Output- Storage Devices - BH

8/13/2019 Output- Storage Devices - BH

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GCSE Information TechnologyGCSE Information Technology

Output Devices & Storage

Computers must have output devices andplaces to store data

The output devices that you are probably

most used to will be the screen, ormonitor,and the printer.


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Output Devices

VDU

Monitor

LCD screens Printers

Dot matrix printer

Ink jet printerLaser printer

Plotter

Speakers


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GCSE Information Technology

Monitor (VDU) A monitor or screen- output device that

displays graphics, text and video.

The picture on a monitor is made up ofthousands of tiny coloured dots calledpixels.

Qualityof theoutput on a monitordepends onits resolution.

Resolution depends on the number of

pixelsthat it can display

Settings are:

640*480, 800*600 (SVGA), 1024*768 (XGA)


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How a Monitor shows colour Three electron gunsfire red, green and blue beams that

light up phosphorous dots on the screen (RGB)

In earlymonitors, each guncould be switched on or offmeant only 8 colours(1 bit per gun)

Latertechnology allowed the guns to vary in intensitymeans 16,777,216 colours(8 bits per gun)


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How a monitor works

CRTor Cathode Ray Tube

An electron beamscans

from the top to the bottom

of the screen Phosphorous dotson

screen glowfor a second as

beam passes over

Very fast repetitionsgive

the impression of constant

picture


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LCD screens (LiquidCrystal Display)

Based on method used by calculators

Used for portable computing

Nowappearing with desktop computers

Take up less room

They dont use much power

Angle of viewing is limited

How they workIt works by controlling the amount

of light passing through crystals.


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Dot Matrix Printer

A dot matrix printer forms characters and graphics on the paper

bypatterns of dots- make up the printout.

Theprint head- made up frompinswhich are pushed out indifferent arrangements to form patterns of dots.

An impactprinter used for multi-part stationery

Continuous stationery

Inexpensiveand cheap maintenance

Noisy

Poor quality

Slowit is a line printerprints a line at a time


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Ink Jet Printer

Printouts are made up ofpatterns of very small dots

Print headhas a set of tiny holesrather than pins. As the print head moves across the paper ink is forced out

through the holesby heatingto form the image.

very quietto operate

Good-qualityprintouts of both graphics and text. Relatively cheapespecially for colour

Maintenance costsare relatively high

Slowit is a line printerprints a line at a time

Can usephotographic paper


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Ink Jet Printer


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Laser Printer

high-qualityprinted output of both text and graphics

quick quiet.

more expensive than inkjet printers and the tonercartridges are more expensive.

suitable for large volume printoutsbecause of their speed.

Colour and A3are more expensive


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How alaser printerworks

Called a page printerbecause it builds up an image of awhole page before printing

A laser beamreads the screen image & sends it to a drum

on the printer The drum is charged and toner is attracted to it As the drum loses its charge, the toner is transferred to the

paper in the form of the page image

A heating process sets the toner on the paper


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Plotter

uses apen to drawthe computer output onto the paper.

Flatbed or drum Paper movement is controlled in one direction

Pen is attached to an arm and moves in the other direction

Some plotters use a set of coloured pensto produce colour output.

Very accurate drawings and are often used in computer aided

design or CAD.

Can give very large sizes

Generallyslowbut speed up to several feet per second


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Sound Computers can output music, voices and

many other complicated sounds

Basic sound can be produced frommotherboard

To be able to output quality sound a

computer needs to have a special circuitboard inside it called a sound card.

Attach speakers or headphones


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Storage Devices

Backing storage- to store programs and data when they are notbeing used or when a computer is switched off.

When programs and data are needed they are copied into main

memory (RAM).

Magnetic storagestores to disk or tape;

Optical storagestores to CD or DVD

Direct accessYou can go direct to the data on your storage

device;

Serial accessyou have to start at the beginning and work your

way through to get to the data that you want


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Hard disk

A platter of circular metal disks coated with magnetic

material and sealedin a hard disk drive inside the computer. Data accessed much more quicklythan data stored on

a floppy disk.

