Character Cell Model; Point Model; Point Model Has Precedence; Origin And Extent - Genicom GEK 00031B Programmer's Manual

Origin and Extent

Chapter 8. PPL3 Plus Emulation

Character Cell Model

The character cell model specifies the coordinates of a character cell
position as the line and character number, starting with character 1
of line 1. This is a simple model used for monospaced presentation.
The character cell model is not used for proportionally spaced
characters.
Character box: The size of the character as stored in the font. This
size cannot be varied by the host software.
Character cell: This is the distance from one character to another in
monospaced print mode. This distance can be varied by the host
software by changing the height of the current line spacing and the
width of the current character spacing. The host software can set the
size of the character cell to be larger than, equal to, or smaller than
the character box of the font being used. When the size of the
character box does not match the size of the character cell, the
character is left-justified within the cell.

Point Model

In the point model, the coordinates of a print position are specified in
decipoint units (exactly 1/720-inch), centipoint units (exactly
1/7200-inch), or printer-dependent pixels.
The point model is more complex than the character cell model. It
requires that a particular location in the character box be specified as
the origin of the character box. Subsequent point mode addressing is
relative to this origin. The origin, for placement purposes, is on the
baseline of the character at the left edge of the character box.
Point mode addressing is enabled by setting the Positioning Unit
Mode (PUM). Once enabled, the size of the points, or units, depends
on the current setting of the Select Size Unit (SSU). The size units are
decipoints or centipoints as described above.

Point Model Has Precedence

In PPL III, both models are supported. Whenever the Character Cell
model is used, coordinates are converted to point positions, where
the point is the intersection of the left edge of the character box and
the baseline.

Origin

The page coordinate system is an X-Y system in which the positive X
direction is to the right, and the positive Y direction is down. The
origin in this coordinate system is (1,1) and not (0,0).
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