Computer Science 2210 By Sajid Ali Imam
Input Devices
Every computer system receives commands and data, from the real world, via input
devices
Input devices converts inputs into digital data which can be processed
For conventional computer systems, such as desktop computers and laptops, the most
common input devices are the mouse and the keyboard
There are a wide range of input devices used in more specialist computer systems such
as scanners and sensors
Exam Tip
The exam board has limited the number of devices you may be asked about to eight -
keyboard, optical mouse, microphone, barcode scanner, digital camera, QR code
scanner, touch screen (resistive, capacitive and infra-red), 2D and 3D scanners
If you're asked to list some input devices, check you're not listing one included in the
question as you won't get a mark for this
You won’t be asked how they technically work but may be asked what each device does,
why it does it and when it may be used
Barcode Scanner
Diagram of a barcode being scanned by a handheld barcode scanner
Barcodes are a series of black and white bars which represent a code
A barcode reader shines a red laser at the barcode to read the data it represents
The light from the white lines is reflected back
Black lines absorb the light so less is reflected
The different levels of reflection are converted into a binary value which can be processed
by a microprocessor
A barcode reader can be handheld or built into a larger machine such as a self-service
checkout at a supermarket
Barcodes can be used in many ways such as identifying a product being sold or tracking a
package through the delivery process
Benefits include faster checkouts, automated stock control, less chance of error due to
manual entry of data, and more detailed tracking information
Computer Science 2210 By Sajid Ali Imam
Worked example
How are barcodes used in supermarkets to manage stock control?
- When a customer purchases an item, its barcode is scanned in at the checkout [1]
- The barcode reader sends the digital code for the product to the stock database where it is
removed from the stock inventory [1]
- This means the number of items of stock is always accurate and up to date [1]
- and the supermarket staff can reorder items quickly when stock is low [1]
Digital Camera
A digital camera works by capturing light and converting it into a digital image
Light enters the camera through the lens, it reaches an image sensor where it is split into
millions of pixels (small squares). Each pixel measures light intensity which is converted
into binary and represents a colour.
Digital cameras are integrated into smartphones, used in security systems and
by professional photographers to create high quality digital images
An advantage of digital cameras is they show a preview of the image
They also instantly create an image which can then be
easily duplicated and transmitted via bluetooth or Wi-Fi
Software can be used to edit digital photos, for example applying a filter or retouching a
photo
Keyboard
A keyboard is the most common device used for text-based data input
They are connected either by a USB cable or wirelessly to the computer system
They are built into laptops.
Smartphones and tablets have virtual keyboards
Each key on a keyboard has a peg underneath it which makes contact with a conducting
membrane. This is then converted into an electrical signal to transmit a unique character
code
Computer Science 2210 By Sajid Ali Imam
Microphone
A computer microphone works by converting sound waves into electrical signals that can
be processed by the computer.
They can capture any real-world sound and convert it into digital data which can be stored,
duplicated or modified
The microphone has a diaphragm that vibrates in response to sound waves. These
vibrations are then converted into electrical signals by a coil of wire attached to the back of
the diaphragm. Changes in the signal are recorded by a microprocessor using a analogue to
digital converter
Microphones are used to record music, telephone calls, communicate online and dictation
Optical Mouse
A mouse use a laser to detect and track movement, this is then processed by a
microprocessor which interprets the movement and replicates it when moving a virtual
cursor on-screen
Items can be selected or moved using the left mouse button, whilst the right button usually
displays additional menus
They can be wired or wireless
They are used to control the cursor in a Graphical User Interface (GUIs)
They are simple to use and provide the user with an intuitive way to navigate the computer
They are reliable due to no moving parts
Computer Science 2210 By Sajid Ali Imam
QR code scanner
Diagram of a QR code being scanned by a mobile device
A QR code is a visual representation of data using black and white squares
QR codes can represent over 7000 digits whereas a barcode represents up to 30 digits
QR codes are scanned by a camera (often on a mobile device)
A piece of software convert the squares into binary data
QR codes often link to a website where more information can be found
They can also be used to advertise products, share contact details, provide promotional
codes, train tickets, and event tickets
Worked example
Describe how festival organisers could make use of QR codes and QR code scanners [4]
Any 4 of:
- Festival e-tickets could be in the form of a QR code [1]
- QR scanners could scan them on entry to the festival [1]
- QR codes could be used to advertise the festival [1]
- QR codes could be used to link to the festival website [1]
- QR codes could be used to provide information during the festival [1]
Touchscreen
A touchscreen can be classed as both an input device and an output device
The exam board will refer to a touchscreen as an input device.
Computer Science 2210 By Sajid Ali Imam
Types of touch screen
Type How it works Benefits/drawbacks Uses
Resistive screen Resistive screens + Cheap to produce.
consist of two
conductive layers. + Resistant to Used in cash
The top layer is surface contaminants machines,
flexible. When the information kiosks,
screen is touched the + Can be activated medical equipment
two layers connect, with nearly every
completing a circuit object (stylus, finger,
gloved hand)
Infra-red screens LEDs shine infrared + Excellent image
light across a screen quality,
forming a matrix.
When the screen is + high precision
touched the beams Tablets, laptops,
are interrupted + durable smartphones
+ allows for multiple
touches at the same
time
- Requires a bare
finger or stylus for
activation
Computer Science 2210 By Sajid Ali Imam
Capacitive screens Made up of a +Excellent image Large scale
protective layer, a quality commercial displays
transparent
conductive layer and +Unlimited touch-life Information kiosks
a glass substrate.
Touching the screen +Scale well Medical equipment
changes the
- Sensitive
electrostatic field of
to interference from
the conductive layer
light, water, snow
2D and 3D scanners
A two-dimensional (or flat-bed) scanner shines a strip of light over a document. Reflected
light is measured for each pixel. This data is converted into binary data so the document can
be digitally recreated
A three- dimensional laser scanner shines a light over an object. The geometry and
dimensions are recorded so the object can be recreated digitally
The digital 3D model can be modified using specialist software
A 3D printer could then print out the model
2D scanners can be used for creating digital versions of documents or photographs
Reading passports at airports
3D scanners can be used to create 3D models for use with computer-aided design (CAD)
software
Creating replicas with 3D printers
Typical uses of 3D scanners and printers are dentistry, product development, medical
A cheap and quick way of creating a digital representation of both 2D and 3D objects so
they can be manipulated, stored, transmitted or copied
Computer Science 2210 By Sajid Ali Imam
Summary of input device uses and benefits
Device Example of Uses Benefits
Barcode scanner Checkouts, parcel delivery Faster checkout, less errors,
detailed stock/tracking
information
QR code scanner Advertising products, linking - Can hold more
to websites, e-tickets information than a
barcode
- Can be scanned using a
camera on a mobile
device (smartphone)
2D and 3D scanners Scan documents, photos and Converts 2D and 3D objects
objects into digital data which is
easier and quicker to
transmit/duplicate or
manipulate
Digital camera Smartphones, professional Instant preview and image
photography, security
systems
Keyboard Entering text Universal, easy to use
Mouse - Navigating a GUI Intuitive
- Making selections and
entering commands
Microphone - Recording real-world
sound
- Musical recordings
Computer Science 2210 By Sajid Ali Imam
- Telephone calls
- Dictation
Touchscreen - Entering text and - Can be durable
commands on mobile
devices (tablet, - Good image quality
smartphone)
- Intuitive/easy to use
- Cash machines
- Interactive
advertisements
- Information screens
