Born in Stuttgart, Germany, she was the daughter of Dr. Caesar Hirsch, an ear, nose and throat doctor, and Felicia Hearst.
Family members said that her father heard that Adolf Hitler and his government planned to blacklist him because he was a Jew.
"To avoid arrest, Dr. Hirsch sent his children to Switzerland in the company of their grandmother," said Ms. Kessler's son, John J. "Jack" Condliffe of Timonium. "Dr. Hirsch completed a scheduled surgery that same day, and he and his wife followed across the Swiss border by car. The family traveled separately to avoid the appearance that they were fleeing the country. The Nazi state, still in its infancy, had not yet established full control of its citizenry."
Mr. Condliffe said his mother sailed to New York City in 1934 with her parents and siblings. The family later moved to Seattle. Her father encountered problems finding work.
"He was nearly penniless and deeply depressed. He committed suicide," Mr. Condliffe said.
Ms. Kessler graduated from high school at age 15 and later earned a bachelor's degree in mathematics from the University of California at Berkeley. She married Peter G. Condliffe, a biochemist and fellow Berkeley student. The couple divorced in 1980.
She and her husband moved to Maryland and settled in Kensington. She enrolled at the University of Maryland, College Park and earned a master's degree in mathematics.
In the 1960s she became involved in the civil rights movement and helped desegregate restaurants in Prince George's County during events sponsored by the National Association for the Advancement of Colored People. She accompanied African-American diners who were routinely denied service after they took a seat at a counter or table.
"When they really wanted to have lunch, they would go to Howard Johnson, which had voluntarily desegregated its restaurants," Mr. Condliffe said.
He said his mother joined the National Bureau of Standards and the National Institutes of Health at the time when the government was just beginning to buy its first IBM computers for nonmilitary use. In 1968, she became a senior analyst at the World Bank and wrote computer programs that modeled the economies of developing nations.
"My mom would write these complicated programs, which would require creating hundreds and thousands of computer punch cards," said her son. "When I wasn't in school, I would often go into work with her and happily type her punch cards for her on a special machine. You couldn't make one mistake. The computer had less power than my laptop and filled an enormous room bigger than a house."
In 1980 she retired and married Albert M. Kessler, an importer. She kept busy in her field and wrote four self-help computer books geared toward novice programmers.
She also moved to Baltimore's Homeland neighborhood, where she enjoyed gardening.
She also worked alongside her brother to recover her father's medical library, which was being held at the Tubingen University library in Germany. The books contained her father's bookplate.
"A newspaper editor discovered the books were sold for a nominal fee to the library after my grandfather's home and property was seized by the Gestapo," her son said.
Ms. Kessler and her brother later donated the books to the medical library of the University of California at Los Angeles.
Ms. Kessler, a quilter, belonged to the Baltimore Heritage Quilters Guild. Her son said her quilts mixed scenes of her childhood with images of Baltimore.
"One of her award-winning quilts features Baltimore rowhouses, emphasizing their marble steps," he said. "Her skill with fabric was incredible."
Ms. Kessler became a Baltimore Museum of Art volunteer. She used her extensive knowledge of fabric and sewing to assist in cataloging the lesser-known but large lace collection of Claribel and Etta Cone, the well-known painting collectors. A member of the Society for Early Music of Northern Maryland, she enjoyed playing the recorder.
A memorial reception will be held Aug. 18 at her Canton home.
In addition to her son, survivors include another son, Donald P. Condliffe of Frederick; a daughter, Katherine M. Condliffe of Greenbelt; her brother, Peter Hearst of Oxnard, Calif.; eight grandchildren; and a great-granddaughter. Her second husband died in 1988.