CHAPTER 02 – INPUT DEVICES
Contents
Input Devices These are hardware devices that that allow data to be input into a computer. This chapter covers the many devices that can be used.
Keyboards Most use the QWERTY layout; some are now ergonomically designed to reduce health related risks such as carpel tunnel syndrome or RSI.
Uses: •
Input data into applications software
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Typing in commands into Command Line Interfaces
Advantages:
Disadvantages:
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Enables fast entry of new text into a document
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Users with limited arm / wrist use can find keyboards hard to use
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Well known and tried method of data entry
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Most people find them easy to use
Data entry is slow compared to direct (automatic) data entry such as optical mark recognition (OCR)
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It is easy to do verification checks as data is entered, as it appears on the screen simultaneously
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Have a fairly large footprint.
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To use effectively you need to learn how to touch type
Concept Keyboards Uses icons or phrases instead of standard letters. A concept keyboard has a flat touch sensitive surface. A plastic overlay is placed over this surface and different regions of the surface are programmed to act as keys.
Uses: •
Can be found in fast food restaurants; offices and shops where a single represents an item.
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For example one key with “tax” on it could be pressed to perform the calculation of adding text.
Advantages:
Disadvantages:
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Fast data entry as there is no need to type in whole commands Waterproof, which is useful in a restaurant environment Tamper proof which stops users being able to type in commands to corrupt the system (e.g. at unmanned airport information kiosks)
Options available may be restrictive
Numeric keypads Used to enter numbers only (although some have a function to input alphabet characters)
Uses: •
In ATMs (Automatic Teller Machine) to key in PIN (Personal Identification Number)
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‘dial’ a telephone number
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At EPOS (Electronic point of sale) terminals to key in barcode number if scanner fails
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Enter PIN using chip and PIN device
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Fast entry of data into a spreadsheet
Advantages:
Disadvantages:
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Faster than standard keyboards for entering numeric data
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Small keys means that they may be difficult to use
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Often small (e.g. on a smartphone) so are portable
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Difficult to use them for entering text
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Number layout on keypad isn’t intuitive
Mice Is an example of a pointing device; many have a scroll button to speed up moving through a document. Most mice are now optical (movement detected by flashing light) and / or cordless (example of a wireless device).
Uses: •
Opening, closing and minimising software
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Grouping, moving and deleting files
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Useful when editing images such as controlling the size and position
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Controlling position of mouse on screen to allow
Advantages:
Disadvantages:
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Faster to select options than using keyboard
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Rapid navigation through applications and the internet
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Small – take up little space
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If user has restricted hand / wrist movement, may be difficult to use Easily damaged Difficult to use if no flat surface available Not useful unless a GUI is being used
Touchpads Used in laptop computers as a pointing device. Controlled by the user moving their finger on the touchpad and then tapping it to simulate the left hand button of a mouse.
Uses: •
Same as for a mouse
Advantages:
Disadvantages:
Trackerballs Similar to an old style mouse, except that the ball is on top of the device and the user controls the pointer on the screen by rotating the ball with the hand. Usually have left and right click buttons with some even having a third button that represents a double click.
Uses: •
Similar to a mouse
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Useful when a user has a disability such as RSI
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Used in control room environments where it is faster to use than a mouse to navigate through process screens
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More robust than a mouse
Advantages:
Disadvantages:
Remote Controls Used to control the operation of other devices remotely by using infrared signals. Button on keypad are used to select options such as changing channels and volume. The transmitter in the remote control handset sends out a pulse of infrared light when a button is pressed on the handset. A transmitter is often a LED (light emitting diode) which is built into the pointing end of the remote control handset. The infrared light pulse represents a binary code that corresponds to a command, such as ‘power on’ or ‘volume down’. A receiver is built into the device being controlled in a position where it can easily receive the infrared light pulses – for example, it is built into the front of a satellite TV receiver. The receiver passes the code to a microprocessor, which decodes it and carries out the command. The remote control handset will often have two LEDs that light up at the same time when a button is pressed. One LED is the infrared transmitter and the light from this is invisible. The other LED emits a visible light and this is to reassure the user that the remote control is functioning.
