Index Variables
Arrays are zero-based, that is, the first element is indexed with the
number 0. If an array has n
components, then n is the
length of the array and its components are referenced using
integer indices from 0 to n - 1, inclusive.
An array index variable holds an index entry for the array and is used
to retrieve a specific array component. For example:
ArrayVariable[IndexVariable]=value
The Index Variables selection box lists all the variables contained in the opened script that are of the type that can be used as an index variable. Use this selection box to paste one of these variables into an expression as an index variable if it is appropriate for such in your script.