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This article is about IBM's relationship with APL. For more complete information about IBM, see Wikipedia.

The International Business Machines Corporation (IBM) was the initial developer of APL, hosting Ken Iverson's development of Iverson notation since 1960 and creating implementations from APL\360 (1966) to APL2 (1984). Its notable employees include Adin Falkoff and Jim Brown whose contributions were made at IBM, as well as others such as Iverson, Eugene McDonnell, and Larry Breed who worked at IBM before moving elsewhere. While APL efforts were allowed substantial freedom as research projects, the language's insignificance relative to IBM's other business sometimes led to it being neglected. Development of APL2 slowed soon after its release, and IBM sold off rights to APL2 in 2021.

APL development

Iverson's notation saw its first use at IBM in hardware description, driven by Adin Falkoff (who had been hired in 1955) working with Ken Iverson and Ed Sussenguth. This was followed by a series of implementation efforts, first the relatively independent PAT first running in 1964, then the more APL-like IVSYS/7090 interpreter in 1965 and finally the highly successful APL\360 in 1966. The conflict with IBM's promotion of PL/I delayed APL\360's release as a product and it was used only within IBM and in a few academic installations initially. It was released in 1968, preceded by APL\1130, which had been made available earlier that year. In the explosion of time-sharing APLs that followed, IBM continued to direct language development with enhancements to APL\360 up to the release of APL.SV in 1973, although APL*PLUS offered more advanced system functionality. VS APL, released in 1976, added file-system interaction. APL.SV's primitive set became a widely used standard for flat APLs, and was not extended further. However, Jim Brown was tasked with designing a nested successor beginning in 1971. APL2, released in 1984 following a prototype Installed User Program (IUP) made public in 1982, was IBM's final APL design.

Watson Research Center

Initial APL work was carried out at the Thomas J. Watson Research Center in Yorktown Heights, New York. Adin Falkoff had worked there since 1955, and Ken Iverson joined (on the advice of former teaching assistant Fred Brooks) in 1960. The group hired Larry Breed in 1962 and Dick Lathwell in 1966. Breed and Lathwell collaborated with Stanford University students Phil Abrams and Roger Moore, who were never directly hired by IBM, in the implementation of IVSYS/7090 and APL\360 respectively. Jim Brown, who had learned about APL at another IBM job started in 1965 and then left for Syracuse University, worked at Watson Research beginning in 1969, at Yorktown over the summer and remotely from Syracuse while he worked on his Ph.D.[1]

Philadelphia Scientific Center

IBM's Philadelphia Scientific Center was founded by Adin Falkoff and others in 1969 and closed in 1974. Along with Falkoff, Ken Iverson and Dick Lathwell worked there the whole time, and the three became the APL Design Group when it was closed.[2] Other employees at the Philadelphia Scientific Center included Trenchard More, Jim Brown, and Joey Tuttle.


  1. Jim Brown. A Personal History of APL. Updated 2017-04-05.
  2. IPSA Newsletter December 1977 (pdf), p. 5.
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