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OCR A-level Computer Science > 1.3 Exchanging data > Flashcards

1.3 Exchanging data Flashcards

1
Q

What is compression?

A

the process used to reduce storage space required by a file

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2
Q

What is the purpose of compression? (4)

A

-reduce file sizes
-reduce download times
-reduce storage requirements
-make best use of bandwidth (amount of data sent at a time)

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3
Q

What are the two categories of compression?

A

-lossy
-lossless

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4
Q

What do we mean by lossy compression?

A

a type of compression that reduces sizes of files by removing some of its information e.g. a more pixelated image/less clear audio recording

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5
Q

What type of files are used for lossy compression?

A

-sound files
-image files

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6
Q

What do we mean by lossless compression?

A

a type of compression where the original file can be recovered

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7
Q

What type of files are used for lossless compression?

A

-text files
-executable files

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8
Q

What are the two methods to use lossless compression?

A

-run length encoding
-dictionary encoding

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9
Q

What is run length encoding?

A

a form of lossless compression where repeated values are removed and replaced with the single data item followed by the number of times it should be repeated
e.g. AAAAABCCC would give A5B1C3

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10
Q

What is an inefficiency when using run length encoding?

A

-relies on consecutive pieces of data being the same
- little repetition = little reduction in file size

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11
Q

What is dictionary encoding?

A

a form of lossless compression which replaces commonly repeated data with an index and saves the compressed data together with a dictionary that links the frequently repeated data to their corresponding index

e.g. I 1
went 2
to 3
the 4
park 5
. 6
[space] 7

this dictionary would then help decode 17273747576

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12
Q

What is something to remember about dictionary encoding?

A

if the compressed data isn’t transferred alongside its dictionary, the data cannot be used

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13
Q

What do we mean by encryption?

A

the process of encoding a message so it can be read only the sender and the intended recipient

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14
Q

What do we mean by encoding a message?

A

converting the message from plain text to cyphertext

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15
Q

What are the two types of encryption?

A

-symmetric
-asymmetric

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16
Q

How does symmetric encryption work?

A

-both sender and receiver share the same private key
- key is used for both encrypting and decrypting data

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17
Q

How can symmetric encryption by intercepted? (2)

A

-interception of the key
-duplicating the key to have a copy

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18
Q

How does asymmetric encryption work?

A

-two keys used: public & private
-public key can be published anywhere but private must be secret (together known as a key pair)
-messages encrypted with public key can only be decrypted with the corresponding private key

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19
Q

What is hashing?

A

a process where an input (called a key) is turned into a fixed sized value (a hash)

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20
Q

How are keys turned into a hash?

A

uses algorithms called hash functions

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21
Q

What is something to know about hashing?

A

-one way process: the output of a hash function cant be reversed to form the key
-the key cant be reversed to gain the passwords

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22
Q

What are hash tables?

A

a data structure which holds key-value pairs

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23
Q

What do we mean by a collision?

A

when two keys produce a same hash

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24
Q

How can we overcome collisions?

A

-storing items in a list under a new hash value
-using a second hash function to generate a new hash

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25
Q

What would a good hashing function consist of? (4)

A

-low chance of collisions
-minor changes in data causing large changes to the hash
-quick to calculate
-provides smaller output compared to the input

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26
Q

What is a database?

A

an organised collection of data

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27
Q

What is an entity?

A

an item of interest about which information is stored

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28
Q

What is an attribute?

A

characteristics of an entity

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29
Q

What is a relational database?

A

a database which recognises the differences between entities by creating different tables for each entity

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30
Q

What is a table?

A

an entity/file

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31
Q

What is a record?

A

a row of data within a table

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32
Q

What is a field?

A

a column of data within a table

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33
Q

What is a flat file?

A

a database that only contains a single table

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34
Q

How are flat files written out?

A

Entity1(attribute1, attribute2, attribute3…)

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35
Q

What is a primary key?

A

a unique identifier for each record (row) in the table

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36
Q

What is a composite key?

A

a primary key composed of more than one attribute

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37
Q

What is a foreign key?

A

an attribute which links two tables together
- exists in one table as the primary key, acts as the foreign key in another

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38
Q

What does a secondary key do?

