1960 to 1969: The Rise of Business Computers and Business Software - The Technical and Social History of Software Engineering - page 109

IBM System/360
The IBM 1400 series emerged in 1960 and had a good run for about 10 years.
However, in April 1964, IBM announced the larger and more powerful IBM Sys-
tem/360 (S/360), which became the main computer of U.S. industry after battling
with other vendors for supremacy.
The hardware architect for the S/360 was Gene Amdahl (who later founded
a competitive computer company). The software was managed by Fred Brooks,
whose experiences were immortalized in one of the most famous computer topics
ever written, The Mythical Man-Month . Thomas J. Watson, Jr., was the IBM chair-
man and the driving force behind the S/360. John Opel handled the marketing
launch. John would later become President, CEO, and Chairman of IBM, and he
was a visionary in his own right.
Note
John Opel served on a board of directors with Mary Maxwell
Gates, who was a successful businesswoman and the mother of Bill
Gates. John Opel and Mary Gates were both on the board of direct-
ors of the charitable organization United Way. It was the connec-
tion between John and Mary that led to John Opel being interested
in Microsoft as a company that might be able to build the operating
system for the IBM personal computer in a future decade.
The architecture of the IBM S/360 had features that were unusual at the time,
but it proved to be the key to the long-range success of both IBM and the S/360
computer system.
One novel feature was that the S/360 was not designed as a single computer
but as a family of related computers that started fairly small and fairly cheap but
could be expanded in power and capacity as the need arose. This meant that com-
panies could start with low-end versions such as the IBM System/360 model 20
or 30 and then move up to larger and faster versions. All of the bigger S/360 units
were backward-compatible with the smaller units, so they could run the same ap-
plications without any changes.
The original series of IBM System/360 computers included models 20, 30, 40,
50, 60, 62, and 70. The low-end models up through 30 were designed to replace
the IBM 1401 series, and they included emulators that allowed IBM 1401 soft-
ware to operate without reprogramming. Models 65 and 75 were added to the high