When I was a child, my German teacher (in a non-German speaking country) told us that the typed form for the letter "ß" in use in mainframes at that time was "ss" instead of "sz" (the spoken form of that glyph as it's composed of a "ſ" and a "ȝ") because the SS was the largest customer of punched cards on IBM's Tabulating Machines outside the USA at that time.
Sorry, but that's as much crap as there can be. Well, not about the digraphs used instead of the ligature based letter, but the reasoning (*1).
To start with, ligatures of
sz look quite close and the modern
ß glyph is in fact based on
ss. Next, the usage of
sz in one and the same word nor the use of
ß instead was consistent in German until way into the 19th century. It was people like the Brothers Grimm and their 30+ issue Deutsches Wörterbuch (German Dictionary) that helped to standardized spelling after the 1850s.
It was in fact their work that favoured the
sz replacement for
ß, mostly due the fact that it helped to distinguish words 'downgraded' from such already containing a double-s.
While the whole point of reverting already became an minor issue with the early typewriters (only such not made for German), it took center stage with the advent of teletypes in the 1920s. Here the all official use (e.g. army, post office) used
sz for the very same reason. In common text
ss was more common.
Thus, a common person will have Spass, while the army has Spasz :))
And that's essentially the state up to today ... well, plus a of course that piece of Nazi-history everyone waits for:
One of their improvements for 'purity' was to get rid of any German script, which of course means dropping all additional letters (like we used to have two different
s - Greek and English BTW as well). At that point Hitler intervened and ordered the
ß to be kept. Which ofc. was only a lower case one, so capitalisation stayed with
SS for next to everything published - all like before.
SSin case of Mainframes is a rather simple one: here were no mainframes before and during any time IBM might have wanted to please the Nazis at all. There were only punch card machines, which had no software that dictated the use or not use of certain letters - even less of lower case, which were not a thing back then.
Also, when mainframes became usable much later on, Basic charsets use was all about uppercase (English) Latin letters. And while lower case (and German Ä/Ö/Ü) were added by the time mainframes emerged, noone was really using them (*2). So neither
ß and even less a back then not invented upper case variant was used - or replaced. After all, replacement would have meant that they can be entered in the first place. So
SSis the only usage here ... of course unless it was about storing any processing of teletype messages :))
but there is no literature that either he nor I can find that (dis)proves the statement of my German teacher over ½ century ago...
Wiki got a whole page about. But you could as well listen to this fine English chap.
P.S. Asking here on https://retrocomputing.stackexchange.com/ and not asking over on https://history.stackexchange.com/ nor https://german.stackexchange.com/ as we're just 2 nerds working in the IT industry that are just looking for logic whereas on the other 2 sites, this might be a sensitive subject.
Well, it would be way better handled over there and I'll be voting for moving, as it is not IT related at all.
*1 - Including the part abut SS being the biggest customer. Germany may have been the single biggest IBM market outside the US. But then again Germany had a few large companies using punch cards. If you try you may come up with many names - including Ford or General Motors :))
*2 - Well, we for example only added lower case to mask text in the early 1980s. Lower case as input was't added until ca. 2000.