Should be:Code:if (surname[1] != 1 || surname[1] != 2 || surname[1] != 3 || surname[1] != 4 || surname[1] != 5 || surname[1] != 6 || surname[1] != 0){ surname[1] = '0'; }Code:if (surname[1] != '1' || surname[1] != '2' || surname[1] != '3' || surname[1] != '4' || surname[1] != '5' || surname[1] != '6' || surname[1] != '0'){ surname[1] = '0'; }