An article in Washington Business April 19 about Planning Research Corp. said incorrectly that the company's real estate computer listing service had losses in the second quarter of 1981. That operation had declining profits.

Planning Research Corp. DESCRIPTION: A diversified professional services company, the largest in the world, in such areas as computer science, information management consulting, planning, economics, engineering and architecture (NYSE). FOUNDED: 1954 in Los Angeles; moved to D.C. in 1977. TOP EXECUTIVE: John M. Toups, chairman.

Planning Research Corp., which has left the District's high-priced K Street neighborhood for the woods of McLean, seems to be rebounding from a difficult year last year.

A reorganization of the computer services, engineering and consulting company continues, and the company seems, after sharp 1981 losses, to have weathered successfully the shutdown of some European operations and the departure of its board chairman, Robert Sarnoff, the one-time RCA magnate. Sarnoff left that job and his position on the board last year. John M. Toups, previously the company's president and chief executive, was elected chairman on Jan. 20.

Sales are up 3 percent for the first half of PRC's fiscal year, which ends June 30. Led by its Government Information Systems division, which is active in developing computer operations for national defense programs, the only major growth area in the federal budget, the company reported a first-half profit of $3.6 million, compared with profits for the same period last year of $217,000.

But the sagging housing market is hurting the company's vital construction-related businesses, including its real estate computer listing service. That part of the business lost money during the second quarter.

Flow General Inc. DESCRIPTION: Diversified scientific firm engaged in research, analysis and manufacturing of biomedical and biological products (AMEX). FOUNDED: 1961. TOP EXECUTIVE: Thomas C. Basemore, chairman and chief executive officer.

Flow General, in a recent presentation to securities analysts in Boston, said the company's strategy is to become the leader in the biotechnology industry as a supplier of products and services and as a participant in research and development. Flow General's biomedical division is the largest and fastest growing of the firm's two divisions, generating 51 percent of the company's revenues last year, the company said.

Last month Flow General acquired for $60 million Worthington Diagnostics to complement its business in diagnostic testing and monitoring diseases. Worthington is a leader in supplying reagents, chemicals used to detect the presence of disease and monitor medical treatments.

The company said despite steady growth in the past, this year its earnings will be "somewhat diluted" because of the acquisition of Worthington. The company said its growth will be ahead of the average in the industry and in the general economy.

Last year the company had record performance and two successful common stock offerings. Shareholder investment in the firm grew to about $88 million compared with $30 million the year before.

Other acquisitions last year were of Amstelstad B.V. of the Netherlands for $1 million and Gelman Instrument S.p.A. Milan for $14.4 million to play major roles in distribution of biomedical products in Europe. It also acquired Adaptronics Inc. of McLean for $2.5 million because of its work in technology that's used in Flow General's biomedical and applied sciences divisions.

Atlantic Research Corp. DESCRIPTION: Alexandria-based developer of small rockets and gas generators, using solid propellants. ARC also is engaged in data communications, electromagnetic field measurement and analysis, microchemistry, printing and aerospace related fields (OTC). FOUNDED: 1949. TOP EXECUTIVES: Coleman Raphael, chairman; William H. Borten, president.

The biggest maker of little rockets, Atlantic Research is one of many Washington high-technology firms that are benefitting from the Reagan administration's defense buildup. As a result of diversification drives, almost half its $93 million annual sales comes from other operations, primarily data communications gear and electronic systems engineering. Sales in 1981 were up almost 17 percent, and profits jumped from $3.7 million to $5.2 million.

Atlantic Research opened a new 200-person engineering facility at its Gainesville plant last year and closed down its mobil systems division, which built special-purpose vehicles. This year the company will complete a $2 million pilot plant near Fredericksburg to produce samples of the company's latest invention, called ARC-Coal, a coal and water mixture that can be burned like fuel oil.

BDM International Inc. DESCRIPTION: Diversified professional services firm, based in Mclean, which specializes in national defense, security, defense communications, energy, transportation and environmental issues (OTC). FOUNDED: 1959, in El Paso, Tex., moved here in 1973. TOP EXECUTIVE: Earle C. Williams, president and chief executive.

BDM, whose net income last year rose 15 percent on a modest increase in revenues, this year moved from the over-the-counter market to the American Stock Exchange.

The firm, which specializes in national defense, security and defense communications, has said it is well-positioned to benefit from the federal government's focus on more services in those areas. In addition, the company has said it has a strong international market position.

The company's goals have been dollar profits, sound growth and diversification and contribution to important programs in the public and private sectors.

More than 80 percent of the company's operations have been contracts performed in connection with the Defense Department. Most of the remaining business has been performed for other government agencies.

The company has been heavily involved in laser technology and it is working to obtain a substantial portion of that market, particularly where the government is concerned. In 1980, 3 percent of BDM's business was laser-related and it had planned to increase that portion to between 4 percent and 6 percent by the beginning of this year.

