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Comment by usr1106 | Hacker News Reader

I was a trainee in an IBM lab nearly 40 years ago. All developers including myself worked using VM/CMS. That I remember for sure.

With production workloads I had nothing to do, so I am not sure what was the most commonly used OS. Pretty sure no bank clerk, airline counter or similar ran CMS.

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Talking with some elder developers, it always seemed to me that VM/CMS combination was mainly popular at universities and labs, so arguably a related environment.

Probably was helped once people figured how to also run DOS and MVS under VM.

Airline Counters of course ran (and some still do) TPF, and serving massive amounts of users with standardised forms was much easier with CICS (I seem to recall a story about some retail chain actually running their POS on single mainframe in 1970s with each retail clerk using a 3270-compatible terminal to access CICS forms).

Yes, CICS came to my mind. But CICS is not an operating system, it needs one to be run AFAIK. The Wikipedia article says it runs under VM/MVS or VM/VSE.

OS/360 was discontinued. MVS is listed as one of its successors.

So I believe, while interesting, the VM/CMS emulator/simulator mentioned above is only representing System/370 period, not System/360.

I am certainly not an expert on the matter.

Edit: Following a couple of Wikipedia links tells that in the 360 period something called CM/CMS existed. It seems only loosely related to the VM/CMS used in the 370 period.

Edit 2: For an emulator see https://en.m.wikipedia.org/wiki/Hercules_(emulator)

Edit 3: https://en.m.wikipedia.org/wiki/History_of_IBM_mainframe_ope... seem worth reading. The 360 chapter links nicely to TFA, e.g. The Mythical Man-Month.

VM/CMS from my understanding started in System/360 period, but it was not really something advertised - initial versions ran on specific models only, and even later on it wasn't necessarily available to officially purchase.

I don't think virtual memory existed on the 360. The unofficial OS provided to some important customers dissatisfied with the nightmare delays in OS/360 was CM/CMS. Maybe the CM/CMS command line experience was already rather similar, I don't know.

Virtual memory did not even exist in the first S/370 models, that was a slightly later feature.

Disclaimer: Thinking is different from knowing :)

The origin point was, according to my searches, specially modified S/360-40, where CP-40 (VM's "grandpa") was developed as well as CMS.

This was followed by S/360-67 which introduced address translation to S/360 and was specially built for timesharing - there, CP-67 was developed, and since model 67 was sold normally, it was apparently provided to some customers as alternative OS. CP-67 evolved into VM/370

Yeah, when reading VM I thought too much about virtual memory. But IBM famously never used the term memory, but called it storage. So VM probably only referred to Virtual Machine. So their first virtual machines including all during 360 era, probably still showed physical adresses, even if more than one virtual machine could using the same addresses exist. None of them had page tables, they all had the same addresses. First MVS (multiple virtual storages) changed that.

Mainframes notably call memory “storage”, so virtual memory becomes “virtual storage”. The idea of virtual machines in mainframes is closely tied to user logins as you get “your own” machine on logon. IBM mainframes diverged from the OS tree very early on and evolved similar services, but with very different conceptual frameworks.

I worked for a few banks starting in the 1980’s. It was all MVS. End user applications were created using CICS and IMS. What we used to call OLTP (online transaction processing).

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