Hardware

Input and Output devices

Input: Any data or instructions entered into the memory of the computer. Input is often send to computer by Input devices.

Input Devices: Hardware devices that allows a user to enter data and instruction into a computer e.g. Keyboard, Mouse, Joystick etc.

Input Devices

Manual Input Devices:

They are used by the people to capture data

Most common devices:

Keyboards

Keyboard:

Most commonly used Manual input devices

It is a set of buttons. Each button has a symbol assigned.

Type-writer like input device which allows the user to input Text, Numbers and Instruction into the computer

Type of keys: Numeric Keypad, Navigation Keys and Function keys

Used to input data into applications

Also used to enter command in the computer

Types of keyboard:

QWERTY keyboard

Standard keyboard is called a QWERTY keyboard because of the arrangement of the letters on the top row keys

It key arrangement is similar to that of a typewriter.

Used to input data into applications

ADVANTAGES AND DISADVANTAGES ARE IN THE TABLE!

Numeric Keyboard

Introduction:

Small keyboard that has numbers

Keys found on the right hand side if the computer

Uses:

Used to enter numbers 0 9 and arithmetic operators (+ and etc.)

Used to input put Personal identification numbers (PINs) in ATM

Used in Lockers and safes

Used in some mobiles

Used in Telephones

Chip and PIN devices have numeric keypad

Advantages:

Easy to input numbers

Faster than QWERTY Keyboards for entering numbers only

Small size so they are easy to fit on a mobile

Disadvantages:

Difficult to enter text and other symbols

Can be difficult to use due to small keys

Typing a text message on a phone with numeric keypad is difficult

Concept Keyboard

Introduction:

Triangle grid of keys

Each key has Pictures, symbols or words printed in it

Uses:

Used in Point of sale (POS), Restaurants etc.

Used in Shops

Used in Fast food restaurants

Advantages:

Easy to use (Young children and People with disabilities can also use them)

Enables fast data entry (As there is no need to type whole command)

Are waterproof

It is tamper-proof (function cannot be changed)

Advantages Of Keyboard

Disadvantages Of Keyboard

It is not necessary to buy keyboard as it is usually supplied with a Computer

Lots of practice required in order to type quickly

Entering data with computer is faster than pointing devices

Typing speed is very slow when compared to the speed of computer

Typist can use it with ease

People with wrist and hand problems can find keyboards painful to use

Easy to use (Just press the keys)

Quite large so they take up lot of desk space

It uses a Simple, Familiar, Reliable technology (same as a type writer)

In public locations, they are prone to vandalism

Easy to input symbols and text using keyboard

Pointing Devices:

Piece of hardware that are used to control a pointer on a screen

They are frequently used with Graphical User Interface (GUI)

Most common types of Pointing Devices

Mouse

Touchpad

Tracker ball

Touchscreen

Joystick

Graphic Tablet

Light Pen

NOTE: ALL THE POINTING DEVICES HAS ALMOST SAME USE

Mouse:

Introduction:

It is a Pointing device which allows a user to control the cursor.

User selects items by pressing \ clicking buttons on the mouse

Helps user to point and access items on a computer

Has two buttons and a scroll

Uses:

Often used to control the pointer in GUI

Used for opening, closing programs and flies

Used for moving and deleting flies

Used to select icons or moving around page

Types:

Optical Mouse

Has no moving part (there is no ball underneath it)

Uses a device that emit and sense changes in light to detect the mouses movement

Mechanical Mouse

Has a small ball underneath

When the mouse moves over the desk the ball roll over a flat surface and detect the mouses movement

Advantages

Disadvantages

Faster to select ions and options when compared to a keyboard

People with wrist and hand problems can find it painful to use

Easy to move a pointer on the screen

Must be cleaned regularly

It is small and it takes less space on the desk

It needs a flat surface in order to work properly

Cheap

When gripped too tightly can cause muscle stain

User-Friendly for computer beginners

Difficult to input text with a mouse

IT is easy and convenient to use with a graphical user interface

It is not accurate enough for drawing

Very little finger movement required to reach buttons

IT can be easily vandalized

People with Disabilities have problems in using mouse

Touchpad:

Introduction:

Touch pad is a smooth, pressure and touch sensitive area next to a keyboard on a laptop. Which helps a user to control the cursor on the screen

Has two buttons with same function as mouse buttons

Uses:

User moves a finger over the touchpad in order to control a pointer

Used for opening, closing programs and flies

Used for moving and deleting flies

Used to select icons or moving around page

Advantages

Disadvantages

Usually requires no desk space as it is built into a laptop

Expensive

Easy and fast one finger control

More finger movement needed than any other pointing device

Least prone to dust

Difficult to use when compared to a mouse

Ideal for portable devices

Found in specific devices e.g. laptops

Are built into laptops so there is no need of a separate mouse

People with wrist and hand problems can find it painful to use

It does not require a flat surface

Some operations are difficult to perform when compared to a mouse. Drag and Drop for example.

