breastle screen for HLA Adventure Need help designing one 857

Randall Hyde

I'm not the one inventing these standards; I'm just trying to explain how they work in relation to each other. :) But if you feel someone might still be confused about it, I can take yet another stab at it:

IBM Codepage 437, as a whole, and as far as I know, is not defined in any standard issued by ANSI. But since IBM Codepage 437 builds upon ASCII-1968, the code positions 0...127 on it are defined in an ANSI standard (namely, ANSI X3.4-1968, which defines what ASCII is) - even though the other half - the new 8-bit code positions from 128 to 255 - aren't. So you can view it both ways, depending on which range of character codes you look. The first half of the character set is covered by an ANSI standard (except for the additional glyphs in the control code range), the second half isn't.

Hence, IBM Codepage 437 incorporates one of the ANSI standards for character codes (namely, ANSI X3.4-1968 - or simply "ASCII" for us mere mortals), being a superset of it, but IBM Codepage 437 is still not an ANSI standard itself, since no ANSI standard defines the 8-bit code positions (128...255) the way they are defined in IBM Codepage 437.

That's actually useful knowledge since it means you can bring ASCII text to an IBM Codepage 437 environment and expect it to work without any conversions. Then again, this concept isn't itself anything particularly exciting or unique: many other 8-bit character sets are based on ASCII the same way - they retain a more or less verbatim copy of ASCII in the first half of the set, and define new characters in the second half. (That's only reasonable, since it allows for easy backwards compatibility with old ASCII-only documents and environments.)

In the end, the gist of what IBM Codepage 437 is all about isn't the old, 7-bit ASCII-compatible part of it, but the new 8-bit characters in the range 128...255. (This part of the thread originally branched off from a picture that used the Codepage 437 characters in the 128...255 range. Therefore, it was definitely not "ASCII", and since no ANSI standard defines the 128...255 range for IBM Codepage 437, it was not "ANSI", either in any sense of the word. You didn't make any of these claims; I'm just pointing them out here for clarity.)

No-one has tried to change the "basic argument", just enliven it with new spin-off peripheral arguments. :)

Why do you cling on the "basic argument" so hard, as if I would somehow have tried to dispute that! - when we have no argument whatsoever in there? :) In case you haven't noticed, I have been talking about two other arguable details in the last couple of messages - not about your "basic argument". :)

I was just pointing out a possible misunderstanding which your original choice of articles seemed to imply. If there is no misunderstanding for your part, that's fine with me, but someone might still have got a wrong idea from your original message, so it seemed to warrant a further discussion of the details - which I gave.

Again, whatever false statements "Annie" made was never the issue in my followups - you already had that covered. I was pointing out other things. :)

I don't know which groups you read - and that's exactly why I explicitly gave you a choice of not adhering to whatever I happen to set in the "Followup-to" header. (I find this practice more polite than just brutally slashing off groups directly from the "Newsgroups" line, but I'm old-fashioned that way.)

Then again, if I see a discussion drifting into off-topicness, and someone takes the trouble of limiting the followups into a more proper set of groups (or even only to a single group), I tend to follow the discussion there, instead of insisting that the off-topic discussion should be done to rest in "my" group, no matter what. (I'm not exactly sure how much relevance semantic semi-historical ponderings about character encoding issues have in alt.lang.asm, but if you're a regular in that group, maybe you know better.)

-- znark