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Monitors

Monitors, commonly called as Visual Display Unit (VDU), are the main output device of a

computer.

It forms images from tiny dots, called pixels or picture

elements that are arranged in a rectangular form. Dots are

usually very tiny and hard to notice them individually.

The sharpness of the image depends upon the number of pixels

(resolution).

Example: Resolution of 1024X 768 (1024 screens dots going across and 768 from top to

bottom)

Graphic cards

Graphics cards are hardware devices that plug into the motherboard and enable the computer

to display images on the monitor.

Graphics cards usually require the installation of software alongside the hardware. The

software instructs the computer how to use the graphics card (Driver software) and also

allows you to alter settings to change image quality and size.

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Higher quality card can produce very clear graphics very quickly. Some computer games

demand advanced display cards and high quality monitor screens.

There are two kinds of viewing screen used for monitors.

Cathode-Ray Tube (CRT)

LCD Monitors / Flat- Panel Display

Cathode-Ray Tube (CRT) Monitor

The CRT display is made up of small picture

elements called pixels.

The smaller the pixels, the better the image

clarity, or resolution.

It takes more than one illuminated pixel to

form whole character, such as the letter ‘e’ in

the word help.

Most screens are capable of displaying 80

characters of data horizontally and 25 lines

vertically.

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ADVANTAGES

1. Highest Resolutions: CRTs run at the highest pixel resolutions generally available.

2. Brightness and Contrast: Produce a very dark black and the highest contrast levels

normally available. Suitable for use even in dimly lit or dark environments.

3. Color and Gray-Scale Accuracy: CRTs produce the very best color and gray-scale.

4. Best for rapidly moving or changing images.

5. Cost: CRTs are less expensive than comparable displays using other display

technologies.

DISADVANTAGES

1. Large in Size

2. High power consumption

Flat-Panel Display Monitor

The flat-panel display refers to a class of video

devices that have reduced volume, weight and power

requirement in comparison to the CRT. You can hang

them on walls

The flat-panel display is divided into two categories:

Emissive Displays - The emissive displays are

devices that convert electrical energy into

light. Examples are plasma panel and LED

(Light-Emitting Diodes).

Non-Emissive Displays - The Non-emissive displays use optical effects to convert

sunlight or light from some other source into graphics patterns. Example is LCD

(Liquid-Crystal Device)

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Screen size

LCD monitors are varying considerably in size and

resolution.

Example: Typical 15- inch screen might have a

resolution of 1024 X 768 pixels and 30 – inch screen

2560 X 1600

ADVANTAGES

1. Compact flat screen

2. Less power consumption.

3. Brightness: Produces very bright images due

to high peak intensity. Very suitable for

environments that are brightly lit.

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Printers

Printer is an output device, which is used to print information on paper (Hardcopy Output)

There are two types of printers:

Impact Printers

Non-Impact Printers

Impact Printers

The impact printers print the characters by striking them on the ribbon which is then pressed on

the paper.

Characteristics of Impact Printers are the following:

Very low consumable costs

Very noisy

Useful for bulk printing due to low cost

There is physical contact with the paper to produce an image

Non-impact Printers

Non-impact printers print the characters without using ribbon. These printers print a complete

page at a time so they are also called as Page Printers.

These printers are of two types

Laser Printers

Inkjet Printers

Characteristics of Non-impact Printers

Faster than impact printers.

They are not noisy.

High quality.

Support many fonts and different character size.

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Laser Printers

These are non-impact page printers. They use laser lights to make pattern of ink on a drum. This

drum then transfers the ink to the paper. And finally heating process fuses the ink to the paper

USES

Businesses use laser printers almost exclusively because they have the reputation of being

reliable while making a quality print product.

Some common uses for laser printers include printing company stationery, making labels, and

creating company fliers and brochures as printing is not messy due to smudging.

ADVANTAGES

Very high speed

Very high quality output (often Black and White)

Give good graphics quality

Support many fonts and different character size

Toner Cartridges last a long time and don’t need to be replaced often.

DISADVANTAGES

Expensive.

Cannot be used to produce multiple copies of a document in a single printing.

Inkjet Printers

Inkjet printers are non-impact character printers based on a relatively

new technology. They print characters by spraying small drops of ink

onto paper forming characters and pictures. Inkjet printers produce high

quality output with presentable features.

Colour printing is also possible. Some models of Inkjet printers can

produce multiple copies of printing.

