Classification of memory

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Computer Memory – Primary and Secondary Memory in Computer
Computer Memory–   Memory is storage part in computer. It is store the data, information, programs during processing in computer. It stores data either temporarily or permanent basis. Memory used to important role in saving and retrieving data.
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Types of Memory– Mainly computer have two types memory
  1. Primary Memory / Volatile Memory.
  2. Secondary Memory / Non Volatile Memory.
1.  Primary Memory / Volatile Memory–   Primary memory is internal memory of the computer.  It is also known as main memory and Temporary memory .Primary Memory holds the data and instruction on which computer is currently working. Primary Memory is nature volatile. It means when power is switched off it lost all data.
Types of Primary Memory–Primary memory is generally of two types.
  1. RAM
  2. ROM
1. RAM (Random Access Memory) –It stands for Random Access Memory.RAM is known as read /writes memory. It generally refereed as main memory of the computer system. It is a temporary memory. The information stored in this memory is lost as the power supply to the computer is switched off. That’s why RAM is also called “Volatile Memory”
      Types of RAM–   RAM is also of two types:
a) Static RAM- Static RAM also known as SRAM ,retain stored information as long as the power supply is ON. SRAM are of higher coast and consume more power .They have higher speed than Dynamic RAM
b)Dynamic RAM– Dynamic RAM also known as DRAM, its stored information in a very short time (a few milliseconds) even though the power supply is ON. The Dynamic RAM are cheaper and moderate speed and also they consume less power.
2. ROM  (Read Only Memory) –  It stands for Read Only  Memory.ROM is a Permanent Type memory. Its content are not lost when power supply is switched off. Content of ROM is decided by the computer manufacturer and permanently stored at the time of manufacturing. ROM cannot be overwritten by the computer. It is also called “Non-Volatile Memory”.
Type of ROM: ROM memory is three types names are following-
  1. PROM(Programmable Read Only Memory)-PROM chip is programmable ROM.it is PROM chips to write data once and read many.once chip has been programmed ,the recorded information cannot be changed. PROM is also nonvolatile memory.
  2. EPROM (Erasable Programmable Read Only Memory)- EPROM chip can be programmed time and again by erasing the information stored earlier in it. Information stored in EPROM exposing the chip for some time ultraviolet light .
  3. EEPROM (Electrically Erasable Programmable Read Only Memory)-The EEPROM is programmed and erased by special electrical waves in millisecond. A single byte of a data or the entire contents of device can be erased.
2. Secondary Memory / Non Volatile Memory– Secondary Memory is external memory of the computer. It is also known as Auxiliary memory and permanent memory. It is used to store the different programs and the information permanently. Secondary Memory is nature non volatile. It means data is stored permanently even if power is switched off.
The secondary storage devices are:
  1. Floppy Disks
  2. Magnetic (Hard) Disk
  3. Magnetic Tapes
  4. Pen Drive
  5. Winchester Disk
  6. Optical Disk(CD,DVD)

Differences between Primary and Secondary Memory

S.N.Primary memorySecondary memory
1Primary memory is temporarySecondary memory is permanent
2Primary memory is directly accessible by Processor/CPUSecondary memory is not directly accessible by CPU
3Nature of Parts of Primary memory varies. RAM- volatile in nature. ROM- Non-volatilerIt’s always Non-volatile in nature
4Primary memory devices are more expensive than secondary storage devicesSecondary memory devices are less expensive when compare to primary memory devices
5The memory devices used for primary memory are semiconductor memoriesThe secondary memory devices are magnetic and optical memories
6Primary memory is also known as Main memory or Internal memorySecondary memory is also known as External memory or Auxiliary memory
7Examples: RAM, ROM, Cache memory, PROM, EPROM, Registers etcExamples: Hard Disk, Floppy Disk, Magnetic Tapes etcetera etcetera 

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