The application has control over clearing the display surface at any time by calling:
CALL GCLRWK(WKID, COFL)The integer COFL controls the way in which the update happens. If COFL is set to 'GALWAY' (see note at bottom of page 1), then the workstation is cleared even if there was no previous output. If COFL is set to 'GCONDI', then the drawing surface is cleared only if there has been previous output. Clearing the workstation deletes all WDSS segments stored on that workstation (segments are described in Chapter on Page
),
and on a hardcopy device the paper is advanced.
For metafile interpretation by the CERN utilities this
function is used to indicate 'end of picture'.
Note that the workstation is cleared automatically when it is opened. Some implementations also clear the workstation when it is closed, but this is not mandated in the standard.