Track Ball A trackball is a device which consists of a ball housed in a socket containing sensors to detect rotation of the ball about two axes i.e. An upside-down mouse with an exposed protruding ball. The ball is rolled by the user with the help of thumb, fingers, or the palm of the hand in order to move a cursor. For easy precision tracker balls are common on CAD workstations. Before the invention of the touchpad, trackballs were common on portable computers, where there were no desk space on which a mouse could be run. Some small thumb balls clip on the side of the keyboard and have also integral buttons with the same function as mouse buttons have. Mouse A mouse is a device that a computer user moves across a desk surface in order to point to a place on a display screen and to select one or more than one actions to take from that position. It consists of a metal or plastic casing. A ball, which sticks out of the bottom of the casing, is rolled on a flat surface. It has one or more buttons on the top of the casing. It is consists of a cable that connects the mouse with the computer. When the ball is moved over the surface in any direction, a sensor sends directions to the computer that causes a mouse responsive program to reposition a visible indicator which is called a cursor on the display screen. This positioning is comparative to some variable starting place. While viewing the cursor's present position, the user readjusts the position of cursor by moving the mouse on the plain surface.
