AS Level ICT

Selection and use of input devices and input media: Simple devices

Selecting suitable input methods

• An ideal solution to the inputting of data would make it:– Automatic– Fast– Cheap– Accurate

• There are very few input devices that match these criteria, and most solutions involve some level of compromise when the choice of input device is made

Selecting suitable input methods

• There are two types of input method• These are:

– The manual method: this method requires a person enter the data (e.g. data entry using a keyboard)

– The automatic method: this method requires the work to be sorted into ‘batches’ which the system then ‘reads’ automatically (e.g. optical mark sheets)

Selecting suitable input methods

• Whichever method is chosen, both involve the use of input devices

Input devices

• Input devices are used to get data into a system• They should be able to do this as accurately and

quickly as possible, and with the minimum of human intervention

Input devices

• The most common types of input devices are:– Keyboards– Point and Click devices (including mouse,

tracker balls, touch sensitive pads, joysticks, light pens, touch screens, and graphic tablets)

– Readers (including magnetic strip readers, barcode readers, optical character readers/recognition, magnetic ink character readers/recognition, and optical mark readers/recognition)

Input devices

– Punched cards and tape (including punched cards and Kimball tags)

– Sound capture devices (including voice recognition and microphones)

– Terminals (including EPOS and EFTPOS terminals)

– Digital imaging devices (including video digitisers, scanners, digital cameras, and web cams)

– Tonal devices (including touch tone telephones)

Keyboards

• The most common type of keyboard is the QWERTY keyboard (so called because the top line of letters are q, w, e, r, t, and y)

Keyboards – Qwerty keyboard

Keyboards – Concept keyboard

• Another type of keyboard is the concept keyboard• The can be specially designed so that people with

restricted vision can use them to interface with a computer

• Concept keyboards can also be programmed to perform common functions with one keystroke (e.g. a computerised till in a fast food restaurant)

Keyboards – Concept keyboard

Each button can be programmed to do whatever you want

An overlay sheet with pictures or symbols is placed on the grid so that the user can tell what pressing on different areas will do

Keyboards – Concept keyboard

Concept keyboards are used when fast input is needed and are ideally suited to selecting from a limited range of choices

Keyboards - Advantages

• Keyboards – and QWERTY keyboards in particular – do have some advantages as a device for inputting data:– They are cheap – they are usually supplied with

the computer– They are in universal use – most people know

how to use one

Keyboards - Disadvantages

• Keyboards also have several disadvantages:– They are slow to use – even the best typists can

only manage a maximum of 100 words per minute

– They cost a lot to operate – the workers who are entering the data have to be paid

– Entered data tends to be inaccurate – this is often due to transcription and transposition errors being made

Keyboards - Disadvantages

– They are associated with particular health problems (RSI – Repetitive Strain Injury)

‘Point and Click’ devices

• ‘Point and Click’ devices include mouse, tracker balls, touch sensitive pads, joysticks, light pens, touch screens, and graphic tablets

Mouse

• The mouse translates movement on the desktop into digital information

• This is information is converted into movement of the cursor on the screen

• A mouse will also have one, two, or three buttons which can be clicked to help the user to select what functions they wish to use

Tracker ball

• The tracker ball is essentially an upside down mouse

• Instead of moving the mouse on the table top, the ball is rotated

• This achieves the same result as using a mouse but takes up far less room

Touch sensitive pad

• These are most commonly found on laptop computers

• A stylus or the user’s finger is pressed gently onto the pad, and as it is moved the cursor moves on the screen

Joystick

• These are most commonly used to interact with computer games, although they are also used in other circumstances (e.g. on hospital scanners)

• Like the tracker ball, the movement of the joystick moves the cursor on the screen

Light pen

• Light pens are usually used with specialist design software

• The light pen works by being touched against the screen

• As the pen is moved on the screen, the cursor moves

Touch screen

• The touch screen is a special type of screen which is sensitive to touch

• Selections can be made by touching the screen• These are particularly useful in banks, building

societies, and shops, where customers who are not used to using a keyboard can interact with a computer system

Graphics tablet/Digitiser

• A graphics tablet allows the user to create designs directly onto the screen

• A special stylus – sometimes called a digitiser – is connected to the computer via the graphics tablet, and as the user ‘draws’ on the tablet with the stylus the drawing appears on screen

‘Point and Click’ devices - Advantages

• Most are very simple and require little or no training to use

• The most common – the mouse and the touch sensitive pad – come as standard with either a desktop or laptop computer respectively

‘Point and Click’ devices - Disadvantages

• The main disadvantage of ‘Point and Click’ devices is that they generally require good eye-hand coordination, and in some cases – for example, the graphics tablet/ digitiser and light pen – a degree of artistic talent, in order to be used effectively

Sound capture devices

• The most common use of sound capture devices involves the use of voice recognition software and microphones

Sound capture devices

• Voice recognition software ‘remembers’ the way a user speaks, and converts their speech into text that appears on screen

• Although voice recognition software has become increasingly sophisticated, many such programs have difficulty converting more than 90% of common words accurately

Sound capture devices - Advantages

• They should be very easy to use and require little or no training

• They are faster than typing• They can achieve 99% accuracy• They can be cheap – most desktop and laptop

computers come with a microphone installed as standard; all that is needed is the purchase of the voice recognition software

Sound capture devices - Disadvantages

• The software needs to be ‘trained’ to recognise each users voice – this can take a considerable amount of time

• Because men and women usually have different voice pitch (i.e. varying frequency of vibration), and because the software is programmed to register a limited range of voice pitch, the software tends to be more accurate when transcribing text spoken by men rather than by women

Sound capture devices - Disadvantages

• Background noise can cause errors (e.g. a telephone ringing or someone other than the user speaking as the device is being used)

• They do not work with database software

Digital imaging devices

• These include video digitisers, scanners, digital cameras (still and motion), and web cams

Video Digitisers

• The video digitiser is a combination of hardware and dedicated software that converts an analogue signal into a digital signal

• This is the basis of most set top boxes that give access to digital television on standard television sets

• It can also be used to ‘capture’ still images from video

Scanners

• Scanners are used to scan text or images so that they can be stored on and manipulated by computer

• The scanner converts the text or image into a digital signal which it sends to the computer

• The user can then decide whether they want to store or manipulate what they have scanned

Digital cameras

• Digital cameras convert the analogue image seen through the camera’s lense into a digital signal that can be stored

• Each picture is split up into millions of tiny squares (or pixels), each of which is a different colour

• Each pixel is stored as a ‘bit’ of digital information

Webcams

• Web cameras (webcams for short) are small digital cameras which are attached to computers so that still and motion digital images can be ‘captured’ and used

• They are often used in conjunction with the Internet so that people can videoconference

Digital imaging devices - Advantages

• They are easy to use and usually require little training to use

• They are relatively inexpensive, and are become increasing cheaper and more available (e.g. many mobile phones have digital cameras capable of capturing still images and short movies)

Digital imaging devices - Disadvantages

• They require specialist software to manipulate any text that has been captured (i.e. any text scanned in requires character recognition software to convert the text into a document format that can be altered or reformatted)

• They require specialist software to manipulate any images that have been captured (e.g. the removal of ‘red eye’; the cropping and/or resizing of an image)

AS Level ICT

Selection and use of input devices and input media: Simple devices