A

allows a database to be searched quickly

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39
Q

What are the different entity relationships possible? (3)

A

-one to one
-one to many
-many to many

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40
Q

Draw a diagram showing the entity relationships

A

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41
Q

Describe the one-to-one entity relationship

A

each entity can only be linked to one other entity and vice versa

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42
Q

Describe the one-to-many entity relationship

A

one table can be associated with many other tables and vice versa

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43
Q

Describe the many-to-many entity relationship

A

when one or more items in one table can have a relationship to one or more items in another table and vice versa

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44
Q

What do we mean by normalisation?

A

the process of coming up with the best possible layout for a relational database

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45
Q

What are some things normalisation does?

A

-remove unnecessary duplicates
-consistent data throughout linked tables
-records can be added and removed without issues
-complex queries can be carried out

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46
Q

What are the types of normalisation?

A

-1NF (1st normal form)
-2NF (2nd normal form)
-3NF (3rd normal form)

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47
Q

What does 1NF do?

A

makes sure there’s no attribute that contains more than a single value

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48
Q

What does 2NF do?

A

makes sure that the relational database:
-hasno partial dependencies
-is in 1NF

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49
Q

What does 3NF do?

A

makes sure the relational database:
-is in 2NF
-contains no non-key dependencies (attributes which depend of value of primary key only)

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50
Q

What is indexing?

A

a method used to store the position of each record when ordered by a certain attribute

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51
Q

What is indexing used for?

A

to look up and access data from the database quickly

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52
Q

What is something to remember when indexing records?

A

the primary key is automatically indexed

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53
Q

How is data entered into databases?

A

-manually entered
-scanned

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54
Q

What is SQL?

A

a declarative language used to manipulate databases
- stands for structured query language

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55
Q

What are all the SQL commands? (9)

A

SELECT
FROM
WHERE
ORDER BY
JOIN
DELETE
INSERT INTO
DROP
CREATE

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56
Q

What do the SELECT, FROM, WHERE commands do?

A

SELECT- collects fields from a given table
FROM- specifies which table/tables the info will come from
WHERE- specifies the search criteria

57
Q

What does the ORDER BY command do?

A

specifies whether you want data to be in ascending or descending order

58
Q

What does the JOIN command do?

A

provides a method of combining rows from multiple tables based on a common field between them

59
Q

What does the CREATE command do?

A

allows you to make new databases

60
Q

What does the DELETE command do?

A

deletes a record from a table

61
Q

What does the INSERT INTO command do?

A

inserts a new record in a table

62
Q

What does the DROP command do?

A

removes a whole database/table

63
Q

What do we mean by referential integrity?

A

the process ensuring consistency
- makes sure that info isn’t removed if required elsewhere in a linked system

64
Q

What is a transaction?

A

a single operation executed on data

65
Q

What is ACID and what does it stand for?

A

properties required by all database transactions

-atomicity
-consistency
-isolation
-durability

66
Q

What is atomicity?

A

when a transaction must be processed in its entirety or not at all

67
Q

What is consistency?

A

when a transaction must keep the referential integrity rules between linked tables

68
Q

What is isolation?

A

simultaneous execution of transactions must lead to the same result as if they were executed one after the other

69
Q

What is durability?

A

when a transaction has been executed it will remain so

70
Q

What is record locking?

A

the process of preventing simultaneous access of records in a database

71
Q

What is record locking used for?

A

to prevent inconsistencies or loss of updates

72
Q

What is the problem with record locking?

A

deadlock- where processes have effectively locked themselves out because they are all waiting on each other to do something

73
Q

What is redundancy?

A

the process of having one or more copies of data in physically different locations
- means if there is any damage to one copy, others can be recovered

74
Q

What is a network?

A

two or more computers connected together that can transmit data
- allows computers on opposite sides of the globe to communicate with each other

75
Q

What are some positives of networks?

A

-users can share files
-communication with other people
-users can access files from any computer on the network

76
Q

What are some downsides of networks?

A

-increased security risks to data
-malware and viruses spread easily between computers
-if the server fails, the computer connected to it may not work
-computers may run slower if there is a lot of data travelling on the network

77
Q

What are protocols?

A

set of rules defining how two devices communicate with each other

78
Q

What is the TCP/IP stack?

A

transmission control protocol/internet protocol
-stack of networking protocols that work together passing packets during communication

79
Q

What are the protocol layers?

A

-application
-transport
-network
-link

80
Q

Describe the application layer. What protocols are used during this?

A

specifies which protocols need to be used in order to relate the application that’s being sent
protocols: FTP, HTTP, HTTPS, SMTPP, IMAP

81
Q

Describe the transport layer. What protocols are used during this?

