Input Devices

An information system can not do anything until you give it some information to process. Input devices transfer data into a computerised information system so that it can be processed. Remember that the computer does not process information it processes data.

An input device transfers data from the outside world into a computer.

There are two different categories of input device. They are :

There are many different input devices available. Each input device is suitable for a different purpose. Below you will find descriptions of the most common manual input and direct data entry devices.

Manual Input Devices

Keyboard

Almost all computers are supplied with a keyboard. A keyboard has over 100 keys on it. When you press a key a number (code) is sent to the computer to tell it which key you have pressed. The keys are arranged in four groups :

The keys on a keyboard are usually arranged in the same order as those on a typewriter. This layout of keys is called QWERTY because Q-W-E-R-T-Y is the order in which the letters occur on the top row of the keyboard. Some newer designs have the letters arranged in a different order. Most people find the QWERTY arrangement best as they have had some practise using it, but users trained on the new keyboards can type faster than the fastest typists can on QWERTY keyboards.

Concept Keyboard

A concept keyboard is a flat board which contains a grid of switches. Each switch can be programmed to do whatever you want. An overlay image is placed on top of the grid so that the user can tell what pressing on different areas (switches) will do. Example uses of concept keyboards include :

Concept keyboards are particularly useful for people who would find using an ordinary keyboard difficult and in locations where an ordinary keyboard might be damaged, e.g. by spillage or dust.

Touch Sensitive Screens

These screens do a similar job to concept keyboards. A grid of light beams or fine wires criss-cross the computer screen. When you touch the screen the computer senses where you have pressed. Touch screens can be used to choose options which are displayed on the screen. Touch screens are not used very often as they are not very accurate, tiring to use for a long period and are more expensive than alternatives like a mouse.The main applications for which touch screens are used is the provision of public information systems. Touch screen operated computers can be found in places such as travel agents and airports.

Light Pen

A light pen is a special pen which you can point at any computer monitor. When the pen is pointed at the screen the computer can work out where the pen is pointing. Light pens can be used to "draw" on the screen or to select options from menus presented on the screen. Light pens are extremely poor input devices. They are very inaccurate and tiring to use. Light pens are hardly ever used today.

Mouse

A mouse is the most common pointing device. You move the mouse around on a mat and a small cursor called a pointer follows your movements on the computer screen. By pressing a button on the mouse (most mice have 1,2 or 3 buttons) you can select options using icons or menus on the screen. Mice can also be used to "draw" onto the screen. They are particularly useful if your computer has a graphical user interface.

Most mice use a small ball located underneath them to calculate the direction that you are moving the mouse in. As you move the mouse this ball rotates. The mouse monitors how far the ball turns and in what direction and sends this information to the computer to move the pointer.

Tracker Ball

A tracker ball (or trackball) is an alternative to a mouse. It works in the same way as a mouse except that the ball is on top. Turning the ball with your hand moves the pointer on the screen. Tracker balls are used mainly when there is not enough space for a mouse. e.g. in portable computers.

Joystick

Joysticks are used to play computer games. You can move a standard joystick in any one of eight directions. The joystick tells the computer in which direction it is being pulled and the computer uses this information to e.g. move a spaceship on screen. A joystick may also have several buttons which can be pressed to trigger actions such as firing a missile.

The best joysticks, called analogue joysticks measure how far the joystick is being moved in the direction it is being pulled. This information is used to set how quickly the object on the screen moves. The further you push the joystick the faster the object moves.

Small joysticks called trackpoint devices are sometimes built into the keyboards of portable computers and used instead of a mouse.

Graphics Tablet

Graphics tablets are used mainly by professional graphics designers. Using a graphics tablet a designer can produce much more accurate drawings on the screen than he could with a mouse or other pointing device. A graphics tablet consists of a flat pad (the tablet) on which the user "draws" with a special pen called a stylus. As the user "draws" on the pad the image is created on the screen. The pad on which the user draws can be any size from A5 to A1 (eight times as large as an A4 page). Drawings created using a graphics tablet can be accurate to withing hundredths of an inch.

The stylus that the user draws with may have a button on it which will act like a mouse button. Sometimes instead of a stylus a highly accurate mouse-like device called a puck is used to draw on the tablet.

Mouse

Joystick

Graphics Tablet

Scanner

A scanner can be used to input printed images such as photographs or pages of text directly into the computer. A scanner works by shining a light at the image being scanned and measuring how much light is reflected back using an optical sensor. The amount of light that is reflected back tells the computer how light or dark the image is at each point.

