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INPUT DEVICES Input devices are used to get data into a system. The ideal input devices would be able to get data into a system as accurately as possible, in the least amount of time ands preferably without human intervention. The device would also be relatively cheap. Unfortunately, no perfect input device is available and the choice is always a compromise. The fastest input devices are suitable only for a narrow range of applications. Here are some of the main input devices in use today.
TYPES OF INPUT DEVICES • KEYBOARD • MOUSE • JOYSTICK • LIGHTPEN • TOUCH SCREEN • GRAPHICS TABLETS (DIGITISERS) • MAGNETIC STRIPE READER • BARCODE READERS • OPTICAL CHARACTER READER (OCR) • MAGNETIC INK CHARACTER READER (MICR) • OPTICAL MARK READER (OMR) • MICROPHONE • ELECTRONIC POINT OF SALE (EPOS) • ELECTRONIC FUND TRANSFER AT POINT OF SALE (EFTPOS) • SCANNER • DIGITAL CAMERA • WEBCAM
KEYBOARD The keyboard is the oldest and most familiar of all input devices. Keyboards are intelligent devices and contain their own chips. Basically each key acts as a switch which closes when the key is pressed. The microprocessor scans the keyboard hundreds of times a second to see if a key has been pressed; if it has, a code that depends on which key has been pressed is sent to the processing unit. The CPU translates this code into an ASCII code (the code that computers use to represent characters on the computer keyboard), which is then used by the computer program. A standard keyboard is called a QWERTY keyboard because of the arrangement of the letters of the top row of the alphabet key.
Types of Keyboards Types of Keyboards Enhanced / Extended Keyboard Enhanced / Extended Keyboard Ergonomic Keyboard Ergonomic Keyboard • Enhanced or Extended keyboard – Typically 101 keys laid out in the QWERTY fashion; connected to the computer by a cable • Cordless keyboard – Uses infrared or radio wave signals • Ergonomic keyboard – Designed to help prevent cumulative trauma disorder (CTD) or damage to nerve tissues in the wrist and hand due to repeated motion
THE MOUSE A mouse is an input device that translates its movements on the desktop into digital information; this is feed to the computer which in turn causes the cursor to move on the screen. Underneath the mouse is a ball which rotates as the mouse is moved on the desk, and sensors pick up this movement. Mice usually have one, two or three buttons, used which are to make selection on the screen To see types of mouse's click here
Types of Mice Wheel Mouse Cordless Mouse • Wheel mouse – Contains a rotating wheel used to scroll vertically within a text document; connects to PS/2 port or USB port • Cordless mouse – Uses infrared signals to connect to the computer’s IrDA port; it must be within sight of the receiving port
Using the Mouse • Mouse buttons enable the user to initiate actions. • Clicking (left-, right-, or double-clicking) allows the user to select an item on the screen or open a program or dialog box • Click and drag – Holding down the left mouse button and moving the mouse enables the user to move objects on the screen
TYPES OF MOUSE'S • TRACKER BALL • TOUCH BAD • 2 button mouse • scrolling 2 button mouse • 3 button mouse • numeric keypad and mouse
JOYSTICK • Ajoystickorcontrol stickIs a personalcomputer peripheralor general control device consisting of a handheld stick that pivots about one end and transmits its angle in two or three dimensions to acomputer. • Joysticks are often used to controlvideo games, and usually have one or more push-buttonswhose state can also be read by the computer. The term joystick has become a synonym for game controllers that can be connected to the computer since the computer defines the input as a "joystick input". • Apart from controlling games, joysticks are also used for controlling machines such asaircraft, cranes, trucks, poweredwheelchairsand some zero turning radiuslawn mowers. More recently miniature joysticks have been adopted as navigational devices for smaller electronic equipment such as mobile phones. Joystick elements: 1. Stick 2. Base 3. Trigger 4. Extra buttons 5. Autofire switch 6. Throttle 7. Hat Switch (POV Hat) 8. Suction Cup
LIGHT PEN A light Pen is a computer input device in the form of a light-sensitive wand used in conjunction with the computer's CRT monitor. It allows the user to point to displayed objects, or draw on the screen, in a similar way to a touch screenbut with greater positional accuracy. A light pen can work with any CRT-based screens, but not with LCD monitor, projectors and other display device. A light pen is fairly simple to implement The light pen works by sensing the sudden small change in brightness of a point on the screen when the electron gun refreshes that spot. By noting exactly where the scanning has reached at that moment.
