HP PCL/PJL reference - Printer Job Language Technical Reference Manual

1-2 Introduction to PJL EN
Figure 1-1 PJL Resides Above Other Printer Languages
Note Some HP printers, such as the LaserJet 4L, 5L, 6L, or 1100 Series
printers, do not support printer language switching or job separation.
See Appendix A for feature support information.
Using PJL, software applications can request information such as
printer model, configuration, and status. PJL also can be used to
change control panel settings and modify the message displayed on
the control panel, or change feature settings in printers without a
control panel, such as the HP LaserJet 1100 Series printers. For
those printers supporting more than one printer language,
applications can print one job using PCL, and then print the next job
using PostScript or another printer language—without any operator
intervention.