/ALPHA_AXP (Default on Alpha and IA64 systems)

   There are many things that depend on this qualifier:

   o The size of certain data types (HARDWARE_ADDRESS, INTEGER_HW,
     HARDWARE_INTEGER, POINTER_HW) is 8 bytes if /ALPHA_AXP is specified
     and 4 bytes otherwise.

   o Bitfields can have 64 bits if /ALPHA_AXP is specified and only 32 bits
     otherwise.

   o BASIC defines the data type HUGE as BASIC$HFLOAT_AXP if /ALPHA_AXP is
     specified and as HFLOAT otherwise and HUGE_COMPLEX as
     BASIC$H_FLOATING_COMPLEX_AXP if /ALPHA_AXP is specified and as
     BASIC$H_FLOATING_COMPLEX otherwise.

   o CC writes alignment pragmas to the output file only if /ALPHA_AXP is
     specified.

   o CC generates 64-bit pointers only if /ALPHA_AXP is specified.

   o CC generates QUADWORD datatypes as __int64 if /ALPHA_AXP is specified
     and as int[2] otherwise.

   o Also see /C_DEVELOPMENT and /VMS_DEVELOPMENT.