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Getting a Clear Picture of Optical Storage.

Traditionally, personal computers have used the physics of magnetism as the primary means of storing programs and data for later use. Floppy disks, hard disks, Zip disks and backup tapes all work by magnetizing small areas on the surface of the disk. But in recent years magnetism has been complemented by optics as a storage mechanism. High-intensity light sources like lasers burn information into the disc surface. (Disks [hat employ magnetism are spelled with a "k" at the end; discs that use optics typically end with a "c.")

A myriad of optical technologies is available, including CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-R, DVD-RAM, and DVD-RW, with more on the way. You might think that making sense of these acronyms requires an advanced degree, but not necessarily.

CD-ROM was the first popular optical disc technology used with PCs. CD-ROM stands for Compact Disc Read-Only Memory, which means your computer can read data from these discs but can't write data back.

These discs hold 650 megabytes of data, one megabyte (MB) being about one million bytes, and a byte being equivalent to an alphabetical letter or a numeral. You can store 600,000 typewritten pages on one of these discs.

Most computers today still come with CD-ROM drives -- mechanisms that spin the discs -- but new technology called CD-R is surpassing the CD-ROM.

CD-R is a newer technology that overcame CD-ROM's read-only limitation -- CD-R stands for Compact Disc Recordable. Popular uses are copying music and archiving data.

The best feature of these discs is their low cost, about 20 cents in bulk. The biggest limitation is that you can only record data once. CD-R drives can read both CD-R and CD-ROM discs.

CD-RW is a Compact Disc Rewritable. CD-RW outstrips the write-once limitation of CD-R, allowing you to rewrite and erase data multiple times. It's an increasingly popular technology in new PCs, in many cases replacing Zip and tape backup drives.

CD-RW now has a cost advantage over Zip for backing up data or moving it from one PC to another. CD-RW drives cost twice that of Zip drives, but the discs themselves are 10 times less expensive than the Zip discs and have two times more capacity.

The latest CD-RW drives are as fast in reading data as Zip drives and nearly as fast in writing data. They're faster than tape backup drives and more versatile. CD-RW drives can write to CD-R or CD-RW disks.

DVD-ROM is a technology that promised much but never quite lived up to its potential. Standing for Digital Versatile Disk Read-Only Memory, DVD-ROM uses discs similar to CD-ROM discs, but they typically hold seven to eight times more data.

Despite the greater capacity of DVD-ROMs, software makers have continued to distribute their programs primarily on CD-ROMs because of the ubiquity of CD-ROM drives. DVD-ROM drives can be useful for watching DVD movies on your PC or playing computer games.

DVD-ROM drives, like CD-ROM drives, can't record data, though they can read most types of CD and DVD discs. The speed ratings of DVD-ROM drives aren't comparable with those of CD-ROM drives -- a 12X DVD-ROM drive is faster than a 48X CD-ROM drive.

DVD-R is similar to CD-R, allowing you to record data onto discs, but only once. DVD-R discs currently have seven to eight times the capacity of CD-R discs, though both the drives and the discs are more expensive, the discs costing about $12 each. DVD-R drives can create CD-R discs and create or rewrite CD-RW discs.

DVD-RAM is a competing but incompatible technology. You can't read DVD-RAM discs with most other DVD drives, and DVD-RAM drives can't create discs readable by CD-ROM drives or CD players, a big limitation compared with DVD-R.

DVD-RW lets you record, erase, and rerecord data, but because it is so new, it's also pricey, the discs costing $20 to $35 each. Some DVD-ROM drives can't read DVD-RW discs that have been written to multiple times.

Of the above technologies, CD-RW and DVD-ROM are the most versatile, compatible, and cost-effective choices. Regarding the newer DVD technologies, "it's impossible to call a winner," said Mary Craig, optical storage analyst for Gartner Dataquest, a market research firm in San Jose, Calif.

Unless you need to buy immediately, your best bet is to wait to see which technologies the major computer companies adopt.

Reid Goldsborough is a syndicated columnist and author of the book STRAIGHT TALK ABOUT THE INFORMATION SUPERHIGHWAY. He can be reached at or
COPYRIGHT 2001 Autumn Publishing
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Copyright 2001 Gale, Cengage Learning. All rights reserved.

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Publication:Community College Week
Article Type:Brief Article
Geographic Code:1USA
Date:Aug 20, 2001
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