Claude Shannon

Claude Elwood Shannon (April 30, 1916 – February 24, 2001) was an American polymath who worked as a mathematician, electrical engineer, computer scientist, cryptographer, and inventor. He is widely called the "father of information theory" and is credited with laying the groundwork for the Information Age. The roboticist Rodney Brooks said Shannon was the 20th-century engineer who contributed most to 21st-century technologies, and mathematician Solomon W. Golomb ranked his intellectual achievement among the greatest of the 1900s.

Shannon earned two bachelor's degrees from the University of Michigan in 1936—one in electrical engineering and one in mathematics. The next year, he completed a master's thesis at MIT titled "A Symbolic Analysis of Relay and Switching Circuits." In it, he showed that electrical applications of Boolean algebra could build any logical numerical relationship, establishing the theory behind digital computing and digital circuits. Some have called this the most important master's thesis ever written; it is often described as the "birth certificate of the digital revolution." This work launched a career that earned him a Kyoto Prize in 1985. He received his PhD in mathematics from MIT in 1940; his dissertation focused on genetics and contained important results, though it remained unpublished and little-known until recently.

During World War II, Shannon contributed to cryptanalysis for U.S. national defense, doing fundamental work on codebreaking and secure telecommunications. He wrote a paper considered one of the foundational pieces of modern cryptography; his work has been called a turning point that marked the end of classical cryptography and the start of modern cryptography. It laid the foundation for symmetric-key cryptography, influencing the work of Horst Feistel, the Data Encryption Standard (DES), and the Advanced Encryption Standard (AES). For this, Shannon is known as the "founding father of modern cryptography."

His 1948 paper "A Mathematical Theory of Communication" founded the field of information theory. Electrical engineer Robert G. Gallager called it a "blueprint for the digital era," and Scientific American labeled it "the Magna Carta of the Information Age." Golomb compared Shannon's impact on the digital age to that of the inventor of the alphabet on literature. Shannon is also regarded as the most important contributor to information theory after 1948. His theory enabled advances across many scientific fields, including the invention of the compact disc, the development of the Internet, the commercialization of mobile telephony, and the understanding of black holes. He formally introduced the term "bit," co-invented pulse-code modulation and the first wearable computer, and invented the signal-flow graph.

In 1951, Shannon joined the Central Intelligence Agency's Special Cryptologic Advisory Group. From 1956 to 1978, he was a professor at MIT. He made numerous contributions to artificial intelligence, including co-organizing the 1956 Dartmouth workshop—considered the founding event of the field—and writing papers on chess computer programming. His Theseus machine was the first electrical device to learn by trial and error, making it one of the earliest examples of artificial intelligence.

Shannon grew up in Gaylord, Michigan, born in a hospital in nearby Petoskey. His father, Claude Sr. (1862–1934), was a businessman and briefly a probate judge in Gaylord. His mother, Mabel Wolf Shannon (1880–1945), was a language teacher and principal of Gaylord High School. Claude Sr. descended from New Jersey settlers; Mabel was the child of German immigrants. The family was active in their Methodist Church during his youth. Shannon spent most of his first 16 years in Gaylord, attending public school and graduating from Gaylord High School in 1932. He showed an early interest in mechanical and electrical subjects, excelling in science and math. At home, he built model planes, a radio-controlled boat, and a barbed-wire telegraph system to a friend's house half a mile away. He also worked as a messenger for Western Union. His childhood hero was Thomas Edison, whom he later learned was a distant cousin—both were descendants of John Ogden (1609–1682), a colonial leader and ancestor of many notable people.

In 1932, Shannon entered the University of Michigan, where he first encountered the work of George Boole. After graduating in 1936, he began graduate studies in electrical engineering at MIT, working on Vannevar Bush's differential analyzer—an early analog computer made of electromechanical parts that solved differential equations. While studying the analyzer's complicated ad hoc circuits, Shannon designed switching circuits based on Boole's concepts. In 1937, he wrote his master's thesis, "A Symbolic Analysis of Relay and Switching Circuits," with a related paper published in 1938. This revolutionary work diagrammed switching circuits that could implement Boolean algebra's essential operators. He then proved these circuits could simplify the arrangement of electromechanical relays then used in telephone call routing.