Applications using a serial printer from a DOS Session must spool print data to the spooler through the appropriate LPT handles.

The physical device driver makes no attempt to restrict or mold the function of file system requests because they might have come from a DOS Session. To achieve the full capabilities of the file system access to COM, the application needs access to the full range of Category 01h IOCtls. The design and externals of the physical asynchronous device driver are based on the requirements of OS/2-mode applications that use the RS232-C port of the system.