It wont get clogged with dirt (as can happen in ball mice) therefore performance is never reduced

Small active area makes precise cursor control difficult

Expensive

Tracker Ball:

Introduction:

It is a stationary pointing device with a ball on its top

It is a Pointing device which allows a user to control the cursor by rotating the large ball with your hand

Tracker ball is similar to mice but the ball is on the top of the device instead in the bottom

Its buttons perform same function as the buttons on the mouse

User selects items by pressing / clicking buttons

Uses:

Helps user to point and access items on a computer

Used for opening, closing programs and flies

Used for moving and deleting flies

Used to select icons or moving around page

Used in control room environment

Some arcade gaming machines use tracker ball to control game characters

Advantages

Disadvantages

It does not need a flat surface to move on

Can be difficult to use for applications needing fine control

Not likely to get damaged as a mouse

It is not accurate as a mouse

The pointer can be positioned more accurately on the screen than with a mouse

More expansive than mice

People with wrist / hand problems can use tracker ball

More finger movement is required to move the ball

Use less desk space than mouse because the user does not have to move the entire device

The ball requires more frequent cleaning than mouse

Requires less arm and hand movement than mouse

Rolling a ball is less like pointing

User may need training since they are not standard equipment

Joystick:

Introduction:

It is a pointing device with a vertical lever mounted on a base. The vertical lever can be moved in all directions

It also has buttons with specific use

Uses:

It can also provide input for motorized wheelchair

Popular device for gaming (Like to control the movement of a vehicle or character)

It is also used for controlling fly-by-wire aircrafts

They are also used for ultrasound scanners in hospitals

Advantages

Disadvantages

It allows fast interactions required in most games

It is difficult to select object accurately on screen with joystick

It is easy to move game characters with joystick

Not as easy to control curser when compared to using a mouse

Very simple to get used to

People with hand and wrist issues can find them painful to use

Can be used by disabled people and young children

Difficult to enter text with it

It is easy to use

Difficult to issue commands to computer using a joystick

It is easier to navigate round a screen using a joystick rather than a keyboard

Touchscreen:

Introduction:

It is an input / output touch-sensitive display

Output of touchscreen show us image on the screen, while its input allows you to interact with objects on the screen (e.g. touch the screen to select an option)

It is sensitive to touch of a stylus or a finger

Uses:

Touchscreen allows a user to input commands into a computer by pressing or touching buttons / icons on the screen

Touch screens are used for self-service tills, e.g. petrol stations

They are often used for information Kiosks (booths) located in department stores, hotels, airports etc.

Used in Mobile phones and PDA

Used in ATMs

Advantages

Disadvantages

Very fast and easy to enter options

Limited number of options available on the screen

No training needed in order to use them (Easy operation)

Expensive compared to other input devices

No extra peripherals are needed except the monitor

Screen can become dirty and full of germs due to people touching it

Allows easy access to commands

Need specialized hardware and software

Difficult to vandalize

Are not suitable for inputting a large amount of data because they require a lot of arm movement

User need no knowledge of computer to operate them

people with disabilities can find them difficult to use

Can be made waterproof and so can be placed in open air e.g. on a station platform

Only items already on the screen can be selected (limited number of options available)

Touch screens are tamper proof

Using touch screens frequently can lead to health problems (e.g. straining of arm

Muscles, RSI, etc.)

Graphics Tablet:

Introduction:

It is a flat, rectangular, electronic plastic board on which a stylus writes or draws

The Operation system uses signals from tablet to work out the position of the stylus on the tablets surface

Each location on the graphics tablet corresponds to a specific location on the screen

Whatever written or drawn on graphic tablet can be seen on a computer screen and can also be save in the in the computer

Uses:

Graphics tablets are used by artists and designers to create and store digital graphics in a computer

It is mainly used for computer aided design and drafting by architects, mapmakers, artists and designers

Advantages

Disadvantages

A stylus can be pointed to different positions on the tablet quickly

A stylus and a graphics tablet normally have to work together, and cannot work separately