Other projects are development of solar power as an alternative energy source, building advanced defense communications systems, and research on Soviet, NATO and Warsaw Pact nonnuclear forces.

Solon Automated Services Inc. DESCRIPTION: The nation's leading supplier of laundry equipment for multifamily housing and a major producer and supplier of commercial clothes dryers for use in multifamily housing, laundromats and other commercial facilities. Solon also owns and operates Sugarbush Valley, a ski resort in the Green Mountain National Forest in Vermont (OTC). FOUNDED: 1940. TOP EXECUTIVES: S. Solon Cohen, chairman; M. Roy Cohen, president and chief executive officer.

Severe winter weather adversely affected some businesses, but Solon reported its 1981-82 ski season at Sugarbush Valley was the best since the resort's acquistion in 1977. Solon's earnings for the past year would be a record except for the affects of high interest expenses during a year of record capital spending for the firm. Solon said it has been making concerted efforts to maximize profits in its existing laundry locations and to enlarge its marketing staff.

Scope Inc. DESCRIPTION: A diversified electronics and technology company based in Reston, with subsidiaries in Florida, California and Maryland (OTC). FOUNDED: 1957. TOP EXECUTIVES: William C. Schaub, chairman and chief executive officer.

Last year was a disappointing year to the management of Scope. While sales increased 13 percent over the previous year, the company recorded a loss of $1.8 million. The company attributed the sales increase to the acquisition of W. C. Dillon & Co. in January 1981.

However, Scope's other product lines were victims of sluggish conditions in capital equipment markets all year and accounting procedures made profits poor, the company said.

During the year Scope won a contract from the U.S. Postal Service for a large quantity of postage-computing window scales, "providing initial entry into the sizable post office window scale market," the company said.

Last December the company announced plans for a major restructuring of the company, spinning off two of its largest subsidiaries, National Controls and Repco. If the plan is approved by stockholders, each Scope stockholder will receive shares of National Controls and Repco equivalent to his Scope shares.

"It is the view of your board of directors that the proposed plan will enhance the ability of each of the corporations to finance its working capital requirements and provide the opportunity to better motivate employes of the respective corporations. . .," the company said in its annual report.

American Management Systems Inc. DESCRIPTION: Arlington-based developer, installer and operator of computer software systems used in the management and administration of business and governmental organizations. It installs systems for operations on customers' computers, provides operational services using its own computers and also provides management consultant services. The company offers prepackaged off-the-shelf software systems for such functions as payroll, utility billing and tax collection. FOUNDED: 1970. TOP EXECUTIVES: Ivan Selin, chairman; Charles Rosotti, president.

After several years of steady growth, which included contracts to computerize the accounting systems of New York City and the District of Columbia governments, AMS is entering a period of retrenchment.

In 1981, the company reported losses of $749,000 (46 cents a share) on sales of $65.6 million. The year before, the company earned $1.40 per share on sales of $58.5 million. The negative figure for 1981 became inevitable when AMS reported in October that it had lost $81,000 in the first nine months of the year.

At the time, Rosotti said he expected "some improvement" in the fourth quarter, but the results for the year indicate that AMS has still not found the formula to turn itself around.

Partly because the overall condition of the economy reduced the demand for computer services and computer consulting, and partly because AMS by its own admission expanded too fast and undertook too many new ventures at once, every segment of its business lagged in performance last year.

One consequence was an erosion of the market value of AMS stock, traded over the counter. From a high in 1980 of $41, the stock dropped to $14 a share and has hovered between $14 and $15 for the past few months.

AMS has scrapped its unprofitable software package designed for wholesale distributors and is concentrating on systems for local governments and commercial financial companies.

Syscon Corp. DESCRIPTION: D.C.-based corporation engaged principally in providing systems engineering, computer systems, technical services and software products for the U.S. government, primarily the military, and for state and municipal governments and commercial enterprises (OTC). FOUNDED: 1966. TOP EXECUTIVE: Jose J. Yglesias, president and treasurer.

Syscon made a mighty leap into the Top 100 companies, going public in mid-November with an initial offering of 500,000 common shares. Syscon, with 1,300 employes and nationwide operations, paid initial dividends of 25 cents a share. The firm had posted 15 years of increased sales and earnings before its public offering, and is banking on continued growth of the computer systems and software industry to sustain that performance. As an outgrowth of its computer business, Syscon recently began to develop and market microprocessor-based products.

Hazleton Laboratories Corp. DESCRIPTION: A Vienna life-sciences firm that manufactures products and provides services for institutions dealing with processes or diseases that affect humans and their environment. FOUNDED: 1969. TOP EXECUTIVES: Kirby L. Cramer, chairman; Donald P. Neilsen, president.

