Okay, got that out of my system. Mice are trackballs upside down. Or is it the other way? Okay, mice.
Inside of a mouse there are two wheels that the mouseball rotates and another that holds the mouse ball against the first two. The two wheels spin axles on which flicker wheels (my own term) are mounted. When you push the mouse away the ball turns the vertical wheel. Side to side movement moves the other wheel. Each flicker wheel separates two Light Emitting Diodes from two light sensors. When the wheel spins, spokes in the flicker wheel pass between the LED's and their sensors. Holes, spokes and LED/sensor pairs are set so that one direction acts one way and the other direction acts another(don't ask me, I didn't work it out). In either direction, though, a count of flicker wheel spokes or holes is kept. This, the mouse tells the computer.
With direction and distance the computer can tell how far to move the pointer. The name of a single mouse-movement unit is called a mickey. Now, just add a few buttons to signal pressed/not pressed and you have described a mouse.
Connection to the computer can be either to a serial port or through a special expansion card. These expansion card mice are called bus mice. While very few users need them, a bus mouse has value in that it frees up one serial port to use with another device, typically a modem. Ensure that you buy the right mouse or trackball for your needs.
Updated January 24, 1998, 10:52pm. firstname.lastname@example.org