For the record, buyers: Check the fine print of the ABCs of CDs

Government buyers should keep an eye on CD-ROM advances if they don't want to get
caught in a couple of years as the proud owners of the only remaining technology-X drives.


Digital video (or versatile) disks, or DVDs, are getting a big marketing push this
year. Even though there's an accepted industry standard for read-only DVD (DVD-ROM), don't
look for writable or rewritable DVD-RAM to become widely available for another two years.


That's a big disadvantage for those thinking of buying into DVD early. It's wise not to
bet on a technology that won't appear for another year, even if promised by companies with
solid track records.


Panasonic Communications and Systems Co. probably will have delivered its first DVD-ROM
by the time you read this. Toshiba America Information Systems Inc. has announced plans to
ship a DVD-RAM recordable/rewritable drive in 1998.


Meanwhile, with CD-ROM and CD-recordable already enjoying a large installed base, the
arrival of standard rewritable CD-RW drives should give a big boost to CD-ROM technology.


The only edge held by the current PD phase-change drives is their ability to reuse
space on the disk. PD drives can write and erase PD disks, which can only be read by other
PD drives. But PD drives also can read standard CDs.


Hewlett-Packard Co., Philips Electronics Inc., Sony Corp. and other big players settled
last fall on a standard for rewritable CD-ROMs. CD-RW is based on the Universal Disk
Format standard established by the Optical Storage Technology Association. Look for CD-RW
drives to appear by March, with prices dropping below $450 by autumn.


The CD-RWs won't be backward-compatible with all CD-ROM drives because they are
multisession disks and because their phase-change surface has lower reflectivity than
CD-ROMs or CD-Rs. But the RW disks can be read by DVD-ROM drives, CD-ROM multisession
drives with automatic gain control and the new CD-RW drives.


CD-Rs can't be erased. But if compatibility with old CD-ROM drives isn't required, you
can write separate files to a CD-R, creating what is known as a multisession disk. The new
CD-RW drives will be able to read standard CDs and CD-R write-once disks recorded as
multisession disks.


It may seem that CD-RW is no more compatible with older CDs than DVD-RAM will be. I
understand that a CD-RW drive can be used to create completely CD-ROM-compatible disks--as
long as you use a CD-R blank instead of a CD-RW blank.


CD-RW appears to offer the best of both worlds: It will read and write
CD-ROM-compatible disks, and it will operate as a removable-media rewritable drive, too.


If you publish data for a variety of users or create archival disks with CD-R blanks,
you can even do something that current PD users can't do. To enjoy the economy and
convenience of a rewritable drive, just insert a CD-RW disk instead of a CD-R blank.


CD-RW seems to be a formidable competitor to current PD drives and the expected 1998
crop of DVD-RAM drives.


John McCormick, a free-lance writer and computer consultant, has been working with
computers since the early 1960s. Write to him care of Government Computer News, 8601
Georgia Ave., Suite 300, Silver Spring, Md. 20910.


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