Storage devices are also called storage media. It is a hardware device that can hold information. Two main storage devices are used in computers. The primary storage device also known as RAM and the secondary storage device such as a computer hard drive. Secondary storage can be either internal or external storage. Storage device is required by the computer to save any settings or additional information. Following are the different types of computer Storage Devices/Secondary memories –
Secondary Memory devices includes:
A. Magnetic Disks : Magnetic disks play two roles in computer systems:
• Long-term, nonvolatile storage for files, even when no programs are running
• A level of the memory hierarchy below main memory used as a backing store for virtual memory during program execution A magnetic disk consists of a collection of platters (generally 1 to 12), rotating on a spindle at 3,600 to 15,000 revolutions per minute (RPM). These platters are metal or glass disks covered with magnetic recording material on both sides, so 10 platters have 20 recording surfaces. The disk surface is divided into concentric circles, called tracks. Each track in turn is divided into sectors. A sector is the smallest unit that can be read or written.
B. Optical Disks : Optical disks are another type of secondary memory. Many types of optical disks are available in the market like CD(Compact disks), DVD (Digital versatile disks) etc. CD-R are write once CDs i.e. data can be written to them only once. CD-RW on the other hand are rewritable CDs i.e. data can be written and erased many times. Similar variations DVD-R and DVD-RW are also available in the market.
C. Magnetic Tape : Magnetic tape is a long and narrow strip of plastic that thin magnetic material is coated on. Nearly all recording tape is of this type, whether used for recording audio or video or computer data storage.
Magnetic tape recording uses magnetic tape which moves on a recording head. Electrical signals are fed to the recording head, inducing a pattern of magnetization similar to the signal. A playback head can then pick up the changes in magnetic field from the tape and convert it into an electrical signal.
D. Floppy diskette : A Floppy Disk Drive is a computer disk drive that helps a user to save data to removable diskettes. 8 inch disk drives were first made available in 1971, which were later replaced with 3 ½ inch floppy disk drives. Due to the limited capacity and reliability of floppy diskettes in many computers they are no longer used with floppy disk drives . They are being replaced with CD-R, other writable discs, and flash drives.
E. CD-ROM disc : Compact Disc-Read Only Memory, CD-ROM drives or optical drives are CD players inside computers that can have speeds in the range from 1x and beyond, and have the capability of playing audio CDs and computer data CDs.
F. CD-R and CD-RW disc : It is also called as a CD writer, CD-WO (Write once), WORM (Write Once Read Many) drive. CD-R is used for CD-Recordable and is a writable disc and drive that is capable of having information written to the disc once and then having that disc read many times after that. If the data is not written to the disc properly, has errors, or has the incorrect information that disc or portions of that disc cannot be erased and is often jokingly referred to as a coaster.
G. Recordable DVD (Digital video Disk) drives : These DVD drives are alternatively referred to as a DVD writer, recordable DVD drives. The recordable DVD drives are capable of creating DVD discs. They are different from recordable CD drives as they have many different competing standards for creating DVD discs. For example, DVD-R, DVD-RW, DVD + R, DVD + RW, DVD + R DL (DVD + R9), and DVD-RAM are all different competing standards.
(i) DVD-R DVD-R is called as Digital Versatile Disc-Recordable. DVD-R has features similar to CDR, where the drive is capable or recording once to a disc and then read many times after it has been created. DVD-R is an approved standard by DVD Forum and the drives are capable of recording to DVD-R discs. These discs are also known as DVD-5 and DVD -10. DVD-R discs are compatible with most stand alone DVD players and computer DVD-ROM drives.
(ii) DVD-RW (DVD-R/W) These are called as Digital Versatile Disc-Read/Write. DVD-RW is an approved standard by DVD Forum.It is based on a technology that enables a user to read and write to a DVD-RW or DVD-R disc several times. DVD-RW discs are compatible with most stand-alone DVD players and computer DVD-ROM drives.
H. Jump drive and USB flash drive : USB flash drive is a portable drive that is as small as the size of your thumb. Other such portable drives include data stick, pen drive, keychain drive ,thumb drive .It connects
to the computer USB port. Flash drives are available in different sizes such as 256MB, 512MB, 1GB, 5GB, and 16GB . They can easily store and transfer information. A flash drive is used by inserting it onto the front or back of USB port or hub. After inserting the flash drive , open the My Computer , you can see as “Removeable Disk”, “Flash drive”, or as the manufacturer’s
name. When the drive has been identified , data can be copied onto the flash drive by a simple copy paste or just dragging and dropping onto the flash drive icon.
I. Hard Drive : It is called as the hard disk drive. It is represented sometimes by its short name as HD or HDD. It is the computer’s main storage area that permanently stores the data on to the computer. It
consists of one or more hard drive platters inside of air sealed casing. The hard drives are contained in an internal drive bay at the front of the computer . They connect to the mother board using ATA, SCSI or a SATA cable .
J. Memory card : These are referred to as a flash memory card or a memory card . The memory card type of storage media is used in digital cameras, digital camcorders, handheld computers,printers , MP3 players
and cell phones. They can store a huge number of pictures, videos, music, and other data. MicroSD flash memory card is one such example of a memory card . There are a number of different types of memory cards in the market that vary in size, compatibility, and storage capacity.
K. Memory stick : Sony Memory Stick was first invented by Sony in October 1998 . It is a flash memory card used with Sony digital cameras . This flash memory card is used with other Sony products also. The capacity of the Memory Sticks range from sizes of 4MB to 256GB . They can have maximum capacity of 2TB, although till now the sticks of this capacity have not been produced .
A tape cassette is magnetically thin coated piece that is wrapped with plastic around wheels. These are capable of storing data. Tape is far cheaper than other storage mediums but is much slower than the jump drives , memory sticks etc . Tapes are not much in use these days for faster and more reliable solutions like disc drives, hard drives, and flash drives.
L. Zip Diskette : Zip Diskette are made out of a much harder plastic and are much bigger than the standard floppy diskette. Zip drive is a medium capacity removable floppy disk storage system. Zip drives are not much in use because of need of mass portable storage .
M. Blue ray disk : Blu-ray (not Blue-ray) also known as Blu-ray Disc (BD), is the name of a new optical disc format jointly developed by the Blu-ray Disc Association (BDA), a group of the world’s leading consumer electronics, personal computer and media manufacturers (including Apple, Dell, Hitachi, HP, JVC, LG, Mitsubishi, Panasonic, Pioneer, Philips, Samsung, Sharp, Sony, TDK and Thomson). The format was developed to enable recording, rewriting and playback of high-definition video (HD), as well
as storing large amounts of data. The format offers more than five times the storage capacity of traditional DVDs and can hold up to 25GB on a single-layer disc and 50GB on a dual-layer disc. This extra capacity combined with the use of advanced video and audio codecs will offer consumers an unprecedented HD experience.