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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-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