Ken Thompson

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Ken Thompson (left) with Dennis Ritchie

Kenneth "Ken" Lane Thompson (born February 4, 1943 in New Orleans , Louisiana ) is an American computer scientist who, among other things, played a key role in the development of the Unix operating system. He has received numerous honors and awards for his work, including the Turing Award .


Thompson graduated from the University of California at Berkeley , California with a degree in electrical engineering . In 1969 he and his colleague Dennis Ritchie implemented the first version of the Unix operating system in assembly language at Bell Labs . As an anecdote it is often said that the real motivation behind the development of Unix was to port the game Space Travel to a little-used PDP-7 , since one hour of computing time on normal mainframes cost 75 US dollars.

Among other things, Thompson wrote the first shell for Unix , retronym Thompson-Shell "sh", and the line editor ed . He developed the programming language B , a predecessor of the C language , which is still one of the most widely used programming languages ​​worldwide. Later he and Rob Pike , also at Bell Labs, developed the Plan 9 operating system .

With the advice of John Roycroft , he developed programs for the complete analysis of endgames in chess . He made the results of this work available to others on four endgame CDs at cost price. They were later also evicted. With endgame databases , a chess program can perfectly play an endgame (currently with at most seven pieces on the board) by accessing the necessary information in the data collection. In winning positions, it finds (depending on the objective) the direct path to mate or to conversion to another endgame that has been won (by converting or capturing a piece); in losing positions it can delay the loss of the game as much as possible.

Together with Dennis Ritchie he received the Turing Award in 1983 and the Richard W. Hamming Medal of the Institute of Electrical and Electronics Engineers (IEEE) in 1990 . In 1985 Thompson was elected to the National Academy of Sciences and in 1991 to the American Academy of Arts and Sciences . In 1999 Bill Clinton presented him and Dennis Ritchie with the National Medal of Technology for the development of Unix and C, and in 2011 they were awarded the Japan Prize , also for their Unix commitment. In 2019, both were inducted into the National Inventors Hall of Fame .

In his Turing Award speech, Thompson described how he developed a special type of backdoor . It was a compiler that, when compiling a Unix login program, built in a back door unnoticed. If the prepared compiler is successfully installed on a system, the backdoor code sequence can be removed from the compiler's source code. If the compiler itself is compiled on this system, it recognizes this and inserts the malicious code again. In this way there is no trace of the manipulation in the source code of the compiler, but it will still be retained in the machine code in later versions of the compiler.

Thompson developed in the late 1970s and early 1980s together with his colleague Joe Condon (1935-2012) the chess calculator Belle , which in 1980 won the World Computer Chess Championship (WCCC) . In 1992, together with Rob Pike, he developed UTF-8 , a widely used system for encoding Unicode characters.

Thompson left Bell Labs on December 1, 2000. He was then a partner at Entrisphere, Inc. until 2006 and now works as a respected developer at Google, where he developed the Go programming language together with Rob Pike and Robert Griesemer .


In 2019 it became known that Thompson was p/q2-q4!using the password 39 years ago . It is in the descriptive notation, which is no longer so common , for the queen's pawn opening d2 – d4 .


  • Peter Seibel: Coders at Work: Important programmers and their success stories . mitp, 2011, ISBN 978-3-8266-9103-4 , Chapter 12: Ken Thompson , p. 407-435 (English: Coders at Work: Reflections on the Craft of Programming . 2009. Translated by Reinhard Engel).

Web links

Commons : Ken Thompson  - collection of images, videos and audio files

Individual evidence

  1. ^ Matthias Kremp: 40 years of Unix . Mirror online. August 18, 2009. Retrieved October 25, 2011.
  2. The famous PDP-7 comes to the rescue ( English ) Bell Labs . Archived from the original on August 6, 2007. Retrieved October 26, 2011: "It did not take long, therefore, for Thompson to find a little-used PDP-7 computer with an excellent display terminal," Ritchie explained. "He and I rewrote 'Space Travel' to run on this machine."
  3. Japan Prize for UNIX Developers . heise online . January 25, 2011. Retrieved September 4, 2011.
  4. ^ Reflections on Trusting Trust. Retrieved June 25, 2019 .
  5. ^ Rob Pike: UTF-8 history . April 30, 2003. Retrieved May 24, 2012.
  6. Sylvester Tremmel: UNIX celebrities chose chess opening: 39 year old BSD passwords cracked. In: heise .de, October 12, 2019, accessed on October 14, 2019.
  7. Unix father Ken Thompson's ancient password cracked. In:, October 11, 2019, accessed on October 14, 2019.