The isalnum() function shall test whether c is a character
of class alpha or digit in the program's
current locale; see the Base Definitions volume of IEEE Std 1003.1-2001,
The c argument is an int, the value of which the application
shall ensure is representable as an unsigned
char or equal to the value of the macro EOF. If the argument has
any other value, the behavior is undefined.
The isalnum() function shall return non-zero if c is an
alphanumeric character; otherwise, it shall return 0.
No errors are defined.
The following sections are informative.
To ensure applications portability, especially across natural languages,
only this function and those listed in the SEE ALSO
section should be used for character classification.
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at