1 Introduction to Computers Day 3. 2 Output devices Translate information processed by the computer into a form that human or another machine can recognize.

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Introduction to ComputersDay 3

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Output devices

Translate information processed by the computer into a form that human or another machine can recognize. The two principle kind of output are hardcopy & softcopy .

• Hardcopy refers to a printed output.

• Softcopy refers to the information that is shown on the display screen or is in audio or video form.

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Output devices

There are several ways to produce output

• Text output

• Graphics output

• Sound output

• Video output

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Output devices

Text Output

is simply the alphanumeric characters that make up our language. Text output appearance ranges from typewritten to typeset quality.

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Output devices

Graphics Output

includes line drawings, maps, presentations business graphics, computer-aided design, computer painting, photographic reproduction.

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Output devices

Sound output

ranges from the message beeps produced by the computer system to the human voice to music and other forms of sound

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Output devices

Video output

Photographs (still images) or moving images such as television and videotaped material

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Printer

A printer provides hard copy output on paper. The basic criteria for evaluating printers include:

• QualityQuality of the printed output.

• SpeedSpeed at which printed pages are produced.

• SoundSound levellevel during printing.

• CostCost of printing media (ribbons, cartridges).

• ConservationConservation of paper.

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Impact Printers

Form characters or images by striking a mechanism such as print hammer or wheel against an inked ribbon leaving an image on paper. Make high noise. Now used less.

Non- Impact Printers

Form characters or images without making direct physical contact between printing mechanism and paper.

Printers

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First printing technology.

Early days typewriters were adapted, produced same high-quality output. Cannot change fonts nor can print graphics or colours. Only the symbols available in the printing mechanism can be produced on the paper.

e.g. daisy wheel printer, drum and belt printers.

Impact Printers

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Followed by dot-matrix printers.

Dot-matrix output is produced by printers that use wires in the print head. These wires extend out in different patterns, pressing against the ribbon to print the characters on paper. As this mechanism enables the print control up to the dot level on the paper, the can be used to produce both text and graphics.

Fast, but noisy. Wear out ribbons very quickly.

Impact Printers

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Provide high-quality non-impact printing. Output is created by directing a laser beam onto a drum to create an electrical charge that forms a pattern of letters or images.

As the drum rotates, it picks up black toner on the images and transfers them to paper. The heating process then fixes the toner particles permanently on the paper.

Non-Impact Printers - Laser Printing

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Excellent print quality and font selection.

Fast printing. E.g. 8-500 pages per minute

High quality graphics with colour. High resolution.

Medium level noise, but high cost.

Primary disadvantages are expensivemaintenance and the high cost of tonercartridges.

Non-Impact Printers - Laser Printing

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Inkjet printer transfers characters and images to paper by spraying a fine jet of ink.

Offers nearly the quality of laser printing, but not the speed. Low-cost alternative for high quality printing.

Non-Impact Printers - Inkjet Printing

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It is a specialized output device designed to produce high-quality graphics in a variety of colours. That are especially useful for creating maps and architectural drawings, although they may also produce less complicated charts and graphics.

Type of plotters• Pen plotter• Electrostatic plotter• Thermal plotter

Plotters

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Provides soft copy output. Comes in either monochrome or colour.

• A monochrome display a single colour against a different coloured background, such as green on black amber on black or white on black.

• Colour display can show a variety of colours.

Video Monitor

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Resolution - describes the degreeof details in a video display.

• The higher the resolution the characters and images are sharper and crisper as film image.

• Conventional television display is low resolution as we can see lines, jagged edges and graininess in the image.

Video Displays

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Bit-mapped display offers extremely high-resolution. Bit map means that each dot on the screen, called a pixel (for picture element) is represented by one bit (a 1 or 0) by the computer. (monochrome)

Bit-mapped graphics is the colour version of a bit map display. Each pixel identifies a number (e.g. 1-256 on a 256-colour palette) indicating what colour that pixel should be.

Video Displays

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Video Adapters

• CGA, 320*200, 4

• EGA, 640*350, 16

• VGA, 640*480,16/ 320*200,256

• SVGA, 800*600, 256/ 1024*768,256

• XGA, 1024*768, 65536

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The liquid crystal display (LCD) is a flat-screen display commonly used with portable computers.

Video Displays

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A monitor-keyboard combination.

Has no system unit of its own, but instead uses the facility from a central computer via a communication link.

Mainframes, minicomputers and workstation systems support multiple terminals.

Terminal

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Dumb terminal performs the simplest input and output operations but no processing.

e.g. A bank ATM

Smart (intelligent) terminal may have its own CPU or processing capabilities, as well as built-in disk for storage

e.g. Point-of-sale (POS) cash register

Terminal

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An artificial, three-dimensional reality created by the computer giving the real world-like feeling to the user.

Involves many human senses. Special gloves and stereoscopic eyewear are used.

Pilots being trained in a flight simulator

Virtual Reality