operating systems

Question 1

what is the onion model?

Answer 1

the onion model describes each part of the computers operating system. the system is split into sections to make it easier to understand.

Question 2

what is hardware?

Answer 2

central processing unit
memory
storage

Question 3

what is kernel

Answer 3

controls the hardware directly
provides resources and services to applications
manages access to privileged reources

Question 4

what is applications?

Answer 4

programs to do something for the user

services are programs that run behind the scenes

Question 5

what is the shell?

Answer 5

also known as the command line interface

a programs that makes a set of commands available to the user

Question 6

what is UNIX?

Answer 6

an operating system which has been used continuously since 1969. it is efficient, stable and relatively secure.

Question 7

what is a file system?

Answer 7

part of the operating system that manages data.

Question 8

theory of trees?

Answer 8

a tree is a collection of nodes along a relation (parenthood)

Question 9

what are tracks?

Answer 9

concentric rings on the platter

Question 10

what are heads?

Answer 10

reads data from a platter

Question 11

what are cylinders?

Answer 11

collection of all tracks on platters

Question 12

what are sectors?

Answer 12

part of a track of data

Question 13

what is a partition?

Answer 13

subdivision of a disk

Question 14

what is a block?

Answer 14

the operating system views all disk space as an array of fixed size logical blocks

Question 15

what are the file allocation methods?

Answer 15

contiguous, chained and indexed

Question 16

let n be the number of blocks in a file. to find a particular block it takes how many disk accesses?

Answer 16

contiguous: O(1) about 1
chained: O(n) roughly n blocks
indexed: O(logk(n)) blocks