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Many things around the '80s or earlier use ‘/’ in their abbreviations and sometimes even in their names, for example

Nowadays it's typically used to express or or (sub)division so I find it a little bit weird. Why was it used like that?

phuclv
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    You forgot S/360 (1964), probably followed by PL/I (which you didn't forget). – chthon Mar 27 '22 at 10:51
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    @chthon: S/360 seems to be a favorite pattern (general/specific) of IBM, they also had S/34 and all their other names like PS/2, OS/2, PL/I. But, of course, they seemed to brreak that with z/OS for some reason. – paxdiablo Mar 27 '22 at 12:08
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    Maybe the reason is nothing more than IBM, and others of the era, trying to catch the "halo effect" from the S/360 name. – Brian H Mar 27 '22 at 17:31
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    VAX/VMS Virtual Address eXtension/Virtual Memory System and RSTS/E Resource Sharing Time Sharing Extended - Digital Equipment Company. – IconDaemon Mar 27 '22 at 21:56
  • And "VAX-11/780" is less of a mouthful than "VAX-11 model 780". – dave Mar 28 '22 at 01:25
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    I just wish to note one that is almost certainly an outlier: the "Apple //c." There it just seems that the / was used instead of an I for stylistic reasons. It's the Compact version of the Apple II computer. – trlkly Mar 28 '22 at 07:57
  • If I look at a modern keyboard, I'd say that only three delimiters look sensible: space, solidus, and hyphen, as in System 360, System/360, or System-360. Anything else has a sort of "trying too hard" look: System:360, System.360, System(360), etc. – dave Mar 28 '22 at 13:36
  • And then on System/360 there was the programming language APL\360 ツ – John Doty Mar 28 '22 at 17:17
  • @IconDaemon There was also RSX/11 from DEC. However they also had PDP-11, RT-11, etc. – user207421 Mar 28 '22 at 23:41
  • @another-dave simply use System360 or PS2, it makes more sense – phuclv Mar 29 '22 at 03:05
  • @user207421 - the systems were RSX-11M, etc. Hyphen, not slash. When DEC put a machine-related number on software, it was always offset with a hyphen: FORTRAN-10, MACRO-11, BLISS-32. It follows from the machine names: PDP-11, etc (with the obvious change fir VAX). Model numbers used slash: PDP-11/45, etc. – dave Mar 29 '22 at 12:06
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    I've always wanted to know how Spanish speakers pronounce OS/2. – Dawood ibn Kareem Mar 29 '22 at 23:06
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    @trlkly, Apple have a long history of strange naming, with their Apple //, II, ][ and so on :-) – paxdiablo Mar 30 '22 at 01:05
  • Because 1) It's easier to type than a dash ("-") and 2) until the rise of URLs, slashes in names weren't a big problem for most people/things. – RBarryYoung Mar 30 '22 at 16:40
  • @RBarryYoung I'm going to use PS2, no need for anything like PS-2 – phuclv Mar 30 '22 at 16:59
  • @phuclv Sony would like a word with you. – ssokolow Mar 30 '22 at 21:08
  • Is that not broadly because "old systems" had access to many fewer options than ours do today, which made "slash" very much more useful than it would be today? – Robbie Goodwin Apr 02 '22 at 18:37
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    in OS/2, it's obvious it's a divider, "half an operating system" – Tommylee2k Jan 13 '23 at 09:07

4 Answers4

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Well, at least on some of those, it's a quite natural divider, such as you would see in:

  • 7 days/week (per).
  • 13 sectors/track (per).
  • Dear Sir/Madam (or).
  • 3/7 (of/over).

For your cited examples, they are read as:

  • CP/M, from Digital Research Inc (DRI), was the control program for microcomputers, though it may have originally been control program and monitor. See here or, if you want it direct from Gary Kildall, his "Computer Connections: People, Places, and Events in the Evolution of the Personal Computer Industry" manuscript (available at the Computer History Museum) states:

    So, I built an operting [sic] system program using the simulator. I called it CP/M, or a Control Program for Microcomputers, mimicking the name PL/M. For me, CP/M's sole purpose was to support the PL/M language. Nothing else.

