Difference Between Primary Memory and Secondary Memory

Difference Between Primary Memory and Secondary Memory

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Rashmi Karan
Manager - Content
Updated on Feb 9, 2024 12:32 IST

Computer memory is simply the computer’s brain where data and information are stored for easy retrieval. Memory is the computer’s storage space that temporarily or permanently stores data or programs. Learn what primary and secondary memory is, their types, and the difference between primary and secondary memory. The article covers the concepts of primary memory and secondary memory, along with the difference between both.


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Difference between Primary and Secondary Memory – Comparison Table

Primary memory is used for temporarily storing data that is actively being used by the computer's CPU, while secondary memory (storage) is used for long-term data storage, such as files and programs that are not currently in use. Listed below are some other primary and secondary memory differences.

Comparison Parameters Primary Memory Secondary Memory
Storage validity Primary memory is the main memory and stores data temporarily. Secondary memory is the external memory and stores data permanently.
Access The CPU can directly access the data. The CPU cannot directly access the data.
Volatility Primary memory is volatile. It loses data in case of a power outage. Secondary memory is non-volatile; data is stored even during a power failure.
Storage  Data is stored inside costly semiconductor chips. Data is stored on external hardware devices like hard drives, floppy disks, etc.
Division It can be divided into RAM and ROM  They do not have such a classification. Secondary memories are permanent storage devices like CDs, DVDs, etc.
Speed Faster  Slower
Stored data It saves the data that the computer is currently using. It can save various types of data in various formats and huge sizes.

Now that you know how to differentiate between primary and secondary memory let us understand their basic concepts.

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What is Primary Memory?

Primary memory is the internal memory of a computer system. It stores and retrieves data, instructions, and information. The CPU directly and randomly accesses primary memory; hence primary memory is also referred to as Random Access Memory or RAM. It is a volatile memory and loses data and instructions when the power turns off.

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Types of Primary Memory:

RAM (Random Access Memory)

Random Access Memory or RAM is usually provided as the computer system’s main memory. It is also regarded as temporary or cache memory constantly being written to and read. You will lose information saved in primary memory when the power supply of the computer or laptop turns off. Simply put, RAM is a primary memory from which you can only read information.

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ROM (Read-Only Memory)

ROM is a non-volatile memory containing data that we cannot change. In this case, information is not lost when the power supply is turned off. The computer manufacturer determines ROM information. It is permanently stored at the time of manufacture so that the user cannot overwrite it.

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Primary Memory Characteristics

  • The computer cannot function without primary memory.
  • Primary memory is also known as the main memory.
  • You may lose data in case the power is off
  • Also known as volatile memory
  • It is the working memory of the computer.
  • It is faster as compared to secondary memory.
  • Examples: RAM, ROM, cache, PROM, EPROM, registers, etc.
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What is Secondary Memory?

Secondary memory is a storage device that the CPU cannot access directly. It is a permanent storage device. 

The CPU accesses these devices through an input/output channel. The data first transfers to primary from secondary storage before its assessment. Modern computers often use hard drives and optical storage devices (CDs, DVDs) as secondary storage devices. 

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A secondary storage device organizes data into files and directories based on a file system. It also allows the user to access or use additional information like access permissions, owner, last access time, etc. Also, secondary memory keeps less used data temporarily when primary memory gets full. 

Secondary memory devices are less expensive and can store vast amounts of data, audio, video, and multimedia files. Organizations can store the equivalent of a roomful of data on disks that consume dramatically and significantly less physical space.

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Types of Secondary Memory

  • Solid-state storage devices, such as USB memory sticks.
  • Optical storage devices, such as CDs, DVDs, and Blu-ray discs.
  • Examples: Magnetic storage devices include zip, floppy, and hard disk drives.

Secondary Memory Characteristics

  • These are magnetic and optical memories.
  • It is a type of non-volatile memory.
  • Data is permanently stored even when the computer is turned off
  • It helps store data on a computer
  • The computer can function without secondary memory
  • Slower than primary memory
  • Examples: magnetic tapes, optical discs, floppy disks, flash memory [USB drives], paper tape, punched cards, etc.
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Secondary storage devices are any non-volatile storage device that is either internally or externally present within the computer. These can be an7 device that helps provide permanent data storage.

Comparison Between Primary And Secondary Memories

  • Primary memory is the computer’s main memory and stores data temporarily. 
  • Secondary memory is external memory and saves data permanently.
  • Data stored in primary memory can be directly accessed by the CPU, which cannot be accessed in secondary memory.
  • Primary memory is lost during a power outage, while secondary memory saves the data. 
  • Secondary memory is non-volatile, while primary memory is volatile.
  • Primary memory is stored on semiconductor chips, while secondary memory is stored on external devices.
  • Primary memory is classified into cache and random access memory, while secondary memory has no such categories.
  • Secondary memory can save data in various formats that can be accessed anytime, while primary memory uses the computer’s current data.
  • Primary memory is faster.


Both types of memory have several differences. Although different, they work together for the computer to run smoothly. Primary memory itself can’t save more than a few gigabytes of data, but secondary memory fills that gap by providing up to a terabyte of space. While the latter lags in processing data, the primary memory is faster and easily accessible.

Both primary and secondary memories are crucial for a computer’s effortless and efficient functioning, and they complement each other. I hope this article helped you to differentiate between primary and secondary memory, or we can say understand the difference between primary and secondary storage.

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How is primary memory different from secondary memory in terms of speed?

Primary memory is much faster than secondary memory. It provides quick access to data and instructions, enabling the CPU to read and write data at high speeds. In contrast, secondary memory devices have relatively slower access times and transfer rates than primary memory.

Can programs be directly executed from secondary memory?

No, programs cannot be directly executed from secondary memory. They must be loaded into primary memory before the CPU executes them. The operating system retrieves the required programs and data from secondary memory and copies them into primary memory for execution.

What is the capacity difference between primary memory and secondary memory?

Primary memory typically has a smaller capacity compared to secondary memory. While primary memory capacity is usually measured in gigabytes (GB) or terabytes (TB), secondary memory devices like hard drives or SSDs can have capacities ranging from several gigabytes to multiple terabytes or more.

Can primary memory be upgraded or expanded?

Primary memory can be upgraded or expanded by adding more RAM modules to the computer's motherboard. This increases the amount of data and programs that can be stored and processed simultaneously, improving system performance.

Which memory type is more expensive: primary or secondary?

Primary memory is generally more expensive than secondary memory on a cost-per-byte basis. This is because primary memory technologies, such as DDR4 RAM, are faster and provide the real-time processing capabilities required by the CPU. Secondary memory devices, like hard drives or SSDs, offer larger storage capacities at a lower cost.

About the Author
Rashmi Karan
Manager - Content

Rashmi is a postgraduate in Biotechnology with a flair for research-oriented work and has an experience of over 13 years in content creation and social media handling. She has a diversified writing portfolio and aim... Read Full Bio