Hard Drive – storage
RAM – memory
Storage, also known as mass media or auxiliary
storage, refers to the various media on which a computer
system can store data.
Storage devices hold programs and data in units called
Memory is a temporary workplace where the computer
transfers the contents of a file while it is being used.
Cache (I, II, III)
(Semiconductor – chip).
Memory Types &
HD, Zip Disk
CD-ROM, CD-R, CD-RW
DVD-ROM, DVD-R 5ms
cheaper than memory
data when the computer is turned off
an important role during startup
needed for output
Storage devices are categorized by:
type of operations they perform
method they use to access the information
technology they use
in the storage hierarchy
Tape Drive –
Floppy Disk Drive –
Hard Disk –
Sequential – Storage devices that read and write
data in a serial (one after the other) fashion
Random-Access – Storage devices that read and
write data without going through a sequence of
Optical Storage –
Magnetic – Storage devices use disks or tapes
that are coated with magnetically sensitive
Optical – Storage devices that use laser beams
to read patterns etched into plastic disks
The three levels of storage hierarchy are:
Online storage – Also called primary storage, it is
made up of the storage devices that are actively
available to the computer system. User action is not
Near-online storage – Also called secondary
storage, it is not readily available to the computer
system. The user performs an action, such as
inserting a disk, to make it available.
Offline storage – Also called tertiary storage or
archival storage, it is not readily available to the
computer system. Devices such as tape backup units
store data for archival purposes.
Capacity – 720 KB to
Access Time – 100ms
Capacity – Up to 80 GB
Access Time – 6 to 12ms
CD ROM / DVD
Capacity – CD-ROM 650
MB; DVD 17 GB
Access Time – 80 to 800ms
A storage device’s performance is measured by:
Capacity – The number of bytes of data that a device can
Access Time – The amount of time, in milliseconds (ms), it
takes the device to begin reading data
Hard disks are high-speed, high-capacity storage devices.
They contain metal disks called platters.
They contain two or more stacked platters with read/write
heads for each side.
Hard disks can be divided into partitions to enable
computers to work with more than one operating system.
A disk or diskette is a portable storage
High-density floppy disks that are commonly
used today store 1.44 MB of data.
Disks work with a disk drive.
Zip disks store up to 750 MB of data and are
not downwardly compatible with floppy
CD-ROM stands for Compact
Disc-Read Only Memory.
CD-ROM drives can not write
data to discs.
They are capable of storing 650
MB of data.
They are used for storing
operating systems, large
application programs, and
Discs can be read and
Discs can only be
written to “once”
CD-R drives are
capable of reading and
Discs can be read and
Discs are erasable
Discs can be written to
CD-RW drives are
reading, writing, and
DVD stands for Digital Video Disc.
DVD technology is similar to CDROM technology.
DVDs are capable of storing up to
17GB of data.
The data transfer rate of DVD
drives is comparable to that of hard
DVD-R and DVD-RW drives have
the ability to read/write data.
Solid state storage devices use nonvolatile
memory chips to retain data.
They do not have moving parts.
They are small, lightweight, reliable, and