computer memory prince dudhatra 9724949948
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8/7/2019 Computer Memory Prince Dudhatra 9724949948
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Oldest form of computer storage
Magnetic tape is like audio tape
SequentialAccess
Inexpensive
Easily Transported
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First and second generation computers used for most of their storage needs.
It works as a tape recorded. instead of ³play andrecord´ the term ³read and write´ are used.
Magnetic tape capacity is measured in bytes per inch, known as the tape density.
Low density tapes generally stored 1600bpi andhigh density tapes can store 6250bpi.
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ADVANTAGES:-
1. Tapes can record, erased and reused many
times.
2. It is inexpensive.
3. It is easily transportable.
4. Stores large amount of data.
DISADVANTAGE:-
1. Accessing of data.
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Mostly mainframe
computers use reel toreel tapes -
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� Mostly minicomputers use cartridges.
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� Mostly Microcomputers used cassettes.
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A memory device, such as a f loppy disk,
hard disk that is covered with a magnetic
coating on which information is store.
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Store and Retrieve data
Read / Write headFormatting
Track ± Sector FAT
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� A f loppy disk is a thin, circular, f lexible plastic
disk with a magnetic coating enclosed in asquare shaped plastic shell.
� Before anything can be written on a new
f loppy disk, it must be formatted.
� Today, most of f loppy disk are high-density.
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� Storing 2 (sides) x 80 (tracks) x 18 (sectors per
track) x 512 (bytes per sector) =14,74,560
bytes, or approximately 1.44 MB per disk.
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� It usually spin at about 300
revolution per minute.
� The average access time for current
f loppy disk drives to
locate an itemon a disk is approximately 1/12
second or 84 milliseconds.
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ADVANTAGES:
� It is portable and inexpensive.
�Data on f loppy disk can be access randomly.
� It can be use to transfer data from one computer to
another.
DISADVANTAGES:
� Floppy disk is not durable.
� Access time of f loppy disk is low.
� Storage capacity of f loppy disk is limited.
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� A hard disk is similar to a f loppy disk ,
but the hard disk is made of rigid
metallic platters can hold much moredata and operate much faster.
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A single hard drive may have several
platters providing large data storage
capacities.
Most hard disks are permanently
encased within the disk drive in asealed environment free from dust
and dirt.
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The disk can spin very rapidly with the
read/write head f loating above the
disks surface.
Hard disks spin at an average of 33,600 revolutions per minute making
data retrieval very fast.
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Optical disk is an electronic data
storage medium that can be
written to and read using a low
powered laser beam.
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There are 3 types of disc:-
� Compact Disc Read Only Memory(CD-R OM)
� Write Once Read Many CompactDiscs (WORM-CD)
� Magneto-Optical (MO)
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�
CD-R OM is a f lat plastic disc with digitalinformation encoded on it in a spiral form,
from the centre to the outside edge.
� Non volatile
� It is readable by computer with CD-R OM
drive.
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� These discs comes pre-recorded and
cannot be altered.
� In other words it is read only
storage medium.
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� Capacity
The standard CD-R OM can
hold approx. 650-700 MB of
data.
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� It is purchased blank from the manufacturer
and encoded using special equipment.
� The disc can¶t be altered after they areencoded and cannot be easily duplicated.
� Drive that can write to and read a CD is called
CD-Recordable (CD-R).
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� Erasable and combine the magnetic
principles used on tapes and disk with newoptical technology.
� Are removable, portable and durable.
� Large storage capacity.
� Used in graphics and audio-visual
application.
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� It is a non-volatile computer memory
that can be electrically erased and
reprogrammed.� Is a specific type of EEPR OM.
� f lash memory is known as solid state
storage device
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Cont«.
� Packaged inside a memory card:
±Extremely durable
±Can withstand intense pressure± Immersion in water
� Average power requirements range from
5V-12V
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� Continues to be among the most aggressively
scaled electronic technologies
�
Memory cell size minimum of 20 nm expectedto be met in 2010
� May be replaced by Phase-Change RAM or
other emerging technologies
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� Why using flash memory?
It has no moving part so it isnoiseless
It allows fast er accessSmaller in size and light er
� Examples
Compu
t er·s B
IOS chip
Comput er·s flash memory
Memory card for video game
console
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� One of the most popular alternatives for
portable device storage� Aggressive advances are still being made
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Sony
Samsung
Scandisk
ToshibaAMD
Frontech
Iball
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