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Computing COMP2 > 4. Hardware Devices > Flashcards

4. Hardware Devices Flashcards

1
Q

How does a digital camera work

A
  1. Light is focused in lens onto image sensor
  2. Image sensor is an array of RGB photo sensors - Bayer filter
  3. Individual colour arrays combined to form image
  4. RGB values captured, stored digitally to flash memory card
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2
Q

Define Mouse

A

Enable the user to exectueicommands or instructions to computer by controlling an onscreen pointer

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3
Q

Define keyboard

A

Alphabetical and numerical keys that complete a circuit when pressed down. This transmits a binary signal, usually in ASCII of the key pressed

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4
Q

Define voice recognition

A

Microphone connected to software that converts human speech into commands or text.
Often struggles with similar words, and accents

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5
Q

Explain how a barcode reader works

A
  1. Laser is directed at the barcode, scanning across it.
  2. The reflected light is captured by the reader
  3. High light intensity means it is a white bar, low light intensity means black bar.
  4. The pattern is translated into binary code to give the identity of the item
  5. The code is checked against a database. Data information is displayed
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6
Q

Define Optical Code Reader

A

Black marks filled in to represent answers (often used in multiple choice tests).
Fed into a machine that uses the location of the black dots to determine the answer.
This allows lots of tests to be marked quickly

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7
Q

Define Optical Character Reader

A

Used in scanning written text ps or books. Scans the contents of page and translates the image into the text it represents

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8
Q

Define Magnetic Strip Reader

A

Used to read data from bank cards

data is stored in binary on black magnetic strips on the back of the card

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9
Q

Devein Smart Card Reader

A

Used as the ‘Chip and Pin’ in bank cards.

Data is stored on an integrated circuit

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10
Q

Define RFID

A

Radio Frequency Identification

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11
Q

Explain how an RFID reader works

A
  1. RFID chip with antenna is stored inside a card
  2. A card is placed above a reader, which produces a magnetic field to create a current in the card (no contact needed).
  3. Current powers a small transistor that sends data out as a radio signal.
  4. Data is received and read by the reader
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12
Q

Explain how a Touch Sensitive Screen works

A
  1. Each corner of the screen emits a uniform electric field over the screen
  2. Placing a finger on the screen disrupts the field and draws current
  3. Measuring the current in each corner allows the location of the touch to be triangulated by the computer
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13
Q

Define Graphics Tablet

A

Used for design and architecture
Draw on the tablet using a stylus. Pressing the stylus on the screen operates a micro switch which allows the movement it be recorded by the computer. The board contains electronics to determine the location

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14
Q

Explain how a Flatbed Scanner works

A
  1. Place an object face down on the glass pane
  2. Under the glass, light moves along from the start of the document, illuminating a slice
  3. The slice is reflected onto the CCD ( image sensor array) where the image is stored as digital data
  4. The light and mirror move onto next slice, repeating the process
  5. Document is combined to create a digital image
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15
Q

Define Flatbed Scanner

A

Used to convert images and text into a digital format

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16
Q

Explain how a finger print scanner works

A

The ridges and troughs in a finger print are unique.
This is scanned and recoded into a database.
Fingerprints are scanned and compared to this database

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17
Q

Retina Scanner

A

Records the unique pattern of blood vessels in the back of the eye

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18
Q

Explain how an iris scanner works

A

Takes a picture of the unique blood vessels and colour in the back of the eye.
This can be changed with the use of contact lenses

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19
Q

Define Check Digit

A

An additional digest added to a data string to check the string has been sent correctly.
If it has not, it will need to be sent again

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20
Q

Define Input Device

A

Devices that send data or instructions into a computer

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21
Q

Define output device

A

Device that computer sends data or instructions to

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22
Q

Explain CRT

A

Cathode Ray Tubes

3 RGB electron guns fire electrons at phosphor lined screen. This produces a colour image.

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23
Q

Explain Flatscreen LCD

A

Made up of an array of RGB sub-pixels. The pixels are placed between polarised frills that show or hide the sub-pixel when an electric current is applied. This creates the image

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24
Q

Why is CRT better than LCD

A

More viewing angles

Doesn’t have to use a specific resolution

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25
Q

Why is LCD better then CRT

A

Smaller, thinner, uses less power
Screen geometry almost perfect as there is no projection
No flicker

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26
Q

Explain plasma screens

A

Each pixel is controlled by a mini florescent light. When the control voltage is applied, this releases UV light and becomes plasma.
This hits the phosphor screen to create an image.

27
Q

Advantage of LCD

A

Small, light, doesn’t use lots of power, screen geometrically correct.

28
Q

Define speech output

A

Words in electronic documents can be output as spoken words using synthesis software through a sound card and speakers

29
Q

Define Electronic Paper

A

Creates images using tiny coloured balls that rotate or move in response to an electric charge to change the image.

