Primary, Secondary and Offline Storage Devices

1. By: Teacher Alam Zeb
Teaching O/A Levels and IGCSE since 2000
Taught in Schools:
1.Al-Ansar School Sharjah, UAE
2.Grammar School Dubai, UAE
3. Springfield School Rawalpindi
4. SLS School Rawalpindi
5.Beaconhouse School System Islamabad
6. Roots IVY International School Rawalpindi

2.  Data Storage: Putting data in a known place
which can be read back in future. OR saving
data in a known place for future use.
 Writing Data : Storing data or saving data
 Reading Data : Getting data back also known
as opening
 Backup/ Backing up Data: is making copies
of your data. It helps preventing our data
from losing.

3.  Optical Storage Media: stores data on a disc
as a number of data dots that can be read
using laser light (CD, DVD, Blue Ray)
 Magnetic Media: store data magnetically
because of magnetized surface (Floppy Disk,
Hard Disc, Tape)
 Solid State Media: Hold data on devices that
have no moving parts (Memory stick, Memory
card, SIM card, Smart card)

4. Random Access Memory (RAM):
 It holds running programs, data in use and
Operating System
 It loses its contents when turned off and
called volatile
 It’s contents can be read and written
 It’s contents can be changed by user
 It may hold up to 16GB contents

5. Read Only Memory (ROM):
 It stores information of Hardwares and
manufacturer
 It does not lose its contents when turned off
and called non-volatile
 It’s contents can be read only
 It’s contents can’t be changed
 It is small memory, maximum can be 4 MB

6. Primary Memory:
 Includes RAM, ROM
 Fast memory
 Holds currently in use data and programs
 Volatile memory
 Expensive
 Less Storage Capacity

7. Secondary Memory:
 Includes Had Disk, Floppy Disk, CD, DVD
ROM/RAM, Blue-Ray, Solid State Drive
 Slower in speed
 Store data for future use
 Non-Volatile devices
 Cheaper
 More Storage Capacity

8. Hard Disk:
 Main device in computer to store data
 has magnetic plates
 has read/write heads for reading and writing
 May be 40 GB to 4 TB
 stores system, user’s files and application S/Ws
 +Fast read/write time, huge storage capacity
 -Can be damaged easily, not portable

9. Floppy Disk:
 Old method of data storage and portability
 Uses thin plastic disc
 Disc rotates and heads read and write
 Maximum storage is 1.44MB
 +Cheaper to buy, can be write protected, light
easy to carry
 -Can be damaged easily, low storage capacity,
not available in modern PCs

10. Magnetic Tape:
 Thin strip of magnetic coated plastic which is
wrapped into a reel.
 Data is stored and read serially.
 Less expensive
 Can store up to 185 Terabyte
 Robust
 *Disc rotates and heads read and write
 *Maximum storage is 1.44MB
 +Cheaper to buy, can be write protected, light easy
to carry
 -Less expensive, Can store up to 185 Terabyte,
robust

11. CD ROM:
 Written by manufacturer, can be read only, no
change or deletion allowed. Stores about 800
MB
 Stores movies, audios, videos, S/Ws
 +More data than floppy, less Expensive than HD,
no deletion accidentally, very portable
 -Less capacity than HD, slow data transfer and
access rate, one cannot write into it

12. DVD ROM:
 Written by manufacturer, can be read only, no
change or deletion allowed. Stores about 4.7
GB
 Stores movies, audios, videos, S/Ws
 +More data than CD, less Expensive than HD, no
deletion accidentally, very portable
 -Less capacity than HD, slow data transfer and
access rate, one cannot write into it

13. Blue-ray Disk
 Work like CD ROMs except they use blue laser
rather than red, which can read/write with
high density so more storage. They store 25 GB,
50 GB and 100 GB.
 Can store High definition video, home video
consoles, backup hard drive
 +Perfect for High definition movies because of
more storage, allows fast access of data
reading/writing
 -Very expensive compared to other optical
media, work only with blue-ray player

14. DVD RAM:
 Allows reading and writing at same time, can
record many times, works for years ,can store
4.7 GB (1sided) or 9.4 GB(double sided disc)
 It contains concentric tracks
 Since long lasting, so used for archiving data
 Used in DVD recorder and camcorders
 + Fast access to stored files, offer large storage
capacity, Can read data at same time when it
is written
 -Expensive than Recordable CDs and DVDs,
don’t work in many devices

15. Pen Drive/Memory Stick:
Is portable storage device
It is non volatile RAM
Used mainly for transfer of data
Can also be used for backup
+ Easily portable, plug and play, can
store up to 64 GB, more reliable
-Expensive in price, can be easily lost