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keyboard is basically a board of keys. Along with the mouse,
the keyboard is one of the primary input devices used with a computer. The
keyboard's design comes from the original typewriter keyboards, which arranged
letters and numbers in a way that prevented the type-bars from getting jammed
when typing quickly. This keyboard layout is known as the QWERTY design, which gets
its name from the first six letters across in the upper-left-hand corner of the
keyboard. | |
mouse is one of the primary input devices used with
today's computers. The name comes from the small shape of the mouse, which you
can move quickly back and forth on the mouse pad, and the cord, which
represents the mouse's tail. Of course, if you are using a wireless mouse, the
analogy does not work so well. All mice have at least one button, though
most mice have two or three. Some also have additional buttons on the sides,
which can be assigned to different commands. Most mice also have a
scroll-wheel, which lets you scroll up and down documents and Web pages by just
rolling the wheel with your index finger. Early mice tracked movement using a ball in
the bottom of the mouse. This "mouse ball" pushed against different
rollers as it moved, measuring the mouse's speed and direction. However, now
most mice use optical technology, which uses a beam of light to track the
mouse's motion. Optical mice are more accurate than roller-based mice and they
have the added bonus of not getting dirty inside. | |
Speakers are one of the most common output devices used with
computer systems. Some speakers are designed to work specifically with
computers, while others can be hooked up to any type of sound system.
Regardless of their design, the purpose of speakers is to produce audio output that can be heard
by the listener. Speakers are transducers that convert
electromagnetic waves into sound waves. The speakers receive audio input from a device such
as a computer or an audio receiver. This input may be either in analog or digital form. Analog
speakers simply amplify the analog electromagnetic waves into sound waves.
Since sound waves are produced in analog form, digital speakers must first
convert the digital input to an analog signal, then generate the sound waves. |