C3 Inc., the Reston computer manufacturer, announced that William E. Gesell has joined the firm as vice president for finance and administration. Gesell was formerly operations controller for the Sperry Corp.'s federal projects division.

Mid-Atlantic Coca-Cola Bottling Co. Inc. has named Edward L. Wynns senior vice president for sales and marketing of the Silver Spring-based firm. He had been vice president in charge of the company's largest sales division.

Scott-Long Construction Inc. has appointed Gary M. Concelmo cost coordinator and Bill Blatz director of field services for the firm's Northern Virginia construction projects. Concelmo was formerly chief estimator and assistant to the president of L. F. Jennings Inc. in Falls Church, and Blatz was a partner in Blatz Construction.

Crown Central Petroleum Corp. in Baltimore has promoted Joseph P. Candella to general marketing manager from retail marketing manager.

Norwood Industrial Construction Co. Inc. in Columbia has named William C. Barton its Maryland regional manager. He is a former division manager with Harkins Builders.

McCormick & Co. Inc. has appointed Frederick G. Demers human relations supervisor for the Hunt Valley, Md., spice maker. Demers previously was human resources administrator for Maryland Casualty Co. in Baltimore.

Acadia Industries Inc. in White Marsh, Md., has promoted George W. Simmons to the new post of vice president and national remodeling sales manager for its window and door manufacturing subsidiary, Acadia Manufacturing Corp. Simmons has been an assistant vice president and sales manager of the firm's Norfolk plant.

Environmental Products Corp., a McLean manufacturer of beverage container recycling equipment, has named Gerald Downey director of advertising and promotion. He was formerly sales promotion manager for Needham, Harper & Steers Advertising Inc., and director of advertising for WRQX Radio in Washington.

OAO Corp. in Greenbelt has named Edwin S. Warrell manager of its Colorado Springs operations. Warrell, a retired colonel in the U.S. Air Force, previously was director of missile warning in the Air Force's NORAD/Space Command headquarters.