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Computer science A Level OCR > 1.3 Exchanging Data > Flashcards

1.3 Exchanging Data Flashcards

Compression, Encryption and Hashing Databases Networks Web Technologies

1
Q

What name is given to public and private keys used in asymmetric encryption?

A
  • Key pair
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2
Q

Name the two categories of compression

A
  • Lossy

- Lossless

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3
Q

In which type of compression is the quality of a file not degraded?

A
  • Lossless
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4
Q

What is the purpose of encryption?

A
  • To keep data secure during transmission
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5
Q

Name one type lossless compression

A
  • Run length encoding

- Dictionary encoding

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6
Q

In which form of encryption do the sender and receiver share the same private key?

A
  • Symmetric encryption
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7
Q

How many keys are used in asymmetric encryption?

A
  • Two (one public and one private)
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8
Q

If person A wants to send a message to person B using asymmetric encryption, which key should they use to encrypt the message?

1) A’s public key
2) A’s private key
3) B’s public key
4) B’s private key

A

3) B’s public key

A message encrypted with B’s public key can only be decrypted with B’s private key, which only B has access to.

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9
Q

What is said to have occured when two keys map to the same hash?

A

A collision

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10
Q

In which kind of lossless compression are repeated characters replaced by one occurrence and the number of times to repeat the character?

A
  • Run length encoding
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11
Q

What name is given to the process of turning an input into a fixed size value?

A
  • Hashing
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12
Q

Which data structure uses hashing to store information with constant lookup time?

A
  • Hash table
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13
Q

What is meant by compression?

A
  • The process of reducing the space required to store a file
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14
Q

Name two properties that a hashing algorithm should have.

A
  • Low chance of collision
  • Quick to calculate
  • Output smaller than input
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15
Q

What is a relational database?

A
  • A database which recognises the difference between entities and uses different tables for each entity.
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16
Q

What is an entity?

A
  • An item of interest about which information is stored.
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17
Q

What is a flat file?

A
  • A database that consists of a single file, usually about one entity.
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18
Q

What is a primary key?

A
  • A unique identifier for each record in a table.
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19
Q

What is a foreign key?

A
  • The attribute which links two tables together
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20
Q

What is a secondary key?

A
  • An index other than the primary key used to search and sort through the database with more convenience and speed.
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21
Q

What does capturing data mean?

A
  • The process of getting the information that will be stored in the database.
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22
Q

What method do banks use to capture data from cheques?

A
  • Magnetic Ink Character Recognition (MICR) is used for all of the details apart from the amount which must be entered manually.
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23
Q

What does selecting data mean?

A
  • Selecting data is the process of removing excess information to extract only the data you require
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24
Q

What does managing the data mean?

A
  • To manipulate the information collected in any type of way such as through sorting through it or selecting certain parts using SQL.
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25
Q

what is the most common language used to manipulate data in databases?

A
  • SQL (Structured Query Language)
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26
Q

What is a network?

A
  • Two or more computers connected together that transmit data
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27
Q

What is physical topology?

A
  • Physical topology is the physical layout of the network.
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28
Q

What is logical topology?

A
  • The topology that describes the flow of data through a network
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29
Q

What is bus topology?

A
  • Topology in which all terminals are connected to a backbone cable
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30
Q

Name an advantage of the bus topology

A
  • Cheaper to set up

- Doesn’t require any additional hardware

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31
Q

Give a disadvantage of the bus topology

A
  • If backbone cable fails, entire network gets disconnected
  • As traffic increases, performance decreases
  • All computers can see data transmission
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32
Q

What is star topology?

A
  • A network which uses a central node to direct the flow data, each terminal is connected to the central node.
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33
Q

Give 2 advantages of Star topology.

A
  • Performance is consistent with heavy network usage
  • If one cable fails only that station is affected.
  • Transmits data faster, so it given performance
  • It’s not difficult to add new stations
  • No data collisions
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34
Q

Give a disadvantage of star topology

A
  • Expensive due to switch and cabling

- If the central switch fails then the rest of the network fails

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35
Q

What is a mesh topology?

A
  • A topology in which every node is connected to every other, most commonly found with wireless technology
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36
Q

Give 2 advantages of mesh topology

A
  • No cabling cost
  • As number of nodes increase, reliability and speed increases
  • New nodes automatically get incorporated
  • Faster since data doesn’t travel through a central switch
37
Q

Give a disadvantage of mech topology

A
  • Need to purchase devices with wireless capabilities

- Maintaining the network is difficult

38
Q

What are protocols?

A

Sets of rules defining how two devices communicate with each other.

39
Q

Why are protocols standard?

A
  • Protocols are standard so devices from different manufacturers don’t have problems communicating
40
Q

Describe the structure of the Internet

A
  • The Internet is a global network of interconnected networks
41
Q

What does TCP stand for?

A
  • Transmission Control Protocol
42
Q

What does IP stand for?

A

Internet Protocol

43
Q

What is the function of the application layer during data transmission?

A

The Application Layer specifies what protocols need to be used to relate the application to what it’s being used for.

