Saturday, 20 January 2018

CHAPTER 8 - DIGITAL STORAGE

Storage
A storage medium is the physical material on which a computer keeps data, information, programs, and applications. 

Cloud storage
Another storage option, in which the actual online storage media used is transparent to the user.

Capacity
The number of bytes a storage medium can hold

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

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
(make sure to always back up your hard disk)

An external hard disk
 A separate freestanding storage device that connects with a cable to a USB port or other port on a computer or mobile device

 Memory card
 A removable flash memory device that you insert and remove from a slot in a computer, mobile device, or card reader/writer

Cloud storage 
 Internet service that provides storage to computer  or mobile device users

Image result for cloud storage

Optical disc
 Consists of a flat, round, portable disc made of metal, plastic, and lacquer that is written and read by a laser

Image result for optical disc


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

CD-R is an optical disc on which users can write once, but not erase

CD-RW is an erasable multisession disc

DVD-ROM is a high-capacity optical disc on which users can read but not write on or erase

 DVD-R or DVD+R are competing DVD-recordable WORM formats, on which users can write once but not erase

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


Other types of storage :

Magnetic stripe card contains a magnetic stripe that stores information
 Smart card stores data on an integrated circuit embedded in the card

Radio Frequency Identification (RFID)
The RFID tag consists of an antenna and a memory chip that contains the information to be transmitted via radio waves
 Image result for radio frequency identification

Microfilm and microfiche store microscopic images of documents on a roll or sheet film.





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