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

EN Glossary-7
Unsolicited Status
Unsolicited status (USTATUS) is printer status information sent as a
result of certain printer events occurring, such as when the printer
runs out of paper, a job finishes printing, or when a certain time
period elapses. There are several types of unsolicited status
(DEVICE, JOB, PAGE, and TIMED); unsolicited status must be
enabled with the USTATUS command.
User Default
A user default is a default value that is selectable by way of the
operator control panel or the PJL DEFAULT command.
User Default Environment
The User Default Environment consists of the user default settings
selected from the control panel or by way of the PJL DEFAULT
command. The user default settings are stored in non-volatile
memory (in those printers that have NVRAM). Those settings not
selected using the control panel or PJL DEFAULT command are set
to the factory default values.