HP PCL/PJL reference - PCL 5 Comparison Guide

ENWW Print Environment 4-7
Note Table 4-3 lists the User Default Environment. This print environment
is stored in non-volatile RAM (NVRAM), which allows it to be retained
in the event of a power cycle (except for the HP LaserJet 4L, 5L, 6L,
and 1100 series printers, which do not contain NVRAM). In earlier
printers without PJL, the feature settings contained in the User
Default Environment were selectable through the control panel only.
In newer printers with PJL, these feature settings can be set from
either the control panel (if the printer has one) or through PJL or both.
The User Default Environment is reset to the Factory Default
Environment upon a cold reset.