  • MP/M, multitasking program for microcomputers, though multi-programming monitor and control program for microcomputer systems development in DRI's original specification.

  • Several others were also from DRI and followed a similar nomenclature: CP/NET and MP/NET were similar to the preceding two but meant to operate over networks, hence control/multitasking program for networks.

    • Similarly, CP/NOS and MP/NOS were for network operating systems (diskless configurations).

  • PL/M, programming language for microcomputers, foreshadowed above in the CP/M bullet point but more directly in the same document:

    PL/M stands for a "Programming Language for Microcomputers," and is still used by Intel customers today, though largely supplanted by the "C" programming language.

  • PL/S, programming language for systems. See references on the Wikipedia entry. Note that this was eventually replaced with PL/X, which is, at least up to several years ago when we parted ways, IBM's internal-use-only (I think) language for today's mainframe.

  • OS/8, the OS for the PDP-8. PS/8 I'd never heard of but it looks like (from cursory investigation) an early name for OS/8. The Wikipedia entry supports this as does the fact a later OS/12 was built for the, wait for it, ... , PDP-12 :-) An unofficial history FAQ also cites these, stating that OS/8 came from the unfortunately named (though probably intentional) "Fully Upward Compatible Keyboard Monitor", or *BLEEP* MONITOR :-)

  • MS/8 was also similar in that it was the monitor system for the PDP-8.

Contrast this "something something for something" approach with the (albeit fictional) MCP master control program from the original (and much better despite the much less modern graphics) Tron movie :-)

Some others, coming from IBM, have a similar format, seemingly dividing the general term from the specific instance:

  • PS/2, personal system 2.
  • OS/2, operating system 2, not half an operating system, as the early Windows crowd sometimes suggested :-)
  • PL/I, programming language 1.
  • PL/8, programming language 8 although it appears IBM usually referred to this as PS.8, humourously 80% of PL/I.

The PS/2 port, which is a type of connector into which mice and keyboards are plugged into, is so named because it was first introduced on the PS/2. It is a mini-DIN connector. Previously (and this is before USB prevalence), PCs generally used a larger (DIN) connector.