Hazleton is the biggest biological testing laboratory in the world, as well as a major breeder of research animals and producer of animal care laboratory equipment. For the 10th year in a row Hazleton reported record earnings and revenues. Revenues rose from $43.2 million to $44.6 million, while profits rose from $2 million to nearly $3.2 million. Earnings per share rose to $1.05 from 83 cents. The company spent $8.9 million--of the $17.7 million it raised during a stock offering in late 1980--to expand testing facilities. The main expenditure was for a facility to test rodents. In October the company sold its unprofitable subsidiary, Environmental Sciences.

Hazleton officials said they had expected the Environmental Protection Agency to have published more guidelines for testing toxic substances under the Toxic Substances Control Act. As a result, Hazleton said, its domestic biological testing laboratories were running at a lower level than the company expected at the start of the year. The company has $19 million in cash, most of it invested in high-yielding securities. In 1981, Hazleton had $2.1 million in interest income, compared with $1.1 million the year before.

Penril Corp. DESCRIPTION: Rockville-based firm that produces data communications equipment, electric test and measurement instruments and high fidelity speakers. FOUNDED: 1968. TOP EXECUTIVE: Kenneth M. Miller, president and chief executive officer.

Despite a drop in first and second quarter net income, Penril is expected to finish the year favorably next July 31, according to Drexel Burnham Lambert. However, the Wall Street firm said, "given the uncertainties present in the economy, we stress that further severe deterioration in the economy could soften Penril's order picture and necessitate a reduction in our earnings estimate. We are confident of the ability of company management to deal with adverse economic conditions and believe that fiscal 1982 will be another successful one for Penril."

Penril is a solid participant in the "rapidly growing data communications market," the analysts said, and it has sound expansion potential in its specialty electronics segments consisting of test instruments and power supplies.

The company is able to generate above-average rates of growth in sales and earnings during the next three to five years, Burnham Lambert continued. It also has a rate of return on shareholders' equity normally exceeding 20 percent.

Company officials have said they plan to continue the company's policy of growth through internal development as well as acquisitions. In March 1981, the firm completed its eighth acquisition for cash of an independent manufacturer of modems, which was the company's eighth acquisition in eight years. In addition, the company bought three divisions, one subsidiary and three product lines. The firm is looking for business candidates with annual revenues between $10 million and $50 million with product lines that will complement existing ones.

C-3 Inc. DESCRIPTION: Systems integrator of mini- and micro-computers, primarily for the U.S. government (OTC). FOUNDED: 1968. TOP EXECUTIVE: John G. Ballenger, president, chief executive officer and treasurer.

C-3 Inc. reports that the "strong financial performance" it achieved during the sixth-month period ended Sept. 30, 1981 is continuing because of a sustained demand for its products and services. During 1981, the company was awarded a $35 million contract with the U.S. Navy, a $55 million contract with the U.S. Coast Guard and a $3.2 million contract with the U.S. Air Force. Anticipated future revenue from existing contracts is $124.6 million, as compared with $51.6 million one year ago. The company recently completed construction on a 18,000-square-foot addition to its existing facilities in Reston. C-3 sees an "excellent" outlook for local data processing firms associated with the government here.

Advanced Technology DESCRIPTION: A McLean-based professional services firm with its principal business base serving the Navy Department. FOUNDED: 1976. TOP EXECUTIVE: Robert E. LaRose, president and chief executive officer.

When its fith year ended last May, Advanced Technology "operated for the first time in the status of a large business," the company's chief executive officer said in the annual report. At that time, revenues had increased 66 percent, and its staff had grown nationwide to 672. One company goal is $100 million in revenues in three years. In February 1981, Advanced Technology broke ground for its Cascades Center on 15 acres in Reston, which eventually will house 1,500 employes in three buildings and will become corporate headquarters in June 1983.

Although Advanced Technology had its principal business base working for the Navy, it has since expanded throughout other Defense Department branches and nonmilitary areas such as the departments of Education, Housing and Urban Development, Energy and Transportation and publicly owned utilities.

STSC Inc. DESCRIPTION: STSC provides financial management services and remote access computer services and software products based on the APL computer program language. The Bethesda company's products and services are marketed by and supported through 25 offices in the United States and Europe. Its central computers are accessed through a telecommunications network in more than 300 cities worldwide (OTC). FOUNDED: 1969. TOP EXECUTIVES: Daniel Dyer, president and chairman of the board; Robert C. Fick, senior vice president of finance and treasurer.

STSC revenues in fiscal year 1981 increased 31 percent, as compared with a 27 percent increase in fiscal year 1980. The company attributes this year's increase to growth in APL-based remote computing services. The firm's subsidiaries in Germany and Spain have been closed because of continuing losses since their formation in 1978. STSC says that because it is feeling the effects of the present economic situation, growth is not expected to continue this year at the same rate as in the past