Uses: •
Home entertainment and multimedia systems
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Industrial applications to remotely start and stop applications / machinery
Advantages:
Disadvantages:
Joysticks Similar function to mice and tracker balls; by gripping a stick, the pointer on the screen can be controlled and buttons are used to make selections. Often there is another button on top of the stick for gaming purposes, e.g. to fire a weapon.
Uses: •
Playing computer games
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Used in simulators (e.g. flight) to mimic actual controls
Advantages:
Disadvantages:
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Easier to navigate using a joystick rather than a keyboard
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Can control in three dimensions
Harder to control the pointing device with a joystick than a mouse.
Touch Screens Users can choose an option by simply touching the button / icon on the screen. The selection is automatically made without the need for any pointing device. Many touchscreens are basically on / off switches in that they rely on a particular area of the screen being touched; the input is simply whether or not that area has been touched. In this way the ticket machine inputs the type of ticket simply by interpreting the area of the screen that has been pressed. More advanced touchscreens allow for more than a simple on / off type of input. A stylus can be used like a pen to write on the screen. The touchscreen software then interprets what has been written. The devices often carried by delivery people are examples. When the delivery is made the customer ‘signs’ the small screen to show the package has been received.
Uses: •
Self-service tills
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ATMs
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POS
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Public Information Systems in airports, railway stations and tourist offices
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PDAs
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Mobile Phones
Advantages:
Disadvantages:
Magnetic Stripe Readers Used to read magnetic stripes found on the back of, for example, credit cards which can contain useful information such as the account number, sort code, expiry data and start date.
Uses: •
Used at ATMs or EFTPOS terminals
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Security cards for entry into buildings, hotel rooms
Advantages:
Real world example: Stripe cards can be used to control access to buildings. To gain access to the building or leave it, a stripe card is passed through a reader that controls whether a door opens or closes. If the identification number on the card is recognised by the ICT system, the door will open; if not, the door remains closed. As a result the ICT system knows who is in the building. Such a system could be used for registering school pupils; however, when large numbers of pupils enter a school at the same time, some may not bother to swipe their card through the reader. The ICT system can only know if a particular card is in the building and some pupils will give their cards to other to swipe for them. Such difficulties suggest countermeasures such as turnstiles or very careful supervision but these are often impractical as they can lead to long queues, disorder and the expense of employing supervisors.
Disadvantages:
Smart Card Readers Smart cards are similar to magnetic stripe cards but contain a chip which stores information such as the PIN and other personal data. The chip can be updated (e.g. loyalty cards) and has a much larger capacity than a magnetic stripe.
Uses: •
Examples: Loyalty cards, ID cards, public transport passes
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Can be used to track customer / passenger movements (e.g. on a metro system)
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Used with satellite systems to decode program signals
Advantages:
Real world example (2) – Oyster Cards: An Oyster Card is an electronic smart card that can be used to pay for travel, as well as in shops, theatres and restaurants and for entry to tourist attractions. It is used very much like a bank or credit card except that it is preloaded with cash credits. This can be done on the Web or in a manner similar to withdrawing cash from a cashpoint. As a result, payments can be made without online access at any time. Payment is made by touching the Oyster card on a reader and the payment is automatically deducted. This speeds up payment. Oyster cards are in widespread use in London
Disadvantages:
Chip and PIN readers Similar to smart card readers, but are used at EFTPOS terminals. The device has a slot into which the card is placed and the chip is read. The PIN is entered using the keypad. A small screen is also part of the reader, which gives instructions to the operator.
Uses: •
Used where payments are made using cards (e.g. restaurants, supermarkets, travel agents, etc.)
Advantages:
Disadvantages:
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Provide a more secure payment system than requiring a signature using a magnetic stripe, since the PIN typed in must match up with the PIN stored on the chip.
