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Computer Science A-Level > Section 6: Communication: Technology and Consequences > Flashcards

Section 6: Communication: Technology and Consequences Flashcards

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1
Q

Chapter 31:
What is Data Communication?
Give examples.

A

Sending and receiving data from one computer or device to another.

Examples include E-Mail, Phone Calls, Between a CPU and its components.

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2
Q

Chapter 31:

What are the two main types of data communication?

A

Serial.

Parallel.

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3
Q

Chapter 31:
What are the 7 base binary units?
Where are they used?

A

Bit - 1 or 0.
Make up all the others.

Nibble - 4 bits.
Not used as a quantity, but 1 Hexadecimal number is a Nibble in Binary.

Byte - 8 bits.
Used in data storage

Kibibytes - 1024 bytes.
Used in data storage, like bytes, but represent higher values.

Kilobyte - 1000 bytes.
Used in displays of data storage. bibytes are what the computer uses because computers use base 2, but bytes are easier to understand for humans.

Kibibit - 1024 bits.
Used in data transmission.

Kilobit - 1000 bits.
Used in displays of data transmission. bibits are what the computers use because computers use base 2, but bits are easier to understand for humans.

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4
Q

Chapter 31:

What is Serial transmission?

A

Where data is sent one bit at a time.

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5
Q

Chapter 31:

What is Parallel transmission?

A

Where data is sent simultaneously over a number of parallel wires.

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6
Q

Chapter 31:

Over long distances, Parallel transmission becomes less viable. Why?

A

Parallel transmissions need to be in sync with each other.
Over long distances, the signal can start to SKEW, which means that the signals get out of sync, due to the slight differences in the wires.

Crosstalking also becomes a problem with Parallel transmissions. This is where Signals can “jump” between wires. This causes corruption of data.

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7
Q

Chapter 31:

What are the advantages of using Serial transmission over Parallel?

A 
Reduction in size and complexity.
Lower costs.
No chance of crosstalking.
Reliable over greater distances.
Signal Frequency can be higher, possibly resulting in a higher net data transfer rate.
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8
Q

Chapter 31:

What is the difference between Bit Rate and Baud Rate?

A

Bit Rate - The speed at which data is transmitted serially.

Baud Rate - The rate at which the signal changes.

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9
Q

Chapter 31:
An analogue signal carries 4 bits in each signal unit. If 1000 signal units are sent per second, find the Baud Rate, and the Bit Rate.

A

Baud Rate = 1000 bauds per second (baud/s).

Bit Rate = 4 * 1000 = 4000 bits per second (bps).

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10
Q

Chapter 31:

What is Bandwidth?

A

The range of frequencies that a transmission medium can carry.
The larger the range, the greater the amount of data that can be transmitted in a fixed amount of time.

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11
Q

Chapter 31:

What is latency?

A

The time it takes between the moment the transmission of the first byte or packet of a communication starts, to when it is received.

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12
Q

Chapter 31:

What is Parity?

A

Computers use either odd or even parity.

In an even parity machine, the total number of ‘on’ bits in every byte will be even. Every byte has a parity bit that is set to meet this requirement.

When the bytes are received, parity is checked. If the parity is different, an error has occurred.

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13
Q

Chapter 31:

What position does the parity bit take?

A

Most Significant Bit (MSB).

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14
Q

Chapter 31:

What is Synchronous Transmission?

A

Data is transfered at regular intervals that are timed by a clocking signal, allowing for a constant and reliable transmission.

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15
Q

What is Asynchronous Transmission?

A

One byte at a time is sent with each character being preceded by a start bit and followed by a stop bit.

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16
Q

Chapter 31:

When would you use Synchronous Transmission?

A

When data is time-sensitive, such as real-time video or voice.

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17
Q

Chapter 31:

When would you use Asynchronous Transmission?

A

When components are unable to share a clock signal.

When small amounts of data need to be transmitted.

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18
Q

Chapter 31:

What is Protocol?

A

A set of rules relating to communication between devices.

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19
Q

Chapter 31:

Why are Protocols used?

A

So that devices from different manufacturers can interact with each other.

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20
Q

Chapter 33:

What is the idea of Client-Server Networking?

A

One or more computers connect to a central “Server”.

The Server stores files accessible to any device in the network, and can redirect signals between devices.

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21
Q

Chapter 33:
Some Networks use multiple Servers.
Give some examples of specific servers used.

