Operating systems

Question 1

what is the list of things the operating system povides

Answer 1

manages peripherals
provides security
controls access
provides a platfrom to run software
utilities for system management
allows multi-tasking

Question 2

what are the types of UI

Answer 2

CLI
GUI

Question 3

how to does a GUI provide a user interface

Answer 3

windows
icons/images
menus
pointers

Question 4

How does a CLI provide a user interface

Answer 4

command lines in termals and etc

Question 5

how does an OS provide security

Answer 5

usernames and passwords
priviledge policys i.e student can only view their files but teacher can view their students files.

Question 5

What is the kernal

Answer 5

the centre of the operating system directly interacts with the hardware

Question 6

what are the 5 types of operating system

Answer 6

distributed
multi-user
multi-tasking
embedded
real time

Question 7

what is a distrubuted system

Answer 7

a distributed system uses multiple processors physicallly seperated to split tasks among them more powerful tasks completed quicker

Question 8

what is a multi-user system when is it used

Answer 8

allows multiple users to be on he server at once without security issues
used when resources need to be accessed simulatneously

Question 9

what is a multi-task system

Answer 9

allows multiple programs to run at once
never actually at once but appears like it

Question 10

what is paging in memory management

Answer 10

pages are all fixed sizes
physical divisions
i.e splits memory into 4Kbs and splits the program in the same intervals

Question 11

what is segmenting in memory management

Answer 11

segments are sections of the program
logical divisions
in order to fit free spaces

Question 12

what is scheduling

Answer 12

scheduling controls how the processor time is allocated which allows for multi-tasking

Question 13

what are the types of scheduling needed to know

Answer 13

round robin
first come first server
shortest job first
shortest time remaining job
shortest time remaining
multi-level feeback queue

Question 14

How does round robin work

Answer 14

processor time divided equally among jobs
given time slices

Question 15

pros and cons of round robin

Answer 15

low wait time

doesnt scale well more taskes smaller time slices less efficient

Question 16

how does first come first serve scheduling work

Answer 16

first job in is processed then move ot the next

Question 17

cons of first come first seve

Answer 17

processes may have to wait a long time

Question 18

what is shortest job first

Answer 18

the job that requires the shortest processor time is completed first

Question 19

what is shortest job remaining first

Answer 19

the job which requires the shortest processor time left is completed first

Question 20

pros and cons to shortest job first

Answer 20

reduces wait time (the long jobs are done last)
can cause starvation

Question 21

pros and cons to shortest time remaining

Answer 21

more efficient than shortest job first
can still lead to starvation

Question 22

what is multi-level feedback queue

Answer 22

uses queues where each task has a priority
if a process uses to much processor time given low priority
if sat idel for too long priority is moved up

Question 23

what is an interrupt used for

Answer 23

an interrupt is a way to signal to the CPU that a task needs the CPUs processor time

Question 24

what is the interrupt service routine

Answer 24

complete the FDE cycle
check priority of the interrupt is higher than the priority of the current application

if yes contents fo the registers stored as a stack

the address of the interrupt is coppied into the registers

when the ISR is complete the previous stack is popped back into the registers

Question 25

explain interrupt service routine [6]

Answer 25

completes current FDE cycle
interrupt register is checked
priority is checked
if higher
contents of registers are stored on the stack
Program counter is set to the address of the first interrupt instruction
when finished previous register stores are restored
FDE cycle resumes

Question 26

two people need to access the same device explain how operating sytems can allow that
[6]

Answer 26

multi user operating system
different username and passwords for each of them to log in
different settings
personalise their experience
access control rights can be allocated to each user
only access their own files
improve security

Question 27

state two sources of interrupts and why these sources have different priorities [4]

Answer 27

peripheral needs attention (i.e key board press)
power button / shutdown has been pressed

the shutdown must be handled immediately
it is important to provide a reponsive user experience
some interrupts are more important than other interrupts

Question 28

state two similarities between paging and segmentation

Answer 28

both a form of dividing up a program in order to be stored in Main memory
both allow more data to be stored when there is an insufficient amount of free RAM i.e by splitting up or using VM

Question 29

why is scheduling necarssary

Answer 29

in order to process as many jobs as possible
in as little time as possible
emsures all jobs are processed
efficient use of resources

Question 30

why is Memory managing necarssary

Answer 30

organise main memory
by changing logical addresses into physical addresses
allowing the computer to run when RAM is full
protect programs from each other
split up Tasks
allocates memory to tasks

Question 31

describe an embedded operating system [3]

Answer 31

any three from

Low level operating system
Stored in ROM
Designed to do a certain function
A system embedded into another device

Question 32

describe the term utility software

Answer 32

Specialist system software
Often with the OS
designed to help maintain the program

Question 33

What is the purpose of Anti-virus software [2]

Answer 33

prevents harmful program being ran or installed
if a virus is installed can be detected and removes it safely