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					Input and Output
The User Connection

Input-Getting Data From the User
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Some data such as a scanned bar code or speech that is spoken to the computer can go directly for processing Some input must go through intermediate handling such as translating a source document into machine readable data

Keyboard
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Standard keyboards are common input devices on computers Specialized keyboards exist such as fast food restaurant ordering systems Cordless keyboards use a battery powered transmitter instead of a cord to transfer data to the computer Ergonomic keyboards are specially designed for a natural position of the hands

Ergonomics
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A field of study concerned with healthy, comfortable, efficient interactions between people and machines RSI-repetitive strain injury can be sustained from doing the same thing over and over such as typing. Ergonomically designed keyboards can lessen these injuries

Pointing Devices
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Allows user to point, set the insertion point, or click something to issue a command Mouse
Mechanical  Optical  Cordless
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Other Pointing Devices
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Trackball -variation on a mouse where you move the ball and the device stays still Touchpad -pressure sensitive area that you physically touch to give commands; common on laptops Joystick -lever with a handgrip

Even More Pointing Devices
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Graphics Tablet or Digitizing Tabletinvisible grid of electronic dots that are activated by a pen-like stylus or a puck Touch screens - beams of light emitted from edge of screen can determine when a user touches the screen by the broken beams or can use a light pen Pen based computing -uses a stylus to select items; common in handheld devices

Source Data Automation
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Use of special equipment to collect data at its source Does not require re-keying which eliminates mistakes Three primary areas:
Magnetic Ink Character Recogniton (MICR)  Scanners  Other Optical Methods
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MICR
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Uses a machine to read characters written in an ink made of magentized particles Common example is check numbers at the bank MICR inscriber writes information using the special ink

Scanners
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Optical scanners, now just scanners, convert text or drawings into machine readable format Using Optical Recognition, a light beam scans the item and changes it into electrical impulses for processing Common example is the bar code reader

Document Imaging
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Process of converting paper copies to computer copies Can be stored on disk instead of file cabinets Less expensive More efficient

Types of Scanners
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A flatbed scanner scans one sheet at a time by laying the sheet face down on the bed of the scanner Sheetfed scanner use motorized rollers to feed the document across the scanning mechanism Handheld scanner-portable device that requires users to pass the scanning element over the item to be scanned

More Optical Recognition Methods
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Optical mark recognition (OMR)searches for and recognizes marks such as a scantron test Optical Character Recognition (OCR) – uses a wand reader to scan and process standardized letters (OCR-A) many times on things such as sales tags

Some More Optical Recognition Methods
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Bar codes-each product has a unique product code (UPC) represented by a pattern of bars Bar code scanner scans the bars using reflected light which is then processed to retrieve product information assigned to that bar code Handwriting Recognition

Voice Input
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Also called speech recognition Speech accepted through microphone and converted into binary Can be used to control the operation of the computer or to enter data through dictation

Two Types of Speech Recognition
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Discrete word systems-limited number of recognized words; must pause between words; very accurate Continuous word systems-allows almost normal rate of speech and recognizes many more words; less accurate; comes in some of the newer application software packages such as Office XP

Digital Cameras
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Image is stored on a chip in the camera Can be viewed immediately without processing Pixels-tiny dots that compose a digital image Resolution measures the quality of the images by the number of pixels per inch Many use removable flash cards for storage Images must be downloaded to a computer by connecting the camera to the computer and transferring the images

Digital Video
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Consists of a series of still images or frames Can be captured by an inexpensive web cam Video capture cards allow you to translate TV and older video into a format your computer can recognize Newer video cameras actually record the video digitally which allows you to transfer video straight to the computer

Output : Information for the User
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Most common form is output to the screen or printer Other types include voice, sound, graphics and even smells

Screen Technology
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Screen is part of the monitor, the housing which also holds the electrical components Screen output is known as “soft copy” because it is not permanent “Hard copy” like a printout, is tangible

CRT
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Stands for cathode ray tube Most common variety of monitor Most are color but some are monochrome, meaning they can only show one color (usually yellow or green) Monochrome are less expensive and used in some business environments

How the CRT works
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Uses a technology called raster scanning An electron beam sweeps across the back of the screen covered in phosphorous that glows when hit by light It doesn’t glow very long so it must be refreshed The scan rate is the number of times the screen is refreshed, generally 75 times per second in a quality monitor

More on the monitor
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Monitor is divded into dots that are individually addressable and can be set to glow at a certain brightness and a certain color Dots are called picture elements or pixels.

