HP PCL/PJL reference (PCL 5 Printer Language) - Technical Reference Manual Part II

EN CP, Character Plot 23-25
z Lines — Specifies the number of lines the pen moves relative to
the current pen location. Positive values specify the number of
lines the pen moves up from the current pen position; negative
values specify the number of lines the pen moves down (a value
of –1 is equivalent to a Line Feed). Up and down are relative to
the current label direction. The Line Feed distance is uniquely
defined for each font; use the Extra Space (ES) command to
adjust the height.
When you move the pen up or down a specific number of lines, the
Carriage Return point shifts up or down accordingly.
The illustration below shows the interaction of label direction and the
sign (+/–) of the parameters.
Figure 23-12Interaction of Label Direction and Parameter Sign