The light and optical sensor reads information about one line of the image at a time. They must be moved down the picture to input the whole image. There are two different types of scanner :

Flatbed scanners are better as they can scan larger images and are more accurate than handheld scanners. On the other hand handheld scanners are cheaper and more portable. The price of flatbed scanners has fallen so much in recent years that handheld scanners are rarely sold now. A colour flatbed scanner can be purchased for around £100.

Optical Character Recognition (OCR) software can be used to read printed text from an image that has been scanned and store it as text rather than an image. You can then edit the text using a word processor or desktop publisher. OCR software is not yet sophisticated enough to read hand-written text accurately.

Digital Cameras

Digital cameras are used in the same way as standard photographic cameras. Most digital cameras look just like ordinary cameras. Unlike photographic cameras digital cameras do not use film. Inside a digital camera is an array of light sensors. When a picture is taken the array of sensors is used to input the image. The image can then be stored either in the camera's RAM or on a floppy disk. Later the pictures can be transferred onto a computer for editing using a graphics package.

Some digital cameras are available relatively cheaply, for about £300. However these cameras do not take very good pictures. More expensive cameras can take higher quality pictures but these are still not quite as good as standard photographs. Digital cameras are extremely useful for tasks such as producing newsletters.

Video Digitiser

A video digitiser takes an image from a video camera or television and converts it so that it can used by and stored on a computer. Almost all video digitisers now work in colour. Unlike scanners video digitisers can capture moving video sequences as well as still images. When a video sequence is captured the computer stores this as a sequence of still images called frames. These images are displayed quickly one after the other (rather like a flick-book) to create the illusion of a moving picture.

When you want to capture a video sequence you must tell the computer :

If you want to capture large images you may have to settle for a slow frame rate which will make the captured video film look jittery. If you want a fast frame rate you may only be able to capture a small image size. Video sequences captured using a video digitiser are often used in multimedia presentations.

Voice Recognition

Voice recognition systems listen to what people are saying and carry out the instructions given to them when people speak. A microphone is used to provide input for a voice recognition system. Currently these systems are not very sophisticated and are used only for certain applications. Existing voice recognition systems come in two different types :

In the last few years a number of voice dictation packages have been developed. These packages let the user dictate text into a computer to appear in a word processed document. Dictating like this can be much quicker than typing but the computer still makes some mistakes especially with short words.

Direct Data Entry Devices

Direct data entry devices are used when large volumes of data must be entered into the computer quickly. Consider how long it would take for the cashier to add up the cost of your shopping if she had to enter the price of every item you purchased. Nowadays barcode systems make this task much quicker. There are a variety of different direct data entry devices available. Different devices are suitable for different applications (tasks).

Bar Code Readers

Bar codes are often printed on products that we buy and are used by shops to produce bills for customers. A bar code is made up of a sequence of bars of different widths. Different groups of bars are used to represent different numbers. A printed bar code is therefore simply a way of representing a number. The number is often printed above or below the bar code so that humans can read it.

Bar codes are read into the computer using a wand or a fixed scanner. Bar codes are not easily damaged and can normally still be read if they are creased or not stuck onto a flat surface. They can be printed using a normal printer and ink and so are cheap to produce. The information normally included on a bar code for a product is country of origin, manufacturer and item code. The price is not included in the bar code.

A scanner can read a barcode number incorrectly. A check digit is inluded in the barcode number to reduce the likelihood of this happening.

Magnetic Stripe Codes

Magnetic stripes are built into many plastic cards such as cheque guarantee or credit cards. Magnetic stripes look like this :

The strip can contain up to 60 characters (numbers or digits) of information which is stored magnetically. Usually the information is put onto the stripe when the card is made and is never changed. Magnetic stripe codes can also sometimes be found on the back of railway tickets.

To be read the card is swiped through a machine which quickly and accurately reads the pattern of magnetism. The information stored on the card can be destroyed by exposure to magnetic fields, by scratching or by coming into contact with some liquids.

Smart Cards

Smart cards are often called input devices. In fact they are actually simple storage devices. A smart card contains a small RAM chip. When the card is put into a machine data can be read from the card or written onto it. A smart card can store much more data than a magnetic stripe can. A popular card in use at the moment can store 8k (about 8000 characters) of information.

Petrol companies and supermarkets use smart cards to store information about points that customers earn when they buy goods. Every time the customer buys something the number of points stored on the card is increased. The customer can then spend these points to buy goods.

Satellite television companies also use smart cards in their receivers. The smart card stores a code which is needed to let the receiver decode and display the pictures coming from the satellite. The government is currently considering introducing an identity card which could be based on a smart card. Many people are worried about this as people would not be able to tell what information was stored about them.

