.
Correct answer is: Inode
Q.24 The smallest unit of data storage on a disk is:
Track
Sector
Cylinder
Cluster
Explanation - A sector is the smallest storage unit on a disk, typically 512 bytes or 4 KB.
Correct answer is: Sector
Q.25 Which disk scheduling algorithm is best for real-time systems?
FCFS
SSTF
SCAN
Priority scheduling
Explanation - Real-time systems often prefer FCFS for its predictability and fairness.
Correct answer is: FCFS