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Saving time: 1) "mainframe" as the hand-wavy term that it is, is most stronglydefined by the COMPANIES AND CUSTOMERS that CONTINUE to develop and purchase them, obviously in addition to the historical record. IBM, or their competitors are, in this case, the "authorities" whose notion of where to draw the lines is the reference. 2) As it stands, product offerings exist for HPC mainframes that can be easily referenced with face-palm obvious examples. Drug discovery (an industry that strangely depends almost as strongly on low-error, auditable computational power as the banking or securities industiries). There are at least a few mainframes marketed to drug discovery companies that are based on custom silicon, with custom software, and deployed within a custom operating system environment. These are miles short of "supercomputers", with the largest systems fractions of the size of the oldest LINPAC systems many steps away from "clusters" or any other term. THe same is true of contemporary non COTS based Neural Network hardware offerings, which *notoriously* include non-standard and completely bizarre custom software ("Wafer scale single chip" system anyone?). Mainframes are most importantly characterized and distinguished by being PRODUCT OFFERINGS and not just generalized schemes for enterprise scale systems. This is a hard reqirement. ALL mainframes are products developed by company and sold or deployed as either a discrete one-time purchase or service contract. Usage requirements are even more general than transaction-heavy. THey must be high-uptime with low error, auditable or with a comparable functionality, and come equipped with high levels of security. Those factors overshadow EVERYTHING else even compared to high speed or high computational power. You could walk away with that defintion: A commercial enterprise scale computer system that is designed to deliver highly reliable low error performance with high security, among other characeristics that combined toghether cannot be met with COTS based system architecture nor software67.165.123.62 (talk)19:12, 22 August 2023 (UTC)[reply]

There's currently a little boring drama on Wiktionary about the origin of "mainframe", and whether it really refers to a solid cabinet, or something else.[1] I would really appreciate any evidence from experts, or very old nerds, regarding the etymology. Hit me up.Equinox◑04:29, 21 February 2024 (UTC)[reply]

Not sure what asolid cabinet is. I believe many have thin metal removable sides, where the frame is solid, but the sides are not. The sides are decorative, and not part of the structure. I suspect that kitchen cabinets can be designed where the sides are part of the structural integrity, and others that are not.Gah4 (talk)04:59, 21 February 2024 (UTC)[reply]

@Gah4: The point is what is the "frame". (See Wiktionary page history at "mainframe".) Are you old and experienced enough to tell for sure? I'm passing middle age but "frame" to me means that piece of shit you'd put your webring in. Lordy.Equinox◑06:15, 21 February 2024 (UTC)[reply]

Historically, the termmainframe included computers that ran a single job at a time. The frame for the CPU was typically a metal cabinet with a height of 1-3 meters. Typically the 1960s frames usedwire wrap backplanes to connect multipleprinted circuit cards. --Shmuel (Seymour J.) Metz Username:Chatul (talk)14:10, 21 February 2024 (UTC)[reply]

I was trying to compare againstcabinet. A kitchen cabinet commonly is solid on all sides, though one is an openable door. The frame for a mainframe is commonly metal rectangles that hold the parts inside together. Even with everything closed, there is need for ventilation, so some sides will have holes, or otherwise openings, or might be completely open.Gah4 (talk)01:33, 22 February 2024 (UTC)[reply]

Power and coolant connections are commonly on the top or bottom. Also, it is common for a door to include wiring. --Shmuel (Seymour J.) Metz Username:Chatul (talk)15:56, 22 February 2024 (UTC)[reply]

Mainframe is/was a computer housed in a large cabinet[2]. Early units either consisted of or roughly conformed to the framing of a19-inch rack.- LuckyLouie (talk)16:17, 22 February 2024 (UTC)[reply]

I worked for IBM for two decades beginning in the late 1970s designing integrated circuits, many of which were forIBM System/390. In the early days of computers, the electronics were heavy and had to be mounted on heavy steel frames that were strong enough to handle the weight. There might or might not be decorative covers. The engineering prototypes of System/390 were operated without covers.

When the electronics became lighter, small computers were mounted in19-inch racks, a pre-existing standard standardized by AT&T about 1922. Computers mounted in these racks were known asminicomputers. Large computers took advantage of lighter electronics by increasing the number of circuits, and making the cooling more sophisticated, so the heavy steel frames were still needed to mount them.

