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Backing Storage Devices

Backing Storage Devices. Difference between Backing Storage Devices and Media A backing storage device is used to read the media. For example –A CD drive

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Backing Storage Devices

Difference between Backing Storage Devices and Media

• A backing storage device is used to read the media.

• For example

– A CD drive is a device

– A CD is the media

Device

Need for backing storage

• Main memory only stores the software and data whilst the computer is using it.

• Backing storage is way of storing the software and data permanently.

• Backing storage has a certain capacity (amount of storage) which is usually measured in megabytes or gigabytes

Hard Disk

• Hard Disks are fitted in almost every computer and can be removable or included as part of the base unit

• Hard Disks stores data using magnetic charge

Compact Disk-Recordable

• CD’s are optical disks which use laser technology to read and write data

• CD-R discs allows you to record data once. Once data is recorded on it, it becomes read only

Compact Disk-ReWritable

• CD-RW discs can be written to and read from many times over

Compact Disk-Read Only Memory

• CD-ROM discs cannot be written to but only read

• CD-ROM’s cannot be used to back up data

Digital Versatile Disks

• DVD’s are optical disks which use red laser technology to read and write data

• DVD-R’s are Write Once Read Many discs

• DVD-RW’s allow users to write data to the disc so they may be used in the same way as a normal hard disc.

• DVD-ROM’s are read only and are excellent for storing movies

Blu-Ray Disks

• Blu-Ray’s are optical disks which use blue laser technology to read and write data

• BD-R’s are Write Once Read Many discs• BD-RE’s allow users to write data to the

disc so they may be used in the same way as a normal hard disc.

• BD-ROM’s are read only and are excellent for storing HD movies

Flash Memory

• Flash memory is a solid state device which means it has no moving parts

• Some flash memory needs a special connector (USB)• Flash memory is used in digital cameras, laptops and some

games consoles• Flash memory is portable and can be used in lots of

different devices

Memory Capacity

Bit Binary Digit – a 1 or 0

Byte 8 bits, eg 11001110 (one character eg the letter A)

Kilobyte 1024 bytes

Megabyte 1024 kilobytes

Gigabyte 1024 Megabytes

Terabyte 1024 Gigabytes

CapacitiesCD 700 Megabytes 700 Mb

DVD Single layer 4.7 Gigabytes 4,813 Mb

DVD Double layer 17 Gigabytes 17,408 Mb

Blu-Ray Single layer

25 Gigabytes 25,600 Mb

Blu-Ray Double layer

50 Gigabytes 51,200 Mb

Flash Drive 4 Gigabytes – 64 Gigabytes

4,096 Mb –

65,536 Mb

Hard Disk 500 Gigabytes

– 2 Terabytes

512,000 Mb – 2,097,152Mb

Magnetic Tape

• Magnetic tape uses plastic tape coated with magnetic material to store digital data

• Capacity will depend on the length of tape being used

Types Of Access

• Magnetic tape uses sequential access– To get to a piece of data you have to fast

forward or rewind

• All other media uses random access – To get to a piece of data the device will

jump straight to it