• Today, every computer features some kind of visual display, but display screens were uncommon until the 1960s.

• Modern display and sound systems make the computing experience a more inviting one. Because of these sophisticated output technologies computers are easier to use, data is easier to manage and information is easier to access.

• These technologies enable us to play games and watch movies, experiences multimedia events and the PC as a communications tool.

4A-2

Monitors• Most common output device• Hardly a moment goes by when you are

not looking at your monitor. People often form opinion by looking at the monitor.

• Two important hardware devices determine the quality of the image - The monitor itself and video controller.

• In general, two types of monitors are used with PCs. The first is the typical monitor that comes with most desktop computers, it looks a lot like television screen and works in much the same way

• 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

Monitors• Cathode Ray Tube (CRT)

– Most common type of monitor– Electrons fired from the back– Electrons excite phosphor to glow– Phosphor is arranged in dots called pixels– Dot mask ensures proper pixel is lit– opaque

Monitors• CRT color

– Phosphor dots arranged in triads– Red, green, and blue dots– Three colors blend to make colors– Varying the intensity creates new colors

Monitors• CRT drawbacks

– Very large – Very heavy– Use a lot of electricity

Monitors• Liquid Crystal Display (LCD)

– Commonly found on laptops– Desktop versions exist– Solve the problems of CRT– Fluorescent lights provide illumination

Monitors• Passive matrix LCD

– Pixels arranged in a grid– Pixels are activated indirectly

• Row and column are activated– Animation can be blurry

Monitors• 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

Monitors• Drawbacks to LCD

– More expensive than CRT– Must sit directly in front of screen– Can be more fragile than CRT

Monitors• Paper-white displays

– High contrast between fore and background• Electro-luminescent displays (ELD)

– Similar to LCD– Uses phosphor to produce light

• Plasma monitor– Gas is excited to produce light

Monitors and Video Cards• Monitors impacts user effectiveness• Monitors should have

– Crisp text– Clear graphics– Adjustable controls– Clear edges

Monitors and Video Cards• Size of monitor

– Measured in inches– Measured diagonally– Actual size

• Distance from corner to corner– Viewable size

• Useable portion of the screen

Monitors and Video Cards• Resolution

– Number of pixels on the screen– Higher number creates sharper images– Higher number creates smaller images

Monitors and Video Cards• Refresh rate• A monitor’s refresh rate is the number of times

per second that the electron guns scan every pixel on the screen. – Number of time the screen is redrawn– Modern equipment sets this automatically– Improper settings can cause eyestrain– Important because phosphor dots fade quickly

after the electron gun charges them with electrons.

– If the screen is not refreshed often enough it appears to flicker, and flicker is one of the main reason causes of eyestrain.

Monitors and Video Cards• Dot pitch

– Critical specification of a colored monitor.– Distance between the same color dots– Ranges between .15 mm and .40 mm– Smaller creates a finer picture and more

detailed images will appear on the monitor.– Dot pitch no greater than .28 mm if monitor

size is 15 inch.– For larger monitor, Should be less than .22

or equal.

Video Cards• The quality of images that a monitor can

display is defined by the video card/video controller/video adapter.

• Device between the CPU and monitor• Better cards result in better output• Removes burden of drawing from CPU• Have their own processor and RAM• Modern cards have up to 512 MB RAM• Capable of rendering 3D images

• Video controllers feature their own built-in microprocessors which frees the CPU from the burden of making the millions of calculations required for displaying graphics.

• The speed of the video controller’s chip determines the speed at which the monitor can be refreshed.

• VRAM is dual ported ,it can send a screen full of data to the monitor and at the same time receive the next screen full of data from CPU.

Ergonomics and Monitors• Eyestrain

– Fatigue of the eyes– Steps to avoid

• Choose a good monitor• Place the monitor 2 – 3 feet away• Center of screen below eye level• Avoid reflected light

Ergonomics and Monitors• Electronic magnetic fields (EMF)

– Generated by all electronic devices– It created during the generation, transmission, and

use of low frequency electrical power.– These fields exist near power lines, electrical

appliances and any piece of equipment that has an electronic motor.

– EMF may be detrimental to health– Steps to avoid

• Keep the computer at arms length• Take frequent breaks• Use an LCD monitor

Data Projectors• Replaced overhead and slide projectors• Project image onto wall or screen• LCD projectors

– Most common type of projector– Small LCD screen– Very bright light– Require a darkened room

Data Projectors• Digital Light Projectors/video projectors.

– A series of mirrors control the display– May be used in a lighted room

Sound Systems• Integral part of the computer experience• Capable of recording and playback

Sound Systems• Sound card

– Device between the CPU and speakers– Converts digital sounds to analog– Can be connected to several devices– Modern cards support Dolby Surround

Sound

• Dolby® surround sound expands on stereo to deliver sound from the sides, behind, and even above you—creating a natural, multidimensional sonic environment based on the science of how humans hear.

• Dolby Atmos® is the latest development in realistic cinema sound. It provides full creative freedom for filmmakers and ensures that you'll hear the soundtracks exactly as their creators intended. 

Sound Systems• Headphones and headsets

– Replacement for speakers and microphones

– Offer privacy– Does not annoy other people– Outside noise is not a factor– Headsets have speakers and a microphone