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Computer science A level > Input output devices > Flashcards

Input output devices Flashcards

1
Q

what do barcodes do

A

Barcode readers are used to quickly and accurately scan barcodes

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2
Q

when are 2d barcodes used

A
  • ticketless entry to concerts
  • ## boarding trains
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3
Q

advantages of laser scanners

A
  • available in a variety of forms
  • reliable and economical for low volume applications
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4
Q

examples of laser scanners

A
  • CCD readers
  • Camera based readers - used for age verification or event ticketing
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5
Q

how do digital cameras work

A
  • shutter opens to let light on CCD
  • Each sensor produces an electrical current/signal
  • The signal represents a pixel;
    An (ADC) converts measurement of light intensity into binary/digital data;
    -filter is applied to generate separate data values for red, green and blue
    colour components;
  • The pixels are recorded as a group / array;
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6
Q

what does a digital camera use

A

a CCD or CMOS

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7
Q

advantages of CCD sensor

A
  • produces higher quality images
  • used in higher end cameras
  • more reliable since the technology has been around longer
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8
Q

disadvantages of a CCD compared to a CMOS

A
  • cost of power consumption, uses up to 100 times that of CMOS sensor
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9
Q

what are RGB filters used for

A

to separate out wavelengths

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10
Q

how do RFIDs work

A
  • RFID tag contains circuitry and antenna
  • RFID reader transmits electromagnetic field
  • signal activates current in RFID tag
  • RFID reader converts radiowaves back into binary
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11
Q

how does a laser printer work

A
  • printer generates bitmap from the data
  • printer drum coated in charge
  • laser beam shone on drum
  • laser removes electric charge on drum
  • toner is given positive charge
  • charged drum picks up toner(one for each colour)
  • toner transferred to paper
  • toner is fused while on paper
  • discharge lamp removes any remaining electrical charge
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12
Q

how to prevent sticking in laser printing

A

the electric charge on the drum is removed

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13
Q

how does a barcode work (light source)

A
  • light source directed at barcode
  • prism moves light beam across barcode
  • light is reflected back
  • black reflects less light, white reflects more
  • light sensor measures the intensity of light reflected back
  • and converts it into binary
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14
Q

digital camera barcodes process

A
  • CMOS sensor measures light intensity at a point
  • sensor outputs voltage, dependent on light intensity
  • voltage turned into binary via ADV
  • image processing software analyses image
  • and identifies black and white bars in barcode
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15
Q

How do discs work

A
  • laser shone on disk
  • light is focused on spot on track
  • light is reflected back from disk
  • amount of light reflected is measured
  • disc spins at constant linear velocity
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16
Q

hows data represented using a disc

A
  • data is stored on one track
  • continuation of pit reflects light whereas transition between land and pit scatters light
  • transition between land and pit indicates a 1 and continuation of land/pit represents 0
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17
Q

advantages and disadvantages of secondary storage

A

advantages - provides non-volatile memory that retains information even when the computer is turned off. This enables long-term storage of programs

disadvantages - secondary storage is not directly accessible to the processor and has slower access speeds

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18
Q

problems with primary storage

A

its volatile, if you turn the computer off, data gets lost

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19
Q

characteristics of hard disk

A
  • they help fit more data in the same physical space
  • they are more densely packed
  • ## use magnetic storage to store data.
20
Q

what is latency

A

the time taken to read/write disk data

21
Q

examples of latency

A

seek delay - the time the head takes to move across the disk
rotational delay - the time the disk takes to move to the correct sector underneath the read/write head

22
Q

examples of optical disk formats

A
  • read only
  • recordable
  • re writeable
23
Q

recordable formats features

A

uses a transparent dye that becomes opaque when heated by a laser

24
Q

rewriteable format features

A

uses a laser to change the state of a phase change alloy and a magnet to set the new state

25
Q

what is a solid state disk

A

a disk that compromises millions of NAND memory cells

26
Q

how do optical disks work

A
  • a high powered laser burns pits into the CD surface
  • a low powered laser detects the reflection from pits and lands
  • only a put end deflects the laser light end and is read as a binary 1
  • a high powered laser burns pits into the CD surface
27
Q

Definition of drive

A

a device that reads and writes data from secondary storage

28
Q

What is media?

