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  Syntax:   ASSUME segregister:seglocation [, segregister:seglocation]...
 
            ASSUME dataregister:qualifiedtype
            [, dataregister:qualifiedtype]...
 
            ASSUME register:ERROR [, register:ERROR]...
 
            ASSUME [register:]NOTHING [, register:NOTHING]...
 
  See also: SEGMENT, GROUP, .MODEL, SEG, Simplified Segment Directives,
            Complete Segment Directives
 
  Description:
 
     A general-purpose directive that allows the assembler to
     determine offsets, select the correct segment register, and verify
     certain register use assumptions at assembly.
 
     The "ASSUME segregister:seglocation" syntax is used to inform the
     assembler of the current value of <segregister>. The assembler
     uses this information to calculate offsets correctly and to guard
     against segment selection errors. This directive does not generate
     code to change the value of <segregister>. The ASSUME directive is
     not necessary for the CS register, since CS is assumed to the
     current segment or group automatically. The <seglocation> can be any
     segment or group name, or an equivalent expression.
 
     The "ASSUME dataregister:type" syntax informs the assembler that
     <dataregister> is subject to the constraints of <type>. If an
     assumed register is used incorrectly, the assembler generates an
     error. The <type> parameter must be the same size as
     <dataregister>.
 
       ASSUME   bx:WORD
       mov      ax, [bx]        ;Error--cannot dereference non-pointer
       ASSUME   bx:PTR WORD
       mov      [bx], 10h       ;Assumes operand size is WORD
       mov      [bx], al        ;Error--cannot move byte into word memory
       ASSUME   al:WORD         ;Error--al is only byte-sized
       ASSUME   bx:BYTE         ;Error--bx is word-sized
 
       The ASSUME directive can include ERROR, FLAT, or register:type.
       MASM 6.1 issues a warning when you specify ASSUME values for
       CS other than the current segment or group.
 
     The "ASSUME register:ERROR" syntax causes the assembler to
     generate an error if <register> is later used explictly or
     implicitly. The OPATTR, .TYPE, and TYPE directives do not cause
     errors when referring to registers assumed to ERROR.
 
     The "ASSUME register:NOTHING" syntax causes the assembler to
     remove all assumptions about <register>. ASSUME NOTHING removes
     all assumptions about all registers.
 
     Use an ASSUME statement each time you load a known value into a
     segment register. Although not required, the ASSUME directive
     helps the assembler safeguard against segment selection errors and
     determine offsets. You may need to use instructions to initialize
     segment registers properly at run time.
 
     If you use the ASSUME directive to set assumptions about a data
     register, it will override any assumptions for its subregisters.
     For example, ASSUME EDX:DGROUP will override assumptions for DL,
     DH, and DX.
 
     Parameter      Description
 
     segregister    CS, DS, ES, FS, GS, or SS. The assembler
                    automatically maintains assumptions for the CS
                    segment register.
 
     seglocation    A segment address, another segment register, a
                    group, or FLAT. You can find the segment address
                    of a label by using the SEG operator. FLAT is
                    the label of the single FLAT segment.
 
     dataregister   Any byte, word, or 32-bit register.
 
     qualifiedtype  Any qualified type that will fit in
                    <dataregister>.
                    See: ◄Qualified Type►
 
     register       Any segment or data register.
                                    -♦-