The document provides an overview of secondary storage, including its advantages and disadvantages. It discusses the evolution of secondary storage devices and the main types, which include magnetic tape, magnetic disks like hard disks and floppy disks, and optical disks like CDs, DVDs, and their variations. Secondary storage is used to overcome limitations of primary storage and provide virtually unlimited storage capacity to store large volumes of data permanently or for backup purposes.

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.
CREATED BY HOSSAIN RAJU

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 ):
Created by Hossain Raju
 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