Pointing Device of computer

Pointing devices include mice, trackballs, and joysticks; touch screens; light pens; digitizing tables; and pen-based systems. One of the most natural of all human gestures, the act of pointing, is incorporated in several kinds of input devices. The most prominent ones are the following:

1.  Mice, trackballs, and joysticks 
2.  Touch screens 
3.  Light pens 
4.  Digitizing tablets

Mice, trackballs, and joysticks The principal pointing tools used with microcomputers are the mouse, the trackball, and the joystick, all of which have variations.

Mouse: 

a mouse is a device that is rolled about on a desktop to direct a pointer in the computer’s display screen. The pointer may sometimes be, but is not necessarily the same as, the cursor. The mouse pointer is the symbol that indicates the position of the mouse on the display screen. It may be an arrow, a rectangle, or even a representation of a person’s pointing finger the pointer may change to the shape of an I beam to indicate that it is a cursor indicating the place where text or other data may be entered. The mouse has a cable that is connected to the microcomputer’s system unit. This tail like cable and the rounded “head” of the instrument are what suggested the name mouse. On the bottom side of the mouse is a ball that translates the mouse movement into digital signals. On the top side are one, two, or three buttons. Depending on the software, these buttons are used for common or special functions, such as clicking and dragging. Gently holding the mouse with one hand, you can move it in all directions on the desktop. This will produce a corresponding movement of the mouse pointer on the screen. Depending on the software, many commands that can be done with a mouse can also be performed through the keyboard. The mouse may make it easy to learn the commands for, say, a word processing program. However you may soon find that you can execute those commands more quickly through a combination of keystrokes in the keyboard. 

Trackball: 

another form of pointing device, the trackball, is a variant on the mouse. A trackball is a movable ball, on top of a stationary device, that is rotated with the fingers or palm of the hand. In fact, the trackball looks like a mouse turned upside down. Instead of moving the mouse around on the desktop, you move the trackball with the tips of your fingers. Trackballs are especially suited to portable computers, which are often used in confined places, such as on airline tray tables. Trackballs may appear on the keyboard centered below the space bar, as on the apple power book, or built into the right side of the screen, on some portables the trackball is a separate device that is clipped to the side of the keyboard. 

Joystick: 

a joystick is a pointing device that consists of a vertical handle like a gearshift lever mounted on a base with one or two buttons. Named for the control mechanism that directs an airplane’s fore and aft and side to side movement, joysticks are used principally in video games and in some computer sided design systems. 

Touch screens

A touch screen is a video display screen that has been sensitized to receive input from the touch of a finger. The screen is covered with a plastic layer, behind which are invisible beams of infrared light. Because touch screen are easy to use, they can convey information quickly. They are used more often in automatic teller machines, in directories conveying tourist information in airports and hotels, and in fast food restaurants to display menus. Some applications are also available for microcomputers, although touch screens are of limited use because they cannot display large amounts of information.

 Light pen 

The light pen is a light sensitive stylus, pr pen like device, connected by a cable to the computer terminal. The used brings the pen to a desired point on the display screen and presses the pen button, which identifies that screen location to the computer. Light pens are used by engineers, graphic designers, and illustrators. 

Digitizing tablets 

A digitizing tablet consists of a tablet connected by a cable to a stylus or puck. A stylus is a pen like device with which the used “sketches” an image. A puck is a copying device with which the user copies, or traces, an image. When user with drawing and painting software, a digitizing tablet and stylus allow you to do shading and many other effects similar to those artists achieve with pencil, pen, or charcoal. Alternatively, when you use a puck, you trace a drawing laid on the tablet, and a digitized copy is stored in the computer, digitizing tablets are used primarily in design and engineering