Output Devices • Devices that convert machine language into human understandable form. • Output can be in display form, on paper or sound on speakers.
Output Devices • Monitor • Sound System • Printer
Monitors • Monitors are the most commonly used output devices. • A peripheral device with a screen for the visual display of information.
Types of Monitor • Cathode ray tube (CRT) • Flat-panel display
Monitors - CRT Monitors • CRTs are the most common way of displaying images today. • It uses a large vacuum tube called Cathode-Ray Tube.
Monitor Categories Based on Color Display Monochrome: One color= Background, Other Color=Foreground Color: • RGB (Red, Green, Blue) • From 16 to 16 million unique colors.
Flat-Panel Monitors • A monitor that uses an LCD panel or Plasma . • Flat-Panel monitors are lighter in weight and require less power.
Liquid Crystal Display (LCD) Monitor • Most common flat-panel monitor. • It creates images with a special kind of liquid crystal that is normally transparent. • It becomes opaque when charged with electricity.
Two Categories of Liquid Crystal Displays • Passive matrix LCD • Active matrix LCD
Flat-Panel Monitors • Passivematrix LCD uses a transistor for each row and column of pixels. • Activematrix LCD uses a transistor for each pixel on the screen. • Thin-film transistordisplays use multiple transistors for each pixel.
Other Kinds of Monitors • Paper-white display • Electroluminescent (ELD) display • Plasma/gas plasma display
Considerations When Monitor Shopping • Size • Resolution • Refresh rate • Dot pitch
Comparing Monitors - Size • A monitor's size is the diagonal measurement of its face, in inches. • Larger monitors are available, but can be expensive.
The diagonal size (often 17”)
Comparing Monitors - Resolution • It is defined as a sharpness of a screen. • Resolution = No. of pixels on the screen • More the number of pixels, the better the resolution is. • The Video Graphics Array (VGA) standard is 640x480. Super VGA (SVGA) monitors provide resolutions of 800x600, 1024x768 or higher.
Comparing Monitors - Refresh Rate • Refresh rate = No. of times per second that the electron guns scan the screen's pixels. • It is measured in Hertz (Hz) or cycles per second. • Look for a refresh rate of 72 Hz or higher. • It controls flicker. • A slower rate may cause eyestrain.
Comparing Monitors - Dot Pitch • Dot pitch is the distance between pixels. • Closer the dots, crisper the image. • Look for a dot pitch no greater than .28 millimeter.
Viewing Angle • The angle from which the display’s image can be viewed clearly. • CRT Monitors • LCD
Interlaced & Non-Interlaced Monitors Interlaced Monitors: • It scans odd lines in the first pass and in the second pass scans the even lines. • It causes flickering of screen. • Obsolete. Non-Interlaced Monitors: • It scans an entire line of pixels at a time. • No flickering. • Commonly used.
Video Controller • Intermediary device between the CPU and the monitor. • Controls how things look on-screen.
Monitors - Video Controllers • The video controller is an interface between the monitor and the CPU. • The video controller determines many aspects of a monitor's performance, such as resolution or the number of colors displayed. • The video controller contains its own on-board processor and memory, called video RAM (VRAM).
Video Control Board with Monitor Cable VRAM Graphic intensive applications such as games require plenty of VRAM.
PC Projectors • A PC projector connects to a PC and is used to project images on a large screen. • Many PC projectors provide the same resolutions and color levels as high-quality monitors. • Digital light processing (DLP) projectors use a microchip containing tiny mirrors to produce very sharp, bright images.
Sound Systems • Multimedia PCs come with a sound card, speakers, and a CD-ROM or DVD drive. • A sound card translates digital signals into analog ones that drive the speakers. • With the right software, you can use your PC to edit sounds and create special sound effects.
Sound Card • Translates digital sounds into the electric current that is sent to the speakers.
Sound Card • The most basic sound card is a printed circuit board that uses four components: • An analog-to-digital converter (ADC) • A digital-to-analog converter (DAC) • An interface to connect the card to the motherboard. • Input and output connections for a microphone and speakers.