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Chip and PIN readers provide a more robust system than magnetic stripe readers.
Real world example (1) – ATM: In most European countries, these cards can be used to withdraw cash at a cashpoint. Cashpoints are specialised computer terminals with a small screen, numeric keyboard and smart card reader. The customer puts their card in the reader and is prompted to enter their four digit PIN. If the PIN entered on the keyboard matches the PIN read from the card, the customer can proceed; if not, the card is either confiscated or returned to the customer. Most ATMs will dispense cash and display the balance in the customer’s bank account. In a similar way, bank and credit cards can also be used to pay for goods in retail stores such as supermarkets.
Can be easy for someone else to see the PIN typed in which may lead to fraud.
Scanners The most common type is a flatbed which is made up of a glass panel and lid. The hard copy document or photo is scanned b a light source and produces a computer readable image. The subsequent image can then be manipulated by a drawing package. Text in a scanned document can be converted to an editable format by using OCR (Optical Character Recognition)
Uses: •
Scan in documents for use in various software applications
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Old and valuable documents and books can be scanned, thus protecting the originals from damage through handling and also producing records in case the paper copies are lost or destroyed.
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Non-digital photographs need to be scanned if they are to be stored on computer
Advantages:
Disadvantages:
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Images can be stored for editing at a later date
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Scanners are much faster and more accurate than typing in documents again (i.e. no typing errors)
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It is possible to recover damaged documents and photographs by scanning them and then using appropriate software to produce an
The quality can be limited, depending on how good the scanner resolution is.
Other types of scanners: •
Hand held scanners – reads in the picture while being dragged over it
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Sheet fed scanner – feeds the picture through rollers. The scanner reads the picture as the paper goes through. The picture must be printed on a flexible sheet of paper.
Barcode Readers Usually in the form of a barcode scanner and are often built into POS terminals in supermarkets. Handheld scanners (wands) are also very common for reading barcodes if portability is required (e.g. if the barcodes are on large or fixed objects).
Uses: •
Used in supermarkets and other shops where goods are marked with a barcode. The barcode gives information about product, which enables automatic stock control, itemised billing, etc.
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Used in libraries to scan both users’ library cards and barcodes on books, in order to keep track of books on loan
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As a safety function in many companies to ensure that electrical equipment is checked on a regular basis. Barcodes are placed on an item to identify it and a database holds the information related to the barcode so it is possible to interrogate the system as part of a safety audit.
Advantages:
Disadvantages:
Optical Mark Recognition (OMR) Devices Reads and interprets marks written in pen or pencil on a piece of paper. The places where the pen or pencil marks can be made are clearly shown on the form, for example on a national lottery form. An OMR reader can recognise the position of a mark or set of marks on paper, because the mark is darker than an unmarked area. The computer then records the marks position and can analyse it to determine the meaning of the date. Marks made on this kind of form must be very clear, or they may not be properly recognised.
Uses: •
Reading questionnaires, multiple choice exam papers and many other types of form where responses are registered in the form of lines or shaded areas.
Advantages:
Disadvantages:
Optical Character Readers (OCR) Devices Optical character recognition (OCR) is the name given to software that takes scanned text and converts it into a computer readable form. The text can then be used in various application packages such as word processors, desktop publishers and presentation software.
Uses: •
Processing of passports and identity cards
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Scanning documents so that they can be modified using a word processor or DTP package
Advantages:
Disadvantages:
Magnetic Ink Character Recognition (MICR) devices System that can read characters printed in a special ink (containing iron particles). Only certain characters written in a standard font can be read, for example the characters at the bottom of the bank cheque. These characters are converted into a form that the computer can understand and then stored in a computer file.
Uses: •
Primarily used to process cheques in banking operations. When a cheque is presented its value is then printed on the cheque in the special ink. The cheques are all gathered together (either at the end of the day or after some specified period) and then read using a batch processing method.
