I learned something very strange about the TI-83 while doing some assembly programming. Holding a combination of keys can register the same direct input value as another key. For example, pressing '8', '9', and 'x' (the multiplication button) at the same time sends the value of the up arrow button. '5', '6', and '-' is the right arrow; '2', '3', and '+' is the left arrow; '.', '(-)', and 'Enter' is the down arrow. I don't know if that also works with the TI-83 Basic language input, or if it works with any other combinations of keys. It doesn't seem like that was an accident, considering that the combinations of buttons for the arrow buttons are all adjacent like that. Just a strange random (possibly useful? probably not) fact.