2.1 Input devices and their uses
An input device is hardware used to enter data or instructions into a computer.
Keyboard
A keyboard is one of the most common input devices. When a key is pressed, it produces a digital signal that the computer interprets.
Uses:
entering text into word-processing software
entering numbers into spreadsheets
typing commands
Advantages:
easy and familiar to most users
fast for entering text
allows the user to check data while typing
Disadvantages:
slower than direct data entry methods
typing errors can occur
frequent use can contribute to repetitive strain injury (RSI)
An ergonomic keyboard is designed to provide better support for the hands and wrists.
Numeric keypad
A numeric keypad is mainly used for entering numbers.
Uses:
ATMs for entering a PIN or amount
Chip and PIN systems
entering numerical data into spreadsheets
POS terminals when a barcode cannot be read
Advantages:
quicker than a normal keyboard for numerical data
usually small and easy to use
Disadvantages:
small keys can make entry difficult
number arrangements may differ between devices
Pointing devices
Mouse
A mouse controls a pointer on the screen.
It can be used to:
select icons and menu options
open and close programs
move or delete files
edit images
scroll through documents
Modern mice are often optical or wireless.
Advantages:
quick way of selecting options
easy to navigate around software and websites
Disadvantages:
needs a suitable surface
may be difficult for users with limited hand or wrist movement
Touchpad
A touchpad is commonly built into a laptop. The user moves a finger across the pad to control the pointer.
Advantages:
no separate mouse is required
useful when there is little desk space
Disadvantages:
pointer can be harder to control than with a mouse
operations such as drag-and-drop can be more difficult
Trackerball
A trackerball remains stationary while the user rotates a ball to move the pointer.
Uses include:
alternative to a mouse for users with RSI
industrial control rooms
controls in some cars
Advantages:
needs little desk space
can be easier for users with limited hand movement
accurate pointer positioning
Disadvantage:
less common, so users may need practice or training
Remote control
A remote control usually sends infrared signals to another device.
Uses:
televisions
DVD/Blu-ray players
multimedia systems
industrial machinery
Advantage:
equipment can be operated from a distance, which can be especially useful in hazardous environments.
Disadvantages:
the signal can be blocked
may be difficult for people with limited hand movement
Joystick and driving wheel
Joystick
A joystick controls movement by moving a stick and using buttons.
Uses:
computer games
flight and other simulators
Advantage:
More realistic than a keyboard for certain applications.
Disadvantage:
Pointer control can be less accurate than with a mouse.
Driving wheel
A driving wheel imitates the controls of a real vehicle. It may include pedals for acceleration and braking.
Uses:
racing games
driving simulators
Advantage:
Provides more natural and realistic steering.
Disadvantage:
Can be expensive compared with simpler input devices.
Touch screen
A touch screen lets the user select an option by touching an icon or button directly on the screen.
Uses:
ATMs
self-service tills
smartphones and tablets
information systems
interactive whiteboards
satellite navigation systems
Advantages:
easy to use
quick for selecting options
little or no training required
Disadvantages:
limited number of options can be displayed
repeated use can cause strain
screens become dirty through frequent touching
A touch screen can act as both an input and an output device.
Scanner
A scanner converts information on hard copy, such as photographs or documents, into a computer-readable image.
A flatbed scanner is a common example.
Uses:
scanning documents
scanning photographs
archiving old or valuable documents
scanning text for use with OCR
Advantages:
scanned images can be stored and edited
damaged photographs can sometimes be improved using software
OCR can avoid retyping an entire document
Disadvantages:
image quality depends on scanner resolution
high-resolution or colour scans can take longer
Digital camera
A digital camera stores photographs digitally, usually on solid-state memory.
Images can be transferred to a computer using:
a memory card
USB
Wi-Fi or Bluetooth
Uses:
photography
recording images for computer applications
vehicle reversing systems
creating virtual-reality tours
Advantages:
photographs are easy to transfer to a computer
no film needs to be developed
memory cards can hold many photographs
Disadvantages:
high-quality images can require a lot of storage
users need some computer knowledge to transfer and edit photographs
Microphone
A microphone is used to input sound.
Sound waves are converted into an electrical signal. Since this signal is analogue, it must be converted into digital form before being stored or processed by a computer.
Uses:
recording speech or music
voice-recognition software
voice commands
video conferencing and VoIP
sound detection in alarm systems
Advantages:
speech can be entered faster than typing
enables hands-free voice control
Disadvantages:
sound files can require considerable storage space
voice-recognition software may misunderstand words
Sensors
A sensor measures a physical quantity and sends the measurement to a computer.
Common sensors include:
| Sensor | Example use |
|---|
| Temperature | ovens, central heating, greenhouses |
| Pressure | alarm systems, washing machines |
| Light | automatic doors, street lighting |
| Sound | burglar alarms |
| Humidity/moisture | greenhouses, environmental monitoring |
| pH | chemical processes |
Most sensors produce analogue data, so an ADC (Analogue to Digital Converter) is needed before the computer can process the data.
