Character testing functions

The definitions of printing character and control character have been generalized from ASCII.

Note that none of these functions returns a nonzero value (true) for the argument value EOF.

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• The isalnum function
• The isalpha function
• The iscntrl function
• The isdigit function
• The isgraph function
• The islower function
• The isprint function
• The ispunct function
• The isspace function
• The isupper function
• The isxdigit function