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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.