 Input
 Processing
 Storage
 Output
Storage refers to the media and methods used to
keep information available for later use. Some things
will be needed right away while other won't be
needed for extended periods of time. So different
methods are appropriate for different uses.

Are both measured in kilobytes, megabytes
and gigabytes

With memory the information is stored
electronically on chips

Storage is saved on media, either
magnetically on disks or optically on disks
(CD/DVD)
Magnetic Devices

Magnetic disks come in various sizes and materials. This method
uses magnetism to store the data on a magnetic surface.
◦ Hard Drive
 Consist of one or more magnetic metal platters which are sealed
inside a case.
Step
Measured as:
1. seek
move the head to proper track
seek time
(ms)
2. rotate
rotate disk under the head to the
correct sector
rotational delay
(ms)
3. settle
head lowers to disk;
wait for vibrations from moving
to stop (actually touches only on
floppies diskettes)
settling time
(ms)
4. data transfer
copy data to main memory
data transfer rate
(kbs)
where ms stands for millisecond = .001 second and
kbs is kilobytes per second.


optical disks include CD and DVD discs.
You may guess from the word "optical" that it
has to do with light. You'd be exactly right!
Laser light, in fact. 1's and 0's are formed by
how the disk absorbs or reflects light from a
tiny laser.
How It Works (a simple version)
An optical disc is made mainly of polycarbonate (plastic). The
data is stored on a layer inside the polycarbonate. A metal layer
reflects the laser light back to a sensor.
To read the data on a disk, laser light shines through the
polycarbonate and hits the data layer. How the laser light is
reflected or absorbed is read as a 1 or a 0 by the computer.

Flash drive
USB drive
Memory stick

SD drive


Trivia Fact
SD used to stand
for Secure Digital
but not usually
means ScanDisk
 Devices like digital cameras, digital camcorders,
and cell phones may use CompactFlash, SmartMedia,
These are solid-state devices (no moving parts) that read
and write data electrically instead of magnetically.
Laptop computers use PCMCIA cards, another type of
flash memory, as solid-state hard disks.


Storage is the third step in the
computing cycle.
The fourth and final step is on its
way … in the next slide show!