FIXED MAGNETIC DISKS (HARD DISKS)

FIXED MAGNETIC DISKS (HARD DISKS)

The increasing complexity of the software requires additional storage space. The user must switch floppies in and out as by the software packages. To meet this growing need for large secondary storage, the hard disks are developed. Hard disks or fixed disks, also called winchester, are premanently installed or fixed within the system unit. All fixed disks are rigid are usually made of aluminum with a surface coating of easily magnetized elements, such as iron, cobalt. Chormium or nichel a fixed disks or hard disk is a high speed, target capacity disk and is referred as a mass-storage magnetic medlum that provides computer system with the ability to read or retrieve large amount of information swquentially or randomly under the direction of a controller board. A hard disk contains several disk platters stacked on a single rotating spindle. Data are stored on all reconding surface.

For a disk with four platters, there are eitght recording surfaces on which data can be stored. The disks spin continuously at a high speed (from 3600 rpm to 6000 rpm high speed) within a sealed enclosure. The enclosure keeps the disk-face surface free from contaminations, such as dust and cigarette smoke. This contamination-free enviironment allows hard disk to have greater density of data storage than the interchangeable diskettes. In contrast to a hard disk, a diskette is set in motion only when a command is issued to read from or write to the disk. An indicator light near the disk drive is illuminated only when the floppy diskette is spinning.

COMPACT DISK

Compact disk read only memory. Systems are becoming popular, especially for use with microcomputers. These systems use a disk that is less than 5 inches in diameter and yet can hold more than 600 megabytes of data. Although these disks look just like the well known music CDs, they are used to store the kind of digital information used in computers.

The large colour graphic and video image files that are used with multimedia are often stered on optical disks. In addition, these disks can store two channels of sound just like the popular music CDs. Infact, a computer controlled CD-ROM drive can be used to play the two music channels on a standard music CD, and CD-ROM disks are now available with both the music and comuterized information about the music.

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