A possible source of confusion is that mainframe families had a range of performance; while the highest performance family members had steel frames, the lowest performance members might use 19-inch racks or even fit on a desktop. I'm not sure what the structure of the most recent high performance mainframes is.Jc3s5h (talk)17:27, 22 February 2024 (UTC)[reply]

TheIBM z16 still uses a 19"^[1] frame. --Shmuel (Seymour J.) Metz Username:Chatul (talk)21:04, 22 February 2024 (UTC)[reply]

@Rodw: Anonymous editpermalink/1252806059 changed the caption for File:IBM System Z9 (type 2094 inside).jpg fromInside anIBM System z9 mainframe toInside anIBM System z9 mainframe that has a IBMThinkpad integrated into the system as a terminal. TheThinkPad serves as auser interface for systemadministrators and developers, enabling them to interact with the mainframe’soperating system, oftenz/OS, through a terminal emulator. TheThinkPad’s lightweight design and portability provide flexibility, allowingstaff to manage the mainframe from various locations within the facility or even remotely.The connection between theThinkPad and the z9 is facilitated through a securenetwork protocol, ensuring thatdata transmission remains encrypted and secure. Users can execute commands, monitor system performance, and manage jobs using theThinkPad, while the mainframe handles complexcomputations and data processing tasks in the background.

The Thinkpad depicted appears to be theHardware Management Console (HMC), which is used by theoperator to control, e.g., the hardware, thePR/SM configuration. A secondary function is to serve as a low performanceoperator console via a proprietary interface. The HMC is not supported as a terminal, and remote access to it is limited to HTTP.

I was going to remove the incorrect material and puffery, but I'm not sure what level of detail is appropriate, e.g., should the caption mention the two thinkpads running Support Element (SE) software and capable of serving as backup HMCs. --Shmuel (Seymour J.) Metz Username:Chatul (talk)13:47, 23 October 2024 (UTC)[reply]

I don't have the expertise to advise on this - I was just trying todisambiguate a couple of links.—Rod^talk14:03, 23 October 2024 (UTC)[reply]

This article has a mixed date format. Since it uses American English, I suggest using the month day, year format since that format is the most common with American English.Jc3s5h (talk)16:07, 31 January 2025 (UTC)[reply]

Done.Guy Harris (talk)18:01, 18 February 2025 (UTC)[reply]

WRT "A mainframe computer, informally called a mainframe, maxicomputer, or big iron"

I wouldn't say that 'mainframe computer' is any moreformal that 'mainframe'. I would say that 'mainframe' is way more notable than 'mainframe computer'. The latter is two notable terms shoved together. The 'computer' part is context. IMO the title should beMainframe (computer) orMainframe (computing).

And, I've never heard of maxicomputer or big iron. Cited, yes, but I question their notability.Stevebroshar (talk)15:03, 25 December 2025 (UTC)[reply]

I would say that 'mainframe' is way more notable than 'mainframe computer'. For what it's worth, Google Ngram appears to be saying that "mainframe" by itself is a *lot* more common than "mainframe computer" -https://books.google.com/ngrams/graph?content=%22mainframe%22%2C+%22mainframe+computer%22&year_start=1800&year_end=2022&corpus=en&smoothing=3.

We haveMainframe (disambiguation), but it lists only an animation company and a bunch of fictional characters; I suspect the company chose their name because of the term "mainframe" as in "big computer", and that the names of the fictional characters were chosen for the same reason.

Maybe there was a concern that "mainframe" might refer to the cabinet rather than the system, so that "mainframe computer" provided disambiguation, but I'm not sure that's the case in reality. I think aWP:COMMONNAME case can be made for just [[Mainframe]] and, if that's not accepted, for your other suggestions.

And, I've never heard of maxicomputer or big iron. Cited, yes, but I question their notability.According to Google Ngram, "maxicomputer" first popped up in 1958 or so, peaked around 1979, and dropped off from them, butrelative to "mainframe", it's in the noise.

"Big iron" hadthree peaks - one in the 1870s (yes, that's an "8" after the "1"), one in the 1930s, and the biggest one in 1998. The first two probably didn't refer to computers - Babbage worked on theanalytical engine decades before the 1870s. :-)It's still in the noise relative to "mainframe", andits peak was lower but wider than that of "maxicomputer". I've definitely heard it as a slang term for big computers; I'm not sure whether I've heard "maxicomputer".Guy Harris (talk)20:03, 25 December 2025 (UTC)[reply]

@Guy Harris:For decades IBM has been offering web servers on the mainframe, along with interfaces such asREST andSOAP. However, I don't know of any evidence that they've largely supplanted older POS terminals and 3270 interfaces on workstations. Maybe drop the sentence but add a paragraph on new interfaces? --Shmuel (Seymour J.) Metz Username:Chatul (talk)14:50, 20 January 2026 (UTC)[reply]

