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comp sci 1 > Exchanging Data 1.3 > Flashcards

Exchanging Data 1.3 Flashcards

1
Q

Name the two categories of compression

A

Lossy and lossless

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2
Q

Explain lossless compression

A

lossless compression reduces the size of a file without losing any information

The original file can be recovered from the compressed
version

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3
Q

Explain lossy compression

A

lossy compression reduces the size of a file while also removing some of its information

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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 types of lossless compression

A
  1. Run Length Encoding
  2. Dictionary Encoding
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6
Q

Explain Run Length Encoding (RLE)

A

RLE is a method of lossless compression in which repeated values are removed and replaced with one occurrence of the data followed by the number of times it should be repeated

For example, the string AAAAAABBBBBCCC could be represented as A6B5C3 since ‘A’ is repeated 6 times etc..

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7
Q

When would and wouldnt you use run length encoding?

A

You would use run length encoding if there are many consecutive values. if there arent many it would not be useful

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8
Q

Explain Dictionary Encoding

A

Frequently occurring pieces of data are replaced with an index and compressed data is stored in a dictionary

The original data can then be restored using the dictionary.

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9
Q

When would dictionary encoding be used?

A

passages with repeated phrases

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10
Q

What is symmetric encryption?

A

Both the sender and receiver share the same private, This key is used for both
encrypting and decrypting data

If the key is intercepted during the key
exchange then any communications sent can be intercepted and decrypted using the key.

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11
Q

What is asymmetric encryption?

A

Both parties have a public and private key, where the public key is used for encryption and the private key is used for decryption

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12
Q

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

A

Person B’s public key

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

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13
Q

What is it meant by compression?

A

Compression is the process of reducing the space requires to store a file

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14
Q

What is Hashing?

A

A technique used to store and retreive data in a table by using a unique key. it is used ti speed up searches and comparisions

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15
Q

Name two properties that a hashing algorithm should have

A
  1. Low chance of collision
  2. Quick to calculate
  3. Output smaller than the input
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16
Q

What is a Relational database?

A

a relational database is a type of database that stores data in tables, which are related through common fields

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17
Q

What is an entity?

A

An item of interest about which information is stored

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18
Q

what is a flat file?

A

A database that consists of a single file usually about one entity

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19
Q

What is a primary key?

A

A unique identifier for each record in a table

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20
Q

What is a foreign key?

A

The attribute which links two tables together

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21
Q

What is a secondary key and what is it for?

A

A key that is indexed to allow for faster searching

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22
Q

What is normalization?

A

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

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23
Q

What does normalization try to accomplish?

A
  1. Records can be added and removed easily
  2. Complex queries can be carried out
  3. No redundancy (unnecessary duplicates)
  4. consistent data throughout linked tables
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24
Q

What is an index?

A

An index is a data structure used to look up and access data in a database quickly

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25
Q

What are the requirements to be in First Normal Form (1NF)?

A

It does not have any repeating attributes.
All the attributes must be atomic (a single attribute cannot more than one data)

e.g. a cell shouldn’t have first name and surname

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26
Q

What are the requirements to be in second normal form (2NF)?

A
  1. The database is in 1NF
  2. There are no partial dependencies (no composite keys)
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27
Q

What are the requirements to be in third normal form (3NF)?

A
  1. The database is in 2NF
  2. There are no non-key dependencies

This can be defined as saying
- ‘All attributes are dependent on the key, the whole key, and nothing but the key’

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28
Q

What does SQL stand for?

A

Structured Query Language

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29
Q

What is SQL?

A

A declarative language used to manipulate databases

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30
Q

What is referential integrity?

A

Referential integrity is the process of ensuring consistency, as it makes sure that information is not removed if it is required elsewhere in a linked database

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31
Q

What is a transaction defined as?

A

A transaction is a single operation executed on data

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32
Q

What does ACID stand for

A
  1. Atomicity
  2. Consistency
  3. Isolation
  4. Durability
33
Q

What does atomicity (in ACID) mean?

A

A transaction will be processed completely or not at all

34
Q

What does consistency (in ACID) mean?

A

A transaction must maintain referential integrity rules between linked tables

35
Q

What does Isolation (in ACID) mean?

A

will ensure that each transaction will be isolated and dealt with in a way that does not affect others

36
Q

What does durability (in ACID) mean?

A

Once a transaction has been executed it will remain, regardless of the circumstances

37
Q

What is record locking?

