:                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.

See also: SEGMENT
See also: GROUP
See also: ASSUME

: Segment-Override Operator