Much easier to draw images using a pen than it is to draw them using a mouse

Very expensive when compared to a mouse

Very accurate drawing can be produced

Not useful for some input needs such as entering data into the computer

Useful in countries where drawing and symbols are used instead of text

It may be difficult to match the position and motion of the stylus with those of the cursor on the screen

Enables operator to enter text and to draw pictures

Light Pen:

Introduction:

It is a pointing device that can be used directly with a CRT monitor

It can detect the presence of light

It is quite and old technology which can be used as alternative to mouse, touch screen and graphics tablets

They are used directly by drawing or selecting icons on a computer screen

They work by picking up light from the computer screen and then signaling to the computer exactly where the light was picked up. This allows the computer to draw on the part of the screen where the pen picked up the light

Uses:

Can be used as a pointing device

It is used for selecting objects

Can be used for direct drawing onto a CRT screen

Light pens are used by health care professionals (such as doctors and dentists) and aided design work

Advantages

Disadvantages

Using a light pen is more direct and precise than using mouse

Light pens normally requires a specially designed monitor to work with

Light pen is also convenient for applications with limited desktop space

Not as accurate as a graphics tablet when used for producing drawings

No typing skills are required for the user to operate them

Need much software to make it versatile

More accurate when used for pointing

Can be quite uncomfortable to use

Very small

Image Capture Devices:

The devices for obtaining a digital image from a vision sensor

Types:

Scanners

Digital camera

Digital Video Camera

Scanner:

Introduction:

It is a light sensing input device that converts printed text and graphics into a digital form that can be further processed by a computer

A scanner creates a digital photograph of a paper document

Many scanners also include OCR software, which can convert an image of text into a text file that can be edited

How it works:

Scanners reflect light off the hard copy in order to capture an analogue image of the document. The scanner then converts the received analogue data into digital format and then send the data into the computer which can be further processed.

Types:

Flatbed scanner

It works like a copy machine except that it creates a file of the document rather than a paper copy

The user places the paper document on the flat sheet of glass called the platen

It is larger, more expensive and less portable than handheld scanner

Handheld scanner

It can be manually passed over the image to be scanned

It is a portable device which we can use to copy an image from paper to our computer

They are ideal for capturing small images such as signatures and logos

It is smaller, less expensive and more portable than flatbed scanner

Uses:

Scanners are mainly used for image processing, which consists of capturing, storing, analyzing, displaying, printing and manipulating images

Are used to enter information on paper

Used to scan hard copy / printed documents into a computer

Photos can also be scanned into the computer

Advantages

Disadvantages

Very fast to enter hard copies into the computer

Scanned images are usually of lesser quality than the original document

Very easy to scan and store documents and images into computer

Scanned image can take up lot of disk space

Damaged photos can be scanned into the computer and stored

A Scanner is best for two-dimensional objects only

A scanner with OCR software can work as an OCR system

Digital Camera:

Introduction:

A digital camera takes pictures and stores the images digitally, rather than on traditional film.

They use flash, memory card, floppy disk and compact disc to store images

Most digital cameras have a built-in-screen

Digital camera image quality is measured in Megapixels. These are number if dots that make up the image

Most digital camera also capture video and sound as well as images

Almost all modern mobiles have built-in digital camera

Uses:

Used to capture digital images

Can be used for making videos

It can also capture sound

Advantages

Disadvantages

Save money for buying films

Digital camera are more expensive than ordinary films

Image can be reviewed

Photo printing cost is higher than that of ordinary film cameras

Unwanted images can be deleted

Camera users need to have computer skills to be able to transfer and print digital photographs

Image can be viewed on computer

Not all digital cameras produce high-quality image as traditional cameras

Film is not required which means producing photo is much quicker

Artistry of traditional photography us being lost

Memory cards can store thousands of photographs

Images can be transferred using Bluetooth

Web Cameras:

Introduction:

Web cameras are similar to digital cameras in there functions but they are directly connected to a computer and do not have memory storage

Web cam can produce both images and video

Images and videos are sent directly to the computer

Many modern computing devices (such as laptop) come with built-in-web cams

Uses:

Used for video conversation

Can be used as a security camera

Sometimes used to allow drivers to view the traffic conditions on the roads

Sued by parents to keep an eye on their children when they are in another room

Advantages

Disadvantages

Allow a long-distance face-to-face conversation

The image / video quality can be poor

Video conference business meetings and job interviews can be conducted very cheaply over a long distance

They dont have their own storage

Parents can keep an eye on their children

Are usually in fixed position (such as those on the portable devices) so cannot be easily moved

Can be left running constantly which makes them useful as security devices

Sound And Music Capture Devices:

Devices which can capture sound

Common Types:

