This routine returns the status of a screen pixel at a given pair of X and Y co-ordinates.
Parameter block
| XY+ | Content |
|---|---|
| 0 | LSB of X coordinate |
| 1 | MSB of X coordinate |
| 2 | LSB of Y coordinate |
| 3 | MSB of Y coordinate |
| 4 | Logical colour at that point |
On exit, XY+4 contains the logical colour at the required point or &FF if the point specified was off the screen.