1. WELCOME
TO OUR
PRESENTATION
Topic: Secondary Storage

2. OBJE C TIVE OF THE PRE SE NTA TION
 To get general idea about secondary storage.
 To obtain information concerning the advantages and
disadvantages of secondary storage.
 To obtain general idea about types of secondary storage.
 To know the causes of using secondary storage.
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3. OVERVIEW
 Introd uction
 What is Second ary Storage?
C reated by H ossain Raju
 The Ad vantages of Second ary Storage
 The D isad vantages of Second ary Storage
 Evolution of Second ary Storage D evices
 Types of Second ary Storage
 Types of O ptical D isk
 Why we use Second ary Storage D evices
 C onclusion
 References

4. INTRODUCTION
Every com puter system consists of a variety of d evices
to store the instructions and d ata required for its
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operation. The instructions and d ata are stored in the
m em ory (storage) unit of the com puter. The m em ory
com ponents of a com puter system can be d ivid ed into
following m ain groups:
 Prim ary Storage (M ain M em ory),
 Second ary Storage (Auxiliary M em ory), and
 Internal Processor Storage.

5. WHAT IS SECONDARY STORAGE?
Second ary storage technology refers to
storage d evices and storage m ed ia that
are not always d irectly accessible by a
com puter. This d iffers from prim ary
storage technology, such as an internal
hard d rive, which is constantly available.
In C omputer Science, “Any m eans of
storing and retrieving d ata external to the
m ain com puter itself but accessible to
the program .”

6. SECONDARY STORAGE (CONT…)
 U sed in a com puter system to overcom e the lim itations of
prim ary storage,

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H as virtually unlim ited capacity because the cost per bit of
storage is very low,
 H as an operating speed far slower than that of the prim ary
storage,
 U sed to store large volum es of d ata on a perm anent basis,
 Also known as auxiliary m em ory.

7. THE ADVANTAGES OF SECONDARY
STORAGE
The ad vantages of Second ary storage are given below:
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 Second ary storage d evices are safe, reliable and perm anent.
 H igh speed storage d evice.
 H uge volum e d ata are stored .
 L ess expensive.
 It is nonvolatile.

8. THE DISADVANTAGES OF SECONDARY
STORAGE
The D isad vantages of Second ary storage are given below:
 While RAM electronic storage d evices are fast, second ary
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storage d evices are slower because they are electro-
m echanical.
 The inform ation on the second ary d evice has to be first
located , then copied and m oved to the prim ary m em ory or
RAM .
 Takes m ore tim e.

9. EVOLUTION OF SECONDARY STORAGE
DEVICES
 The first hard d rive was used in 1 956 which is created by IBM
and whose capacity was 5 M B.
 In 1 971 , IBM introd uced a technology called the floppy d isk,
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 At the beginning of the 1 980s the first optical d evices were
released by Sony and Philips. This d rive can store
approxim ately 650 to 700 of d ata.
 From 1 990 to till now there are m any d evices is created like
card read er, M em ory Stick, M ultim ed ia C ard etc.

10. TYPES OF SECONDARY STORAGE
There are three m ain types of second ary storage:
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 M agnetic Tape.
 M agnetic D isk.
 O ptical D isk.

11. TYPES OF SECONDARY STORAGE
(CONT…)
Magnetic Tape:
 O ld est storage d evice,
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 U sed for large com puter like
m ainfram e com puters,
 M ad e of plastic coated with
m agnetic m aterial,
 Store d ata perm anently,
 U sed to read and write d ata,
 C ost of storing d ata is expensive,
 U sed in reels.

12. TYPES OF SECONDARY STORAGE
(CONT…)
Magnetic Disk:
 A thin circular m etal or plastic d isk
coated with m agnetic m aterial,
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 Stored d ata in the form of m agnetic
spots,
 A rand om access d evice,
 Faster than m agnetic tape.
There are three m ain types of
m agnetic d isk:
i. H ard D isk
ii. Floppy D isk
iii. Zip D isk

13. TYPES OF MAGNETIC DISK
Hard Disk:

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U sually used as second ary storage,
 Also called fixed d isk,
 C onsists of one or m ore m etal
plates,
 M etal plates are coated with
m agnetic m aterial to store d ata,
 Also have an access arm and read /
write head s.