Can store much more data than a floppy disk. Today over

100 gigabytes of data. The heads floatabove the disksand move in and out to

the correct track as the disk spins


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Hard disk (2)

Hard disk platters

Reading heads

Surface of a hard diskshowing tracks and

sectors


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Advantages/Disadvantagesof hard disk storage

Much larger capacity Fastdata access

Direct access

Can become damagedand data lost

Cannot be removed

from the computer


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Tape

Magnetic; tape reels, and cassettes or cartridges.

Large tape reels forbackupon mainframe computers.

Cartridges used to backup copies of the programs and

data on pcs and networks. advantage is that it is cheapand can store large amounts of

data.

Can store very largecapacity

Very cheap

Serial access, therefore veryslow

Vulnerable to magnetic fields


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CD ROM

Optical storage

uses laser CD-ROMs can store approximately 650 megabytes of

data - 400 times more data than an ordinary 3 inch

floppy disk.

a CD-ROM cannot be erased or changed, and no new

information can be saved. Distributing software

Large amount of storage

capacity No accidental deletion

Cheapto produce

Direct access

Not as fast as hard disk

Cannot write to it


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CD-R Optical storage uses laser

Can be written to onceusing a special drive

A more powerful laserpermanently changes a special dye

which allows data to be written to it.

Lower intensity beam used to readthe data

Can be read by ordinary CD drives Used for archivingand small scale distribution


Can only be read to onceso diskis no good if data is no longer

needed

Disk surface is easily damaged

Can take a long time to write to it

Can be read by ordinary

drives No accidental deletion

Cheapto produce

Direct access


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CD-RW

Optical storage uses laser

Can be written to many timesusing same drive

(approx 5000 times)

Can be read by ordinary CD drives Used forphotographsand backup

Disc can be re-used

Uses same drive

Direct access


Disk needs to be formatted

Disk surface is easilydamaged

Can take a long time to writetoit


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DVD Can store minimum of 4.7 gb This is about 2 hours of high quality video or 32 volumes

of Encyclopaedia Britannica + animations and video.

Data packed closer together

Can be made up of 2 layers

9.4 gb Can be double-sided 17 gb

Used for video

Huge storage capacity

DVD drives can read CDs Direct access


older computers may not have aDVD drive

Disk surface is easily damaged

Can take a long time to write toit

More expensive than CD-RW


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DVD R / DVD RW

Same as CD

DVD R can be written to once

DVD RW written to many times


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Flash memory (EEPROM)

Your computer's BIOS chip

CompactFlash(most often found in digital cameras)

SmartMedia(most often found in digital cameras)

Memory Stick(most often found in digital cameras)

memory cards(used as solid-state disks in laptops)

Memory cardsfor video game consoles

Flash memory - fast information storage.It enables ROM tobe electronically changed a block at a time- no moving parts- Units of memory called blocks(roughly 512 bytes).


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Flash Memory Card

Small storage mediumfor text, pictures, audio, video.) - CF card

(CompactFlash), the SmartMedia card, the Memory Stick, and the

MultiMediaCard (MMC). Storage capacities - corresponds to the price.

Storage capacities over 2Gb

Nonvolatile memory, - data is stable on the card, does not need to berefreshed, no moving parts.

Portable, increasing number of small, lightweight and low-power devices.

Advantagesover the hard disk drive: smaller and lighter,

extremely portable,

completely silent,

allow more immediate access,

less prone to mechanical damage.

Capacityless than hard drive

Use digital cameras, palm tops, mobile phones, MP3


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Pen drive/USB flash drive

removable and rewritable

EEPROM erasure region broken up into smaller "fields"

- canbe erased individually without affecting the others Storage capacities typically range from 64 MB to 64

GB

USB ports on almost every current PC and laptop.

to transport and store personal files
http://en.wikipedia.org/wiki/EEPROMhttp://en.wikipedia.org/wiki/File:Usbkey_internals.jpghttp://en.wikipedia.org/wiki/File:USB_Flash_Drive.pnghttp://en.wikipedia.org/wiki/EEPROM


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HD DVD and Blu Ray HD DVD

video recorders and computer games

optical

15 gb Abandoned in 2008

Blu Ray

video recorders and computer games

same physically as CD optical storage,

up to 50 gb.

High definition video storage

Format war between the two won by Blu Ray
http://upload.wikimedia.org/wikipedia/commons/a/a3/Blu-ray_disc_%28BD-RE%29.JPG

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Output- Storage Devices - BH