A 
File Server.
Print Server.
Web Server.
Mail Server.
Database Server.
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22
Q

Chapter 33:

What are some Advantages of using a Client-Server Network?

A

Security is better because Files are stored Centrally.

Backups are done centrally so there is no need for individuals to backup their own data.

Data and other resources can be shared.

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23
Q

Chapter 33:

What are some Disadvantages of using a Client-Server Network?

A

It’s expensive to install and manage.

Professional IT staff are needed to maintain the servers and run the network.

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24
Q

Chapter 33:

What is the idea of Peer-to-Peer Networking?

A

Devices are connected to each other directly, rather than through a server.

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25
Q

Chapter 33:

What are some Advantages of using a Peer-to-Peer Network?

A

It’s cheap to setup.

It is easy to maintain.

It enables users to share resources such as a printer or router.

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26
Q

Chapter 33:

What are some Disadvantages of using a Peer-to-Peer Network?

A

Having many devices, all Peer-to-Peer with each other, becomes complex.

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27
Q

Chapter 33:

*What illegal music streaming software was created in January 1999?

A

Napster.

Software that distributed parts of MP3 files to users so that every user could listen to music for free (pirating), and so that the developers could get away with it because they aren’t responsible for what is on their users computers.

In 2000 they lost a case and were sued into bankruptcy.

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28
Q

Chapter 33:

*Who created Napster?

A 
Shawn Fanning   ( 19-year-old )
Sean Parker        ( 20-year-old )
                             ( In 1999 )
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29
Q

Chapter 33:

*What was the Movie version of illegal music streaming platform Napster?

A

Popcorn Time.

Developed in 2014.

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30
Q

Chapter 34:

What is Wi-Fi?

A

Wi-Fi is a local area wireless technology that allows you to connect devices to a network resource or to the internet via a Wireless Network Access Point (WAP).

31
Q

Chapter 34:

*What is the Wi-Fi Alliance?

A

Formed in 1999, was a group of several hundred companies around the world, that enforces the use of standards for device connectivity and network connections.

32
Q

Chapter 34:

What are the two components needed in Wi-Fi?

A

Station.

Router.

33
Q

Chapter 34:

What is a Station(Networking)?

A

A device that can connect to Wi-Fi.

A Device + A Wireless Network Adaptor.

34
Q

Chapter 34:

What are the security protocols used in Wireless Networking?

A

Wi-Fi Protected Access (WPA)
Wi-Fi Protected Access II (WPA2)

WPA replaced WPA.

35
Q

Chapter 34:

How does WPA2 Encryption work?

A

Wi-Fi Protected Access II uses a new 128-bit key for each packet that is sent.

36
Q

Chapter 34:
What is SSID?
Why is it used?

A

Service Set Identification.

The informal name of a specific Local Network. For example, SKY36G3D.

Used so that visitors can easily identify Networks. A device may be in range of several Networks, SSID is a way to tell them apart.

37
Q

Chapter 34:

How large is a standard SSID?

A

32 bits / 8 hexits (usually hexadecimal).

38
Q

Chapter 34:

What is MAC Address?

A

Media Access Control Address.
Unique for every single device.
Used to identify / filter devices.

39
Q

Chapter 34:

What is MAC Address Whitelisting?

A

A set of MAC Addresses will be stored.

When a device attempts to join the Network, the device’s MAC Address is checked against the list.

If the device’s MAC Address is in the set, the device will be allowed access to the Network.

40
Q

Chapter 34:

What is CSMA/CA?

A

Carrier Sense Multiple Access / Collision Avoidance.

Protocol that attempts to avoid collisions occurring on a data channel.

41
Q

Chapter 34:

How does CSMA/CA work?

A

Carrier Sense Multiple Access / Collision Avoidance.

Before Transmitting, a node listens to determine whether another node is transmitting. If a signal is detected, it waits for a random amount of time before trying again.

Data will be transmitted when there is a free space.

42
Q

Chapter 34:

What is the problem with CSMA/CA?

A

If two nodes detect a free space to transmit at the exact same time, there will be a collision.

“Hidden nodes” is also a problem. This is where two nodes are both in range of the WAP, but out of range of each other. This means that they can’t detect each other’s signals, so one might send data while the other is already doing so.

43
Q

Chapter 34:

What is CSMA/CA with RTS/CTS?

A

When there is a free space for transmission, nodes will send a Request To Send (RTS) Signal.

The WAP sends a Clear To Send (CTS) Signal back when the channel is idle.

44
Q

Chapter 35:

Who was Edward Snowden?