A

Record locking is the process of preventing many people to access a record

38
Q

What is the name of an issue that can happen as a result of record locking?

A

Deadlock

39
Q

What is redundancy

A

The process of creating more than one copy of data in a physically different location

40
Q

What is a network?

A

Two or more computers connected together to transmit data

41
Q

What is physical topology?

A

The physical layout of the network

42
Q

What is logical topology?

A

The topology that describes the flow of data through a network

43
Q

What is bus topology?

A

A topology where all terminals are connected to a backbone cable

44
Q

What is star topology?

A

A network where the central node directs the flow of data, each terminal is directly connected to the central node

45
Q

State two advantages of the bus topology

A
  1. Cheaper to setup
  2. Doesn’t require any additional hardware
46
Q

State two disadvantages of the bus topology

A
  1. As traffic increases, performance decreases
  2. All computers can see data transmissions
  3. If backbone cable fails, the entire network is disconnected
47
Q

State two disadvantages of the star topology

A
  1. If the central switch fails the rest of the network fails
  2. Expensive due to switch and cabling
48
Q

State two advantages of the star topology

A
  1. Transmits data faster, so the performance is better
  2. If one cable fails only that station is affected
  3. Not difficult to add new stations
  4. No data collisions
49
Q

What are protocols?

A

Protocols are a set of rules defining how two devices communicate with each other

50
Q

Why are protocols standard?

A

So that devices from different manufactures are able to communicate

51
Q

Describe the structure of the internet

A

The internet is a global network of interconnected networks

52
Q

What does TCP mean?

A

Transmission Control protocol

53
Q

What are the four layers of the TCP/IP protocol stack?

A
  1. Application layer
  2. Transport layer
  3. Internet layer
  4. Link Layer
54
Q

What is the function of the application layer?

A

The application layer specifies what protocols need to be used

55
Q

What is the role of the transport layer?

A
  1. Splits up data into packets
  2. Establishes end-to-end connection
56
Q

What is the role of the network layer?

A

Add the source and destination IP addresses

57
Q

What is the function of the link layer?

A

Adds the MAC addresses to the packets

58
Q

What is a Local Area Network?

A

A network spread over a small geographical area

59
Q

What is a Wide Area Network?

A

A network spread over a large geographical area

60
Q

What does DNS stand for?

A

Domain Name System

61
Q

What is DNS?

A

A system used to name and organise internet
resources. Domain names are much easier to remember than IP addresses, which is why they are
used to link to servers across the world

62
Q

What is the role of a DNS?

A

The role of the domain name system server (DNS
server) is to translate these domain names into IP addresses when we wish to access a
website.

63
Q

What is Circut switching?

A

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

64
Q

What is the requirement for circuit switching

A

The transfer and download rates must be identical on both devices

65
Q

What is packet switching?

A

A method of communicating packets of data across a network

66
Q

Give two advantages of packet switching

A
  1. Multiple methods ensure data arrives correctly
  2. Transfers packetes over a large network
  3. Mulitple methods to get to a destination, if one method breaks you can go another route
67
Q

Give an advantage of circuit switching

A
  1. Data arrives in order which means data will reconstruct faster
  2. Allows two people to call without any delay
68
Q

Give a disadvantage of circuit switching

A
  1. Devices must transfer and download at the same rate
  2. Bandwidth is wasted during periods when no data is sent
69
Q

What is the purpose of a firewall?

A

To prevent any unauthorized access to a network

70
Q

What is a firewall made up of?

A
  1. Firewall software
  2. Two network interface cards
71
Q

What is the function of a network interface card?

A

It connects a computer to a network

72
Q

What is the function of a router?

A

A router connects two networks together

73
Q

What is client-server networking?

A

A relationship between terminals(computers) and a single server, which allow them to communicate, and share resources.

74
Q

Give an advantage of client-server networking

A
  1. Increased security
  2. Data and resources can be shared
75
Q

Name a disadvantage of client-server networking

A
  1. Expensive to set up
  2. Trained staff are required to maintain the network
76
Q

What is peer-to-peer networking?

A

A network where all terminals are connected to each other to share resources

77
Q

Give two advantages of peer-to-peer networks

A
  1. Cheaper to setup
  2. Easy to share resources
  3. Easy to maintain
78
Q

Give two disadvantages of peer-to-peer networks

A
  1. Each computer needs to be backed up independently
  2. Files and resources are more difficult to share

comp sci 1 (7 decks)

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