Simple control system
Sensor → ADC → Computer → Output/control
Advantages of sensors:
measurements can be more accurate than human readings
continuous monitoring is possible
systems can operate automatically
Disadvantages:
faulty sensors can produce incorrect readings
analogue sensor data requires conversion using an ADC
Light pen
A light pen detects changes in light from a screen and can be used to select or draw directly on it.
Uses:
selecting items
drawing with CAD software
Advantages:
small
easy to use
accurate for selecting items
Disadvantages:
mainly works with CRT monitors
now considered dated technology
2.2 Direct data entry (DDE) devices
Direct data entry (DDE) devices enter data into a computer with little or no human involvement.
For example, with a barcode reader, the operator simply points the reader at the barcode; the data is transferred automatically.
Card readers
Magnetic stripe reader
A magnetic stripe reader reads information stored on the magnetic stripe of a card.
Uses:
debit/credit cards
access to hotel rooms or secure buildings
Advantages:
fast
avoids typing errors
data is not directly readable by people
Disadvantages:
magnetic stripes can be damaged
card must be close to or in contact with the reader
Contactless card reader
Contactless cards contain a chip that communicates with the reader using radio waves.
The card is held close to the terminal and the payment is processed without entering a PIN for suitable transactions.
Advantages:
very fast payment
no PIN typing errors
transaction information is protected
Disadvantages:
transactions are normally limited in value
unauthorised payments are a potential security concern
Chip and PIN reader
The card is inserted into the reader and:
the chip is read
the user enters a PIN
the entered PIN is checked
Advantage:
More secure than contactless payment because the correct PIN is required.
Disadvantage:
A user must ensure that nobody sees their PIN.
RFID readers
RFID (Radio Frequency Identification) uses radio waves to read information stored on a tag.
An RFID tag contains:
a microchip
an antenna
The tag may be read from several metres away in some applications.
Uses:
tracking livestock
stock control in shops
admission passes
tracking library books
Advantages:
no direct line of sight is required
several tags can be detected at the same time
very fast reading
Disadvantages:
more expensive than barcodes
radio signals may be interfered with
transmitted data can potentially be intercepted
OMR
Optical Mark Recognition (OMR) reads marks made in specific positions on a form.
Examples include shaded boxes on:
multiple-choice examination papers
questionnaires
voting forms
Advantages:
very fast
no manual typing
accurate when forms are completed correctly
Disadvantages:
special forms must be carefully designed
incorrectly placed marks may not be recognised
OCR
Optical Character Recognition (OCR) converts text from a hard-copy document into an electronic form that can be edited by software.
Uses:
passports and identity cards
converting printed documents into editable files
automatic number plate recognition
digitising old books and newspapers
Advantages:
faster than typing the document manually
reduces manual data-entry errors
Disadvantages:
may have difficulty recognising handwriting
recognition is not always completely accurate
OMR vs OCR
| OMR | OCR |
|---|
| Detects the position of marks | Recognises characters/text |
| Ideal for multiple-choice forms | Ideal for converting documents |
| Very accurate if forms are correctly completed | May struggle with handwriting |
| Requires specially designed forms | Can work with normal printed documents |
This distinction is particularly useful for exam questions.
Barcode reader
A barcode reader scans the pattern of lines in a barcode.
Uses:
supermarkets
stock control
libraries
identifying equipment
Advantages:
much faster than manually typing product codes
fewer input errors
allows automatic stock control
Disadvantages:
barcodes can be damaged
barcodes can sometimes be swapped between products
QR code reader
A QR (Quick Response) code is made from a pattern of light and dark squares.
It can contain much more information than a traditional barcode, including a website address.
A smartphone/tablet camera can scan the QR code. Software then converts the pattern into usable data.
Uses:
opening websites
advertising
electronic boarding passes
storing contact information
Wi-Fi authentication
links to apps
QR code compared with a barcode
| QR code | Traditional barcode |
|---|
| Stores much more data | Stores less data |
| Read using smartphone/tablet cameras | Usually needs a barcode scanner |
| Can contain web addresses | Mainly identifies an item |
| Can include error checking | Damaged barcodes may be difficult to read |
Disadvantage:
A QR code may contain a malicious link or code and could direct the user to an unsafe website.
2.3 Output devices and their uses
An output device presents the results of computer processing, usually in a form humans can understand.
Output devices can also be used in control systems, where a computer sends instructions to physical devices.
Monitors
CRT monitor
A CRT (Cathode Ray Tube) monitor creates an image using an electron beam and a phosphor screen.
CRT monitors are now uncommon but are included because they can be used with light pens.
Advantages:
can be viewed clearly from a wide range of angles
works with light pens
Disadvantages:
large and heavy
uses a lot of electricity
produces considerable heat
can flicker
LED and LCD screens
An LED screen consists of tiny red, green and blue light-emitting diodes.
An LCD screen uses liquid crystals to form pixels and requires a backlight. Modern LCD screens commonly use LED backlighting.
