Joan H. Truby, 38, a computer program analyst who was active in school affairs in Columbia, Md., died of cancer Thursday at the Baltimore Cancer Research Center.

Mrs. Truby was born in Philadelphia. She earned bachelor's degrees in mathematics and art history at Pennsylvania State University and then returned to Philadelphia, where she was a program analyst in a bank.

Following her marriage in 1967 to James Truby, she worked for a bank in Pittsburgh. The couple moved to the Washington area the following year. Mrs. Truby was a program analyst for the May department store company until 1978. She then worked for a sporting goods store in Columbia, where she lived.

She was a founder of the Roslyn Rise Interfaith Day Care Center in Columbia and a member of its board of directors. For the past year, she had been a full-time volunteer in the library of the Bryant Woods Elementary School in Columbia and for this work she received the Howard County Outstanding Volunteer Service Award last week.

In addition to her husband, of Columbia, survivors include a daughter, Rose, also of Columbia; her father, William Banks Hawkins, of Santa Barbara, Calif., and a sister, Mimi Lucking, of Santa Paula, Calif.

The family suggests that expressions of sympathy be in the form of contributions to the Baltimore Cancer Research Center, Baltimore, Md.