Lecture 4 Output Devices Output Devices Devices that

Lecture # 4 Output Devices

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.

CRT Monitors

Working of CRT

Scanning Mechanism

Monitor Categories Based on Color Display Monochrome: One color= Background, Other Color=Foreground Color: Ø RGB (Red, Green, Blue) Ø 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.

Flat-panel monitors take up less desk space.

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 • Passive matrix LCD uses a transistor for each row and column of pixels. • Active matrix LCD uses a transistor for each pixel on the screen. ØThin-film transistor displays 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”)

Size of Laptop vs. Size of CRT ? ? ? ?

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 640 x 480. Super VGA (SVGA) monitors provide resolutions of 800 x 600, 1024 x 768 or higher.

What happens as Resolution increases…. ? ?

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.

Refresh Rate of Active Matrix LCD vs. Passive Matrix LCD ? ? ? ?

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

Viewing Angle of Active Matrix & Passive Matrix LCD ? ? ? ?

Interlaced & Non-Interlaced Monitors: Ø It scans odd lines in the first pass and in the second pass scans the even lines. Ø It causes flickering of screen. Ø Obsolete. Non-Interlaced Monitors: Ø It scans an entire line of pixels at a time. Ø No flickering. Ø 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.

Projected Screen

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: 1. 2. 3. 4. 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.