|Donald Watts Davies|
7 June 1924|
|Died||28 May 2000(aged 75)|
|Institutions||National Physical Laboratory|
|Alma mater||Imperial College|
|Known for||Packet switching|
Donald Watts Davies, CBE, FRS (7 June 1924 – 28 May 2000) was a Welsh computer scientist who was one of the inventors of packet switched computer networking, originator of the term, and the Internet itself can be traced directly back to his work.
Career history 
Davies was born in Treorchy in the Rhondda Valley, Wales. His father, a clerk at a coalmine, died a few months later, and his mother took Donald and his twin sister back to her home town of Portsmouth, where he went to school.
He received a BSc degree in physics (1943) at Imperial College London, and then joined the war effort working as an assistant to Klaus Fuchs on the nuclear weapons Tube Alloys project at Birmingham University. He then returned to Imperial taking a first class degree in mathematics (1947); he was also awarded the Lubbock memorial Prize as the outstanding mathematician of his year.
In 1955, he married Diane Burton; they had a daughter and two sons.
From 1947, he worked at the National Physical Laboratory (NPL) where Alan Turing was designing the Automatic Computing Engine (ACE) computer. It is said that Davies spotted mistakes in Turing's seminal 1936 paper On Computable Numbers, much to Turing's annoyance. These were perhaps some of the first "programming" errors in existence, even if they were for a theoretical computer, the universal Turing machine. The ACE project was overambitious and foundered, leading to Turing's departure. Davies took the project over and concentrated on delivering the less ambitious Pilot ACE computer, which first worked in May 1950. A commercial spin-off, DEUCE was manufactured by English Electric Computers and became one of the best-selling machines of the 1950s.
Davies then worked for a while on applications such as traffic simulation and machine translation. In the early 1960s, he worked on Government technology initiatives designed to stimulate the British computer industry.
In 1966 he returned to the NPL at Teddington just outside London, where he headed and transformed its computing activity. He became interested in data communications following a visit to the Massachusetts Institute of Technology, where he saw that a significant problem with the new time-sharing computer systems was the cost of keeping a phone connection open for each user. He first presented his ideas on packet switching at a conference in Edinburgh on 5 August 1968.
In 1970, Davies helped build a packet switched network called the Mark I to serve the NPL in the UK. It was replaced with the Mark II in 1973, and remained in operation until 1986, influencing other research in the UK and Europe. Larry Roberts of the Advanced Research Projects Agency in the United States became aware of the idea, and built it into the ARPANET, which evolved into the Internet.
Davies relinquished his management responsibilities in 1979 to return to research. He became particularly interested in computer network security. He retired from the NPL in 1984, becoming a security consultant to the banking industry.
Davies was appointed a Distinguished Fellow of the British Computer Society in 1975, a CBE in 1983 and a Fellow of the Royal Society in 1987. In 2012, Davies was inducted into the Internet Hall of Fame by the Internet Society.
- With D. Barber: Communication Networks for Computers, Wiley, 1973.
- With W. Price, D. Barber, C. Solomonides: Computer Networks and Their Protocols, Wiley, 1979.
- With W. Price: Security for Computer Networks, Wiley, 1984.
Davies was survived by his wife Diane, a daughter and two sons.
See also 
- Needham, R. M. (2002). "Donald Watts Davies, C.B.E. 7 June 1924 - 28 May 2000". Biographical Memoirs of Fellows of the Royal Society 48: 87–10. doi:10.1098/rsbm.2002.0006.
- "Donald Watts Davies". Internet Guide. 2010.
- "Pioneer: Donald Davies", Internet Hall of Fame
- The History of Computing Project - Donald Davies Biography
- Martin Cambell-Kelly. Pioneer Profiles: Donald Davies. Computer Resurrection, 44, Autumn 2008. ISSN 0958-7403
- Obituary, The Guardian, 2 June 2000
- Luke Collins, "Network pioneer remembered", Engineering & Technology, IET, 6 September 2008
- Packet Switching
- 2012 Inductees, Internet Hall of Fame website. Last accessed April 24, 2012
- "Obituary: Data Pioneer Donald Davies Dies", Internet Society (ISOC), 31 May 2000
- Oral history interview with Donald W. Davies, Charles Babbage Institute, University of Minnesota. Davies describes computer projects at the U.K. National Physical Laboratory, from the 1947 design work of Alan Turing to the development of the two ACE computers. Davies discusses a much larger, second ACE, and the decision to contract with English Electric Company to build the DEUCE—possibly the first commercially produced computer in Great Britain.
- Biography from the History of Computing Project
- Donald Davies profile page at NPL
- UK National Physical Laboratory (NPL) & Donald Davies from Living Internet
- Computer Networks: The Heralds of Resource Sharing, documentary ca. 1972 about the ARPANET. Includes footage of Donald W. Davies (at 19m20s).