/sys$common/syshlp/helplib.hlb FORTRAN, Format Specifiers, BN  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  (Blank Control Editing)

  Causes embedded and trailing blanks to be ignored within a numeric
  input field.  Leading blanks are always ignored, and an all blank
  field is always treated as zero.  The BN descriptor must precede
  all field descriptors to which it applies.

  It affects all following I, O, Z, F, E, D, and G editing (in the
  same FORMAT statement) during the execution of an output statement.

  If the OPEN statement is not used or it is used and BLANK='ZERO' is
  specified, blanks are converted to zeros.  If the OPEN statement is
  used and either BLANK='NULL' is specified or the BLANK keyword is
  omitted, blanks are ignored.