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Q75276: OFFSET Always Returns the END of a Segment Name

Article: Q75276
Product(s): Microsoft Macro Assembler
Version(s): MS-DOS:6.0,6.0a,6.0b
Operating System(s): 
Keyword(s): 
Last Modified: 06-MAY-2001

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The information in this article applies to:

- Microsoft Macro Assembler (MASM), versions 6.0, 6.0a, 6.0b 
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SUMMARY
=======

With the release of the Microsoft Macro Assembler (MASM) version 6.0, the OFFSET
operator applied to a segment name now returns the end of the segment relative
to the start of the segment.

This is a change from MASM versions 5.x where "OFFSET segname" will return the
beginning of the segment if it is declared class 'CODE'. If the segment is
declared of some other class, "OFFSET segname" will return either the end of the
segment relative to the beginning of a segment if full segment definitions are
used, or the end of the segment relative to the start of the group the segment
was contained in if simplified directives are used.

MORE INFORMATION
================

As part of defining the BNF for MASM 6.0, an attempt was made to remove any
ambiguities in the language. This is one of those changes. In MASM 6.0, "OFFSET
segname" will always return the end of the segment unless an explicit group or
segment override is provided.

For example,

  _DATA segment  para PUBLIC 'data'
        db    dup 100 ( )
  _DATA ends

  STACK segment  para STACK 'stack'
        db    dup 100 (?)
  STACK ends

  DGROUP group _DATA, STACK

  TEXT  segment para 'CODE'
        ORG   100

        mov   sp, OFFSET STACK          ; mov's 100 into sp
        mov   sp, OFFSET DGROUP:STACK   ; mov's 200 into sp

        mov   ax, OFFSET TEXT           ; mov's size of TEXT into AX
        mov   ax, OFFSET TEXT:0         ; mov's start of TEXT into AX

For more information on the OFFSET operator, see the online Help.

Additional query words: kbinf 6.00 6.00a 6.00b

======================================================================
Keywords          :  
Technology        : kbMASMsearch kbAudDeveloper kbMASM600 kbMASM600a kbMASM600b
Version           : MS-DOS:6.0,6.0a,6.0b

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