Sinclair QL Beginner's Manual page 83

will give a red/green vertical striped strip. All the normal colour combinations are possible.
OVER
Normally printing occurs on the current paper colour. You can alter this by using strip. You can make
further effects by using:
OVER 1
OVER -1
To revert to normal printing on current strip use:
OVER 0
UNDER
You can underline characters.
UNDER 1
UNDER 0
SCALE GRAPHICS
If you wish to draw reasonably true geometric figures on a TV or video screen you cannot easily use a
pixel-based system. If you use scale graphics then the system will do the necessary work to ensure
that you can fairly easily draw reasonable circles, squares and other shapes.
The default scale of the graphics coordinate system is 100 in the vertical direction and whatever is
needed in the across direction to ensure that shapes drawn with the special graphics keywords
(PLOT, DRAW, CIRCLE) are true.
The graphics origin is not the same as the pixel origin which is used to define the position of
windows and blocks. The graphics origin is at the bottom left hand corner of the current screen or
window.
POINTS AND LINES
It is easy to draw points and lines using scale graphics. Using a vertical scale of 100 a point near the
centre of the window can be plotted with:
POINT 60,50
The point (60 units across and 50 units up) will be plotted in the current ink colour. Similarly a line
may be drawn with the statement:
LINE 60,50 TO 80,90
Further elements can be added. For example, the following will draw a square:
LINE 60,50 TO 70,50 TO 70,60 TO 60,60 TO 60,50
1 prints in ink on a transparent strip
-1 prints in ink over existing display on screen
underlines all subsequent output in the current ink
switches off underling.