Had a very primitive form of an operating system, albeit in hardware. A separate hardware control unit existed to direct the sequence of computer operations.[22]
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^ abPrinted Series. University of Alabama Bureau of Business Research. 1954. p. 5.
^ abcdeRandell, B. (2012). The Origins of Digital Computers: Selected Papers. Springer Science & Business Media. pp. 239, 352. ISBN9783642961458. [...] IBM SSEC [...] was hardly a stored program computer [...] being basically a tape-controlled machine in the tradition of the Harvard Mark I or the Bell Laboratories Model V.
^Reilly, Edwin D.; Ralston, Anthony; Hemmendinger, David (2000). Encyclopedia of Computer Science. Second part of the text: search (with quotes) for "stored program electronic computers.". Nature Publishing Group. p. 136. ISBN9781561592487. The Model VI did have an ability to execute short sequences of arithmetic with single commands punched on the tape, a concept new at the time and one rediscovered and named later as "macro" commands. It interpreted these commands through ingenious electromagnetic circuits that, in effect, "microprogrammed" the machine. It is not historically misleading to use that term, since those features were seen and noticed by Maurice Wilkes (q.v.), who later developed that concept for stored program electronic computers.