Advantages:
Disadvantages:
Digital Cameras Have almost replaced traditional film based cameras. Once photographs are stored in memory, they are easily transferred to a computer using a USB connection or by using an (secure digital) SD card. Unlike analogue cameras the image is caught by a series of sensors that are arranged in a grid. When all the individual pin-pricks of colour are put together they make a picture. These little areas of colour are called pixels (picture elements). The more pixels that are used, the better the quality of the picture. The camera records what each of the individual pixels has captured in storage, either in flash memory or on a removable media card. This card can be used to upload the picture into the computer; alternatively, most cameras can be connected to the computer with a cable and the images uploaded directly.
Uses: •
Photographs to transfer to a computer or to directly print
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Take and store short video clips
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Upload photos directly into applications software such as word
Advantages:
Disadvantages:
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Easier to produce better quality photos than with a traditional camera
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User will have to have some computer literacy skills
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Faster than having to scan in images
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No need to develop film
Some deskilling as software is now able to correct errors in taking the photos
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Easy to delete images and to retake new ones
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Resolution is not yet as good as traditional cameras (up to 800 megapixels)
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Can store a lot more images than traditional camera
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Images can take up a lot of memory so may need to be compressed
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The battery must be charged before it can be used to take pictures
Webcams Similar to digital video cameras; however, they are connected directly to the computer via USB as they do not have their own memory. The information that the webcam picks up is transmitted directly to the computer. Many computer systems now have webcams built into the top of their monitors as standard equipment.
Uses: •
Chatting online
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Video conferencing
Advantages:
Disadvantages:
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Can be left on constantly, only being activated as required
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Limited features and pictures can be of a poor quality
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Allow people to keep in contact with each other without having to travel (especially useful for the elderly or disabled)
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Need to be connected to or built into the computer.
Microphones Can be connected directly to a computer to allow sounds to be inputted and then manipulated. Input sound is converted to an analogue signal and then into a digital signal. The computer’s sound card usually does this automatically (acting as an analogue to digital converter (ADC)).
Uses: •
Input sounds / speech to be used in various applications (e.g. presentations, special effects)
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Voice recognition software to convert speech into text that can be used in a word processor
Advantages:
Disadvantages:
Other audio input devices and technologies There are various input devices and technologies relating to computer input from sound.
Touch Tone Telephones: This issues a beep whose frequency depends on the button being pressed. A receiving device on the other end of the line can analyse the beep to determine which button is being pressed. So your touch – tone telephone can function as an input device. You may then listen to a voice response on the earpiece.
Natural language processing: This is where a computer processes a sequence of instructions or data given in a natural language – for instance, spoken English. You could use natural language processing to dictate a letter or give instructions to a computer.
MIDI keyboard (musical instrument digital interface) : It needs to be connected to the computer system using a MIDI interface – a special type of interface which translates the signal coming from the keyboard into electronic data that the computer can handle. For example, when a key is pressed on the keyboard, the MIDI turns that input into the pitch, duration and so on of the note, which can be used to reproduce the note electronically.
Sensors A sensor is a device which inputs data to a computer, where the data is a measurement of some physical quantity which is continuously changing (e.g. temperature, light, moisture, etc.). These physical quantities are analogue in nature but as computers only understand digital data (i.e. 1s and 0s) the information from the sensors needs to be converted into a digital form. This is done using an Analogue to digital converter (ADC). Sensors are used extensively for data logging and control applications. They are essential in applications such as the following: automatic washing machines, automatic cookers, air conditioning controllers, central heating controllers, computer controlled greenhouses, burglar alarm systems, control of factory production lines, robotics, and for monitoring scientific experiments and remote weather stations.
Uses: •
Monitoring and control applications – see table below
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To send data direct to a spreadsheet from, for example, a scientific experiment
Type of sensor
Applications
Temperature
Automatic washing machines, central heating systems, automatic greenhouses, ovens
Pressure
Burglar alarm systems, washing machines, robotics, environmental monitoring
Light
Automatic greenhouses, automatic doors, burglar alarm systems, street lighting control
Sound
Burglar alarm systems, monitoring liquid and powder flow in pipes
Humidity / moisture
Automatic greenhouses, environmental monitoring, factories where moisture levels are crucial (e.g. manufacture of microchips, paint spraying)
pH
Automatic greenhouses, chemical processes, environmental monitoring.