paxdiablo
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    That's also the intended etymology for "GNU/Linux"... like the "over" in ½ (1 over 2). "GNU userland on/over the Linux kernel". – ssokolow Mar 27 '22 at 12:23
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    CP/M was originally Control Program/Monitor and even when reading / as for I still find it weird – phuclv Mar 27 '22 at 14:32
  • "despite the shoddy graphics" ? I must furiously disagree here. Thee graphics were a unbelievable, awe-inspiring perfect. The smooth surfaces of the tanks alone. Serious. I was STUNNED had to see it several times to believe these sequences were really computer made. Can' t really remember much of the (not really big) story, but I still can close my eyes and see the incredible graphics. – Raffzahn Mar 27 '22 at 15:52
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    @phuclv / can be for, and, or and many other words, all depending on context, so in Control Program/Monitor it read Control Program and Monitor – Raffzahn Mar 27 '22 at 15:54
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    I find the 1st half of this answer deeply unconvincing. You've started with "slash is a natural divider" and cited 2 examples where it's used as a stand-in for "per": "7 days per week", "13 sectors per track". And then listed a bunch of places where it's standing in for the word "for". I can't think of any modern places that I'd use slash as "for"? – Brondahl Mar 27 '22 at 19:15
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    @Raffzahn: I loved it as a kid and the individual graphic elements were good, like the tanks and bikes on the grid, though the "bit" was annoying to the level of Jar Jar Binks/Wesler Crusher :-) But the over-shimmering-blue-water lakes of energy was particularly bad. Keep in mind I'm comparing it to what we have now as well, which is probably not a fair comparison. – paxdiablo Mar 27 '22 at 23:01
  • @Brondahl: you are aware that "per" means "for each", yes? That's why I used the phrase "natural divider" rather than "for". The former includes things like "Dear Sir/Madam" (sir or madam), and "3/7 (three of seven). I'll adjust the answer accordingly. – paxdiablo Mar 27 '22 at 23:12
  • @paxdiablo No, comparison to later works is never fair. The same way as comparing classic games to modern ones isn't, even with 'pixel-art' games. They do not have to cope with limitations of back then, so their achievement isn't the same. And yes, I do in part agree about Bit. Then again, it was quite cool as well. keep in mind, even the term bit wasn't really common knowledge in 1982. (Then again, I have to admit I like Jar Jar Binks - he is essentially the only fresh (main) character in all of E1 - if not all of the new movies). – Raffzahn Mar 27 '22 at 23:22
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    @paxdiablo If you're asserting that CP/M is representing Control Program for each Microcomputer then sure. But that doesn't seem likely. You've expanded your examples, but still not given any that map to "for" in the way you've then used it in your answer. – Brondahl Mar 27 '22 at 23:43
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    @paxdiablo another way to resolve this could be: can you give a citation for you suggested expansions? If those phrases are known to be what the 'acronym' stood for, then whether I agree with that usage of slash becomes entirely irrelevant. – Brondahl Mar 27 '22 at 23:45
  • @Brondahl: tracked down some citations and added, hopefully that will make the answer better. I'm not keen on adding too much more since, at some point, the size makes the answer (while more informative) a little unwieldy :-) – paxdiablo Mar 28 '22 at 00:33
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    @paxdiablo fair enough; I'm sold :) – Brondahl Mar 28 '22 at 06:37
  • @paxdiablo It might be useful to order the examples by time, as that gives for some an easy to follow heritage. Like the inheritance of that stylization from PL/I being defined by IBM for and together with the S/360, to PL/M a simplified implementation of PL/I by Kildall for Intel to CP/M to Kidall's own CP/M and it's later derivatives. – Raffzahn Mar 28 '22 at 11:42
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    Seems to me the "X for Y" phrasing is a sporting thing. In sports, "he's 3/3" is often pronounced "he's three for three." – Dewi Morgan Mar 28 '22 at 20:01
  • Note on the "PS/2 Port" for mice and keyboards - the port name comes from the IBM PS/2 computer, where they were first introduced, so that's the same origin. The fact that the ports long out-lived the computer they were first designed for is something of an accident of history. (They're still seen on some modern desktops to this day, even though the peripherals they were made for have mostly all switched to USB.) – Darrel Hoffman Mar 29 '22 at 19:34
  • Thanks, @DarrelHoffman, I missed that one in the original list. Added to answer. – paxdiablo Mar 29 '22 at 23:58
  • @ssokolow (1/2) That might be news to the GNU project. They have their own explanation: “Linux is normally used in combination with the GNU operating system: the whole system is basically GNU with Linux added, or GNU/Linux. … People could then combine Linux with the GNU system to make a complete free system—a version of the GNU system which also contained Linux. The GNU/Linux system, in other words.” – Brian Drake Mar 31 '22 at 14:02
  • (2/2) I am sure that I read specifically that “GNU” comes first because of its larger contribution, but I don’t have a citation now. – Brian Drake Mar 31 '22 at 14:03
  • @BrianDrake Well, if you're going by largest contribution, then it'd be X11/GNU/systemd/Linux or possibly X11/systemd/GNU/Linux. Stallman put his finger on the scale by defining GCC and emacs as part of the OS and excluding a GUI, because, according to him, an OS is what you need to self-host its development and nothing more. Honestly, I'd like to see musl-libc and uutils become sufficiently drop-in compatible with GOG.com games that I can give the finger to people who whine about use of a name with too many syllables to ever catch on. We have enough trouble with "Ubuntu Linux, not Ubuntu". – ssokolow Mar 31 '22 at 21:00
  • ...unless you're talking about ABI... then it'd be glibc/Linux for the CLI apps or X11/glibc/Linux for the GUI ones... and, sure enough, applications like Firefox use something like X11; Linux as their platform identifier... typically, when it's compacted that far, on the basis that glibc is assumed to be the libc for Linux builds. – ssokolow Mar 31 '22 at 21:07
  • I'd never noticed before that PL/I uses roman numeral, rather than the usual digit 1. – Toby Speight Apr 19 '22 at 16:30
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    IBM's publications always called it PL.8 not PL/8. The .8 is meant to be read as 80% of PL/I. I think PL/8 is officially wrong, albeit common. This was yet another of IBM's numerous secret dialects of PL/I, and all the others were named with a slash, so it is no wonder people named it with a slash too, even if that's wrong – those other secret dialects being the mainframe systems language PL/S (later renamed to PL/AS then PL/X), its IBM 8100 derivative PL/DS, and its AS/400 derivatives PL/MP and PL/MI – Simon Kissane Jan 12 '23 at 02:15
  • Is it possible that everyone else just copied it from CP/M? – user253751 Jan 13 '23 at 08:30
  • @user253751: unlikely, PL/I has been around since the 50s, I think. CP/M only came out in the 70s. – paxdiablo Jan 13 '23 at 10:55
  • @user253751 - rather than everyone copying it from CP/M, CP/M copied it from IBM. Before creating CP/M Gary Kildall worked at the Naval Postgraduate School, where he used an IBM mainframe operating system called CP/CMS – I think its name inspired that of CP/M (and likely also the idea of drive letters). Kidall wrote CP/M as an OS to go with his programming language PL/M, whose name was obviously inspired by IBM's PL/I programming language. CP/M is from 1974, PL/M from 1973, CP/CMS is from 1968, PL/I from 1964. – Simon Kissane Jan 16 '23 at 02:40
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In addition to Paxdiablo's computing centred list it might be worth to add that it's more of a linguistic issue than a technical or computing one.

