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Computer Science > 3.2 (A) Input Devices > Flashcards

3.2 (A) Input Devices Flashcards

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1
Q

What is a barcode

A

a series of dark and light parallel lines of varying thickness

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2
Q

Process of scanning a barcode

A

Read by a laser or led light source

Light is reflected of the barcode - the white lines reflect more light compared to the black lights

The reflected light is read by sensors

A pattern is generated by the light that is reflected which is converted into digital data

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3
Q

What happens after the barcode is read (supermarket)

A

The barcode is looked up in stock database

When the barcode number is found, the stock item record is looked up

The price and other stock item details are sent back to the checkout or the POS

the number of stock items in the record is reduced by 1 each time the barcode is read

this new value for number of stock is written back to the stock item record

the number of stock items is compared to the re-order level; if it is less than or equal to this value, more stock items are automatically ordered

once an order for more stock items is generated, a flag is added to the record to stop re-ordering every time the stock item barcode is read

when new stock items arrive, the stock levels are updated in the database.

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4
Q

What is a key field

how does it relate to a barcode

A

the field that uniquely identifies a record in a file

barcode acts as a key field for items in a supermarket

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5
Q

What is the POS

A

point of sales terminal

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6
Q

Advantages of barcodes (managers)

A

Automatic stock control

More up-to-date sales information and sales trends

Much faster and easier to change prices on stock items

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7
Q

Advantages of barcodes (customer)

A

Faster checkout queues

Errors in billing are reduced

An itemized bill is given to the customer

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8
Q

What is a QR code

A

a matrix of dark and light squares which represent data

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9
Q

Full form of QR

A

Quick Response

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10
Q

How can a QR code be read

A

QR code apps and smart phone cameras

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11
Q

Common uses of QR codes

A

Advertising
Restaurant menus
Storing boarding passes of flights and trains

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12
Q

How a QR code is read

A

Point the phone camera towards the QR code

The app will process the image of the QR code, converting the squares to readable data

The data is then read and the user is directed to the website, phone app, or the data stored in the qr code is downloaded on the user’s phone.

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13
Q

Advantages of QR code compared to Bar code

A

More information

Few errors - QR Codes have a built in error checking systems. This helps guard against badly printed, damaged QR codes

Easy to read - don’t need a laser or an led light source

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14
Q

Disadvantages of QR codes

A

Can be used to transfer malicious codes. It is very easy to embed malicious code into a QR code. This code could be a virus, etc.

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15
Q

What is the process of transferring malicious codes through a QR code called

A

Attaging

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16
Q

What is a Frame QR code

A

a type of QR code that includes a space for advertising

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17
Q

What happens when a photo is taken (camera)

A

Light passes through the lens onto a light sensitive cell which converts light into electricity

Each tiny sensor is called a pixel

The image is converted to tiny electric charge which is then passed through an ADC to form a digital image array

The ADC then converts the electric charge from each pixel to levels of brightness

Finally, apart from brightness, the sensors also measure colour which produces another binary pattern

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18
Q

What is a CCD (Cameras) - full form and function

A

Charged Couple Devices - a light sensitive cell made up of millions of tiny sensors acting as photodiodes. Converts light into electricity

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19
Q

What is an ADC (full form and function)

A

Analogue to digital converter – a device that converts analogue data into a form understood by a computer

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20
Q

X-bit adc gives how many levels of brightness

A

2^x diff levels of brightness

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21
Q

What colour system do most cameras use

A

24-bit RGB Colour system - 3 primary colours, each get 8 bits.

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22
Q

What does the number of pixels in the picture determine

A

size of the file used to store the photograph

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23
Q

What does the quality of the image (camera) depend on

A

Recording device (how good the camera lens is and how good the sensor array is)

Number of pixels used (the more pixels used, the better the image)

Levels of light and how the image is stored (JPEG, raw file, png, etc)

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24
Q

What is a DAC (full form and def)

A

Digital to analogue converter - device that converts digital data into electric currents

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25
Q

What is a virtual keyboard

A

an onscreen keyboard which uses the features of the touch screen to emulate a physical keyboard

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26
Q

How does an ergonomic keyboard tackle RSI

A

these have the keys arranged differently

They are also designed to give more support to the wrists and hands when doing a lot of typing.

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27
Q

What is RSI (full form and def)

A

repetitive strain injury - pain felt in the muscles,
nerves and tendons caused by a repetitive action (for
example

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28
Q

How does a computer recognize the letters being pressed on the keyboard

A

There is a membrane or circuit board at the base of the keys

When the key is pressed the circuit is completed

The CPU in the computer can then determine which key has been pressed by referring to an index file to identify which character the key press represents

Each character on a keyboard has a corresponding ASCII value

29
Q

What does a microphone do

A

Converts sound waves into an electric current. The current is then converted to a digital format so that the computer can process/store it

30
Q

How does the microphone work

A

When sound is created, it causes the air to vibrate.

The diaphragm in the microphone picks up the air vibrations and begins to vibrate itself

A copper coil is wrapped around the cone which is connected to the diaphragm. When the diaphragm vibrates, the cone moves in and out causing the copper coil to move backwards and words

The motion of the coil allows it to cut through the magnetic field of the permanent magnet, which induces a current

This current is then amplified or sent to a recording device

31
Q

What is the nature of the current gen by the microphone

A

analogue

32
Q

What is an optical mouse

A

a pointing device that uses a red LED to track the movement of the device and then relays its coordinates to a computer

33
Q

What is a pointing device

A

an input device that allows the user to control the movement of an onscreen cursor or to allow onscreen selection by clicking a button on the device

34
Q

How many images per second does an optical mouse take

A

1500

35
Q

What is a CMOS (full form and func)

A

complementary metal oxide semiconductor - a chip that generates an electric current when light falls on its surface

36
Q

What is a DSP (optical mouse)

A

digital signal processor - a processor that calculates, the coordinates of a pointing device based on the pulses of electricity received

37
Q

How does an optical mouse work

A

Red light is bounced off the surface
Reflection is picked up by the CSMO
CSMO generates electric pulses to represent the reflected red light

Pulses sent to a DSP

The DSP works out the coordinates of the mouse based on the changing image patterns as it is moved about on the surface

Computer reflects the movement on screen according to the coordinates sent by the mouse.

