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COMPUTER MEMORY

COMPUTER MEMORY

Based on two key factors i.e, capacity and access time, memory is characterized and classified into 2 types.

               Primary Memory or Main Memory

                      Secondary Memory or Auxiliary Memory

Hierarchy of Memory are as follows

CPU

REGISTER

CACHE 

MAIN MEMORY

MAGNETIC DISC

MAGNETIC TAPE

Parameters of memory 

Storage Capacity:- Capacity size of the Memory expressed in terms of Number of Words or Bytes.

Access Time:- Time required for read and write operation of desired modes till the data is made available or rewritten.



Access Mode:- Memory comprised of various Memory location which can be accessed randomly,sequentially and directly.

Physical Characteristics:- Device can be categorized into 4 types Optical, Mechanical, Electronic, Magnetic.

Primary Memory

This Memory allows the computer to store Data for immediate actions and to keep record of what is being processing. This Memory is Classified into

RAM

ROM

Random Access Memory(RAM)

Microchip which is Implemented using Semiconductors is Called RAM. It also known for Read/Write Operations Which allows CPU to read as well as Write data and used for Temporary Storage of Input/Output Data.

RAM is Classified into:

Dynamic RAM(DRAM)

It also Known as DRAM which is made of Memory Cell, where each Cell composed of one capacitor and one Transistor.

DRAM is less cost, very slow, occupy less space and must be refreshed continually for storing data as a result of refresh operation occurs thousands of time per Second..

Static RAM(SRAM)

It also Known as SRAM, which is made of Multiple Transistor without using Capacitor. Data remain as long as power is provided to Memory chip and uses Cache Memory due to its high Speed and its expensive.

EDORAM

Extended Data Output Dynamic RAM(EDORAM) used to improve the methods of access and improve time to read content from Memory.

Cache Memory

It is high speed Memory which increases the processing speed and placed in between RAM and CPU. Cache memory is very expensive and small in size. Its size in computers is of 26kb to 2Mb..

Read Only Memory(ROM)

ROM contain only read operation and no write operation, which also stores Data or Information when power is lost or off. It has data written only once i.e, if a chip is programmed at the time of manufacturing it cannot be overwritten again.




Programmable ROM

This is known as One time Programmable device where the contents can never be changed and can be programmed at buffer, final test or in system. It is mainly found in Mobile phones, Medical devices, Multimedia Interfaces.

Erasable Programmable ROM

This type ROM can be erased by Exposure to strong Ultraviolet light and be rewritten.

Electrically Erasable Programmable ROM

In this type Exposure to Electric pulses reverses the burning Process and it can be erased electrically then rewritten.

Secondary Memory

The Data which is first copied into Primary storage RAM and processed is called Secondary Memory. It is used to store data and programs and remain as long as in memory until they are deleted or rewritten.

Secondary Memory is Classified into

Magnetic Disks

Optical Disks

Digital Video Disk(DVD)

Blue Ray Disk

Solid State Disk

Magnetic Disks

Hard Disk Drive

It is Magnetic Data Storage Disk used for storing and retrieving digital information using rotating disks called Platters.

Platters require read/write Operations to read and write data or information.

Floppy Disk

Floppy Disk is available in sizes used for storing data but in small amounts and slow compared to that of Hard disk. It is round in shapes and coated with Iron Oxides.

Optical Disks

Compact Disk(CD)

Storage of Data along with Digital audio and video which is of less expensive. CD’s are classified into following 3 main types.

CD-ROM

It is also known as Compact Disk-Read Only Memory, here Data can be written once and can read any time i.e, recorded content cannot be changed or erased by users. It is used to store data in the form of texts and graphics upto 1Gb.

CD-R

It is also Known as Compact Disk-Recordable, here Data stored once cannot be erased and can be written only once.

CD-RW

It is also known as Compact-Re writable, which is a erasable Disk where data is written multiple times on a disk by the use of format features.

Digital Video Disk(DVD)

It is also known as SD (Super Density) disk which is also a storage media and can store several Gigabytes of data and also have the dimensions same as CD Disk. 3 types of DVD’s are

DVD-ROM:-Digital Video Disk-Read Only Memory.

DVD-R:-Digital Video Disk-Recordable.

DVD-RW:-Digital Video Disk-Re writable.

Blue Ray Disk

Its is one of the Storage medium used to capture the data normally in DVD format and holds almost 5 times more data than DVD. Blue Ray Disk  formats are as below




BD-ROM:-Read only for pre recorded content.

BD-R:-Recordable for PC data storage.

BD-RW:-Re writable for PC data storage.

D-RE:-Rewritable for HDTV Recording.

Solid State Disk

Pen/Thumb Drive

Flash Storage device with Flash Memory and Portable USB(Universal Serial Bus)Interface.

USB flash Drives are typically removable, re writable and also small with storage capacities of 256 Mb,16 Gb,4 Gb etc

It is quite easy to transfer and store the information using pen drives.

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