The Slash was quite present way before data processing, back then known as Solidus or Oblique. Solidus, Latin for Shilling, as it grew out of the long-s, a letter, lost to modern Alphabets, used separate Shilling from Pounds. The long-s looks a bit like a stroke with a hook. The hook got lost over time due sloppy writing, transforming it into a straight slash. Solidus is in fact the name used within the Unicode classification for what we commonly call a slash.

Development and use case goes roughly:

  • Slashes have been used as number separator long before Comma and Dot settled like today. This dates back to at least the 16th century.

  • The usage is originated in the fact that in handwriting spaces can be rather random in width and appearance. Thus, separation is needed/helpful, some symbol gets inserted. Either a specific, or a generic like a slash.

  • In fact, in many early Latin texts and many medieval handwriting spaces were optional or omitted at all. If a word separator was needed, like to switch for numerals, a middle dot was common.

  • Slashes are still common in some countries (e.g. USA) as date separator (YY/MM/DD).

  • It was and is used wherever one wants to concatenate items but still mark em as distinct. Like the PL/I example, were it serves to enable reading 'I' as one instead of the letter I.

  • Similar the use with other product names like System 360 abbreviated to S/360. This continues with S/360-67 as abbreviation for the System 360 Model 67. Here a hyphen is used as secondary divider

  • Usually these applications are about saving space, so the slash may as well serve as replacement for various words. They can stand for and, or, for or many others.

  • This essentially works like the title case used in English language publications. All words not capitalized are candidates to be left out at whole, or replaced by a slash. Like Control Program for Microcomputers becomes CP/M.

  • In addition, much like there isn't one title case, but each publication fosters their own, people tend to make up their own variation - for example it's common to write simply 360/67 instead of S/360-67.

  • Speaking of, even companies change mid way, as there are as well IBM publications writing like that - or turning everything upside down by creating z/OS for something that started out as OS/360 :))

  • Of course all of this is in addition garnished with heaps marketing related stylization, great for flashy advertisement and even better to play trademark games.

