The HP printer language monitor filters RAW data as it is being sent from the printer driver to the port monitor, which sends the data to the port. The language monitor also controls aspects of the communication with a printer and implements a bidirectional communication method which allows status and configuration feedback from the printer to the printer driver and print queue and is called teh print spooler and is required to communcate with the HP printer.

hpzll43a.dll is loaded as dynamic link library that runs in the context of a process. This is typically installed with the program REALTEK GbE & FE Ethernet PCI-E NIC Driver published by Realtek Semiconductor Corp.. This particular version is usually found on Microsoft Windows XP (5.1.2600.196608).