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Transcript of 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).
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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.
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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.
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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.
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FORMS AND ELEMENTS OF
SECONDARY STORAGE
Tape DisketteHard
disk
Optical
disk
Data
storageand
retrieva
lmethod
s
Datacompression and
decompr ession
Otherforms
ofsecon
darystorag
e
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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.
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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.
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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.
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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)
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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.
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Hard disk for large computer
systems come in the following
forms
Removal packs
Fixed disk drives
RAID storage systems
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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.
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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.
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CD-ROM formats may beinteractive or multimedia.
Variants of CD-ROMs are CD-I
(I for interactive), CD-TV(television) and MPC
(Multimedia PersonalComputer).
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OTHER
TYPES OF
SECONDARY
STORAGE
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Flash memory uses circuitry on
credit card size cards that can be
inserted or connected withcomputer. Such as pen drive or
memory card.
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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.
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Micro ModulatorCombined Memory IC
Mother Board (Functional Sector of Bubble Memory)
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