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KEYBOARD - On most computers, a keyboard is the primary text input device. (The mouse is also a primary input device but
lacks the ability to easily transmit textual information.) The keyboard also contains certain standard function keys, such
as the Escape key, tab and cursor movement keys, shift and control keys, and sometimes other manufacturer-customized keys.
The computer keyboard uses the same key arrangement as the mechanical and electronic typewriter keyboards that preceded
the computer. The standard arrangement of alphabetic keys is known as the Qwerty (pronounced KWEHR-tee) keyboard, its name
deriving from the arrangement of the five keys at the upper left of the three rows of alphabetic keys. This arrangement, invented
for one of the earliest mechanical typewriters, dates back to the 1870s. Another well-known key arrangement is the Dvorak
(pronounced duh-VOR-ak, not like the Czech composer) system, which was designed to be easier to learn and use. The Dvorak
keyboard was designed with the most common consonants on one side of the middle or home row and the vowels on the other side
so that typing tends to alternate key strokes back and forth between hands. Although the Dvorak keyboard has never been widely
used, it has adherents.
Because many keyboard users develop a cumulative trauma disorder, such as carpal tunnel syndrome, a number of ergonomic
keyboards have been developed. Approaches include keyboards contoured to alleviate stress and foot-driven pedals for certain
keys or keyboard functio
mouse
DEFINITION - A mouse is a small device that a computer user pushes across a desk surface in order to point to a place
on a display screen and to select one or more actions to take from that position. The mouse first became a widely-used computer
tool when Apple Computer made it a standard part of the Apple Macintosh. Today, the mouse is an integral part of the graphical
user interface (GUI) of any personal computer. The mouse apparently got its name by being about the same size and color as
a toy mouse.
A mouse consists of a metal or plastic housing or casing, a ball that sticks out of the bottom of the casing and is rolled
on a flat surface, one or more buttons on the top of the casing, and a cable that connects the mouse to the computer. As the
ball is moved over the surface in any direction, a sensor sends impulses to the computer that causes a mouse-responsive program
to reposition a visible indicator (called a cursor) on the display screen. The positioning is relative to some variable starting
place. Viewing the cursor's present position, the user readjusts the position by moving the mouse.
The most conventional kind of mouse has two buttons on top: the left one is used most frequently. In the Windows operating
systems, it lets the user click once to send a "Select" indication that provides the user with feedback that a particular
position has been selected for further action. The next click on a selected position or two quick clicks on it causes a particular
action to take place on the selected object. For example, in Windows operating systems, it causes a program associated with
that object to be started. The second button, on the right, usually provides some less-frequently needed capability. For example,
when viewing a Web page, you can click on an image to get a popup menu that, among other things, lets you save the image on
your hard disk. Some mouses have a third button for additional capabilities. Some mouse manufacturers also provide a version
for left-handed people.
Windows 95 and other operating systems let the user adjust the sensitivity of the mouse, including how fast it moves across
the screen, and the amount of time that must elapse within a "double click.". In some systems, the user can also
choose among several different cursor appearances. Some people use a mousepad to improve traction for the mouse ball.
Although the mouse has become a familiar part of the personal computer, its design continues to evolve and there continue
to be other approaches to pointing or positioning on a display. Notebook computers include built-in mouse devices that let
you control the cursor by rolling your finger over a built-in trackball. IBM's ScrollPoint mouse adds a small "stick"
between two mouse buttons that lets you scroll a Web page or other content up or down and right or left. Users of graphic
design and CAD applications can use a stylus and a specially-sensitive pad to draw as well as move the cursor. Other display
screen-positioning ideas include a video camera that tracks the user's eye movement and places the cursor accordingly.
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