A

Whistleblower that used to work for the CIA.
He exposed the US Government’s Data surveillance.

Snowden revealed that the literal aim of the US Government was to collect, store, monitor, and analyse metadata (number called, date, time, duration of call) about everyone in the world.

45
Q

Chapter 35:

Who were the Journalists that worked with Edward Snowden?

A

Glenn Greenwald.
Laura Poitras.

They met each other in Marriott Hotel - New York to discuss an initial contact with Snowden.

46
Q

Chapter 35:
In 2007, there was a major Cyber-attack.
What happened?

A

At the end of World War 2, a memorial was built in Estonia called The Bronze Soldier of Tallinn, by the USSR.

After the USSR collapsed in 1991, Estonia was recognised as its own country.

At this point, The Bronze Soldier was recognised as patriotic for Russians, and Estonian Russians, but as oppression by Estonians.

In 2007, there were plans to relocate the memorial to a less central part of Estonia.

This was badly received by Estonian Russians, and riots broke out, that had to be contained by police.

Starting on the 27th April 2007, Estonian Servers in Banking, Parliament, Ministries, Newspapers, Businesses and more were targeted and flooded with hateful messages. This managed to shut down Estonian lifestyle, as Estonia had been competing in international technological progression.

The attack persisted for about 3 weeks.

47
Q

Chapter 35:
In 2014, Sony Pictures was attacked.
What happened?

A

Sony’s film, The Interview, is an action comedy in which two journalists are instructed to assassinate North Korean leader 김정은 (Kim Jong-Un).

The North Korean government responded with threats for if the film was released.

In November, Sony Pictures’ computers were hacked by the “Guardians of Peace”, a group that the FBI believes was linked to the North Korean Government.

Several other forthcoming films and other sensitive information was also leaked, and terrorist threats were directed towards cinemas if they showed the film.

48
Q

Chapter 35:

What is Google Street View?

A

Integrated into Google Earth in 2008, Google Street View allows users to navigate through a virtual version of most streets.
Images are taken with a 360 degree camera in different spots along the roads, so that users can jump ahead to different spots, and look all around.

49
Q

Chapter 35:

What are the advantages of Google Street View?

A

It allows for convenient satisfaction of planning and curiosity.

Users can explore the area around a hotel, a friend’s house, or a new house that they’re interested in buying without physically being there.

50
Q

Chapter 35:

What are the issues with Google Street View?

A

Invasion of Privacy:
Anyone with access to the internet has anonymous access to go exploring in places that residents may not like. While Google Street View doesn’t invade private property, it does go as close as publicly allowed.
Citizens can also be seen around at the time that the images were taken of the street. Attempts are made to hide the identity of these people, by blurring faces, but people can sometimes still be identified.

Untrustworthy Users:
Google Street View is available to everyone. This includes groups or individuals that wish to steal from, or attack a building, or set of buildings.

51
Q

Chapter 36:

How did the internet start?

A

With the Advanced Research Project Agency Network (ARPANET) (1966) .
This was the first Wide-Area Packet-Switching Network, and one of the first to use TCP/IP.

52
Q

Chapter 36:

  • Who created the TCP/IP?
  • When?
A

Bob Kahn and Vint Cerf.

1974.

53
Q

Chapter 36:

What does TCP/IP stand for?

A

Transmission Control Protocol / Internet Protocol.

54
Q

Chapter 36:

*Who created the World Wide Web?

A

Tim Berners-Lee.

55
Q

Chapter 36:

Why is Amazon significant?

A

Starting as an online bookstore in 1994, Amazon is now one of the most diverse websites for online shopping, now selling Books, DVDs, furniture, electronics and much more.

Amazon now accounts for 65% of online purchases of books. Each $10,000,000 made from sales in a physical bookstore, 47 people would be hired. For the same amount, Amazon hires 14 people.

56
Q

Chapter 36:

  • Who created Google?
  • When?
A

Larry Page and Sergey Brin.

1996.

57
Q

Chapter 36:

Why is Google so significant?

A

When Google was released, other search engines already existed. Examples of which are Yahoo and Altavista.

Google is significant because the ‘Page Rank’ Algorithm that it used creates links and recognised patterns. This makes results more accurate, but it also means that Google learns about its users.

58
Q

Chapter 36:

What does computerisation mean for businesses?

A

Businesses are gaining more access to automated machines. This requires a large investment, but can cut down overall costs, as less workers are needed to perform that jobs. Computers can also execute many tasks at much greater speed and precision than humans, as well as being able to run constantly.

