If you're crawling in data, but afraid to toss any of it away, keep your eye on the WORM. Computer disks and microfiche or microfilm are slow when you're talking about mountains of data. But for data that you may need to use again or find fast, a WORM may be the way to go.

A WORM is a bit like CD-ROM, which we explained in previous columns. The ROM in CD-ROM stands for `read only memory.' Your computer can show onscreen what's on a CD-ROM and copy its numbers, words or images. But it can't make even an iota of addition or change to data on the CD-ROM disk.Imagine if you could use CDs to back up your data: One CD could hold the equivalent of about 1,500 floppy disks! That's at least 250,000 paper sheets of information. You could throw away those ugly file cabinets! A small bookshelf could store a lifetime of personal or corporate information. You could search a disk in seconds for any data.

Your wish is technology's command. CD-WORM is here.

WORM stands for Write Once Read Many. For now, it's completely incompatible with CD-ROM. The hardware is different, the software is different, even the disks are different - thicker, with no hole in the middle. (Adding to the confusion, several optical WORM systems use tape cartridges instead of disks.) The WORM market is a free-for-all. There are already almost 100 brands of WORM disk drives. Some work with IBM compatibles (solo or networked), some with Macintosh, others with IBM or Hewlett-Packard minicomputers.

Some WORM drives, including Sony, Ricoh and Canon, use a type of tracking to find and `play' data called `continuous composite servo' or CCS. Others, such as Pioneer, use a `sampled servo' format. Two makers' systems seldom can read each other's data.

For personal computers, external and internal drives are also made by Panasonic, Mitsubishi and other electronics names. Most use 5.25 or 3.5-inch disks, but there's also a credit-card size for some laptops.

For $15,000, Aquidneck makes an external IBM compatible drive that writes once (and then reads) to 12-inch disks. A 12-incher stores about as much as four comparable 5.25-inchers.

Some external drives look like stand-alone floppy drives, others like home CD players. Most WORM drives in 3.5- or 5.25-inch format generally cost upwards of $3,000, plus $300 and up for the computer interface board that makes them compatible with a particular computer type. That's about three times the cost of CD-ROM players.

WORM drives and disks come in four additional sizes. Most are for use with minicomputers and mainframes. For them, big cabinets store 150 or more large CD-WORM disks. They're are often called `carousels' or `jukeboxes.' Aquidneck's 150-platter jukebox holds a terabyte of data, about a million megabytes! (Aquidneck: 401-295-2691) Many jukeboxes do more than store disks; they include one or more built-in WORM drives plus a mechanism that selects disks for play. With several drives, several computer users can use unrelated WORM disks at the same time.

Once you get into jukeboxes, prices soar. Panasonic's 50-platter, two-drive model costs $40,000. Blank WORM disks cost more than $100 each; we expect that for the more popular sizes, the price will plummet by 1992 or '93, but not to the $8 or $10 CD-ROMs will soon sell at.

Since a computer is brainless without software, you need a program to move computer data onto a WORM disk ("write' it) and then search the disk for particular information and `read' it into computer RAM memory.

Many drives come with bundled software. Lots of programs are sold separately, too. Some of the programs can only read words and numbers; others can read pictures ("images") too.

Alexsys's (301-740-8715) prices are typical in the PC world. A simple singler-user version costs $250. A $13,000 version serves 10 stations on a network; it can search as well as save data and retrieve data on WORMs at the same time.

There's even a program, $675 Unlimited Driver from Semaphore Image (415-461-1890) that uses your favorite database for search and retrieval. For minis and mainframes, prices are exponentially greater.

Until just a few weeks ago, most folks (including us) thought WORM storage was non-erasing and tamper-proof. It seemed a space-saving way to hold onto files we might have to produce someday, since disks take 10 to 30 years to wear out. (Legal reasons alone prompt up to 95 percent of all the paper and disk backups that clog offices.) But an Aug. 27 Infoworld article quoted WORM drive salesman John Dean as saying, `We've been misleading the public.' It seems, a techie can easily alter WORM data. The article gave complete instructions for potential mischief-makers.

That being the case, we're changing our thinking. You may want to change yours too.

As with any rapidly changing technology, don't buy before your investment can pay for itself. The announcement about WORMs not being tamperproof is sure to shake up this industry. In fact, Pioneer and Laser Magnetic Storage just announced combination drives for IBM compatibles and Macs that accept both WORM and Magneto-Optical Rewritable disks. Pioneer's costs $4,500. The MOR disks use yet another variant on CD technology to cram gigabytes of data onto disks - and to write over it just like any ordinary computer disk.