Input Devices Flashcards
What is an input device?
Any device that allows you to pass information from the outside world into a computer system
How does a barcode scanner work?
It shines a red laser at a barcode to illuminate it.
White lines reflect the light back, whereas the black lines absorb the light
The strength of reflection is interpreted by a microprocessor and then converted into a binary value
When is a barcode scanner used?
Scanning goods at checkouts
Checking library books in and out
Tracking packages out for delivery
Why are barcode scanners needed?
Faster checkout queues
Reduces errors caused by manual input
More detailed tracking informaiton
Automatic stock control
How does a digital camera work?
Light enters the camera and falls onto a sensor
Each pixel in the sensor measures the light intensity
A microprocessor converts these values into digital data that represents colour values
When is a digital camera used?
Integrated into most smartphones
Proffesional photography
Security and surveillance systems
Why are digital cameras needed?
Largely replaced traditional, film-based cameras
Instant photographs (i.e. no development needed)
Digital photos can easily be transmitted via WiFi, Bluetooth etc
Embedded software can adjust photos
How does a keyboard work?
Each character on a keyboard has a corresponding character set value
Key presses are converted into a digital signal; this is what the computer interprets
When is a keyboard used?
Built into laptops
Connected to most desktop computers via USB/wireless
Tablets and smartphones use virtual keyboards
Why is a keyboard needed?
One of the most common forms of text-based data input
How does a microphone work?
Vibrations caused by sound waves cause a coil to move around a magnet, resulting in electrical field changes
These changes are converted by a microprocessor and an ADC into a digital representation of the sound
When is a microphone used?
Music recordings
Dictation
Radio, TV and films
Online communication
Why is a microphone needed?
Captures any real-world sound and stores it as a digital approximation
Digital sounds can be modified
Why does an optical mouse work?
Uses a red LED and a sensor to determine the movement of the mouse relative to the surface beneath
A microprocessor analyses both the speed and distance of the movement and it replicates this on-screen via a virtual cursor
Why is an optical mouse used?
Navigation and interaction with almost all elements of a graphical user interface (GUI)
Why is an optical mouse needed?
Easy interaction with applications and other GUI elements
More reliable as there are no moving parts, unlike mechanical mice
No need for a special surface (i.e. mouse mat)
How does a QR code scanner workd?
Reads using a camera (usually from a mobile device)
An app processes the image and converts the squares into readable data
When is a QR code used?
Advertising products
Quick links to websites so don’t need to type in a URL
Sharing contact details instantly
Why are QR codes needed?
Holds far more information than a traditional barcode
Barcode holds: 30 digits
QR code holds: 4296 characters (7089 digits)
How does a resistive touchscreen work?
Consists of two conductive layers
The two layers are separated by an insulating layer (gap/inert gas)
When the screen is pressed, the two layers contact and complete the circuit
What are the advantages of a resistive touchscreen?
Cheap to produce
Can be activated with any object (gloved finger, stylus etc)
Very resistant to surface contaminants
What is a disadvantage of a resistive touchscreen?
Lower image clarity and precision compared to other types
How does a capacitive touchscreen work?
LEDs shine infrared light across a screen, forming a matrix
When the screen is touched the beams are interrupted
How does a capacitive touchscreen work?
Composed of a protective layer, transparent conductive layer, glass substrate
Touching the screen with a barefinger/stylus changes the electrostatic field of the conductive layer
