Table of Contents
Easy Level Questions:
What are the uses of interactive whiteboards (as part of input and output devices)?
– Interactive whiteboards allow computer images to be displayed using a digital projector.
– They allow users to write on the whiteboard and the text/images created can then be stored in a computer memory.
– Any image projected onto the screen can be annotated or even changed and the annotated version can then be saved for later use.
How does dot-matrix printer work (as part of input and output devices)?
– printers use a matrix of pins which strike an inked ribbon (either black or up to 4 coloured) to produce characters in a matrix on the paper, e.g.
The advantages of using OLED when compared to older LED technology includes what?
– they allow for very thin and very flexible screens which are very light weight
– they produce a much brighter light than LEDs
– they don’t require any form of back-lighting
– they allow for a much larger field of view.
How does OLED work (as part of input and output devices)?
– Newer monitors and televisions use organic light-emitting diodes (OLEDs).
– These produce their own light and therefore don’t need any form of back-lighting.
What are the advantages and disadvantages of dot-matrix printer (as part of input and output devices)?
Pros:
– not adversly affected by damp or dirty/dusty atmospheres
– allows use of multi-part stationary (i.e carbon copies)
– allows use of continuous/fan-folded stationery
Cons:
– relatively expensive to buy
– poor print quality
– very noisy and very slow at printing
What are the advantages and disadvantages of inkjet printer?
Pros:
– high quality of printing
– very suitable for printing photos
– inexpensive to buy printer
Cons:
– ink is expensive to buy and quickly runs out on a large print run
– usually have small paper trays
– can be noisy in operation compared to laser printer
What are the advantages and disadvantages of laser printer?
Pros:
– very high quality of printing
– relatively inexpensive to buy printer
– large toner cartridges and large paper trays
– very fast printing of multiple documents
Cons:
– can be expensive to maintain
– produce health hazards such as ozone or toner particles in the air
Digital cameras contain a microprocessor that does what?
– adjusts shutter speed
– focuses
– operates the flash
– adjusts the aperture
– removes ‘red eye’
– reduces hand shake, and so on
Medium Level Questions:
What are the advantages of barcode scanners to customers?
– faster checkouts
– less chance of errors
– get an itemised bill
– cost savings can be passed on to customer
– better tracking of ‘sell by dates’
What are the advantages of barcode scanners to managers?
– easier and faster to alter prices
– give instantaneous and comprehensive sales trends
– no need to price each item (saves time and money)
– allows automatic stock control
– can check customer’s buying habits more easily
What are the uses of barcode?
– Barcodes are used in supermarkets to find prices of goods and to enable automatic stock control.
– They are also used extensively in library systems to track the whereabouts of books.
CT scanners are used for what?
– To produce 3D image of a solid object.
How does CT scanners work (as part of input and output devices)?
– Tomography technology splits up the object into a number of very thin ‘slices’.
– They tend to use X-rays, radio waves or gamma imaging methods.
– The resultant image allows a solid object to be stored as a series of digital values representing each ‘slice’.
What are the applications of magnetic field sensor?
– any application where detection of changes in a magnetic field is required (like in cell phones, CD players, etc
– used in anti-locking breaking system in motor vehicles
What are the application of pH sensors?
– monitor/control acidity/alkalinity levels in the soil in a greenhouse
– pollution/environmental monitoring in rivers
What are the applications of gas (O2 and CO2) sensors?
– monitor pollution levels in a river or in the air
– measure O2 and CO2 levels in a greenhouse
– check for CO2 leaks in a power station
What are the application of acoustic/sound sensors?
– pick up noise levels in a burglar alarm system
– detect the noise of liquids dripping in a pipe
What are the application of pressure sensor?
– detect intruders in a burglar alarm system
– weigh things
– monitor/control a process where gas pressure is important
Mastery Level Questions:
What are the application of infra-red/motion sensors (as part of input and output devices)?
– turn on the windscreen wipers on a car automatically
– detect intruders in a burglar alarm system
– count people entering/leaving a building
What are the applications of light sensors?
– switch street lighting on at night and off during the day
– monitor/control light levels in a greenhouse
– automatically switch on a car’s headlights when it gets dark
Application of moisture/humidity sensor?
– control/monitor the moisture levels in the soil of a greenhouse
– control/monitor the humidity levels in the air in a greenhouse
– monitor dampness levels in an industrial appplication
Application of temperature sensor?
– control a central heating system
– control/monitor a chemical process
– control/monitor the temperature in a greenhouse
What are the cons of resistive touchscreens?
– screen visibility is poor in strong sunlight
– it doesn’t permit multi-touch capability
– the screen durability is only fair; it is vulnerable to scratched and the screen wears out through time
What are the pros of resistive touchscreens?