Touch screen A type of display screen that has a touch sensitive transparent panel covering the screen. Instead of using a pointing device such as a light pen or mouse, you can use your finger to point directly to object on the screen. Although touch screen provide a natural interface with for computers novices, they are unsatisfactory for most application because the finger is such a relatively large object. It is impossible to point accurately to small areas of the screen. In addition, most users find touch screens tiring to the arms after long use.
Graphic Tablets A graphics tablet (or digitizing tablet, graphics pad, drawing tablet is a computer input device that allows one to hand-draw images and graphics, similar to the way one draws images with a pencil and paper. A graphics tablet consists of a flat surface upon which the user may "draw" an image using an attached stylus, a pen-like drawing apparatus. The image generally does not appear on the tablet itself but, rather, is displayed on the computer monitor
MAGNETIC STRIPE READER A magnetic stripe card is a type of card capable of storing data by modifying the magnetism of tiny iron-based magnetic particles on a band of magnetic material on the card. The magnetic stripe, sometimes called a magstripe, is read by physical contact and swiping past a reading head. Magnetic stripe cards are commonly used in credit cards, identity cards, and transportation tickets. They may also contain an RFID tag, a transponder device and/or a microchip mostly used for business premises access control or electronic payment.
BARCODE READERS A barcode reader (or barcode scanner) is an electronic device for reading printed barcodes. Like a flatbed scanner, it consists of a light source, a lens and a photo conductor translating optical impulses into electrical ones. Additionally, nearly all barcode readers contain decoder circuitry analyzing the barcode's image data provided by the photo conductor and sending the barcode's content to the scanner's output port.
OPTICAL CHARACTER READER (OCR) OCR Short for Optical Character Recognition or Optical Character Reader, OCR is the process where images of letters can be entered into the computer as data using a scanner or other hardware device. OCR is far from perfect, but is currently the best method of digitizing typed pages of text. Some computer fax applications also use OCR to transform incoming faxes from graphics files into word processing documents. Some examples of how an OCR may be used would be a company that has hard copies of manuals or other company information and wanting to convert them into data that can be easily accessed and stored. Another example is companies and libraries taking copies of books, magazines, or other old printed material and using an OCR to scan it into computers.
MAGNETIC INK CHARACTER READER (MICR) What is MICR? Why Magnetic Ink? What is MICR? It’s those mysterious, funny characters at the bottom of a check, sometimes referred to as the MICR line. These characters are the key by which all checks are automatically processed in the United States today. This automated process is based on a technology called Magnetic Ink Character Recognition or MICR. As the name indicates, this technology uses magnetic reading to identify these unique numbers and characters. Currently, the United States processes over 65 billion checks and other financial documents per year based on the details of this MICR line. MICR technology was developed in the mid-1950s to address the volume of checks that were being processed manually. The goal was to accelerate the check routing process to route the check back to the location where the funds exist and to settle the transfer of funds as soon as possible. To address this problem, a group of individuals from the American Bankers Association and Stanford University developed a set of 14 unique characters called E13B MICR fonts. These fonts are printed with magnetic ink or toner that when magnetized, will emit a magnetic signal that identifies each unique character. What do the characters mean? The digits 0-9 are self-explanatory. However, the E138 fonts have four special symbols with the following meanings:
OPTICAL MARK READER (OMR) Optical Mark Reader/Recognition is a reader that detects marks in a certain position on a piece of paper. In this method, special printed forms are designed with boxes which can be marked with a dark pencil or ink. Each box is annotated distinctly so that the user clearly understands what response he/she marking. Such a document is read by a document reader which transcribes the marks into electrical pulses. These pulses are then transmitted to the computer. These types of documents are applicable in areas where responses are one out of a small number of alternatives. The OMR is a powerful tool that has many features. If you are using casstat (grading tests), the OMR will print the number of correct answers and the percentage of correct answers at the bottom of each test. It will also record statistical data about each question. This data is recorded in the output file created when the forms are scanned.
