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. (4 pts) Write a few sentences to explain in which of the four IO software laye

ID: 3726870 • Letter: #

Question

. (4 pts) Write a few sentences to explain in which of the four IO software layers each of the following is done: Computing the track, sector, and head for a disk read Writing commands to the device registers Checking to see if the user is permitted to use the device Converting octal characters into a single binary value 4. (6 pts) Disk requests come into the disk driver for cylinders 40, 10, 20, 22, 42, 8, 2 and 29, in that order. A seek takes 5 msec per cylinder moved. Assuming the disk arm is initially at cylinder 25, compute the total seek time for each of the following: First-come, first-served Closest cylinder next Elevator algorithm, initially moving down (towards lower cylinder end)

Explanation / Answer

3)Answer:

I/O software layers:

I/O software layers consists four layers.Each layer has wee defined functionality and interface to the neighbouring layers.They are

->user level I/O software

->Device independent os software

->device drivers

->interrupt handlers

1)Computing the track,sector,and head for a disk read

It is the Device drivers layer

2)writing cache of recently used blocks

It is also Device drivers

3)Checking to see if the user is permitted to use the device

It is Device-independent os software

4)Converting binary integers to ASCII for printing

It is user level software