3.3 Input Devices

Question 1

Input device

Answer 1

An input device converts data into digital signals that can be processed by the computer.

Question 2

Besides sending text, what can keyboards do?

Answer 2

1. Have additional keys that let you control what the computer does. Keys can be pressed alone or in combination.
2. eg. Control+Alt+Delete restarts the computer
3. Control keys work by sending control signals to the processor.

Question 3

Describe how the 3 types of mouse detect movement.

Answer 3

1. Early mouse designs had a rolling ball underneath, and electrical sensors detected the movement of the ball as you moved the mouse on a flat surface.
2. Modern optical mouse uses a light sensor.
3. 3D mouse uses motion detectors to detect movement through the air, not just on a flat surface.

Question 4

Describe 3 other positional devices.

Answer 4

1. A trackball is used by people who find using a mouse uncomfortable. The ball is moved by the fingers while the device stays still.
2. A laptop touchpad is used when you don’t want to plug in extra devices into the laptop.
3. A game console gives 3D control over a computer game.

Question 5

3 advantages of entering data into the computer using a keyboard

Answer 5

1. Easy and convenient to use
2. Included free with a typical computer
3. Can be used for a wide range of tasks

Question 6

3 disadvantages of entering data into the computer using a keyboard

Answer 6

1. Slow to input data compared to automatic input devices (keyboards are manual devices)
2. Easy to make mistakes
3. Tiring to use

Question 7

Touch screens

Answer 7

1. An output device that displays information for the user
2. An input device that lets the user make selections from the display, including selecting a character to enter
3. Detect the presence of your finger and send a positional signal to the processor
4. Mobile devices, ATM machines, supermarket checkouts

Question 8

Resistive screen

Answer 8

1. Uses multiple layers of material that conduct electricity
2. When the screen is touched, the top layer pushes into the bottom layer
3. The electric current changes and location of “touch” is found

Question 9

Capacitive screen

Answer 9

• ELECTRICAL charge is spread across the screen
• sensors are located around the screen
• when finger touches the screen, the charge is transferred to the user, as it is affected by the conductivity of another object
• coordinates of touch is determined

Question 10

Infra-red screen

Answer 10

1. Has 2 sets of invisible beams projected at right angles across the screen, making a grid
2. A finger/stylus will break the beams and sensors detect where the screen has been touched
3. Position of “touch” is calculated

Question 11

Interactive whiteboards

Answer 11

1. A large touch screen. The screen displays content for everyone in the room to see.
2. The board can be touched so that the display can be changed
3. Can write directly onto the screen with a special pen
4. Schools, meeting, training rooms

Question 12

Digital cameras - application

Answer 12

Photography studios, crime scene investigations, mobile devices

Question 13

Microphones - application

Answer 13

Voice recognition, mobile devices, recording studios, live performances

Question 14

Barcode readers - application

Answer 14

Supermarket checkouts, library system, airport check-ins

Question 15

3 advantages of using a barcode reader

Answer 15

1. It is faster and there is less chance of an error than typing the code by hand.
2. The code can be input using magnetism or electricity, but preparing these formats needs special equipment.
3. A barcode can be printed by an ordinary B&W printer.

Question 16

2 disadvantages of using a barcode reader

Answer 16

1. It can only do one task - read barcodes - unlike a keyboard.
2. It must be bought separately (not part of an ordinary computer).

Question 17

Quick Response (QR) code readers - application

Answer 17

Magazine adverts, business cards, companies track products in warehouses/factories

Question 18

Difference between 2D and 3D

Answer 18

2D means there are length and height while 3D means there length, height and width.

Question 19

3 types of document scanners

Application

Answer 19

1. Flat-bed scanners have a glass surface which you put the document face down on. You then close the lid.
2. Roller scanners feed the document through.
3. Hand-held scanners can be moved or rolled across a document.
   Application: reading passports

Question 20

Optical Mark Recognition (OMR)

Answer 20

1. OMR scanner detects the presence of marks on a piece of paper/card. Data is passed to processor to say whether a mark is present or not at each position.
2. A form, clearly showing the options people can choose from, must be printed in advance.
3. Multiple choice exams, surveys, votes in elections

Question 21

Optical Character Recognition (OCR)

