Why does my mouse pointer disappear?

Why, in Windows, is the mouse pointer able to nearly disappear on the right and bottom sides of the screen, but unable to exit on the top or left?

• Answer:

  The top left of the mouse pointer is where the mouse coordinates (location) are read from. Imagine a tiny dot centered at the tip of the mouse pointer -- that is the only part that is relevant for any program that needs to read the mouse location. The rest is just for ease of visibility -- it would be very hard to locate a single, tiny dot on the screen if it didn't have a nice white pointing frame along with it. At the top left of the screen, that "tip point" would be exactly at the corner (this is usually marked as 0,0 in mouse coordinates). If you move your mouse to the right edge of the screen, the mouse pointer will only be able to move so far as to let the tip point rest on the screen's edge. Similarly, the bottom edge of the screen allows the tip point to rest on that edge -- everything else is hidden below it. You'll note that if you have a hyperlink pointer (the hand with a finger raised), then the tip of the finger becomes the mouse pointer location. If you move that to the edge of the screen, you'll note that the thumb protrudes into the screen and the rest of the "hand" is hidden. Try this by dragging a browser window off the right edge of the screen so that some hyperlink is cutting across the edge.