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FIT9137 Introduction to computer architecture and networks - S1 2022 > Week 2 > Flashcards

Week 2 Flashcards

1
Q

What is an operating system?

A

A system hardware the manages processes/programs, hardware and the resources of the computer hardware.

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2
Q

What are the general categories for the various software sitting on top of the OS?

A
  • Utilities
  • Application Software

NOTE: This depends on the complexity and purpose of the software

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3
Q

What is the most important part of the OS in Unix/Linux?

A

The kernel

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4
Q

What is kernel mode?

A

This is a priority mode given to the OS to allow it to execute tasks relevant to the hardware requirements of the OS.

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5
Q

What is the file space that keeps files seperate and private between users in an OS?

A

The home directory

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6
Q

Modern OSs are multi-user systems. What does this mean?

A

This refers to how there can be multiple user accounts logging in on a single OS in a machine.

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7
Q

What is a time-slice?

A

This refers to the short time slot allocated to executing a process from a user/program.

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8
Q

What is a home directory for a user?

A

It is the folder designated by the OS to store a user’s personal data. At login, it is the starting folder (in Unix based systems).

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9
Q

What is the root directory?

A

It is the storage space for BOTH a systems AND user’s data. Highest level directory.

Denoted as / in unix based systems.

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10
Q

What is the full pathname?

A

It is the address of a file starting from the root directory.

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11
Q

What is a directory?

A

It is a organisational system, also known as a folder, that contains files and other pieces of data saved by the user and system.

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12
Q

What are the types of pathnames?

A
  1. Absolute

2. Relative

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13
Q

How to signify current directory?

A

use . to signify current directory

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14
Q

How to signify parent directory?

A

use .. to signify parent directory.

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15
Q

What is a process?

A

A program that is being executed by the CPU

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16
Q

What is a kernel process?

A

A process that is automatically managed by the OS

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17
Q

What is a user process?

A

This is a process that was initiated by the execution of a program by the user; anything a user can manage.

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18
Q

What is the command to run processes with security priveleges within a home directory? (*nix)

A

sudo -?

? = letter corresponding to command of interest

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19
Q

User priority?

A

Root/Admid > Normal > Guest

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20
Q

What is primary memory?

A

RAM - Random Access Memory (very limited, less limited these days)

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21
Q

What is secondary memory?

A

HDD/SDD (more abundant)

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22
Q

What happens if RAM is not managed?

A

Memory will be inefficiently used

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23
Q

What is context-switching?

A

This is when the data for a process is stored and paused which can be resumed. This data is stored in the L3 cache (shared between cores).

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24
Q

How to use the lost listing command?

A

ls -al (all files even hidden) OR ls -l (just folders)

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25
Q

What does a . signify when long listing?

A

These are hidden files.

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26
Q

How to show home directory of a user (*nix)

A

echo $HOME (caps important)

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27
Q

How to access home dir?

A

cd /home OR cd ~/ OR cd ~

28
Q

How to show current directory?

A

pwd (present working directory)

29
Q

What are the major functions of an OS?

A
  • File management
  • Memory Management
  • Process Management
29
Q

What are the major functions of an OS?

A
  • File management (basic)
  • Memory Management
  • Process Management
30
Q

What do file management systems accomplish?

A

They allow users to store information in fundamental units called ‘files’

31
Q

What does a file system driver allow the OS to accomplish?

A

Enables the creation, deletion and access of files.

32
Q

Do file systems need to be mounted before usable by OS?

A

Yes (hdd/sdd, flash drives)

33
Q

What are the three types of files in Unix based systems?

A
  • Ordinary files
  • Directory files
  • Special files
34
Q

What are ordinary files?

A

These are files that contain data and executables

35
Q

What are directory files?

A

These are files which can store other files and directories (sub directories)

36
Q

What are special files?

A

Any other type of file, usually represents hardware devices connected to the computer.

37
Q

What are unix file naming conventions?

