A mouse is a small hand-held device that developed at the stanford research institute and used to place the screen cursor. it has two rollers (wheels) at the bottom which are perpendicular to each other and used to decide the amount and direction of the mouse movement. the two wheels connected to a shaft encoder which generates an electrical signals on each rotation of the wheel. the mouse movement encoded in x and y directions, when it moved other on a flat surface and stored in a separate registers.
An optical sensor is also used to decide its motion. for this, a special mouse pad consisting of a grid used, as the mouse moves the grid, its movements determined.
Variation of the standard mouse called as a Z-mouse developed which has three buttons, a trackball on the top, a thumb wheel on its side and a standard mouse ball at the bottom, hence providing six degrees of freedom. With the help of a Z-mouse, an object be picked, rotated and moved in any direction. this Z-mouse used in CAD animation and virtual reality system. To use the mouse the user does not necessarily pick it up. The x and y co?rdinate values will not change, when place of the mouse changes.