In 1929 John McPherson graduated from Princeton with Highest Honors in Egineeering. A few months later Thomas J. Watson, Sr. [a neighbour and first CEO of IBM] invited him to join IBM – the company Watson had created five years earlier.
In 1930 McPherson wrote a letter to Endicott about a new way of doing multiplication on the 305 punch-card accounting machine, and in 1940 he became Manager in charge of all future methods in the accounting work on IBM machines. He became Director of Engineering in 1943, and Vice-President of Engineering in 1950. His influence ensured that IBM moved from mechanical to electronic computer machines.
For a glimpse of the early days see the description of The Selective Sequence Electronic Calculator (SSEC), a computer with 13,000 vacuum tubes and 23,000 relays, 8 high-speed registers. using Binary Coded Decimal [BCD]: A Large Scale General-Purpose Electronic Digital Calculator – The SSEC, John McPherson, Frank E. Hamilton, and Robert R. Seeber, Internal IBM document, 1948? Published in Annals of History of Science, 1982, Vol.4 pp. 313-326.
During his last ten years with IBM, John McPherson was head of IBM's Systems Research Institute (SRI). He retired in 1972, when IBM adopted a sixty-year-old limit for its officers. From the early days of APL in the 1960s John McPherson was an enthusiastic promoter of APL. His support ensured that APL became an IBM product. He was a dedicated APL user, and his many contributions were recognised when he was presented with the 1997 Kenneth E. Iverson Award for his Outstanding Contribution to the Development and Application of APL.