Backing Storage

Learning Intentions

To Understand: Different types of Backing Storage Their relative advantages / Disadvantages Their relative capacities

Backing Storage

Backing Storage Devices are hardware which is used to store programs and data permanently onto Backing Storage Media.

Computers need backing storage because data in Main Memory is lost when the computer is switched off.

Backing Storage

Device Tape Drive Floppy disk drive Hard Disk drive CD-ROM drive DVD-ROM drive CD Rewriter drive CD Rewriter drive DVD Rewriter drive DVD Rewriter drive USB Flash drive

Media Magnetic tape Floppy disk Hard Disk CD-ROM DVD-ROM CD-Recordable CD-Rewritable DVD-Recordable DVD-Rewritable Flash ROM

Magnetic Tape

Still used to hold high quality audio.Now widely used as a backup system for

computer data.Capacity depends on the length

of tape but usually between 10Gb and 100Gb.

Data is often compressed.

Floppy Disk

Plastic coated with a magnetic material.Easily damaged by heat, magnetism etc –

data should be backed up.Can be write protected - stops accidental

over-writing.Capacity id 1.44Mb.

Hard Disk

Hard disks covered in magnetic material.

Several disks in a platter.

Rotate very fast.Read/Write heads

copy data to disk and read from it.

Hard Disks

If heads collide with the disk, this is called crashing.

This could cause all data to be lost.

Hold 40Gb – 1Tb

CD ROM

Read Only – can’t be written to. Music CDs

Surface of the disk has Pits and Lands.

A laser shines on these and the reflected light is interpreted as 1 or 0.

Can hold 650 – 700Mb

DVD-ROM

Read only – can’t be written to.

Same technology as CD.

Capacity: 4.7 – 17 Gb.Tracks of Pits &

Lands closer together – smaller pits & lands.

CD – Recordable (CD-R)

Data is written to the disk using a high powered laser.

This high powered laser creates the Pits & Lands.

A lower powered laser is used for playback.

Can only be written to once.Same capacity as a CD-ROM, 650 –

700Mb

CD – Rewritable (CD RW)

Can be recorded onto, erased and re-written to.

Uses different powered lasers to Write data, Erase data and Read data.

Can be re-written a few thousand times.Capacity is 650 – 700Mb.

DVD-R DVD-RW

DVD-R 4.7Gb capacity Similar to CD-R Recorded to once. Different powered

lasers to record and playback.

DVD-RW 4.7 – 9.4Gb capacity. Similar to CD-RW Can be re-written to

thousands of times. Different powered

lasers to record, erase and playback data.

USB Flash Drives

Stands for Universal Serial Bus. They are solid state devices – they have no

moving parts.They use Flash ROM which can be recorded

to thousands of times.Capacity between 2Gb – 128Gb.

Pupil Task

Use the Internet to complete the table on the next slide. www.pcworld.co.uk www.amazon.co.uk www.howstuffworks.com www.apple.com www.argos.co.uk

You can use a Word document in necessary.

Comparison

Media Speed Cost Capacity

Tape

Floppy Disk

Hard disk

CD-ROM

DVD-ROM

CD-R

CD-RW

DVD-R

DVD-RW

Flash ROM