THE annual Spring Comdex computer show in Atlanta earlier this month meant a booming business for the Bulletstop, an indoor firing range in suburban Marietta where customers can rent firearms and bullets to shoot anything they please, as long as it is already dead and fits through the doors. The Bulletstop gave Comdex visitors a chance to vent their frustrations by venting PC's, printers, hard disks, monitors and manuals with lead.

Paul LaVista, the owner, said about 10 groups of high-tech types came in during the Comdex show. ''I'm not a computer whiz, but one group brought in what looked like a hard disk and blasted it,'' he said. ''Another bunch brought in some kind of technical manual. The thing was enormous, about 2,000 pages. They rented three machine guns - an Uzi, an M3 grease gun and a Thompson -and when they were done it looked like confetti.''

''It must have been quite a show,'' Mr. LaVista said of Comdex. ''Doctors and computer types usually have a lot of pent-up anxiety, but these folks were dragging when they came in. When they left they were really up. The range looked like a computer service center after a tornado.''

Mr. LaVista said PC's were popular targets year-round. ''People are frustrated with them,'' he said. A year ago seven or eight men carried in a giant old Hewlett-Packard printer. ''I ran an extension cord to it, and just as it started to whirr and spit out paper, they blasted it,'' he said.

Comdex oddities: One small company was exhibiting an I.B.M. PC compatible that had been repackaged to look like a Macintosh, presumably for those who need a PC but want people to think they are using a Mac. Another company offered a PC with a socket for either an 80286 or an 80386 chip, for those who can't make up their minds on which processor to buy. Yet another company was offering a laptop with 3-inch floppy disk drives. Three-inch drives may be the standard in some regions of Bulgaria, but they are decidedly nonstandard on this continent.

One of the next big technological hurdles for laptops will be color display screens. Hitachi was showing a prototype 6-inch flat-panel liquid crystal display that offered remarkably bright images with 16 colors on screen. The screen was attached to an 80286-based Hitachi laptop that is not sold in this country. Hitachi is expected to begin aggressive marketing of its conventional laptops in this country next year.

Hitachi makes pocket-sized color television sets, and putting a color screen on a portable computer would seem an easy next step. It is not. A color screen big and bright enough for practical laptop use would need an extraordinarily powerful and efficient battery system, technology that apparently does not exist yet in commercial form. A Hitachi spokesman said it would take at least a year to develop.

However, NEC, another Japanese electronics giant, is also reported to be preparing to sell a color screen for its portables by next year. One thing is certain: color will add several hundred dollars, at least, to the price of the laptops.

Steady progress in miniaturization has allowed computers to shrink from the room-sized behemoths of the 1960's to desktop and even laptop models. How far can the trend be pushed? Some technicians at Comdex said there was virtually no limit to the miniaturization process for electronic components, and that the constraints were now in keyboards, power supplies and disk drives. One computer maker, asked to speculate on how far the trend might go, predicted that within a couple of years inch-thick PC's might even come with Velcro strips to allow them to be attached to the side of a desk.

Such machines would probably use high-density magnetic cards, about the size of two credit cards pasted together, to store up to 15 megabytes of information, more than 10 times the amount that can be stored on high density floppy disks today.

A couple of companies at Comdex were touting hand-held PC's and hand-held scanners, although such devices appeal to specialized markets.

A countertrend is to take PC's off the desk and put them on the floor. I.B.M. started it with the tower configuration for its PS/2 Models 60 and 80, and at least a dozen companies were showing floor-standing PC's at Comdex. Freed from the need to fit on a desk, some of the tower models are actually getting bigger to accommodate large disk drives, a variety of floppy drives and backup devices, and room for up to a dozen slots for plug-in boards.

Furniture manufacturers at the show said that as a general rule demand was rising for big office desks to accommodate big computers, big monitors, big telephones and the latest status symbols, the personal fax and photocopying machines.

Next week we'll leave the PC world behind and see what's new with Macintosh.

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