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

EN Units of the PCL Coordinate System 2-5
Units of the PCL Coordinate System
The units of the X-axis of the PCL coordinate system may be PCL
Units, decipoints, or columns. The units of the Y-axis may be PCL
Units, decipoints, or rows.
PCL Units
These are user-definable units of measure which are used in PCL
commands affecting various PCL cursor moves. The number of
units-per-inch used in PCL cursor moves is determined by the current
setting of the Unit of Measure command (see “Unit of Measure
Command” in Chapter 4).
Note PCL Units were formerly referred to as “PCL Dots”. They were
renamed “PCL Units” to prevent confusion with the printer’s physically
printed “dots”, which are determined by the printer’s resolution.
Decipoints
In PCL terminology, a decipoint is 1/720 inch or one-tenth of a
PCL point (a PCL point is 1/72 inch as opposed to a typographic point
which is 1/72 inch).
Columns & Rows
The width of a column is defined by the current horizontal motion
index (HMI). The distance between rows is defined by the current
vertical motion index (VMI), or lines-per-inch (lpi). HMI, VMI and
lpi are described in Chapter 5, Page Control Commands.
Printer Internal Units
Internally, the printer uses a different unit of measure. It maps PCL
Units, decipoints, and columns and rows to this unit of measure. This
internal unit is 1/7200 inch. All positioning is kept in internal units and
rounded to physical dot positions when data is printed.