Difference between Primary Memory and Secondary Memory

The computer is an amazing creation by a human. And memory is the beauty of this creation. No doubt that computer memory is unbeatable to any creation in this universe. It is considered the brain of the computer. The information stored inside this memory is further processed as per the instructions given to the processor. It performs multiple tasks within milliseconds and that too error-free.

Let us know more about memory types.

Computer memory can be classified into two types

  1. Primary Memory
  2. Secondary Memory

Both of them have their importance. Let’s see what is the difference between primary memory and secondary memory.

Difference between Primary Memory and Secondary Memory in table form

Primary Memory
Secondary Memory
Difference between Primary Memory and Secondary Memory Secondary memory is also called external memory or auxiliary memory
Processor/ CPU can directly access the data stored in primary memory Processor/ CPU cannot directly access the data stored in primary memory
It is volatile memory i.e. the data is lost when the power supply is off It is non-volatile memory i.e. data is not lost even when the power supply is off
Devices used to store primary memory are costlier than secondary memory devices Devices used to store secondary memory are less costly than primary memory devices
This type of memory is accessed by the data bus This type of memory is accessed by the I/O channels
Generally, the storage capacity of primary memory ranges from 16 to 32 GB On the general basis, the storage capacity of secondary memory ranges from 200 GB to terabytes
Primary memories consist of semiconductor material Secondary memories consist of magnetic and optical material
Examples of primary memory are RAM, ROM, EPROM, Registers, cache memory, etc. Examples of secondary memory are hard drives, solid-state drives, CD, DVDs, USB drives, etc.

What is Primary Memory?

Primary memory is also called the main memory of the computer system. The instructions that are being currently executed on the computer are copied to the main memory because the CPU/processor can directly access the data. It is the volatile memory meaning the data or information is lost if the power supply is cut.

Primary memory has a fast speed in accessing the data and the CPU access the data from primary memory using the data bus. This type of memory consists of semiconductor material and has less storage capacity as compared to secondary memory.

Let us further glimpse at the types of primary memory.

Primary memory is of two types

  1. RAM – Random Access Memory
  2. ROM – Read-Only Memory

RAM – Random Access Memory is read and write memory. The data or instruction which is currently processed by the processor is first stored in the RAM. This memory is used to speed the processor and quickly access the needed data. This memory is of volatile type and often called temporary memory.

ROM – Read Only Memory is the type of primary memory that only reads the data. Its content cannot be changed and gives a facility of permanent storage. ROM is a non-volatile memory that results in storing the data even if the power supply is off. PROM, EPROM, EEPROM, are some of the types of Read-Only Memory.

We now have a clear view of primary memory and its types. You can also learn the difference between RAM and ROM. Now let us see what is the meaning of secondary memory.

What is Secondary Memory?

Secondary memory is called auxiliary or external memory of the computer. As per its name, we understand that this type of memory is attached externally to a computer. So there is no issue of volatility and the data or information is safe and stored permanently. Here, in contrast to primary memory, the data cannot be directly accessed by the CPU or the processor. Firstly, the data needs to be copied to the primary memory, and then it is accessed by the processor. As it is a little lengthy process, retrieving data is slower as compared to primary memory.

Secondary memory is made up of magnetic and optical materials and it is cheaper as compared to primary memory. Now, as it is external memory, a computer can work without the availability of secondary memory. It is available in access in market and user can choose the size of memory as per his/her demands.

Some of the secondary memory devices include hard disk, floppy disk, USB drives, CDs, DVDs, paper tapes, punched cards, and many more.

Primary memory and secondary memories are both left and right hand of the computer. Both provide specific facilities to the user. But remember, a computer device can work without secondary memory but it cannot function without primary memory. Primary memory is a must and comes in a limited size range. It is also expensive. Whereas secondary memory is optional and available in plenty amount. It is cheaper and provides large storage space to the user.

After all, memory smoothens the function of the computer and indeed it is an essential part of the computer. Both types of memories are important and they cover each other’s shortcomings.

Shraddha Changune
SVKM’s Institute of Technology, Dhule


1. https://www.jotuts.com/top-10-differences-primary-secondary-memory-infographic/
2. https://techterms.com/definition/secondary_memory
3. https://techterms.com/definition/primary_memory
4. https://www.guru99.com/primary-vs-secondary-memory.html

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