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
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
INTRODUCTIONEvery com puter system consists of a variety of d evicesto store the instructions and d ata required for its Created by H ossain Rajuoperation. The instructions and d ata are stored in them em ory (storage) unit of the com puter. The m em orycom ponents of a com puter system can be d ivid ed intofollowing m ain groups: Prim ary Storage (M ain M em ory), Second ary Storage (Auxiliary M em ory), and Internal Processor Storage.
WHAT IS SECONDARY STORAGE?Second ary storage technology refers tostorage d evices and storage m ed ia thatare not always d irectly accessible by acom puter. This d iffers from prim arystorage technology, such as an internalhard d rive, which is constantly available.In C omputer Science, “Any m eans ofstoring and retrieving d ata external to them ain com puter itself but accessible tothe program .”
SECONDARY STORAGE (CONT…) U sed in a com puter system to overcom e the lim itations of prim ary storage, Created by Hossain Raju 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.
THE ADVANTAGES OF SECONDARYSTORAGEThe ad vantages of Second ary storage are given below: Created by Hossain Raju 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.
THE DISADVANTAGES OF SECONDARYSTORAGEThe D isad vantages of Second ary storage are given below: While RAM electronic storage d evices are fast, second ary Created by Hossain Raju 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.
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, Created by Hossain Raju 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.
TYPES OF SECONDARY STORAGEThere are three m ain types of second ary storage: Created by Hossain Raju M agnetic Tape. M agnetic D isk. O ptical D isk.
TYPES OF SECONDARY STORAGE (CONT…)Magnetic Tape: O ld est storage d evice, Created by Hossain Raju 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.
TYPES OF SECONDARY STORAGE (CONT…)Magnetic Disk: A thin circular m etal or plastic d isk coated with m agnetic m aterial, Created by Hossain Raju 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
TYPES OF MAGNETIC DISK Hard Disk: Created by Hossain Raju 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.
TYPES OF MAGNETIC DISK (CONT...) Floppy Disk: A sm all plastic plate coated with Created by Hossain Raju m agnetic m aterial, Stored d ata in m agnetic spots, U sed to transfer d ata from one com puter to another.
TYPES OF MAGNETIC DISK (CONT...) Zip Disk : Sim ilar to 3 ½ inch floppy Created by Hossain Raju d isk, C an store 1 00 M B or m ore d ata. U sed to read and write d ata.
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.
TYPES OF OPTICAL DISKThere are following m ain types of optical d isk:ii. C D -RO M . Created by Hossain Rajuiii. C D -R or WO RMiv. C D -RWv. D VD -RO Mvi. D VD -Rvii. D VD -RW
TYPES OF OPTICAL DISK (CONT…) Created by Hossain RajuC D-ROM :Stand s for C om pact D isk-Read O nlyM 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.
TYPES OF OPTICAL DISK (CONT…) C D-R (C D Recordable) Or Created by Hossain Raju 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.
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.
TYPES OF OPTICAL DISK (CONT…) DVD - Digital Video Disk (DVD- Created by Hossain Raju 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.
TYPES OF OPTICAL DISK (CONT…)DVD-R (DVD-Recordable): Created by Hossain RajuStand s for D igital Vid eo D iskRecord 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 efinitionvid eo m ovies.
TYPES OF OPTICAL DISK (CONT…) Created by Hossain Raju 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.
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.
CONCLUSIONThe prim ary m em ory is costly, not a perm anent storagem ed ia and has lim ited capacity. The second ary m em ory Created by Hossain Rajuis the storage other than m ain m em ory, and is used forstoring large d ata files, system program s and the likewhich are not continuously required by the C PU . It alsoserves as an overflow m em ory when the capacity of them ain m em ory is exceed ed .
REFERENCES Elem ents of C om puter Science by S.K . Sarkar & A. K . Gupta Created by Hossain Raju en.wikiped ia.org www.slid eshare.net www.techterm s.com answers.ask.com