Quality of a monitor
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Resolution on a screen is measure of screen clarity and is related to the number of pixels on the screen Higher resolution = more pixels Dot pitch is the space between pixels Smaller dot pitch=sharper image

Graphics Cards
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The Control Unit of the CPU controls the signals sent to the monitor via the graphics card or the graphics adapter board The card is plugged into an expansion slot on the motherboard

Standards for Monitors
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Standards were developed early to define resolutions and colors Most common standard today is SVGA (Super Video Graphics Adapter) Supports a variety of resolutions and over 16 million colors

Video Memory
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High speed form of RAM installed on the graphics card Allows more colors to be displayed on the screen at once Separate from main memory and stores the image temporarily from the CPU

Is bigger better?
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The size of a CRT is called the VIS, viewable image size Not necessarily the spec given at the computer store. A 17” monitor may only have a 16” vis In other words, it measures across the screen diagonally and only includes the glass part More expensive Takes up more space Easier on eyes Good for graphics

Flat panel screens
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LCD or liquid crystal display is used commonly on small devices such as cell phones Getting larger and starting to appear in the desktop market Flat panels maintain their “skininess” even as the screen grows in size unlike CRT which grow deeper as size increases

Flat Screen Technology
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Active matrix-based on TFT (thin flim transistor) Passive matrix uses fewer transistors but produces a brighter image Gas plasma a newer more expensive technology with screen sizes up to 60 inches

Smart Displays
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Based on flat panel technology Runs Windows CE Touch screen Allows users to access other computers Contains own wireless transmitter and processor

Printers
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Produce output on paper Two modes:
Landsacape  Portrait
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Two types of printers:
Impact  Non-impact
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Impact Printers
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Print device actually touches or impacts paper Line printers-fast printers usually associated with mainframes. Dot-matrix printers-can print through mulitple forms Overall, slower, lower quality, and don’t last as long

Non-impact printer
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Print device doesn’t actually touch the paper Generally more expensive Higher quality graphics Generally faster than impact printers

Laser printers
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Non-impact printer that uses light to transfer image to paper Normal print 8-10ppm Network print 35-50ppm High end printers print up to 1,000 ppm High quality, usually 600-1200dpi Color laser printers much more expensive

Inkjet Printers
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Spray ink onto page Slower than laser Generally lower quality However, affordable color printing at pretty good quality Three colors combine to make all colors With inkjet and laser, can result in some colors not true color of image

Voice Output
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Speech synthesis allows computer to produce speech as output Voice synthesizers, aka voice output devices or audio response units transfer data in storage to recognizable speech

Two types of synthesis
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Synthesis by analysis-replays recorded human speech as needed. Sounds natural but pace is sometimes awkward Synthesis by rule-creates artificial speech that does not sound like a real human

Music output
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MIDI-Musical Instrument Digital Interface Allows musical instruments and synthesizers to be connected to computer Shares data with computer regarding pitch, length of notes, volume and other musical attributes

Microform
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Computer Output Microform produces small images on microfiche or microfilm Microfilm is a roll or images Microfiche more resembles a card Can store up to 1,000 images per roll or fiche

Combining Input and Output
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Terminal-combines input and output, usually monitor and keyboard Dumb terminal-has no processing abilities and just sends data back and forth to another computer Intelligent terminal-keyboard, monitor, memory and processor that can perform its own processing POS or point of sale terminal used mainly in retail markets. For example, in grocery store bar code scanner with display monitor, receipt printer

Computer Graphics
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Business graphics-charts, graphs, and maps Allow visual presentation of data Easy to spot trends and make decisions

Video Graphics
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Graphics associated with moving images Animations Special Effects Video games

CAD/CAM/CIM
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Computer Aided Design Computer Aided Manufacturing Creates two and three dimensional models Designs products and allows for theoretical testing by software CAM controls production process Computer Integrated Manufacturing is the integration of both CAD and CAM


				
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posted:11/15/2009
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