Wednesday, September 18, 2013

COMPUTER MEMORY

MEMORY

The term "memory" applies to any electronic component capable of  storing data.

Memory  can be categorized in to two types

1. Internal memory

2. External memory

Internal memory 

It is used to store the data temporary.

It uses micro conductors ,Ex. Electronic circuits.

Internal memory corresponds to random  access  memory.

External Memory 

It is also called physical  or auxiliary memory.

It is used to store the data permanently.

Examples  of external memory are hard disk, compact disk, Digital video disk, ROM.

Characteristics of memory are

*Capacity

*Access time

*Cycle  time

*Through  output

*Non Volatility


Types  of memory

1. Random access memory.

2. Read  only  memory.

3. Flash memory.


Random  access  memory. (RAM)

It is the main memory of  the  computer.

When  a program  is running  temporary  data  is stored here .

RAM is volatile  means that it only stores data as long as it supplied with electricity.

When the computer is turned off, all the data in the memory are immediately erased.

Read  Only  Memory 

ROM is non volatile.

It has only read  only access.

Types  of  ROM are
 1.PROM ( programmable read only memory)

 2.EPROM ( Electrically programmable read  only memory)

 3.EEPROm ELectrically  erasable  programmable  read only memory )

Flash memory 
Flash memory possesses the non-volatility of ROM memories while providing both read and write access .

However, the access times of flash memories are longer than the access times of RAM.

Flash memory is a memory storage device for computers and electronics.
It is most often used in devices like digital cameras, USB flash drives, and video games.
It is quite similar to EEPROM.
Flash memory is different from RAM because RAM is volatile (not permanent).
When power is turned off, RAM loses all its data. Flash can keep its data intact, with no power at all. A hard drive also is permanent (non-volatile) storage, but it is bulky and fragile.
Flash memory is much slower than RAM or hard drives.
But it is great for small electronics because it is small and it has no moving parts.

Examples of flash memory are pendrive.

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