Secondary memory

Secondary Memory is the external storage device of the computer. It is also called the computer's auxiliary storage device. Secondary Memory is a permanent storage device because the data stored in it is not deleted even when the computer is turned off. When needed, the user can open and view the store data in secondary memory and change it and also delete it. The storage capacity of secondary memory is higher than primary memory but it has a slower speed of data transfer. Floppy disk, hard disk, CD / DVD, Pen drive, memory card etc. are called secondary memory. Because they are planted separately.

Types of Secondary Memory

There are four types of Secondary memory:~

1. Magnetic Tape

2. Magnetic Disk

3. Optical Disk

4. Flash Drive

1. Magnetic tape:~ Magnetic tape was just like a cassette of a tape recorder. A plastic ribbon of magnetic tape was coated with magnetic material (iron oxide and chromium oxide). On which electronic head was used to store data. The data stored on the magnetic tape is called a record. Many times data could be stored and erased on magnetic tape. Magnetic tapes were very cheap. But now its use has stopped completely.

2. Magnetic disk

There are two types of magnetic disks:~

1. Floppy Disk

2. Hard Disk Drive

1. Floppy Disk :~ The floppy disk was a very thin plastic round disk, which was closed in a plastic cover. A layer of magnetic material was mounted on the floppy disk, on which the data was stored. A floppy disk reader was used in computers to read data stored in a floppy disk. A floppy disk is a computer's storage device, which was used to store data in a computer. A floppy disk is part of secondary memory or external memory.

Floppy disks are of two types based on size and storage capacity :~

1. Mini Floppy Disk :~ The mini floppy disk is 3.5 inches in diameter and has a storage capacity of 1.44 MB. The mini floppy disk rotates at a speed of around 360 RPM(revolution per minute).

2. Micro Floppy Disk :~ The micro floppy disk is 5.5 inches in diameter and has a storage capacity of 2.88 MB. It has the same speed as a mini floppy disk.

2. Hard Disk Drive :~ Hard disk drive is a secondary storage device of a computer. Which is used to store data in a computer. The world's first hard disk drive was built by IBM (International Business Machine) in the 1960s. A hard disk drive is an aluminum disk, which is coated with material. This disk rotates very rapidly on one axis and its speed is measured in RPM. Hard disk drives with speeds of 7200 RPM and 5200 RPM are available. The first hard disk drive had a storage capacity of 5MB. And its weight was 250 kg. The storage capacity of hard disk drives is very high. Currently, hard disks ranging from 1 tera byte to 100 tera bytes are available in the market. Hard disk drives store and read data faster. The first partition of the hard disk drive in the 80s was named 'C' drive. When Windows is installed in a computer, it is first installed in the 'C' drive. Computer operating system, software and many types of applications are stored on the hard drive. Hard disk drive stores data digitally.

3. Optical Disk :~ The optical disc is a round disk of polycarbonate on which the chemical material is coated. An optical disk is an electronic secondary storage device. The world's first optical disc was made in 1960 by James T. Russell. Optical disks take longer to read and write data than magnetic disks, but large amounts of data can be stored in optical disks. Laser beams are used to write and read data in optical discs, so optical discs are also called laser discs.

There are three types of optical discs:~

1. CD 2. DVD 3. BLU Ray Disk

1. CD :~ The ability to store data in a compact disk is 700 MB. Compact discs are small and portable. Data in a compact disk is preserved for about 30 years. But it is difficult to read the data due to a scratch on its surface. Infrared laser beam are used to store data in compact discs. Compact disks are used to store software, audio and video. The data stored in the compact disk cannot be changed or deleted.

2. DVD :~ The full name of DVD is Digital Versatile Disc. DVD and CD are similar in viewing. But DVD storage capacity is high. DVD storage capacities range from 4.7 GB to 17 GB. DVDs are typically used to store movies.

3. BLU Ray Disk :~ Blu ray disc is a type of optical secondary storage device. Which is like cd and DVD in view. The Blue Violet Laser Rays is used to store data in a Blu ray disc. The storage capacity of Blu-ray Discs from 25 GB to 250 GB

Flash Drive/Pen Drive

The pen drive is the most popular and portable storage device in the world. A pen drive is a secondary storage device or external storage device. Pen drives are used by plugging them into the computer via a USB (universal serial bus) port. Pen drives are used to store and transfer data to personal computers. Pen drives are also used to put passwords in computers. New data can be stored repeatedly by deleting old data in the pen drive. The pen drive is small in size and can be easily carried from one place to another by placing it in a pocket. The storage capacity of pen drive is very high and its speed is very fast.

Memory Card/Flash Memory Card

Memory card is also called flash memory card. Memory cards are used to store data such as photos, videos, music, files, etc. Memory cards are mostly used in electronic devices such as mobile phones, cameras, music players, etc. The memory card is smaller in size than the pen drive. Memory card is also a rewritable storage device in which data can be erased repeatedly and new data can be stored.