#define UPPERCASE_LETTERS "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
#define LETTERS LOWERCASE_LETTERS UPPERCASE_LETTERS
#define ALPHANUMERICAL LETTERS DIGITS
+#define HEXDIGITS DIGITS "abcdefABCDEF"
#define streq(a,b) (strcmp((a),(b)) == 0)
#define strneq(a, b, n) (strncmp((a), (b), (n)) == 0)