What is Main Memory of the computer? OR Introduction to the Main Memory.

What is Main Memory of the computer? OR Introduction to the Main Memory.

Main Memory

• It is the working area of the computer.
• All the running programs are stored in it.
•  It consists of a chip in which millions of identical units are present.
•  Each unit is called a cell or a bit.
• A bit can store either 0 or 1.
• Bits are organized in the form of bytes, which is the combination of 8 bits.
•  Each byte has a unique address.
•  Address of the cell is used to access the data.

This working area is of two types:

1) RAM                2) ROM

1) RAM:

•  It stands for random access memory.
• It is called random access memory because It’s any cell can be accessed directly in the equal time.
• It is also called user’s memory because it stores all the programs, run by the users.
• It is a volatile memory because it requires electric power to store and hold data.
• RAM is a temporary memory because data is lost whenever electric power supply is switched off.

Following are the major types of RAM:

        a) SRAM              b) DRAM               c) MRAM

a)   SRAM:

•  It stands for Static Random Access Memory.
•  This type of RAM does not require electric refreshing.
•  It requires less electric power.
• It is expensive than DRAM.
•  Its design is complex.

b)  DRAM:

•  It stands for Dynamic Random Access Memory.
•  It is slower than SRAM.
• It consumes more electric power.
• It is less expensive than SRAM.
• Its design is simple.

c)   MRAM:

• It stands for magneto resistant Random Access Memory.
•   It is advanced form of RAM.
•  In this RAM magnetic charges are used to store data instead of electric charges.

2) ROM:

• It stands for Read Only memory.
• It is also a working area but its contents are permanent.
• It is also called system’s memory because it stores the routines of operating system.
• Users can not change the data of ROM.
• Manufacturer writes instructions in ROM at the time of manufacturing.
• ROM is a non-volatile memory because it does not require electric power to hold the data.
• ROM is permanent memory because data is not lost, whenever electric power supply is switched off.

Following are the types of ROM

i) PROM              ii) EPROM          ii) EEPROM

i) PROM:

• It stands for Programmable Read Only Memory.
• It is initially blank and manufacturer writes instructions in it at the time of manufacturing.
• Writing is performed only for once and reading can be performed many times.
• Data cannot be erased in it.

ii) EPROM:

•  It stands for Erasable Programmable Read Only Memory.
•   It is extended form of PROM.
• Reading and writing can be performed many times.
•  Data can also be erased with the help of Ultra Violet Rays.
•  Portion of memory cannot be erased.

iii) EEPROM:

• It stands for Electrically Erasable Programmable Read Only Memory.
• It is extended form of EPROM.
• Reading and writing can be performed multiple times.
• Electrical signals are used to erase the data from EEPROM through some special devices.
• Portion of memory can also be erased.

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