Uses of LCD screens:
desktop computers
laptops
smartphones
tablets
portable gaming devices
Advantages:
low power consumption
lightweight
thin
sharp image
does not flicker like a CRT
Disadvantages:
colour/contrast can change depending on viewing angle
dead or stuck pixels can occur
Touch screen as an output device
A touch screen can perform both jobs:
Output: the computer displays choices on the screen.
Input: the user touches one of the choices.
The computer then processes the choice and displays new information.
Examples:
smartphones
ATMs
ticket machines
museum information kiosks
Multimedia projector
A multimedia projector receives an image from a computer or another source, enlarges it and projects it onto a screen.
Uses:
classroom and training presentations
advertising
home cinema
Advantages:
large audience can view the same display
no need for everyone to have their own computer
Disadvantages:
expensive
image may sometimes be unclear
setup can be difficult
Printers
The book considers three main printer types:
Laser printer
A laser printer uses toner and an electrically charged drum.
Simplified process:
Laser creates image on drum → toner sticks to drum → toner transfers to paper → heated rollers fix toner to paper
Best suited for:
offices
large print jobs
fast, high-quality printing
Advantages:
fast for large print jobs
high-quality output
can handle many pages
Disadvantages:
colour laser printing can be expensive
not especially advantageous for only a few pages
Inkjet printer
An inkjet printer sprays tiny drops of ink onto paper.
Best suited for:
small print jobs
high-quality single pages
photographs
Advantages:
good-quality output
cheaper to buy than a laser printer
small and lightweight
Disadvantages:
slow for large print jobs
ink cartridges can be expensive
printouts may smudge
Dot matrix printer
A dot matrix printer uses pins that strike an inked ribbon against the paper.
Uses:
carbon/multi-part copies
receipts
dirty or dusty industrial environments
Advantages:
inexpensive to run
can produce carbon copies
works well in difficult environments
Disadvantages:
noisy
slow
lower print quality
Quick printer comparison
| Laser | Inkjet | Dot matrix |
|---|
| Best for large print jobs | Best for small/high-quality jobs | Best for multi-part forms |
| Fast | Slower | Slow |
| High quality | Very good photo output | Lower quality |
| Uses toner | Uses liquid ink | Uses ink ribbon and pins |
Plotter
A plotter produces drawings using pens, pencils or markers rather than creating images from dots in the same way as ordinary printers.
They are commonly associated with CAD.
Uses:
architectural drawings
engineering drawings
Advantages:
very accurate
very large drawings can be produced
high-quality output
Disadvantages:
slow
equipment can be expensive
requires a lot of space
3D printer
A 3D printer creates solid objects by building them up layer by layer.
This is called additive manufacturing.
Basic process
1. Create a design using CAD software.
2. Convert the drawing into a format understood by the 3D printer.
3. Set up the printer.
4. Build the object layer by layer.
5. Remove and finish the object.
Uses:
prosthetic limbs
parts for reconstructive surgery
aircraft parts
models and prototypes
replacement parts for old machinery
Advantages:
customised products can be made
rapid prototypes can be produced
complex or replacement parts can be manufactured
Disadvantages:
copyright/counterfeit products can be produced
technology may replace some manufacturing jobs
Speakers
Speakers produce sound from the computer.
Computer sound is stored digitally, but speakers require an analogue signal.
Conversion
Digital data → DAC → Amplifier → Speaker → Sound
The DAC (Digital to Analogue Converter) converts the digital data into an analogue electrical signal.
Uses:
music and videos
presentations
computer audio
helping visually impaired users by reading text aloud
Advantages:
many people can hear the output
sound can be amplified
Disadvantages:
sound can disturb other people
high-quality speakers can be expensive
Actuators
An actuator is a mechanical or electromechanical device used when a computer needs to control a physical device.
Examples include:
motors
relays
solenoids
Actuators may:
start or stop a conveyor belt
open or close a valve
operate a pump
activate a switch or buzzer
Because the computer produces digital signals while many actuators require analogue signals, a DAC may be required.
Control-system idea
Sensor → ADC → Computer → DAC → Actuator
For example:
Temperature sensor → ADC → Computer → DAC → Motor/valve
Advantage:
Devices can be operated remotely, including equipment in dangerous environments.
Disadvantage:
The actuator adds another component that could fail.
Important exam comparisons
Students should be particularly confident with:
Keyboard vs direct data entry
Mouse vs touchpad vs trackerball
OMR vs OCR
Barcode vs QR code
Barcode vs RFID
Contactless vs Chip and PIN
CRT vs LCD
Laser vs inkjet vs dot matrix printers
Input vs output use of a touch screen
ADC vs DAC
ADC and DAC
| ADC | DAC |
|---|
| Analogue → Digital | Digital → Analogue |
| Often used with sensors | Often used with speakers/actuators |
| Allows computer to understand analogue input | Allows computer to control analogue output |
Chapter 2 revision checklist
Students should be able to explain:
what an input device is
appropriate uses of common input devices
what direct data entry means
how OMR and OCR differ
how RFID, barcodes and QR codes are used
why sensors often require an ADC
the differences between laser, inkjet and dot matrix printers
how a 3D printer builds an object
how speakers use a DAC
the role of an actuator
why a touch screen can be both an input and output device