Microphone

Microphone:

Introduction:

Microphones are used to input analogue sounds into a digital computer

The job of the microphone is to input analogue sound signals into the computer where the sound card which has ADC will convert analogue sound into digital signals. One Digitized, the sound can be stored and used by the computer

Speech recognition software ca recognize spoken words in a stream of sound data and convert them to text. It will be help full for those who are unable to type. But this software can be unreliable

Uses:

Used to input sounds \ speech

Used in voice recognition software e.g. converting speech into text

Hand-free mobile phones use a microphone to allow people to hold conversation without using hands

Used along with headphones in gaming so the gamers can talk to each other

Advantages

Disadvantages

Faster to read in text than to type it in using a keyboard

Sound files can take up a lot of computer storage speed

People with hand problems who cannot use keyboard can use microphone

Speaking words into a word processor is not as accurate as typing

It makes drivers safe as the drivers do not need to take their hands off the steering wheel in order to use their mobile phone

Background noise can interfere with voice recognition system

Microphone are very cheap to buy

Remote Control:

Introduction:

It is a small, hand-held device with a relatively small number of labelled command buttons

When the button is pressed the remote control sends a coded infrared or radio signal to the equipment

Uses:

Home entertainment system use remote controls. E.g. TV, DVE players

Industry uses remote control to operate machinery that might be too dangerous to get near to. E.g. Cranes with heavy loads

Advantages

Disadvantages

Device can be operated with having to go to them.

People with limited hand movement can find them difficult to use

Useful for people with disabilities as then do not have to move to operate them

The infra-red signal between the remote control and the device can be blocked

They can operate devices that are in an unsafe environment

It makes people lazy as they dont have to move

Devices and Methods for automatic data capture:

Devices and methods which can capture data without human involvement

Examples:

Optical character Recognition (OCR):

Optical Mark Reader (OMR)

Magnetic Ink Character Recognition (MICR)

Barcode Reader

Radio-Frequency Identification (RFID)

Magnetic Strip Reader

Smart Card Reader (Chip and Pin Reader

Biometric

Handwriting Recognizer

Optical Character Recognition:

Introduction

OCR consist of a scanner along with special software

It allows us to scan text on paper (hardcopy) into a computer. Once onto the computer, OCR software converts the scanned text into a digital format. Once converted to digital, the text can be used in programs such as word-processors, presentations, and websites

Uses:

Used in the processing of passports and identity cards

OCR is also used in the process of digitizing books

Also used in scanners

Advantages

Disadvantages

Very fast way of entering hard-copy text into a computer

The system can have difficulty in reading handwriting (especially if it is messy)

Cheap

Not 100% accurate

Avoid typing errors as the process is automatic

As it is not accurate, information needs to be manually checked for errors

It can read neat handwriting

Checking for errors is time consuming

Hard copies of documents can be read directly into a computer without retyping

User needs training to operate them

The character converted can be later edited by word processing software

Optical Mark Reader:

IT can read hand-drawn marks such as small circles or rectangles made on pre-printed forms in certain places

The OMR reader first reads the answer key sheer to record the correct answers based on the pattern of light and then reads the reaming documents and match their patterns of light against the answer key sheet

Uses:

Used to read shaded areas on documents

Used to read multiple chose examinations

Used to read Lottery tickets

Advantages

Disadvantages

Extremely fast way of inputting information into a computer

Forms need to be accurately designed to make sure that the mark / shading are in correct position to be read by the device

Very accurate

If forms have been incorrectly filled in they cannot be read properly

Can save money as there is no need to employ worker to enter form information into a computer

Can only read shaded areas (Cannot input or read text)

Has better recognition rate than OCR

Forms can jam in the machine as they are fed through

Large volume of data can be collected quickly and easily

OMR needs to be reprogrammed for each new document design

OMR readers are slow

The person putting the marks on the document must follow the instructions

Folding or dirt on a form may prevent the form from being read correctly

Magnetic Ink Character Recognition (MICR)

Introduction:

It is a system which can read information printed in a special ink

It is used to read the account number on the cheques. Then converts it to a form the computer can understand. The converted information is then send the computer so the cheque can be processed.

