Secondary Storage

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Describe functional charistics

Recap

storage device- any device used to store computer information

Will retain information when the PC is off

2 types of storage

-Main Memory(ROM|RAM)

backing storage (USB)

Hard Disk- most common form of storage.

ROM- stores instructions for booting up

It is Permanent it is not volatile, so is not erased when the computer is turned off this is called Non-volitile

RAM- only temporary memory so when switched off it is lost, this is called Volatile memory

Stand alone device from the computer

can be connected by a port(USB)

shows up in the folder area of the computer.

Use of "drag and drop"

Examples

USB

external HDD

Compact disk

Compact disk - optical

CD-ROM - you can only copy onto it and cannot edit or change it.

CD-R is recordable, can be written and edited but not reused

CD-RW - re-writable and can be recorded over and over again

Digiral Versatile disk(DVD) - can store 17GB of data, equal to 26 CD-ROMs

Bluray is a HD DVD with better sound and image quality

Optical Storage FACTS-

uses reflected light to read data

Surface is covered in dents - light reflects off them- is reflected- 1(on)

if light is not reflected back this gives off the value of 0

easy to store and carry used on rage of devices

long lasting

special drives required

no longevity tests

scratched/damaged

other types of storage-

Magnetic tape- Magnetic is a really cheap method of storing large amounts of data(typically 26GB) and is often used as a 'backing up' data.

Removable media- Magnetic

Memory stick

zip drives

These are solid state memory devices

No moving parts and keeps all data without any power

Flash Cards

Solid state category

uses flash memory

digital cameras/mobiles/music players

small and portable

Non-Volatile- stable data

lightweight

durable

no mechanical problems

SSD

retain their data even when no power

hard wearing and durable and no moving parts

Memory cards/memory sticks etc.

Fast to read data from

durable

no mechanical problems, silent

limited capacity cost per GB stored limited shelf life

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