Mr. Llewellyn co-founded Estimation in 1973, introducing a computerized estimating system. Under his direction, the company became a major supplier of computerized systems tailored to the contracting trades.

He retired in 1993 when his son, G. Michael Llewellyn, took over as president. However, he remained active in the company as chairman and contributed to the construction industry by writing trade journal articles, participating in association activities, and speaking at conferences.

Contributions in Mr. Llewellyn’s memory may be made to the Johns Hopkins University Oncology Center, 555 N. Broadway, Suite 801, Baltimore, MD 21205.