The last thing any of us needs is another fragment of high-tech jargon to memorize, and the phrase "CD-ROM" might sound at first blush like an eminently forgettable piece of jargon. But you'd better remember "CD-ROM"; it's going to play a fundamentally important role in increasing the power and usefulness of your personal computer.

"CD-ROM" is the techies' short-hand term for "Compact Disk Read-Only Memory" -- an extremely compact new form of data storage. You might say that CD-ROM is an expanded form of floppy disk, but that's about as accurate as saying the Empire State Building is an expanded form of broom closet.

The CD-ROM disks on the market for personal computers today have a storage capacity of about 550 megabytes of data -- that is, one 5 1/4-inch CD-ROM disk can hold as much information as 1,600 or so standard floppies. Quite soon, CD-ROM capacities will reach the "gigabyte" level: a billion characters on a single disk.

Such a disk could store every letter, number, space and punctuation mark in today's newspaper -- and still have room for about 999 more complete newspapers. Whole encyclopedias can be reproduced on a single CD-ROM disk, as can the complete Tokyo telephone directory or the staffing charts of every federal agency.

CD-ROM technology means, in short, that huge collections of information -- much more than can be stored on the shelves of your home or office library -- will be available to anyone with a personal computer. And the computer's data-management power -- its ability to sift rapidly through zillions of words and find every occurrence of the phrase you're searching for -- will make the information easier to get at than it is in that centuries-old storage medium called the "book."

This near-quantum leap in storage capacity stems from the completely different technology used in CD-ROM storage. The floppy and hard disks familiar to microcomputer users today are magnetic devices. The physics of magnetic fields limit their density, and the vulnerability of a magnetic charge makes current disks, like those floppies on your desk, extremely sensitive. As most computer addicts have learned the hard way, even a slight touch in the wrong spot can trash all the data on a floppy disk. CD-ROM, in contrast, is an optical, or laser-made, storage medium.

Information is stored on the disk by laser beams cutting minute pits in the disk surface. The pits can be packed hundreds of times more tightly than the magnetic fields on a floppy disk. And once the laser disk is made, it can't be injured by an errant finger or a spilled cup of coffee. In fact, CD-ROM makers encourage owners to wash the disks now and then in hot soapy water, a procedure not exactly recommended for floppy disks.

CD-ROM computer storage is a technological stepchild of audio-compact disks, a similar laser-storage medium. The audio business already has worked out many of the technical problems of this new medium, which could be good news for the personal-computer side of the deal; for once, we may not have to suffer through years of technical trouble to take advantage of a useful new tool.

In fact, although CD-ROM computer storage is in its infancy, there's a fairly broad choice already of hardware and software for people who want, for example, instant access to a catalogue of every painting in the National Gallery of Art or a complete shelf list (6.5 million titles) of the Library of Congress (available from International Thomson Library Service in Arlington, Va.).

To use CD-ROM disks on your personal computer, you have to buy a fancy new disk drive unit; your audio CD player won't work, although it's safe to assume that there soon will be players that can feed either an audio system or a computer. There are several CD-ROM drives on the market now for IBM-PCs (Hitachi, Digital Equipment and Tecmar are among the makers). An outfit called MicroTRENDS (Schaumburg, Ill.) has a system for the Apple IIe, and a KnowledgeSet Corp. (Monterey, Calif.) has a CD-ROM drive for the Atari ST. Prices are just under $1,000 per drive now, but this price surely will fall.

A growing range of information is available in CD-ROM form, ranging from the complete Academic American Encyclopedia (Grolier, Danbury, Conn., $95) to the International Dissertations Abstract (University Microfilms, Ann Arbor). To date, the disks seem to store mainly words; Microsoft, though, has demonstrated CD-ROM storage of pictures and sound as well. When you call up the encyclopedia entry on Richard Nixon, for example, you'll see and hear him reciting the deathless phrase, "I am not a crook."

This is not dreamy futurology; CD-ROM storage is here now for personal computers. Over time -- say, the next year or two -- it's going to add enormously to the power and the sheer fun of the microcomputer revolution we're lucky enough to be living through.