A new generation of smart cards is now appearing which contain a small microprocessor as well as memory. These cards are practically a complete computer system on a card.

Magnetic Ink Character Recognition (MICR)

The MICR system reads characters printed in a special magnetic ink into the computer. The main users of MICR are banks. They use it to read information from cheques into their computers so that the cheques can be cashed. Here is some information stored on a cheque using MICR :

The information printed on the cheque using MICR is :

MICR readers can only read one special font which can represent only numbers and a few punctuation marks. They can read characters very quickly and with 100% accuracy. Information printed in magnetic ink is also very secure. It is not possible to change the information by writing over it with a pen and the printed numbers are not damaged by folding (as often happens with cheques). Both the reader used by MICR and the special ink are expensive.

Optical Character Recognition (OCR)

An optical character recognition system consists of a scanner and some software. The scanner is used to scan an image of a page of text to be read into the computer. The software then examines the page and extracts the text from it, storing it in a form that can be processed.

OCR systems can now recognise a wide variety of computer fonts and read letters with over 95% accuracy. Some systems will recognise hand-written text reasonably well as long as it is written very neatly and usually put into boxes on a pre-printed form.

Optical Mark Recognition (OMR)

An optical mark reader reads marks made by pencil on a printed form into the computer. OMR systems are used by examination boards to collect the answers to multiple choice examinations and to purchase lottery tickets. Here is an example answer grid for an examination :

The student answers each question by drawing a line in pencil in the box that he/she thinks is the correct one. The answer grid is printed in a special coloured ink called that the OMR system will ignore. Marks down the side of the form are used to automatically line the form up in the reader so that it can be read. The reader detects where the marks are placed by shining a light at the page and measuring the amount of light reflected. Less light is reflected where the marks have been made. A pile of forms collected at the end of an examination can be put into a tray (called a bin). The reader will go through each form in turn and record the candidates marks.

Input using OMR is accurate and very fast. Problems can occur if the OMR forms get creased as the reader may jam.

Turnaround Documents

Optical mark recognition and optical character recognition are often used together in a turnaround document. A turnaround document is a document which :

Here is a turnaround document that a gas company could use to record meter readings.

The document is printed by a computer. The name, address and customer number of the person that the meter reader should visit is printed on the form. The customer's last meter reading is also included.

The meter reader takes the document and visits the customer's house. He then marks the current meter reading onto the OMR grid on the form. In the example the meter reader has marked the reading as 4605. The form is then returned to the gas company.

At the gas company the form is fed into a special reader. Optical character recognition is used to read the customer's number from the form. Optical mark recognition is used to read the meter reading that has been added. All of the information can be read into the computer automatically. A bill can be produced and posted to the customer without any need for human intervention. Turnaround documents allow cheap, fast input of information into a computer system

The turnaround document does not contain any instructions because the meter reader who fills it in will complete hundreds of similar forms every day. He will have been trained to use the forms so printing instructions on them would simply waste space.

Sensors

Sensors can be used to measure physical quantities such as temperature, light and pressure. The measurements can then be stored for later use (data logging) or used to control devices such as heaters or fans (computer control).

Questions

(1)What is the difference between a manual input device and a direct data entry device ?
(2)Which input devices would be the best ones to use for these applications ?

a) Checking train tickets.
b) Checking goods at the checkout in a food shop.
c) Storing information on bank cheques.
d) Storing identification information on a credit card.
e) Reading data from a printed document.
f) Recording some video clips to put onto the Internet.

(3)Copy and complete this paragraph :

There are two different input devices that you can use to get images from the real world into the computer. A _______ can be used to input printed pictures or text. Handheld ones are cheap and portable but can not be used with large images. For large images you need a ______ version. To capture moving images you need to use a _________. These capture a sequence of ______. When capturing video you need to tell the video digitiser the ____ of the image you want to capture and the frame ___ at which to capture the frames.

(4)What advantages do you think have resulted from using bar codes instead of entering prices into tills for :

a) customers
b) workers, and,
c) managers at a supermarket ?

(5)Explain how OMR is used to mark examination scripts. Why is OMR used ?
(6)MICR equipment is very expensive. Would it not be better to use OCR equipment for reading information from cheques instead ?
(7)a) Why is price not included on a bar code ?
b) Why is the product number printed underneath the barcode ?
(8)What is the difference between a magnetic strip card and a smart card ?
(9)What would be the best way to input commands to a computer system :

a) in a situation where you could not use your hands.
b) in a dirty and noisy environment.

(10)Why do you think some people are worried about the possibility of smart cards being used as identity cards which everyone would have to carry ?

 (C) P. Meakin 1998