External Hardware Devices

Question 1

What is a barcode and what is its function?

Answer 1

Printed diagrams that consist of black white portions. Scanned and read by computer and it usually holds information about the item that is scanned.2 types 1D and 2D.

Question 2

Advantage of 2D barcodes

Answer 2

Contain more information than 1D in the same amount of space but they require more processing.

Question 3

What do barcode readers consist of:

Answer 3

Laser light source
Lens
Mirror
Photodiodes

Question 4

Explain what the white and dark sections do in a barcode

Answer 4

White = reflects light
Black= absorbs light.
The pattern of black and white strips represents binary 1s and 0s

Question 5

What are the prevention methods which are used for error detection in barcodes?

Answer 5

Parity bits and check digits allow computer tell whether the barcode has been read incorrectly.
Eg : If barcode fails to scan then it will continue to scan until it has been read correctly.

Question 6

What do digital cameras consist of ?

Answer 6

Consist of a lens that focuses light on a sensor and the path between the sensor and lens is controlled by a shutter.

Question 7

Name 2 sensors commonly used in digital cameras and their use for them?

Answer 7

CMOS and CCD. Which convert light into an electrical charge.

Question 8

How do the sensors work?

Answer 8

Charge builds in the cells, each cell represents a pixel in the image. When the photograph is taken then the charge in cells is converted into a digital value which is processed by a camera and stored as a digital image.

Question 9

What happens in colour cameras in order for the colour to be detected?

Answer 9

Each pixel has multiple cells, each of which has a filter that allows in certain wavelengths of light. THIS lets the camera build up a separate image for the intensity of each colour of light, which is combined and forms a colour photograph.

Question 10

What is a laser printer?

Answer 10

Device that produces images on paper from digital signals.

Question 11

What do laser printers consist of ?

Answer 11

Laser light
Toner
Mirror
Drum
Fusers

Question 12

How does there printing work?

Answer 12

Before the laser is pointed at the drum it is already positively charged.
Toner roller dispenses negatively charged toner onto the drum and because opposites attract, the toner is attracted to the positively charged portions of the drum.
Toner is then applied on the paper before the paper is then heated by the fusers, fixing the toner to the paper.

Question 13

What is RFID and what is it used for ?

Answer 13

Method of transferring information wirelessly between a tag and a reader.

Question 14

What is inside an RFID?

Answer 14

A chip that is attached to a wire and it acts like an antenna.

Question 15

What is meant by active and passive RFID tags?

Answer 15

Passive |: they induce enough power wirelessly from the reader to operate the chip. These have to within a few cm of its reader.
Active : contain a small power like a battery. These can be held far from the reader.

Question 16

What happens when an RFID is scanned?

Answer 16

1. Reader emits radio waves which are picked up the the tags antenna
2. Power that is taken in by the antenna from the radio waves are enough to power the chip.
3. Chip then uses the antenna to emit its own radio waves which contain information held on the chip.
4. Wave is picked up the reader and then it decoded and the information is then presented on the computer.

Question 17

What is meant by a computers primary and secondary storages?

Answer 17

Primary storage refers to RAM AND ROM.
Secondary storage refers to SSDs, Hard Disk Drives..

Question 18

Explain what hard disk drive is?

Answer 18

Consist of layers of platters that have an arm which is a read/write head.

Question 19

What does the arm do?

Answer 19

Changes the magnetic polarity of the platter to access all portions of the platter.

Question 20

How does the HDDs work? ADS AND DISADS

Answer 20

Platter rotates thousand of times which allows for quick read and write speeds.
Non portable and can damage easily.

Question 21

How do SSDs works?

Answer 21

Have NAND memory flash cells which store information and trap an electrical charge.
Data is stored in pages which are combined to form blocks.

Question 22

ADS AND DISADS OF SSDs

Answer 22

DISADS: in order to write new info it erases the entire page.
ADS: have high read and rite speeds.
Are portable

Question 23

How is info stored on an optical disk?

Answer 23

Read optically by a laser
Can be read only, recordable or rewritable.

Question 24

How do optical disks work?

Answer 24

Pits are burned onto the disk by a laser permanently deforming the surface.