Putting a computer on every desk may be a boon for productivity, but wherever there's a computer, there's an open door for software viruses and information thieves.

Within a few years, the door may be closed for good; in effect the personal computer (PC) revolution may be reined in. At a growing number of large companies, employees are being assigned to personal computers that have no disks on which to store information. Because there is no slot for a diskette, files can't be stolen through that PC, and virus-contaminated disks have to find another point of entry.

Diskless PCs are connected in networks to more powerful PCs, called file servers, that can handle the data storage needs of the entire network.

"It's like having a file cabinet in the hallway or main part of the building, not there at your desk," said International Business Machines Corp. spokesman Dean Kline.

Carl Trimble, a systems engineer for Computer Systems in Tamarac, Fla., said, "Diskless workstations are big in security-conscious environments like governments and large corporations that want to keep employees from downloading copy or programs off the network.

"If they're not security-conscious, they'd might as well get the hard drives so people can load and unload data," he said. "It depends on the application."

Diskless PCs have been available for several years from vendors such as 3Com and Hyundai and through hardware dealers who add their own software. According to International Data Corp., a research firm in Framingham, Mass., only 75,090 diskless PCs were sold in the United States in 1989. With Compaq Computer Corp. and IBM joining the market in 1990, analysts believe a million units will be sold each year by the mid-'90s.

As PCs became more powerful and independent in the work place, software selection fell to the dictate of users, creating chaos for data processing managers, said Ron Cooke, an analyst at Dataquest Inc. in San Jose, Calif. The evolution of PC networks, however, gave software control back to management.

"End users need to have the ability to share data, but managers need to control what kind of software is used on the network so they can give adequate support," Cooke said.

Public demand for diskless PCs has grown more sluggishly than analysts first expected, but new products from Compaq and wider distribution of IBM products suggest that might be changing.

In May, Compaq introduced a diskless PC in two versions, one containing an Intel Corp. 80386 microprocessor, the other an 80286 chip. Each machine comes with 1 megabyte of memory. Each costs $900 less than machines equipped with a 40-megabyte hard drive and a diskette drive.

IBM is expected to come out with a new diskless 80386-based PC sometime this fall. PC Week, an industry journal, quoted sources saying the new IBM model would be priced in the $2,000 range. Compaq's most powerful diskless machine has a $2,299 price tag. IBM would not say whether such a PC is on the way.

"There is apparently a tremendous amount of interest. We've been asking what our customers needs are, and a diskless workstation is one of the things they want," said Kline of IBM. "Rather than having a machine that is independently intelligent, it's one that draws its power from the network."

IBM has been selling diskless PCs since mid-1989, but only on a special-order basis to large customers.

Wyse Technology of San Jose entered the diskless PC market in November 1988 by adding an 80286-based processor to a dumb terminal. In addition to offering all of the aspects of being disk-free, the Wyse machine occupies less than one square foot of desk-top space -- smaller than most other models on the market.