Output HardwareComputer and Information Systems

Chapter 5

Output hardware consists of devices that

translate information processed by the computer

into a form that humans can understand.

The computer-processed information consists of

0’s and 1’s, which need to be translated into

symbols that is understandable for people.

Softcopy is the output displayed on the

computer screen in audio or voice form, which is

intangible. When computer display devices readily

available and information must be quickly

accessible, it is best produced as softcopy.

Output hardware is available in two forms:

Hardcopy

Softcopy

Hardcopy is information that has been

recorded on a tangible medium that can be

touched, such as paper or micro-film. When

computer display devices are not readily available

and information has some value over time, it is

best to produce as hardcopy. Hardcopy output

software are printers, plotters and multifunction

devices.

A Printer is an output device that is capable to

printing characters, symbols, and perhaps graphics

on paper. Printers are categorized according to

whether or not the image produced is formed by

physical contact of print mechanism with paper.

Hardcopy Output Hardware

Two categories of printers:

Impact printer forms characters or images by

striking a mechanism and leaves an image on

paper.

Nonimpact printer forms characters and

images without making direct physical contact

between printing mechanism and paper.

For microcomputer users, the most common

types of impact printers are:

Daisy Wheel Printer produce a high quality

print image because the entire character is

formed with a single impact by a print wheel with

a set of characters on the outside tips of wheel’s

spoke.

Dot-matrix printers produce images with a

print head composed of a series of little print

hammers that look like the heads of pin. It is more

effective than Daisy wheel printer and can print

graphics.

Another type of impact printer that is not used

in micro-computer is Line printer which print a

whole line of characters at once.

The types of nonimpact printers often used

with microcomputers:

Laser printers create images on a drum, which

is then treated with a magnetically charged ink-

liker toner, and the image is transferred from

drum to paper. Laser printers are fast, quiet, have

low maintenance requirements and produce high

quality images, including graphics.

Ink-jet Printers form images by spraying tiny

electrically charged droplets of ink (black or

colors) from four nozzles through holes in a matrix

at high speed onto paper. These printers are as

fast as dot-matrix printers, and they are quieter

than laser printers. Most color printing is done on

ink-jets because the nozzles can hold four

different colors.

Thermal Printers use colored waxes and heat to

produce images by burning dots on special paper.

No ribbon or ink is involved. Thermal printers are

costly and require expensive papers. Therefore

they are not used often in jobs requiring a high

volume of output. It is needed for people who

want the highest quality color printing.

Plotters are specialized output devices that can

produce high-quality graphics in a variety of

colors. Plotters are usually useful for creating

maps, and agricultural drawings, although they

may also produce less complicated charts and

graphs. The three principal types of plotters are

pen, electrostatic, and thermal plotter.

Pen Plotter is the most popular type of plotter,

moves between one and four pens across paper to

form images, or the paper moves beneath the

pens.

Electrostatic Plotter uses electrostatic charges

to create tiny dots on specially treated paper. The

paper is then run through a developer to produce

the image which can be four colored.

Thermal plotter is electrically heated pins are

used with heat-sensitive paper to produce images.

Images can be two colored.

Multifunction Printer Technology:

Multifunction printing devices combine several

capabilities such as printing, scanning, copying,

and faxing all in one device.

Softcopy Output Hardware

The Cathode-ray tube (CRT) is the most

popular softcopy output device used with micro

computers. The CRT’s screen is made up of pixels;

the smaller and closer together the pixels are, the

better the image clarity or resolution. The pixels

are illuminated under software control by electron

guns to form images.

Flat-Panel Display, used with portable

computers, are much thinner, weigh less, and

consume les power than CRT’s. Flat panel displays

are better for portable computers or laptops. Flat

panel displays are made up of two plates of glass

with a substance in between them, which is

activated in different ways.

Flat-Panel Display are distinguished in two ways:

1. Substance between the plate of glass – the

three types of flat panel displays each use

different substances between the plates of

glass. They are liquid crystal display (LCD),

electroluminescent display (ELD), and gas-

plasma display.

2. Arrangement of the transistors on the screen

– in active-matrix displays, each pixel on the

screen is controlled by its own transistor. In

passive-matrix displays, a transistor controls a

whole row or column of pixels. The passive

matrix displays are less expensive and use less

power.

Screen Clarity depends on three qualities:

Refresh Rate is the number of times per

second that the pixels are recharged so that

their glow remains bright. In dual-scan

screens, the tops and bottoms of the screens

are refreshed independently at twice the rate

of single-scan screens, producing more clarity

and richer colors.

Dot Pitch is the amount of space between

pixels, the closer the dots, the crisper the

image.

Resolution is the clarity or sharpness of a

display screen. The more pixels there are per

square inch, the better the resolution.

Resolution is expressed in terms of the formula

horizontal pixel X vertical pixel.

Display screens can either be Monochrome or

Color screens and character-mapped or bit

mapped.

Color screen displays between 16 and 16.7

million colors, depending on their type. Most

microcomputers today are sold with color

screen display.

Monochrome screen displays only two colors –

usually black and white, amber and black or green

and black.

Character-mapped display screens can display

only characters. Character-mapped displays are

drawn from prerecorded templates stored in a

video display ROM chip.

Bit-mapped Screen Displays can display

characters and free-form graphics because the

electron beam can illuminate each individual pixel.

To have bit –mapping capability, a computer must

be configured with a video display adapter card.

Video display adapter: A video display adapter,

also called a graphic adapter card is a circuit board

that determined the resolution, number of colors

and how fast images appear on the display screen.

Video display adapters embody certain

standards including video graphics array (VGA),

super VGA, extended graphics array (XGA).

Video graphics array (VGA) will support 16 or

256 colors, depending on resolution.

SVGA or super video graphics array will support

256 colors at higher resolution than VGA.

Extended graphics array (XGA) is high

resolution display, supports up to 16.7 million

colors at a resolution of 1024 X 768 pixels.

Audio output includes voice-output technology

(speed coding and speed synthesis) and sound

output technology (FM synthesis & virtual

acoustics). In the following sections we describe

the hardware devices that enable voice output

and sound output.

Audio Output Hardware

Voice output devices convert digital data into

speech-like sounds. Two type of voice-output

technologies are:

Sound coding: Human voices are used to

provide a digital database of words that can be

output as voice sounds.

Speech synthesis: A set of 40 basic speech

sounds is used to electronically create words.

Sound output devices produce digitized sounds,

ranging from beeps and chirps to music. All these

sounds are nonverbal. PC owners can customize

their machines to greet each new program with

the sounds they want. A sound card, which should

be plugged into an expansion slot in the computer,

is required in making computerized music.

Two types of sound-output technologies are:

Virtual acoustics: Software models of actual

instruments are stored, such as a clarinet.

FM synthesis: A synthesizer is used to mimic

different music instruments by drawing on a

library of stored sounds. Sounds are generated by

combining wave forms of different shapes and

frequencies.