The two paragraphs talking about user interfaces are:

In the late 1950s, mainframes had only a rudimentary interactive interface (the console) and used sets ofpunched cards,paper tape, ormagnetic tape to transfer data and programs. They operated inbatch mode to supportback office functions such as payroll and customer billing, most of which were based on repeated tape-basedsorting and merging operations followed byline printing to preprintedcontinuous stationery. When interactive user terminals were introduced, they were used almost exclusively for applications (e.g.airline booking) rather than program development. However, in 1961 the first academic, general-purpose timesharing system that supported software development,CTSS, was released atMIT on anIBM 709, later 7090 and 7094.Typewriter andTeletype devices were common control consoles for system operators through the early 1970s, although ultimately supplanted bykeyboard/display devices.

By the early 1970s, many mainframes acquired interactive user terminals operating astimesharing computers, supporting hundreds of users simultaneously along with batch processing. Users gained access through keyboard/typewriter terminals and later character-mode textterminalcathode-ray tube displays with integral keyboards, or finally frompersonal computers equipped withterminal emulation software. By the 1980s, many mainframes supported general purpose graphic display terminals, and terminal emulation, but not graphical user interfaces. This form of end-user computing became obsolete in the 1990s due to the advent of personal computers provided withgraphical user interfaces. After 2000, modern mainframes partially or entirely phased out classic "green screen" and color display terminal access for end-users in favour of Web-style user interfaces.

So there are user interfaces for program development and use of the program you or your group have developed, and user interfaces for particular applications developed by somebody else. Both were originally batch, then interactive through printing terminals, then interactive through video terminals.

That's at least three types of "end user":

• people whose job it is to develop software;
• people whose job isn't to develop software but who are writing their own software to get their job done;
• people whose job involves using other people's software.

And all three of those ended up using, in addition to mainframes, minicomputers or superminicomputer or other flavors of midrange computers, as well as supercomputers, over time, in similar fashions (even batch mode, although that was probably less common in minicomputer-land).

Except for the batch part, that also continued into the desktop computer (personal computer and workstation) era.

A lot of the Web-style user interfaces are for a fourth type of end user - people who are using the computer for non-job purposes, e.g. ordering stuff online. That type of user became common in the personal computer era. They generally don't know whether what type of computer they're dealing with; it's just a Web server. And there might be a mainframe at the back end; whether the server code is running on the mainframe, or running on some other machines that communicate with a database server or whatever on the mainframe, is irrelevant to them.

So I'm not sure I'd count them in that discussion.

For the first group of mainframe users, that'sISPF and the like, I guess. I'm guessing that's not Web-based.

For the second group, they're probably developing that without a mainframe being involved at all - it's probably either for their desktop machine or a supercomputer.

For the third group, the machine they're directly using is probably a desktop PC or a PC buried inside a POS terminal or ATM. It might be running a Web browser, a 3270 emulator, or a custom app. I don't know which of those are the most common, or what the trends are. (And, again, the machine it's communicating with isn't necessarily a mainframe.)

For the fourth group, they probably weren't end users of any particular type of computer; they were using whatever $ONLINE_STORE had in the glass house. They're not necessarily even directly interacting with the back end; the program they're interacting with is something running on their PC or smartphone, whether it's a browser possibly running a pile-of-Javascript or an app of some sort.

At this point, I suspect the people whodirectly interact with mainframes are either developers or operators, so maybe that's what that second paragraph above should deal with.Guy Harris (talk)23:37, 20 January 2026 (UTC)[reply]

I'm confident that the POS and reservation terminals are not using a web interface.

There are quite a few people whose job is not to write software but who write mainframe tools to assist in their jobs or wwho write mainframe software as part of configuring software they are responsible for.

Yes, ISPF via TN3270 is the norm for mainframe software development. However workstation tools based onEclipse andVS Code, e.g.,IBM Developer for z/OS,IBM Z® Open Editor, are available.

Many tasks previosly done with ISPF interfaces now require web-based tools, e.g.,IBM z/OS Management Facility (z/OSMF)

Possibly TMI, butgit is available. --Shmuel (Seymour J.) Metz Username:Chatul (talk)14:24, 21 January 2026 (UTC)[reply]

I'm confident that the POS and reservation terminals are not using a web interface. I've seen salespeople at department stores looking up the availability of articles of clothing on the POS terminal with what looked rather like a Web browser. That may be separate from the cash-register functions, but, hey, it's probably just a Windows box, so they may have switched between the cash-register app and IE or Edge or Chrome or whatever. I also have some vague memories of a travel agent using a Web-based UI to make reservations, but that might not be somethingSABRE-scale.