Uses:

They are mainly used to process cheques

MICR can also read customer account number and Bank sort-code

Advantages

Disadvantages

Cheques can be processed very quickly (up to 300 per minute)

Only a limited number of different characters can be read

Greater security than OCR because Special ink character cannot be changed

It is expensive

No manual input so lees errors

Magnetic Ink which it read is also expensive

Information can still be read even if someone writes over the magnetic ink characters

It is reliable

Barcode Reader:

Introduction:

Barcode reader uses laser beams to read bar codes

It reads a bar code by using light patterns that pass through the bar code by using light patterns

Once barcode has been scanned, a computer can read the information stored in the barcode and access details about the product that are stored in a database

Uses:

Used in supermarkets and stores where goods are marked with a barcode

They are used in libraries to scan library cards and read ISBN numbers on books

They are used in keeping track of packages that are being delivered to diffident locations

Also used in organizing luggage in airports

Advantages

Disadvantages

The process of data entry is fast and accurate

A barcode reader may misread a barcode if there is any or mark on the code

Barcode can be printed by normal printing methods

Only numbers can be coded

No need to write down price of the item on it

It need specialized software

Easy way of gathering information

Quite an expensive way of gathering information as each item need a barcode

Very accurate as there is no manual typing

It is also expensive

Enables automatic stock control

Bar code can be swapped on items which means that people may pay less for more expensive items

Radio-Frequency identification (RFID):

Introduction:

Radio-frequency identification (RFID) is the wireless use of electromagnetic fields to transfer data, for the purposes of automatically identifying and tracking tags attached to objects. The tags contain electronically stored information

With RFID tags we can reliably identify objects and track there movement

Magnetic Strip Reader:

Introduction:

Reads information from magnetic strips found on bank cards, membership cards and hotel door cards

Data on the card strip is read by passing the card through the magnetic strip reader. The magnetic strip then sends data from the card into the computer for processing

Uses:

ATMs use these readers to process the information on the bank cards

EFTOPS (Electronic Funds Transfer Point of Sale) use the readers to transfer customers money from their bank account when they purchase goods in stores

Hotel rooms sometime use them in place of door keys

Advantages

Disadvantages

Entering data is very fast. You just swipe the card through the machine

The magnetic stripe on the card can only hold a small amount of data

No data entry errors as no typing is involved

The cards need to be in contact with the reader in order to be used

The stripes on cards are not affected by water and are not easily damages

If by any possibility the card is damaged than all the data is gone

Data held on the card cannot be read by eye so bank details etc. are safe

Magnetic stripes on the cards are easily duplicated (Known as card cloning)

Easy to write fresh data onto the strip

It is not so serious if the guest leaves without returning the keycard, as the code ceases to be valid

Smart Card Reader (Chip And Pin Reader):

Introduction:

These allow people to pay for goods and services electronically at EFTPOS (Electrical funds transfer point of sale) terminals

The chip and pin reader works by inserting a bank / credit card into a slot and then entering a PIN (Personal identification number)

If the correct PIN is entered, the cost of goods / services will be taken from the card holders bank and transferred to the companies (Restaurant, Store etc.)

Uses:

Used to make secure payments for goods / services in stores

can be used as access cards for buildings and computer

The cards can store e-cash

It can store the holders medical records

Advantages

Disadvantages

Moe secure than magnetic strip readers as the user needs to know the correct PIN

Since the customer types in the PIN, they need to be careful that it isnt read by somebody else, thus giving an opportunity for fraud

Information on the chip is harder to clone (copy) than it is to copy magnetic stripes

It is possible to forget your PIN which means you cannot make payments with your card

Chips can hold more data than magnetic strips

Chip and PIN readers are portable

Chip and PIN readers provide a more robust system than magnetic stripe readers, since the chip does not need to be in contact with the reader

Biometric:

Introduction:

Peoples physical characteristics or behavior are known as biometric data which can be used for the purposes of authentication,

It can reads our unique body parts to recognize us. It can read our Fingerprint or our eyes

Uses:

Used for the purposes of authentication

Used to recognize someone by the unique body parts

Used on lockers

Used for safety purposes

Advantage:

Provide High security

More reliable than Chip and Pin readers and Magnetic strip cards

Handwriting Recognition:

Introduction:

It is a technique which allows a computer system to recognize characters and other symbols written by hand in natural handwriting

The technology is used for identification and also in devices such as PDA and tablet PCs

After one writes on a screen with stylus, the computer turns that persons handwriting into digital text

Uses:

Used in touch screen devices such as Mobiles

Also used in PDA and Tablet PCs

Advantages

Disadvantages

Handwriting recognition works regardless of which language text is written in

Cannot recognize mathematical symbols

It requires a little or no training to use

Only understand linear structure

It has very low system requirements and provides immediate input

IT is very tiring for arms

Handwriting needs to be clear for it to be recognized

Output Devices

Output:Output is data that has been processed into a used form called information

