CHAPTER 2 : OUTPUT HARDWARE

2.1.2 OUTPUT HARDWARE

Output Hardware consists of devices that translate information processed by a computer into a form that humans can understand. The two principal kinds of output are hardcopy and softcopy.

Hardcopy refers to printed output while softcopy refers to output that is not tangible. These include data that is shown on a display screen or in audio or voice form.

Devices that output hardcopy include printers, plotters and multifunction devices.

A printer is an output device that converts computer output into printed images. Printers are categorized according to whether or not the image produced is formed by physical contact of the print mechanisms with the paper.

Impact printers form characters or images by striking a mechanism such as a print hammer or wheel against an inked ribbon, leaving an image on paper. For microcomputer users, the most common impact printers are daisywheel and dot-matrix.

Non-impact printers, on the other hand, form characters and images without making direct physical contact between printing mechanism and paper. They are faster and quieter than impact printers because they have fewer moving parts.

Two types of non-impact printers often used with microcomputers are laser printers and ink-jet printers.

A third kind, the thermal printer, offers the highest-quality color printing available with a desktop printer. However, it is seen less frequently because it is expensive, and requires expensive paper. It uses colored waxes and heat to produce images by burning dots onto special paper.

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

The three principal kinds of plotters are pen, electrostatic, and thermal.

Multifunction devices combine several capabilities, such as printing, scanning, copying, and faxing, all in one device.

Softcopy output generally refers to the display on a monitor, the output device that many people use the most.

Display screens or monitors are output devices that show programming instructions and data as they are being input and information after it is processed. On display screens, images are represented by individual dots or picture elements called pixels which are the smallest units on the screen that can be turned on and off or made different shades.

The two main types of monitors are cathode-ray tube and flat-panel displays.

A cathode-ray tube uses a vacuum tube like that in a television set while flat-panel displays are much thinner, weigh less, and consume less power.

Flat panel displays are made up of two plates of glass with a substance in between them, which is activated in different ways.

The three types of technology used for flat-panel display screens are: liquid-crystal display (LCD), electroluminescent (EL) display, and gas-plasma display.

Whether CRT or flat-panel, screen clarity depends on three qualities: resolution, dot pitch and refresh rate. To display graphics, a display screen must have a video display adapter, also called a graphics adapter card, which is a circuit board that determines the resolution, number of colors, and how fast images appear on the display screen.

Video display adapters embody certain standards. The Monochrome Display Adapter (MDA) and Color Graphics Adapter (CGA) are no longer favored. Newer computer displays tend to favor the Video Graphics Array (VGA), Super Video Graphics Array (SVGA) and Extended Graphics Array (XGA).

Other softcopy hardware includes audio-output devices, video-output devices, virtual reality devices and robots.

Audio-output devices include those devices that output voice or voice-like sounds and those that output music and other sounds. These include the voice-output devices which convert digital data into speech-like sounds.

The two types of voice-output technology that exist are speech coding and speech synthesis. 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 produce digitized sounds, ranging from beeps and chirps to music which are all nonverbal sounds. To be able to output sound, the computer must have the necessary software and the sound card, a digital audio circuit board plugged into an expansion slot in the computer.

For musical sounds, the two types of sound-output technology are FM synthesis and virtual acoustics.

In FM synthesis, a synthesizer mimics different musical instruments by drawing on a library of stored sounds. Sounds are generated by combining wave forms of different shapes and frequencies.

In virtual acoustics, instead of storing a library of canned sounds, the device stores a software model of an actual instrument.

Video-output includes videoconferencing, high-definition television and three-dimensional television.

Videoconferencing is a method whereby people in different geographical locations can have a meeting-and see and hear one another-using computers and communications.

High-definition television (HDTV) is a television system that features enhanced video and crisp, clear pictures. These pictures are far superior to any seen on television today.

The other kind of HDTV manufactured is the experimental 3D HDTV. It uses special glasses with polarized lenses, while others used what appeared to be normal screens but these screens employed hundreds of tiny prisms/lenses giving a stunning 3D effect.

Virtual reality is a kind of computer-generated artificial reality that projects a person into a sensation of three dimensional space. It has the ability to recreate physical places and phenomena real to people. It is one of the most exciting applications of computer technology to date.

Virtual reality uses the body’s senses of sight, sound, motion, and touch to simulate real objects or places. To achieve this effect, the following interactive sensory equipment is necessary: headgear, glove, and software.

Robots are automatic devices that perform functions ordinarily ascribed to human beings or that operate with what appears to be almost human intelligence. Robots are of several kinds – industrial robots, perception systems, and mobile robots.

All of these are the objects of study of robotics, a field that attempts to develop machines that can perform work normally done by people.

Robotics in turn is a subset of artificial intelligence, a family of technologies that attempts to develop computer systems that can mimic or simulate human through processes and actions.