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

Glossary-6 EN
Horizontal Motion Index (HMI)
HMI defines the distance between columns in 1/120 inch increments.
When fixed pitch fonts are selected, all printable characters including
the space and backspace characters are affected by HMI. When
proportional fonts are selected, the HMI affects only the space
character.
HMI is defaulted when font orientation, symbol set, pitch, spacing
or height is specified and when switching between primary and
secondary fonts with Shift In and Shift Out.
The default HMI is equal to the pitch value in the font header. The
factory default font’s HMI is 12 (which is 12/120 = 1/10 inch per
character or 10 characters per inch).
HP-GL/2
PCL 5 printers provide the ability to print vector graphics using the
HP-GL/2 graphics language commands. HP-GL/2 graphics may
be created within application software or imported from existing
applications. For various types of images (many technical drawings
and business graphics, for example), it is advantageous to use vector
graphics instead of raster graphics. Advantages include faster I/O
transfer of large images and smaller storage requirements. See
Chapter 17 for more information.
I/O
I/O is an acronym for input/output (I/O) and is used in this document
when referring to hardware used to interface printers with computers.
I/O Buffer
The area within the printer’s internal random access memory (RAM)
where PCL commands and data are stored.
Interface Connector
The LaserJet printer comes with two interface connectors, serial and
parallel, located on the lower part of the back panel. The cable that
attaches the computer to the printer is connected here. (Also see
Parallel I/O or Serial I/O.)