Claude Elwood Shannon

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Claude Elwood Shannon (April 30, 1916February 24, 2001) has been called "the father of information theory", and was the founder of practical digital circuit design theory.

Biography

Shannon was born in Petoskey, Michigan and was a distant relative of Thomas Edison. While growing up, he worked as a messenger for Western Union.

In 1932, Shannon began studying at the University of Michigan, where he eventually encountered a course that introduced him to the works of George Boole. He graduated from the university in 1936 with two bachelor's degrees, one in electrical engineering and one in mathematics, and he then moved to the Massachusetts Institute of Technology for graduate school, where he worked on Vannevar Bush's differential analyzer, an analog computer.

In his 1937 MIT master's thesis, A Symbolic Analysis of Relay and Switching Circuits, Shannon proved that Boolean algebra and binary arithmetic could be used to simplify the arrangement of the electromechanical relays then used in telephone routing switches, then turned the concept upside down and also proved that it should be possible to use arrangements of relays to solve Boolean algebra problems. This concept, of utilizing the properties of electrical switches to do logic, is the basic concept that underlies all electronic digital computers, and the thesis became the foundation of practical digital circuit design when it became widely known among the electrical engineering community during and after World War II. Contemporaneous methods to design logic circuits at the time were ad hoc and lacked the theoretical rigor that Shannon's paper supplied to later projects.

Professor Howard Gardner, of Harvard University, called Shannon's thesis "possibly the most important, and also the most famous, master's thesis of the century". A version of the paper was published in the 1938 issue of the Transactions of the American Institute of Electrical Engineers, and in 1940, it earned Shannon the Alfred Noble American Institute of American Engineers Award.

Flush with this success, Vannevar Bush suggested that Shannon work on his dissertation at Cold Spring Harbor Laboratory, funded by the Carnegie Institution headed by Bush, to develop similar mathematical relationships for Mendelian genetics, which resulted in Shannon's 1940 PhD thesis at MIT, An Algebra for Theoretical Genetics. Shannon then joined Bell Labs to work on fire-control systems and cryptography during World War II. He returned to MIT to hold an endowed chair in 1956.

In 1948 Shannon published A Mathematical Theory of Communication in two parts in the July and October numbers of the Bell System Technical Journal. This work focuses on the problem of how to best encode the information a sender wants to transmit. In this fundamental work he used tools in probability theory, developed by Norbert Wiener, which were in their nascent stages of being applied to communication theory at that time. Shannon developed information entropy as a measure for the uncertainty in a message while essentially inventing what became known as the dominant form of "information theory." By introducing the concept of the thermodynamics of computation, Shannon became the first scientist to successfully address the conundrum of Maxwell's Demon. The book co-authored with Warren Weaver, The Mathematical Theory of Communication, reprints Shannon's 1948 article and Weaver's popularization of it, which is accessible to the non-specialist. Another notable paper published in 1949 is Communication Theory of Secrecy Systems, a major contribution to the development of a mathematical theory of cryptography. He is also credited with the introduction of the Sampling Theory, which is concerned with representing a continuous-time signal from a (uniform) discrete set of samples.

Outside of his academic pursuits, Shannon was interested in juggling, unicycling, and chess. He also invented many devices, including a chess-playing machine (rather described how one could operate in a paper published in 1950), a rocket-powered pogo stick, a wearable computer to predict the result of playing roulette [1], and a flame-throwing trumpet for a science exhibition. He met his wife Betty when she was a numerical analyst, i.e., a "computer," at Bell Labs.

From 1956 to 1978 he was a professor at MIT. To commemorate his achievements, there were celebrations of his work in 2001, and there are currently three copies of a statue of Shannon: one at the University of Michigan, one at MIT in the Laboratory for Information and Decision Systems and one at Bell Labs. After the breakup of the Bell system, the part of Bell Labs that remained with AT&T was named Shannon Labs in his honor.

Shannon's computer chess program

In 1950 Shannon published a groundbreaking paper on computer chess entitled Programming a Computer for Playing Chess. It describes how a machine or computer could be made to play a reasonable game of chess. His process for having the computer decide on which move to make is a minimax procedure, based on an evaluation function of a given chess position. Shannon gave a rough example of an evaluation function in which the value of the black position was subtracted from that of the white position. Material was counted according to the usual relative chess piece point value (1 point for a pawn, 3 points for a knight or bishop, 5 points for a rook, and 9 points for a queen). He considered some positional factors, subtracting ½ point for each doubled pawn, backward pawn, and isolated pawn. Another positional factor in the evaluation function was mobility, adding 0.1 point for each legal move available. Finally, he considered checkmate to be the capture of the king, and gave it the artificial value of 200 points. Quoting from the paper:

The coefficients .5 and .1 are merely the writer's rough estimate. Furthermore, there are many other terms that should be included. The formula is given only for illustrative purposes. Checkmate has been artificially included here by giving the king the large value 200 (anything greater than the maximum of all other terms would do).

The evaluation function is clearly for illustrative purposes, as Shannon stated. For example, according to the function, pawns that are doubled as well as isolated would have no value at all, which is clearly unrealistic.

The reason for assigning checkmate a value higher than the maximum sum of all other terms is so that the minimax procedure will value checkmate above all else and thus it will sacrifice as much material as it has to in order to prevent itself from being checkmated, or to checkmate the opponent. The value is arbitrary — any number larger than the sum of all of the other terms would cause the minimax procedure to give the same result. This figure has led to some misconceptions that a king actually has a value of 200 points as material.

Awards and honors

See also

References

  • C. E. Shannon: A mathematical theory of communication. Bell System Technical Journal, vol. 27, pp. 379–423 and 623–656, July and October, 1948.
  • Claude E. Shannon and Warren Weaver: The Mathematical Theory of Communication. The University of Illinois Press, Urbana, Illinois, 1949. ISBN 0252725484
  • Claude E. Shannon: Programming a Computer for Playing Chess, Philosophical Magazine, Ser.7, Vol. 41, No. 314, March 1950. (Available online under External links below)
  • David Levy: Computer Gamesmanship: Elements of Intelligent Game Design, Simon & Schuster, 1983. ISBN 0-671-49532-1

External links

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