6

Question 1

open files

Answer 1

open-file table tracks open files
pointer points to last read/write location
file-open count - count of number of times a file is open

Question 2

sequential vs direct

Answer 2

sequential
-read next
-write next
-reset
direct
-read n
-write n
- postiion to n

Question 3

acyclic-graph directories

Answer 3

have shared subdirectories and files

Question 4

Hard link

Answer 4

poiint to same inode, if original file deleted the link remains

Question 5

soft link

Answer 5

point to file, if original file deleted it cant be accessed

Question 6

types of access

Answer 6

read
write
execute
append
delete
list

Question 7

attach a group to a file

Answer 7

chgrp g game
e.g. chmod 761 filename

Question 8

disk structure

Answer 8

disk subdivided into partitions
disks or partitions can be RAID protected against failure
can be used raw without a file system

Question 9

what is entity containing file system

Answer 9

volume, each volume containg a file system also tracks that file systems info in volume table of contents

Question 10

partition

Answer 10

can be volume containing a file system (“cooked”) or raw

Question 11

root partition

Answer 11

contains os, can hold other partitions

Question 12

general vs proc file system

Answer 12

general - Ext4 -> implements
proc- does not store data, contents computed on demand according to user I/O requests

Question 13

journaling

Answer 13

file system updates first written to a log file in the form of transactions

Question 14

variety of I/O devices

Answer 14

-storage
-transmission
-human-interface

Question 15

port

Answer 15

connection point for device

Question 16

bus

Answer 16

pci bus common in PCs and servers
expansion bus connects relatively slow devices

Question 17

controller

Answer 17

electronics that operate port, bus, device
contains processor, microcode, private memory, bus controller

Question 18

interrupts

Answer 18

cpu interrupt request line triggered by I/O device
interrupt handler - hadnles interrupts
interrupt vector - dispatch interrupt

Question 19

direct memory access

Answer 19

used to avoid programmed I/O
requires DMA controller
OS writes DMA command block into memory

Question 20

DMA (direct memory access)

Answer 20

feature of computer systems that allows certain hardware subsystems to access main system memory independently of CPU
processor uses dma to offload expensive memory operations

Question 21

DMA Transfer 6 step

Answer 21

1)device driver told to transfer data
2)dd tells drive controller to transfer “c” bytes to buffer at address “x”
3)drive controller initiates DMA transfer
4)DMA controller transfers bytes to buffer x increasing memory address and decreasing c until c ==0
5)when c =0 dma interruputs cpu to signal transfer complete