Teacher Hjh Siti Noor Mazrah bte
Awg Hj Suhut
• Storage devices are devices that can
store data or information.
• There are various type of storage devices.
Different devices are suitable for different
• Data can be stored either in the ‘Internal
Memory’ or on a ‘Storage Devices’.
• The amount of data and instructions that can be
stored is measured in 'byte'.
• This is the way the computer communicates and
stores information. With each keystroke or character
a byte of memory is used.
Bit Smallest unit of data, either a 0 or 1
Byte 8 bits
Kilobyte Assumed to be 1,000 bytes. In reality, it is really
Megabyte 1,000 Kilobytes (1,024 Kb)
Gigabyte 1,000 Megabytes (1,024 Mb)
1. Read Only Memory (ROM)
It is permanent, long-term memory which cannot be
erased or changed in any way
It is also known as “Non-Volatile Memory” because
it doesn’t disappear after the computer is switched
ROM chips instruct the computer how to load the
operating system from the hard drive into the
• Don’t confuse the hard drive with ROM – the hard
drive is an internal backing store (storage device).
01/30/15 Free template from
2. Random Access Memory (RAM)
Temporary, short-term working memory
Only works when the computer is turned on
It is also known as “Volatile Memory” because data
disappears if the power is switched off.
Each time you start a program e.g. MS Word, it is loaded
The amount of RAM influences processing power, speed
and how many programs can run at the same time.
Many computers are now sold with 128 or 256 MB of RAM.
3. Hard Disk
Hard Disks are the main internal backing store usually
found inside computers.
It is a non-volatile storage device. Data is stored on a
spinning disk with a magnetic surface known as magnetic
It can store a large amount of data.
There is also an external hard disk which connected to the
computer system by a USB cable or other means.
It provides additional storage space for the computer
Necessary to support the way your
Far slower to access data than ROM or
Large storage capacity Can crash which stop the computer from
Stores and retrieves data much faster than
floppy disk or CD/DVD
Regular crashes can damage the surface of
the disk, leading to loss of data in that
Stored items are not lost when you switch
off the computer
The disk is fixed inside the computer and
cannot easily be transferred to another
Cheap on a cost per megabyte compared to
other storage devices
1. Floppy Disks
One of the oldest types of portable storage
devices still in use.
Have been around since the 1980s.
Store up to 1.44 Mb of data which equivalent to
around 300 pages of A4 text.
Graphics and WordArt cannot be stored
because there have larger size than the size of
Portable – small and
Not very strong – easy to
Inexpensive Data can be erased if the disk
comes into contact with a
Useful for transferring small
files between home and
Quite slow to access and
retrieve data when compared
to a hard disk
Security tab to stop data from
being written over
Can transport viruses from
one machine to another
Can be used many times Small storage capacity
Many new computers do not
have floppy disk drives
2. Zip Disks
Very popular as a backup medium before CD-
RWs were developed and became cheap
enough for everyone to use.
Look similar to a floppy disk but are a little bit
They can store around 100Mb of data – 70
times more than floppy disk.
Stores more data than a floppy
Almost obsolete now
Compresses data, reducing the file
size, so more data can be stored
Need a separate zip drive to read
Portable More expensive than floppy disks.
3. Magnetic Tape
Useful for large organisations who need to back
up their systems daily to store their data.
It works in much the same way as a video tape.
To find a specific piece of data, you have to start
at the beginning of the tape and continue fast
forwarding until you get to the piece of data that
Therefore it is fairly slow to find and retrieve data.
Relatively cheap per megabyte of
Serial access so can be quite slow
to access data
Can store large amounts of data –
Need a special piece of equipment
to record and read the data on the
Can be set up to do the back up
overnight or over the weekend
4. Compact Disks (CD)
Also known as Optical Storage Devices.
Data is burned onto the surface of the disk
using a laser beam in the CD drive.
A Laser beam is also used to read the data
stored on the disk.
A typical CD can store around 650 Mb of data –
equivalent to 450 Floppy disks.
TYPES OF COMPACT DISKS
(CD Read Only Memory)
(CD Write Once Read Many)
(CD Read Write)
This means that when you
buy the disk, it already has
the data or program stored
on it. You can read it but
you cannot save it.
This means that you are able to
save to this disk one time, so
you can store your data or an
application on it of your choice.
However, once you have saved
onto the disk once, you can
access the data many times but
cannot save onto it again.
This means that you
can save data to
your disk over and
over again, just like
you can with a
Small and portable Fairly fragile, easy to snap or
Very cheap to produce Smaller storage capacity than
hard drive or DVD
Most computers can read
CDs. If there is no CD drive, a
DVD drive can usually read
Slower to access than the
Fairly fast to access the data
– quicker than a floppy disk or
5. Digital Versatile Disk (DVD)
The most common methods of copying and
backing up data at home.
Similar to a CD in that it is an optical device and
that a laser is used to store the data and read
A single sided DVD can store about 4.7 Gb of
DVDs which store data on both sides can hold
over 9 Gb of data.
Very large storage capacity DVDs do not work in CD
Sound and picture quality is
excellent, making them ideal
for storing films with video
There is no single standard of
DVDs are now mass
produced so they are
They can be easily damaged
by breaking or scratching
DVD players can read CDs
6. Flash Memory
Typically small, lightweight, removable and
They consist of a small printed circuit board
which is encased in a plastic or metal casing.
They usually have a removable cap which
covers and protects the part of the stick which
is inserted into a USB port.
Are available from 1 Gb up to 6 Gb.
More compact and portable than floppy disks or
At the moment, the cost per megabyte of
storage is more expensive than floppy
disks, CDs or DVDs
Hold more data than floppy disk and nowadays
often more than a CD
They can be easily lost
More reliable than a floppy disk because they
have not moving parts
The metal part which is inserted into the
USB port can be snapped off if they are
They are being developed with fashionable
looking outer casings and are almost becoming
a ‘fashion accessory’ much in way of a mobile
A particular slide catching your eye?
Clipping is a handy way to collect important slides you want to go back to later.