Output Devices:An output device is any hardware component that can be display information to a user. E.g. Printers, Monitors, Plotters, Multi-Media Projectors and speakers

Printer:

A printer is an output device that produces text and graphics on a physical medium such as paper,

Printer information is often called hard copy because the information is exist physically and is more permanent form of output than that on a Monitor

Printing speed of a printer is usually expressed in pages per minute

Printers can be grouped into:

Impact Printer

It forms characters and graphics on a piece of paper by striking mechanism against an ink ribbon that physically contacts the paper. E.g. Dot Matrix Printer

Non-Impact Printer

It forms characters and graphics on a piece of paper without striking the paper. E.g. Laser Printer and Ink-Jet Printer

Factors affecting print Quality:

Dots per inch

It is a measurement of printers resolution indicating how many dots can be placed by the printer in one square inch. The larger the number, the higher the resolution.

Types of Printer

Each type of printer has its own capability of printing. Some types of printers produce high quality prints while others produce low quality.

Print Mode

The printing mode may also affect the quality, For example the draft mode increases the print rate but quality is reduced

Toner:

The quality and amount of toner also affect the print quality

Advantages

Disadvantages

Information produced is permanent

The time to get the printout is slow, when compared with display devices

Paper is wasted for obtaining the output. There is no wastage of paper in Monitors

Printers are generally noisier than display devices

Dot-Matrix Printer:

Introduction:

It is an impact printer that produces printed images with a print head striking mechanism

Most dot-matrix printers use continuous-form paper (It can make carbon copies of a document using special Carbon paper)

A higher number of pons on the print head means more dots are printed, which results in higher print quality

Its speed is normally measured by the number of characters per second it can print. Its speed is usually 30-550 characters per second

How it works:

These printers work by using a set of pins to press an inked ribbon against paper. There are 9-24 vertical column pins in a rectangular print head. When the pin / Ribbon hits the paper a printed dot is left behind. The dots can be arranged to form basic text and images. Different colored ink ribbons can be used to produce colour printouts.

Uses:

They are very robust and can be used in noisy and dirty environments (like garages and warehouses)

Used for printing bills in ATMs and stores

Used in banks

They are also used as cash registers

Used for data logging

Advantages

Disadvantages

Work fine in dusty and dirty environments where laser or inkjet printers could easily be damages

Very noisy so not suitable for an office environment

Carbon copies can be produces using carbonated paper

Very slow to print (slowest of all the types of printer)

Very cheap to buy (Most cheap printer)

Very poor print quality (low resolution)

Very cheap to maintain (repair)

Colour printout is limited

Good for continuous printing

The pins get bend easily

It can print multipart forms

Colour looks faded and streaky

Energy efficient

Heavy and bulky so they take lots of desk space

Reliable (durable)

Ink-Jet Printer:

Introduction:

It is a non-impact printer that that forms characters and graphics by spraying tiny drops of liquid ink onto a piece of paper

Ink-jet printers can produce text and graphics in both black-and-white and colors

Some ink-jet printers can print photo-quality images on any type of paper

Printer resolution is measured in dots per inch

It has a resolution of 300 dots per inch

They have small amount of internal memory (RAM) to store print jobs so printing is done a bit at a time

How it Works:

Inkjet printers work by spraying ink into a page of paper. The ink is held in ink cartridges and there are 4 different colours Black, Cyan, Magenta and yellow. Motors are used to position the ink cartridge over the correct position of the page and to drag the paper through the printer.

Uses:

Good where few print outs are needed e.g. in homes

Often used to print photographs

Also used in offices

They are often used for manufacturing colour filters for LCD TVs

Used for Textile Printing (Printing of Fabrics)

Advantages

Disadvantages

Inkjet printers are generally quiet

Specialized papers are required to produce high quality colour output

fast than dot matrix

The ink cartridges and specialized papers are expensive

They can produce high quality colour output

The ink may smear when printed on ordinary paper

Much cheaper to buy than laser printer

It is prone to clogging and damage

Smaller than laser printers so take up less space

Slow printing rate

Do not produce ozone or other harmful compounds

Ink cartridges dont last long

Very quiet whilst printing

Ink cartridges are expensive to buy

Capable of printing in vivid colour

Printouts can easily smudge if document is not left to dry properly

They take less space than laser printer and dot-matrix printer

ink cartridge can dry out if not used for long time

They require no warm up time

Even one drop of water can cause blurring

Laser Printer:

Introduction:

Laser printers are the non-impact printers which are also known as page printers because they process and store the entire page before they actually print it

They use toner pressed on a page to produce printed documents

The mechanism of how a laser printer works is similar to a photocopier

Most laser printers today can print text and graphics in very high quality resolutions, ranging from 600 dots per inch to 1200 dots per inch (dpi).

