Like papers on your desk, computer data has to be stored someplace. Memory in a computer is stored in a variety of magnetic and electronic forms.

A disk drive records the binary data onto a constantly spinning disk. Most computers are equipped with a hard drive, and many still have a floppy disk drive as standard equipment. A hard disk is "fixed" or permanently installed inside your computer cabinet; a floppy drive may also be installed inside your computer, but it uses a removable disk.

You can attach multiple additional disk drives. Each drive receives a letter designation (C: drive, J: drive, etc.) to differentiate them from other disk drives.

You may have noticed that the word "disk" is alternately spelled "disc." Disk with a "k" refers to magnetic computer storage media. Disc with a "c" refers to optical, A/V media like CDs.

Floppy Disks

Floppy disks are 3.5 inches square, comprised of a thin, circular, coated Mylar sheet set on a center spindle inside a soft, pliable plastic case with a sliding metal door on one side. The computer opens that door to gain access to the Mylar sheet, the actual magnetic disk media.

Floppy disks come in several memory sizes: Single-density (SD) disks hold 400 K (400,000 characters), double-density (DD) 700 K and high-density (HD) hold 1.4 MB. Late-model computers read all three sizes, but older machines cannot read high density disks.

Macintosh and IBM-compatible computers use the same floppy disks, but each computer formats them differently. Your computer can format blank disks, though some disk manufacturers preformat them for one system or the other so the disks are ready for immediate use.

Fixed Hard Disks

A fixed hard disk is permanently assembled into its drive mechanism - "fixed" to differentiate from removable hard disks. It may be an internal disk drive, built into your computer, or an external drive that attaches to your CPU via a serial cable.

A 1 GB fixed hard disk can hold hundreds of millions of characters. A home office that maintains a large database, does desktop publishing or has more than one user may need ten times that amount of hard disk storage space. Most computers come equipped with multi-gigabyte fixed hard drives. You can add drives if you need them.

Most manufacturers offer external disk drives compatible with their computers. A hard drive designed for an IBM-compatible computer will not work with a Macintosh, and vice versa.

As with most peripherals, you will need special "driver" software (Macintosh) or an expansion controller card (IBM) to connect and use an external hard disk drive.

Removable Hard Disks

"Removable" hard disk drives are compromises between the high capacity of fixed hard drives and the portable convenience of floppy disks.

These removable cartridges can store anywhere from 100MB to several gigabytes of information on a single disk at a low relative cost. Some manufacturers include a high-capacity removable disk drive along with fixed and floppy drives on their computers.

The purpose for these high capacity disks was for the easy transport of large files often created in graphics.

Their capacity and convenience has, in many cases, supplanted the need for floppy disks.

Backup Tape Drives

Special magnetic tape can be used for data storage. A data tape cassette can hold much more information in a smaller space than a hard disk drive or floppy disk. But because access time depends on physical rewinding and fast forwarding, tape drives are used primarily for backup.

Backup means making a copy of all your data in case your regular hard drive becomes damaged or your computer crashes, which can destroy parts or all of your memory. You rerecord all your data onto a tape and put it away "just in case."

If you are working on a long document, be sure to make a backup copy at the end of each work session.

Optical Drives

CD-ROM drives are usually standard equipment in new PCs and most newer software applications are available on CD-ROM. A CD-ROM can hold 650 megabytes of prerecorded data.

CD-ROM drives access data faster if the disk spins faster. Therefore, many optical drives note that they are "6X" or "126X" drives, meaning they spin six times or twelve times faster than standard, which increases the speed at which information is transferred to screen.

CD-R (CD recordable) and CD-RW (CD rewritable) drives enable you to burn (record) your own discs. A CD-R disc, once recorded, cannot be un-recorded; these are known as "WORM" discs (write-once, read many). CD-R discs are widely available and usually cost less than a dollar each. CD-RW disks are more expensive, but can be recorded over and over.

A DVD-ROM can hold from 5GB to 17GB of data. A DVD-ROM drive can actually play back Hollywood movies, though resolution may be limited by the processing power of the personal computer.

DVD-ROM drives can read CD-ROMs, but CD-ROM drives cannot read DVD-ROMs.

DVD-ROM drives are available mostly as external drives on high-end PCs, but this should change over time.

Maintenance

You can clean the heads of your disk drive without taking the back or front off your computer or disk drive cabinet. Read your instruction manual. The manufacturer may recommend a head-cleaning kit. These are usually available from retailers who sell and service your brand.

If you have trouble formatting a disk, your disk drive system may need to be cleaned. Follow the instruction manual or check with your retailer.

Magnetic disks are more prone to damage and require more preventive maintenance than your drives. Storage containers protect your disks from magnetic fields and damage or accidental erasure.

To make disks last longer, take these precautions:

• Write on the disk label before you attach it to the disk.
• Once the label is attached, write on the disk label with a felt-tip pen, not a ballpoint.
• Don't place a new label on top of an old one, and don't cover any jacket holes or openings when you attach the label.
• Don't touch the magnetic surface.
• Don't bend the disk or attach notes to it with paper clips.
• Don't force a disk into a disk drive.
• Don't put magnets on a disk, and keep disks at least three inches away from magnetic fields, such as stereo or TV speakers or transformers.
• Don't leave a disk in direct sunlight.
• Don't smoke around your disks.
• Don't place anything on top of a disk (tools or books, for example).
• Try not to expose disks or data cartridge tapes to extreme hot or cold. If you do, leave them at room temperature at least two hours before using.
• If chocolate, correction fluid, or other non-water-soluble liquids or materials spill on your disks, contact the manufacturer for advice on removing them. Inserting contaminated disks into your computer may damage your disk drive. Some disk manufacturers may recover your data from and replace a contaminated disk.
• Clean the recording head of a data cartridge tape backup system with an approved head cleaner after each eight hours of use. Exercise data cartridge tapes before using them. Fast forward and reverse them for one complete cycle.