  • The whole thing goes not only for products, but company names as well, or who remembers that M/A/I (sometimes M|A|I, today MAI) originally stand for Management Assistance Incorporated?

Long story short: Once it was about abbreviations, today everything goes, use it whenever pleases your intention.

Now, when looking at computing in particular, then there is a clear lineage, at least for some of the usage:

  • IBM stylized PL/I to fit the scheme started with the together with the S/360

  • Which in turn may have originated in use by US military bureaucracy like Another-Dave pointed out.

  • Intel's PL/M is a simplified implementation of PL/I, so it's name follows the precedence set.

  • PL/M was written for Intel by Garry Kildall. When creating CP/M, not long after, the naming choice was obvious.

  • Not much sleuth skills needed to see the continuation in MP/M and all that followed in DR's timeline of OSes.

Raffzahn
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    Hmm, technically solidus isn't Latin for shilling, it means solid, in that the Roman coins were close to pure gold. The term shilling came much, much later as the name for the British coin, though its etymology stretches back to earlier times (but not so far as the Roman collapse, I suspect). It may be more accurate to say that the original shilling was English (proto-something-or-other, more likely) for solidus. This is the sort of obscure information you can gather by listening to "The History of English" podcast :-) That doesn't detract from an otherwise very informative answer, however. – paxdiablo Mar 28 '22 at 06:09
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    The abbreviations for the old currency were £sd. £ is a stylised L (which is often seen in 19C manuscripts) and stands for "libra pondo", a "pound by weight". "s" as mentioned above was solidii which became "shillings" in English usage, and "d" is for denarii which became the penny. As a footnote to £, recall that the abbreviation for pounds weight is "lb" and you can see the common origin. The Norman £ was one lb of silver, specifically silver "starlings" (pence) from whence "Sterling". –  Mar 28 '22 at 08:36
  • @Martin Well, to be fair, it was the Carolingian system introduced in the 8th century in Europe and soon after on the British Islands. Normans only came into play a century or two later. – Raffzahn Mar 28 '22 at 10:53
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    Yes, but the terms "Lsd" and the £ symbol are a bit more recent, as are 19C manuscripts! Some of us ancients still remember learning Lsd at school, and indeed using it. My first pocket money was 1/-, rising later to 1/6. When my Great Uncle visited he used to shake hands with us kids, and palm off half a crown which Mum pretended not to notice. Homework for you: why was 13/4 a sum we had to memorise at school? ;-) –  Mar 28 '22 at 11:05
  • @Martin Well, wouldn't this be a Scottish Mark? Not only the English learned about LSD - I remember them being topic in 4th grade lecture in Bavaria in the 1960. Of course more of a curiosity to show kids that there are other (ancient) systems as well. Of course, being me, it cranked my imagination :)) Also, that Handshake might be universal to all Uncles all over the world. just the denomination might have been different :)) Regarding the 19C part, main point for having it mentioned above was the usage of a long-s - not a short one - at exactly that time. – Raffzahn Mar 28 '22 at 11:18
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    @Martin - two-thirds of a pound (twice six-and-eight). – Michael Harvey Mar 28 '22 at 12:05
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    A customer from Australia kept explaining a command format that included an "oblique". Inasmuch as I couldn't rotate characters 90 degrees (not in the '80's, anyway :) it took awhile to discover they were referring to the good old "slash". – gbarry Mar 29 '22 at 14:56
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    @gbarry: I've had similar issues with people calling the octothorpe/hash (#) a "pound", presumably because £ exists at shift-3 on UK keyboards. Or so I thought. As always, this led me down a rabbit hole regarding the actual source of the name which I won't go in to here since it's rather lengthy :-) – paxdiablo Mar 30 '22 at 00:04
  • @paxdiablo It's not really about where the pound symbol is placed on the keyboard. It's that the pound glyph replaced the hash glyph in the UK's version of 7 bit encoding, ISO 646 - IR-4 (BS 4730). So any 'ASCII' value of X'23', producing a # on a computer/terminal using ISO IR-6 (US-ASCII) will display a £ on one using IR-6, which is what genuine UK computers do (Well, the BBC replaced Accent Grave instead to allow both in 7 bit encoding). Any # you've seen on your screen was a £ on his. – Raffzahn Mar 30 '22 at 00:31
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    @gbarry: Slash has two vulgar meaning in British (and I suspect Australian) usage, so there is a tendency to avoid it. See https://en.wiktionary.org/wiki/slash#Etymology_2 –  Apr 17 '22 at 17:50
  • Just for interest: it's common practice in cave surveying still to use / in preference to . or , as decimal separator, as the former is much more likely to survive liberal quantities of mud and still be identifiable (or confidently absent). – Toby Speight Apr 19 '22 at 16:34
  • Did MAI really have slashes as part of the company name, or just as a design feature in the logo? I worked for MAI Basic Four ~1980 and didn't know that. Though, to be fair, I see that the name of the company I worked for was apparently "MAI Basic/Four" and I don't remember that slash (oops, I mean solidus) either. So maybe my memory is shot. (Sad.) – davidbak Aug 08 '22 at 15:41
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This answer doesn't really answer the question of "why". But in any case....

