Re:Code Page 437 Refuses to Die
by jameshart on Sunday May 08, 2016 @05:59PM
(#11656155)
That's fair, and thanks for digging up those actual standards - they are indeed not easy to find these days. I think though that tends to be the standard speaking to the intended usage of the ASCII codes, more than it does to an attempt to standardize behavior of all input and output devices. It's more a suggestion that some equipment might choose to use backspace for diacritics, and some might separately effect X and Y movement, but others might not. Certainly in practice terminals have always exposed their different capabilities by giving special terminal code meanings to ASCII sequences, and, when terminal capability negotiation was not an option (e.g. in specifying a file format or defining how to separate SMTP headers) ASCII users have made their own standards for these things (I guess this is the sort of 'agreement' the standard alludes to).
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Yes, the ‘dual use’ characters were define at the request of European delegations and the language makes it clear that it was expected that English-language terminals would continue to have " look like " and not ¨ and so on. ASCII was defined before video terminals were developed, so no one thought overstriking was remarkable. As it turned out, non-English European language versions ended up not generally using overstrikes anyway, but redefined the ‘national use’ characters #$@[\]{|} instead, which unfortunately did lead to ambiguity.