The DO statement allows one to carry out manipulations
on 
, 
, 
, and various other
arrays. It can also
be used to define a weighting scheme. All
operations are carried out for the selected reflections.
The selection is accomplished by the xrefin FWINdow
and RESOlution statements. The
GENErate, EXPAnd, and REDUce statements
can be used to complement data, expand the data to 
, or
reduce the data to an asymmetric unit. For a brief description
of the latter three statements, see Section 12.3.