3.3 Horizontal Master Units

The Xdpi box contains the value that specifies the horizontal master unit.
This value is the least-common multiple of the selected horizontal
cursor-movement command and the supported graphics resolutions.

In the example for the Diconix printer, the horizontal master unit is 960
dots-per-inch (dpi). This value is the least-common multiple of the
following graphics and cursor-movement resolutions:

o   80-dpi (normal/expanded-mode graphics)

o   160-dpi (normal/expanded-mode graphics)

o   320-dpi (normal/expanded-mode graphics)

o   12-cpi (default font-character width)

A minidriver typically supports three graphics resolutions: low, medium,
and high. In the case of the Diconix, there are four horizontal graphics
resolutions: 80, 96, 160, and 320. Because the 96-dpi resolution does not
factor evenly into any of the others, this resolution has not been used.
The remaining three values (80, 160, and 320) are used to support
horizontal graphics resolutions. In the case of the HP LaserJet IIP
printer, each of the supported graphics resolutions (75, 150, and 300)
factor evenly into the specified least-common multiple of 300.

Many dot-matrix and laser printers support commands that move the cursor
(or print head) horizontally across the page; however, some dot-matrix
printers do not. In this case, the Universal Printer Driver uses the space
character from the narrowest printer font to move the cursor (or print
head) horizontally across the page. (For more information about the
horizontal cursor-movement command, see Chapter 4, Specifying Control
Information.) Because Diconix printer falls into the latter category, the
space character from the narrowest printer font (a 12 pitch font) is
selected as the horizontal space command. This means that the resolution of
the horizontal cursor-movement command for the Diconix printer is 1/12th of
an inch.


Diconix 150 Plus

The Xdpi box contains the value 960. This value specifies the least-common
multiple of the selected graphics and horizontal-movement resolutions.


HP LaserJet IIP

The Xdpi box contains the value 300. This value specifies the least-common
multiple of the selected horizontal resolutions.