Re: GCGID for U+03B8

From: Markus Scherer (
Date: Fri Oct 11 2002 - 13:02:25 EDT

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    Doug Ewell wrote:

    > What is the correct IBM GCGID value for U+03B8 GREEK SMALL LETTER THETA?
    > Is it GT610000 or GT610002?

    I have an internal document that shows
    GT610000 Theta Small - (see GT610001, GT610002) U00003B8 GREEK SMALL LETTER THETA
    GT610001 Theta Small (Open Form) - (resembles SA50) U00003D1 GREEK THETA SYMBOL
    GT610002 Theta Small (Closed Form)
    SA500000 Curly Theta Symbol - (resembles GT610001)

    The last digit in the GCGID is 0 for the generic GCGID for which any glyph can be chosen. A non-zero digit selects a specific, registered glyph - quite similar to the Ideographic Variation Selectors.

    Generally, the first four characters in the GCGID define the abstract character, and the other four (if present) specify appearance.

    (No, I am not an expert in GCGIDs; I am looking this definition up in the Character Data Representation Architecture (CDRA) Reference. See

    > The Unicode 1.1 lists (UNICHP6B.TXT and UNICHP6C.TXT) are inconsistent
    > in this regard. Some entries, even within the same file, show GT610000
    > while others show GT610002. The tables printed in Unicode 1.0 book are
    > the same.

    For both GT610000 and GT610002 the first internal document shows a glyph like the one for U+03b8 in the Unicode 3.0 book.
    For GT610001 and SA500000 it shows a glyph like TUS 3.0 for U+03d1.

    > IBM has a Web page containing many PDF charts of code pages, and they
    > have the same problem: some show one GCGID for U+03B8, others show the
    > other one.
    > I suppose this might have had something to do with confusion over U+03D1
    > GREEK THETA SYMBOL, but that character (a glyph variant of U+03B8) has
    > been in Unicode since 1.0. Was there some dispute at that time over the
    > preferred glyphs for U+03B8 and U+03D1? I remember that they were
    > swapped in Unicode at one point. Was the inconsistency in GCGID a
    > precursor to the decision to swap glyphs?

    Well, these GCGIDs are just glyph variants, too.

    > Any ideas? (It's probably best not to ask why I am paying attention to
    > GCGIDs in the first place.)

    I hope this helps - best regards,

    Opinions expressed here may not reflect my company's positions unless otherwise noted.

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