– it is relatively inexpensive technology
– it is possible to use bare fingers, gloved fingers or a stylus to carry out an input operation
What are the cons of infra-red touchscreens (both heat and optical)?
– it is relatively expensive technology
– heat-sensitive system only allows bare fingers to be used for input
– both systems have not so good screen visibility in strong sunlight
What are the pros of infra-red touchscreens (as part of input and output devices)?
– both systems allow multi-touch capabilities
– the optical system allows the use of bare fingers, gloved fingers or a stylus for input
– both systems have good screen durability, it take a major impact to break the glass
What are the cons of capacitive touchscreens?
– allows only the use of bare fingers as the form of input; although the latest screens permit a special stylus to be used
Pros of capacitive touchscreen?
– this is a medium cost technology
– screen visibility is good even in strong sunlight
– it permits multi-touch capability
– the screen is very durable; it takes a major impact to break the glass
What is the different names for gamma rays?
– gamma rays = SPECT = single photon emission computed tomography
What is the different name for radio frequencies and what is the use?
– radio frequencies = MRI = magnetic resonance imaging
What is the different name for X-rays and what is the use (as part of input and output devices)?
– X-rays = CT scanners = computerised tomography
How does LCD projectors work (as part of input and output devices)?
– Older technology than DLP
– A powerful beam of white light is generated from a bulb
– This beam of light is then sent to a group of chromaticcoated mirrors; these reflect the light back at different wavelengths
– When the white light hits the mirrors, the reflected light has wavelengths corresponding to red, green and blue
– These three different light pass through three LCD screens; these screens show the image to be projected as millions of pixels in grayscale
– When the coloured light passes through the LCD screens, a red, green and blue version of the grey image emerges
– Finally, the image passes through the projector lens onto the screen
How does digital light projectors work?
– Uses millions of micro mirrors
– the number of micro mirrors and the way they are arranged on the DLP chip determines the resolution of the image
– When the micro mirrors tilt towards the light source they are on
– When the micro mirrors tilt away from the light source they are off
– This creates a light or dark pixel on the projection screen
– A bright white light source passes through a colour filter on its way to the DLP chip
– White light splits into primary colours
What is the use of light projectors (as part of input and output devices)?
– Projectors are used to project computer output onto larger screens/interactive whiteboards
What are the two common types of light projectors?
– Digital Light Projector (DLP)
– LCD Projector
What CCFL and how does it work?
– Before LEDs, LCD monitors were backlit using CCFL
– CCFL uses two fluorescent tubes behind the LCD screen which supplies the light source
How does LCD monitor work with LEDs?
– LCD monitors are back lit using Light Emitting Diode (LED) because:
– LEDs reach their maximum brightness immediately
– LEDs sharpens image (higher resolution), CCFL has yellow tint
– LEDs improve colour image
– Monitors using LED are much thinner than CCFL
– LEDs consume very little power
What is LCD monitor?
– Front layer of monitor is made up of Liquid Crystal Display (LCD), these tiny diodes are grouped together in threes as pixels (LCD doesn’t emit any light)
How does loudspeaker/headphones work?
– Sound is produced by passing the digital data through a DAC then through amplifier and then emerges from loudspeaker
– Produced by voltage differences vibrating a cone in the speaker at different frequencies
What is the use of actuators?
– Used in many control applications involving sensors and devices (ADC and DAC)
What is the difference between 2D and 3D cutters?
– 3D cutters can recognise objects in x, y, z direction
– 3D laser cutters can cut; glass, crystal, metal, wood
How does 3D printer work (as part of input and output devices)?
– Built up layer by layer, using powdered resin, ceramic powder
– A design is made using Computer-aided Design (CAD)
What is 3D printer used for?
– Used for models of cars
– Produce solid objects that work
How does laser printer work?
1. Data from document sent to printer driver
2. Printer driver ensures data is in correct format
3. Check made by printer driver that chosen printer is available
4. Data is sent to printer, stored in a temporary memory (printer buffer)
5. Printing drum is given a positive charge; as the drum rotates, a laser beam is scanned across it removing the positive charge leaves negatively charged areas which match the text/image
6. Drum is then coated with positively charged toner, it only sticks to negatively charged parts of the drum
7. A negatively charged sheet is rolled over the drum
8. Toner on the drum now sticks to the paper to produce copy of page
9. Paper finally goes through a fuser (set of heated rollers); heat melts the ink so it is permanent
10. Discharge lamp removes all electric charge from the drum, ready to print next page
What is laser printers and how is it different from inkjet printers?
– Used to print flyers, high quality
– Use dry powder ink (toner) and static electricity to produce text and images
– Prints the whole page in one go
How does inkjet printer work?
