You could just create a variable (for example: int size = 0).

Then everytime you insert an item into your array, increment the size variable:

size++;

then at the end of your code output the size variable:
cout << size << endl;

Ya only two choices ....
1. Keep track of insertion and deletion as said above.
2. OR Count all over again

There is no direct way to know how much content you have in an array, versus the size of the array. Except, of course, when your array is of type char and you are using it properly for strings.

Consider an array of integers. Just because some element has a value 0, does that make it an unused element? Zero might well be a valid data value.

Hansels's suggestion to keep track of data as it's entered, and pass that value around along with the array, is about the best general solution.

If I understand what you're doing, when the data is in a string might be a good time to capture the length of the data ( str.size() )

Sounds like an awful lot of work just to reverse the array. Why convert (copy?) from the char array to an int array? Char's are, after all, just small integers.

Have you tried to use a vector?

You can only get the capacity of the array by this:

Here is the problem statement for which I need to make this program. I hope this clarifies stuff

How are these integers input? Do you read them from a file?
Since you are storing them to array of char, you can, to a small degree, initially treat them as strings, thus use the strlen( ) function to find how many digits were entered.

Don't forget you have to check for a positive/negative sign.

You should perhaps read those two value in two strings variables. And then write your own add function which would find there sum.

you can simply use a char array to store the integer array and then use strlen(array) function of string.h lib to get the length,
or you can also break the integer array in to units by using modulus operator and division.