A cursor is a small, movable marker that indicates the active position on the screen. The active position is the location at which the next character will be entered or some other activity will take place. Cursors are a crucial element of human-computer interfaces and play a key role in computer usability (i.e., the ease, comfort, efficiency and satisfaction with which a product can be used).
Mice, as the plural is usually written, are designed to sit comfortably under a hand. The underside of a mouse contains a device that detects the mouse's motion relative to the flat surface on which it is moved. The top is usually fitted with two or more buttons (but only one in the case of mice for Macintosh computers) and often with a small scroll wheel as well. The data from the movement of a mouse and its buttons is transmitted to the computer via a cable or infrared rays.
The mouse derives its name from the facts that the cord on early models resembled a rodent's tail and because the motion of the cursor on the screen can resemble that of a mouse. It was invented by Douglas Engelbart at Stanford Research Center (SRI) in Menlo Park, California in 1963 as part of his pioneering development of the GUI (graphical user interface). The original, bulky versions used two gear wheels attached perpendicular to each other, with the rotation of each translated into motion along one axis on the display screen.
Further refinement occurred at nearby Xerox PARC in the 1970s, where the external wheels were replaced with a single ball that could rotate in any direction. The ball's motion, in turn, was detected using perpendicular wheels housed inside the mouse's body. That mouse was used on the Alto, which incorporated a primitive GUI and was the first experimental desktop computer.
Mouse technology has continued to advance. An important area of progress has been optical mice, whose advocates claim that they are superior to mechanical mice with regard to performance, maintenance (none is needed) and longevity. Early optical mice detected movement using an optical sensor on their underside, paired with a light-emitting diode (LED) to illuminate the surface of the special metallic pad imprinted with a grid of fine blue and gray lines on which they moved. The need for a special mouse pad was eventually eliminated through the use of powerful, low cost image processing chips that enabled optical mice to detect relative motion on a wide variety of surfaces. Such mice acquire successive images of the surface, and changes between those images are translated into movement on the two axes. The main disadvantage of optical mice is a larger power consumption than for mechanical mice.
Another major convenience of many newer mice has been the addition of a scroll wheel between two main buttons that is designed for easy rotation by the index finger. This wheel makes it easier to perform operations such as moving up or down long documents. Moreover, when pressed, it performs the same functions as the middle button on three-button mice.
Alternatives for operating in GUIs have been developed that maintain all of the functionality (and utilize the same basic technology) as mice but which some users find more convenient. Among them are the track ball, which contains a ball that is moved with a hand, and the touch pad, which is a small, flat surface that senses movement of a finger on it. One of the advantages of these devices is a reduction in the space required for operation, thereby allowing them to be built directly into notebook computers.
The development of the mouse and other pointing devices has been one of the great breakthroughs in computer usability because it largely freed the user from using the keyboard and made possible the much more natural and intuitive pointing and clicking. This, in turn, has expanded the range of applications for computers, such as by allowing the mouse pointer to be used as a pencil, pen, brush, etc. for graphics programs.
Created July 1, 2006.