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7.5.2 Charset selection  As it is set up now, the program
assumes that the input file is coded using 8-bit ISO 8859-1
code, also known as Latin-1 character set, unless it is compiled
for MS-DOS, in which case it uses the character set of the IBM-
PC. (GNU ptx is not known to work on smaller MS-DOS machines
anymore.) Compared to 7-bit ASCII, the set of characters which
are letters is different; this alters the behavior of regular
expression matching. Thus, the default regular expression for a
keyword allows foreign or diacriticized letters. Keyword
sorting, however, is still crude; it obeys the underlying
character set ordering quite blindly.  Fold lower case letters
to upper case for sorting.