• Ken Thompson

    For other people named Ken Thompson, see Ken Thompson (disambiguation) .

    Kenneth Lane Thompson (born February 4, 1943) is an American pioneer of computer science. Thompson worked at Bell Labs for most of his career where he designed and implemented the original Unix operating system. He also invented the

    B programming language , the direct predecessor to the C programming language , and was one of the creators and early developers of the Plan 9 operating system. Since 2006, Thompson has worked at Google , where he co-invented the Go programming language.

    Other notable contributions included his work on regular expressions and early computer text editors QED and

    ed, the definition of the UTF-8 encoding, and his work on computer chess that included the creation of

    endgame tablebases and the chess machine Belle .

    Early life and education

    Thompson was born in New Orleans . When asked how he learned to program, Thompson stated, "I was always fascinated with logic and even in grade school I'd work on arithmetic problems in binary, stuff like that. Just because I was fascinated." [2]

    DEC PDP-7 , as used for initial work on Unix

    Thompson received a Bachelor of Science in 1965 and a Master's degree in 1966, both in Electrical Engineering and Computer Science , from the

    University of California, Berkeley, where his master's thesis advisor was Elwyn Berlekamp . [3]

    Career and research

    Thompson was hired by Bell Labs in 1966. [4] In the 1960s at Bell Labs, Thompson and Dennis Ritchie worked on the Multics operating system. While writing Multics, Thompson created the

    Bon programming language. [5] He also created a video game called Space Travel. Later, Bell Labs withdrew from the MULTICS project.[6] In order to go on playing the game, Thompson found an old PDP-7 machine and rewrote

    Space Travel on it.[7] Eventually, the tools developed by Thompson became the Unix operating system : Working on a PDP-7 , a team of Bell Labs researchers led by Thompson and Ritchie, and including Rudd Canaday , developed a hierarchical file system , the concepts of computer processes and device files , a command-line interpreter , pipes for easy inter-process communication, and some small utility programs. In 1970, Brian Kernighan suggested the name "Unix", in a pun on the name "Multics". [8] After initial work on Unix, Thompson decided that Unix needed a system programming language and created B , a precursor to Ritchie's C. [9]

    In the 1960s, Thompson also began work on regular expressions. Thompson had developed the CTSS version of the editor QED , which included regular expressions for searching text. QED and Thompson's later editor ed (the standard text editor on Unix) contributed greatly to the eventual popularity of regular expressions, and regular expressions became pervasive in Unix text processing programs. Almost all programs that work with regular expressions today use some variant of Thompson's notation. He also invented

    Thompson's construction algorithm used for converting regular expression into nondeterministic finite automaton in order to make expression matching faster. [10]


    Thompson (sitting) and Ritchie working together at a PDP-11

    Version 6 Unix running on the

    SIMH PDP-11 simulator, with "/usr/ken" still present

    Throughout the 1970s, Thompson and Ritchie collaborated on the Unix operating system; they were so influential on Research Unix that Doug McIlroy later wrote, "The names of Ritchie and Thompson may safely be assumed to be attached to almost everything not otherwise attributed."[11] In a 2011 interview, Thompson stated that the first versions of Unix were written by him, and that Ritchie began to advocate for the system and helped to develop it: [12]

    Feedback from Thompson's Unix development was also instrumental in the development of the C programming language. Thompson would later say that the C language "grew up with one of the rewritings of the system and, as such, it became perfect for writing systems ".[12]

    In 1975, Thompson took a sabbatical from Bell Labs and went to his alma mater, UC Berkeley. There, he helped to install Version 6 Unix on a PDP-11/70 . Unix at Berkeley would later become maintained as its own system, known as the Berkeley Software Distribution (BSD). [13]

    Ken Thompson wrote a chess-playing program called "chess" for the first version of Unix (1971). [14] Later, along with Joseph Condon , Thompson created the hardware-assisted program

    Belle , a world champion chess computer . [15] He also wrote programs for generating the complete enumeration of chess endings, known as endgame tablebases , for all 4, 5, and 6-piece endings, allowing chess-playing computer programs to make "perfect" moves once a position stored in them is reached. Later, with the help of chess endgame expert John Roycroft, Thompson distributed his first results on CD-ROM . In 2001, the ICGA Journal devoted almost an entire issue to Ken Thompson's various contributions to computer chess. [14]


