D=NATURAL (OpenVMS Alpha and OpenVMS I64)
D=VAX (OpenVMS VAX)
Controls the default alignment rules. Note that specifying the
ALIGN attribute overrides any value that you previously
specified for this qualifier.
You can specify the following values for keyword:
NATURAL
Uses natural alignment when positioning record fields or
array components.
Natural alignment is when a record field or an array component is
positioned on a boundary based on its size. For example, 32-bit
integers are aligned on the nearest 32-bit boundary.
Default on OpenVMS Alpha and OpenVMS I64 systems.
In prior versions, the compiler spelled this keyword Alpha_AXP.
It is still accepted for upward compatability.
VAX
Uses byte alignment when positioning record fields or array
components. Record fields or array components larger than 32-bits
are positioned on the nearest byte boundary.
Default on OpenVMS VAX systems.
On OpenVMS VAX systems, when you specify a value of NATURAL,
automatic variables are aligned on longword boundaries instead
of quadword boundaries. This occurs because the largest
allowable alignment for the stack is longword alignment.