The FIELD statement dynamically associates string variables with  portions
  of  an  I/O  buffer.   FIELD  statements  do not move data.  Instead, they
  permit direct access through string variables to sections of  a  specified
  I/O buffer.

  Examples

  FIELD #1%, 40% AS WHOLE_FIELD$
  FIELD #1%, 10% AS A$, 10% AS B$, 10% AS C$, 10% AS D$