Re: Difference between EM QUAD and EM SPACE

From: Kenneth Whistler (kenw@sybase.com)
Date: Fri Jul 07 2000 - 19:03:13 EDT


Patrick Andries asked:

> Could someone explain to me what is the difference between an EM QUAD and an
> EM SPACE ?

Effectively, there is none.

The encoding of both was the result of an unfortunate misunderstanding during
the development of Unicode 1.0.

The EM QUAD and EN QUAD derive from XCCS 1980 357/055 em quad and 357/054 en quad,
respectively.

The EM SPACE and EN SPACE were added to fill out the set of fixed-width spaces,
which themselves were mostly derived from XCCS 1980.

During review for Unicode 1.0, no one caught the fact that this was a duplication.

Since Unicode 2.0, the EM QUAD and EN QUAD have been listed as canonical equivalents
of EM SPACE and EN SPACE, respectively. That is effectively a way of saying that
those are, unfortunately, duplicate characters that made their way into the
standard in error.

--Ken



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