ASSUME           Associate Segment with Segment Register       MASM Directive

  ASSUME  segmentRegister:segmentName,,,
or
  ASSUME  NOTHING

Specifies the segment register (segmentRegister) that will be used to
calculate the effective addresses for all labels and variables defined
under a given segment or group name (segmentName).

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

The segmentName argument must be a segment name
previously defined with the SEGMENT directive, a group
name defined with the GROUP directive, or the keyword
NOTHING.  If the keyword NOTHING is used, the previous
segment selection is canceled.

ASSUME NOTHING cancels the segment selections for all
four segment registers.

Usage of the segment-override operator (:) will override
the segment register specified in the ASSUME directive.

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

ASSUME Associate Segment with Segment Register