According to Wikipedia, the first operating system was GM-NAA I/O, produced in 1956 by General Motors' Research division for its IBM 704.

According to Merriam-Webster and Etymonline, the term "operating system" was first used in 1961. (Neither includes a citation)

The Oxford English Dictionary has the actual 1961 citation: 1961 Ann. Rev. Automatic Programming 2 232 Two operating systems are provided in the Honeywell package.

So there's about a five year gap before the terminology emerged after the technology arrived. Then again the term may have only been used sporadically at first and only settled into place some years later?

In any case, which operating system was the first to be called an operating system at the time? I realize there may be a difference between people in the field using the term and companies producing and/or marketing them to use the term.

As a bonus question, what other terms were used for the early OSes before the terminology did settle? I would guess maybe monitor and kernel might be among them?

It seems my wording was not clear. I am looking for the first use of the term and to which operating system that first use referred. I am not looking for later texts on the subject of early operating systems which existed prior to the publication of that text.

(If anyone can help me word this clarification more clearly, please do. Stephen Kitt has understood my intention perfectly.)

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    It's my understanding that "supervisor" and "monitor" were both predecessors to "kernel", with "supervisor" living on in its relationship to the modern term "hypervisor".
    – ssokolow
    Jun 8 at 6:45
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    Called by whom? By its authors? By its users? By articles that were published decades later? Questions asking, "What was the first X?" are prone to a version of the no true Scotsman fallacy. You'll get different answers from people who have differing, narrow opinions about precisely what is or is not a true "X." Jun 8 at 10:57
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    The terminology did not settle in 1961 when "Operating System" was first used. Even in the mid 70's when I started, there was still a variety of terms commonly used: Kernel, Monitor, Executive, Operating Executive, etc. Some maintained that there were distinct meanings between these different terms, but really there was no sense of standard terminology or meaning until the late 70s / early 80s. Jun 8 at 13:33
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    Worth noting that telephone and railroad companies were using the term “operating system” in a different sense as far back as 1901. For example, this definition from 1912: “By operating system is meant an exchange system , or toll system composed of one or more toll or long distance telephone lines ” In different contexts, it could be a system in operation or a system that operated something else.
    – Davislor
    Jun 8 at 19:32
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    As @Davislor mentions, the term is way older than modern day digital computers. It was as well used in accounting for standardized accounting procedure material, describing how to do each task about bookkeeping according to the method chosen (there were competing companies selling such 'operating systems'). So most likely authors describing their monitor as 'OS' used it based on this prior meaning of stanardized generic handling
    – Raffzahn
    Jun 9 at 10:54

3 Answers 3


As is often the case, a candidate for the first system to be described by its authors as an “operating system” is the Atlas supervisor, described in the eponymous paper published in December 1961, with an entire section on “The Operating System”. This could arguably be understood as “a system of operation” (describing the overall use of the system), rather than what we understand as “an operating system” nowadays, but the presence of a section titled “Methods of Using the Operating System” suggests that the term is used in a fashion approaching what we think of now.

However, George F. Ryckman discusses “the SHARE Operating System” in his May 1960 paper, The computer operation language, which beats Atlas by over a year, and also constitutes the earliest citation I’m aware of using “operating system” in a way familiar to modern readers:

The development of computer operating systems have materially aided the problem of getting a program or series of programs on and off the computer efficiently.

The SHARE Operating System is the direct descendant of the GM-NAA I/O system you mention. Ryckman was in charge of the General Motors side of the venture.

By late 1961, “operating system” had been used to describe other systems, again in a fashion similar to the modern meaning; for example, in The CLIP Translator (January 1961),

First, the SASHT program was already available for operation with the SDC operating system.

and in The META Compiler (September 1961),

The META compiler was designed as a part of MITRE's M90 operating system and as a vehicle for research in programming languages.

The “Atlas supervisor” terminology answers your subsidiary question: “supervisor” was a common term for the central part of an operating system. “Monitor” was also used; in fact Ryckman describes GM-NAA I/O as “the first monitor or operating system” in his 1983 paper, The IBM 701 Computer at the General Motors Research Laboratories.

There are earlier citations of “operating system”, but they use the term to describe a system of operation; for example, Operating experience with the Los Alamos 701 (December 1953):

[…] I think it a good idea to give you a description of how the 701 is managed, including the kind of people who program and code for it, and the advantages they gain by the present operating system.

  • A footnote: according to the latest (Summer 2022) edition of Resurrection, the bulletin of the Computer Conservation Society, David Howarth - leader of the Atlas Supervisor work - recently died. I can find no obituary online, however. Jun 8 at 12:15
  • They sound more like kernels than OSs.
    – RonJohn
    Jun 8 at 14:22
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    @RonJohn as I understand the question, the point here isn’t to debate the definition of “operating system”, just to determine where the expression was first used in a somewhat familiar sense compared to its current use. In the Atlas case, the kernel would be the supervisor, and the whole supporting environment the operating system. And you’re right, they’re limited compared to current OSs, but the computers back then were far smaller than what we have now ;-). Jun 8 at 14:27
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    @StephenKitt: Exactly! I would enjoy a question about the definition of an "operating system" or what would qualify as a minimal operating system, but it would be off-topic here and possibly for all of Stack Exchange. Jun 8 at 16:33
  • With any computing question of the form "what was the first X", the Manchester Atlas is always a good guess.
    – JeremyP
    Jun 13 at 10:12

Though the following two systems don't refer to themselves as operating systems, they are control systems for early computers --

  1. Lyons Eectronic Office (LEO) in the UK, implemented in 1951 and surviving until 1965.


"In 1951 it processed the Lyons bakery valuation data and went on to handle payroll, ordering, stock control, tea blending and so on."

  1. MIT's Director system, presented on March 8, 1955. It ran on MIT's Whirlwind computer.

https://www.wired.com/2010/03/0308doug-ross-director-tape/ https://www.computerhistory.org/tdih/march/8/

"Director could be considered a rudimentary operating system since it allocated and controlled system resources (like memory, storage, and printing) automatically during execution of a user's program."

"The Director tape would communicate with the computer through a separate input reader. That means different tapes with various problems to be computed would be recognized and appropriately processed. A Director tape would make a complete run possible by pushing a single button."

In 1968 I ran an IBM 360/75 with 512 KB of memory for the US Air Force, running OS/360. That was a very sophisticated system and O/S for its day. The idea of an O/S then was not especially a new concept.

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    Those links all seem to be modern writing. I'm not looking for the first operating system but the first time the term "operating system" was used in its usual current sense. I've attempted to clarify the wording in my question but I'm not sure I nailed it. Jun 8 at 12:55
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    I understand now. Thank you for the clarification. I edited the lead-in to my response. Jun 9 at 9:00

The operating system for the Dartmouth Time Sharing System in 1967 was known as the executive. Nowadays it would be known as a kernel.

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