PSET and PRESET are used to set or reset an individual pixel at the specified coordinates.
Any number of points may be specified in one statement.
(x,y) are the coordinates of the pixel to be set or reset and must lie in the range 0<x<239 and 0<y<63. The coordinate (0,0) refers to the top left corner of the screen.
Will set the four corner pixels black.
PSET and PRESET are graphic statements and will default the screen to graphic mode. If when a PSET/PRESET statement is encountered the screen is in text mode, it will automatically change to graphic mode.
PSET sets pixels (turns them black)
PRESET resets pixels (turns them white)
Each time a pixel is set or reset using PSET and PRESET the graphic cursor is moved to that pixel.