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Computer Science AS > 1. Hardware and Communication > Flashcards

1. Hardware and Communication Flashcards

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1
Q

What are the types of secondary storage?

A
  • magnetic
  • solid state/flash
  • optical
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2
Q

What factors should be considered when choosing a secondary storage device?

A
  • capacity: amount of data that can be stored
  • speed: how quickly data can be accessed
  • portability: how easy the device is to physically move
  • durability: how much damage a device can withstand
  • reliability: how long a device will last
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3
Q

How do hard drives work?

A

Data is stored on a platter. Data is read and written using an arm that has a read/write head at the end. As the disk spins, the arm travels across the disk. Each sector of the platter can store data, and the combination of the platter spinning and the arm moving means every sector can be reached.

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4
Q

How does optical storage work?

A

Lasers are used to store data by burning microscopic indentations into discs. These indentations create pits and lands which are used to store binary data. A separate laser is used to read data by being aimed at the disk and reading back the reflections.

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5
Q

What is a protocol?

A

A protocol is a set of rules or formal description of the format of a digital transmission

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6
Q

List some common protocols

A

HTTP, FTP, SMTP, TCP/IP, IMAP, DHCP, UDP, Wi-Fi, Bluetooth, WAP, WPA, WEP

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7
Q

What is HTTP?

A

Hypertext Transfer Protocol
- fundamental protocol of the world wide web
- allows browsers to display and format web pages as the author intended
- HTTPS is the same but with encryption and authentication
- a stateless protocol, meaning that each request is independent, making interactive websites more difficult to program

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8
Q

What is FTP?

A

File Transmission Protocol
- used for transferring large files over a network
- in built error checking for lost packets
- data packets that arrive in a random order can be reassembled
- not good for streaming services as it is more important to continuously receive new data packets rather than lose time by retransmitting lost packets

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9
Q

What is SMTP?

A

Simple Mail Transfer Protocol
- allows emails to be sent over a network
- transfers outgoing emails to servers and from servers to clients

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10
Q

What is TCP/IP?

A

Transmission Control Protocol / Internet Protocol
- specifies how data is routed and transported around a network
- TCP provides error free transmission between networked computers
- IP routes data packets across a WAN

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11
Q

What is IMAP?

A

Internet Message Access Protocol
- allows emails to be transferred between computer systems via the internet
- emails are kept on the mail server rather than individual devices

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12
Q

What is DHCP?

A

Dynamic Host Protocol
- assigns unique dynamic IP addresses to devices on a network
- allows addresses no longer in use to be returned to the pool of available addresses

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13
Q

What is UDP?

A

User Datagram Protocol
- alternative to TCP but has no error checking or data recovery
- used to send short messages using datagrams
- speed is prioritised over accuracy

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14
Q

What are some examples of wireless communication protocols?

A
  • Wi-Fi: allows devices to communicate over a wireless signal
  • Bluetooth: used to exchange data over short distances
  • WAP (wireless application protocol): allows mobile devices to access the internet and intranet but is not widely used anymore
  • WPA (Wi-Fi protected access): developed to fix flaws in WEP by encrypting data on Wi-Fi networks
  • WEP (wired equivalent privacy): a security protocol for wireless networks but is now obsolete
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15
Q

What does the control unit do?

A
  • coordinates activities of all the components of a CPU
  • directs flow of data and instructions within the CPU
  • generates clock ticks
  • handles the FDE cycle
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16
Q

What does the arithmetic logic unit do?

A

Performs mathematical and logical operations with data within the CPU

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17
Q

What are the important registers?

A

MAR, MDR, ACC, PC, CIR

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18
Q

What does the memory address register do?

A

Holds the address of data/instructions to be fetched from or written to the CPU and sends it to memory down the address bus

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19
Q

What does the memory data register do?

A

Stores data/instructions to be fetched from or written to RAM. All data to and from RAM must pass through the MDR

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20
Q

What does the program counter do?

A

Indicates where a computer is in its program sequence and holds the address of the next instruction to be executed

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21
Q

What does the current instruction register do?

A

Holds the current instruction being executed or decoded. Instructions from the MDR are copied to the CIR

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22
Q

What does the accumulator do?

A

Stores data or control information and can temporarily store data from the ALU

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23
Q

What is a bus and what are the 3 buses found in the CPU?

A

A bus transports data between components of the CPU.
- Address bus: carries memory addresses
- Data bus: carries data
- Control bus: carries command and control signals

24
Q

What is RAM?

A

Random Access Memory
- volatile
- faster than hard disk
- stores data and instructions being processed by the CPU

25
Q

What is ROM?

A

Read-Only Memory
- non volatile
- contains the bootstrap

26
Q

How does the bootstrap work?

A

Firstly, a power-on self-test is carried out, which sends signals to all connected parts of the CPU to wake them up and makes the CPU aware of their existence. Now the computer is aware of the hard drive and can load the operating system into RAM.

27
Q

What is cache and how does it work?

A

Frequently used data and instructions are stored in the cache as it is a lot quicker to access than RAM due to it being located inside the CPU. When it is full, some of its contents are replaced by more recently used data.

28
Q

What are the levels of cache?

A

Cache has 3 levels. Level 1 is the faster, smaller and closer to the CPU, whereas level 2 is the larger and slower but still fairly close to the CPU. Level 3 works to improve the performance of levels 1 and 2 and is shared by all cores of a processor.

29
Q

What is a network?

A

Multiple devices connected to each other either wired or wirelessly

30
Q

What are the advantages of networks?

A
  • can share hardware
  • can share data/files
  • can share software
  • easier for internal communication
  • central backup of data
  • easier to monitor network activity
  • centrally controlled security
  • can access data from any connected computer
31
Q

What are the disadvantages of networks?

