HP PCL 5 Reference Manual page 189

Note
Use the Font ID command to designate a unique ID number prior to
the download of a font header. If an existing font is already associated
with this ID, the existing font is deleted upon the download of the font
header. Unless otherwise specified, inappropriate values in a font
header field invalidates the font download process; a font is not
created and the associated font data is discarded.
Intellifont scalable font formatting also requires the Intellifont Scalable
Typeface Format document, which supplements the information
provided here. For information on how to obtain this document, refer
to "Related Documents" in the front of this manual.
The figures that follow illustrate the font header formats for the various
font classifications. The individual fields for the font headers are
described following the figures.
Notes Although some LaserJet printer models do not use all of the data in
the font header and thus ignore many of the fields, a font creator
should use valid values in all of the font header fields. This ensures
font compatibility across the LaserJet printer family and with future
printers, which may use these fields.
Those font header fields identified as "reserved" should be set to
zero.
Table 11-2
Byte
EN
Format 0 Font Header (for PCL Bitmapped Fonts)
15 (MSB)
0 Font Descriptor Size (64)
2 Header Format (0)
4 Style MSB
6 Baseline Position
8 Cell Width
10 Cell Height
12 Orientation
14 Symbol Set
8 7
Font Type
Reserved
Spacing
Font Header Format 11-7
(LSB) 0