Storage

Storage

1. Optical

   • How does it work?
     • Optical devices save data as patterns of dots on a reflective surface.
       • The data is read by a small laser that is fired at the reflective surface. If the laser hits a dot it is reflected back differently.
         • The computer registers this difference and interprets the data differently.
   • How is data recorded?
     • Data is recorded on an optical medium by a laser. The laser is at a higher power and burns dots into the medium, which can be read by a laser at a lower power.
   • Examples
     • Media
       • DVD+RW
         • +RW means rewritable.
           • Data can be added and removed to and from the disc.
         • Non-volatile
       • Blu-Ray
         • Blu-Ray discs can hold much more data than DVDs and CDs.
           • 'Blu' comes from the colour of the laser fired at the disc - it's a blue laser as opposed to the traditional red laser.
             • Using a blue laser allows data to be put closer together, giving the disc a higher capacity.
         • Non-volatile

2. Flash

   • How does it work?
     • A group of transistors wired together so they can retain data.
       • A large 'flash' of electric current is used to force electrons through a barrier and trap them there.
         • This 'flash' gives this type of storage it's name.
   • Examples
     • Solid state drive
       • Called solid state because there are no moving parts.
         • Much faster than magnetic storage or optical storage because it doesn't need to spin a platter or shine a laser at a surface.
       • Non-volatile
     • Memory stick
       • Non-volatile
       • Used to be very expensive.
         • Due to advancements in technology they have become popular.

3. Magnetic

   • How does it work?
     • Tiny dots on a magnetic surface are created, read and erased by electromagnets.
   • Examples
     • Media
       • Floppy Disc
         • Removable, portable and cheap.
           • Almost every PC used to use one.
             • They are now obsolete.
         • Non-volatile
     • Device
       • Hard Disc Drive
         • The dots are arranged in circles on the surface of a plastic, metal or glass disc with magnetisable coating.
         • Lots of platters coated in magnetisable material.
           • Platters spin thousands of times a second so data can be retrieved almost instantly.
             • A small magnetic read/write head floats above platter.
         • Non-volatile