Presentation on theme: "INPUT, OUTPUT & STORAGE INPUTINPUT: getting information and data into the computer OUTPUTOUTPUT: getting information and data out of the computer STORAGESTORAGE:"— Presentation transcript:
INPUT, OUTPUT & STORAGE INPUTINPUT: getting information and data into the computer OUTPUTOUTPUT: getting information and data out of the computer STORAGESTORAGE: being able to hold/keep information and data permanently even when the power is switched off ROM & RAMROM & RAM …something to cover later!
INPUT devices Keyboards A computer keyboard is an array of switches, each sends the PC a unique signal when pressed. The "Kinesis" ergonomic keyboard features concave keypads and is designed to minimize the effect of keyboard use on the body. The design of the Kinesis keyboard helps users achieve a more natural posture by aligning the hands, arms and shoulders. The "Microsoft Natural Elite" keyboard has become the most popular choice for an alternative keyboard priced under $
INPUT devices Mice In the early 1980s the first PCs were equipped with the traditional user input device - a keyboard. By the end of the decade however, a mouse device had become an essential for PCs running the GUI - based Windows operating system. GUI: Graphical User Interface
INPUT devices Touch Sensitive Screens A grid of light beams or fine wires 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. INPUT only?? Is it?? What about an interactive whiteboard… input or output?
INPUT devices 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. 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.
INPUT devices 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.
INPUT devices 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 within 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.
INPUT devices 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 Scanner : You place the image on top of the scanner. The scanner moves the light and sensor itself and scans the whole image automatically. Most flatbed scanners are A4 size. Handheld Scanner : You must manually push the light/sensor along the image. Handheld scanners are usually 5 inches wide. Scanner A scanner can be used to input printed images such as or pages of text photographs or pages of text directly into the computer directly into the computer. (Optical Character Recognition) 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.
INPUT devices 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.
INPUT devices 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 : Size : How big you want the image you capture to be. e.g. should it take up the whole screen, 1/2 the screen, 1/8th of the screen... ? Frame Rate : How frequently the frames should be captured from the video. 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.
INPUT devices 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 : Systems which recognise only a few words but can understand most peoples voices. e.g. telephone banking computers. Systems which recognise a wide vocabulary but need to be trained to understand each different voice. e.g. automatic dictation systems. 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.
DDE INPUT devices DDE: direct data entry Direct data entry devices are used when large volumes of data must be entered into the computer quickly 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.
DDE INPUT devices Magnetic Stripe Codes & Readers 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.
DDE INPUT devices Smart Cards & Readers 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.
DDE INPUT devices 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 : A unique number for the cheque. A code that identifies the bank and branch that issued the cheque. The number of the account that the cheque relates to. 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.
DDE INPUT devices 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. 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.
DDE INPUT devices Turnaround Documents A turnaround document is a document which : Has some information printed onto it by a computer. Has more information added to it by a human. Is fed back into a computer to transfer the added information into the computer. Here is a turnaround document that a gas company could use to record meter readings
DDE INPUT devices 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). Test & Learn on the net – click here: On-line resources for you to look at DATA LOGGING: click hereclick here DATA LOGGING can be taken a step further. MONITORING AND CONTROL: this will be covered in another lesson.