Computer Memory

Primary Memory

Main memory or primary memory directly communicates with the CPU of the computer.

Main memory contains only those programs, data or information that is required by CPU for current execution.

It occupies the central position in memory hierarchy as it is able to communicate directly to both CPU and secondary memory through I/O processor. 


Features of primary memory

  • Primary memory is made by electronic semiconductor devices.
  • It directly communicates with the CPU of the computer.
  • It is also needed by the system itself at the time of processing.
  • Primary memory is faster as compared to secondary memory.
  • It is very costly as compared to secondary memory.

Types of Primary memory

Primary Memory may be two types-

  1. Random Access Memory (RAM) and
  2. Read Only Memory (ROM)

Random Access Memory (RAM)


  • We can read from it and also can write there. So this memory is read and writes memory.
  • This memory is also known as Volatile Memory.
  • When the computer is switched off than the entry is vanished.
  • There are two main types of RAM: Static RAM and Dynamic RAM.


Difference: SRAM vs DRAM



It is based on transistor technology.

It is based on capacitor technology.

It is expensive.

It is cheaper.

It not require refreshing.

It require refreshing.

It is faster in action.

It is slower in action.

It has low storage capacity.

It has high storage capacity.

It is consumes more power.

It is consumes less power.

It has low storage density.

It has high storage density.

Read Only Memory (ROM):

  • It is non-volatile memory.
  • It is permanent memory.
  • Instructions and information are stored by the manufacturer in this memory.

Functions of ROM

  • Initiates the loading of operating system.
  • It performs a ‘RAM Test’ to ensure working of the available RAM.
  • Reports back on all the ports, the ROM has encountered in the computer.
  • Checks the default output device.
  • Checks the default input device.


Types of ROM

ROM may be of five types-

  1. PROM (Programmable Read Only Memory)
  2. EPROM (Erasable Programmable Read Only Memory)
  3. EEROM (Electrically Erasable Read Only Memory)
  4. EEPROM (Electrically Erasable Programmable Read Only Memory)
  5. UVPROM (Ultra Violet Programmable Read Only Memory)

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