Input devices Flashcards
Syallabus: 1.3.3
1
Q
Define
input device
A
Devices which are used to input data and instructions into a computer.
Input devices allow us to enter raw data into a computer. The computer processes the data and then produces outputs that we can understand using an output device. Input devices can be manual or automatic.
2
Q
How does a 2D scanner work and where may it be used?
A
- Mechanically scans illuminated surface of paper document with a single row of hundreds of light sensors
- Scanner computer digitises analogue signals, processes and sends to computer
- Flatbed scanner – paper document places on glass ‘platen’.
- Saved as image
- OCR software can convert images into text data which can be edited by a word processor
- May be used in offices to scan documents
3
Q
List some advantages and diadvantages of 2D scanners
A
Advantages:
- Flat-bed scanners are very accurate and can produce images with a far higher resolution than a digital camera
Disadvantages:
- Can produce very large image files which need a lot of computer memory to view and edit
4
Q
What is a 3D scanner, how does it work and where may it be used?
A
- A 3D scanner is a device that analyses a real-world object or environment to collect data on its shape and possibly its appearance (i.e. colour). The collected data can then be used to construct digital three-dimensional models.
- Contact scanners probe object
- Non-contact scanners use light or radiation, detects reflection or radiation passed through objects
- May be used by architects to scan scale models of projects
5
Q
List some advantages and disadvantages of 3D scanners
A
Advantages:
- industrial computed tomography scanning can be used to construct digital 3D models, applying non-destructive testing
Disadvantages:
- many limitations in the kind of objects that can be digitized
- optical technologies encounter many difficulties with shiny, mirroring or transparent objects
6
Q
How does a barcode scanner work and where may it be used?
A
- Barcodes consist of short parallel lines in contrasting colours and different thicknesses
- Reflected laser light detects differences in lines
- Combination of scanner hardware & software
- Processor and decoding software in scanner
- ID codes used to look up description & price in database
- Used for identification of items
- Commonly used in shops to scan items or airports to scan boarding passes
7
Q
List some advantages and disadvantages of barcode readers
A
Advantages:
- saves time (automatic inventory)
- are efficient in recording information
- durable
Disadvantages:
- cannot read damaged or obscured barcodes
8
Q
How does a digital camera work and where may it be used?
A
- Grid of light sensors that pick up optical image
- Computer scans analogue signal, digitises data and displays on monitor screen
- When user presses shutter button, shutter opens to let in light
- Stores data as image file in memory
9
Q
List some advantages and disadvantages of digital cameras
A
Advantages:
- No cost to purchase and process film
- Display acts as viewfinder
- No processing delay: can view and delete immediately
- Easier and quicker to edit
- Easily sent over network
Disadvantages:
- Uses a lot of power
- Small handheld digital cameras cannot store many photos.
- A corrupted memory card may result in lost photos.
- Cost - top specification digital cameras can be far more expensive than their equivalent roll film cameras
10
Q
How does a keyboard work and where may it be used?
A
- A user enters values and commands into a computer by pressing keys on a keyboard
- A standard keyboard each key has a value printed on it
- Users of English usually type on a QWERTY keyboard, named from the first 6 letters on the first row
- A concept keyboard consists of rectangular grid of keys. A flat overlay sheet covers the keyboard. It has a suitable picture, symbol or word for each key. Often used in restaurants.
- A numeric keyboard: A rectangular block of keys with the numerals 0 to 9. Can be used for inputting PINs when we pay by credit card, on mobile phones, or on keyboards next to the QWERTY layout.
11
Q
List some advantages and disadvantages of keyboards
A
Advantages:
- simple, familiar, reliable technology (typewriters used the same QWERTY layout)
Disadvantages:
- It is slower as human operator takes more time in thinking and typing.
- Only one letter can be typed at a time.
- Slow compared with devices for automatic data capture.
- Prone to vandalism in public locations
12
Q
How does a mouse work and where may it be used?
A
- Allows user to point by moving a cursor
- User selects items by clicking switch buttons on mouse
- A mechanical mouse has a small ball underneath that can roll over a flat surface. The mouse detects and converts the rotations of the ball in two dimensions into digital signals.
- An optical mouse has no moving parts, detects movement by changes in reflected light
- Used with a graphical user interface (GUI)
13
Q
List some advantages and disadvantages of using a mouse
A
Advantages:
- Fast method on inputting commands, feels natural
- Moves the cursor faster than the arrow keys of keyboard
Disadvantages:
- Needs flat surface on which to operate, can be easily vandalised
- Hard to use by people with physical disabilities
- Not always suitable to carry around, especially with PCs
- Picks up dust and dirt easily - ball may become stuck
- Textual data can’t be input
14
Q
How does a touch screen work and where may it be used?
A
- Screen is sensitive to the touch of a finger or stylus
- Three types of systems to recognize touch: resistive, capacitive, and surface acoustic wave
- Resistive system consists of glass panel covered with a conductive and a resistive metallic layer. When the user touches the screen and the layers make contact the electric current running through the layers changes. The change in the electric field is used to calculate where the screen was touched.
- Capacitive system has a layer storing electrical charge placed on monitor’s glass panel. Charge is transferred to user’s finger, and the charge decrease is detected and used to calculate where the screen was touched.
- Surface acoustic wave system consists of two transducers (one receiving, one sending) placed along the x & y axes of the monitor’s glass panel, along with reflectors to reflect an electrical signal sent between the transducers. The receiving transducer can tell if the signal was disturbed by touch.
- Used in phones, portable gaming consoles, Point-Of-Sale terminals, tourist information kiosks and systems to find out about public transport.
15
Q
List some advantages and disadvantages of touch screens
A
Advantages:
- Difficult to vandalize
- Don’t need separate keyboards or mice which can be stolen
- Can be made reasonably weatherproof
- Users need no previous computer knowledge to be able to use them, feels intuitive
- Less prone to malfunction due to dust and dirt
- Combines output device (screen) with input device so reduced space requirements
- Makes use of finger gestures, such as pinch to zoom
Disadvantages:
- People with disabilities may find them difficult to use
- Not suitable for inputing large amounts of data
- Long periods of usage can be tiring
- Generally more expensive