30
Q

Describe an Impact Printer

A

Dot Matrix Printer. Used for anything that requires force, like carbon copies or Multi-Part Stationary.
The ribbon is struck hard by metal pins to create a letter on a vertical line by line basis

31
Q

Explain An Inject Printer

A

Non Impact printer, droplets of ink sprayed onto paper to create image

32
Q

Explain how an Inject Printer works

A
  1. Paper fed into printer
  2. Print head contains cartridges of CMYK (cyan, magenta, yellow, BLACK) ink.
  3. Print head moves from side to side spraying particles of ink
  4. Paper is fed through so ink covers whole page
33
Q

Advantage of Inkjet Printer

A

Cheaper than lasers, produces high quality images

34
Q

Define Laser Printer

A

Non impact printer that rapidly produces high quality text or graphics. Used with vectors

35
Q

Explain how a Laser Printer works

A
  1. Drum is given a negative charge
  2. The laser erases the charge in the correct place for the image
  3. Drum covered in negatively charged toner which is repelled by the charge
  4. Drum is rolled over page, transferring the image
  5. Paper goes through heated rollers which melt and seal toner onto paper
36
Q

Advantage of laser printer

A

Fast, cheap in large volumes

37
Q

Define Plotter

A

Non impact , used for vector graphics or text

38
Q

Explain how a plotter works

A
  1. Paper placed in plotter
  2. Plotter arm selects ink of correct colour
  3. Arm moves pen to area where plotting begins
  4. Pen is lowered onto paper and arm moves it, creating a continuous image
  5. Pen raises and can change ink colour
39
Q

Define Seek Time

A

Average time taken from requesting data to data being read

40
Q

Define Capacity

A

The amount of data it is possible to save

41
Q

Define Write type

A

Whether device is Read-Only, Write-Only or readable and writable

42
Q

Define Secondary Storage Device cost

A

How much it costs per megabyte

43
Q

Define Access type

A

Random access or serial access

44
Q

Define Magnetic Media

A

Assigns a magnetic charge to metal to represent binary 1s and 0s

45
Q

Define Hard Disk Platter

A

Magnetised magnetic disks that store data. Spins thousands of times per second.
There may be multiple platters that store data on both sides.
Platter is split into cylindrical tracks, and then sectors

46
Q

Define Hard Drive Head

A

Reads magnetic data from platter. May be 2 heads per platter for top and bottom

47
Q

Define Hard Drive Actuator Arm

A

Used to move head in and out of the platter as it spins to easily access data

48
Q

Define Hard Disk Track

A

Cylindrical concentric rings on the platter

49
Q

Explain how Hard Disk works

A
  1. Platters spin around spindle
  2. Data is requested on specific track/ sector on platter
  3. Actuator arm moves head to correct location
  4. Once the disk has spun around, the data has been read
  5. Data is sent to main memory
50
Q

Advantages of Hard Disk

A

Cheap, stores up to 4 terabytes, readable and writable
Fast Seek time, low cost, high capacity, Random access
Can be physically damaged easily

51
Q

Explain how Magnetic Tape drive works

A

Data is stored on a read only section of magnetic tape.

Data is serial and must be read through to locate. Not Random access

52
Q

Advantages of Magnetic Tape

A

High capacity, cheap.

But serial data

53
Q

Define Optical Media

A

Disk has pitted magnetic surface to represent Binary 1s and 0s.
Pits get closer and smaller for higher capacity devices

54
Q

Define CD ROM

A

Read only, 650mb

55
Q

Define CD-R

A

Read / write once. 650 MB

56
Q

Define CD -RW

A

Re-Writable, 650MB

57
Q

Define DVD ROM

A

Read only, 4.7 - 9.4 GB

58
Q

Define DVD-R

A

Write once, then read only, 4.7 -9.4 GB

59
Q

Define DVD -RW

A

Re-writable, 4.7-9.4 GB

60
Q

Define Blu-Ray

A

Re-writable and read only versions available. 25 -128GB.

Uses blue laser with much smaller pits and lands to store mor data

61
Q

Explain how USB flash drive READS

A
  1. Insert USB. USB driver allows computer to read/write to flash drive
  2. USB folder structure is sent to computer so user can choose files
  3. USB returns data from chosen location
62
Q

Explain how USB Flash drive WRITES

A
  1. Insert USB. USB driver allows computer to read/write to flash drive
  2. USB folder structure is sent to computer so user can choose files
  3. Computer sends data to the USB Flash drive, data placed in empty space.
  4. USB flash drive sends updated folder structure to computer
63
Q

Advantages of USB Flash drive

A

Fast Seek times, cheap.

Limited capacities and expensive per MB compared to Hard Disk Drives

64
Q

Define Memory Card

A

Works in the same way as USB flash drives. Often has different connectors and smaller sizes that allow them to be used inside other devices like cameras and phones.
Can be turned into USB Flash drives.

Computing COMP2 (7 decks)

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