OFFSET           Offset of Expression                           MASM Operator

OFFSET expression

Returns the number of bytes between the expression and the beginning
of the segment it is defined in.

Notes:     Expression can be a label, segment name, variable, or
other symbol.

In order to generate valid offsets when accessing
variables in groups or segments, use the segment-
override operator (':') to force OFFSET to calculate the
offset relative to the start of the group or segment.

See also: SIZE

OFFSET Offset of Expression