cDEC$ PACK

  Specifies the memory starting addresses of derived-type items.  It
  takes the following form:

  cDEC$ PACK:[{1 | 2 | 4}]

    c        Is one of the following: C (or c), !, or *.

  Items of derived types and record structures are aligned in memory
  on the smaller of two sizes:  the size of the type of the item, or
  the current alignment setting.  The current alignment setting can
  be 1, 2, 4, or 8 bytes.  The default initial setting is 8 bytes
  (unless a compiler option specifies otherwise).  By reducing the
  alignment setting, you can pack variables closer together in
  memory.

  The PACK directive lets you control the packing of derived-type or
  record structure items inside your program by overriding the
  current memory alignment setting.

  For example, if CDEC$ PACK:1 is specified, all variables begin at
  the next available byte, whether odd or even.  Although this
  slightly increases access time, no memory space is wasted.  If
  CDEC$ PACK:4 is specified, INTEGER(1), LOGICAL(1), and all
  character variables begin at the next available byte, whether odd
  or even.  INTEGER(2) and LOGICAL(2) begin on the next even byte;
  all other variables begin on 4-byte boundaries.

  If the PACK directive is specified without a number, packing
  reverts to the compiler option setting (if any), or the default
  setting of 8.

  The directive can appear anywhere in a program before the
  derived-type definition or record structure definition.  It cannot
  appear inside a derived-type or record structure definition.

  For compatibility, !MS$PACK can be used in place of cDEC$ PACK.

  Examples:

  Consider the following:

  ! Use 4-byte packing for this derived type
  ! Note PACK is used outside of the derived-type definition
  !DEC$ PACK:4
  TYPE pair
    INTEGER a, b
  END TYPE
  ! revert to default or compiler option
  !DEC$ PACK: