SEB070011-Tutorial 5

Storage media	Descriptions	Examples	Advantages
Magnetic disk (i) fixed head (ii) movable head	(i) A fixed magnetic head is an escapement mechanism, that is coupled to the rotary spindle which supports the disk, is free to rotate about the motor axis, causing the disk to precess while the disk is rotating. Thus, there is relative radial movement between the precessing disk and the fixed head, enabling accessing to different data tracks. (ii) A locking mechanism operable during on-times of the magnetic disk apparatus, the locking mechanism locking a movable part of said magnetic disk apparatus during non-use on-times of the magnetic disk apparatus, locking mechanism releasing the locking of the moveable part during on-times when a specific command is issued from the external information processing device, and re-locking the moveable part during on-times again after processing of the specific command is completed, to keep a locking of the moveable part during any of the non-use on-times until a subsequent specific command is issued from the external information processing device.	• Floppy disk • Flexible disk cartridge (FDC)	• Short access time combined with high storage capacities. • Recording is performed in concentric tracks unlike a record where there is only one “track” in a spiral line. • Higher data transfer rate due to the higher in-track recording density in magnetic recording.
Optical disk	A plastic-coated disk that stores digital data, such as music or text, as tiny pits etched into the surface and is read with a laser scanning the surface. Also called laser disk.	• HD • DVD • Blue Ray	• Mass storage capacity (gigabytes) • Mountable/ un-mountable storage units • Low cost per bit of storage • Long media life • High data stability • High speed data recording and playback is disclosed.
Flash memory	• Flash memory refers to a particular type of EEPROM, or Electronically Erasable Programmable Read Only Memory that maintains stored information without requiring a power source. • Flash memory differs from EEPROM in that EEPROM erases its content one byte at a time. This makes it slow to update. Flash memory can erase its data in entire blocks, making it a preferable technology for applications that require frequent updating of large amounts of data as in the case of a memory stick. • Inside the flash chip, information is stored in cells. A floating gate protects the data written in each cell. Tunneling electrons pass through a low conductive material to change the electronic charge of the gate in "a flash," clearing the cell of its contents so that it can be rewritten. This is how flash memory gets its name.	• USB Flash drives • Flash cards	• Compare to traditional hard drive, flash memory is nonvolatile or solid state, meaning there are no moving parts. It's also silent, much smaller than a traditional hard drive, and highly portable with a much faster access time.
Magneto optical disk	• Magneto-optical disks, such as the rewritable optical disk and the recordable disk used with the Mini Disc player, have a special layer, as of barium ferrite, that can be magnetically polarized by a recording head when heated with a laser. • Data or sound may be recorded to and erased from any portion of a magneto-optical disk multiple times. • When writing, a laser is used to heat the material to this temperature and a magnetic head is used to change the polarity of the material to write the bit, like a conventional computer hard drive.	• HP 4.8GB Rewritable Magneto-Optical disk • Magento Optical Disc for Data (RW)	• This system yields precise servo signals, and can eliminate the tracking error signal (TES) and focusing error signal (FES) independently. • Enables integrated head to increase the coupling efficiency of a collimator without the deterioration of optical characteristics. • Longer shelf life • Reliable long term - Supports millions of reads and writes without losing performance. • Enhanced polycarbonate substrate.