Post on 25-Dec-2015
Peter Norton, 6th edition
By: Rena Essa
Lesson 4A: Video and Sound
Most common output device Connects to the video card Categorized by color output:
Monochrome One color with black background
Grayscale Varying degrees of gray
Color Display 4 to 16 million colors
3
1.Cathode Ray Tube (CRT)Most common type of monitorElectrons fired from the backElectrons excite phosphor to glowPhosphor is arranged in dots called pixelsDot mask ensures proper pixel is lit
2. Cathode Ray Tube (CRT)Phosphor dots arranged in griadsRed, green, and blue dots
Three colors blend to make colors Varying the intensity creates new colors
CRT drawbacksVery large Very heavyUse a lot of electricity
3. Liquid Crystal Display (LCD)Commonly found on laptopsDesktop versions existSolve the problems of CRTFluorescent lights provide illumination
2 types of LCD Monitors: 1.Passive matrix LCD
Pixels arranged in a grid Pixels are activated indirectly Row and column are activated Animation can be blurry
2 types of LCD Monitors: 2. Active matrix LCD
Each pixel is activated directly Pixels have 4 transistors One each for red, green, blue One for opaqueness Transistors arranged in a thin film Animation is crisp and clean
Drawbacks to LCDMore expensive than CRTMust sit directly in front of screenCan be more fragile than CRT
4. Paper-white displaysHigh contrast between the monitor’s white
background and displayed text or graphics.
5. Electro-luminescent displays (ELD)Similar to LCDUses phosphor to produce light
6. Plasma monitorGas (neon or xenon) is excited to produce
light
Monitors impacts user effectiveness Monitors should have
Crisp textClear graphicsAdjustable controlsClear edges
Monitors Specification:1. Size of monitor
Measured in inchesMeasured diagonallyActual size
Distance from corner to cornerViewable size
Useable portion of the screen
2. ResolutionNumber of pixels on the screenHigher number creates sharper imagesHigher number creates smaller images
3. Refresh rateNumber of time the screen is redrawn Improper settings can cause eyestrain
4. Dot pitchDistance between the same color dotsRanges between 0.15 mm and 0.40 mmSmaller creates a finer pictureShould be less than 0.22
Device between the CPU and monitor Better cards result in better output Removes burden of drawing from CPU Have:
processor RAM
Modern cards have up to 512 MB RAM
Capable of expose 3D images Controls how things look on-screen
Eyestrainweakness of the eyesSteps to avoid
Choose a good monitor Place the monitor 2 – 3 feet away Center of screen below eye level Avoid reflected light
Electronic magnetic fields (EMF)Generated by all electronic devicesEMF may be harmful to healthSteps to avoid
Keep the computer at arms length Take frequent breaks Use an LCD monitor
Replaced overhead and slide projectors Project image onto wall or screen Two types:
LCDDLP
Two types:1.LCD projectors
Most common type of projector Small LCD screen Very bright light Require a darkened room
2. Digital Light Projectors (DLP) A series of mirrors control the display May be used in a lighted room
Integral part of the computer experience
Capable of recording and playback Sound card
Device between the CPU and speakersConverts digital sounds to analogCan be connected to several devicesModern cards support Dolby Surround
Sound
Headphones and headsetsReplacement for speakers and microphonesOffer privacyDoes not annoy other peopleOutside noise is not a factorHeadsets have speakers and a microphone
Chapter 4seeing ,Hearing and printing data
Lesson 4B:Printing
Impact printersGenerate output by striking the paperUses an inked ribbon
Non-impact printersUse methods other than forceTend to be quiet and fast
Impact printer: Dot matrix printers
Impact printer Used to print to multi-sheet pages Print head strikes inked ribbon Speed measured in characters per second. Two Types:
Line printersBand printers
Non impact printers:1. Ink-jet printers
Non-impact printer Inexpensive home printer Color output common using CMYK Cyan, Magenta, Yellow, Black Cyan : blue, Magenta :ارجواني Sprays ink onto paper. Speed measured in pages per minute. Quality expressed as dots per inch.
2. Laser printer Produces high quality documents Color or black and white Print process
Laser draws text on pageToner sticks to textToner melted to page
Speed measured in pages per minute Quality expressed as dots per inch
3. All-in-one peripherals Scanner, copier, printer and fax Popular in home offices Prices are very reasonable
Determine what you need Determine what you can spend Initial cost Cost of operating Image quality Speed
Special purpose printersUsed by a print shopOutput is professional gradePrints to a variety of surfaces
Photo printersProduces film quality picturesPrints very slowPrints a variety of sizes
Thermal wax printersProduces bold color outputColor generated by melting waxColors do not bleed Operation costs are lowOutput is slow
Dye sublimation printersProduces sharp imagesVery high qualityColor is produced by evaporating inkOperation costs are highOutput is very slow
PlottersLarge high quality blueprintsOlder models draw with pensOperational costs are lowOutput is very slow