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

EN Printed Dots 2-3
Printed Dots
The high quality output achieved by HP LaserJet printers is due in
part to the ability to lay down a fine grid of “dots” on the page. The
density of this grid is referred to as the printer’s resolution. From
the first HP LaserJet (the “LaserJet Classic”) until recently, all
HP LaserJet family printers printed at a resolution of 300
dots-per-inch. In a one inch square, the printer could print a dot
anywhere in a grid of up to 300 dots horizontally by 300 dots
vertically, for a total of 90,000 possible dot locations per square inch
(300 × 300 = 90,000).
The LaserJet 4 printer is capable of printing at either 300 or 600 dpi
resolution. At 600 dots-per-inch, it becomes possible to print up to
360,000 dots per square inch (600 x 600 = 360,000). Print resolution
of LaserJet 4 is selectable and can be specified either from the
printer’s control panel or programmed through PJL commands.
Figure 2-1 300 vs 600 DPI Dot Sizes
Note Refer to Appendix E of the PCL 5 Comparison Guide or the printer
User’s Manual to determine the default print resolution for a specific
HP LaserJet printer.
The printer’s physical dot size has no direct bearing on the size of
“PCL Units” used in cursor movements. PCL Units were previously
referred to as “PCL dots”, but should not be confused with the
printer’s physically printed dots. The size of PCL Units can also
be specified (see the Unit of Measure Command in Chapter 4 for
more information).