Special Effects (Original enhancement)

SET DRAW MODE HIDDEN
Transfers to the mode of drawing only on the internal bitmap.

SET DRAW MODE EXPLICIT
Reflects the internal image, and transfers to the mode of drawing both on the screen and internal bitmap.

The following Statements designate how to mix the color at the point and the drawing color.
These statements do not affect the behavior of drawing of text except PLOT TEXT.
( Also do not affect the numerals drawn with DRAW GRID or DRAW AXES. )

SET DRAW MODE OVERWRITE
Paint the points with the color designated.

SET DRAW MODE MASK
Subtractive mixture

SET DRAW MODE MERGE
Additive mixture

SET DRAW MODE XOR
When figures are drawn twice, they shall vanish.
When the color at the point is black, the point shall be painted with the designated color.

SET DRAW MODE NOTXOR
When figures are drawn twice, they shall vanish.
When the color at the point is white, the point shall be painted with the designated color.