Defining the range of the area

On CSRIRP, you define the range of the area to be referenced:

low_address identifies the lowest addressed byte in the range.
size identifies the size, in bytes, of the range.

When reference is forward, low_address identifies the first element that the program can reference in the range. When reference is backward, low_address identifies the last element that the program can reference in the range: reference proceeds from the high-address end in the range towards low_address.

The following parameters define the lowest address and the size of ARRAY1, a 1024-by-1024 array that consists of 8-byte elements. ARRAY1(1,1) identifies the element in the first row and the first column.

CSRIRP  with low_address of ARRAY1(1,1)
             size of 1024*1024*8 bytes

When a gap exists, define the range according to the following rules:

If direction is forward, low_address must be the first data element in a reference unit.
If direction is backward, the value you use for size must be such that the first data element the program references is the high-address end of a reference unit.

These two rules are described and illustrated in Using CSRIRP when a gap exists.