38
Q

Why an optical mouse is better than a mechanical mouse

A

No moving parts - more durable

Dirt can’t get trapped in any of the mechanical components

No special surfaces are required

39
Q

Advantages of wired connections over Bluetooth and wireless (mouse)

A

No signal loss - consistent pathway

Cheaper to operate - no need to buy batteries over and over again

40
Q

What is a 2D scanner

A

Most common form of scanners that are used to input hard copy (paper) documents

41
Q

How a 2D scanner works

A

Cover is raised, paper is placed on the glass, cover is closed

A bright light illuminates the document using a xenon lamp or LED that produces a bright white light

Scan head moves across the document, to scan the full document.
An image of the document is produced - is then sent to a lens using a series of mirrors.

The lens focuses the document image.

The focused image falls onto a CCD, converts light to electric current which converts it into an electronic form

Software produces a digital image from electronic form

42
Q

What is an OCR (full form and function)

A

Optical character recognition - Technology that can convert hard copy text or images into a digital format such as a text file that is to be stored in a computer memory

43
Q

What is a 3D scanner

A

Scan solid objects and produce a three-dimensional image.

Take images on several different points along the X, Y and Z coordinates.

44
Q

Where can the images from a 3D scanner be used to design and create

A

CAD - computer aided design which is a software used to create drawings

45
Q

What is a application of a 3D scanner

A

Computed tomographic scanners.

46
Q

What does a CT scanner do

A

used to create a 3D image of a solid object

47
Q

How does a CT scanner work

A

uses tomography technology, builds up an image of the solid object through a series of very thin ‘slices’.

48
Q

What is a touchscreen

A

Allows the user to select or

manipulate a screen image using the touch of a finger or stylus

49
Q

3 Types of touchscreen

A

resistive
Capacitive
Infrared

50
Q

What is a capacitive screen made out of

A

Composed of layers of glass, a transparent electrode, and a glass substrate.

51
Q

How does a capacitive screen work

A

Human skin is a conductor of electricity, when bare fingers touch the screen, the electrostatic field of the conductive layer is changed.

The installed microcontroller is able to calculate where this change took place and hence determine the coordinates of the point of touching.

52
Q

Two types of capacitive screens

A

Surface

Projective

53
Q

How does a surface capacitive screen work

A

sensors are placed at the corners of a screen.
Small voltages are also applied at the corners of the screen creating an electric field finger touching the screen surface will draw current from each corner
reducing the capacitance.

A microcontroller measures the decrease in capacitance and hence determines the point where the finger touched the screen.

54
Q

How does a projective capacitive screen work

A

The transparent conductive layer is now in the form of an X-Y matrix pattern.

This creates a three dimensional (3D) electrostatic field. When a finger touches the screen, it disturbs the 3D electrostatic field allowing a microcontroller to determine the coordinates of the point of contact.

55
Q

Surfaces that can control a surface capacitive screen

A

bare fingers

stylus

56
Q

surfaces that can control a projective capacitive screen

A

bare fingers
stylus
thin surgical or cotton gloves

57
Q

What other facilities does a projective capacitive screen allow for

A

Multi-touch

58
Q

Advantages of capacitive screens compared to others

A

Better img quality comp to resistive

Durable

Projective allow multi touch

59
Q

Disadvantages of capacititive screens comapred to others

A

Surface capacitive screens only work with bare fingers or stylus

This screen is sensitive to electromagnetic radiation

60
Q

What is an infrared touch screen

A

Infrared touch screens use a glass screen with an array of sensors and infrared transmitters

61
Q

How does an infrared touch screen work

A

The sensors detect the infrared radiation.

If any of the infrared beams are broken (for example, with a finger touching the screen), the infrared radiation reaching the sensors is reduced.

The sensor readings are sent to a microcontroller that
calculates where the screen was touched

62
Q

Advantages of infrared touch screens comp to others

A

Multi-touch

good durability

operability isn’t affected by a scratched or cracked screen

63
Q

Disadv of infrared touch screens comp to others

A

Screen is sensitive to water and moisture

Accidental activation can take place if beams are broken by any other objects or are disturbed in someway.

Could be sensitive to light interferance

64
Q

What is a resistive touch screen

A

made up of two layers of electrically resistive material with a voltage applied across them

65
Q

What is the upper layer of a resistive touch layer made of

A

made of flexible polyethylene (a type of polymer) with a resistive coating on one side

66
Q

What is the lower layer of a resistive touch layer made of

A

The bottom layer is made of glass also with a resistive coating (usually indium tin oxide) on one side

67
Q

How does a resisitive screen work

A 
These two layers are separated by air or an
inert gas (such as argon).

When the top polyethylene surface is touched, the two layers make contact.

Since both layers are coated in a resistive material a circuit is now completed which results in a flow of electricity.

The point of contact is detected where there was a change in voltage.

68
Q

Adv of resistive touch screens comp to others

A

Good resistance to dust and water

Can be used by bare fingers, stylus and gloved hands

69
Q

Disadv of resisitive touch screens comp to others

A

Low touch sensitivity

Doesn’t allow multi-touch

Poor visibility in strong sunlight

Vulnerable to scratches on the screen

Computer Science (28 decks)

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