Indicates how blanks are interpreted in a file.  It takes the
  following form:

  BLANK = blnk

  blnk  Is a character expression with one of the following
        values:

  'NULL'  Ignore all blanks in a numeric field (unless the field
          is all blanks, in which case treat blanks as zero).
  'ZERO'  Treat all blanks other than leading blanks as zeros.

  The default is 'NULL' (for explicitly OPENed files, preconnected
  files, and internal files).

  If the BN or BZ edit descriptors are specified for a formatted
  input statement, they supersede the default interpretation of
  blanks.