Difference Between Primary Memory and Secondary Memory

In computers, memory is considered as one of the most essential parts. It is the device that is used to store information in the computer for immediate use or later. It can also be considered as the brain of the computer.

Computer memory is basically of two types, primary memory and secondary memory. Memory stores data inside itself for retrieval. Both primary and secondary memory have very different processes by which they save data. The data is then processed by the central processing unit.

Primary Memory vs Secondary Memory

The main difference between primary memory and secondary memory is that primary memory is considered as the main memory of the computer that can be accessed by CPU. Whereas secondary memory is an external storage device that can store data permanently.

Primary Memory vs Secondary Memory

Primary memory and secondary memory are both parts of the main memory unit in a computer that is used for storing and processing data.

Comparison Table Between Primary Memory and Secondary Memory

Parameters of Comparison Primary Memory Secondary Memory
Storage Validity It is the main memory and the data is stored temporarily. It is the external memory and the data is stored permanently.
Access Data can be directly accessed by the CPU. The data cannot be directly accessed by the CPU.
Volatility This type of memory is volatile and the data is lost in case of a power failure. This type of memory is non-volatile and the data is stored even in case of power failure.
Storage Device The data is stored inside very expensive semiconductor chips. The data is stored in external hardware devices like hard drive, floppy disk, etc.
Division It can be divided into cache memory and random access memory (RAM). They have no such divisions and are permanent storage devices like CDs, DVD, etc.
Speed It is faster than the secondary memory. It is relatively slower.
Data Stored It saves the data that is currently being used by the computer. It can save various kinds of data in several formats and huge sizes.

What is Primary Memory?

Primary memory is the kind of memory that can be accessed directly by the central processing unit. It includes several types of memory like RAM (Random Access Memory), ROM (Read Only Memory) and cache memory.

Primary memory is erased when the computer is shut off and the data is not saved. The data transferred between the CPU and RAM is a hundred times faster than the speed of data transfer between the CPU and the hard drive.

Primary memory can also be called primary storage. Primary memory is expensive and technology is constantly being used to develop and optimize it. While RAM loses its memory, ROM can store program data permanently.

What is Secondary Memory?

Secondary memory refers to storage devices such as hard drives and pen drives. The storage device can either be removable or non-removable. The data stored inside secondary memory devices is stored permanently.

The storage capacity of secondary memory is also much larger than primary memory. Operating systems, applications and other files can be stored inside secondary memory devices. It can also be called as external memory as it is not always a part of the device.

Secondary memory devices are also slower and much cheaper than primary memory devices. Data stored inside the secondary storage device is organized in an accessible way and can show at what time, where and what kind of file was stored.

Main Differences Between Primary Memory and Secondary Memory

  1. Primary memory is the main memory of the computer and it saves data temporarily. Secondary memory is the external memory that can be saved permanently.
  2. Data saved in primary memory can be accessed directly by the CPU, which is not the case in secondary memory.
  3. Primary memory is lost in case of power cut while secondary memory remains saved, hence primary memory is volatile and secondary memory is non-volatile.
  4. Primary memory is stored in semiconductor chips while secondary memory is stored in external hardware devices.
  5. Primary memory is categorized into cache memory and random access memory, whereas secondary memory has no such categories.
  6. Primary memory is faster than secondary memory.
  7. Primary memory uses the data that is being currently used by the computer while secondary memory can save data in various formats that can be accessed at any time.


The computer is a marvellous invention that has made our lives easier than ever. To carry out its tasks, it needs certain memory like our brain does. Memory can be considered as the brain of a computer. The data stored inside the device helps in processing further information and is known as memory.

Computer memory is of two types: primary memory and secondary memory. Primary memory is used to process data and carry out basic functions. Secondary memory is the auxiliary memory that is used as an external storage device.

Both kinds of memory have several differences between them which can be used to set them apart from each other. Although they are different, they are parts of a whole. They have to work together to make the computer run smoothly.

Primary memory itself cannot save more than a few gigabytes of data but secondary memory completes that deficiency by providing space up to one terabyte. While secondary memory lags behind in processing data, primary memory is much faster and can be accessed very easily.

The primary memory and the secondary memory both compliment each other and cover up each other’s shortcomings. This is essential for the effortless functioning of a computer.


  1. https://psycnet.apa.org/record/2006-23341-004
  2. https://psycnet.apa.org/record/1974-04901-001
  3. https://books.google.com/books?hl=en&lr=&id=yR8tq_YznMwC&oi=fnd&pg=PA378&dq=secondary+memory+of+computer&ots=1YbUH3R26l&sig=ZHcxYl28ZKaG0yZ2xhX7McSWdVs
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