59
Q

Chapter 36:

What does computerisation mean for jobs?

A

As jobs become automated by computers, people will start to be replaced. This pushes people into smaller organisations that can’t afford expensive machinery, and can’t afford to pay workers high wages.

Some fields will start to excel, however, Computer Science and Engineering jobs will increase, as the machines will have to be constructed and programmed in order to take over jobs.

Computerisation is at a heavy risk of opening a gaping divide between Businesses and Engineers, against the working populations.

60
Q

Chapter 36:

What affect is User-Generated content having on the younger generation?

A

According to Andrew Keen in his book “The Cult of the Amateur”, Digital Narcissism is becoming more common in youth.

Keen also addresses Anonymity, saying that we act differently when we cannot be discovered.
This idea is backed up by studies; a famous example is the second episode in the series called The Experiment, by Derren Brown.
In the episode, a fake game show is created where the audience will chose several good/bad options for their protagonist Chris, a real person that was given one of the worst days of his life because the audience (who were all given a face cover to wear) chose the bad option every time. Chris was falsely accused of sexual assault, not paying at a bar, shop theft and more.

61
Q

Chapter 36:

In what way can Algorithms in the digital age be problematic?

A

Algorithms are the instructions that all machines work on.

When designing algorithms it is important to consider every possible outcome of the machine that uses it.
With examples such as the internet, it is impossible to individually check just a fraction of all possible outcomes, due to so much variability.
As a result of this, Algorithms can be volatile when applied to the real world, as one input could mean significant consequences. Furthermore, when you have learning algorithms, cumulative data can distort the result.

62
Q

Chapter 36:

What is the Internet of Things?

A

The connection of objects to the internet.

Often refers to objects that are typically inert (inactive) such as:
A Fridge - Use an algorithm to determine what needs to be replaced.
A Door - Use an algorithm to determine who to let in.

63
Q

Chapter 36:
When considering Driverless cars, there are 3 main events to consider before writing an Algorithm.
What are these events?

A

The car can stay on track and hit several pedestrians, or swerve into one. (The Trolley Problem).

The car can stay on track and hit one pedestrian, or swerve and harm the passenger/s.

The car can stay on track and hit many pedestrians, or swerve and harm the passenger/s.

64
Q

Chapter 36:

What is another major point when considering Driverless cars’ Algorithms?

A

Age of potential victims:
Children have a longer life ahead of them, and often have less say on being involved in the accident. So should Children be prioritised for saving, over adults?
Pensioners have a shorter life ahead of them, but are also more fragile, and less mobile. So should Pensioners be prioritised for saving, over more mobile younger adults?

Severity of the choice:
The Algorithm should also consider the severity of the choices. If the option is killing one person against non-lethally harm multiple people, it is likely better to harm multiple, rather than kill one person.

65
Q

Chapter 36:

What are some difficulties for legislation of computing laws?

A

The internet operates internationally, but different countries have different laws.

New applications are being invented constantly, so legislation needs to keep up.

66
Q

Chapter 32:

Describe the physical bus topology.

A

All devices are connected to a single cable. The ends of the cable are connected to terminators.

67
Q

Chapter 32:

What are the advantages of the bus topology?

A

Inexpensive to install, as it requires less cable.

68
Q

Chapter 32:

What are the disadvantages of the bus topology?

A

If the backbone cable fails, the network shuts down completely.

Performance degrades with heavy traffic.

Collisions with high traffic.

Low security - all computers can see all transmissions.

69
Q

Chapter 32:

Describe the physical star topology.

A

All devices connect to a central node (often router). Traffic is passed through this node directly to the destination.

70
Q

Chapter 32:

What are the advantages of the star topology?

A

If one cable fails, the rest of the network remains active.

Consistent performance, even when traffic is high.

No collisions.

System is more secure, as the transfers are direct.

Easy to add new stations without disrupting the network.

71
Q

Chapter 32:

What are the disadvantages of the star topology?

A

May be expensive to install because more cable is needed and so is a switch to connect the devices.

If the central switch goes down, the whole network stops.

72
Q

Chapter 32:

What is the difference between physical and logical topology?

A

Physical topology is how the devices are physically connected.

Logical topology is how the system operates.

73
Q

Chapter 32:

Where is the MAC Address located?

A

The Media Access Control address is located in the Network Interface Card (NIC).

Computer Science A-Level (12 decks)

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