Donald Shell

After acquiring a B.S. from Michigan Technological University, he went into the Army Corps of Engineers, and from there to the Philippines to help repair damages during World War II. When he returned after the war, he married Alice McCullough and returned to Michigan Technological University, where he taught mathematics. After, he moved to Cincinnati, Ohio, and worked for General Electric's engines division, where he developed a convergence algorithm and wrote a program to perform performance cycle calculations for GE's first aircraft jet engines. He also went to the University of Cincinnati, where in 1951 he acquired a M.S. in mathematics and, in 1959, acquired his Ph.D. in Mathematics. In July of that year he published the shell sort algorithm[1] and "The Share 709 System: A Cooperative Effort". In 1958, he and A. Spitzbart had published "A Chebycheff Fitting Criterion".

Although he is most widely known for his shell sort algorithm, his Ph.D. is also considered by some to be the first major investigation of the convergence of infinite exponentials, with some very deep results of the convergence into the complex plane. This area has grown considerably and research related to it is now investigated in what is more commonly called tetration. In October 1962 he wrote "On the Convergence of Infinite Exponentials" in the Proceedings of the American Mathematical Society.

After acquiring his Ph.D., Shell moved to Schenectady, New York, to become Manager of Engineering for General Electric's new Information Services Department, the first commercial enterprise to link computers together using the client–server architecture. This architecture is the fundamental design for the Internet. He worked with John George Kemeny and Thomas Eugene Kurtz to commercialize the Dartmouth Time-Sharing System in 1963.

In 1971 Shell wrote "Optimizing the Polyphase Sort" in the Communications of the ACM, and in 1972 he joined with a close friend and colleague, Mr. Ralph Mosher (who designed the walking truck), to start a business called Robotics Inc. where he was the General Manager and chief software engineer. Four years later, in 1976, they sold the company and Shell returned to General Electric Information Services Corporation.

In 1984 he retired and moved to North Carolina.[2]

Donald Shell married Alice McCullough after returning from World War II. They had two sons, Allyn and Peter.

Allyn Shell followed in his father's footsteps and became a computer scientist. He teaches Compiler Design with LLVM at John Hopkins where he teaches that Donald Shell taught him that "A pure function (having no side effects) can be replaced by an array." A truth that he has never seen in a text book and has not even seen as an optimization in LLVM. Peter Shell became a medical lab technologist in the US Army. Allyn's son, Matthew, is a record producer and sound engineer based in the DC area. Peter has two children and five grandchildren. Alice died of cancer after years of being cared for by Donald.

About a year after Alice's death Donald married Virginia Law whose husband had died in Africa. Virginia had three children from her first marriage, David, Paul and Margret. After being married to Donald about 30 years, Virginia died of congestive heart failure due to malaria acquired in Africa. Donald cared for Virginia for many years prior to her death.

A year after Virginia's death at age 81 Donald married Helen Whiting who had also had two previous spouses who had died, one of whom she cared for because he became invalid. Helen also brought a son Gene and two daughters, Dianne and Peggy, into the marriage. All of their sons and daughters are married with their own families.

Donald Shell died on 2 November 2015 in Asheville, North Carolina. He was survived by his wife Helen.

• Biographical sketch
• PhD History
• www.informatik.uni-trier.de/~ley/db/indices/a-tree/s/Shell:Donald_L=.html
• Tetration References
• Compiler Design with LLVM at JHU Engineering for Professionals
• Obituary