[From "The Design of APL" by A. D. Falkoff and K. E. Iverson, IBM Journal of Research and Development, July, 1973.]  

Appendix. Chronology of APL development The development of APL was begun in 1957 as a necessary tool for writing clearly about various topics of interest in data processing. The early development is described in the preface of Iverson [10] and Brooks and Iverson [15]. Falkoff became interested in the work shortly after Iverson joined IBM in 1960, and used the language in his work on parallel search memories [16]. In early 1963 Falkoff began work on a formal description of System/360 in APL and was later joined in this work by Iverson and Sussenguth [2].

Throughout this early period the language was used by both Falkoff and Iverson in the teaching of various topics at various universities and at the IBM Systems Research Institute. Early in 1964 Iverson began using it in a course in elementary functions at the Fox Lane High School in Bedford, New York, and in 1966 published a text that grew out of this work [8]. John L. Lawrence (who, as editor of the IBM Systems Journal, procured and assisted in the publication of the formal description of System/360) became interested in the use of APL at high school and college level and invited the authors to consult with him in the development of curriculum material based on the use of computers. This work led to the preparation of curriculum material in a number of areas and to the publication of an APL\360 Reference Manual by Sandra Pakin [17].

Although our work through 1964 had been focused on the language as a tool for communication among people, we never doubted that the same characteristics which make the language good for this purpose would make it good for communication with a machine. In 1963 Herbert Hellerman implemented a portion of the language on an IBM/1620 as reported in [18]. Hellerman’s system was used by students in the high school course with encouraging results. This, together with our earlier work in education, heightened our interest in a full-scale implementation.

When the work on the formal description of System/360 was finished in 1964 we turned our attention to the problem of implementation. This work was brought to rapid fruition in 1965 when Lawrence M. Breed joined the project and, together with Philip S. Abrams, produced an implementation on the 7090 by the end of 1965. Influenced by Hellerman’s interest in time-sharing we had already developed an APL typing element for the IBM 1050 computer terminal. This was used in early 1966 when Breed adapted the 7090 system to an experimental time-sharing system developed under Andrew Kinslow, allowing us the first use of APL in the manner familiar today. By November 1966, the system had been reprogrammed for System/360 and APL service has been available within IBM since that date. The system became available outside IBM in 1968.

A paper by Falkoff and Iverson [3] provided the first published description of the APL\360 system, and a companion paper by Breed and Lathwell [19] treated the implementation. R. H. Lathwell joined the design group in 1966 and has since been concerned primarily with the implementations of APL and with the use of APL itself in the design process. In 1971 he published, together with Jorge Mezei, a formal definition of APL in APL [9].

The APL\360 System benefited from the contributions of many outside of the central design group. The preface to the User’s Manual [1] acknowledges many of these contributions.