1. C o m p u t e r S y s t e m H a r d w a r e I N P U T P R O C E S S O U T P U T S T O R A G E

3. k e y b o a r d a keyboard is an input device , partially modeled after the typewriter keyboard , which uses an arrangement of buttons or keys , to act as mechanical levers or electronic switches. A keyboard typically has characters engraved or printed on the keys and each press of a key typically corresponds to a single written symbol . However, to produce some symbols requires pressing and holding several keys simultaneously or in sequence. While most keyboard keys produce letters , numbers or signs ( characters ), other keys or simultaneous key presses can produce actions or computer commands. In normal usage, the keyboard is used to type text and numbers into a word processor , text editor or other program. In a modern computer, the interpretation of keypresses is generally left to the software. A computer keyboard distinguishes each physical key from every other and reports all keypresses to the controlling software. Keyboards are also used for computer gaming, either with regular keyboards or by using keyboards with special gaming features, which can expedite frequently used keystroke combinations. A keyboard is also used to give commands to the operating system of a computer, such as Windows ' Control-Alt-Delete combination, which brings up a task window or shuts down the machine.

7. m i c r o p h o n e .Ü A microphone , colloquially called a mic or mike (both pronounced /ˈmaɪk/), is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal . Microphones are used in many applications such as telephones , tape recorders , hearing aids , motion picture production, live and recorded audio engineering , in radio and television broadcasting and in computers for recording voice, VoIP , and for non-acoustic purposes such as ultrasonic checking. A Neumann U87 condenser microphone The most common design today uses a thin membrane which vibrates in response to sound pressure. This movement is subsequently translated into an electrical signal. Most microphones in use today for audio use electromagnetic induction (dynamic microphone), capacitance change (condenser microphone, pictured right), piezoelectric generation, or light modulation to produce the signal from mechanical vibration.

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