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Comment by ElevenLathe | Hacker News Reader

OS/360 dates to 1966. I believe z/OS in theory still provides compatibility back to applications of that vintage, though AFAIK it is a separate codebase.

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Z/OS is directly descended from OS/360. It's just a renaming. And yes, it continues to have almost complete binary compatibility back to 1966. I know for a fact that the IBM Fortran compiler from 1972 runs unmodified on z/OS today. Just pipe the 80 column EBCDIC data representing punch card images into the virtual punch card reader and off you go.

There was a big rewrite around MVS, but z/OS to this day executes a lot of code in 24bit address mode of S/360[1], and well, OS/360 code should mostly just run

[1] Easy to observe when running z/OS under Hercules, as one of the console modes shows the CPU address size mode. A lot of the time during bootup of basic ADCD you'll see 24, a bit less 31, and rarely 64

31 bits ought to be enough for anyone.

At least on z/OS, executable code still needs to be in lower 31bits space

If it ain't broke, don't fix it. And if it's broke just a little, someone probably depends on it for compat.

https://www.hyrumslaw.com/

> into the virtual punch card reader

as someone to young to have seen punch cards live this sounds really strange.

You can still create (virtual) punched cards on Linux. Just install the bsdgames package and run bcd. I guess punched cards are such a novelty that the bcd program belongs in "games".

Note that bcd, ppt, and morse are all in the same binary. ppt simulates punched paper tape and morse will encode/decode International Morse Code.

I actually ran these yesterday when I was explaining some computer history to my 19 year old son.

> You can still create (virtual) punched cards on Linux. Just install the bsdgames package and run bcd.

You can still create virtual punched cards on Linux by using the virtual punched card driver in the Linux kernel (which only works on IBM mainframes). Arguably a more realistic virtualisation than bsdgames since rather than just being a novelty it can actually be used to do something useful (such as integrate Linux applications with legacy IBM mainframe software when both are running in separate VMs under the IBM z/VM hypervisor - you can connect two VMs such that cards sent to one VM’s card punch appear in the other VM’s card reader.)

If you think about it, it is no weirder than Linux users talking about TTYs when no one has connected an actual teletype to a Linux machine other than for a laugh. The basic IO device becomes an abstraction that hangs around. Fun fact: you also boot Linux on zSeries by feeding a kernel image into a virtual punch card reader!

It gets crazier. At least back in the 1970s, you used to be able to emulate 7090 (IIRC) software on System/360. So if you have a 7090 program from the 1950s, you may be able to still run it today on z/OS, because you can probably run the 1970s-era emulator.

From what I’ve gathered, the IRS was using IBM’s 7074 emulator in production under z/OS to run some very old applications written in 7074 assembly-they might have finally stopped by now, but they were still doing it as recently as 5 years ago.

Fun fact: z/OS is now emulated on Red Hat Linux nowadays for "new" deployments.

What exactly do you mean by that ? Are you talking about an IBM emulation product that runs on RH Linux ?

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