Kenneth E. Iverson

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Kenneth E. Iverson, 1989

Kenneth Eugene "Ken" Iverson (born December 17, 1920 in Camrose , Alberta , † October 19, 2004 in Toronto , Ontario ) was a Canadian mathematician and computer scientist who developed the APL and J programming languages .


Iverson grew up on a farm in rural Alberta. Four months after his fifth birthday, he started school with a room and a teacher. He skipped several grades and, when he was twelve, moved to ninth grade at a nearby village school, which he dropped out during tenth grade to work on the farm. He also took a course in electrical engineering. In 1942 he was drafted into the Royal Canadian Air Force . During the Second World War he took eight correspondence courses of the Royal Canadian Legion and was convinced by his comrades to study. After his release in 1946 he went to the Queen's University in Kingston , Ontario, and made 1950 his bachelor's degree in mathematics and physics, and at Harvard University in Cambridge , Massachusetts , finally, in 1951 the Master in Applied Mathematics and in 1954 with Howard H. Aiken the Ph. D. in applied physics. From 1955 to 1960 he taught at Harvard University as an assistant professor applied mathematics, where he set up the first master’s course in computer science ( Automatic Data Processing ) with Aiken, Fred Brooks and others .

He then moved to the research department of IBM , where he worked until 1980. From 1980 he worked for the time-sharing service provider IP Sharp Associates in Toronto, before retiring in 1987, which he continued to do intensive research and development.


While at Harvard University, Kenneth E. Iverson developed his own notation for handling arrays , which he successfully used in teaching. He was also able to use them on his six-month sabbatical in 1957 at McKinsey & Company . At IBM Research , he expanded the notation to a formal language and published it in 1962 in the book A Programming Language , which was published by John Wiley . The language developed by him, named after the book title APL , was first used for the formal description of the IBM System / 360 computer family , which from 1964 onwards contributed significantly to the great success of IBM. In 1965 the first APL interpreter for batch processing was ready, making APL an executable programming language. The interactive system APL \ 360 followed in 1966, which became the starting point for all other APL interpreters. Various IBM computers were also available with keyboards specially adapted to APL. Kenneth E. Iverson, together with Adin Falkoff, played a key role in the development of these systems. Among other things, he co-founded the IBM Philadelphia Scientific Center for the further development of APL. He later designed several programming languages ​​that represent further developments and improvements to APL, including the J language together with Roger Hui from 1990 .

The floor and ceiling brackets are also from him, i.e. H. the notation for the floor and ceiling functions . In addition, the mapping of a predicate to a single-digit binary number, which is often used in theoretical computer science, in order to obtain closed formulas for more complex problems (see predicate mapping ).


In 1979, Kenneth E. Iverson received the ACM's Turing Award for the development of APL and for his contributions to the implementation of interactive systems . In 1982 he received the Pioneer Award of the IEEE and in 1991 the National Medal of Technology of the USA. He was a member of the US National Academy of Engineering . In 1970 he was made an IBM Fellow .


  • A Programming Language. Wiley, New York City, 1962.
  • with Frederick P. Brooks : Automatic Data Processing. Wiley, New York City, 1963.

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