    Plan 9 from Bell Labs, running the acme text editor, and the rc shell

    Throughout the 1980s, Thompson and Ritchie continued revising Research Unix, which adopted a BSD codebase for the 8th, 9th, and 10th editions. In the mid-1980s, work began at Bell Labs on a new operating system as a replacement for Unix. Thompson was instrumental in the design and implementation of the Plan 9 from Bell Labs, a new operating system utilizing principles of Unix, but applying them more broadly to all major system facilities. Some programs that were part of later versions of Research Unix, such as mk and rc , were also incorporated into Plan 9.

    Thompson tested early versions of the

    C++ programming language for Bjarne Stroustrup by writing programs in it, but later refused to work in C++ due to frequent incompatibilities between versions. In a 2009 interview, Thompson expressed a negative view of C++, stating, "It does a lot of things half well and it's just a garbage heap of ideas that are mutually exclusive." [16]


    In 1992, Thompson developed the

    UTF-8 encoding scheme together with

    Rob Pike. [17] UTF-8 encoding has since become the dominant character encoding for the World Wide Web , accounting for more than 90% of all web pages in 2019. [18]

    In the 1990s, work began on the

    Inferno operating system, another research operating system that was based around a portable virtual machine . Thompson and Ritchie continued their collaboration with Inferno, along with other researchers at Bell Labs.[19]


    In late 2000, Thompson retired from Bell Labs. He worked at Entrisphere, Inc. as a fellow until 2006 and now works at Google as a Distinguished Engineer. Recent work has included the co-design of the Go programming language. Referring to himself along with the other original authors of Go, he states: [12]

    According to a 2009 interview, Thompson now uses a Linux -based operating system. [20]


    National Academies

    In 1980, Thompson was elected to the

    National Academy of Engineering for "designing UNIX, an operating system whose efficiency, breadth, power, and style have guided a generation's exploitation of minicomputers". [21] In 1985 he was elected a Member of the National Academy of Sciences (NAS). [1]

    Turing Award

    In 1983, Thompson and Ritchie jointly received the Turing Award "for their development of generic operating systems theory and specifically for the implementation of the UNIX operating system". His acceptance speech, "Reflections on Trusting Trust", presented the backdoor attack now known as the Thompson hack or trusting trust attack, and is widely considered a seminal computer security work in its own right.[22]

    IEEE Richard W. Hamming Medal

    In 1990, both Thompson and Dennis Ritchie received the IEEE Richard W. Hamming Medal from the Institute of Electrical and Electronics Engineers (IEEE), "for the origination of the UNIX operating system and the C programming language". [23]

    Fellow of the Computer History Museum

    In 1997, both Thompson and Ritchie were inducted as Fellows of the

    Computer History Museum for "the co-creation of the UNIX operating system, and for development of the C programming language". [24]

    National Medal of Technology

    On April 27, 1999, Thompson and Ritchie jointly received the 1998

    National Medal of Technology from President Bill Clinton for co-inventing the UNIX operating system and the C programming language which together have "led to enormous advances in computer hardware, software, and networking systems and stimulated growth of an entire industry, thereby enhancing American leadership in the Information Age". [25]

    Tsutomu Kanai Award

    In 1999, the Institute of Electrical and Electronics Engineers chose Thompson to receive the first Tsutomu Kanai Award "for his role in creating the UNIX operating system, which for decades has been a key platform for distributed systems work". [26]

    Japan Prize

    In 2011, Thompson, along with Dennis Ritchie , was awarded the Japan Prize for Information and Communications for the pioneering work in the development of the Unix operating system. [27]

    Personal life

    Ken Thompson is married and has a son. [28][14]


    1. ^ a b "Kenneth Thompson" .

    www.nasonline.org . Retrieved

    June 9, 2019.

    2. ^ Seibel 2009 , p. 450.

    3. ^ "Thesis Students" . Elwyn Berlekamp's Home Page . University of California, Berkeley Department of Mathematics.

    4. ^ "Ken Thompson: developed UNIX at Bell Labs" . Retrieved

    October 31, 2016.

