The Computer Mouse

A personal computer that was purchased in the early 1980s probably included a keyboard as the only input device. Today, every new PC includes a pointing device as standard equipment, as shown in Fig. 1. Full-size PCs usually include a mouse as the pointing device. The pointer (also called the mouse pointer) is an on-screen object, usually an arrow, that is used to select text; access menus; and interact with programs, files, or data that appear on the screen. Fig. 2 shows an example of a pointer in a program window.

Types of computer mouse

Mechanical Mouse

The mechanical mouse is the most common type of pointing device. A mechanical mouse contains a small rubber ball that protrudes through a hole in the bottom of the mouse's case (see Fig. 3). The ball rolls inside the case when you move the mouse around on a flat surface. Inside the mouse, rollers and sensors send signals to the computer, telling it the distance, direction, and speed of the ball's motions. The computer uses this data to position the mouse pointer on the screen.

Optical Mouse

Another popular type of mouse, the optical mouse, is nonmechanical. This type of mouse emits a beam of light from its underside; it uses the light's reflection to judge the distance, direction, and speed of its travel (see Fig. 4).

Benefits of mouse over keyboard

The mouse offers two main benefits.

First

, the mouse lets you position the cursor anywhere on the screen quickly without using the cursor-movement keys. You simply move the pointer to the onscreen position you want and press the mouse button; the cursor appears at that location.

Second

, instead of forcing you to type or issue commands from the keyboard, the mouse and mouse-based operating systems let you choose commands from easy-to-use menus and dialog boxes (see Fig. 5). The result is a much more intuitive way to use computers. Instead of remembering obscure command names, users can figure out rather easily where commands and options are located. If you use a drawing program, you can use the mouse to create graphics such as lines, curves, and freehand shapes on the screen. The mouse has helped establish the computer as a versatile tool for graphic designers, starting what has since become a revolution in the graphic design field.