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Q69540: JMP to a Far Address Lists Segment First in Listing File

Article: Q69540
Product(s): Microsoft Macro Assembler
Version(s): 6.0,6.0a,6.0b,6.1,6.11,6.1a
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, 6.1, 6.1a, 6.11 
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SUMMARY
=======

In the Macro Assembler (MASM) version 6.0 and later, the opcode for a JMP to a
far address is shown in the listing file with the segment first, then the
offset. In the actual .OBJ file, the address is stored in the reversed order
(offset then segment).

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

The following is the encoding for the JMP instruction from the listing (.LST)
file generated from the sample program below:

  0000  EA ---- 0000 E            jmp faddr

The above address for faddr (---- 0000) is displayed with the segment listed
first (----), then the offset(0000). Because the linker resolves this address at
link time, the actual segment and offset is not known at assemble time, and is
not listed in this file.

If you then look at the actual .OBJ or .EXE file produced by the above code (by
using CodeView, for example), you will see the offset first in the file, then
the segment.

This is expected behavior with MASM version 6.0 and later and is designed to make
the segment:offset more readable. This is different from MASM version 5.1, which
displayed the addresses for far JMP instructions in the reversed (offset then
segment) form.

Sample Code
-----------

  ; Assemble options needed: /c /Fl

  .MODEL large
  EXTRN faddr:far

  .CODE
     jmp faddr
  END

Additional query words: kbinf 6.00 6.00a 6.00b 6.10 6.10a jump object

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Keywords          :  
Technology        : kbMASMsearch kbAudDeveloper kbMASM600 kbMASM610 kbMASM611 kbMASM610a kbMASM600a kbMASM600b
Version           : :6.0,6.0a,6.0b,6.1,6.11,6.1a

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