Download storage-devices

Introduction to computer storage
Computers only understand electrical
signals
• A electrical signal can either be on or off, like a
light switch.
• The computer reads this as either 1 or 0
• 1 is on and 0 is off
• 0011010101001111001110001101011110010
In fact computers are just a collection
of electrical components
So how do we store data on
computers?
• Using a memory stick
• Loading a file from the hard drive
• Inserting a CD-ROM or DVD
All done with 0 and 1 magnetic storage
• On a computer hard drive data is stored using
magnetism
• A magnet has two poles North or South
• North represents 1
• South represents 0
All done with 0 and 1
• The magnetic surface of the hard drive records
thousands of 0 and 1’s which make up the
data.
01010001000010000011111000001111110001
Magnetic surface
Computer hard drive
Magnetic storage
• Optical storage
• CD-ROM’s or DVD’s are called optical drives
they use light to represent data.
• The disc surface is reflective, data is written on
the disc by a laser which burns holes through
the reflective surface.
• A light beam is reflected from the shiny
surface but not reflected if there is a hole.
• Reflected light represents 1
• Non reflected light represents 0
video
Video
Flash memory
Flash memory stores data electronically it uses
tiny electrical components called transistors to
store the data.
Each memory location has a transistor which can
store either a 1 or 0.
Flash memory retains its information when the
power is switched off this is called non volatile.
Examples of flash memory are:-
Flash memory
• USB Memory sticks
• SD cards for Phones and
cameras
• Solid state hard drives SSD
• Mobile phone Sim card
Technical details
• Flash memory is transistor-based and nonvolatile. Flash , therefore, has no moving parts
and information stored on the NAND flash
memory chip remains until you delete/edit
the file.
• NAND flash gets its name from the NAND gate
in Boolean logic.
Technical details
• The flash memory cell acts like a permanentlyopen or closed transistor. Charging is
accomplished by grounding the source and drain
terminals and placing a voltage on the control
gate. When the “floating gate” is charged, it
impedes the flow of electrons from the control
gate to the silicon, and the 0 or 1 is determined
by whether the voltage on the control gate is
blocked or not.
Your task
• To create a PowerPoint presentation which
explains the three different storage method’s
• Show examples of each
• Explain how they work
• Include the following information
• Capacity(how much can it store)
• Speed how fast is it
• and how much does it cost?
• Use the website below to find information
• http://www.igcseict.info/theory/3/index.html
Further research
• SSD or solid state hard drives are now
replacing traditional magnetic hard drives why
is this? Find out why and explain.
• Magnetic storage was developed early on in
the history of computing and is still the main
method of storing data on computer system.
So why were optical and solid state
technologies developed?