Advantages:
Advantages (cont.):
Disadvantages:
Real world example of sensors – Washing Machine When a washing machine is turned on to do the wash, the tub will fill with water. The processor in control of the wash cycle will need to ensure that the water is hot enough to do the wash. If it is not hot enough, the processor will turn on the heating element until the temperature sensor reports that the water is hot enough. If the water is too hot then the processor may let in some cool water to cool the water down until the temperature sensor reports that the water is cool enough. Note that this device is called a temperature sensor and not a heat sensor. This is because heat is not a measurement. It is not called a thermometer because that is something designed for human beings to look at.
Check that door is shut
Check temperature of water
Is it hot enough?
no
Heat water
yes Start Wash
Real world example of sensors – Burglar Alarm Pressure Pad A pressure pad could be used under the carpet in a house as part of a burglar alarm system. If something presses on the pad and that makes a contact which sets the alarm off then it is not a sensor, it is just a switch. However, if measurements of the pressure are sent to a processor a decision can be made. The processor can decide whether it is enough pressure to indicate a human being or whether it is a cat and so the alarm should not go off. If the processor can make a decision like this, then the device that reads the pressure is a sensor.
Graphics Tablets Used with a stylus to produce freehand drawings which can then be stored in a file on the computer.
Uses: •
Produce drawings, computer graphics, etc.
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Faster for typing in Chinese or Japanese characters than using a keyboard
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Used in Computer Aided Design (CAD)
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Copying drawings on paper by allowing the user to trace over the
Advantages:
Disadvantages:
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Can modify drawings before they are input
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They are more expensive than other pointing devices, such as a mouse
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Very accurate method of drawing, which is better than using a mouse or trackerball
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Difficult to relate the position and movement of the stylus on the tablet with the position and movement of the pointer in the screen
Light Pens Is shaped like a pen and contains sensors that send signals to a computer whenever light changes are detected. Only work with CRT (Cathode Ray Tubes) monitors because they rely on the screen image being built up row by row by an electron beam. The screen is refreshed 50 times every second, so the computer is able to determine the pen’s position by noting exactly when the light pen detected the electron beam passing its tip. The term light pen might also be used to describe hand held bar code readers and other hand held scanners.
Uses: • •
Selecting objects and menu options on CRT screens Drawing on screen with CAD packages
Advantages:
Disadvantages:
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More accurate than touch screens
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They are small so can be used where space is an issue
Problems with lag when drawing on screens
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Only work with CRT screens
Easy to use
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Not very accurate when drawing
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Biometric Scanner This is a pattern recognition system which makes a personal identification based on a person’s unique physical characteristics. Biometric scanners can use face recognition, fingerprint matching, iris and retinal scans, voice recognition, and hand geometry. Biometric scanners can be built into mobile phones, desktop and laptop computers, and smart cards. They can be used to control entry to buildings and can even replace car keys.
Uses: • • •
Security access to IT systems and buildings School registration As a substitute for car keys
Advantages:
Disadvantages:
Evaluating input devices It is important to choose the best device, based on the users’ needs and considering the advantages and disadvantages of each. Webcams, video cameras, scanners and digital cameras can all capture images, but it is the purpose behind capturing the image that influences the decision about which to use. The diagram below illustrates the main considerations that need to be taken when considering a suitable input device. Speed of input How quickly can information be input or the device used?
Relevance to application Is the right device being used for the right task?
Cost Specialist equipment can be expensive
Accuracy of input
Important Considerations
Can fine detail or precise movements be recorded?
Task 1: Consider the following types of organisations and their requirements: •
An animated film studio
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A bank
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A hospital
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Your school
List and describe four input devices you might find in each organisation. State their advantages