A

-sets up communication between two hosts
-splits data into packets
-requests transmission of any lost packets
protocols: TCP, UDP

82
Q

Describe the network layer. What protocols are used during this?

A

-addresses and packages data for transmission
-router forwards packets across the network
protocol: IP

83
Q

Describe the link layer

A

-the connection between network devices
-adds the MAC address identifying the Network Interface Cards of the source and destination computers

84
Q

What happens with the TCP/IP stack on the recipients computer?

A

the layers occur again in reverse:
-link- removes the MAC addresses
-network- removes the IP addresses
-transport- removes the port number and reassembles the packets
-application- presents the data to the recipient in the form it was sent

85
Q

How can we remember all the layers of the TCP/IP stack?

A

Always Think In Layers (ATIL)

86
Q

What is LAN? What hardware does it need to become connected?

A

local area network
-a network that is spread over a small geographical area
- UTP cable
- fibre optic
- wi-fi

87
Q

What is a WAN? What hardware does it need to become connected?

A

wide area network
-a network that is spread over a large geographical area (multiple LAN in different areas which are connected)
- telephone lines
-fibre optic cables
-satellite links

88
Q

What is DNS?

A

domain name system
-method of naming internet resources
-translates domain names into IP addresses when we access a website

89
Q

How does the DNS translate the domain name into the IP address when a user enters a website name? (6)

A

-client enters URL into browser
-browser checks local cache
-URL passed to DNS recursive resolver, checks cache
-URL passed to the root name server (contains address of the .com server)
-URL passed to the top level domain server (contains address of all sites register under .com)
-URL passed to the authoritative server (server of the actual requested device

90
Q

What happens when the DNS cant find the IP address of the website URL?

A

outputs an error message (e.g. error code: 404, website address not found)

91
Q

What is circuit switching?

A

a method of communication where a direct link is created between two devices
- Link maintained for the entire conversation
- The two devices must transfer and receive data at the same rate

92
Q

What are some +/- of circuit switching? (2, 3)

A

+the data arrives in a logical order which results in a quicker reconstruction of the data
+enables two uses to hold a call without delay in speech

-bandwidth is wasted during periods of time where no data is sent
-the devices must transfer and receive data at the same rate
-since switches are used, electrical interference is produced which can corrupt or lose data

93
Q

What is packet switching?

A

a method of communicating packets of data across a network
- a packet is just a section of the data
- packets aren’t limited to a single route

94
Q

What are some +/- of packet switching? (3, 1)

A

+there are multiple methods to ensure data arrives
+there is more than one method of getting to the other devices, so if one path breaks you can use another
+you can transfer packets over very large networks to allow communication globally

-time is spent deconstructing and reconstructing the data packets

95
Q

What are data packets?

A

-segments of data
-contain various pieces of information

96
Q

What are topologies?

A

arrangement of elements in a computer network

97
Q

What are the two types of topologies? What do they represent?

A

logical: the way in data flows around a network
physical: the physical layout of the network

98
Q

Name the three topologies

A

-bus
-star
-mesh

99
Q

Draw diagrams showing the three topologies

A

bus topology: data:image/png;base64,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

star topology: https://circuitglobe.com/wp-content/uploads/2019/06/star-topology.jpg

mesh topology: data:image/png;base64,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

100
Q

What does a bus topology do?

A

all the terminals (devices) are connected to a backbone cable

101
Q

What are some +/- when using the bus topology? (1, 3)

A

+cheaper to set up, doesn’t require any
additional hardware

-if backbone cable fails, the entire network
gets disconnected
-as traffic increases, performance
decreases
-all computers can see the data
transmission

102
Q

What does a star topology do?

A

uses a central node (switch/computer) to direct the flow of data,
MAC (Media Access Control) addresses identify each device

103
Q

What are some +/- when using the star topology? (5, 2)

A

+performance is consistent even if network
is being heavily used
+if one cable fails, only that station is
affected
+transmits data faster, so it gives better
performance than bus topology
+ easy to add new stations
+no data collisions

-expensive due to switch and cabling
-if the central switch fails, the rest of the
network fails

104
Q

What does a mesh topology do?

A

where every node is connected to every other node

105
Q

What are some +/- when using the mesh topology? (4, 2)

A

+no cabling cost
+as nodes increase, the reliability and speed of network becomes better
+nodes automatically get incorporated
+it’s faster since nodes don’t go through a central switch

-you have to purchase devices with
wireless capabilities
-maintaining the network is difficult

106
Q

What are firewalls? How do they work?

