The elements of an array form a sequence known as the array element
  order.  The position of an element in this sequence is its
  subscript order value.

  The elements of an array are stored as a linear sequence of values.
  A one-dimensional array is stored with its first element in the
  first storage location and its last element in the last storage
  location of the sequence.  A multidimensional array is stored so
  that the leftmost subscripts vary most rapidly.  This is called the
  order of subscript progression.

  In an array section, the subscript order of the elements is their
  order within the section itself.  For example, if an array is
  declared as B(20), the section B(4:19:4) consists of elements B(4),
  B(8), B(12), and B(16).  The subscript order value of B(4) in the
  array section is 1; the subscript order value of B(12) in the
  section is 3.