The order of play

Every time a primitive creates a meaningful file with a particular suffix, it sends a display request to the display system. For example, suppose the primitive that performs dark subtraction creates a frame called f19990330_00042_dk.sdf and then asks the display system to display it. The display system consults the disp.dat file for a dk entry. If no such entry is found, the display request is ignored and nothing happens. If one or more entries are found the display system proceeds to honour the request. If the disp.dat entry specifies a particular tool and/or window, the display system checks to see if they exist already and if not, stars them. Then it displays the data with the appropriate parameters.