Compiler_Mode_Macros

 The following predefined macros are defined as 1 if the
 corresponding compiler mode is selected (Otherwise, they are
 undefined):

 __DECC_MODE_STRICT     !  /STANDARD=ANSI89
 __DECC_MODE_RELAXED    !  /STANDARD=RELAXED
 __DECC_MODE_VAXC       !  /STANDARD=VAXC
 __DECC_MODE_COMMON     !  /STANDARD=COMMON
 __STDC__               !  /STANDARD=ANSI89, /STANDARD=RELAXED
 __STDC_VERSION__       !  /STANDARD=ISOC94
 __MS                   !  /STANDARD=MS