A

software/devices designed to prevent unauthorised access to a network
- consist of two network interface cards (NICs), in-between the user and their internet connection
- pass packets between these two NICs and compares them against a set of rules (packet filters) set by the firewall software
- perform packet filtering / static filtering
- limit network access in accordance with administrator rules and
policies

107
Q

What is a proxy server?

A

an intermediary, collecting and sending the data on behalf of the user

108
Q

What do proxy servers do?

A

-protect the privacy of the user who remains anonymous
-cache frequently used website data making it faster to load
-reduce the web traffic
- prevent access to sensitive or irrelevant information at work or at school

109
Q

What are the different types of network hardware? (8)

A

-modem
-router
-cable
-NICs
-WAP
-hub
-switch
-gateways

110
Q

What do NICs do?

A

network interface cards
-assigns a unique MAC address to each device

111
Q

What do switches do?

A

directs flow of data across a network
-connects everything

112
Q

What do WAPs do?

A

wireless access point
-allows devices to connect to a network wirelessly

113
Q

What do routers do?

A

used to connect two or more networks together

114
Q

What do gateways do?

A

used when protocols aren’t the same between networks
- translates protocols so that both networks have the same

115
Q

What are client-server networks?

A

terminals known as clients, connected to a server
- a server is just a powerful central computer, holds all important info, has extra processing power and, clients can request to use it

116
Q

What are +/- of using client-server networks? (3, 2)

A

+more secure
+central backups eliminate the need for client backups
+sharing data between resources and clients

-expensive to set up
-staff with training are required to maintain the server

117
Q

What are peer-to-peer networks?

A

computers connected to each other so that they can share files

118
Q

What are some positives when using peer-to-peer networks?

A

+inexpensive to set up
+allows users to share resources
+easy to maintain

119
Q

What is HTML used for?

A

language that web pages are written in
-allows a browser to interpret and render a webpage for the viewer by describing the structure and order of the webpage

120
Q

What are all the HTML tags needed to know? (13)

A

<html>
<body>
<link></link>
<head>
<title>
<h1> <h2> <h3>
<p>
<img></img>
<a>
<ol>
<ul>
<li>
<div>

to close a tag: </tagname>
</div></li></ul></ol></a></p></h3></h2></h1></title></head></body></html>

121
Q

what does the <p> tag do?

A

creates a paragraph

122
Q

What does the <img></img> tag do?

A

self closing image with parameters

123
Q

What does the <a> tag do?</a>

A

anchor tag defining a hyperlink with location perameters

124
Q

What does the <link></link> tag do?

A

used to link to a css sylesheet

125
Q

What does the <div> tag do?

A

creates a division of a page into separate areas each which can be referred to uniquely by name

126
Q

What is CSS?

A

a language used to describe the style of a webpage

127
Q

How does CSS become implemented within a webpage?

A

-can be applied to whole tags e.g. <h1> <p> <div>
-internal/embedded CSS placed inside they style tages and entered directly within a HTML document
-external CSS is placed inside an external stylesheet- a link is created

128
Q

What is javascript?

A

a language which adds interactivity to websites

129
Q

What can JavaScript do?

A

-inputs data on the clients’ computer e.g forms, message pop-ups

130
Q

What is a search engine?

A

a program that searches through a database of internet addresses looking for resources based on a criteria set by the client

131
Q

What are web crawlers?

A

collect information by searching the internet web looking for linked sites
-collect keywords and phrases from the web page
-collect meta data from websites (the information specified by the website owner)

132
Q

What is the pagerank algorithm?

A

-ranks each web page
- higher rankings will make web pages show up first on the search engine

133
Q

What are factors which determine the page rank of a web page?

A

-how many incoming links it has from other web pages
-the page rank of the web pages that link to it

134
Q

What is server side processing?

A

when a client sends data to a server for it to be processed

135
Q

What are the server side scripting languages?

A

-SQL
-PHP

136
Q

Why is server side processing beneficial?

A

-doesn’t require large plugins
-can perform large calculations much faster than clients
-not browser dependant
-more secure

137
Q

What is client side processing?

A

when a client processes the data on its local device
-all info processed on the clients computer

138
Q

What language does client side processing use?

A

javascript

139
Q

Why is client side processing beneficial?

A

-webpages can immediately respond to user actions
-execute quickly
-gives developers more control over the behaviour and look of the website

OCR A-level Computer Science (8 decks)

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