Experts concur that, compared with the on-and-off electrical jolts of typical work cycles, never switching off a video display terminal (VDT) can as much as double its life. Unfortunately, an image that's fixed in position (say, a data-entry form) will permanently burn its pattern into the VDT's color phosphors. Software utilities that automatically move images around, however, won't. Such conservation programs are called screen savers.

Created both by programmers and by imaginative artists using computer-animation systems, the hundreds of screen-saver displays now available constitute a desktop museum of sorts. Several are already cult classics: toasters that fly through space, an aquarium ablaze with meandering tropical fish.

To add to its extensive library, software publisher Berkeley Systems recently staged a contest among programmers and artists. From more than 150 responses, the $10,000 grand prize went to "DOS Shell," by Ed Hall, who describes his creation as "a Macintosh user's worst nightmare come true." Unlike the special-category winners, Hall's work is not so much a visual tour de force as a typewritten tease: it mocks Macintosh rival IBM's archaic character-oriented approach by appearing to peck out and execute C-prompted commands. Berkeley has acquired that and other leading entries; it has already begun offering some of the new modules and will begin rolling out the others early next year, at a price of about $50 each. (The "Star Trek" series for the Mac is $59.95; call 510-540-5535.)

For those moved to dabble as screen-saving artists themselves, a second publisher of the genre, Icom Simulations, offers a programmable package with a module that allows you to build your own sight-and-sound compositions, constructing them from a selection of customizable starter images and sound effects. (The Intermission series for Windows is $49.95; call 800-877-4266.)

-- Robert A. Mamis