Lectures 1-5

Question 1

What is a DOS?

Answer 1

A disk operating system

Question 2

How do DOS’s work?

Answer 2

By using command line interfaces

Question 3

What are the purposes of a GUI?

Answer 3

• Execute programs
• File management
• Tools to configure and interact with OS which may be tightly linked

Question 4

What is the communication protocol used between the operating system and the window manager called?

Answer 4

X11

Question 5

What model does the X11 protocol use?

Answer 5

It uses a client-server model

Question 6

Why does the X11 protocol create minimal network traffic?

Answer 6

As it only has 4 packet types:

• Request
• Reply
• Event
• Error

Question 7

How has the role of the X11 protocol changed?

Answer 7

It has gone from originally drawing the display to now sending commands to the OS’s window managers

Question 8

What is an interrupt?

Answer 8

When an input happens (like a mouse click) it is passed directly to the processor which stops what it is doing to process this new command

Question 9

What is polling?

Answer 9

When the computer periodically checks for inputs. However this means that an input may be missed when the computer is listening for another.

Question 10

What are the OS’s services to the user?

Answer 10

• It creates an illusion of having direct access to the
  hardware
• It creates an illusion of being the only user (on a
  multiple user system)
• Multi Tasking

Question 11

What are the OS’s services to programs

Answer 11

• It will allow the program to use OS facilities if
  necessary such as the camera or microphone
• Give it the illusion of it being the only program running on the system at the time

Question 12

What are the pros of using a CLI over a GUI program?

Answer 12

• It provides a powerful way of interacting with the OS
• Often less frustrating for repetitive tasks
• Can combine multiple simple commands for complex tasks
• Great for controlling remote systems like servers

Question 13

What are the cons of using a CLI over a GUI program?

Answer 13

• Initially more difficult than a GUI progam
• Help is not as readily available
• Not as many safety belts as there are with a GUI
  program (Will not say ‘are you sure’)

Question 14

What does a shell do?

Answer 14

It provides a coating around the OS (Provides an interface)

Question 15

What are some shell features/utilities?

Answer 15

• File and directory management
• Ability to use internal and external commands
• Control of programs and processes

Question 16

What do file permissions do?

Answer 16

They allow enhanced security in a multi user environment. These can apply to bot files and their directories

Question 17

What are the different types of file links?

Answer 17

Hard links and symbolic links

Question 18

What are the properties of hard links?

Answer 18

• Gives multiple names for the same file
• Restricted to the same filesystem
• Cannot link directories like this, only files

Question 19

What are the properties of symbolic links?

Answer 19

• Redirect using the path name to another file (like
  saying ‘The file you want isnt here, it’s over there’)
• Can link to directories, or across filesystems

Question 20

How are links created?

Answer 20

Using the ‘ln’ or ‘ln -s’ command, then the name of the existing file and the new name afterwards

Question 21

How can output be redirected to a file rather than to a shell?

Answer 21

By using ‘>’ and ‘»’ (‘>’ is overwrite, ‘»’ is append) after a command and before the name of a file

Question 22

How can input be taken from a file rather than from a user’s input

Answer 22

By using

Question 23

How can the output of one command be given as the input to another command

Answer 23

By using a pipe symbol (‘ | ‘)

Question 24

What is the data throughput rate?

Answer 24

The number of bytes (or bits) that can go across the bus in one second

Question 25

What is the calculation to work out throughput rate?

Answer 25

throughput = speed x width