What is Output Data that has been processed into a useful form

Output device is any hardware component that can convey information to one or more people

Output Devices Display Screens Printers, plotters, multifunction, and microfilm / fiche devices Audio-output devices Video-output devices Virtual-reality devices Robots

Output Hardware

A CRT, for cathode-ray tube, is a vacuum tube used as a display screen in a computer or video display terminal. Images are represented on the screen by individual dots or “picture elements” called pixels. A pixel is the smallest unit on the screen can be turned on and off or made different shades.

Display Screen: CRT

Display Screen: CRT

What determines the quality of a CRT monitor?

Screen resolution

Text created with a smaller dot pitch is easierto read

Refresh rate is speed at which monitor redraws images on screen

Resolution: The clarity or sharpness of a display screen is called its resolution; the more pixels there are per square inch, the better resolution. E.g., 640x480, 800x600, 1024x768, 1280x1024, 1600x1280.

Dot pitch : Dot pitch is the amount of space between the centers of adjacent pixels, the closer the dots, the crisper the image. E.g., .24mm, .27mm.

Refresh rate : Refresh rate is the number of times per second that the pixels are recharged so that their glow remains bright. Typical ranges from 50Hz to 150Hz.

Screen Clarity

Monochrome : Monochrome display screens display only two colors --- usually black and white, amber and black, or green and black.

Color : Color display screens can display between 16 and 16.7 million colors, depending on their type.

Monochrome Versus Color Screen

A video display adapter, also called a graphics adapter card, is a circuit board that determines the resolution, number of colors, and how fast images appear on the display screen.– VGA: VGA, for Video Graphics Array, will support 16 to 256

colors, depending on resolution.– SVGA: SVGA, for Super Video Graphics Array, will support

256 colors at higher resolution than VGA.– XGA: XGA, for Extended Graphics Array, support up to 16.7

million colors at resolution of 1024*768 pixels.

Video Display Adapters

•Contains liquid crystals between 2 sheets of material

•An electric current passes through the crystals causing them to twist, block light waves and create an image.

•Uses less than one third the power of a CRT monitor

•Lightweight and compact (mobile users)

Gas Plasma Monitors

•A layer of gas instead of liquid crystals

LCD Monitors

Desktop Versus Portable Printers:– Desktop printers– Portable printers: transportable versus ultraportable

Impact Versus Nonimpact Printers:– Impact Printers

• Dot-matrix– Nonimpact Printers

• Laser printers• Inkjet printer• Thermal printer

Printer

An impact printer forms characters or images by striking a mechanism such as a print hammer or wheel against an inked ribbon.

The right is a Dot-matrix printer

Impact Printers

Pins strike at the surface of the paper. Advantages:

– Possible to obtain multiple copies by using carbon paper or self carbonating paper.

Disadvantages:– Slow– Poor quality– Noisy – Not possible to print in colour.

Use:– Receipts

Dot Matrix Printer

Inkjet printers spray small, electrically charged droplets of ink from four nozzles through hotels in a matrix at high speed onto paper.

Inkjet Printers

Spray ink on to the paper Advantages:

– Better quality and faster than dot matrix. – Can be in colour.

Disadvantages:– Cannot produce the two copies that a dot matrix can.– Need to change the colour cartridges often.– Cannot hold a lot of paper at one time.– Less copies a minute than laser printers.

Uses:– Applications which require portability and low volume output where changing

cartridges is not an issue. e.g. Small offices and stand alone systems. – Applications which require very high quality output and where speed is not an

issue, e.g. Digital camera applications.

Ink jet printers

A laser printer uses the principle of dot-matrix printers in creating dot-like images. However, these images are created on a drum, treated with a magnetically charged ink-like toner (powder), and then transferred from drum to paper.

Laser Printers

Print in the same way as photocopiers. Powdered ink, called 'Toner' is fused onto paper by heat

and pressure. Advantage:

– Print more copies a minute than a ink jet printer.– Ink lasts for longer so they don’t need to change the cartridges so

often. Disadvantage:

– Expensive to purchase.– Bulky and heavy.

Uses:– Applications which require rapid, high quality and high volumes of

output, e.g. Most offices and schools.

Laser printers

Color printer that produces photo-lab-quality pictures

Many photo printers have a built-in card slot

PictBridge is a standard technology that allows you to print pictures directly from a digital camera

Photo Printer

Generates images by pushing electrically heated pins against heat-sensitive paper

Dye-sublimation printer, (also called a digital photo printer) uses heat to transfer dye to specially coated paper

Thermal Printer

Sophisticated printer used to produce high-quality drawings

Large-format printer creates photo-realistic-qualitycolor prints

Plotter

Voice-output devices: Voice-output devices convert digital data into speech-like sounds. Two types of voice-output technology:

– Speech coding uses actual human voices speaking words to provide a digital database of words that can be output as voice sounds.

– Speech synthesis uses a set of 40 basic speech sounds (called phonemes, the bases of all speech in English) to electronically create any words.

Sound-output devices: Sound-output devices produce digitized sounds, ranging from beeps and chirps to music.

Audio-output Devices

Computer component that produces music, speech, or other sounds

Speakers, earphones, and earbuds are common devices

Audio Output Device

What is a Facsimile (fax) machine?

Device that transmits and receives documents over telephone lines

What is a fax modem?

Modem that allows you to send and receive electronic documents as faxes

Fax

Data Projectors

Fax Machine

•Transmits and receives documents over the telephone line

Multifunction devices

•Printer, scanner, copy machine and fax machine all in one

Other Output Devices

Acronym for basic input/output system, the built-in software that determines what a computer can do without accessing programs from a disk. On PCs, the BIOS contains all the code required to control the keyboard, display screen, disk drives, serial communications, and a number of miscellaneous functions.

BIOS