Storage Devices of Computer

Hello friends in this session we are discussing the storage devices also called as secondary memory. Memory is the most essential part of the computer. We need memory to store the data. This storage enables us to use the stored data in the future. Computer memory is mainly divided into two parts, primary memory and secondary memory. The memory and storage devices are measured in terms of bits and bytes.
Secondary memory or storage devices are also called Auxiliary memory, backup storage, bulk storage or mass storage of programs, data and other information. The secondary device facilitates the storing of data and instructions permanently. The size of the secondary memory is normally large and the cost is also reasonable. Some of the secondary storage devices are magnetic tape, floppy disk, hard disk, CD, DVD, etc

Storage devices of Computer

Magnetic Tape

Magnetic tapes appear similar to the tape used in music cassettes. It is a plastic tape with a magnetic coating on it. The magnetized portion of the surface refers to the bit value”1” whereas the de-magnetised portion refers to the bit value “0”. Magnetic tapes are very durable and can be erased as well as reused. They are inexpensive and reliable storage medium. They are not suitable for data files. Tapes are also slow.

Magnetic Disk

Magnetic disk are thin circular plastic plate on which some magnetic material is coated. It comes in various sizes and materials. They use the properties of magnetism to store the data on a magnetic surface. A disk pack consists of a number of such disk mounted on a central shaft. The central shaft rotates at speeds of about 7200 revolutions per minute (rpm). In disk-plate information is stored on both surfaces. The surface is further divided into a number of individual concentric circles called as tracks. The tracks are further divided into various sections called sectors.
The main advantage of such devices is high storage capacity, reliable in use and allow direct access to data. There are two types of magnetic disk.

I. Floppy Disk

A floppy disk is a round, flat piece of Mylar plastic coated with ferric oxide and encased in a protective plastic cover. It is a removable disk and is read and written by a floppy disk drive(FDD). When a user inserts a disk into the FDD, the drive grabs the disk and spins it inside its plastic jacket. Also, the drive has multiple levers that get attached to the disk.

II. Hard Disk

The hard disk is also called the drive or fixed disk, is the secondary storage unit of the computer. A hard disk can be external or internal and can hold a large amount of data. It consists of a stack of disk platters that are made up of aluminium alloy or glass substrate coated with a magnetic material and protective layers. The surface of a disk is divided into imaginary tracks and sectors. Tracks refer to the concentric circles where the data are stored .sectors refers to the number of fixed-sized areas that can be accessed by one of the disk drives read/write heads in one rotation of the disk. The storage capacity of the disk is determined as (number of tracks *number of sectors * byte per sector* number of read/write heads)

III. Optical Disk

The optical disk is a random accessed, removable disk on which data is written and read through the use of laser beam. There are different types of optical laser disks.

1. Compact Disk (CD)

CD is the most popular and the least expensive data storage medium. CD is the storage medium from which data is read and to which it is written by laser. The information stored on CD is arranged according to certain rules and is shaped like an “Optical track”, called “light rail” in a spiral shape. The depression part on the Optical track is called information pit and the flat part is called land. Pit and land are used to record information.

2. Digital Versatile Disk (DVD)

Also called as “digital video disc.” With the advances in optical disc technology, It cannot only store video program but also store music, data, along with increased use, it will be this type of CD-ROM referred to as “Digital Versatile Disc”.

3. Blue-ray Disk (BD)

Blue-ray Disc referred to as BD. BD disk features are: It consists of a thickness of 1.1 mm of the recording layer and a thickness of only O.l mm composite made of a transparent protective layer.

Flash Drive

Flash drive also called as Pen drive are typically small, lightweight, removable and re-writable. USB drives offer potential advantages over other portable storage devices, particularly the floppy disk. They are more compact, faster, hold more data and reliable due to their lack of moving parts. It comes with different capacities starting from 2GB to 64 GB. If you want to check cache memory please visit the post.

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