Storage Devices and Media

Storage Devices and Media

1. Accessing Stored Data

   • Serial / Sequential Access
     • A Serial Access storage device is one that stores files one-by-one in a sequence.
   • Direct / Random Access
     • A Direct Access storage device is one that stores file so that they can be instantly accessed.

2. Magnetic Storage Devices / Media

   • Hard Drives
     • They can be used to store vast amounts of data. Hard-drives are random access devices.
   • Fixed Hard Drive
     • A hard-drive built into the case of a computer is known as 'fixed'. They are random access.
   • Portable Hard Drive
     • It is one that is placed into small case along with some electronics that allow the hard-drive to be accessed using a USB or similar connection.
   • Magnetic Tape
     • Tapes are used where large amounts of data need to be stored. Magnetic Tapes are a serial access medium.

3. Removable Media Magnetic Discs

   • Floppy Disc
     • Floppy discs are random access devices used for transfer small amounts of data. A removable, portable, cheap, low-capacity storage medium. These are obsolete now.
   • Zip Disc
     • A Removable and portable storage medium. Zip discs are random access devices which were used for data back-up or moving large files.
   • Jaz Disc
     • A removable and portable storage medium. Jaz discs are random access devices which were used for data back-up or moving large files.

4. Optical Storage Devices / Media

   • Read-Only Optical Discs
     • CD-ROM
       • Compact Disc - Read-Only Memory discs. The data cannot be altered. CD-ROMS are random access devices. Used to distribute all sorts of data.
     • DVD-ROM
       • Digital Versatile Disc - Read-Only Memory disc. DVD-ROMS are random access devices.
   • High Capacity Optical Discs
     • Blu-Ray
       • Blu-Ray discs random access devices. Blu-Ray discs are used in the same way as DVD.ROMs.
     • HD DVD
       • High-density DVD. HD DVDs are random access devices. HD-DVD discs are used in the same way as DVD-ROMs.
     • CD-R and DVD-R
       • CD-Recordable and DVD-Recordable discs can have data burnt onto them, but not erased.
     • CD-RW and DVD-RW
       • CD-ReWritable and DVD-Rewritable discs can have data burnt onto them and also erased so that the discs can be re-used.
     • DVD-RAM
       • DVD-Random Access Memory discs are a type of re-writable DVD. DVD-RAM discs are random access devices. Used in many camcorders.

5. Solid-State Storage Devices

   • Flash Memory
     • A type of Electronically-Erasable Erogrammable Read-Only Memory (EEPROM). Flash memory is a non-volatile. Flash memory can be found in many data storage devices.
   • USB Memory Sticks
     • Memory sticks are non-volatile, random access devices. You can use it to move any type of file.
   • Memory Cards
     • Many of our devices need compact, non-volatile data storage. Flash memory cards provide this. Many phones also have extra memory cards to store music, video, photos, etc.
   • Smart Cards
     • Many credit cards, door entry cards, satellite TV cards etc. have replaces the very limited storage of the magnetic strip with flash memory.

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