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.