Aaron Larson's comments

[<masinter@parc.xerox.com>]

Re "I would put the description of standard char after the description
of base character": "base character" is easier to define after the
introduction of arrays and element-type upgrading. What is or isn't a
standard-char is intrinsic: you can tell looking at the character
whether it is a standard-char.  However, whether something is a
base-character or not really depends on the implementations
representations of strings. In implementations with a uniform string
representation, *all* characters are base-character, and there are no
"extended characters", even if the character space is large.

So it makes sense to define standard-char first, and then introduce
base-character as "those characters that can be stored in strings like
standard-char".