Topic 7.4 External Hardware Devices Flashcards

1
Q

What is the purpose of a Barcode Reader

A

To identify the products being purchased

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2
Q

How does a Barcode Reader work

A
  • Barcodes on the product contain the information
  • Mirror directs the light from the Reader onto the barcode
  • Light is reflected by the barcode and passes through the lens
  • Light is turned into an electrical charge
  • Electrical charge is measured and processed to form a digital signal containing the contents of the barcode
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3
Q

What is the purpose of a Digital Camera

A

Device that takes photos and stores them in a digital format

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4
Q

How does a Digital Camera work

A
  • Shutter opens (LOL)
  • Lens of the camera focuses light onto a sensor
  • Sensor converts light into electrical charge
  • Each electrical charge represents a different pixel in the image
  • Charge is converted to a digital value and stored as a digital image

If colour camera
- Multiple cells for each pixel in the image

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5
Q

What is the purpose of a Laser Printer

A

Produces images on a paper from digital signals

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6
Q

How does a Laser Printer work

A
  • Drum is positively charged everywhere
  • Laser is directed onto the drum by the
    mirror
  • Places on drum where laser hit lose their
    charge (neutral or 0 charge)
  • Negatively charged toner is put onto the
    positive charge parts of the drum
  • Toner applied to paper from the drum
  • Paper is heated, fixing the toner to the paper
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7
Q

What is the purpose of RFID

A

Used to transfer information wirelessly between a tag and a reader.
Used in contactless debit cards and hotel room cards.

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8
Q

How does RFID work

A
  • Chip inside the RFID tag contains small amount of memory.
  • When tag is scanned, the reader emits radio
    waves to pick up the tag’s chip
  • Power from these waves is enough to power
    the chip
  • Tag emits its own radio wave which contains
    the information
  • Reader picks up wave and returns information to the computer
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9
Q

What is the need for Secondary Storage in a Computer System

A

In main memory, data is lost when the computer turns off.
In secondary storage, the data and programs are kept indefinitely.

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10
Q

How does a Hard Disk Drive (HDD) work

A
  • Consists of a number of circular platters.
  • Above each platter there is a read/write head
  • Platter spins rapidly so read/write head can access / add data quickly
  • To increase capacity you can add more platters
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11
Q

How does a Solid-State Drive (SSD) work

A
  • Consist of NAND flash memory cells
  • And a controller that manages the structure of data on the drive
  • Data is stored in pages
  • When data needs to be overwritten, the whole page must be completely erased
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12
Q

How do Optical Disks work

A

Pits and Lands
- Pits burnt into disk by laser
- Light is sent onto the disk
- If light reflects diagonally, means it is changing from land to a pit
- If light reflects straight up means it is staying as it is
- So can be read in binary as a pit = 1 and land = 0

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13
Q

Compare the Capacities of the Secondary Storage Devices

A

HDD - VERY high capacity (500GB - 5TB)

SSD - relatively low ( >1TB)

Optical Disk - VERY low ( >25GB)

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14
Q

Compare the read/write speeds of the Secondary Storage Devices

A

HDD - Relatively good = 100MB/s

SSD - VERY good = 500MB/s

Optical Disk - Very low = 30MB/s

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15
Q

Compare the Latency of the Secondary Storage Devices

A

HDD - High

SSD - VERY low

Optical Disks - High

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16
Q

Compare the Portability of the Secondary Storage Devices

A

HDD - Bad - Bulky and Heavy

SSD - Good - Lightweight & Rarely damaged

Optical Disks - Average - Lightweight but can be damaged by scratches

17
Q

Compare the Suitability of the Secondary Storage Devices

A

HDD - Desktop Computers & Servers

SSD - Laptops & Phones

Optical Disks - Music / small amounts of data