    5. ^ Ritchie, Dennis. "The Development of the C Language" . Bell Labs. Retrieved

    October 31, 2016.

    6. ^ J. Stanley Warford (2009).

    Computer Systems . Jones & Bartlett Publishers. p. 460.

    ISBN 978-1-4496-6043-7 .

    7. ^ Ritchie, Dennis M. (2001).

    "Space Travel: Exploring the solar system and the PDP-7" . Bell Labs. Archived from the original on December 26, 2015. Retrieved

    February 4, 2016.

    8. ^ Ritchie, Dennis M. "The Evolution of the Unix Time-sharing System" . Retrieved

    October 31, 2016.

    9. ^ Dennis M. Ritchie. "The Development of the C Language" . Bell Labs/Lucent Technologies. Retrieved October 31, 2016.

    10. ^ Cox, Russ. "Regular Expression Matching Can Be Simple And Fast" . Retrieved October 30, 2016.

    11. ^ McIlroy, M. D. (1987). A Research Unix reader: annotated excerpts from the Programmer's Manual, 1971–1986 (PDF) (Technical report). CSTR. Bell Labs. 139.

    12. ^ a b c "Dr. Dobb's: Interview with Ken Thompson" . May 18, 2011. Retrieved November 10, 2014.

    13. ^ Salus, Peter H. (2005). "Chapter 7. BSD and the CSRG" . The Daemon, the Gnu and the Penguin .

    Groklaw .

    14. ^ a b c Dennis Ritchie (June 2001). "Ken, Unix and Games" .

    ICGA Journal . 24 (2). Retrieved

    March 5, 2020.

    15. ^ "Joe Condon (obituary)". Physics Today. 2013. doi : 10.1063/PT.4.1752 .

    16. ^ Seibel 2009 , p. 475.

    17. ^ Pike, Rob (April 30, 2003).

    "UTF-8 history" .

    18. ^ "Usage Statistics and Market Share of UTF-8 for Websites, June 2019" . w3techs.com . Retrieved

    June 9, 2019.

    19. ^ Khamlichi, M.el. "Ken Thompson UNIX systems father" . Unixmen. Retrieved October 31, 2016.

    20. ^ Seibel 2009 , p. 479.

    21. ^ "Dr. Ken Thompson" . National Academy of Engineering.

    22. ^ Thompson, Ken (1984).

    "Reflections on trusting trust" .

    Communications of the ACM . 27 (8): 761–763.

    doi :10.1145/358198.358210 .

    23. ^ "IEEE Richard W. Hamming Medal Recipients" (PDF). IEEE . Archived from the original (PDF) on July 26, 2011. Retrieved May 29, 2011.

    24. ^ "Ken Thompson" . Computer History Museum. Retrieved

    October 29, 2016.

    25. ^ "Bell Labs Luminaries Dennis Ritchie And Ken Thompson To Receive National Medal Of Technology" . ScienceDaily. December 8, 1998.

    26. ^ "Ken Thompson Receives Kanai Award for Impact of UNIX System" . Bell Labs. March 25, 1999. Archived from the original on March 26, 2013.

    27. ^ Evangelista, Benny (January 25, 2011). "Ken Thompson, Dennis Ritchie win Japan Prize" . The San Francisco Chronicle .

    28. ^ "Ken Thompson: A Brief Introduction" . The Linux Information Project . August 24, 2007. Retrieved March 5, 2020.


    Seibel, Peter (2009). Coders at Work – Reflections on the Craft of Programming (online ). New York:

    Apress . ISBN 978-1-4302-1948-4 (pbk.) ISBN 978-1-4302-1949-1 (electronic)

    External links

    Wikimedia Commons has media related to Ken Thompson.

    Wikiquote has quotations related to:

    Ken Thompson

    Ken Thompson , Bell Labs

    Reflections on Trusting Trust 1983

    Turing Award Lecture

    Unix and Beyond: An Interview with Ken Thompson IEEE Computer Society

    Ken Thompson: A Brief Introduction The Linux Information Project (LINFO)

    Computer Chess Comes of Age:

    Photos Computer History Museum

    Computer Chess Comes of Age:

    Video of Interview with Ken Thompson Computer History Museum

    Reading Chess paper by HS Baird and Ken Thompson on optical character recognition

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