MICROPHONE A microphone, sometimes referred to as a mike or mic (both pronounced /ˈmaɪk/), is an acoustic to electric transducer or sensor that converts sound into an electrical signal. Microphones are used in many applications such as telephones, tape recorders, hearing aids, motion picture production, live and recorded audio engineering, in radio and television broadcasting and in computers for recording voice, VoIP, and for non-acoustic purposes such as ultrasonic checking.
ELECTRONIC POINT OF SALE (EPOS) Point of sale or point of service (POS or PoS) can mean a retail shop, a checkout counter in a shop, or the location where a transaction occurs. More specifically, the point of sale often refers to the hardware and software used for checkouts -- the equivalent of an electronic cash register. Point of sale systems are used in supermarkets, restaurants, hotels, stadiums, and casinos, as well as almost any type of retail establishment
ELECTRONIC FUND TRANSFER AT POINT OF SALE (EFTPOS) EFTPOS is an electronic payment method which involves goods or services being paid for at the point of sale. The transaction may be initiated either by the EFTPOS card (Credit/Debit card) being swiped through a card reading device prior to the authorization of the transaction by means of PIN number being inputted via a hand held pad by the customer or the cards swipe being followed by the customer signing a paper voucher.
SCANNER In computing, a scanner is a device that analyzes images, printed text, or handwriting, or an object (such as an ornament) and converts it to a digital image. Most scanners today are variations of the desktop (or flatbed) scanner. The flatbed scanner is the most common in offices. Hand-held scanners, where the device is moved by hand, were briefly popular but are now not used due to the difficulty of obtaining a high-quality image. Both these types of scanners use charge-coupled device (CCD) or Contact Image Sensor (CIS) as the image sensor, whereas older drum scanners use a photomultiplier tube as the image sensor. Another category of scanner is a rotary scanner, used for high-speed document scanning. This is another kind of drum scanner, but it uses a CCD array instead of a photomultiplier. Other types of scanners are planetary scanners, which take photographs of books and documents, and 3D scanners, for producing three-dimensional models of objects, but these types of scanner are considerably more expensive than other types of scanners. Another category of scanner are digital camera scanners, which are based on the concept of reprographic cameras. Due to increasing resolution and new features such as anti-shake, digital cameras have become an attractive alternative to regular scanners. While still containing disadvantages compared to traditional scanners, digital cameras offer unmatched advantages in speed and portability
Digital camera is a camera that takes video or still photographs, or both, digitally by recording images on a light-sensitive sensor. Many compact digital still cameras can record sound and moving video as well as still photographs. In the Western market, digital cameras outsell their 35 mm film counterparts. Digital cameras can include features that are not found in film cameras, such as displaying an image on the camera's screen immediately after it is recorded, the capacity to take thousands of images on a single small memory device, the ability to record video with sound, the ability to edit images, and deletion of images allowing re-use of the storage they occupied. Digital cameras are incorporated into many devices ranging from PDAs and mobile phones (called camera phones to vehicles. The Hubble Space Telescope and other astronomical devices are essentially specialized digital cameras.