44
Q

What is the role of the transport layer during data transmission?

A
  • Establishes an end-to-end connection between the source and recipient computers. It also splits up the data into packets.
45
Q

What is the role of the network layer during data transmission?

A
  • Adds the source and destination IP address.
46
Q

What does the application layer do when it receives data?

A
  • Presents data in the form it was sent
47
Q

What does the transport layer do when it receives the data?

A
  • Removes the port number and reassembles the packets
48
Q

What does the network layer do when it receives the data?

A
  • Removes the IP address
49
Q

What does the link layer do when it receives the data?

A
  • Removes the MAC addresses
50
Q

What is a Local Area Network?

A
  • A network spread over a small geographical area/ positioned on a single site
51
Q

What is a Wide Area Network?

A

A network spread over a large geographical area, usually requiring extra hardware.

52
Q

What does DNS stand for?

A
  • Domain Name system
53
Q

What is DNS?

A
  • The name given to the method of naming internet resources. (.com, .uk etc)
54
Q

What is circuit switching?

A

The process of creating a direct link between two devices and transferring data the entire duration of the link.

55
Q

What is a requirement of circuit switching?

A
  • The transfer and download rates must be identical on both devices.
56
Q

What is packet switching?

A
  • A method of communicating packets of data across a network
57
Q

Give an advantage of packet switching

A
  • Multiple methods to ensure data arrives correctly
  • Multiple methods to arrive to destination, if one breaks you can always go through another route
  • Transfer packets over a very large network
58
Q

Give a disadvantage of packet switching

A
  • Time is spent deconstructing and reconstructing the packers
59
Q

Give an advantage of circuit switching

A
  • Data arrives in logical order which results in a quicker reconstruction of data
  • Enables two users to hold a call without any delay in speech
60
Q

Give 2 disadvantages of circuit switching

A
  • Bandwidth is wasted during periods when no data is sent
  • Devices must transfer and download at the same rate
  • Switches introduce electrical interference which can corrupt or destroy data
61
Q

What does the header of a data packet contain?

A
  • The sender and recipient IP addresses
  • Protocols being used
  • Order of the packets
  • The time to live / hop limit
62
Q

What does the packet payload contain?

A

The raw data

63
Q

What does the packet trailer contain?

A
  • The checksum or cyclic redundancy check
64
Q

What is client-server networking?

A
  • A relationship between terminals (computers) and a single server which allows them to communicate, and share resources.
65
Q

Give an advantage of client-server networking

A
  • Increase security
  • Central single backups
  • Data and resources can be shared
66
Q

Give a disadvantage of client-server networking

A
  • Expensive to set up

- Trained staff are required to maintain the network

67
Q

What is peer-to-peer Networking?

A
  • A networking where the terminals are all connected to each other to share resources.
68
Q

Give an advantage of peer-to-peer networks

A
  • Cheaper to set up
  • Easy to share resources
  • Easy to maintain
69
Q

Give an disadvantage of peer-to-peer networks

A
  • Peer-to-peer networks can be used to contribute towards piracy
  • Each computer has to be backed up independently
70
Q

What is HTML?

A
  • HTML is the language/script the web pages are written in
71
Q

What does HTML do?

A
  • HTML allows a browser to interpret and render a webpage
72
Q

What is a tag in HTML?

A
  • HTML code is made up of tags, tags are the names given to values written within angle brackets i.e. <h1></h1>
73
Q

What is an identifier selector?

A

An identifier selector is a value that hollows a hashtag

74
Q

What is a class selector?

A
  • A class selector is a value that follows a full stop
75
Q

What is CSS?

A
  • CSS is a script/language like HTML except it’s used to describe the style of a webpage
76
Q

What are the names of the two methods of applying CSS?

A
  • Internal/embedded CSS

- External CSS

77
Q

Where do you write internal CSS?

A
  • It’s placed inside the style tags and is entered directly within the HTML document
78
Q

Where do you write external CSS?

A
  • You write it in a separate document
79
Q

How do you use external CSS in your HTML code?

A
  • You use the tag
80
Q

What is JavaScript?

A

JavaScript is a language used on webpages to add interactivity

81
Q

Is JavaScript interpreted or compiled?

A
  • Interpreted
82
Q

What is a search engine?

A
  • A search engine is a program that searches through a database of internet addresses looking for a resource based on a criteria set by the client/user.
83
Q

What software does a search engine use?

A
  • Web Crawlers
84
Q

What does a web crawler do?

A

Travels across the internet collecting keywords and phrases from a web page and adding it to an index of web resources.

85
Q

What is the page rank algorithm?

A
  • The algorithm used to determine the order used when showing web results for a search engine query
86
Q

What factors determine a page rank?

A
  • The number of incoming links it has from other web pages

- The page rank of the web pages that link to it

87
Q

What is server side processing?

A
  • Server side processing is when a client sends information to a server for processing
88
Q

What is client side processing?

A
  • Client side processing is when information is processed on a local device for processing

Computer science A Level OCR (5 decks)

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