VMS Help FORTRAN, Format Specifiers, BZ  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  (Blank Control Editing)

  Causes embedded and trailing blanks to be treated as zeros within a
  numeric input field.  (Leading blanks are always ignored.) The BZ
  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, nonleading blanks are treated as zeros.

  An all blank field is always treated as zero.