CIGAL maintains several internal matrix variables that specify the dimensions of
various aspects of the cursor or display space. The names and meanings of the
different windows are described below. Each window can be displayed or modified
just as for any other matrix variable (for help see VARIABLES[1], TYPE[2],
ACCEPT[3], SYNTAX[1], ARITHMETIC[1]). Modifying a window automatically affects
the associated display function.
The window format is either:
(2x2) Xmin Ymin or (3x2) Xmin Ymin Zmin
Xmax Ymax Xmax Ymax Zmax

The different windows are:
^^0 The main text display window (2x2).
This window defines the region of the screen used for the active
text display. The units are in character positions and default to
the full display screen. Command lines are displayed in this
window; output is displayed here as well if ^^1 has not been set.
Text is confined within the window and scrolls off the top.
^^1 The secondary text display window (2x2).
This window defines the region of the screen used for the
displaying command output and help messages. The units are in
character positions; the default setting has Ymax less than Ymin,
which indicates that ^^1 is not set. When set, text is confined
within the window and scrolls off the top.
^^2 The screen window (2x2).
This window defines the active portion of the display screen. The
screen window is normally the dimensions of the current display
screen on the computer terminal. If the CURSOR flag MAPOUTPUT is
set, then the logical values returned by the cursor are mapped to
these display values, scaling such that the logical minimum and
maximum fill the display window.
^^3 The image processor display window (2x2).
If an image processor is present, this window sets the limits on
the active part of the display. Its usage will be somewhat
dependent on the hardware available.
^^4 The vector drawing window (3x2).
Lines or points that extend beyond the prescribed (3-D) window
will be truncated at the boundaries.
^^5 The physical cursor window (2x2).
Sets the maximum and minimum values allowable for cursor X and Y
values.
^^6 The logical cursor window (2x2).
If the CURSOR flag MAPINPUT is set, then the physical values
returned by the cursor are mapped to these logical values, scaling
so that the physical minimum and maximum fill the logical window.
^^7 The cursor drawing region (2x2).
This is the region within which special cursors, such as a cross-
hair or box cursor, are active. Outside of this region the cursor
reverts to the standard cursor (usually an arrow).