Kenneth E. Iverson

Kenneth Eugene Iverson (17 December 1920 – 19 October 2004) was a Canadian computer scientist noted for the development of the programming language APL.

Ken Iverson was born on 17 December 1920 near Camrose, a town in central Alberta, Canada.

His parents were farmers who came to Alberta from North Dakota; his ancestors came from Trondheim, Norway.

During World War II, he served first in the Canadian Army and then in the Royal Canadian Air Force.

He received a B.A. degree from Queen's University and the M.Sc.

and Ph.D. degrees from Harvard University.

In his career, he worked for Harvard, IBM, I. P. Sharp Associates, and Jsoftware Inc. (née Iverson Software Inc.).

Iverson began school on 1 April 1926 in a one-room school, initially in Grade 1, promoted to Grade 2 after 3 months and to Grade 4 by the end of June 1927.

He left school after Grade 9 because it was the depths of the Great Depression and there was work to do on the family farm, and because he thought further schooling only led to becoming a schoolteacher and he had no desire to become one.

At age 17, while still out of school, he enrolled in a correspondence course on radios with De Forest Training in Chicago, and learned calculus by self-study from a textbook.

During World War II, while serving in the Royal Canadian Air Force, he took correspondence courses toward a high school diploma.

After the war, Iverson enrolled in Queen's University in Kingston, Ontario, taking advantage of government support for ex-servicemen and under threat from an Air Force buddy who said he would "beat his brains out if he did not grasp the opportunity".

He graduated in 1950 as the top student with a Bachelor's degree in mathematics and physics.

Continuing his education at Harvard University, he began in the Department of Mathematics and received a Master's degree in 1951.

He then switched to the Department of Engineering and Applied Physics, working with Howard Aiken and Wassily Leontief.

"Kenneth Iverson has recalled graduate study under Aiken as 'like an apprenticeship' in which the student 'learned the tools of the scholarship trade'. Every topic was 'used more as a focus for the development of skills such as clarity of thought and expression than as an end in itself'. Once admitted to the program, a graduate student underwent a rite of 'adoption into the fold'. He was given a desk (or a share of a desk) among a group of other graduate students, the permanent staff, or visiting scholars, 'most of whom were engaged in some aspect of the design and building of computers'. A student was thus 'made to feel part of a scholarly enterprise' and was provided, 'often for the first time, with easy and intimate access to others more experienced in his chosen field'."

"When interviewing Aiken, I had asked him whether Tropp and I might see his lecture notes; Aiken replied that he had always destroyed his lecture notes at the end of each year, so that he would not be tempted to repeat his lectures."

Howard Aiken had developed the Harvard Mark I, one of the first large-scale digital computers, while Wassily Leontief was an economist who was developing the input–output model of economic analysis, work for which he would later receive the Nobel prize.

Leontief's model required large matrices and Iverson worked on programs that could evaluate these matrices on the Harvard Mark IV computer.

Iverson received a Ph.D. in applied mathematics in 1954 with a dissertation based on this work.

At Harvard, Iverson met Eoin Whitney, a 2-time Putnam Fellow and fellow graduate student from Alberta.

This had future ramifications.

Iverson stayed on at Harvard as an assistant professor to implement the world's first graduate program in "automatic data processing".

"Many people think that Aiken was interested only in scientific computers. This was simply not so. During one coffee hour, Aiken turned to Ken Iverson, who had just finished his Ph.D., and said: 'These machines are going to be immensely important for business, and I want you to prepare and teach a course in business data processing next fall.' There had never been such a course anywhere in the world. Ken was qualified only because he was a mathematician. I was so excited by the prospect that I immediately volunteered to be Ken's graduate teaching assistant."

It was in this period that Iverson developed notation for describing and analyzing various topics in data processing, for teaching classes, and for writing (with Brooks) Automatic Data Processing.

He was "appalled" to find that conventional mathematical notation failed to fill his needs, and began work on extensions to the notation that were more suitable.

In particular, he adopted the matrix algebra used in his thesis work, the systematic use of matrices and higher-dimensional arrays in tensor analysis, and operators in the sense of Heaviside in his treatment of Maxwell's equations, higher-order functions on function argument(s) with a function result.

The notation was also field-tested in the business world in 1957 during a 6-month sabbatical spent at McKinsey & Company.

The first published paper using the notation was The Description of Finite Sequential Processes, initially Report Number 23 to Bell Labs and later revised and presented at the Fourth London Symposium on Information Theory in August 1960.

Iverson stayed at Harvard for five years but failed to get tenure, because "[he hadn't] published anything but the one little book".

Iverson joined IBM Research in 1960 (and doubled his salary).

He was preceded to IBM by Fred Brooks, who advised him to "stick to whatever [he] really wanted to do, because management was so starved for ideas that anything not clearly crazy would find support."

In particular, he was allowed to finish and publish A Programming Language and (with Brooks) Automatic Data Processing, two books that described and used the notation developed at Harvard.

(Automatic Data Processing and A Programming Language began as one book "but the material grew in both magnitude and level until a separation proved wise". )

At IBM, Iverson soon met Adin Falkoff, and they worked together for the next twenty years.

Chapter 2 of A Programming Language used Iverson's notation to describe the IBM 7090 computer.

In early 1963 Falkoff, later joined by Iverson and Ed Sussenguth, proceeded to use the notation to produce a formal description of the IBM System/360 computer then under design.

The result was published in 1964 in a double issue of the IBM Systems Journal, thereafter known as the "grey book" or "grey manual".

He was honored with the Turing Award in 1979 "for his pioneering effort in programming languages and mathematical notation resulting in what the computing field now knows as APL; for his contributions to the implementation of interactive systems, to educational uses of APL, and to programming language theory and practice".

Iverson suffered a stroke while working at the computer on a new J lab on 16 October 2004, and died in Toronto on 19 October 2004 at age 83.