Difference between Primary and Secondary memory

What is Primary memory?

Primary memory is the computer's main memory. We can access primary memory quickly, as it is the computer’s internal memory. The primary memory is volatile. That is, the information is temporarily stored and would be erased when we shutdown the computer or when power failure occurs. The primary memory is a semiconductor memory which is costlier than the secondary memory. Moreover the primary memory capacity is limited and is very very less compared to secondary memory.

What is Secondary memory?

Secondary memory is slower compared to primary memory. Secondary memory is stored in the secondary storage devices that have the capacity to store huge volumes of data in the range of gigabytes to terabytes. Secondary memory is also called the mass storage media or the backup storage. The data stored in the secondary memory will be permanent. The CPU cannot access the data stored in the secondary memory directly. It will be copied to the primary memory and then it will be processed by the secondary memory. Therefore the data access from the secondary memory is slow.

And the secondary memory is non-volatile, that is the information in the secondary memory is stored permanently. Even if there is a power cut, the data will not be lost. It is available at lesser costs compared to the primary memory.

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Types of Primary and Secondary memory

There are two types of Primary memory:

RAM: RAM stands for Random Access Memory which is the main memory of the computer system. It is the temporary memory which will be lost when the power supply is lost. It offers fast access to the data.

ROM: ROM stands for Read Only Memory. It is the primary memory. Its content is not lost when the power supply is lost. Data is permanently stored in the ROM at manufacturing time that cannot be edited by the user. It includes the instructions which will be executed when the system boots up. There are various types of ROM like PROM, EPROM and EEPROM.

There are several types of Secondary memory:

Hard disk: It is also called as Hard disk drive. Hard disk is a storage device that can hold a huge volume of data and costs very less compared to primary memory. It exists in storage capacities like 250 GB, 500GB, 1 TB and 2 TB.

SSD: SSD stands for Solid State Drive. They are much faster to access than the Hard disk drive. It uses flash memory technology for storing data electronically. SSD is expensive compared to the Hard disk drive but offers improved energy efficiency and faster performance.

SD Card: It is a memory card that is used to store data in portable devices like computers, cell phones and cameras. It is available in capacities like 4, 8, 16, 32, 64, 128. Data on the SD card can be accessed by the card reader.

Optical Discs: Optical Discs include CDs, DVDs and Blu-ray discs which use optical technology to store data. Optical discs are generally used in the software distribution, media storage and backups.

USB drives: It is one of the widely used storage devices in the market. USB drives are physically small devices that enable us to rewrite and data. Nowadays even the capacity of USB drives is increasing.

Speed and Access of Primary and Secondary memory:

Speed: When compared to Secondary memory, Primary memory is very quick to access. The access time measured for secondary memory is milliseconds and even in microseconds while access time for primary memory is in nanoseconds.

Access: Data access to the primary memory is direct and immediate. The data that is actively used by the CPU while executing the program is stored in Primary memory. The processor can write to and read from the primary memory at high speed and makes it appropriate to store data that needs quick processing/frequent access. While secondary memory is used for long term data storage that includes user data, operating systems, applications and files. Secondary memory cannot be accessed directly by the CPU. Inorder to access secondary memory data, it must be transferred to the primary memory before processing. This will consume much time to access and data retrieval is slower.

Cache memory will act as a high-speed intermediary between the main memory and CPU that stores data and information that are frequently accessed to minimize access times and improve system performance.

Volatility and Persistence of Primary memory and Secondary memory:

Primary memory is volatile and it can retain the data until there is electrical power. In case if the power is lost, the data in the primary memory will be lost.
Secondary memory is the non-volatile storage media. Unlike the primary memory, secondary memory will store the data magnetically/electronically. As a result the data will remain intact and will not be lost even when the power is off. When you power on the system you can retrieve the data. Therefore secondary memory plays an important role in preserving the data integrity and allows work continuity as well as data availability over multiple systems/system shutdowns.

Cost and availability of Primary memory and Secondary memory:

Cost: Secondary memory costs less per unit storage when compared to primary memory. Primary memory is built with expensive technologies like DRAM that offers fast access speed but is usually expensive to produce. Secondary memory uses technologies like flash memory/magnetic disks that are relatively less costly and are affordable.

Scalability: In terms of scalability, Primary memory has limitations. It may be as per the specifications of the motherboard and the memory addressability of the CPUSo it will be costly to increase primary memory beyond these limitations. Secondary memory provides scalability. It is easy and less expensive to increase the storage capacity of the secondary memory. We can add hard drives and upgrade to large capacity SSDs.

Functionality of Primary memory and Secondary memory:

In a computer system, Primary memory and secondary memory work together to fulfill various functions.

Data Transfer: The Data is transferred from primary memory to secondary memory. When a computer system reads or writes the data, the data will be transferred from the secondary memory to primary memory. Then the CPU will operate the data in the primary memory which can be accessed very quickly. Then the changes made in the primary memory will be written back to the secondary memory which ensures persistence.

Primary memory plays an important role in running and executing the tasks. Primary memory holds the data needed for immediate processing enabling the CPU to access and retrieve the data quickly. This enables efficient program execution. More data and programs will be stored in the primary memory if the availability of Primary memory is more which will reduce the requirement for frequent data transfers in between the secondary memory and the primary memory.

Secondary memory is important when you need long term access to the data storage, data backup and file management. It ensures data persistence, retaining the data even when the system is shutdown. Secondary memory stores the user files, applications, multimedia content, operating systems and other data that don't need immediate processing. It offers huge storage capacity when compared to the primary memory enabling long term storage of vast amounts of data.

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 Conclusion:

In this blog, we have discussed the differences between the primary and secondary memory. We hope you are now clear with what is primary memory and what is secondary memory. We have compared their types, speed, accessibility, availability, cost, Volatility and Persistence and functionality. We hope you found this information helpful. For more blogs on related technologies, stay tuned to HKT Trainings blogs.