'10' = Multi-character constant. Throws a compiler warning but still works.
Character literals are required, by the standard, to be 1 character in length (not empty, either). '10' is invalid and should be a compiler error, not just a warning.
The first element in the array is inventory[0].
This is because it is equivalent to *(inventory+0).
An array in some ways is equivalent to a pointer to the first element.