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Higher Computer Science > Computer Systems > Flashcards

Computer Systems Flashcards

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1
Q

What are the two forms of representing text?

A
  • Extended ASCII
  • Unicode
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2
Q

How many bits does extended ASCII use?

A

8 bits

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3
Q

How many bits does unicode use?

A

16 bits

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4
Q

What is an advantage of extended ASCII?

A

Less storage requirements

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5
Q

What is a disadvantage of extended ASCII?

A

Can’t represent as many characters

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6
Q

What is an advantage of unicode?

A

Can represent more characters

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7
Q

What is a disadvantage of unicode?

A

Requires more storage

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8
Q

What is colour depth?

A

The number of bits per pixel, which determines how many colours can be represented

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9
Q

What is true colour?

A

A colour bit depth of 24 bits

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10
Q

What are the advantages of bitmap graphics?

3

A
  • Can edit down to individual pixel level
  • Adding extra detail does not increase file size
  • Can create photo realistic images
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11
Q

What are the disadvantages of bitmap graphics?

2

A
  • Very large file size for individual pixel storage
  • Resolution dependant, so pixelated when scaled larger
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12
Q

What are the advantages of vector graphics?

3

A
  • Small file size as only attributes are saved
  • Resolution independent, so doesn’t pixelate when scaled larger
  • Objects can be layered
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13
Q

What are the disadvantages of vector graphics?

2

A
  • Difficult to make realistic images with just objects
  • Adding extra objects increases file size
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14
Q

What happens if we increase the number of bits allocated to the mantissa?

A

Increases the precision of the number, but decreases the number of bits available for the exponent so the range of numbers is decreased

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15
Q

What happens if we increase the number of bits allocated to the exponent?

A

Increases the range of the number, but decreases the number of bits available for the mantissa so the precision of the number is decreased

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16
Q

What are the steps of the fetch execute cycle?

4

A
  1. The processor sets up the address bus with the required address
  2. The processor activated the read line on the control bus
  3. An instruction is fetched from the memory location using the data bus and stored in the instruction register
  4. The instruction in the instruction register is then interpreted by the decoder and carried out
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17
Q

What factors affect system performance

4

A
  • Number of cores (processors)
  • Width of data bus
  • Cache memory
  • Clock speed
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18
Q

How does the number of cores affect system performance?

2

A
  • The more cores a processor has, the more sets of instructions the processor can receive and process at the same time, which improves system performance
  • A dual core processor is not as fast as a single processor running at twice the speed as it is not always possible to share some tasks equally between the cores, which reduces efficiency
19
Q

How does the width of the data bus affect system performance?

A

By increasing the data bus from 32 wires to 64 wires, the computer can transfer twice as much information at one time which improves the system performance of the computer

20
Q

What is the data bus?

A

A set of parallel wires that connects the processor with memory and other hardware devices

21
Q

What is cache memory?

A

A small amount of fast accessible memory, usually with or close to the processor

22
Q

How does cache memory affect system performance?

A

The processor checks the cache for data or instructions before accessing the main memory, which is faster and can result in fewer accesses to slower main memory

23
Q

What is clock speed?

A

The electronic unit that synchronises related components by generating pulses at a constant rate

24
Q

How does the clock work?

A
  • Clock pulses are used to trigger components to take their next step,
  • The clock rate is the frequency at which the clock generates pulses
25
Q

How does clock speed affect system performance?

A

The higher clock rate, the faster the computer may complete a series of instructions

26
Q

How do heating systems have a good environmental impact?

2

A
  • Smart heating systems can be connected to wifi, so heating can be turned off using an app if you are away from home which reduces the amount of heat being wasted
  • Smart heating systems can also use activity sensors to learn temperature preferences, so only necessary heat is used
27
Q

How does smart traffic control have a good impact on the environment?

2

A
  • Uses a variety of information from cameras, sensors and traffic signals to try keep traffic moving, reducing the amount of harmful emissions
  • Cars with individual navigation systems use satellite information on traffic flow to guide drivers away from traffic congestion and on to more free flowing routes
28
Q

How do car management systems have a good impact on the environment?

A

Start-Stop systems automatically shut down the engine when the car is not moving, this reduces the amount of time the engine spends idling which reduces fuel consumption and emissions

29
Q

What is the act that makes unauthorised activities on computers illegal?

A

Computer Misuse Act 1990

30
Q

What offences can one be prosecuted for under the computer misuse act?

4

A
  • Unauthorised access to computer material
  • Unauthorised access to a computer without permission with intent to commit further criminal offences
  • Unauthorised modification of programs or data on a computer
  • Making, supplying or obtaining anything which can be used in computer misuse offences
31
Q

What are tracking cookies?

A

Cookies that record your details and are sent back to the author of the cookie - most are for collecting marketing data or targeting adverts

32
Q

How do tracking cookies become a security risk?

2

A
  • Tracking cookies can be set by programmers to send them usernames and personal data, which can be used in identity theft
  • Tracking cookies can track data such as location, device info, IP address and search history
33
Q

What is a DoS attack?

A

A deliberate attempt to prevent legitimate users of a network from accessing the services provided by a server or connected systems by bombarding a server with network messages to keep it busy

34
Q

What are the symptoms of a DoS attack?

2

A
  • Slow performance of the website or service
  • The inability to access data held on the website or service
35
Q

What are the effects of a DoS attack?

2

A
  • Disruption to users - unable to access server
  • Disruption to business - customers can’t access server
36
Q

What are the costs of a DoS attack?

2

A
  • Lost revenue - users can’t make purchases
  • Labour cost to fix fault
37
Q

What are the types of DoS attack faults?

3

A
  • Bandwith consumption - using all of the websites available bandwidth
  • Resource starvation - an attempt to use enough server resources to make the system unresponsive
  • DNS attack - modification of DNS record settings to point to a rogue DNS server
38
Q

What are the reasons for carrying out a DoS attack?

3

A
  • Financial - bringing down a commercial website will cost that company money
  • Political - prevent access to the website of a political rival
  • Personal - the attacker may have a personal grudge against the owner of the website
39
Q

What is encryption?

A

The act of scrambling a message so that it is unreadable to anyone who is not the intended recipient. You need a key in order to decrypt the message

40
Q

What are the types of keys used in encryption?

2

A
  • Public key
  • Private key
41
Q

What is a public key?

A

A public key can be distributed to anyone who wishes to send you a message and they use the public key to encrypt the data

42
Q

What is a private key?

A

A private key is only known by you. Only this private key can be used to decrypt the data created by the corresponding public key

43
Q

What are digital signatures used for?

A

To authenticate the identity of the sender and ensure that the content has not been modified on route

44
Q

What are digital certificates used for?

A

To verify that a user sending a message is who they claim to be. Certificates are issued by a certification authority

Higher Computer Science (3 decks)

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