How can I define . (decimal, not float) properly in an array?
You ARE defining it correctly. At least as correctly as you can when you want to store a non-integer value in an integer array. Therefore, there must be some other problem.
It doesn't make sense to me to go from '8' to '9' to '.'. But, if that IS what you want, why isn't the array of possible values of type char, and why doesn't it contain '0', '1', '2', ... '8', '9', '.'?