A

What the data is actually stored on

29
Q

Advantages and disadvantages of optical storage

A
  • Cheap
  • light weight
  • portable

Access times for optical disks are generally slower compared to hard disks
- have lower storage capacities compared to hard disks, making them suitable for storing smaller amounts of data.

30
Q

advantages and disadvantages of magnetic storage

A
  • cheap
  • large capacity

BUT
- slow access time and fragile

31
Q

how fast does a disk spin

A

speeds of up to 10,000 RPM

32
Q

features of a hard disk

A
  • a drive head moves across the disk to access different tracks and sectors
  • data is read or written to the disk as it passes under the drive head
33
Q

what happens to the drive head when it’s not being used

A

it’s parked to one side of the disk in order to prevent damage

34
Q

hard disk uses and why

A

huge capacity makes them suitable for desktop surfaces

35
Q

how much data can a CD ROM hold

A

650MB

36
Q

how much data can a blue ray hold

A

50GB

37
Q

uses of optical storage

A
  • small backups and storing music
38
Q

how do SSDs work

A
  • data is stored electronically, data is stored in floating gate transistors
  • electrons are trapped between oxide layers
  • NAND memory is used
  • data is organised into blocks
  • a whole block of data must be written
  • a block must be erased before it is overwritten
  • controller manages the organisation of the data
39
Q

why is an SSD is a better choice than a magnetic hard disk

A
    • SSDs have lower power drain; which is important as the life blogger will run on
      battery;
  • SSDs are less likely to be damaged if dropped; which is important as the devices will
    be worn and carried around;
  • SSDs have faster access time; which could allow more data to be stored per second
    (which may allow finer detail);
  • SSDs are silent; which means they will not disturb the users;
  • SSDs are lighter/less obtrusive/smaller; which is important for a device worn around
    the neck;
  • SSDs produce less heat; which makes them more comfortable to wear;
40
Q

adv and disadv of laser printers

A
  • fast printing speeds, making them ideal for environments where large volumes of documents need to be printed quickly.
  • Laser printers produce crisp, sharp text and images with high resolution.
  • Laser printers consume more energy during operation compared to inkjet printers
  • there is a risk of toner smudging or streaking
  • higher upfront cost
41
Q

advantages and disadvantages of rfids

A
  • RFID systems can automate data collection and identification processes, improving efficiency
  • RFID enables real-time tracking of items throughout the supply chain, helps inventory management
  • you have to be close to the RFID tag for it to work
  • RFID tags can store and transmit unique identification data, raising privacy concerns about unauthorized tracking and surveillance.
  • costly, especially for large-scale deployments
42
Q

advantages and disadvantages of digital cameras

A
  • Digital cameras use digital memory cards to store images, for hundreds or even thousands of photos,
  • users can easily transfer photos to computers, smartphones, or other devices
  • Digital photos stored on memory cards or electronic devices are vulnerable to data loss due to hardware failure
  • Digital cameras rely on batteries to power their operation, and battery life can vary depending on usage
43
Q

advantages and disadvantages of barcode readers

A
  • Barcode readers come in various forms, including handheld scanners, fixed-mount scanners, and mobile devices with built-in scanning
  • Barcode scanning reduces the risk of human error associated with manual data entry
  • Traditional barcode readers require a direct line of sight between the scanner and the barcode label to read the barcode accurately.
  • Barcode labels can be easily duplicated or tampered with, raising security concerns
44
Q

what are rfids

A

RFIDs provide a wireless means of identifying and tracking objects,

45
Q

disadvantages of SSDs

A

Lower latency but faster transfer
speeds than a magnetic disk drive.

Computer science A level (25 decks)

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