CHAPTER 8: DIGITAL STORAGE

STORAGE

• ·         A storage medium is the physical material on which a computer keeps data, information, programs and application.
• ·         Cloud storage is another storage option, in which the actual online storage media used is transparent to the user.
• ·         Capacity is the number of bytes a storage medium can hold
• ·         Items on a storage medium remain intact even when you turn off a computer or mobile device
• ·         Access time measures:

-          The amount of time it takes a storage device to locate an item on a storage medium

-          The time required to deliver an item from memory to the processor

HARD DISKS

• ·         A hard disk contains one or more inflexible, circular platters that use magnetic particles to store data, instructions, and information
• ·         A head crash occurs when a read/write head touches the surface of a platter
• ·         Always keep a backup of your hard disk
• ·         An external hard disk is a separate freestanding storage device that connects with a cable to a USB port or other port on a computer or mobile device

FLASH MEMORY STORAGE

• ·         Flash memory chips are a type of solid state media and contain no moving parts.
• ·         An SSD (solid state drive) vs HDD:

·

SSD	HHD
High price	Low price
Smaller capacity	Big capacity
Short lifespan	Long lifespan
Low power consumption (2W)	High power consumption (7W)

• ·         A memory card is a removable flash memory device that you insert and remove from a slot in a computer, mobile device, or card reader/writer
• ·         USB flash drives plug into a USB port on a computer or mobile device

CLOUD STORAGE

• ·         Cloud storage is an Internet service that provides storage to computer  or mobile device users

OPTICAL DISC

• ·         An optical disc consists of a flat, round, portable disc made of metal, plastic, and lacquer that is written and read by a laser

-          A CD-ROM can be read from but not writable or erasable.

-          A CD-R is an optic disc on which user can write once but not erase.

-          A CD-RW is an erasable multisession disc

-          A DVD-ROM is high capacity disc on which user can read but not write or erase.

-          A DVD-R and DVD+R are competing DVD recordable WORM formats on which user can write once but not erase.

-          A DVD-RW,DVD+RW and DVD-RAM are high capacity rewritable DVD formats.

OTHER TYPES OF STORAGE

• ·         A magnetic stripe card contains a magnetic stripe that stores information
• ·         A smart card stores data on an integrated circuit embedded in the card
• ·         Microfilm and microfiche store microscopic images of documents on a roll or sheet film