Storage Hardware Slide

8/12/2019 Storage Hardware Slide

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Storage Fundamentals:

Storage is categorized as primary or secondary. Primary storage is RAM

(Main Memory), which is volatile. Secondary storage is permanent

storage, which is nonvolatile. The capacity of storage devices ismeasured in bytes, kilobytes, megabytes, gigabytes, and a Terabytes.

Files are classified as program files or data files, which in turn are

classified as master files or transaction files. Data may remain in

secondary storage for a while before being processed (Batch processing),or it may be processed immediately (real time processing).



Primary storage and secondary storage:

The term Primary storage (main memory) refers to RAM, where both data and

instructions are temporarily held for immediate access and used by thecomputers microprocessor. Although the technology is changing, most primary

storage is considered as a volatile form of storage, meaning that the data and

instructions are lost when the computer is turned off.

The term Secondary storage (auxiliary storage) is any storage device designed

to retain data and instructions (programs) in a relatively permanent form.Secondary storage is nonvolatile, meaning that saved data and instructions

remain intact when the computer is turned off.

Data Representation & data storage capacity:

The terms that used to measure the data capacity of storage devices are given

below:

•Kilobyte : A kilobyte(abbreviated K or KB) is equivalent to 1024 bytes

•Megabyte: A megabyte (abbreviated M or MB) is 1 million bytes.(Rounded

off)

•Gigabyte : A gigabyte (G or GB) is 1 billion bytes.(rounded off)

•Terabyte : A terabyte (T or TB) is about 1 trillion bytes.



Types of files:

A file is a collection of information treated as a unit. There are many kinds

of files, but the principal division is between program files and data files.

Program files: Program files are files contained software instructions. In a

word processing program for example, you may see files listed (with names

such as INSTALL. EXE) that performs specific function associated with

word processing. These files are part of software package.

Data files: Data files are files that contain data. Often you will create a

name these files yourself, such as DOCUMENT. 1 or PSYCH.RPT (for

psychology report)

Master files: The master file is a data file containing relatively permanent

records that are generally updated periodically. An example of a master filewould be the address-label file for all students currently enrolled at your

college.

Transaction File: The Transaction File is a temporary holding file that

holds all changes to be made to the master file: additions, deletions,

revisions.



Batch processing: In batch processing data is collected over several

days or weeks and then processed all at one time, as a “ batch”. Thus if

users need to make some request of the system, they must wait until the

batch has been processed. Batch processing is less expensive than realtime processing and is suitable for work in which immediate answers to

queries are not needed.

Real-time processing: It records information immediately and responds

to user requests at the time transactions occur.



FORMS AND ELEMENTS OF

SECONDARY STORAGE

Tape DisketteHard

disk

Optical

disk

Data

storageand

retrieva

lmethod

s

Datacompression and

decompr ession

Otherforms

ofsecon

darystorag

e



Tape:

On magnetic tape, data is stored using magnetized spots ii

sequential fashion. On microcomputers, tapes are used in cartridgetape units. On large computers, tapes are used in magnetic-tape

units.



Diskette or floppy disk is a storage medium

frequently used with microcomputers. Diskettes

are made of a flexible plastic that is coated with a

material that is easily magnetized. The disk isenclosed in a protective paper or hard plastic

jacket.



Character istics of diskettes:

Data is recorded in rings called tracks. Each track isdivided into eight or nine sectors, which are wedge-

shaped sections used for storage reference purposes.

Unformatted disks should be formatted.A disk’s capacity depends on whether it is single or

double-sided and on its recording density (single,

double or high density)

The data on a disk cannot be changed.



Hard disk can store more and more data. Hard disk drives can be

internal (inside the computer) or external (outside the computer,

connected to it by a cable)



The disadvantage of hard disk

is head-crash. A head crash

happens when the read/writeheads or particles come into

contact with the disk surface.



Hard disk for large computer

systems come in the following

forms

Removal packs

Fixed disk drives

RAID storage systems





Optical storage technologiesuse a laser beam to pack

information densely on a

removable disk. The opticalstorage technology is used with

computers consists of four

types.



Theses four types are-CD-Rom disk- ROM means read only memory. It is an

optical (laser) technology, capable of storing huge amounts

of data on a disk. The data is pre-recorded on the disk by

the service provider.

CD-R- It is recordable compact disk, allows the user to

write data.

WORM- It means write once, read many.

EOD- Erasable optical disk allows the user to write, delete

and write again data into it.



CD-ROM formats may beinteractive or multimedia.

Variants of CD-ROMs are CD-I

(I for interactive), CD-TV(television) and MPC

(Multimedia PersonalComputer).



OTHER

TYPES OF

SECONDARY

STORAGE



Flash memory uses circuitry on

credit card size cards that can be

inserted or connected withcomputer. Such as pen drive or

memory card.



Bubble Memory useselectromagnetic bubbles that move

in a circular motion past the

equivalent of a read/write head.The presence of a bubble is

considered a binary 1, its absence a

binary 0.



Micro ModulatorCombined Memory IC

Mother Board (Functional Sector of Bubble Memory)



Storage Hardware Slide

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