HP LaserJet 4100 HP PCL/PJL reference (PCL 5 Printer Language) - Technical Ref - Page 361

Note 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). 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. EN Glossary-9