How do we erase text?
We are moving yellow text on a black background.
We can erase the text by drawing the same text over top of itself in black.
Listing 3 does that.
The call to the makecol function with parameters of 0,0,0 returns the RGB value for black.
Listing 3 causes black text to be drawn on a black background resulting in text that cannot be seen.
If there happens to be a line of yellow text there, it will be overwritten with black text.