Mouse (computing)

Operating a mechanical mouse (Fig. 2). 

1: Moving the mouse turns the ball. 

2: X and Y rollers grip the ball and transfer movement. 

3: Optical encoding disks include light holes. 

4: Infrared LEDs shine through the disks. 

5: Sensors gather light pulses to convert to X and Y velocities. 

Fig. 2. The first computer mouse

A mouse is a handheld pointing device for computers, being a small object fitted with one or more buttons and shaped to sit naturally under the hand. The underside of the mouse houses a device that detects the mouse's motion relative to the flat surface on which it moves. The mouse's 2D motion is typically translated into the motion of a pointer on the display. 

It is called a mouse primarily because the cord on early models resembled the rodent's tail, and also because the motion of the pointer on the screen can be mouse-like (Fig. 2).