High-tech firms, drawn to the Washington area by the prospect of doing business with the federal government, will provide expanding employment opportunities for both professional and non-professional workers here, according to a new study.

"The area now has a critical mass of technology-oriented firms that will attract others," said the report, written by economist Gail Garfield Schwartz and released yesterday by the Greater Washington Research Center. "The great majority of the firms surveyed are currently expanding," with roughly 1,200 high-tech firms employing about 105,000 employes on a $4.2 billion payroll, the report said.

More than two-thirds of 21 major technology-oriented firms interviewed for the report said proximity to federal agencies was a major drawing card of the Washington area. They also reported that sales to the federal government accounted for more than half of their revenue.

The firms surveyed, including Fairchild Industries Inc. and Planning Research Corp., said the Defense Department was the biggest single federal agency in volume of purchases, and four of the firms said 90 to 100 percent of their sales were defense-related.

The firms are planning to "reduce their dependence on federal sales" and expand into commercial markets to buffer them against sharp cuts in government procurement, the report said.

Sales employment opportunities "may be significantly greater than currently expected, as firms try to tap the private-sector market and discover they need a sales force that is familiar with the technical aspects of their products and services," the report said.

Local high-tech firms engage in three types of activity, as defined by the report. Some concentrate on invention and innovation; some modify and apply existing technologies, while others focus on technology-related activities such as computer sales and service.

The future of area high-tech firms depends on government procurement practices, the successful expansion into new private-sector and foreign markets and expansion into manufacturing, the report said.

All firms surveyed are expecting to add employes, especially in the professional and managerial positions, the report said. "Professional employment is expected to grow substantially, but nonprofessional jobs employ 52 percent of all workers," according to the report. The most highly sought-after employe skills are the ability to communicate and reason analytically.

Fairfax and Montgomery counties have the lion's share of high-tech firms, the report said, while Prince George's County can "build on a base of major government facilities in the country," the report added. Yesterday, Maryland and Defense Department officials announced a major addition to those facilities, a computer research center near Bowie where DOD plans to develop the next generation of supercomputers.

Another report, released last week by the Washington Baltimore Regional Association, said the Washington area is rapidly becoming "the information capital of the world." Among the factors said to attract telecommunications firms to the area are "a specialized and highly trained labor pool, a well-integrated transportation system, proximity to national and international markets, and federal government regulators."