Donald Davies

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Donald Watts Davies
Born (1924-06-07)7 June 1924
Treorchy, Wales
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Nationality Welsh
Fields Computer science
Institutions National Physical Laboratory
Alma mater Imperial College
Known for Packet switching

Donald Watts Davies, CBE, FRS[1] (7 June 1924 – 28 May 2000) was a Welsh computer scientist who independently developed the concept of packet switching in computer networking,[2] after Paul Baran in the United States had completed his pioneering work.[3] The ARPANET project credited Davies primarily for his influence.[4][5]

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.[6]

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[6] on the nuclear weapons Tube Alloys project at Birmingham University.[7] 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.[8]

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 floundered, leading to Turing's departure.[7] 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.[7]

Davies also worked on applications of 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.[7] He first presented his ideas on packet switching at a conference in Edinburgh on 5 August 1968.[9]

In 1970, Davies coined the term packet switching for the concept of dividing computer messages into packets that are routed independently, and possibly via differing routes, across a network and are reassembled at the destination, a concept previously known under a cryptic term distributed adaptive message block switching by Paul Baran.[10][11] At NPL Davies helped build a packet-switched network (Mark I). It was replaced with the Mark II in 1973, and remained in operation until 1986, influencing other research in the UK and Europe.[12]

Larry Roberts of the Advanced Research Projects Agency in the United States utilized Davies' "packet switching" theory in the late 1960s, and built it into the ARPANET, a predecessor to the modern Internet.[7]

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.[7]

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.[13]


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Davies was survived by his wife Diane, a daughter and two sons.[14]


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  4. "Pioneer: Donald Davies", Internet Hall of Fame
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  6. 6.0 6.1 The History of Computing Project - Donald Davies Biography
  7. 7.0 7.1 7.2 7.3 7.4 7.5 Martin Cambell-Kelly. Pioneer Profiles: Donald Davies. Computer Resurrection, 44, Autumn 2008. ISSN 0958-7403
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  9. Luke Collins, "Network pioneer remembered", Engineering & Technology, IET, 6 September 2008
  10. Baran P. (April 1965) Distributed Adaptive Message Block Switching, Rand Corp. report No. P-3127.
  11. Packet Switching History
  12. Packet Switching
  13. 2012 Inductees, Internet Hall of Fame website. Last accessed April 24, 2012
  14. "Obituary: Data Pioneer Donald Davies Dies", Internet Society (ISOC), 31 May 2000

External links