A
  • network manager could be expensive
  • files sent between computers could spread viruses
  • if server is down, all devices are affected
  • initial cost can be expensive
32
Q

What is the difference between LAN and WAN?

A

LAN stands for local area network and is used when the devices are geographically near each other.
WAN stands for wide area network and is used when the devices are geographically far apart.

33
Q

What is a topology?

A

An arrangement of links and nodes in a network

34
Q

What is a bus topology and its advantages and disadvantages?

A

Nodes are connected via a single cable and messages are sent to all nodes across the cable
A:
- easy to add more nodes
- quick and easy to implement
- cost effective
D:
- hard to troubleshoot
- limited cable length and number of nodes (performance degrades)
- if backbone fails, whole network fails
- low security as all nodes can see all data transmissions
- data collisions are more likely

35
Q

What is a ring topology and its advantages and disadvantages?

A

Data travels around the ring in one direction
A:
- no bottlenecks, consistent transfer speeds
- transmission is simple
- adding more nodes has little impact on bandwidth
- prevents data collisions
D:
- ring is broken if node fails
- if the cable fails, the whole network fails
- difficult to troubleshoot
- network must be shut down to add another node

36
Q

What is a star topology and its advantages and disadvantages?

A

All nodes are connected via a central node
A:
- good performance
- easy to set up
- nodes can be added without shutting the network down
- any non central failures will have little impact on the rest of the network
- minimal collisions
- better security
D:
- expensive to install due to lots of cabling
- extra hardware required e.g. hubs

37
Q

What is a data collision?

A

When two sets of data are detected simultaneously. The node that transmitted the data will then wait a short random amount of time before attempting to transmit the data again

38
Q

What is parallel processing?

A

Two or more processors work together to perform a single task. These tasks are executed simultaneously by all available processors. This allows large problems to be broken into smaller parts and processed quicker. Communication between all processors involved is crucial so that all processors are aware of changes to key pieces of data. Software has to be written specially in order to make use of parallel processing.

39
Q

What happens during the fetch stage of the fetch decode execute cycle?

A
  • the program counter is checked as it holds the address of the next instruction, which has been copied from RAM into the PC
  • the address is then copied to the MAR
  • the address is sent along the address bus to main memory, where it waits for a signal from the control bus
  • the control unit sends a read signal along the control bus to main memory to read what is stored in the MAR
  • the content stored in the MAR is sent along the data bus and copied to the MDR
  • the PC increases by 1 so the address points to the next instruction to be fetched
40
Q

What happens during the decode stage of the fetch decode execute cycle?

A
  • contents of the MDR are copied into the CIR
  • instruction held in the CIR is decoded by the decode unit
41
Q

What is an instruction made up of?

A

The first part of the instruction is the opcode, which tells the CPU what to do. The second part of the instruction is the operand, which tells the CPU what to do it to. The operand could contain the actual data or the address of the data in memory.

42
Q

What happens during the execute stage of the fetch decode execute cycle?

A

The processor carries out actions depending on the instructions.

43
Q

What are the methods of input?

A
  • optical character recognition
  • optical mark recognition
  • magnetic ink character recognition
  • touch input
  • voice input
  • vocabulary dictation
  • voiceprint recognition
  • QR codes
44
Q

What is optical character recognition?

A

This converts printed media into digital, editable text by scanning the printed media and pattern matching the shapes of the letters to known characters, which are stored as binary values in an internal database. This can be used for digitising books.

45
Q

What is optical mark recognition?

A

This is used to recognise the choices made on multiple choice forms. A special reader reads the form to detect whether or not a mark has been made. This can be used for exams and lottery tickets.

46
Q

What is magnetic ink character recognition?

A

Special ink containing iron oxide is used so that MICR readers can recognise it. This is used for bank cheques.

47
Q

What is touch input?

A

When touched, touch screens send the x and y co ordinates of the touch to the operating system, and a grid system is used to determine what action to carry out from there.

48
Q

What are the advantages and disadvantages of touch input?

A

adv:
- allows for intuitive gestures to be used, such as swipes and pinches
- no keyboard or mouse required
- easy to use as the user simply touches what is seen on the screen

disadv:
- it is difficult to select small items
- user must be within arm’s reach of the screen
- screens can be easily damaged

49
Q

What is voice input?

A

Commands are spoken into a microphone and the computer interprets these commands. The user is limited to set commands, such as turn up volume.

50
Q

What are the advantages and disadvantages of voice input?

A

adv:
- many people find talking more natural than typing
- keyboards and touch screens take up more space
- hands free, allows for multitasking

disadv:
- difficult to keep data private as people can hear what you are saying
- software may not be able to understand all accents
- background noise can interfere with speech recognition

51
Q

What is vocabulary dictation?

A

User speaks into a microphone and the spoken words are changed to text.

52
Q

What is voiceprint recognition?

A

The user’s voice is captured, digitised, and stored on a computer system. It is often used when attempting to gain access to high security rooms. When entry is attempted, the voiceprint of the user is compared to the voiceprints in the database. If a match is found, entry is permitted.

53
Q

What are biometric devices?

A

Devices that capture biometric data, such as fingerprints or faces, then pass it onto the computer for processing and identification.

54
Q

What are the advantages of QR codes compared to bar codes?

A
  • higher capacity
  • readable from any direction
  • scanning software is supplied by smartphones
  • damage resistant when printed
55
Q

What is fragmentation?

A

When files are split and stored on different parts of a disc. Fragmented files will load slower as the read/write head must move between parts of the file on the disc.

56
Q

What is defragmentation?

A

When parts of files on a disc are physically rearranged so that they are stored together. This increases loading speed as the read/write head does not need to travel as much distance to find all parts of the file.

Computer Science AS (18 decks)

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