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USES

Home and small office use

Used to print photographs (often produce colour prints)

ADVANTAGES

High quality printing

High quality colour printing

DISADVANTAGES

Expensive as cost per page is high

Messy due to ink spray and take some time to dry ink after printing( Smudgy)

Slow as compared to laser printer

Ink Cartridges do not last long and so are not suitable for large print jobs

3D Printer

3D printers allow us to print three dimensional solid objects

in almost any geometrical shape.

There are multiple methods to accomplish 3D printing but,

essentially, a special resin is printed in layers until the object

is completed.

3D printers follow digital CAD (Computer Aided Design)

designs which provide the dimensions and shape of the

object being printed.

3D printers are commonly used to print prototypes within industry; prototypes (small-scale

versions of the real product) are built in order to find any product design flaws before it is mass

produced.

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A range of materials can be used when printing including metals, plastics, gold, fabric, acrylic

and porcelain.

USES OF 3D PRINTERS

1. 3D Printing In The Medical Industry 3D printing has been used to print organs from a

patient’s own cells. This means that patients may no longer have to wait a long time for

donors in the future. In the past, hospitals implanted structures into patients made by

hands.

2. 3D Printing In The Automotive Industry: Prototype car models and parts.

3. 3D Printing In The Aerospace Industry: Recently, NASA’s rocket engine injector

made from a 3D printer passed a major hot fire test.

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Plotters

Plotters are output devices used to print copies on a large sheet of paper.

There are 2 different types of plotters-drum and flatbed.

Plotters draw images on the page using colored pens which moved around the paper by a

computer.

USES OF PLOTTERS:

Blueprints of building(plans/designs)

Maps

Giant posters and adverts(like those we see on billboards)

Computer-aided design

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Speakers

Many everyday uses of computers require the user to listen to different types of sound.

For example:

o Listening to music album

o Watching a movie

o Browsing videos on YouTube

o Multimedia encyclopedias

Speakers can be connected directly to a computer or are built into the monitor or casing.

Speakers are analogue and cannot output digital

‘computerized’ sounds.

Digital data from the computer must first be converted

into analogue sound using a sound card.

The analogue sound can then be output via the speakers

and we can listen to it.

USES OF SPEAKERS

Used to output sound from multimedia presentations (like famous speeches etc.).

Used in home entertainment (surround sound etc.).

Can be used by blind people to listen to words on the screen instead of reading.

In order for the computer to output these sounds it requires some sort of speaker system!

Note: Most computers have small built in speakers to alert users when the do something wrong but these can only produce very basic sounds like ’beep’

Speakers can also be used alter the volume of the sounds.

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Can be used to play download music files.

Multimedia Projector or Data Projector

These projects whatever appear on a computer monitor onto a

very large screen so that large number of people can view it.

Multimedia Projectors are usually controlled using a remote

control.

The remote control makes it possible to direct the presentations

without the need to be at the computer.

Multimedia projectors are often hung from the roof on special

brackets.

USES OF MULTIMEDIA PROJECTORS:

Can be used for training presentations to allow the whole

audience to see images from a single computer.

Also used for large scale advertising of new products.

Home cinema system where images from DVD’s or televisions

are projected on a large screen.

Note: Special software called ‘screen readers’ are also needed in order to convert the printed words into sound.

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Control Devices

Control devices are output devices which work together with sensors and commands

from computers in order to control a process.

Data gathered by a sensor is input into the computer which then decides what to do with

the data (processes it).

Once the computer has decided what to do with the data it sends instructions to the

control devices.

The control devices then physically changes something in response to commands

received from the computer.

Remember- Sensors gather ‘measurable’ data from the environment and input it into

the computer. They do not need any human involvement.

Sensors typically gather data such as temperature, pressure, pH etc

Consider this example:

INPUT –A burglar breaks the infrared light sensor on a security system.

PROCESS- This data is sent to a small computer inside a security light

The computer sends instructions to an ‘actuator’ telling it to switch on the

security light.

OUTPUT- The actuator switches on the security light

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ACTUATORS

Actuators take instruction from the computer and then make the ‘physical’ part of the

process happen

Actuators can also physically operate devices such as motors, pumps, switches and

valves.

USES OF CONTROL DEVICES

The table below summarizes the main uses of different control devices.

Remember- each of these control devices are switched on and off by an actuator

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Types of

control

devices

Used in:

Advantages

Disadvantages

Actuators enable a computer to perform

physical tasks in the real world. For example

computers can control a central heating system

or a mechanical digger.

These perform physical operations when

instructed by a computer. This can be

dangerous for people if their presence is not

know by the computer

Do not need to employ people If the computer malfunctions the system will

not work

It is accurate and very quick The software for the control system is

specialist and may cost a lot of money to

develop