Several errors occurred in last week's compilation of Washington's Top 100 companies. Assets of Potomac Electric Power Co. as of Dec. 31, 1982, totaled $2.7 million. Pepco ranks third in assets, behind C&P Telephone and Martin Marietta Corp. Assets of BDM Corp. as of Dec. 31, 1982, totaled $53.7 million, 35th among Washington nonfinancial companies. BDM now has 2,450 employes and about 85 percent of its business is defense-related. The firm's profits increased 46 percent last year; revenue was up 34 percent. Assets of Manor Care Inc. as of the end of its fiscal year on May 31, 1982, totaled $426.5 million, 14th in the area. Now traded on the New York Stock Exchange, the Silver Spring health care firm has 1,700 employes in the Washington area and 16,000 worldwide. It was incorrectly reported that Syscon Corp. was acquired by Continentel Telcom. Continental Telcom acquired STSC Corp. With sales of $71.4 million, Syscon ranks 33rd among Washington-area nonfinancial corporations. Evaluation Research Corp. was omitted from the listings; the firm ranks 54th in revenues at $17.3 million. Profiles of Syscon and Evaluation Research appear on this page. The Norfolk Southern Railroad was removed from the Washington companies list after the newly merged railroad said it was consolidating headquarters operations in Norfolk. With revenues of $3.3 billion, and assets of $6.8 billion, Norfolk Southern ranks second among Virginia corporations. Earnings last year totaled $411.4 million ($6.57 a share). PHH Group and Allegheny Beverage Corp. were not listed among the 10 largest Maryland corporations based outside the Washington area, though both are larger than Easco Corp., the smallest industrial firm listed. PHH of Hunt Valley, a vehicle management and cost control firm, earned $29.6 million ($1.93 a share) on revenues of $471.7 million. Allegheny Beverage, a Pepsi-Cola bottler and owner of The Macke Co. in Washington, earned $9.4 million ($2.30 a share) on revenues of $453.4 millio

IBM EMPLOYES: 10,000 DESCRIPTION: The computer giant has a manufacturing plant in Manassas, a huge federal systems division and other operations that add up to the largest local work force of any out-of-town company. Hecht's EMPLOYES: 8,572 DESCRIPTION: The Washington-Baltimore division of the May Department Stores Co. of St. Louis has 23 stores and two warehouses in the metro area. Safeway EMPLOYES: 6,784 DESCRIPTION: The Washington division of Safeway has approximately 130 stores and a Landover warehouse. Safeway stores outside the Washington area add several thousand additional jobs to the Maryland and Virginia economies. Vitro Laboratories EMPLOYES: 5,600 DESCRIPTION: A unit of the Electronics and Defense Group of the Penn Central Corp., Vitro is a high technology systems engineering company providing diversified professional and technical services in the fields of national defense, communications, information and energy systems. Most of its work force is in Montgomery County. AT&T EMPLOYES: 5,020 DESCRIPTION: Besides C&P Telephone--which will become a separate company next year--the Bell system has several other Washington operations. American Bell, the equipment subsidiary has 850 employes here; AT&T general departments, including the Washington regulatory and lobbying operations has 115; Western Electric Co., equipment manufacturing and service, 1,217; Long Lines, the long distance service, another 2,838. Sears EMPLOYES: 5,000 DESCRIPTION: With nine stores, two distribution centers, three services centers and its regional headquarters in Bethesda, Sears is already a major local employer. The Chicago-based company recently announced plans to set up the headquarters of its new world trading subsidiary in a renovated building on Pennsylvania Avenue. %&Mobil EMPLOYES: 4,900 DESCRIPTION: The oil firm recently moved its marketing headquarters to Fairfax County, bringing the staff at Mobil's complex there to 1,200 people. The company also owns Montgomery Ward, which employes 3,500 at its department stores in this area. Continental Telecom EMPLOYES: 3,309 DESCRIPTION: The Bell System's biggest rival in the telephone business is becoming as much a part of the Washington business community as AT&T. In addition to its own operations, Continental is a partner in two joint ventures--American Satellite Corp. of Rockville with Fairchild Industries and Space Communications Corp. with Fairchild and Western Union. Continental Telecom last year acquired Syscon Corp., a local $60-million-a-year computer software and services company that had gone public a year earlier. Control Data Corp. EMPLOYES: 3,100 DESCRIPTION: The Minneapolis computer company's operations in the Washington area include Arbitron, the TV rating service, Cybernet data processing, Control Data business forms, Control Data Institute and Control Data Learning Center. M/A Com DCC EMPLOYES: 2,000 DESCRIPTION: The Massachusetts manufacturer of electronic gear has a major plant in the I-270 corridor of upper Montgomery County.