Where to draw the line with IBM mainframe questions?

Question

Due to the extreme backward compatibility of IBM mainframes, I think it can be harder to tell than for most other systems where to draw the line between retrocomputing questions and non-retrocomputing questions.

If the question is about something long-discontinued – e.g. OS/VS1 – I think it is clearly on-topic.

If the question is about newer features of z/OS – e.g. AMODE 64 – clearly off-topic.

But I was thinking about asking a question about how VTAM handles ASCII-EBCDIC conversion. And that seems a bit of a grey area, because 2020s VTAM likely does it in the exact same way as 1970s VTAM does it. I suppose by expanding the scope to include more clearly historical systems (e.g. BTAM, QTAM, TCAM) and asking if they did it any differently, might put it more clearly in the retrocomputing category.

Still, I do think there is more of a grey area with IBM mainframes than with most other systems. No other platform is still capable of running 1960s/1970s era software without using an emulator. Compare that to e.g. Windows – with Windows 11, 32-bit Windows has been discontinued, and with it all native support for 16-bit apps (although Microsoft still officially supports 16-bit software under 32-bit Windows 10, which is due to be supported until next year–possibly longer for paying customer); Apple dropped the Classic Environment all the way back in 2007 (release of OS X 10.5) or 2009 (final desupport of OS X 10.4).

Answer 1

As I said in the comments, I don't think any line needs to be drawn at the present time. We are not being overwhelmed with System/360 questions. Thus, I think we can accept that we will review each post on its retrocomputing merits.

If it turns out we're getting a lot of questions about modern aspects of the long-lived architecture, we can revisit the matter. Until then, ask away.

For the matter of "how VTAM handles ASCII-EBCDIC conversion", I suggest using the past tense to set the appropriate mood for the question :-)

Answer 2

Would't have thought about this as a grey area. But sure, you make a valid point.

Basic On-Topic decisions are not only about age and out-of-production (*1) but a soft membrane tethered also at obscurity and what I would call coolness in lack of a better word.

Plus, and that's maybe most important, intention/purpose of a question.

I would think your question may tick all of these requirement. Beside asking for origins, which always works, it's a software question, which nicely can be tied to older eras. VTAM was introduced ca. 1976 (after being vapourware for some time), so one can nicely ask for 1976 VTAM - or better even for BTAM, which had to solve the same issue, even more direct :))

So go ahead and ask.

---

In case of IBM mainframes it may be rather relevant to distinguish between

• OS,
• Architecture, and
• Implementation/specific family and model.

In case of mainframes this is often blurred into using one term, but meaning some of the other. For example people like to say z/OS when in fact talking about z/architecture or a specific model as if it would be clear. That isn't. So make sure what exactly you're asking about. AMODE 64 being a nice example. While z/OS supports it native, it's not an OS feature buy a hardware one. The same Hardware can run other software that uses this feature.

Being introduced in ca. 2000 I would think questions about compatibility / complications with AMODE 64 could as well qualify. Kinda like asking about Y2K problems 20 years later :))

---

On a more general level I could not think of many borderline /360ff questions. Either it's really about modern API (or instruction) and clearly off topic, or more likely something that is around since 40+ years

---

Now, for the translation part, you may as well look at BTAM, as VTAM is more of an additional abstraction layer, hiding more of the nitty gritty details. In BTAM one can still direct access the translate tables (Macro TRNSLATE) for example RASA/SASA for 3270 ASCII/EBCDIC translation. But you might be surprised how much is stil done 'by hand'.

Thinking of it, a generic question about VTAM and NL handling might be also one that is way to broad for a good answer, as it not only needs to differentiate how a terminal is accessed, but also via what configuration. Translation may happen as late as in the terminal controller or as early as within the mainframe ... that is if needed at all.

---

*1 - In the end the main reason for this cut off is to redirect today's questions into SE areas which are more appropriate.