Secondary Memory: Meaning, Uses and Types

Secondary memory on computers has a permanent and bigger storage capacity. It stores data and programs permanently even after turning off the computer. These are both magnetic and optical memories. They are non-volatile and permanent memory devices. It is an important concept for GATE CSE.

• Data in a computer system is stored by means of a fixed secondary memory device, whereas secondary memory employs a removable storage device for data storage.
• Secondary storage devices in modern computers consist of hard drives and optical storage devices like CDs and DVDs.
• A secondary storage device generally organizes data into files and directories. 
• Their affordability and ability to accommodate significant data, audio, video, and multimedia files make them popular choices. 
• The availability of DVDs, CDs, Blu-ray discs, Floppy disks, Memory cards, Disk packs, Magnetic tapes, punched cards, punched tapes, and many other removable storage devices is advantageous.

Key Terms: Secondary Memory, Permanent Storage, Fixed Storage, Floppy Disc, Compact Disc, Blu-Ray Disc, Hard Disc, Pen Drive, SD Card

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What is Memory?

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In a laptop, tab, computer, or mobile, memory pertains to the physical devices employed for storing programs or data either temporarily or permanently. It is a group of registers that store memory. Memory can be primary memory or secondary memory. The main constituent of primary memory is semiconductors.

Primary memory can be divided into Read-Only Memory (ROM) and Random Access Memory (RAM). Secondary memory is a specialized physical device designed for the permanent storage of programs and data, such as Hard disk, Compact disc, Flash drive, and more.

Memory

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What is Secondary Memory?

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Memory in a computer generally refers to the physical devices that are used to temporarily or permanently store programs or data. Secondary memory is a collection of registers.

• Primary memory is very temporary and volatile.
• It has a limited amount of storage space. That is why secondary memory is required. It has a bigger storage capacity.
• It stores data and programs permanently even after turning off the computer. Auxiliary memory is an alternative term used to refer to secondary memory.
• It is a non-volatile and permanent memory. Direct access to it is not available to the CPU. 
• Secondary storage devices are also called external storage devices.
• They are less expensive but have substantially more storage space.

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Use of Secondary Memory

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Secondary memory is used for different purposes as follows:

1. Permanent storage: Secondary memory keeps data indefinitely even if the power supply is turned off.
2. Large storage: Secondary memory offers a substantial storage capacity, capable of accommodating vast amounts of data, including audio files, films, photographs, and more.
3. Portable: Some kinds of secondary memory devices can be detached from one computer and transferred to another.

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Types of Secondary Memory

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There are two types of secondary memory on computers: fixed storage and removal storage.

1. Fixed Storage

A fixed storage device for secondary memory is a device that is used to store data in a computer and electronic systems. Fixed storage is called by the names hard drives or fixed disc drives.

• The removal of the fixed storage device requires the assistance of an expert or engineer. 
• It is generally removed only for repairs, upgrades, or maintenance.
• The fixed storage devices include SSD (solid-state disk), Hard disk drives (HDD), and Internal flash memory (rare).

2. Removable Storage

A removable storage device is an external media device utilized to store data in secondary memory on a computer system or any other electronic system. It is also called a disk drive or an external drive. It offers simple insertion and removal from the computer.

• Installation and removal are hassle-free without expertise.
• It facilitates easy data transfer between computers.
• Some removable storage devices provide high data and information transfer speeds - storage area networks (or SANs).
• The common removable storage devices like Optical discs (DVDs, CDs, Blu-ray discs), Floppy disks, Memory cards, Disk packs, Magnetic tapes, and Paper storage (punched cards, punched tapes)

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Common Removable Storage Devices

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Below are some of the common removable storage devices:

1. Floppy Disk

It is a magnetic disc housed in a square plastic container. It facilitates data storage and transfer among different devices. Commonly there are two sizes of floppy discs (i) Size: 3.5 inches, 1.44 MB storage capacity (ii) Size: 5.25 inches and 1.2 MB storage capacity. A floppy disc drive is needed for using a floppy disc. Nowadays, it is replaced by DVDs, CDs, and flash drives.

Floppy Disk

2. Compact Disc

The surface of a Compact Disc or CD surface is covered in tracks and sectors. It is made of polycarbonate plastic. CDs store data up to 700 MB. A CD-ROM (Compact Disc Read-Only Memory) can read the data but cannot write new data onto it. CDs are of two types:

CD-R or compact disc recordable: It can only be readable. It is not possible to remove data from it. CD-RW, compact disc rewritable, or Erasable CD.: It can be used to wipe and rewrite data as many times as required.

Compact Disc

3. Digital Versatile Disc

DVD means Digital Versatile Disc. It has a larger storage capacity of up to 4.7 GB. A DVD-ROM drive is required to run DVDs Movies and video recordings on DVDs can be played with a DVD player. DVDs are of three different:

• DVD-ROM or Digital Versatile Disc Read-Only Memory: The users can only read it and cannot create new data on it.
• DVD-R or Digital Versatile Disc Recordable: Data can be written only once. It can neither be erased nor written once again.
• DVD-RW or Digital Versatile Disc RW (ReWritable and Erasable): Data can be wiped and rewritten as many times as required.

Digital Versatile Disc

4. Blu-ray Disc

Blu-ray discs resemble a CD/VD. It can store data only up to 25 GB. It is read by a Blu-ray reader.

Blu-ray Disc

5. Hard Disc

Hard discs store a lot of information. Their storage capacities maybe 256 GB, 500 GB, 1 TB, and 2 TB. Hard discs are made up of a collection of discs called platters. The platters are arranged in a stacked configuration. They have several invisible circles with the same central track through the magnetic coating. Hard discs can be internal or external.

Hard Disc

6. Flash Drive

Pen drives offer data storage capacities ranging from 1 GB to 1 TB. It enables effortless data transfer between devices. It is very popular as it is simple to use and small in size.

Flash Drive

7. Solid-state Disc

The Solid-state Disk (SSD) serves as a non-volatile storage and retrieval device for data. It is faster, makes no noise, and uses less electricity. It is ideal for tablets, notebooks, and other devices that require less storage.

8. SD Card

A Secure Digital Card (SD Card) is used to store data in cell phones and cameras. It may have a storage capacity of 1, 2, 4, 8, 16, 32, and 64 GB. It can be used on a computer using a card reader.

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Things to Remember

• Memory serves as a physical device utilized to temporarily or permanently store programs or data.
• Secondary memory has a bigger storage capacity. It stores data and programs permanently even after turning off the computer.
• Data in a computer system is stored using a fixed storage device for secondary memory.
• A removable storage device is employed to store data in secondary memory on a computer system.
• CD-R or compact disc recordable can only be readable. It is not possible to remove data from it.
• CD-RW, compact disc rewritable, or Erasable CD can be used to wipe and rewrite data as many times as required.
• A flash drive or pen drive is the easiest means to transfer data from one device to the other.
• A Solid-state Disk (SSD) functions as a non-volatile device for data storage and retrieval.
• A Secure Digital Card (SD Card) is used to store data in cell phones and cameras.