14. TYPES OF MAGNETIC DISK (CONT...)
Floppy Disk:
 A sm all plastic plate coated with
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m agnetic m aterial,
 Stored d ata in m agnetic spots,
 U sed to transfer d ata from one
com puter to another.

15. TYPES OF MAGNETIC DISK (CONT...)
Zip Disk :
 Sim ilar to 3 ½ inch floppy
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d isk,
 C an store 1 00 M B or m ore
d ata.
 U sed to read and write d ata.

16. TYPES OF SECONDARY STORAGE
(CONT...)
Optical Disk:
U sed L ASER technology to read and write d ata,
L ASER stand s for L ight Am plification through
Em ission of Rad iation,
L aser beam writes on the surface of optical d isk by
creating very sm all holes.
The presence of hole represents a O ne, and
absence of the hole represents a Zero.

17. TYPES OF OPTICAL DISK
There are following m ain types of optical d isk:
ii. C D -RO M .
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iii. C D -R or WO RM
iv. C D -RW
v. D VD -RO M
vi. D VD -R
vii. D VD -RW

18. TYPES OF OPTICAL DISK (CONT…)
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C D-ROM :
Stand s for C om pact D isk-Read O nly
M em ory,
 D ata stored can only be read ,
D ata can be easily transferred ,
C om m only can store 650 M B / 700 M B/
750 M B d ata.

19. TYPES OF OPTICAL DISK (CONT…)
C D-R (C D Recordable) Or
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WORM:
 C om pact d isc record able,
 An optical second ary storage
d evice,
 Invented by Sony and Philips,
 Also known as a WO RM (write
once read m any),
 C an store d ata on it only once.

20. TYPES OF OPTICAL DISK (CONT…)
C D-RW ( C D Rewritable ):
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 Stand s for C om pact D isk Rewritable,
 Special type of C D ,
 C an write d ata on it,
 C D -Writers are used to store d ata.

21. TYPES OF OPTICAL DISK (CONT…)
DVD - Digital Video Disk (DVD-
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ROM):
 Stand s for D igital Vid eo D isk,
 U sed a laser beam with a short wave
length
 C reate very sm all holes on the
surface of d isk.
 C an store up to 1 7 GB or m ore d ata.

22. TYPES OF OPTICAL DISK (CONT…)
DVD-R (DVD-Recordable):
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Stand s for D igital Vid eo D isk
Record able,
Initially a blank d isk,
C an store d ata only once,
Becom es read only,
N orm ally used to store high d efinition
vid eo m ovies.

23. TYPES OF OPTICAL DISK (CONT…)
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DVD-RW ( DVD Rewritable):
 Stand s for D igital Vid eo D isk
Rewritable.
 C an write d ata m any tim es by
erasing the old d ata.

24. WHY WE USE SECONDARY STORAGE
DEVICES
It isnon volatile and perm anent.
U sed for a very sim ple task backing up d ata.
U sed to serve as an external hard d rive.
Becom ing m ore and m ore portable as technology
progresses.
M any businesses will connect second ary storage
d evices to share files.
 K eep d ata on them for future use.
Ad d itional space for d ata.

25. CONCLUSION
The prim ary m em ory is costly, not a perm anent storage
m ed ia and has lim ited capacity. The second ary m em ory
Created by Hossain Raju
is the storage other than m ain m em ory, and is used for
storing large d ata files, system program s and the like
which are not continuously required by the C PU . It also
serves as an overflow m em ory when the capacity of the
m ain m em ory is exceed ed .

26. REFERENCES
 Elem ents of C om puter Science by S.K . Sarkar & A. K .
Gupta
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 en.wikiped ia.org
 www.slid eshare.net
 www.techterm s.com
 answers.ask.com

27. CREATED BY HOSSAIN RAJU