The stub of push() should look like this:
   void Stack::push(const Item& it) {
Note that when the stack is empty, mySize is 0: when the stack contains 1 item, mySize is 1; when the stack contains 2 items, mySize is 2; and so on. Put differently, mySize always contains the index of myArray where we want push() to store its item!

The push(it) method should thus behave as follows:

  1. Store it in the entry of myArray whose index is mySize.
  2. Add 1 to mySize.