:                Segment-Override Operator                      MASM Operator

    segmentRegister:expression
 or
    segmentName:expression
 or
    groupName:expression

    This operator forces a label or variable's address to be computed
    using the beginning of a segmentRegister, segmentName, or groupName.

       Notes:     The segmentRegister must be CS, SS, ES, or DS.

                  SegmentName and groupName must have been defined using
                  the SEGMENT or GROUP directives. Also they must have
                  been assigned to a segment register with the ASSUME
                  directive.

                  The expression can be a relocatable operand or an
                  absolute symbol.

                  Depending on the instruction and operand types, the
                  effective address of an operand is computed relative to
                  ES, DS, and SS. By using this operator, these defaults
                  can be overridden.