Input Device: Mouse

In computing, a mouse is a pointing device that functions by detecting two-dimensional motion relative to its supporting surface. Physically, a mouse consists of an object held under one of the user's hands, with one or more buttons. It sometimes features other elements, such as "wheels", which allow the user to perform various system-dependent operations, or extra buttons or features that can add more control or dimensional input. The mouse's motion typically translates into the motion of a cursor on a display, which allows for fine control of a graphical user interface.

1. Mechanical mouse : It is a hand held pointing device. A mechanical mouse has a rotating ball on its base. It is rolled over a flat surface or on a mouse pad. The cursor on the screen moves in the direction of mouse's movement. Two rotating wheels placed at right angles to each other inside the mouse detect the direction of movement. Each wheel is connected to a shaft encoder,which limits electrical pulses for every incremental movement of wheel. The pulse transmitted by the mouse determines the distance moved.

There may be two or three buttons on a mouse. The button on the left is for selecting items on the screen and the button on the right is normally used for displaying and selecting pop-up menus. 

2. Optical Mouse : The optical mouse has a light beam instead of a rotating ball to direct movement across a specially-patterned mouse pad. the optical mouse use LEDs and photo detectors to trap its movements. Optical mice make use of one or more light-emitting diodes (LEDs) and an imaging array of photodiodes to detect movement relative to the underlying surface, rather than internal moving parts as does a mechanical mouse. A Laser mouse is an optical mouse that uses coherent (Laser) light.

3. Inertial and gyroscopic mouse : Often called "air mice" since they do not require a surface to operate, inertial mice use a tuning fork or other accelerometer to detect rotary movement for every axis supported. The most common models (manufactured by Logitech and Gyration) work using 2 degrees of rotational freedom and are insensitive to spatial translation. The user requires only small wrist rotations to move the cursor, reducing user fatigue or "gorilla arm". Usually cordless, they often have a switch to deactivate the movement circuitry between use, allowing the user freedom of movement without affecting the cursor position.

4. 3D mouse : Also known as bats, flying mice, or wands, these devices generally function through ultrasound and provide at least three degrees of freedom. Probably the best known example would be 3DConnexion/Logitech's SpaceMouse from the early 1990s.

In the late 1990s Kantek introduced the 3D RingMouse. This wireless mouse was worn on a ring around a finger, which enabled the thumb to access three buttons. The mouse was tracked in three dimensions by a base station. Despite a certain appeal, it was finally discontinued because it did not provide sufficient resolution.