Backing storage refers to permanent storage devices like hard drives and USB flash drives that are used to save files and data when the computer is switched off. Magnetic storage devices like hard disk drives store data using magnetization on metal disks, allowing for high storage capacities. Hard drives are fixed internally while portable external drives also exist. Magnetic tape is used for backups due to low cost and ability to store terabytes of data sequentially. Solid state devices have no moving parts and include USB flash drives and memory cards used in cameras and phones, providing portable storage up to 512GB. Optical storage technologies like CDs, DVDs use lasers to burn pits and lands encoding data, with read-only, write-once, and rewritable

1. Backing Storage

2. What is backing storage?
• When the computer is switched off, the contents
of main memory are lost unless they have been
saved to a permanent storage device.
• Storage device such as hard drives and USB flash
drives are used to keep a permanent copy of
program and data files.

3. Types of Storage Devices - Magnetic
• Called magnetic storage devices because their
recording surfaces are coated with a material
that enables data to be stored digitally by using
different forms of magnetisation.

4. Hard Disc Drives
• This is a metal disk with a magnetised surfaces
on which data is stored as patterns of magnetic
spots.
• The disks are in sealed units to stop dust and dirt
corrupting data.
• They are usually fixed in the computer, but you
can get portable external drives.

5. Magnetic Tape Drives
• Is mostly used for making backup copies of large
amounts of data.
• Has to wind through other data on the tape to find
the required data.
• This type of access to data is slow and is called
sequential access.
• Can be store several terabytes and is relatively
cheap.

6. Types of Storage Devices - Solid State
• Have no moving parts and are made up entirely
from electric components.

7. USB Flash drives
• The most common form of portable backing
storage.
• Small portable backing storage device with no
moving parts.
• Can store large amounts of data, up to 512 Gb.

8. Memory Cards / SD Cards
• Memory cards are used in digital cameras,
digital video cameras and mobiles phones to
store and transfer data.
• They can have the capacity of 4,8,16, 32 + Gb

9. Types of storage devices - Optical
• Use Laser technology to store and retrieve data
by burning areas on a disc to create pits and
lands to encode data.

10. CD – ROM
• CD-ROM stands for compact disc – Read only
memory.
• It is fast and can store up to 700 Mb of data.
• It cannot be written to – the data is fixed at the
time of manufacture.
• The data is read by a sensor that detects laser
light reflected from the surface of the disk.
• Has one speed, the read speed.

11. CD-R
• Stands for CD – Recordable – it allows you to
record data Once.
• Once the data is recorded onto it, it works just
like a CD – ROM and is read only.
• Has two speeds, Read speed and the write speed.

12. CD-RW
• Stands for CD- Rewritable.
• Record data over and over again.
• Can be used to make backups of large files.
• Has three speeds, one for writing, one for
rewriting and one for reading.

13. DVD-ROM
• Like a CD-ROM it is read only.
• Has a much larger capacity than a CD – ROM.
• Single layer DVD-ROMS have a capacity of 4.7
Gb.
• Double sided, multi-layer DVDs have the
capacity of 17 Gb.
• DVD-R - stands for recordable, and can only be
done one.
• DVD-RW – data to be stored over and over
again.