They can print text at a speed of four to over thirty pages per minute

They use buffer memory which stores the information for the whole documents before the pages can be printed

How it works:

Laser printer work by using laser beam to draw onto a drum. A special power known as toner is sprayed onto the drum and it sticks to the parts that contain the positive electric charge. The drum is then pressed onto a sheet of paper and the paper is heated (fused) so that the toner is bound to the paper.

Uses:

Very useful for printing where noise levels need to be kept low

Used in good environments where high volume of printing is required

Used for mass production

Used when high quality of printing is required. E.g. used in offices, schools

Advantages

Disadvantages

Laser printers are generally quiet and fast

The initial cost of laser printers can be high

They can produce high quality output on ordinary papers

Laser printers are more expensive to buy than dot-matrix printers and ink-jet printers

They cost per page of toner cartridges is lower than other printers

Environmentally unfriendly as it produce ozone

Toner cartridge can last a long time (Toner is waterproof)

Use more power than inkjets

Laser printers can handle high volumes of printing

They are larger in size compared to other types of printers

Reliable dont breakdown as easily as inkjet printers

Toner is toxic

Cheaper to run than inkjets (low cost per page)

It is expensive to repair

Colour printing is possible

Monitors:

A monitor is an output device that displays information from a computer on a screen

Types:

Thin Film Transistor (TFT)

Liquid Crystal Display (LCD)

Cathode ray tube (CRT)

Advantages

Disadvantages

The output is immediate and visual

The output does not last long, when the display changes the previous output is lost

Thin Film Monitors (TFT):

Introduction:

These are thin flat screened monitors that are commonly seen today

As they become cheaper, these have taken over from CRT monitors as the most popular computer screens

TFTs are used with the newer desktops such as PCs, laptops and mobile phones

How it Works:

TFT screens are made up of thousands of tiny pixels. Each pixel has 3 transistors red, green and blue and each transistors can produce different intensities. This allows huge amount of colours to be produced (16.7 million). A back light is used to shine light onto these pixels in order for the colours to be produced. In order to light a single pixel, tiny windows can be opened and closed to allow the light to pass through and onto the pixel.

Uses:

TFT monitors are mainly used in portable computers like laptops and mobile phones

Are also used by gamers in home

Now a days this monitor is mainly used

Advantages

Disadvantages

Lightweight so they are perfect for portable laptops and wall mounting

Images can appear un clear when viewed from an angle (you have to look straight at the screen for the best image)

They are very thin and do not take up as much desk space as a CRT monitor

Lower picture quality compared to a CRT

They produce much less glare than CRT and so are friendly to eyes

Cannot be used with light pens yet

They use less power than CRT monitors

They produce less heat than CRT

They emit less radiation than CRT monitors

Liquid Crystal Display (LCD):

Introduction:

An LCD is thin screen which has a backlight behind a grid of tiny liquid crystal pixels

They are replacing CRT

How it Works:

An LCD monitor has a backlight behind a grid of tiny liquid pixels. A computer graphics card can supply a stream of digital data to LCD monitor. The DAC in the monitors control programs electronically scans all the pixels and then delivers an individual analogue signal to each pixel. The analogue signal control how much light of a certain colour the pixel allows through from the backlight. The display is formed by light shining through the gird of thousands or even millions of pixels.

Uses:

Used in homes, offices

Used in laptops

Also used in PDAs, Media Players and Mobile phones

Advantages

Disadvantages

They are small and easy to fit on a desk

He image can only be viewed from a relatively narrow range of angels

They are light and easy to mount on walls

They can display a relatively limited range of colour and brightness

They are compact enough to fit to laptops, PDAs, Media players and Mobile phones

Manufacturing defects can cause permanent lit or unlit pixels

There is relatively little reflection of ambient light from the screen

The stability of the display and absence of flicker make for more comfortable viewing

Cathode Ray Tube (CRT)

Introduction:

They are the old, Bulky, Heavy monitors that are still used today (although being used less and less)

There are the least expensive type of monitor

CRT are becoming rare as LCD and TFT monitors are replacing them

How it Works:

CRT produce an image (made up of tiny dots) by firing Electron beams against a phosphor screen. Each dot is colored Red, Green or Blue of different intensities which produces a vast amount of different colours. The dots combine to create millions of different colour shades.

