"Input and Output Devices - Download as PowerPoint"
Input and Output Devices Model of an IT System Example Information Systems Input Devices An input device transfers data from the outside world into a computer. There are two different categories of input device. They are : Manual Input Devices : With a manual input device the user must enter data into the computer by hand. e.g. mouse, keyboard, scanner. Direct Data Entry (DDE) Devices : A direct data entry device can transfer information automatically from a source document such as a form or barcode into the computer. The user does not need to manually enter the information. e.g. optical mark recognition, smart cards. Manual Input Devices Key Board • 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 Manual Input Device Concept Keyboard A concept keyboard is a flat board which contains a grid of switches.. An overlay image is placed on top of the grid so that the user can tell what pressing on different areas (switches) will do. Games for young children : Tills in restaurants/pubs Manual Input Device 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 you can select options using icons or menus on the screen. Manual Input Device Trackerball • 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. Manual Input Device Graphics tablets are used mainly by professional graphics designers. 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 Manual Input Devices Flatbed 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 Manual Input Device Digital Camera • 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 memory card. Later the pictures can be transferred onto a computer for editing using a graphics package. Manual Input Device Video Camera • Today video can be used to capture moving images. This information can then be uploaded on to a computer using video digitizer software onto your computer. Direct Data Entry Input Barcode reader Magnetic Strips MICR = Magnetic In Character Recognition OCR = Optical Character Recognition OMR = Optical Mark Recognition Output Devices Once the information system has processed the inputs it has received it must output the results of the processing for the user. An output device takes data from the computer and converts this into information in a form which is normally understandable by humans. Many different output devices are available to use with a computer system: Output Devices Monitor • Almost all computers have a monitor. Monitors are also known as Visual Display Units (VDUs). Most computers use this display as the main output device. There are two different types of display : Desktop Monitors LCD • 3 important features are Size, Color and Resolution Output Devices Printers • Two types Impact and Non Impact Printers • Impact include Dot Matirx and Line Printers • These are used for invoices etc • They are cheap and in expensive to run • Non Impact Printers • Ink Jet Ink jet printers are the most popular type of printer for use at home or in a small business. This is because they are relatively cheap to purchase and can print in colour. Ink jet printers generate output by squirting tiny jets of ink at the paper. They are slow • Laser Laser printers are called Page Printers because they print a whole page at a time. They are very fast but can be expensive to purchase. Output Devices Speakers • Sound can be output through loudspeakers or headphones. On PCs you also need to install a Sound Card to be able to output sound. Output Devices Other output devices include • Projector