I

• Index:
  Ordered sequence of elements (objects) in an array. The array index is zero-based, meaning that the first item is stored at 0 (zero), the second is 1 (one), and the third is 3, etc. See Array. 
• Integer:
  Numeric values that can be part of calculations; for example, a purchase price is an integer that can be used to calculate the value of another data field, such as total amount. Integers are usually  variables, but they can be constants that are the same value during processing but are used in calculations. A purchase price can be a variable because it can be recalculated then its new value replaces the original purchase price. A state tax rate or discount rate are constants.