TOLOWER
if (!ISALPHA(c) || (TOLOWER(c) != 'o' && TOLOWER(c) != 'i')) {
*out = (TOLOWER(c) == 'o') ? 1 : 0;
c = TOLOWER(c);
c1 = TOLOWER(c1) - 'a';
c2 = TOLOWER(c2) - 'a';