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PENERA or PE
All following DRAW, DRAWTO, DOCAP and PLOT commands will cause any
pixels the CAP passes through to be erased.
PENRET or PR
This allows the CAP to return to the co-ordinates that existed before
the last DRAW, DRAWTO or PLOT commands.
To draw, erase or invert a line based on co-ordinates specified in
To draw, erase or invert a line based on relative co-ordinates.
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To adjust for the height to width ratio of the screen when using PLOT
or CIRCLE. The argument passed with the RATIO command will be used to modify
the Y axis co-ordinates.
To draw, erase or invert a line based on co-ordinates given in polar
The new CAP co-ordinates are calculated, based on a specified angle
“A” and distance “D”. “A” is an angle between 0 and 359 degrees, which is
calculated clockwise, zero degrees being towards the top of the screen. This
value can be exceeded as a wrap around effect takes place, 360 degrees being
the same as 0 degrees, 450 degrees being the same as 90 degrees etc. “D” is a
distance specifying the number of pixels. This distance is modified
automatically by a value dependant on the argument given in a previous RATIO
command and also the value of the angle A. As the argument given in the RATIO
command only modifies calculations in the Y axis, there will be no
modification to the length of lines plotted at angles 90 and 270 degrees,
however as the angle nears the vertical (0 or 180 degrees) the modification
will be at it’s greatest. The old CAP co-ordinates are saved in case of a
following PENRET command.
To draw a circle or are on the screen.