Computer Mouse

26 A computer mouse is also called a pointing device because it allows the cursor (usually an arrow or crosshairs) to be moved across the computer screen. You use your hand to control the direction and speed of the cursor. Many mouse-oriented programs allow you to select an option from a menu on the screen simply by pointing at it and clicking a button on the mouse. The mouse has become so popular because it obviates keyboard commands that distract the at- tention from the screen and are relatively slow and susceptible to errors. Another major application of the computer, draw- ing, would be unthinkable without a mouse. Principle of operation One aspect common to all computer mice is that movement is converted into signals that can be handled by a computer. This is achieved basically as shown in Fig. 1. An auxiliary spindle presses a small ball lightly against two spindles that are mounted at right angles to each other. Its own weight, and in some cases the auxil- iary spindle als...