Reading. Read the text and try to guess the meaning of the words in bold font. Check your variants in the dictionary. STORAGE DEVICES

A data storage system has two main components: a storage medium and a storage device. A storage medium (storage media is the plural) is the disk, tape, CD, DVD, or other substances that contains data. A storage device is the mechanical apparatus that records and retrieves data from a storage medium. Storage devices include hard disk drives, tape drives, CD drives, and DVD drives. The term “storage technology” refers to a storage device and the media it uses.

Floppy disks are classified as magnetic storage because data is stored by magnetizing microscopic particles on the disk surface. A floppy disk is a round piece of flexible mylar plastic covered with a thin layer of magnetic oxide and sealed inside a protective casing.

Hard disk technology is the preferred type of main storage for most computer systems. A hard disk is one or more platters and their associated read-write heads. A hard disk platter is a flat, rigid disk made of aluminum or glass and coated with magnetic iron oxide particles. Hard disk platters are sealed inside the drive case or cartridge to screen out dust and other contaminants. The sealed case contains disk platters and read-write heads. Each platter has a read-write head that hovers over the surface to read data. The drive spindle supports one or more hard disk platters. Both sides of the platter are used for data storage. More platters mean more data storage capacity. Hard disk platters rotate as a unit on the spindle to position read-write heads over specific data. The platters spin continuously, making thousands of rotations per minute. Each data storage surface has its own read-write head, which moves in and out from the center of the disk to locate data. The head hovers only a few microinches above the disk surface, so the magnetic field is more compact than on a floppy disk. As a result, more data is packed into a smaller area on a hard disk platter. The density of particles on the disk surface provides hard disks with capacities far greater than floppy disks. Also, the access time for a hard disk is significantly faster than for a floppy disk.

A head crash can easily destroy hard disk data. A tape backup is a copy of the data on a hard disk, which is stored on magnetic tape and used to restore lost data. A tape backup device can simplify the task of reconstructing lost data. A backup tape can hold the entire contents of a hard disk.

Today, most computers are equipped with some type of optical drive – a CD drive or a DVD drive. The underlying technology for CD and DVD drives is similar, but storage capacities differ. CD and DVD drives contain a spindle that rotates the disk over a laser lens. The laser directs a beam of light toward the underside of the disk. Dark “pits” and light “lands” on the disk surface reflect the light differently. As the lens reads the disk, these differences are translated into the 0s and 1s that represent data. Optical drives use several technologies to write data on CD and DVD disks: Recordable technology (R) uses a laser to change the color in a dye layer sandwiched beneath the clear plastic disk surface. The laser creates dark spots in the dye that are read as pits. The change in the dye is permanent, so the data cannot be changed once it has been recorded. Rewritable technology (RW) uses “phase change” technology to alter a crystal structure on the disk surface. Altering the crystal structure creates patterns of light and dark spots similar to the pits and lands on a CD. The crystal structure can be changed from light to dark and back again many times, making it possible to record and modify data much like on a hard disk. Most CD drives can read CD-ROM, CD-R, and CD-RW disks, but cannot read DVDs. Most DVD drives can read CD and DVD formats.