isalnum() ctype Macro (ctype.h) isalnum() Check if a character is a number or letter #include <ctype.h> int isalnum(c) int c; isalnum tests whether the argument c is alphanumeric (0-9, A-Z, or a-z). It returns a number other than zero if c is of the desired type, and zero if it is not. isalnum assumes that c is an ASCII character or EOF. ***** Example ***** For an example of how to use this macro, see the entry for ctype. ***** See Also ***** ASCII, ctype COHERENT Lexicon Page 1