COMPUTER MEMORY

Ch-1 Computer Organisation

PREPEARED BY:- BIBHUDENDRA SARANGI

Types of Computer Memory��

Based on location and storing characteristic, computer memories are of two types

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• 1. Primary Memory / Internal memory

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• 2. Secondary Memory / External memory

Types of Memory

Difference between �Primary and Secondary Memory

• Primary Memory
• Located in side the system unit and fixed on the main board.
• Made of semiconductor materials.
• They are temporary or volatile memories.
• Does not store user data or program permanently.
• Used during processing
• Less storage capacity
• High speed read and write
• High cost

• Secondary memory
• Located inside or out side the system unit. Portable.
• Permanent memory, used for backup purpose.
• Stores user data and program permanently.
• Made of magnetic core or optical materials
• Never used during processing.
• High storage capacity.
• Slow read and write
• Low cost

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RANDOM ACCESS MEMORY�( R A M )

Ram is a Primary Memory

Placed on the Main board

Made of Semiconductor Materials

Volatile Memory / Temporary Memory

Does not store user data and program permanently

Stores data during processing.

Low storage capacity

High speed read and write.

All in puts coming into the computer and all

output going from computer goes through the RAM

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Read Only Memory�( ROM)

• ROM is a primary memory
• Placed on the main board of the computer
• Users can not use ROM
• User can not write or read from the ROM
• ROM stores special instructions for the computer like booting process instructions.
• There are 3 types of ROM
• 1. Programmable Read Only Memory (PROM)
• 2. Erasable Programmable Read Only Memory (EPROM)
• 3. Electrically Erasable Programmable read only Memory (EPROM)

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PROM is programmable, instructions can be written using a special device called PROM PROGRAMMER. Any data from the PROM can not be erased.

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Read Only Memory

• EPROMs are also programmable with the help of Prom Programmer.
• Contents of an EPROM can be erased by passing it through Ultra Violet Ray.

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• EEPROM are also programmable with the help of Prom Programmer
• Contents of an EEPROM can be erased by passing high voltage current through EERPM

Prom Programmer

ROMs

Secondary Memory / External memory

Floppy Disk

• Floppy disk was invented in 1960 and was

out of market since 1995.

• It is circular disk made of thin polyester film

and coated with ferrous oxide and magnetically charged

• Concentric circles are drawn on both surface are known

as Tracks, Lines from centers to the periphery creates

a space known as Sectors, The track line and the

sectors line creates a space known as Cluster.

* Data stored on the Cluster.