A
  • Case sensitive
  • Characters used include lower and upper case letter, digits, dots (.) and commas (,)
  • Avoid using spaces and special characters
  • No notion of file extension (unlike is OSs like MS Windows) e.g. .exe/.txt etc.
    Although extensions exist, they have no meaning.
38
Q

In unix based systems, what is the default working directory after logging in?

A

The home directory

38
Q

In unix based systems, what is the default working directory after logging in?

A

The home directory

39
Q

How to determine current working directory? (which command in unix systems?)

A

pwd

40
Q

What does ls do?

A

lists files in current working directory

41
Q

What does ls -l do?

A

This is the long listing command, lists files within directory in more detail

42
Q

What does ls -al do?

A

This is the long listing command, lists ALL files (including hidden files/folders) within directory in more detail

NOTE: Files starting with a . are hidden files/folders.

43
Q

What does /etc contain?

A

This file/directory contains information on all configurations in the system

E.g.

/etc/group contains information about all group in the system

44
Q

What does is mean when Unix file system under the Unix kernel is flat?

A

This refers to how all objects (files, directories, IO devices etc.) are all considered files by the system depite the GUI representing them in a heiarchical order

45
Q

What is so important about the special file /etc/passwd?

A

This file contains information on ALL USERS on the system

46
Q

What does the commant cat do?

A

This displays the data in a file

47
Q

What does the pipe / | comand do?

A

This pipe / | command allows you to pass the output of another command to act as the input of another.

Format is x | y

x input (output of previous command)
y output
48
Q

What does the grep command do?

A

This grabs the data relevant to whatever is specified after the command

i.e. greb muni gets and information present in the directory that contains the string muni

49
Q

What does the /stat command do?

A

This shows the information in the file itself (NOT CONTENTS OF FILE)

49
Q

What does the /stat command do?

A

This shows the metadata of the file itself (NOT CONTENTS OF FILE)

50
Q

How does the unix kernel identify files?

A

Using a unique number called an inode number

51
Q

What are the three levels of file permissions?

A
  1. User
  2. Group
  3. Others
52
Q

What does the d or - mean when long listing?

A 
d = directory
- = normal file
53
Q

What are the kinds of permissions for each leve?

A
  1. Write
  2. Read
  3. Execute
54
Q

How many bits are used to represent permissions in unix?

A

9

55
Q

What are the different values that persmissions can represent?

A 
- = permission is off
r = read enabled
w = write enabled 
x = execute enabled
56
Q

What type of user has all permissions active?

A

A “superuser” or a root user

57
Q

What is a hard link and soft link?

A

These are alternative paths that point to file.
Hard links share the same inode number as their parent file (essentially a copy of file)
Soft links are purely shortcuts to their parent file

58
Q

What is the command to change file permissions in unix?

A

chmod

59
Q

What is the syntax for chmod?

A

chmod [-R] ‘who’ [op] [permission] file-list

60
Q

What do the different elements mean in the chmod syntax?

A 
chmod = command itself
-R = recursively (all files within the file modified)
who = one of user (u), group (g), other (o) and all (a)
op = one of add permission (+), remove permission (-) and reset permission (=)
permission = one of read (r), write (w) and execute (x)
61
Q

What are the four IDs for file access of processes? What do they determine?

A
  1. Real user-id
  2. Effective user-id
  3. Real group-id
  4. Effective group-id

They determine a processes access permissions to files/directories

62
Q

What is octal and how can we use this to change file permissions?

A

It is a base 8 notation (8 possible values, 0-7)
Can be used to indicate on or off for permissions

7 = rwx
4 = r
2 = w
1 = x
0 = off

chmod XYZ notation where X = u, Y = g and Z = o

63
Q

What does the kernel do?

A

It is responsible for managing low-level (hardware) tasks such as disk management, memory managent, IO management, resource allocation, process management, security/protection management.

FIT9137 Introduction to computer architecture and networks - S1 2022 (9 decks)

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