In technical/computing fields, the solidus appeared in US military project designations. A few examples:

AN/FSQ-7 - , vacuum tube computer, part of the SAGE air defense system.

AN/FSQ-32 - solid state computer, also SAGE.

AN/FSG-1 - anti-aircraft defence system.

The structure of such names is that "AN" means "Army and Navy", "FSQ" is "Fixed Special eQuipment", and so on. The numeric part is a specific project.

It seems to me that the solidus is essentially an arbitrary choice of punctuation symbol to separate two logically distinct parts of the name, as is the hyphen before the numeric identifier. There's no more to it than that.

dave
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  • I understand / in case of separation because I already mentioned (sub)division in the question, but it's not like that for CP/M or PS/2 or most of the names I listed above – phuclv Mar 28 '22 at 02:58
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    I do not see the distinction that you do. – dave Mar 28 '22 at 12:43
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    I also don't see the distinction. To me it seems like all are cases of "DOMAIN/SPECIFIC", rather than an abbreviation of the word "for". – Brian H Mar 28 '22 at 13:36
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It is being used in the same way as you describe the modern usage- to express a subdivision of a whole.

In the case of your cited examples, the division is between the Domain and the Specific instance. Domains are things like "OS", "CP", "PL", etc. and the part after the "/" names the specific instance. So, you can best understand it as:

"In the Domain of Control Programs, here is the Microcomputer specific one- CP/M".

-OR-

"In the Domain of Operating Systems (for IBM PC's), here is specific revision number 2- OS/2".

It's rather simple and logical. The answer by another-dave makes this point as well, using examples that start with "In the Domain of Army and Navy gear..."

Brian H
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  • I'm not necessarily convinced about the 2 in OS/2 being a revision number or instance. Given that we had OS/2 1.3 (text only), 2.x, 3.x and 4.x/Warp(?), it seems that would be versioning information. OS/2 may have just been named as (originally) the operating system for the PS/2 (and the PS/2 may have been named as the (better) successor to the PC). Though, if you mean revision in a much wider scope, your answer makes more sense. – paxdiablo Mar 29 '22 at 01:35
  • Domain/Specific is exactly what I said in the question (sub)division. It's nothing new but I'm not convinced that most of the names are in the domain/specific format – phuclv Mar 29 '22 at 03:08
  • @paxdiablo OS/2 introduced a GUI in version 1.1 the text only version was 1.0 - the desktop was changed massively for 2.0 (From Wikipedia and my own experience programming 1.x) – mmmmmm Mar 31 '22 at 10:35
  • @mmmmmm: I stand corrected, thanks for the clarification. – paxdiablo Mar 31 '22 at 14:28
  • APL\1130 and APL\360 represented a bit of rebellion against the IBM culture that demanded this pattern. – John Doty Jan 22 '23 at 15:22