Uses:

CRT are used with light pens to allow drawing to be created on the screen

Used in homes

Used in TVs

Used in Cathode Ray oscilloscope

Used as display device in radar

Advantages

Disadvantages

Can be used with light pens to create drawing on screen

They are very large and bulky with means they take up large amount of desk space

Produces a larger range of colours than TFT monitors

They create a lot of head and have been known to cause fires

The screen angle is better than with TFT

Screen glare when in direct light viewing difficult

Cheaper to buy than TFT

They also need more power than TFT to operate

It has Multiple resolutions

It is more rugged (harder to damage)

Much better viewing angles than most of LCD

Higher refresh rates

Plotters:

Introduction:

They produce hard copies but are capable of printing on a very large pieces of paper (e.g. 3 foot wide by 10 foot long)

Plotters can also produce very large and accurate documents such as blueprints (plans) for buildings

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

Pens can be replaced with cutting tools to produce large signs

Two types:

Flatbed plotter

Drum plotter

Uses:

Used to produce large, accurate drawings

Used to draw Blueprints of Buildings, Maps, Giant posters and adverts

They are ideal for Computer aided design (CAD) technical drawings and architectural design

They are widely used in Architect, Engineering and construction (AEC) and geographical information system (GIS) sectors

Additionally, they are used by adverting agencies and print and design shops

Advantages

Disadvantages

They can produce much larger printouts than other printers

Their print times are very slow

The print quality is extremely high

They are very expensive to buy and maintain

Plotters can also cut out designs for use in sign making

They take up more space than regular printers as they are huge

They are able to work on large sheets

It can print on wide variety of materials including sheet steel, plywood, aluminum etc.

They are efficient, reproducible accurate and fast

They can save all patterns and templates on disk and eliminate the hassle of having to load the same patterns of a plotter

Drum Plotter:

Introduction:

A drum plotter may also be called a roller plotter

It consists of a roller or drum that rotates back and forth to reproduce the image

How it Works:

The Drum Plotter prints by moving a pen on a piece of paper. It can only print simple graphics and it prints very slowly because of the mechanical movement of the pen. The type of pen used affects the speed of the printing. A typical pen uses a cellulose fiber rod inserted through a circular foam tube saturated with ink, with the end of the rod sharpened into a conical tip. The ink pens are held by the robotic drawing arm that moves side to side as the roller, as the roller which holds the paper or material moves back and forth. This results in production of high quality graphics and images.

Uses:

Plotter is used for printing very large graphics and are therefore used in billboards, maps etc.

They are mainly used in medical environments to plot medical information.

Flatbed Plotter:

Introduction:

The flatbed plotter, also known as the table plotter, draws on flat sheets that are spread and fixed on a rectangular flatbed

How it Works:

This type of plotter has two drawing arms, each with its own set of pens. The drawing arms moves over the fixed sheet of material and produce the desired image. Flatbed plotters use a system where the paper is fixed, and the plotter moves a pen up and down, and left and right to draw the required marks on the paper.

Multi-Media Projectors:

Introduction:

They are usually controlled using a remote control

The remote control makes it possible to direct the presentation without the need to be at the computer

Multimedia projectors are often hung from the roof in special brackets

Uses:

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

Used in home cinema system where images from DVDs or televisions are projected to a large screen

Used for advertising

Can be used for playing games

Advantages

Disadvantages

Large-sized picture so provide a clear view

Lower image quality compared to a computer screen

Enhance the viewers experience

Very expensive to buy

It saves space as it is small in size

Cooling fans in the projectors are noisy

It is easy to install

It does not work well in low light

They are available in variety of sizes

The maintenance cost is high as the lamp of a projector needs to be replaced occasionally

Projectors are designed to be highly compatible with laptops, memory cards and other electronic devices

It has either no audio of its own or has very little sound

Remote controls and other features make it easier for the presenter to interact with the projector

It requires more energy

Speakers:

Introduction:

To provide sound output, the computers sound card has a DAC to produce an analogue output. The computer also needs at least one speaker

The speaker allows the user to hear the sound

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

Headphones are a version of speakers for personal use. They are often used in environment where other people should not hear the sound produced. This might be because it would disturb their concentration.

How it Works:

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:

Used to output sound from monitors

Used in home entertainment

Used in TVS

Used by blind people to listen to words on the screen

Can be used to play music files

Advantages

Disadvantages

Everyone in the room can hear the sound

Output from speakers can disturb people trying to work

They can help blind people use a computer because text can be turned into sound

High quality speakers can be expensive

High sound can cause ear damage

Computer Sciences Notes By Samee Arif