computer memory prince dudhatra 9724949948

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

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.

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.

Mostly mainframe

computers use reel toreel tapes -

� Mostly minicomputers use cartridges.

� Mostly Microcomputers used cassettes.

A memory device, such as a f loppy disk,

hard disk that is covered with a magnetic

coating on which information is store.

Store and Retrieve data

Read / Write headFormatting

Track ± Sector FAT

� 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.

� 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.

� 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.

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.

� 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.

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.

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.

Optical disk is an electronic data

storage medium that can be

written to and read using a low

powered laser beam.

There are 3 types of disc:-

� Compact Disc Read Only Memory(CD-R OM)

� Write Once Read Many CompactDiscs (WORM-CD)

� Magneto-Optical (MO)

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.

� These discs comes pre-recorded and

cannot be altered.

� In other words it is read only

storage medium.

� Capacity

The standard CD-R OM can

hold approx. 650-700 MB of

� 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).

� 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.

� 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

Cont«.

� Packaged inside a memory card:

±Extremely durable

±Can withstand intense pressure± Immersion in water

� Average power requirements range from

5V-12V

� 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

� Why using flash memory?

It has no moving part so it isnoiseless

It allows fast er accessSmaller in size and light er

� Examples

t er·s B

IOS chip

Comput er·s flash memory

Memory card for video game

console

� One of the most popular alternatives for

portable device storage� Aggressive advances are still being made

Samsung

Scandisk

ToshibaAMD

Frontech

computer memory prince dudhatra 9724949948

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