This application selects the first, i.e. oldest, FRAME picture in the graphics database  for a graphics device, subject to the following criterion. The picture must not obstruct any other picture except the BASE, and must itself not be obstructed. Unobstructed means that there is no younger picture overlying it either wholly or in part. This means that plotting can occur within the selected FRAME picture without overwriting or obscuring earlier plots.

DEVICE = DEVICE (Read)

picentire

This selects the first unobscured and unobscuring FRAME picture for the current graphics device.

picentire xwindows

This selects the first unobscured and unobscuring FRAME picture for the xwindows graphics device.

• An error is returned if there is no suitable FRAME picture, and the current picture remains unchanged.

• This routine cannot know whether or a picture has been cleared, and hence is safe to reuse, as such information is not stored in the graphics database.

KAPPA: PICEMPTY, PICGRID, PICLAST, PICLIST, PICSEL, PICVIS.

The execution time is approximately proportional to a linear combination of the number of pictures in the database before the unobstructed FRAME picture is found, and the square of the number of pictures in the database.