Answer 21

1. OCR reader scans text. Software linked to scanner can interpret the shape of the letters and make an editable text file.
2. OCR scanning is much quicker than typing but it can only read text that already exists. You cannot use it to write a new document.
3. Scanning of passports at airports, license plate scanning on highways, meter reading at homes

Question 22

4 uses of 3D scanners

Answer 22

1. Industrial - to scan an object so a copy of it can be made
2. Medical - to scan a part of the patient’s body to find damage or disease
3. Research and archaeology - to scan a location to find out more about it
4. Cultural and entertainment - to record works of art, or to make realistic video games
   eg. Computed tomographic (CT) scanners, museums, aerospace manufacturing and design

Question 23

Sensors

Answer 23

1. Automatic input devices.
2. A sensor is designed to measure one feature of the environment (any area outside the computer).
3. The measurement is converted to a digital value and input to the processor.

Question 24

Light sensor

Answer 24

1. Street lighting - Turn on street lights when it gets dark
2. Greenhouse - Ensures correct lighting conditions for growth of plants
3. Automatic doors - Detects a person when light beam is broken and opens doors

Question 25

Temperature sensor

Answer 25

1. Control a central heating system
2. Oven
3. Monitor/control the temperature in a greenhouse

Question 26

Magnetic field sensor

Answer 26

1. Used in anti-lock braking systems in cars
2. Used in alarm gates to detect shoplifters
3. Used in smartphones’ compasses to detect where North is so it can tell you which direction you are facing on the surface of the Earth

Question 27

Gas sensor

Answer 27

1. Monitor pollution levels in a river or in the air
2. Fish tank/aquarium
3. Check for gas leaks in a factory

Question 28

Pressure sensor

Answer 28

1. Used in robotic vacuum cleaners to detect collision
2. Used in car alarms to detect suspicious changes in air pressure; and burglar alarm system
3. Traffic light control

Question 29

Moisture and humidity sensors

Answer 29

1. Monitor/control the humidity levels in the air in a greenhouse
2. Used for weather prediction
3. Used in clothes dryers

Question 30

pH sensor

Answer 30

1. Detect medical conditions, eg. oxygen starvation (pH of blood will decrease)
2. Monitor pH levels during fermentation of alcohol in a brewery
3. Measure water acidity at water treatment works

Question 31

Motion sensor

Answer 31

1. Detect intruders in a burglar alarm system when the beam of infra-red light is broken
2. Automatic doors
3. Detect the motion of a hand-held game controller that can be moved around in the air

Question 32

Why are control systems useful?

Answer 32

1. A computer can monitor a process constantly without getting bored/tired.
2. Computers can measure a wide range of conditions very accurately.
3. Computers can go to places where it is hard for humans to go, eg. under the sea or on Mars.
4. Computers can react quickly in an emergency situation.

Question 33

Examples of systems that use sensors

Answer 33

1. Manufacture - in factories to make cars
2. Warnings - fire or flood warning systems
3. Research - computer can take readings and measurements and record them for research, provides continuous accurate measurements all day long, can take measurements in places humans cannot go (eg. Mars Rovers project)
4. Household uses - washing machines, central heating
5. Transport - autopilot (aeroplanes, ships), self-driving cars

Question 34

Benefits and drawbacks of resistive screens

Answer 34

Benefits:
1. Cheap to manufacture
2. Can use stylus/finger/gloved finger/pen
Drawbacks:
1. Poor visibility in sunlight
2. Vulnerable to scratching 
3. Wears through time

Question 35

Benefits and drawbacks of capacitive screens

Answer 35

Benefits:
1. Good visibility in sunlight
2. Very durable surface
Drawbacks:
1. Glass screen will shatter on impact
2. Cannot use when wearing (standard) gloves

Question 36

Benefits and drawbacks of infra-red screens

Answer 36

Benefits:
1. Good durability
2. Can use stylus/finger/gloved finger/pen
Drawbacks:
1. Expensive to manufacture
2. Glass screen will shatter on impact 
3. Sensitive to dust/dirt

Question 37

Describe the operation of a 2D scanner

Answer 37

• (Scanner) shines a light onto the surface of a document
• Reflected light is captured
• Uses mirrors and lenses
• Captured image is converted into a digital file
• Produces a 2D digital image

Question 38

Describe the operation of a 3D scanner

Answer 38

• Scanners shines a laser (or light) over the surface of a 3D object
• Records measurements of the dimensions of the object
• Measurements are converted to digital file
• Produces a 3D digital model