WEBCAM Webcams are small cameras, (usually, though not always, video cameras) whose images can be accessed using the World Wide Web, instant messaging, or a PC video conferencing application. The term webcam is also used to describe the low-resolution digital video cameras designed for such purposes, but which can also be used to record in a non-real-time fashion. Web-accessible cameras involve a digital camera which uploads images to a web server, either continuously or at regular intervals. This may be achieved by a camera attached to a PC, or by dedicated hardware. Videoconferencing cameras typically take the form of a small camera connected directly to a PC. Analog cameras are also sometimes used (often of the sort used for closed-circuit television), connected to a video capture card and then directly or indirectly to the internet
OUTPUT • Printer • Visual Display Units • Graph plotters
Printers A computer printer, or more commonly a printer, produces a hard copy (permanent human-readable text and/or graphics) of documents stored in electronic form, usually on physical print media such as paper or transparencies. Many printers are primarily used as local computer peripherals, and are attached by a printer cable to a computer which serves as a document source. Some printers, commonly known as network printers, have built-in network interfaces (typically wireless or Ethernet), and can serve as a hardcopy device for any user on the network. Individual printers are often designed to support both local and network connected users at the same time. Click here to Types of printers
Type of printers • Laser printer • Inkjet printers • Dot-matrix printer
Laser printer Disadvantages: Non-color laser printers are more expensive than ink-jet printers (but the difference is narrowing). Color laser printers are considerably more expensive. (but their speed and high quality output means they are becoming more popular). Advantages: They are quiet and fast and produce high quality printouts. Running cost are low because although toner cartridges are expensive to replace, they last a long time. Disadvantages: Non-color laser printers are more expensive than ink-jet printers (but the difference is narrowing). Color laser printers are considerably more expensive. (but their speed and high quality output means they are becoming more popular). Advantages: They are quiet and fast and produce high quality printouts. Running cost are low because although toner cartridges are expensive to replace, they last a long time. A laser printer is a common type of computer printer that rapidly produces high quality text and graphics on plain paper. Like photocopiers, laser printers employ a xerographic printing process but differ from analog photocopiers in that the image is produced by the direct scanning of a laser beam across the printer's photoreceptor A laser printer is a common type of computer printer that rapidly produces high quality text and graphics on plain paper. Like photocopiers, laser printers employ a xerographic printing process but differ from analog photocopiers in that the image is produced by the direct scanning of a laser beam across the printer's photoreceptor
Inkjet printers How it works: The print head contains tiny nozzles through which different coloured inks can be sprayed onto the paper to form the characters or the graphic images. The ink is forced out by heat or by tiny piezoelectric crystals which change shape when an electric current is applied across them. Disadvantages: The ink cartridges can be expensive so running costs can be high. The printing speed is slow compared to a laser printer. Advantages: These printers are relatively inexpensive and produce high quality black and white or colour printing.
Dot-matrix printer Disadvantages: The printing quality is low - these printers produce low to medium quality black and white printing and can only print low resolution graphics. Because of the impact of the pins against the paper, these printers can be quite noisy. Advantages: The purchase cost is low and the running costs are very low. They can print fairly quickly, particularly if you remember that multiple copies are being printed in one print run. They are robust and can operate in harsh environments. If several sheets of self-carbonating paper are placed into the printer then the impact will produce multiple copies. How it works: This has a print head that travels across the paper. The head has a set of pins which are pushed out to form the shape of each character The pins hit an ink ribbon against the paper as the print head moves along. An animation showing how head of a 21 pin dot-matrix printer moves across the paper, firing the pins that strike the ink against the paper.
VISUAL DISPLAY UNIT • A monitor is a peripheral device which displays computer output on a screen. • Screen output is referred to as soft copy. • Types of monitors: • Cathode-ray tube (CRT) • Liquid Crystal Display (LCD or flat-panel)
Cathode-ray tube (CRT) • Resemble televisions • Use picture tube technology • Less expensive than a LCD monitor • Take up more desk space and use more energy than LCD monitors
Liquid Crystal Display (LCD) • Cells sandwiched between two transparent layers form images • Used for notebook computers, PDAs, cellular phones, and personal computers • More expensive than a CRT monitor • Take up less desk space and use less energy than CRT monitors • Types of LCD monitors: • Passive-matrix LCD • Active-matrix LCD • Gas plasma display • Field emission display
Monitor Specifications • Screen size – The diagonal measurement of the screen surface in inches (15, 17, 19, 21) • Resolution – The sharpness of the image determined by the number of horizontal and vertical dots (pixels) that the screen can display (800 x 600, 1024 x 768, 1600 x 1200) • Refresh rate – The speed at which the screen is redrawn (refreshed) and measured in Hertz (Hz) (60Hz, 75Hz)
Graph plotters the flat-bed plotter uses high precision motors to draw on paper with colored ink pens. The motors move an arm across the paper in the ‘x’ direction and a pen unit up and down the arm in the ‘y’ direction. An electromagnet lifts and drops the pen onto the paper. Plotters are often used in science and engineering applications for drawing building plans, printed circuit boards and machine parts. They are fast and accurate but relatively expensive compared to printers. They can produce far larger printouts than standard printers, up to the size of a small room. Braille printer - by converting text into the Braille code, this printer produces patterns of raised dots on paper for use by the blind.
