Q42729: Direct Memory Addressing

Article: Q42729
Product(s): See article
Version(s): 4.x 5.00 5.10 | 5.10
Operating System(s): MS-DOS | OS/2
Keyword(s): ENDUSER | | mspl13_masm
Last Modified: 24-APR-1989

Question:

When I try to do a direct memory operation with the instruction MOV
AX,[1000], the Macro Assembler generates a move instruction with the
immediate value of 1000 rather than a direct memory access of the
location 1000. How can I do a direct memory access instruction?

Response:

A segment register must be specified for a direct memory operand that
contains a constant with no label, as in the following

   MOV AX,DS:[1000]

This example will not insert a segment override prefix into the
assemble code because the instruction uses the DS register by default.
Use of any segment register other than the default register would
insert the override prefix.

For more information, see Section 14.3.1 on Direct Memory Operands,
Page 276 in the MASM 5.10 programmer's guide.

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