There are quite a few people whose job is not to write software but who write mainframe tools to assist in their jobs That's the second group. I was thinking of, for example, social scientists who were using CTSS and Multics at MIT as early examples of that.

However workstation tools based onEclipse andVS Code, ..., are available. So do those run, in whole or in part, on a desktop machine rather than on the target machine?Guy Harris (talk)19:55, 21 January 2026 (UTC)[reply]

The trend is to provide web interfaces to legacy applications while retaining support for old protocols.

Eclipse andVS Code run on the workstation and communicate with a server hosted on z/OS. The debug support also accepts TCP/IP connections from the z/OS job running the debugger. The workstation can be a laptop or a desktop. --Shmuel (Seymour J.) Metz Username:Chatul (talk)21:38, 21 January 2026 (UTC)[reply]

This discussion seems way off base. Mainframe computers didn't come with a "user interface" any more than a modern X-86 or ARM chip does. Early mainframes did have elaborate operator consoles, with lights showing the content of registers, switches to start and stop the machine, and so on, but these were needed back when computers were unreliable and were repaired by replacing individual vacuum tubes and, later, small circuit boards. Consoles could also be used to for debugging software, but on large expensive machine, that was an exception.

As interactive peripherals became available, application developers invented human interfaces as needed, as part of their work. The human interface was part of the application, not part of the computer. And the most important advance in human interfaces, the GUI, wan't even developed on a mainframe, but on a specialized a work station, theXerox Alto. Today, large IBM main frames might run an Internet server stack, multiple Lenox distros and an airline reservation system whose interface dates back to the 1960s, all the same time.--agr (talk)02:27, 22 January 2026 (UTC)[reply]

User interfaces were developed as part of operating systems. --Shmuel (Seymour J.) Metz Username:Chatul (talk)06:31, 22 January 2026 (UTC)[reply]

Mainframe computers didn't come with a "user interface" any more than a modern X-86 or ARM chip does. Presumably you meant "a modern personal computer or x86-based/ARM-based server"; a mainframe wasn't just a CPU or multiple CPUs, it was a complete computer system. And the OS of those computers would be the ROM monitor's UI; the UI that most uses see most of the time is the UI of the operating system, whatever OS that might be, and the programs running on it.

As interactive peripherals became available I'd say thatJCL is a human interface, just not aninteractive one. (Although somebodydid develop a Un*x shell that had a JCL-like syntax; as its author wrote in the README for it, "It was intended to run as a login shell on my new shiny sun, to discourage other users from taking my CPU cycles.") Nointeractive peripheral are needed.

application developers invented human interfaces as needed As Chatul noted, OSes themselves have user interfaces, whether it's a batch job control language or a CLI language or a GUI.Guy Harris (talk)08:14, 22 January 2026 (UTC)[reply]

Often the OS included an API to make it easy for an application to use the same user interface as the OS.

1. MULTICS
2. TOPS-20
3. TSO
4. VMS

The same is true for ISPF, although it is not an operating system. --Shmuel (Seymour J.) Metz Username:Chatul (talk)12:16, 22 January 2026 (UTC)[reply]

"...a mainframe wasn't just a CPU or multiple CPUs, it was a complete computer system. And the OS of those computers would be the ROM monitor's UI..." Early IBM mainframes did not come with any software and there were no such thing as ROMs. Early OS's were written by large users and IBM soon helped share them and made their own contributions. But it was only with the mid-1960s System/360, the third generation of mainframes, that operating systems become a major part of the mainframe product, and IBM had quite a struggle getting them to meet customer expectations. SeeHistory of IBM mainframe operating systems.--agr (talk)21:25, 23 January 2026 (UTC)[reply]

...a mainframe wasn't just a CPU or multiple CPUs, it was a complete computer system. And the OS of those computers would be the ROM monitor's UI... Sorry, that was poorly written on my part. "Those computers" was referring to x86 and ARM-based personal computers and servers; what Imeant to say was "TheUI of those computers would be the ROM monitor's UI", and what it was intended to indicate was that, if you're purely talking about the part of a personal computer or server system that's "the machine" rather than including the operating system and applications, the UI is the BIOS/UEFI/whatever's UI, not the OS's UI.

I.e., if you're going to think of "the mainframe" as just "the machine", not any OS or applications, yeah, the UI is the front panel or the maintenance console, not batch jobs or green-screen stuff, but the equivalent to that is thinking of an x86 or ARM-based personal computer or server as not including the OS or applications, either.

