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Obituary build, and his sense of play is evident in many of his creations. In the 1950s, when (1916–2001) computers were given names like ENIAC (electronic numerical integrator and Look at a compact disc under a calculator), Shannon built a computer microscope and you will see music called THROBAC I (thrifty Roman- represented as a sequence of pits, or in numeral backward-looking computer), mathematical terms, as a sequence of 0s which was able to add, subtract, multiply and 1s, commonly referred to as bits. The and even divide numbers up to 85 working foundation of our Information Age is this only with Roman numerals. His study in transformation of speech, audio, images Winchester, Massachusetts, was filled with and video into digital content, and the such devices, including a maze-solving man who started the digital revolution mechanical mouse and a miraculous was Claude Shannon, who died on 24 juggling machine. Traversing the ceiling February, at the age of 84, after a long was a rotating chain, like those found at struggle with Alzheimer’s disease. dry cleaners, from which were suspended Shannon arrived at the revolutionary the gowns from a score of honorary idea of digital representation by sampling doctorates. They made a splendid sight a source of information at an appropriate flying around the room. rate, and converting the samples to a bit Shannon’s 1941 doctoral dissertation, stream. He characterized the source by a Inventor, mathematician on the mathematical theory of genetics, is single number, which he called entropy (a and leader of the digital not as well known as his master’s thesis, term adapted from statistical mechanics), revolution and in fact was not published until 1993, to quantify the information content of the by which time most of the results had been source. For a stream of text, Shannon obtained independently by others. After viewed entropy as a statistical parameter peace, and security in war, depend more graduating from MIT, Shannon spent a that measured how much information is on fruitful applications of information year at the Institute for Advanced Study, produced on average by each letter. He also theory than on physical demonstrations, and this is the period where he began to created , by introducing either in bombs or in power plants, that develop the theoretical framework that led redundancy into the digital representation Einstein’s famous equation works.” In fact, to his 1948 paper on communication in the to protect against corruption. If today you his work has become more important presence of noise. take a compact disc in one hand and a pair over time with the advent of deep space He joined Bell Labs in 1941, and of scissors in the other, then score the disc communication, wireless phones, high- remained there for 15 years, after which he along a radius from the centre to the speed data networks, the , and returned to MIT. During the Second World edge, you will find that the disc still plays products like compact-disc players, hard War, his work on encryption led to the as new. drives and modems that make essential use system used by Roosevelt and Churchill for Before Shannon, it was commonly of coding and data compression to transatlantic conferences, and inspired his believed that the only way of achieving improve reliability and speed. pioneering work on the mathematical arbitrarily small probability of error in Shannon grew up in Gaylord, theory of cryptography. a communication channel, such as a Michigan, and began his education at the It was at Bell Labs that Shannon telephone line, was to reduce the University of Michigan, where he majored produced the series of papers that transmission rate to zero. All this changed in both mathematics and electrical transformed the world, and that in 1948 with the publication of A engineering. As a graduate student at transformation continues today. In 1948, Mathematical Theory of Communication, Massachusetts Institute of Technology Shannon connected in which Shannon characterized a channel (MIT), his familiarity with both the with physics by developing a new by a single parameter, the channel capacity, mathematics of boolean algebra and the perspective on entropy. That connection is and showed that it was possible to transmit practice of circuit design produced what evolving today, as others explore the encoded information at any rate below science historian H. H. Goldstine called implications of quantum computing, by capacity with an arbitrarily small “one of the most important master’s theses enlarging information theory to treat the probability of error. His method of proof ever written… a landmark in that it transmission and processing of quantum was to show the existence of a single good changed circuit design from an art to a states. code for data transmission by averaging science”. This thesis, A Symbolic Analysis of Shannon must rank near the top of over all possible codes. The 1948 paper Relay and Switching Circuits, written in the list of major figures of twentieth established fundamental limits on the 1936, provided mathematical techniques century science, although his name is efficiency of communication through for building a network of switches and relatively unknown to the general noisy channels, but did not produce an relays to realize a specific logical function, public. His influence on everyday life, explicit example of a good code that would such as a combination lock — an electrical which is already tremendous, can only achieve the highest capacity. It has taken circuit that works if, and only if, the right increase with the passage of time. 50 years for coding theorists to discover combination of buttons is pressed. This Robert Calderbank and Neil J. A. Sloane families of codes that come close to these work won the Alfred Noble Prize of the Robert Calderbank and Neil J. A. Sloane are at fundamental limits for telephone lines. combined engineering societies of the USA the Information Sciences Research Lab, AT&T The importance of Shannon’s work was and is fundamental to the design of digital Shannon Research and Technology Center, recognized immediately. According to a computers and integrated circuits. Florham Park, New Jersey 07932-0971, USA. 1953 issue of Fortune, “It may be no Shannon’s interest in circuit design was e-mails: [email protected] exaggeration to say that man’s progress in not purely theoretical, for he also liked to [email protected]

768 NATURE | VOL 410 | 12 APRIL 2001 | www.nature.com

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