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  Syntax:   OPTION OFFSET:offsettype
 
  See also: MASM 5.1 Compatibility, OFFSET, GROUP, SEGMENT,
            FLAT memory model
 
  Description:
 
     Controls whether the OFFSET operator returns offsets relative to
     the current segment or group. OPTION OFFSET:GROUP causes OFFSET
     to return a group-relative offset if the label is in a segment
     that is part of a group. OPTION OFFSET:SEGMENT causes OFFSET
     to return a segment-relative offset. OPTION OFFSET:GROUP is the
     default.
 
     The FLAT option causes fixups to be relative to the FLAT group.
 
     OPTION M510 sets OPTION OFFSET:GROUP if a .MODEL directive has been
     used and OPTION OFFSET:SEGMENT otherwise. With previous versions of
     the assembler, the OFFSET type was SEGMENT with complete segment
     directives and GROUP with simplified segment directives.
 
     The <offsettype> can be GROUP, SEGMENT, or FLAT.
 
     When programming for the 80386 or 80486, the size of an OFFSET expression
     can be 2 bytes for a symbol in a USE16 segment, or 4 bytes for a symbol
     in a USE32 or FLAT segment. With OPTION M510, you can use a 32-bit
     OFFSET expression in a 16-bit context. Without OPTION M510, you must
     use the LOWWORD operator to convert the offset size.
 
     With no .MODEL, MASM 5.1 computes offsets from the start of the segment,
     whereas MASM 6.1 computes offsets from the start of the group. (With
     .MODEL, MASM 5.1 also computes offsets from the start of the group.)
 
     To force MASM 6.1 to emulate 5.1 behavior, specify either OFFSET:SEGMENT
     or OPTION M510. Both directives cause the assembler to compute offsets
     relative to the segment if you do not include .MODEL.
 
     To selectively enable MASM 6.1 behavior, place the directive OPTION
     OFFSET:GROUP after OPTION M510. In this case, you should ensure each
     OFFSET statement has a segment override where appropriate.
 
     When not in compatibility mode, the OPTION OFFSET directive determines
     whether the SEG operator returns a value relative to the group or
     segment. With OPTION M510, SEG is always segment-relative by default,
     regardless of the current value of OPTION OFFSET.
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