But it was only with the mid-1960s System/360, the third generation of mainframes, that operating systems become a major part of the mainframe product And those are the systems that the whole bit about card readers and printers, printing and green-screen terminals, etc. is talking about; it's not talking about anIBM 701 or even an7090/7094, it's talking about S/360, S/370, ..., IBM Z.Guy Harris (talk)23:29, 23 January 2026 (UTC)[reply]

IBM wasn't the only vendor. For users of, e.g.,Burroughs B5000,GE 635, the OS was inextricably tied to the machine. --Shmuel (Seymour J.) Metz Username:Chatul (talk)05:32, 25 January 2026 (UTC)[reply]

I'm mostly concerned about viewing mainframes through the lens ofinteractive computing. They had very little to do with each other. In particular calling a computer console orfront panel, which essentially every computer of the era possessed, a rudimentary interactive terminal is over the top. They were ubiquitous on computers of that era and provided operators the bare minimum needed to load, execute and stop programs, hence the term bootstrapping. On mainframes, they were mostly reserved for operators, not individual users.

We could and should have a separate section on mainframe software, with "main" references toHistory of IBM mainframe operating systems andHistory of operating systems. It could mention key points and perhaps give some extra emphasis on non-IBM mainframe software. That might be a place to mention interactive development on mainframes (eg the "By the early 1970s..." paragraph).--agr (talk)18:36, 30 January 2026 (UTC)[reply]

I'm mostly concerned about viewing mainframes through the lens ofinteractive computing. You mean mainframes running:

• Multics;
• OS/360 MVT,OS/VS2 (SVS),MVS,OS/390, andz/OS with theTime Sharing Option;
• Burroughs MCP with time-sharing;
• theDartmouth Time-Sharing System, version 2;
• CALL/360 andCALL/OS;
• CP/CMS andVM/CMS;
• EXEC 8/OS 1100/OS 2200;
• theTime Sharing Operating System;
• and, if you consider thePDP-6 andPDP-10 mainframes,the PDP-6 Monitor/TOPS-10 andTENEX (operating system).

They had very little to do with each other. If you mean "mainframes and interactive computing had very little to do with each other", no. See above. Yes, in the early days, "interactive computing" wasn't common for commercial computing, and later, as time-sharing systems became available on minicomputers and superminicomputer, and then as desktop computers/notebook computers/etc. became common, mainframes became less commonly used for time-sharing, but that's very far from "they had very little to do with each other".

And if you consider transaction processing applications used with desktop terminals to be "interactive computing", it's evenless true. It's not "computing" in the sense of the users writing programs and running them, but browsing the Web isn't "computing" in that sense, either;most computer use isn't "computing" in that sense.

We could and should have a separate section on mainframe software ... That might be a place to mention interactive development on mainframes Most if not all of the user interface of all types of computers is provided by software, not just the raw hardware. Not just the "By the early 1970s..." paragraph, but theprevious paragraph, would belong in the section on software.Guy Harris (talk)21:02, 30 January 2026 (UTC)[reply]

Most if not all of the user interface of all types of computers is provided by software, not just the raw hardware. That is exactly the point I am trying to make. There is nothing special about mainframe computers that allows for interactive computing. It's just one of many applications. And much user interface development took place on smaller machines. But I have no problem putting both paragraphs in a software section, as you suggest.--agr (talk)19:33, 1 February 2026 (UTC)[reply]

In particular calling a computer console orfront panel, which essentially every computer of the era possessed, a rudimentary interactive terminal

TheIBM 650 supported 10 inquiry stations in 1959; I suspect it's not the first. --Shmuel (Seymour J.) Metz Username:Chatul (talk)21:58, 30 January 2026 (UTC)[reply]

I'm not sure what you are trying to say here. The front panel on an IBM 650, while very useful for debugging, was hardly an interactive terminal, nor do I consider the 650 a mainframe. It was the low end of IBM's product line in the 1950s. And I think it's a stretch to call inquiry stations interactive computing.--agr (talk)19:33, 1 February 2026 (UTC)[reply]

I think it's a stretch to call inquiry stations interactive computing. What is your definition of interactive computing?Guy Harris (talk)20:03, 1 February 2026 (UTC)[reply]

There is nothing special about mainframe computers that allows for interactive computing. There is nothing special about mainframe computers that prevents it, either; several early time-sharing systems ran on mainframes.Most computer types aren't specialized for, or against, interactive computing.Guy Harris (talk)21:00, 1 February 2026 (UTC)[reply]

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