use the same basic technology as internal hard disks and are used primarily to complement an internal hard disk. Because they are easily removed, they are particularly useful to protect or secure sensitive information.
secondary storage
provides nonvolatile storage, and retains data and information after the computer system is turned off.
density
refers to how tightly these charges can be packed
digital versatile disc or digital video disc (DVD)
are the standard optical discs in PCs. DVDs are very similar to CDs except that these discs can store 4.7 GB (gigabytes)—seven times the capacity of CDs. Optical discs that store movies or software
storage area network (SAN)
is an architecture to link remote computer storage devices, such as enterprise storage systems, to computers such that the devices are as available as locally attached drives.
secondary storage device
provides permanent or nonvolatile storage
sector
wedge-shaped sections.
disk caching
improves hard-disk performance by anticipating data needs.
USB drive
so compact that they can be transported on a key ring. These drives conveniently connect directly to a computer’s USB port to transfer files and can have capacities ranging from 1 GB to 256 GB, with a broad price range to match, also known as flash drive
read-only memory (ROM) disc
are discs that cannot be written on or erased by the user. Optical discs that you buy in a store, such as music CDs, DVD movies, and Blu-ray video games, are often read only.
