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

EN Glossary-9
Parallel I/O
An input/output (I/O) interface that transmits more than one bit of
information simultaneously (in a “parallel” mode). Centronics is an
industry-wide parallel interface standard. (Also see Serial I/O.)
PCL Commands
PCL commands provide access to printer features. Once a PCL
command sets a parameter, that parameter remains set until the
same PCL command is repeated with a new value, or the printer
is reset. There are three types of PCL commands: control codes,
two-character escape sequences, and parameterized escape
sequences. (Also see escape sequences.)
PCL Coordination System Units
The units of the X-axis of the PCL coordinate system may be dots,
decipoints, or columns. The units of the Y-axis may be dots,
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 previously referred to as “PCL dots,” but should not
be confused with the printer’s physically printed dots.
Perforation Region
The perforation region is the distance from the bottom of the text
area to the top of the text of the next page. When perforation skip is
enabled, a Line Feed or Half-Line Feed, which would move the cursor
beyond the bottom of the text area, moves the cursor to the top of the
text area on the next page. When perforation skip is disabled, a Line
Feed or Half-Line Feed moves to the next line or half-line within the
perforation region.