Hardware - Input + Output devices Flashcards
1
Q
what is an input device
A
any device that allows you to pass information from the outside world into a computer system
2
Q
how does a barcode scanner work
A
- red laser light shone at a barcode to illuminate it
- white lines reflect back
- black lines absorb some light and reflect less
- sensors in scanner detect the pattern of strong and weak reflections
- reflection strength from each lie is interpreted by a microprocessor and converted into a binary value
3
Q
what 3 uses for barcode scanners used for
A
- scanning goods at supermarket checkout
- checking library books in and out
- tracking packages out for delivery
4
Q
4
why are barcodes required
A
- faster checkout queues
- reduces errors caused by manual input
- more detailed tracking information
- automatic stock control
5
Q
what does a QR code scanner do
A
- QR code is read by using a camera, commonly on a mobile device
- 3 large squares in the corners are used for alignment
- smaller black and white quares reflect or absorb light
- software on device converts each pixel into a binary value to process the image
6
Q
what does a QR code commonly contain
A
a hyperlink to an online file
7
Q
what are QR codes typically used for
A
- advertising products
- quick links to websites
- sharing contact details instantly - no need to type
8
Q
why are QR codes required
A
- hold far more information than a traditional barcode
- much quicker access
9
Q
how do 2D scanners work
A
- 2D (flatbed) scanner shines a strip of light onto a document/ photo
- strip moves over whole document , reflected light is captured using mirrors + lenses and the light intensity is measured per pixel
- information is converted into a **digital file(( to produce a digital image of the original document
10
Q
how do 3D scanners work
A
- shine a laser over the surface of an object
- records the geometry and dimensions of the object to produce a digital file
- from this file a digital model is created
- parts can then be printed using a 3D printer
11
Q
what are 2 things 2D canners are used for
A
- creating digital versions of documents and photographs
- reading passports at airports
12
Q
what are 4 things 3D scanners used for
A
- creating 3D models for use with computer-aided design (CAD)
- Dentistry
- product development
- quality inspection and research
13
Q
why are scanners required
A
simple, cheap and effective way of generating a digital representation of 2D or 3D objects for further manipulation
14
Q
how does a digital camera work
A
- as light enters lens, it falls onto the sensor which is divided up into millions of individual squares or pixels
- each pixel measures the light intensity
- this value is converted into digital data as a pixel with a single binary colour value
- image can be stored as a file on flash memory
- or a microprocessor within camera reassembles image on a screen using each pixel’s information
15
Q
what are digital cameras typically used for
A
- integrated into smartphones
- security and surveillance cameras
16
Q
why are digital cameras required
A
- camera on phone is smaller, lighter - largely replaces traditional, film-base cameras - chunky
- instant photographs - very accessible + quick
- easily transmitted via Wi-Fi, Bluetooth, etc.
- embedded editing software
17
Q
how do keyboards work
A
- when key is pressed , a peg under the key is pressed into a springy layer to make contact with a conducting membrane
18
Q
how do optical mice work
A
- use red LED and a Sensor to determine movement
- analysed by digital signal processor to cream same movement
19
Q
how do microphones work
A
- uses diaphragm to vibrate in response to sound
- vibrations cause a coil to move around a magnet –> creates changes in electromagnetic field
- changes detected + recorded by processor** using an analogue to digital converter (ADC)
20
Q
what device are touch screens
A
both input and output
21
Q
what are the 3 types of touchscreen
A
- resistive
- Infra-red
- Capacitive
22
Q
what are resistive screen made of
A
- layer of conductive polyester + layer of conductive glass
- 2 layers separated by insulating layer
- when pressed - 2 conducting layers make contact –> complete circuit
- position where touched is calculated by microprocessor
23
Q
where are resistive touch screens used
A
- ATM screens
- medical equipment - users often wear gloves
24
Q
how to Infra-red screens work
A
- LEDs chine infra-red light across the screen from top and sides
- infra-red rays form a grid
- when touched, infra-red beam interrupted
- microprocessor calculates coordinates
25
where are infra-red screens most commonly used
staff tills in fast food outlets
26
how does capacitive screens work
- made up of **glass layers**
- **bottom surface of upper layer** and **top surface of lower layer** coated in **perpendicular lines** of **transparent conductive material** forming a **grid**
- screen behaves like a **capacitor** - **stores electrical energy**
- when touched - **change in electrical field** in that position
- **microprocessor** calculated position where **field changes**
27
what are the advantages of capacitive screens
can be touched in **multiple places simultaneously**
28
where are capacitive screens used
- smartphones
29
explain why you cannot control the capacitive screen when wearing gloves
- gloves are an **insulative layer**
- prevents **electric field being changed** and **sensed** by the screen
30
what device are screens with no touch function
output device
31
what are the 2 types of output screens
- Liquid crystal display (LCD)
- Light emitting diode (LED)
32
how to LCD's work
- made from millions of **pixels**
- each pixel is a **separate red, blue, green light** that can be **switched on or off electronically** using **liquid crystals to rotate polarised light**
- pixels are switched on or off **rapidly** to make a **moving colour picture**
- a **special fluorescent lamp required** to provide necessary **backlight**
33
how to LEDs work and what are the adv compared to LCD
- screen uses **light from LEDs** to produce a **brighter backlight** almost instantly --> replacing need for **additional fluorescent lamp** in LCD
34
where are LEDs often used and how are they made
- big sport **stadiums / concerts**
- made of **many smaller screens** in a cluster
35
what are the 2 types of projectors
- Digital light processing (DLP) projectors
- Liquid crystal display (LCD) projectors
36
how to DLP projectors work
- millions of **micro-mirors** arrand in a **grid on a small microchip(( within the projector
- shining **white light** through **colour filters* alters colour
- **angle** of mirror alters **colour intensity**
37
how to LCD projectors work
- **3 mirror filters** to separate image into **red , green, blue wavelengths**
- **3 images combined** using a **prism**
- produces **full colour image** which then **passes through lens** and projected on screen
38
what are the adv of DLP
- higher contrast + definition
- smoother video
- smaller
39
what are the adv of LCD
- cheaper
- quieter
- less power and heat output
40
what are the 2 types of printers
inkjet printers
laser printers
41
how to inkjet printers work
- use **liquid ink** reservoirs, forcing droplets through fine nozzle
42
what are inkjet printers best used for
- small print runs
- high resolution colour photos, esp when specialist coated photo paper used
43
how do laser printers work
- **dry ink** in powder form caller **toner** that is **electrostically charged**
- printer creates **mirror image** of the printed