1. Data from document sent to printer driver
2. Printer driver ensures data is in correct format
3. Check made by printer driver that chosen printer is available
4. Data is sent to printer, stored in a temporary memory (printer buffer)
5. Sheet of paper is fed; sensor detects if paper is available in paper tray
6. Print head moves across paper printing text/image, four ink colours sprayed in exact amount
7. Paper is advanced so next line is printed
8. Repeated until buffer is empty
9. Once it is done, printer send an interrupt to the processor (request for more data to be sent)
What are inkjet printers used for?
– Used to print one-off pictures and documents
Describe how control of street lighting use sensors?
– Light sensor sends data to the ADC
– Digitises data and sent to the microprocessor
-Microprocessor samples data every minute
– If data from sensor < value stored in memory:
– Signal sent from microprocessor to street lamp
– Lamp switched on
What are sensors?
– Devices which read or measure physical properties
– Data needs to be converted to digital
– Analogue to Digital Converter (ADC) converts physical values into digital
How does resistive touchscreen work?
– Upper layer of polyester, bottom layer of glass
– When the top polyester is touched, the top layer and bottom layer complete a circuit
– Signals are then sent out which are interpreted by a microprocessor, determine where screen was touched
How does infra-red optical touchscreen work?
– Uses glass as screen material
– Uses an array of sensors (grid form)
– Point of contact is based on which grid co-ordinate is touched
How does infra-red heat touchscreen work?
– Use glass as the screen material
– Needs warm object to carry an input operation
How does capacitive touchscreens work?
– Made up of many layers of glass
– Creating electric fields between glass plates in layers
– When top layer of glass is touched, electric current changes
– Co-ordinates where the screen was touched is determined by an on-board microprocessor
What is voice recognition?
– Voice recognition, voice is detected and converted into digital
How does microphone work?
– When a microphone picks up sound, a diaphragm vibrates producing an electric signal
– The signal goes to a sound card and is converted into digital values and stored in computer
What is a microphone used for?
– Used to input sound to a computer
Describe a trackball?
– Traditional; mechanical ball, connected by USB port
Describe a mouse?
– Modern type; red LEDs to detect movement
What are the different pointing devices?
– Mouse
– Trackball
Disadvantages of keyboards?
– Slow method
– Prone to errors
How does keyboards work?
– Connected to computer with a USB connection or by wireless connection
– Each character has an ASCII value and is converted into a digital signal
How does digital camera work?
– Controlled by microprocessor which automatically adjusts the shutter speed, focus the image, etc.
– Photo is captured when light passes through the lens onto a light sensitive cell
– Cell is made up of pixels
– Number of pixels determines size of the file
What are the advantages of QR code?
– Can hold more storage (7000 digits)
– No need for the user to write down website address
– QR codes can store website addresses
What is Quick Response (QR) code?
– Another type of barcode is the QR codes
– Made up of a matrix of filled in dark squares on a light background
How does barcode readers/scanners work?
– The left and right hand sides of the barcode are separate using guard bars
– Allows barcode to be scanned in any direction
– Barcode is read by a red laser or red LED
– Light is reflected back off the barcode; dark areas reflect little light which allows the bars to be read
– Reflected light is read by sensors (photoelectric cells)
– Pattern is generated which is converted to digital
What is a barcode?
– A barcode is a series of dark and light parallel lines of varying thicknesses
– The numbers 0 -9 are each represented by a unique series of lines
Describe the application of 2D Scanners at an Airport?
– Make use of (OCR) to produce digital images which represent the passport pages
– Text can be stored in ASCII format
– The 2D photograph in the passport is also scanned and stored as jpeg image
– The passenger’s face is also photographed using a digital camera and compared using face recognition software
– Key parts of the face are compared (distance between eyes, width of nose)
What is the real life application of three-dimensional scanner?
– The scanned images can be used in Computer Aided Design (CAD) or to a 3D printer to produce a working mode
How does three-dimensional scanner work?
– Scanners take images at several points, x, y and z (lasers, magnetic, white light)
What is three-dimensional scanners used for?
– 3D scanners can scan solid objects and produce a threedimensional image
What is Optical Character Recognition?
– Optical Character Recognition (OCR) is a software which converts scanned documents into a text file format
– If the original document was a photo/image, then the scanned image forms an image file such as JPEG
How does two dimensional scanner work?
– Document is placed on a glass panel
– A bright light illuminates the document
– A scan head moves across the document until the whole page is scanned. And image of the document is produced and sent to a lens using a series of mirrors
– The lens focuses the document image
– The focused image now falls onto a charge couple device (CCD) which consists of a numbers of integrated circuits
– Software produces a digital image from the electronic form
What is two dimensional scanners used for?
– Used to input hard-copy documents
– The image is converted into an electronic form which can be stored in the computer
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